_SORTING, GRADING, AND PACKING_
The question of standardising the output of our plantations is one which
has occupied attention for some years, with a not inconsiderable degree of
success.
Meanwhile opinion is growing in favour of proceeding along the line of
reducing the number of plantation grades to a minimum. At present some
confusion exists. Some estates make up tree-scrap and bark-shavings
together; one estate puts tree-scrap, earth-scrap, and bark-shavings into
one uniform crepe; other estates have three or more separate scrap
grades--_e.g._, lump-rubber and "washings," tree-scrap, earth-scrap, and
bark-shavings scrap. There is a movement on foot at present to try to
restrict plantation rubber to three grades:
CREPES--1. _First Quality Latex._--_I.e._, crepe made from the true
coagulum obtained from the regulated coagulation of strained latex. This is
a pale rubber, and may be prepared satisfactorily if the directions given
in preceding chapters are followed. Naturally there must be, in all
factories, some defective rubber of this grade. For various reasons the
crepe may be of inferior colour, or is slightly contaminated with dirt or
traces of oil and grease, etc. This defective rubber should be placed aside
most rigorously and plainly marked as "off-quality."
If a proper scheme of standardisation of latex and chemicals is followed,
there should not be any such variety in shades of colour, such as was
common in No. 1 crepe in the past.
Comparatively few estates in Malaya now prepare thick (or blanket) crepes
in the No. 1 grade, but in such cases the same rules must be applied as
govern the sorting of thin fine pale crepes.
2. _Compound Crepe, No. 1._--In this it is proposed to include
cup-coagulated lumps, coagulated lumps from transport vessels, skimmings,
bucket rinsings, cup-washings, and tree-scrap. It has been shown in Chapter
X. that strict care is necessary to eliminate all oxidised (dark) scraps.
These are relegated to a lower grade. The possession of a "scrap-washer" is
necessary if the best results are to be obtained.
On some estates the ingredients of this compound crepe, while fresh, are
placed in a common jar or tank to which a quantity of sodium bisulphite (1
per cent. solution) and acid are added. The resulting conglomerate mass is
cut up for working.
3. _Compound Crepe, No. 2._--This grade would include the remaining lower
grades--viz., bark-shavings, scrap, and earth-rubber scrap.
REDUCTION CARRIED TOO FAR.--However desirable it may be to diminish the
number of grades, it must be pointed out that diminution and simplification
are not necessarily synonymous terms in this matter. It is well known that
on estates where the earth-rubber is only brought in at lengthy intervals,
say of a week, the resulting crepe is sometimes very tacky. This is only
natural, and is due to the prolonged exposure to the sun's rays. With the
improved machinery now at our disposal, and with the increasing attention
which will be given to the lower grades in the future, it is possible to
prepare from average bark-shavings crepe free from bark, and of quite a
good colour. Where trees are not "scrapped" before tapping, there would
seem to be no objection to amalgamating the rubber obtained from the
bark-shavings with the No. 1 Compound crepe; and it would be a distinct
danger and possible loss if this good rubber were to be mixed with earth
rubber. The liability of the latter to become tacky is well recognised; and
if possible it should be maintained as a separate grade, in which it would
be permissible to mix only rubber obtained from actually dry shavings from
"scrapped" trees, or heavily-oxidised scraps which have been rejected from
other grades.
SHEETS.--Broadly there are no fine distinctions to be made at present in
the grading of smoked-sheet rubber; it is either No. 1, or if any
so-called defect is visible the sheets must be rejected and plainly marked
as "off-quality."
Clippings (trimmings) may either be made into crepe or shipped under their
own description.
RUBBER GROWERS' ASSOCIATION'S RECOMMENDATIONS.--Taking the foregoing
arguments into full consideration, it would seem that, strictly speaking,
the number of grades cannot be reduced to less than four at present without
producing some amount of confusion.
In its handbook,[15] the Rubber Growers' Association remarks:
[15] "Preparation of Plantation Rubber," 1917.
"The fewer grades the better, and regularity of each grade is most
important.
"The grading should be as follows:
"(No. 1) Fine crepe (or No. 1 sheet), made from the free or
liquid latex.
"(No. 2) Clean light brown crepe, made from lumps and skimmings.
"(No. 3) Scrap crepe, made from tree-scrap.
"(No. 4) Dark crepe, made from bark-shavings, earth rubber, and
the lower quality of scrap.
"Tacky rubber should be packed separately.
"_Compound Scrap Crepe._--Estates using scrap-washers should make a
compound crepe of grades Nos. 2 and 3, which will make one compound free
from bark and specks. All rubber intended for No. 4 should be most
thoroughly washed."
Concerning these recommendations the remarks in preceding paragraphs should
be studied.
CARE IN SORTING.--Whether dealing with smoked-sheet, pale crepe, or lower
grades, the strictest care is necessary in sorting and grading. This work
must of necessity be relegated to coolies, and they should be trained men.
Instructions must be definite, and doubtful specimens of rubber should
always be placed aside for the decision of the European superintendent. Any
pieces showing unmistakable signs of what are regarded as defects should be
stringently rejected. In the case of pale crepe, when the defect is
confined only to a small area it is permissible to cut out the affected
portion. Similarly there can be no objection, in the case of smoked sheets,
to an occasional sheet being treated in this manner. On the majority of
estates these rules are observed carefully, but some estates yet have to
learn that defective pieces of rubber may not be concealed in a bulk of
otherwise good quality. Samplers have often an uncanny knack of hitting
upon the defective specimens, and it is entirely the fault of the estate's
sorters if these pieces are submitted as being representative of the mass.
CHOICE OF CASES.--Consumers complain justly of the presence of chips,
splinters, and wood-dust. It will be evident, therefore, that whatever the
type of case employed the interior surfaces should be smooth, there should
be no cracks or gaps in the timber, and the cases should be cleaned out
before using. There remains great room for improvement in the means and
method of packing, and in spite of suggested alternatives we are at present
restricted to the use of wooden cases.
From comparisons of actual quality and fulfilment of the requirements
indicated above, there can be no question that cases made of three-ply
wood, such as the "Venesta," are in every respect superior to the ordinary
wooden cases of "Momi" type. The consideration of cost and available
supplies, of course, enters largely into the question, and three-ply cases
are not at present so largely employed as they deserve to be.
A new type of case was recently exhibited in Singapore. It emanates from
the U.S.A. and is made of a fibrous material, resembling in appearance a
very stout cardboard. The complete case when assembled consists really of
two boxes, one of which is inverted and slides down over the other. Packing
is completed by means of stout wire, which is strained by a simple ratchet
arrangement. It is claimed that from 225 to 250 lbs. of rubber can be
contained. Other claims made amount to the statement that the case is
practically indestructible under normal conditions of handling and
shipping. A demonstration given certainly appeared to substantiate the
statement fully. Rubber packed in cases of various and average type was
allowed to fall from a height of about twenty feet. In all instances the
wooden cases of every type were either smashed or badly burst, whereas the
fibre cases were merely dented. These cases are obtained in flat sections,
which, in assembling, are folded and clamped by means of copper rivets in
a special but simple machine. It was pointed out that objection might be
lodged against the use of copper for this purpose.
More recently there is announced a new packing case which is stated to be
made from low-grade rubbers, but information is rather vague.
BAGS.--There are in local use stout canvas bags which have the advantage of
being used many times, as long as they are waterproof and kept in good dry
condition. Their employment for the conveyance of smoked-sheets would
appear to be permitted, but crepe rubbers sent in them are often reported
upon as being "massed" at the edges, and hence difficult to "sample."
BALES.--Attempts to bale rubber for the market have been frequent, but no
success seems to have attended the efforts. In some quarters the failure
has been ascribed to prejudice on the part of buyers, but it is the opinion
of the writers that the objections to baling are, or could be,
well-founded. Massed rubber often cannot be inspected properly, and hence
is always open to suspicion that internally there may be unsuitable
portions.
There have been several schemes put forward for winding crepe rubber on
spindles so as to form a cylindrical package complete in itself. We have
seen the process, and certainly the method had much which appeared
commendable. Apart from other objections which might be raised, there is
always the one prominent objection mentioned in the preceding paragraph.
While baling of rubber is thus not likely to suit the general market, there
is no reason why, as in one or two instances, it should not be practised by
agreement between producer and consumer. It is believed that "slab" rubber
is shipped in bales from Sumatra to the U.S.A.
Quite recently a proposal has been put forward to revert to a simple form
of baling for ordinary plantation rubber. Under this scheme wooden cases
are discarded, the packing material being composed of scrap-grade crepe
rubber which, it is claimed, could be put to use by the manufacturer. An
obvious drawback would be evident if these bales happened to be exposed to
direct sunlight or a continuous high temperature. The tackiness which might
supervene would make the handling of such bales unpleasant, even if it did
not affect the internal rubber.
FOLDING FOR PACKING.--In the packing of smoked sheets it would appear to be
advisable to avoid, if possible, the folding of any pieces, as the
objection is made that such rubber is difficult to "sample" on arrival,
especially in cold weather. Sheets should be prepared or cut to such length
that they occupy the full superficial area of the box, either singly or
side by side.
[Illustration: A SHIPMENT OF RUBBER, PACKED AND READY FOR TRANSPORT.]
The same remark applies to the packing of crepe rubbers, except that here
we deal with units of folded rubber. Crepes are generally folded by hand,
and coolies usually work to a certain dimension by means of a standard
stick. The work is slow, but often gives employment, at a cheap rate of
pay, to women and weak coolies.
Several machines have been invented to replace this labour. The best of
these yet seen has a simple device by means of which the length of the fold
is adjustable to suit the size of any packing case. It is called the
"Senang" folder, and is made by the General Engineering Company (Radcliffe)
Ltd., Radcliffe, near Manchester.
CARE IN ASSEMBLING.--Whatever the type of case employed, great care must be
given to the assembling of parts and the final fastening. It is not
uncommon to find in the operation of putting on the "strapping" that nails
have been driven into the rubber. Extra bands of strapping are sometimes
advised, and where these bands pass over the sides (not edges) of the case
only specially short nails should be used.
All wood should be planed, and in cases other than three-ply should be of
stout wood, not less than 5/8 inch in thickness. All timber used should be
of uniform type and thickness.
METHODS OF PACKING.--The usual method of packing crepe is to fold the
lengths to some measure of the dimensions of the case. This is done in a
haphazard fashion on some estates, with the result that either space is
lost or the packing is badly arranged.
Some ingenuity can be displayed in the packing of sheet rubber in order to
avoid folding the sheets, which, besides increasing the difficulty of
sampling, leads to loss of space. Endeavours are being continually made on
estates to prepare sheet of such a size as to obtain the maximum benefit of
space both in smoke-house accommodation and in packing. A few estates
employ tanks of such calculated dimensions as will yield uniform sheets
which pack flat and fill the superficial area of the case.
In view of the contamination which sometimes characterises the employment
of wooden cases it is sometimes advised that the interior should be lined
with sheets, or pieces of crepe, the ends of which are later folded over
the top of the mass. In this manner it is stated that contamination is
confined only to the exterior of the contents of the case.
WEIGHT OF CONTENTS.--The dimensions of average cases are 19 inches by 19
inches by 24 inches, giving a capacity of 5 cubic feet.
In these it is possible to pack 150 lbs. of crepe rubber and 200 lbs. of
sheet rubber (about 5 per cent. more in cases of three-ply wood). It may
be noted that boxes arrive in better condition when fully packed. The
foregoing figures are not adhered to strictly. For example, some estates
find it expedient to ship rubber in actual ton lots, and for this purpose
pack only 140 lbs. of crepe per case, giving sixteen cases to the ton.
Other estates, using presses, pack more per case than the quantities noted
above. At present there does not appear to be any definite regularity in
practice.
[Illustration: ON ITS ROAD TO THE RAILWAY: BULLOCK-CART TRANSPORT.]
In all instances it should be the invariable rule that the rubber should be
weighed before packing, and that all cases should contain uniform nett
quantities of any particular type of rubber. Invoicing, etc., will thus be
greatly facilitated. If these practices are followed, and the rubber always
weighed on the same scales (assuming it to be perfectly dry when packed)
complaints of "short-weight" should be infrequent.
"SHORT" WEIGHTS.--In some cases the occurrence of "short" weights on
arrival at ports would appear to be inexplicable. It often happens that the
constituent parts of wooden cases have been in stock for a considerable
period. If for no other reason than that indicated below, all cases,
either before or after assembling, should be thoroughly dried in the sun.
"Short" weight could be accounted for to some degree by a lack of
observance of this elementary rule, as it is most probable that there would
be a perceptible difference in weight of the wooden case in a drier
atmosphere.
(_a_) If rubber is weighed in the box, and the average tare of the
case deducted from the gross weight (in order to obtain the nett
weight), any loss in the weight of the timber would appear as a
deficiency of rubber at the distant port.
(_b_) Whether the same effect would be produced eventually in the case
of rubber which is weighed before packing will depend upon the method
of weighing at the warehouse. If the rubber is weighed in the box, any
observed deficiency would be attributed to a loss of weight in the
rubber.
PART III
MACHINERY AND BUILDINGS
CHAPTER XIII
_MACHINES_
The number of manufacturers of machines for preparing rubber would seem to
be on the increase, and there can be little doubt that this competition
will result in a continued improvement in the design of machines. It cannot
be denied that there has been room for such improvement, and it is believed
that manufacturers will display judgment in putting only their best quality
into the work. While design and finish are very excellent in their way, it
is to be regretted that in a number of cases in the past the material of
rolls has been found to be of inferior quality. Generally, the complaint
seemed to be that the rolls were too soft, and that the "grinding" effect
was far too great. The damage to pale rubber in such cases is considerable,
as it is impossible to keep the rolls free from fine dark powder. The
effect is generally noticed more in the smooth rolls with which a finish is
put upon the crepe.
Cases have occurred frequently in which rolls have been returned, because
of the injury caused to pale rubber, and there can be little doubt that the
life of quite a large number of rolls is even now far too short in
comparison with the expense involved.
It is a moot point, however, in many instances how far the quality of the
rolls is actually responsible for the damage done to the rubber. In the
experience of the writers it is certain that complaints regarding the rolls
were unjustifiable, and that the injury had been caused by carelessness in
the "feeding" of the machine. Especially in the case of smooth finishing
rolls, it is clear that if the rolls are allowed to run idle for more than
the briefest possible interval grinding must take place.
The complaints apply not only to the rolls themselves, but also to the
brass linings for shaft-bearings. Cases are known in which a brass "liner"
was so worn within a few weeks as to be quite useless. If the matter ended
there it would not be so bad; but there is always the possibility of
particles of brass finding their way into trays, and so into the rubber.
The damage which ensues to the rubber is quite irreparable. This particular
defect arising from the presence of brass will be dealt with in a later
chapter. But here again it is necessary to point out that such wear on
brass liners may be caused by the standards (ends) of the rolls being
eccentric; and the case may be analogous to the placing of "new wine in old
bottles."
_En passant_ it may be remarked that in any case brass liners are not
strictly necessary. White-metal alloys are in use on rubber machines, and
cast-iron bearings have been employed satisfactorily for years.
It would be well for managers to remember, therefore, that when machines
have to be ordered, nothing but the best is good enough, and that the
difference between good machinery and passable machinery is probably
immensely greater in effect than any saving in expenditure would warrant.
ADEQUACY OF MACHINES.--In general, the factories which prepare sheet rubber
are usually equipped with adequate machinery. This arises from the fact
that machines are necessary for preparing all grades below the first, even
if they are not necessary for the making of sheet. Thus all the necessary
macerators and finishing machines are installed, but the major part of the
output is in sheet form. For the preparation of sheet, no heavy machinery
is required; all that is necessary are light machines for rolling the
sheets and expressing as much moisture as possible. To obtain a pattern on
the sheet, another light machine may be used. It may be imagined, then,
that the work of rolling sheet rubber by power machines is small, and that
a large quantity of rubber can be worked off in a comparatively short time.
It follows, therefore, that the preparation of the lower crepe grades can
be proceeded with at once, and that the whole work of the factory is
expedited.
The case of factories which have to prepare all first-grade rubber in crepe
form is quite different, especially when thin rubber has to be made. The
care which has to be exercised in preparing pale crepe rubber is very great
in comparison with what is demanded by sheet rubber. The rubber has to go
first through the uneven-speed macerators, from there to the intermediate
rollers, thence to the finishing rollers. Considerable ingenuity has to be
displayed in the arrangement of the machines, so that one section will not
work faster or slower than another. More often than not, the attempt to
arrive at such a desirable arrangement fails, owing to an insufficiency of
machines. Such a statement will probably read strangely to the uninitiated;
but an example will make it plain. A factory may have a battery of six
machines, one only of which is a finishing machine (smooth rolls). With
five macerators and intermediate machines working continuously, it will be
more than the work of one finishing pair of rolls to keep pace, especially
as so much more care has to be exercised in finishing than in rough
crepe-making. The obvious course to adopt is to substitute a pair of smooth
rolls, with suitable gear ratio, for a pair of macerators or
"intermediates."
If, however, the macerators and intermediates are already fully occupied
the whole of the time, any such change would be of small benefit. What is
really needed in this case is more machinery.
It might be pertinently asked what constitutes an adequate equipment of
machines for crepe-making. The writers cannot give a number, but have no
hesitation in stating that if a factory cannot complete its whole day's
work before dark, it is inadequately equipped. No work should be done after
dark, if possible, as it cannot receive the supervision which crepe-making
demands. To make comparison between the number of machines in any two
factories and their respective outputs is not sound argument, as the
out-turn of two similar machines will depend upon the speed at which the
rolls travel--_i.e._, the gearing between the machines and the engines.
Thus, while one machine will out-turn 40 lbs. of crepe per hour, another
may only have an output of 30 lbs., although the machines may be identical
in pattern. To make calculations based on a rate per hour for any known
make of machine, and to apply those calculations to the existing machinery
in any factory, in an attempt to judge whether there is a sufficient number
of machines, would be a mistake, unless one were also supplied with the
relative speeds at which the rolls work.
Finally, on the question of adequacy of machines, it must be pointed out
that an insufficient number of machines must result in a poor product,
since all rolls have to be used for all grades. Even with the greatest
possible care it happens that pale crepe is sometimes spoiled because it is
contaminated with foreign matter, resulting from the working of lower
grades on the same machines. This is one of the great arguments in another
direction for the installation of a scrap-washer.
In conclusion, the writers can only give their opinion that one must not
decide the question of adequacy by the number of existing machines, but by
the time taken each day in working off the rubber, providing one can be
satisfied that the best arrangement of the existing machines has been made.
IDEAL ARRANGEMENT.--As to what this best arrangement may be, guidance can
be obtained from the results of experience here given. It must be premised
that the output of any factory preparing fine pale crepe is limited by the
output of the smooth finishing rolls. Broadly, it will be recognised that
if there is any excess of capacity in a battery it should be found in the
smooth-roll machines. This sufficiency, or excess of capacity, may
sometimes be attained by an alteration in the gearing of the drive of the
rolls from the back-shaft, or by an addition to the number of machines. In
the former case, there are practicable limits of speed, beyond which the
second alternative measure must be adopted.
SPEED.--The usual speed at which the back-shaft travels ranges from 60 to
70 revolutions per minute. Taking first the macerating machines, the
intermediate gearing between the shaft and the rolls should give a driving
speed of about 20 revolutions per minute on the faster-travelling roll.
This is equivalent, with a 15-inch diameter roll, to a peripheral speed of
about 60 to 65 feet per minute.
The intermediate and smooth rolls can be arranged to travel more quickly,
but the maximum comfortable speed for proper feeding and control appears to
be about 25 revolutions per minute on even-speed rolls. In view of the fact
that the rubber at each successive machine becomes longer and thinner, it
will be seen that a smooth-roll machine could not cope with the output of a
macerator in the same period of time. If, therefore, the macerator is fully
occupied for the greater part of the time, an additional smooth-roll
machine must be installed, even though the existing one has been "speeded
up" to practicable limits.
For the information of the uninitiated it might be explained that in the
macerating and intermediate machines the cog-wheels driving the two rolls
are of different sizes (_i.e._, differentially geared), as opposed to the
smooth rolls on which the cog-wheels are usually of the same size (_i.e._,
even speed). The idea in the one case is to exert a "working" influence
upon the rubber while it is being washed by the stream of water coming from
above; in the smooth rolls a squeezing action only is effected.
To give an idea of the ratio of the speeds of the rolls in each machine in
a typical working battery, the following particulars may be noted:
GEAR RATIOS.--
_Machine._ _Differential Ratio._
1. Macerator 32-17
2. Intermediate (coarse grooved) 32-17
3. " (fine grooved) 30-19
4. Smooth (uneven speed) 30-19
5. " (finishing) 25-24
6. " ( " ) 25-24
It will be seen that the so-called "even-speed" smooth rolls run at
approximately the same rate.
It is advised that in all cases the gear wheels should be cut helically.
Those who have experience of the noise of some batteries after they are
slightly worn will appreciate such a remark.
GROOVING OF ROLLS.--Concerning the choice of grooving, there is divergence
of opinion, some managers preferring one type, which others reject in
favour of another type. Provided any particular type can be shown to be as
effective as required, no necessity for laying down hard-and-fast rules
seems to exist.
The following particulars serve to describe a battery well known to the
writers, and accustomed to produce the finest quality of thin pale crepe
and lower grades:
-----------------+-----------------------------------+-------------
| |_No. of Times
_Machine._ | _Grooving._ |Rubber passes
| | through._
-----------------+-----------------------------------+-------------
1. Macerator | Deep horizontal grooves; |
| square-cut, 5/16 inch x 5/16 inch |
| x 5/8 inch spaces | 3
2. Intermediate | Horizontal grooves; 3/16 inch |
| x 3/16 inch x 3/8 inch spaces | 2
3. " | Fine spiral grooves; 1/8 inch |
| x 1/8 inch x 1/4 inch spaces | 2
4. Geared smooth | Nil | 1
5. "Even" smooth | " | 1
6. " " | " | 1
-----------------+-----------------------------------+-------------
| Total | 10 times
-----------------+-----------------------------------+-------------
The actual rate of output of this installation is the capacity of the last
smooth machine. This is about 180 lbs. per hour, while the output of the
macerator is approximately double this amount. Thus the macerator only
works for about half the time. This applies also to the two intermediate
machines. After a study of the preliminary remarks, it would not be
difficult to suggest methods for improving the condition of affairs. It
would appear that, in order to obtain a uniform rate of working in such a
battery, the relative peripheral speeds of the several machines should
be--(1), (2), and (3) 100; (4) 150; (5) and (6) 200. The remarks on the
practical limits of speed should be borne in mind. In this case the smooth
rolls travelled at 23 revolutions per minute.
As already stated, it is not intended to lay down definitely that, _e.g._,
horizontal grooving alone should be cut on macerating rolls. Some estates
employ with satisfaction a deep square-cut spiral 1/4 inch by 1/4 inch by
1/4 inch or 1/2 inch spacing; others use a large diamond pattern. Similarly
various types of grooving are cut in the intermediate rolls.
[Illustration: A BATTERY OF MACHINES.
On the left, light marking rolls for sheet rubber; on the right, heavy
machines for crepe preparation. In the middle background, "scrap-washing"
machines outside the main building.]
It has been remarked in the chapter dealing with crepe preparation that
much depends upon the condition of the coagulum. There is no necessity, or
desirability, for having a standard higher than 2 lbs. dry rubber per
gallon, and it has been argued that it would be better to select a standard
of 1-1/2 lbs. The tougher the coagulum, the more the power required, and
the slower the rate of output of the leading machines.
In ordering machines for crepe-making, only large rolls should be
considered--_e.g._, rolls having a diameter of 12 inches to 18 inches and
from 15 inches to 18 inches face.
ROLLS RUNNING HOT OR "FREE."--If the rolls are found to become hot, work on
that machine should be stopped, and an examination made, otherwise there
is the possibility of the crepe becoming sticky and "tacky" when dry.
Although comparatively cold water may be flowing upon the rubber and the
rolls, little alleviation may be noticed, inasmuch as the source of heat
lies generally at the bearing ends of the rolls. This may be tested by
placing the hand on the top of the "standard" of the machine. The
development of the heat may be due to lack of lubrication, worn bearings,
or sometimes faulty setting-up of the machines.
Allusion has been made to the necessity for avoiding the running "free" of
rolls--_i.e._, in the absence of rubber. The grinding of the rolls, when
working close together, produces a fine powder, which causes a more or less
pronounced deposit on pale crepe. When the rolls have been in action for
some time and become slightly worn, this deposit may be confined only to
the edges of the rubber.
SHEETING MACHINES.--The foregoing paragraphs have dealt entirely with
machines for crepe preparation. Concerning machines for use in
sheet-making, the ground has been mainly covered in Chapter IX.
Where both crepe and sheet are made, it is permissible and advantageous to
use the heavy smooth rolls for the rolling of the sheets, and it is only
necessary to instal one or two light machines for placing a pattern on the
rubber.
Where a heavy battery does not exist, light machines with smooth rolls may
be employed satisfactorily. Even engine-power is not necessary for the
preparation of excellent sheets, but the output is limited where hand-power
only is employed. Estates are known on which upwards of 1,000 lbs of sheet
rubber are made daily with hand-power machinery in one station. Beyond this
figure, it is deemed advisable to instal a small engine, say of 7-9
horse-power. This is ample to drive a battery of three smooth-roll machines
and two markers, and yet have sufficient reserve to actuate a small pump
for the water supply.
LUBRICATION OF MACHINES.--It must always appear to those inexperienced in
engineering matters that existing methods for lubricating rubber machinery
are distinctly crude, when one considers the delicacy of the material to
be prepared. Many existing machines are still lubricated with oil, which
has to be administered in generous quantities. Generally, such machines
have been so designed that the excess of oil may find an easy passage into
the tray which receives the rubber. If not, it drops just outside the tray
to the floor, and is washed away in great gouts. Even where grease-cap
lubricators are fitted it is common to find that the excess can often be
transferred from the bearings to the trays and so to the rubber. One would
have expected from the attention which is being given to machinery for
rubber estates that some improvement in lubrication methods would have been
devised.
It is probable, however, that a great deal of the disabilities attaching to
present methods of lubrication might be obviated if closer attention were
given to the actual operation of the lubricators. Coolies should not be
allowed to handle them, and the responsibility should be placed upon a
foreman or the engine-driver.
TRAYS.--The most unsuitable and damage-causing part of the vast majority of
machines, without doubt, is the tray. On nearly all machines the tray is
wider than the effective portion of the rolls, so that any excess of
lubricant may drop into it. On others, not only is the tray wider than the
rolls, but its edge either is in contact with the shaft of a roll or just a
small distance away. The edge of the tray is thus favourably situated for
acting as a "wipe," and the lubricant is transferred to the inside of the
tray. Considering that the effective portion of rolls is about two-thirds
of their length, it must be unnecessary to have trays wider than the length
of the rolls. For the preparation of fine crepe trays are quite
superfluous, and their place can be taken by a narrow piece of board if
required. If the bed of the machines has been covered with glazed tiles,
even a piece of board is not necessary. Where trays have been removed from
the fine-crepe rolls on a number of estates, a marked decrease in the
number of spoiled pieces of rubber has resulted.
It must be recorded that the foregoing paragraph appeared in our 1913
publication. After a lapse of over seven years, the remarks remain as true
as when originally written. One of us is continually meeting with cases in
which the defects are plainly attributable to the cause indicated above,
and the fault often lies with the management of estates. On most machines
the trays are not fixtures, and could be removed if desired.
ARRANGEMENT OF MACHINES.--In considering the future arrangement of
machines, the first care should be to see that machines and windows are to
be found together.[16] Of all the factory operations, rolling of rubber
should be given the maximum light. At the same time it would not be
advisable always to choose a southern aspect, unless outside shades were
supplied. The best position for setting up machines, therefore, is along a
wall having a number of windows. This is extremely convenient also from the
view of power transmission, and gives the maximum free floor space to the
factory. In setting up machines, foresight must be displayed, otherwise one
may find, when future extensions are made, that the extra machines may
obstruct an entry or exit.
[16] Windows imply the existence of walls. Such is the conventional design
of factories. It may be pointed out that walls are not necessary. The roof
may be supported on pillars between which expanded metal of large size may
be placed. This fulfils all requirements and gives the maximum of light and
air. Many new factories have been erected to such a design.
For the actual erection of machines, no labour should be accepted without
European supervision. At present there are machines which are practically
useless owing to faulty workmanship, and on many machines bearings run hot
for no apparent or explicable reason. Whether the fault lies with the
turning of the rolls or the setting of the machine cannot be decided; but
at any rate too much care cannot be expended on the supervision of setting
up machines.
There is no reason why everything in a factory should not be made as easy
to clean as possible. For this desirable condition all machines should have
the beds faced with tiles. A word of caution should be given against using
marble slabs under the machines, as they would be eroded in time by the
slight amount of acid washed out of the rubber. There would be no such
objection against the use of white glazed tiles, if they are well set.
ACCESS TO BACK OF MACHINE.--In a few factories it has been noticed that the
drainage of water from the machines runs to the front of them. This means
that the coolies are put to unnecessary inconvenience and discomfort, and
they often suffer from sore feet. All water should drain to the back of the
machines. The necessity for seeing that these drains are kept clear might
then induce those in charge to examine the back of the machines. It is
often the case that, while the front of the rolls and tray are kept clean,
little attempt is made to cleanse those parts which are not visible or
accessible from the front. There should be no need to point out that any
labour expended in such "front-window" work is rendered useless by the
contamination from accumulations of old rubber and grease at the back of
the machines. In the course of visiting factories one of us has many times
seen great surprise exhibited by the manager or assistants on being shown
the state of affairs at the back of the machines. There should have been no
occasion for such surprise, for the back of the machines is quite as
accessible to them as to the visitor.
In conclusion it might be said that the manager needing advice as to the
best machines cannot go far wrong in purchasing any of the better-known
makes, such as Shaw's, Bridge's, Robinson's, Bertram's, Walker's, Carter's,
Iddon's, etc. This list does not include local manufacturers such as the
"United Engineers." It must not be imagined that their machines are not
recommended. As a matter of fact, their machines compare well with those
made at Home. It would be well to judge in the final decision upon--
1. Cost.
2. The experience of those already using the machines.
3. Simplicity of parts.
4. Lubrication system.
5. Mode of adjusting rolls.
6. Fitting of trays.
ENGINES.--It is not intended here to discuss particular makes of engines,
or even to attempt to lay down definite statements with regard to the type
of engine. Without a full knowledge of local circumstances, it is not
possible to recommend whether the engine shall be oil-driven, gas-driven,
or steam-driven.
Assuming a copious supply of very cheap timber, there could be no objection
to the employment of a steam-engine; but for most estates such a choice is
out of the question.
Again, in deciding between oil and gas, local economic factors must be
considered. Suction-gas plants are now made, in which a wonderful variety
of refuse can be consumed in the production of gas, whereas ordinarily
estates are restricted to the use of either charcoal or anthracite coal.
Both oil and gas driven engines are eminently suitable for the purpose of a
rubber factory, and the results obtained on different estates with either
are often discussed in favour of one or the other. The selection ultimately
narrows itself down to one of cost of running, in which availability of
supplies becomes an essential feature.
POWER.--No matter what type is selected, there should be made an ample
allowance for margin of power. The general experience of estates has been
that when the first portion of the estate comes into bearing, there is a
desire to avoid great outlay, which should really have been secured in the
original capital. The result has been that as later the estate expands, the
original power unit is found to be inadequate, and a larger engine has to
be purchased. In a short while the original engine is found to be
unsuitable even as a "stand-by," inasmuch as it is incapable of doing more
than a portion of the work required. This means eventually that another
large engine is required. Had sufficient margin of power been allowed
originally, only two engines would have been bought, as against the three
indicated above. Without going into finer details, it is usual to allow a
rate of 10 horse-power per heavy machine used for crepe preparation. In
actual practice, when a battery is working under full load, the power
demanded is about 6 horse-power per machine. Thus a 50 horse-power engine
running six machines and a scrap-washer is really running with only a small
margin of power, and if large pieces of hard coagulum are placed in the
washer or the macerator there may be a sudden stoppage. Assuming an average
estate commences with only three machines for crepe-making, on an expanding
programme, allowance of power should be made for six machines and a
scrap-washer, if the purchase of larger power units is to be avoided
later.
CHAPTER XIV
_FACTORIES_
GENERAL CONSTRUCTION.--On the question of general construction there is
little to be said, except that buildings are now being properly designed in
more permanent form than were some of the earlier buildings. On the whole
there is little fault to be found with factories in general, except in so
far as the output has outgrown the accommodation.
Most factories are now erected in iron, but there are a few which are built
of bricks. It should be premised that a factory in which rubber is to be
prepared should be as light and airy as possible. In this respect quite a
number of the older factories are lacking, and they seem to have been
designed to exclude as much air and light as possible. Under these
circumstances, the building is always dark, there is always an air of
dampness, dirt may accumulate, and there is usually a bad smell. Rubber
prepared under these conditions is always liable to be below the high
standard which should be attained, and the general tone of the factory is
depressing.
PLENTY OF LIGHT.--The old idea that light must be excluded is now known to
be erroneous; so that in designing a factory, provision should be made for
ample light and air. It should not be forgotten that in tropical climates,
iron buildings may become uncomfortably hot, as most of our older factories
are. Usually it will be found that the ventilation is imperfect. There is a
lack of window space, and the roof is imperfectly ventilated. The ridge of
the roof should be opened up by means of a "jack-roof," so that the warm
air rising naturally may escape at the highest point of the building. These
are defects which should be remedied in old buildings.
As a rule no rubber remains in the factory at night-time, except in the
form of coagulum, the loss of any of which would be noted with ease. The
conventional idea of enclosing the factory with walls of galvanised
sheeting, wood, or brick, is not strictly necessary. In modern buildings
these walls are replaced by large-mesh expanded metal, thus making the
machine-room perfectly light and plentifully ventilated. Under such
conditions, dirt cannot accumulate unseen, and the general tone of the work
is raised.
THE FLOOR.--The floor should be of thick concrete, and have a good surface
layer of cement. Preparations are now advertised for which claims are made
that their employment renders the surface of such floors waterproof and
dustproof. If these claims can be substantiated when the use is applied to
the floors of rubber factories, the employment of a preparation of this
nature should result in a considerable saving of expense and trouble.
Preferably the floor should not be flat, but should slope slightly from the
longitudinal middle of the building to the sides on either hand. If the
floor is level it usually results in accumulation of water, the cement
breaks in patches, and the factory always appears to be dirty.
POSITION OF MACHINES.--All machines should be arranged adjacent to and
parallel with one of the long sides of the building, and should be raised
about 6 inches above the floor, so that water may escape easily. Tanks for
the reception of latex, scrap rubber, etc., should be placed along the
opposite wall to the machines, and the intermediate length of the building
should be entirely free from fixtures. It was not uncommon in older
factories to find the engine situated in the middle of the floor, so that
what with the space occupied by the engine, and the space rendered
unavailable by the belt-drive, the real accommodation of the factory was
sadly diminished. In no modern factory should the engines be brought into
the main room. They should always be accommodated in a special compartment,
situated outside the wall, along the inside of which machines are placed.
In this way considerable floor space is left available, and the machines
may be worked by direct drive. Not only so; but if a suction-gas plant is
worked, there can then be no excuse for particles of coal or charcoal dust
being found in the factory.
POSITION OF ENGINES.--It scarcely need be pointed out that if the engines
are placed outside the wall which is opposite the machines, a long
belt-drive would be necessitated, and that the presence of the belt would
prevent the use of end doors. It is presumed in these arguments that two
engines are to be installed. One can hardly imagine a modern factory in
full working being equipped with only one engine, which might possibly have
an excess of power necessary to drive all the machines. In the case of
breakdown, which sometimes happens in the best supervised factories, it
would be small consolation to know that this excess of power was present
theoretically.
HOW MANY STOREYS.--There can be no doubt that, taking all things into
consideration, the best type of factory is that consisting only of one
floor. The factory should be quite separate from all other buildings, and
if attempts are made to conserve ground space by putting a drying-room over
the factory, much trouble will ensue, especially if pale crepes are to be
made. In the first place, the factory is made very much darker, and hence
more difficult to keep clean; secondly, the ventilation of the factory is
seriously interfered with; and thirdly, it is manifestly prejudicing the
drying of rubber to place it directly over a room which is always more or
less awash with water. At night such a building would reek with a
moisture-laden atmosphere, and little drying could be expected to take
place in that interval. From actual experience it has been shown that
rubber hung to dry in such a room, situated over a damp factory, is very
liable to attacks of "spot" diseases, since the presence of perpetual
moisture is favourable to the development of these diseases. If a
double-storey building has to be worked, it will be readily seen that no
first-grade rubber should be allowed to dry in it. The accommodation over
the factory may be restricted to the purpose of receiving lower grade
rubber which is not so liable to "spot" diseases, and possibly does not
take so long to dry as first-grade rubbers of equal thickness. It is
evident, therefore, that the erection of double-storey factories is false
economy, as separate drying-houses have to be built eventually. This
conclusion does not apply with the same force to factories worked in
conjunction with smoke-houses for preparing sheet rubber, but,
nevertheless, such a factory should not have another floor above the
work-room.
VERANDAHS.--One of the worst features in many factories is the necessity
for coolies to bring latex into the factory. As already mentioned, the
floors of factories are usually running with water (or should be), and it
can be imagined that the passage to and fro of scores of coolies must bring
in a great quantity of dirt. Not only so; the very presence of the coolies
is a hindrance to the efficient working of the factory, and considerable
floor-space and time are wasted.
This feature in factory working is all the more annoying because the
necessity for it could so easily be obviated. All that is necessary is the
erection of a wide, open verandah outside the wall of the factory. Here all
latex could be received and strained, scrap-rubbers could be received and
passed through an opening into tanks placed in convenient position. Water
could be laid on in this verandah so that coolies might wash their buckets,
and the whole verandah might be enclosed only with expanded metal so as to
avoid interference with the lighting of the factory. In this way it would
be quite unnecessary for any field coolie to enter the factory proper, and
this would facilitate cleanliness. Such an arrangement has been discussed
by the writers many times during the last few years, but the number of
estates which have made such provision is still in the minority, and the
same slipshod and dirt-making procession of coolies continues to walk
through the factories, and the same piles of bark-shavings and scrap-rubber
continue to accumulate and ferment in a few instances.
An indication of types of verandahs is given in Chapters VII. and IX. These
are not intended to be representative of a universal design, but may be
suggestive in the planning of others according to local conditions.
SITUATION OF TANKS.--It will be noted that these verandahs are raised from
the ground-level to a height of about 3 feet in order that latex may be
gravitated, with a slight fall, into the coagulating tanks which are within
the factory. There exists a real necessity for this practice, inasmuch as
otherwise to obtain gravitation of latex (which is quicker and cheaper
than handling) the coagulating tanks would have to be either placed on the
floor or sunk beneath the level. The risk of contamination of latex or
coagulum under such circumstances would be appreciable. Apart from this, it
is advisable to have the coagulating tanks raised to a height of between 2
and 3 feet, to secure the advantage of ease of working in the processes of
coagulation and the handling of coagulum--a not inconsiderable factor.
In some modern designs it is proposed to place the coagulating tanks in a
separate building. This would seem to be an unnecessary refinement in a new
building, if observance is given to the suggestions made in previous
paragraphs.
DESIGNS AND "LAY-OUT."--In a previous publication[17] comment was made upon
grievous errors in designs prepared by those inexperienced in the
requirements of the tropics. There is little ground now for complaint, and
local engineering firms are fully capable of advising upon, and
constructing, suitable buildings.
[17] "Preparation of Plantation Rubber," Morgan, 1913.
In considering the first installation of a factory and equipment one always
has to weigh the question of prime cost against the probability of future
expansion of crop. If it should be decided at first merely to cater for
contemporary requirements, the fullest consideration should be given in
discussing design of building and lay-out of machinery to the
practicability of later extension. The site should be large enough for the
eventual group of buildings, the building should be easily capable of
extension with the least cost, and the same forethought should govern the
lay-out of the machinery.
DRAINS.--Lastly, there is the question of drains. Generally speaking, all
factories are well provided with drains, and the only difficulty is that of
getting an adequate fall for efficient drainage. But there is a certain
amount of laxity exhibited in the matter of providing sieves in drains. To
anyone acquainted with factory working, it must be apparent that quite a
lot of small pieces of rubber are washed into the drains. This rubber
should be collected at intervals during the day; but in many instances
that collected is only a fraction of what escapes. Wherever possible the
drainings of a factory should be carried as far as is practicable from the
buildings by means of cement drains. Too often these are short, and lead
into earthen drains. Even if no pieces of rubber are present, the serum
from the coagulum is subject to decomposition, the effluvium from which is
objectionable.
WATER SUPPLY.--It is essential that a good supply of water should be
available. This should be distributed by pipes all round the building, so
that a hose may be used in every part for the thorough cleansing of the
factory at intervals during the hours of working.
Summing up, it might be said that a good factory, therefore, should have
the following features:
1. Plenty of windows, or walls of expanded metal.
2. A jack-roof in the ridge, and hence a good system of ventilation.
3. Engines in compartments outside the walls of the factory.
4. Machines close to and parallel with the wall outside of which the
engines are placed.
5. Latex tanks and other fixtures along the wall opposite the
machines.
6. A long middle free space, at either end of which a large double
door should be placed in the end walls.
7. A good concrete and cement floor sloping slightly from the middle
towards each long wall.
8. An abundant water supply, and several lengths of hose.
9. The building should be of only one floor, and have ample head room.
10. There should be an outside, open verandah upon which latex may be
received, etc.; preferably outside the wall which is opposite to the
machines.
11. The system of drainage should be thorough, and the drains should
be adequately screened, so that all particles of rubber may be
collected.
CHAPTER XV
_OTHER BUILDINGS_
DRYING-HOUSES FOR CREPE.--It has already been shown in the previous chapter
that one type of drying-houses--viz., that over a factory--stands
condemned, except for the drying of low-grade rubbers. Generally speaking,
a great advance has been made in the design of crepe drying-houses during
recent years, and it has been possible even to improve older ones so as to
bring them into line with the more modern buildings. Houses for drying
crepe rubber may be of one floor, two floors, or even three floors.
Doubtless those built with three floors were designed with a view to
economising the available site for factory buildings, and as long as the
ventilation is good there can be no very great objection to them. It might
be pointed out, however, that even with the best of ventilation the air
passing successively through three layers of rubber must be fairly
saturated with moisture by the time it leaves the building. The effect of
this upon the rate of drying in the uppermost chamber will not be so marked
as it will be in the middle floor, as the temperature of the top floor must
be many degrees higher than that of the other two rooms. It would be
expected, therefore, that the rate of drying in the middle storey would be
slower than that in either of the other two.
In houses of two floors this objection would not have to be met, and
drying-houses of this type are successful and common.
HOW MANY STOREYS?--Again nothing could be urged against a building of two
or three storeys in which the ground floor was occupied as a packing-room,
except that, by negligence in not allowing wet crepe a preliminary dripping
period, water might fall upon the packed rubber below.
As a matter of experience, such a house is, taking all into consideration,
the cheapest and most suitable type for any estate with an increase in
output. Even at the outset there should be a separate room in which sorting
and packing is undertaken. This is conveniently the lower room of a
drying-house. The only stipulation to be made for a house with two storeys
is that the floor of the upper room should be of an open pattern, so that
the air may circulate right through the building. This is usually and very
successfully attained by laying down wide slats of wood, with spaces of an
inch or more between them. It is not advisable to have spaces wider than
1-1/2 inches, otherwise there is a certain amount of danger to the limbs of
individuals who have to work or supervise in the building. In any case, it
is very convenient to have pathways of planks running the whole length of
the floor, so that the supervision is made more convenient. If this is
done, there can be no objection to the custom of suspending the rubber of a
lower chamber from the slats of the floor of the upper room. At present, in
some drying-houses, this means of suspension is used, but no planks are
laid down, and it becomes necessary to walk over the drying rubber. This is
a detail, but it is one which does not make for the improvement of rubber,
and the expenditure of a small sum would be sufficient to rectify the
matter.
From every point of view, it would be desirable to have the floor of the
packing-shed (or the packing-room in a combined house) raised from the
ground, to a height of, say, 3 feet; or the height of a bullock-cart or
motor-lorry. Not only is ventilation improved, but there would be a great
saving in labour. Packed cases could be wheeled directly on a level with
the cart or lorry.
A great many estates favour drying-houses of one storey. These are
eminently suitable, provided that the site is suitable, and that the
relative dimensions of the house are favourable to efficient ventilation.
It is a common mistake to find buildings of which the breadth is out of
proportion to the height. Obviously, if the height is not considerably in
excess of the breadth, ventilation will be defective. For a single-storey
drying-house, the maximum height should bear the ratio to the breadth of
3:2, and in a house of this type specially long pieces of crepe can be
utilised. Naturally, in a house of two storeys, this factor is not likely
to be neglected, and if the lower room is used for packing purposes the
rate of drying should be rapid. Again, when a single-storey building is
contemplated, it is well to make strict examination of local conditions. If
the site is low-lying and surrounded by trees it will be clear that tall
buildings are required, and that a house of more than one floor is to be
preferred. Considerations of this nature would have prevented the erection
of some dry-sheds which do not give a satisfactory rate of drying.
VENTILATION.--No matter how many floors there may be in a drying-house, the
greatest attention should be given to the question of ventilation. It is an
elementary point in the study of ventilation problems that the best system
of natural ventilation is obtained by admitting cool air near or through
the floor and providing an exit for the warmer air at the highest point in
the building. It is not often that such a rule is infringed in the
ventilation of rubber drying-houses, but several of the older buildings
erred in this respect. In a good modern house there is a space (about 2
feet in height) all round the base of the walls merely closed with expanded
metal; this admits cool air. An exit for warm air is provided in the ridge
of the roof by either ventilation chimneys or by a jack-roof. The latter is
preferable, as it provides for a more free and uniform escape.
In some drying-houses, besides the ridge openings, the space along the
eaves is left open. This would seem to be undesirable, as it provides for
the entrance of outer air, which might combat the ascending warm air and so
interfere with the natural upward currents. Provided that a jack-roof or
other suitable openings have been installed, there is, therefore, no
necessity for the existence of open spaces at the eaves, and they probably
do more harm than good.
In the tropics, on days of sunshine, there must always be an upward current
of air in well-designed houses. Temperatures of 105 deg. F. are easily recorded
in the ridge space of a building, while the temperature in the lower part
of the house may be at least 15 deg. F. lower. On the floor of an upper room a
temperature of 90 deg. F. is commonly noted, and in buildings with three
storeys the usual day temperature of the top room is about or over 100 deg. F.
Even, therefore, when there is no trace of a breeze, there must be a
displacement of air in an upward direction, though it may not be detected
without tests being applied.
It is often asked whether a temperature of 100 deg. F., such as is obtained in
the upper room, is calculated to injure the quality of the rubber. There
need be no fear on this ground; the experience of many estates goes to show
not only that no harm results, but also that the drying of the rubber is
expedited. There would seem to be no reason why crepe rubber should not be
dried at a temperature of 100 deg. F. It must be understood, however, that
higher temperatures for crepe rubber are not recommended, as it has been
proved that the rubber is affected. The fact becomes obvious with continued
treatment at temperatures much above 100 deg. F., for the rubber stretches and
breaks across the support.
WINDOWS.--Concerning the subject of window space in a drying-house, there
has been much discussion at various times. Years ago it was common to find
windows widely open with the sunshine streaming in. Naturally, tackiness
developed in some of the rubber, and care was then taken to keep the
windows closed. Thus the rooms were darkened and air excluded. There
followed a period in which windows were fitted with ruby-coloured glass to
keep out the actinic rays of the sun, which were responsible for tackiness,
and excess of light, which was supposed to be responsible for the rapid
oxidation of rubber. Unless special precautions were observed in the
processes of coagulation and preparation, it was not proved that the
exclusion of light prevented or lessened the natural oxidation of crepe
rubber. Since the introduction of sodium bisulphite for the prevention of
oxidation, there has been no cause to worry as to the possible effect of
light, as no perceptible darkening of the rubber takes place. It follows,
therefore, that no trouble need be taken to exclude light, although the
necessity for excluding direct sunshine still exists. Windows may be left
open as long as the sun does not reach them. This can usually be arranged
in a drying-house by manipulating the windows at intervals during the day,
so that those in the shady side of a building are always open, while those
on the sunny side are always closed. If it is thought that this
manipulation cannot be entrusted with success to the store coolies, the
case may be met by having all windows constructed on the louvre pattern, so
that, although the windows are closed all day, air and light are not
excluded. Should it be desired to retain the existing type of windows,
which open outwards, and to keep them open all day, a simple arrangement of
ruby-coloured cloth on an outstanding wooden frame may be placed within the
walls of the building, or the shutters of the windows may be hinged at the
top to open outwards. Unless there is a pronounced breeze, or it is
required to examine the rubber closely, there is no necessity to have
windows open, except in the case of a house in which the bottom floor is
used as a packing-room. The windows of this chamber may remain open during
the day, to advantage in sorting and packing, and also to the proper
ventilation of the building. Thus the direct rays of the sun are rendered
harmless, while air and light are allowed to enter.
HOT-AIR DRYING-HOUSES.--Mention has already been made of the existence of a
system of drying in which hot air is forced into a drying-house by means of
a powerful fan. Provided that the temperature of the hot air could be so
regulated as not to exceed 100 deg. F., there would be merit in the system.
Such matter of regulation could be solved by having a duct in the main air
passage, through which cool air could be admitted in such proportion as to
modify the temperature of the hot air. As the process is worked at present,
the temperature attained is often well above 100 deg. F., and there is a danger
of thin crepe placed in this house over-night being found upon the floor in
the morning. Unless the crepe is prepared thick and cut into fairly short
lengths, it will not bear its own weight at higher temperatures; and if it
is made thick, drying is impracticably prolonged. It is probable that, with
a temperature of 100 deg. F., and a steady current of air, average thin crepe
would dry in such a drying-house within six or seven days. This would be
an improvement upon the usual rate of drying in most factories, although
several ordinary drying-houses are known in which thin crepe will dry
naturally in that period.
SMOKE-HOUSES.--No discussion of theoretical considerations regarding the
process of smoke-curing will be attempted here. We are concerned only with
the necessity for supplying a demand for smoke-cured sheet rubber. Broadly,
the process is akin to the smoke-curing of herrings, and the objects are
much the same--viz., (1) drying, (2) preservation--except that while
herrings are only dried partially, rubber should be dried perfectly.
On a small scale a primitive smoke-house could be built easily and cheaply,
and such a building might be fully as efficacious as the most elaborate and
expensive installation. In the early days of estates it was not uncommon to
see temporary smoke-houses constructed of wood, and roofed with "attaps"
(palm leaves). Some of the best rubber in the market has come from wooden
buildings, but naturally the risk of destruction by fire is considerable.
For imperative reasons it may be sometimes found necessary to smoke rubber
when the only available building is a single-storey one. As a temporary
measure, the building may be converted into a smoke-house by placing the
fires in pits sunk deeply into the ground, and effectively screened above
by iron baffle plates. But it is not advisable that smoking be continued in
such a single-storey building, as the best effects are not obtained, and
the risk of fire is far too great.
USUAL TYPES.--At first sight it would appear that the best type of
smoke-house would be one consisting of a tall building, covering a
comparatively small superficial area, and having a number of superimposed
chambers in which the rubber could be hung to dry. In practice there are
several solid objections which limit the height and the number of floors.
Chief among these is the question of temperature. If smoke-curing is to be
effective, a certain temperature must be attained and maintained. To obtain
such results in a house of excessive height would be difficult, if not
impossible, under normal conditions. It would be found that the chamber
immediately above the furnace-room would be overheated if the temperature
in the upper rooms was within the desired range, etc.
Until recent years smoke-houses could be classed as belonging to one of two
types:
(1) Those having external furnaces.
(2) Those having internal furnaces.
The number of the former existing at the present time must be very small,
as it has been shown that the arrangement of the furnace outside the house
is unsatisfactory in comparison with the other type of house. In discussing
the question of smoke-houses, therefore, it will be understood that the
standard type accepted is that having an internal furnace. In its original
form it was known as a "Kent" drier, and consisted of a tall two-storey
wooden building. The walls of the lower chamber had the form of an inverted
and truncated pyramid. By this arrangement it was possible to obtain from a
comparatively small fire sufficient smoke and heat to cure the product
placed in the room above. This is the principle upon which many
smoke-houses in Malaya are designed. On a very large scale it is not
claimed that the sloping sides of the lower chamber lead to economy in the
number of fires, but merely divert the smoke in an upward direction. It is
acknowledged that vertical lower walls are quite effective, and it is an
easier matter to fit in doors.
It may be noted that the usual type of smoke-house now in general use
consists of a building of two storeys, in the lower of which are situated
the furnaces, while rubber is hung on racks in the upper room. Sometimes
there may be a third storey, also used as a drying (curing) chamber. As a
rule the drying-room is one long unit, as also is the furnace chamber; but
in some cases they are subdivided by vertical partitions into smaller
chambers, for ease of working and better control. This applies with some
force in the case of very long houses standing in an open space. It is
sometimes found in such cases that at certain seasons the prevailing winds
have the effect of making drying and curing uneven in parts of the
building.
With these exceptions, the ordinary type of smoke-house functions very
efficiently, and is capable of drying average sheet (from standardised
latex) in a period ranging from seven to eleven days. Should the building
not be capable of such performance, in spite of the strict observance of
all rules laid down for the processes of preparation, then there is some
defect in ventilation or in the distribution of heat.
GENERAL VENTILATION.--The ordinary rules of ventilation in drying-houses
apply equally to a smoke-house. There should be a slow current of air and
smoke from the lowest point to the highest point in the building.
In spite of all that has been written on this subject, it is by no means
uncommon to encounter the idea that a smoke-house should be perfectly
closed in order to get good results. As to what must become of the (say) 25
per cent. of moisture which the rubber contains there is no knowledge. In
dozens of cases, when complaints regarding slowness of drying have been
investigated, it has been necessary to point out the need for providing a
rational system of ventilation.
Naturally only a slow current of air and smoke is required. The creation of
an appreciable draught would have the effect of increasing the fuel
consumption of the furnaces, raising dust from the ash, and of causing a
temperature higher than that which is known to be desirable. It will be
clear, therefore, that if there are to be any openings at the base of the
walls they should be small in area, and should have some device by means of
which the current of air can be efficiently regulated. In the usual case
the construction of the building is not calculated to render it air-tight,
and the necessity for providing special air inlets does not arise.
WINDOWS.--Windows are not strictly necessary, and are only intended to be
of service during the time in which coolies are at work within the
building. The operations of examining rubber, turning sheets, removing dry
rubber, cleaning racks and floors, and putting wet rubber into position,
usually occupy some hours daily. During this interval the windows should be
widely opened if the weather is favourable, and should remain so until the
fires have been lighted. It should not be forgotten that during the heat
of the day quite an appreciable degree of drying is possible. Advantage can
be taken of this; but there is no necessity to extend the interval unduly,
and it is of greater advantage to proceed with smoke-curing when the work
in the drying-chambers has ceased.
RACKS OF SUPPORTS.--Still referring to the usual type of smoke-house, it
may be remarked that in the upper room bays of racks run at right angles to
a central passage down the length of the building. Narrower passages run
between the bays of the racks to facilitate ease in handling and
inspection. The wooden supports may be placed about 3 inches apart
horizontally, and 15 or 18 inches apart vertically. A full bay of racks
should contain nine or more lines of support in each of the planes which
are 15 or 18 inches apart vertically. The number of these planes is
governed only by the height of the room, measured from the floor to eaves.
The supports should be of smooth timber, and need not exceed 1-1/2 inches
square in section.
It is usual and advisable to smooth off the rectangular edges of the
supports or bars, to avoid the incidence of splinters of wood adhering to
the rubber. The bars should not be fixtures, but may either be accommodated
in slots, or may rest _between_ two nails, so that it is possible to give
them a rotary motion by turning the projecting ends. This practice is
followed in smoke-houses, the idea being to move the drying sheets slightly
each day, with a view to the prevention of a pronounced mark across the
sheets.
Care should be taken to see that the vacant racks are thoroughly cleaned
before fresh rubber is placed upon them, otherwise a distinct dirty mark is
caused across the middle of the sheet. This mark usually cannot be removed,
even by scrubbing with water. Where this mark occurs regularly in all
sheets, attention should be turned to the openings beneath the bays of
racks, if open fire furnaces are employed. It will generally be found that
gauze of too wide mesh has been fitted. This should be removed or covered
with a finer gauze.
A more effective way of dealing with the trouble, provided other
precautions have been taken, is to have plenty of spare wooden bars. It
should be a rule stringently enforced that, as soon as racks are emptied,
the bars should be removed to the factory to be cleansed thoroughly. A
spare set should enter the smoke-house with each batch of fresh rubber. The
actual number of spare sets required could be limited to a two days'
supply, and the extra cost would be recouped easily.
FLOOR OF DRYING-CHAMBER.--The floor of the chamber is usually of planks,
except that the space under each bay of racks should be filled with
expanded metal. With the use of wood fires there is always a large amount
of light ash formed, which may find its way into the upper chamber. To
counteract this, screens of fine mesh gauze are laid over the expanded
metal. This gauze may be fitted into a movable wooden frame, so that when
it becomes necessary to clean it the whole may be removed.
The difficulty is that with furnaces of the "open-fire" type the rise of
dust is so great that the gauze screens soon become clogged, especially as
the slight tarry matter in the smoke condenses on the gauze, causing the
dust to adhere. With the better types of furnaces, the employment of gauze
screens is not necessary, as there should be very little rise of dust. It
is sufficient to use only expanded metal, to prevent any displaced pieces
of rubber falling into the furnace chamber.
FURNACES GENERALLY.--The crudest and dirtiest method of fuel consumption in
the preparation of smoked-sheet rubber is that of making a fire on the
ground. This is still a common practice, and should be condemned as being
both wasteful and harmful. Under prevailing conditions coolies will, in
spite of instructions, heap up a pile of logs in order to save themselves
the trouble of stoking the fire in small quantity and at regular intervals.
A small supply of water is kept at hand with which to quench the fire
somewhat if it threatens to cause trouble. Naturally a large quantity of
fine ash is thus thrown up, and the rubber above receives the deposit. If
the coolie does not happen to be sufficiently awake, of course a house
burns occasionally.
From this primitive type of furnace, others have been evolved. These
usually take the form of more or less shallow trucks, the majority of
which are similar in principle to the fire on the ground, except that the
container can be withdrawn from the house for the purpose of removing the
ash. Sometimes they are even more objectionable than the ground fire,
inasmuch as, being raised above the ground level, an under-draught through
fire-bars is caused, and consumption of fuel is so much the more rapid.
PITS.--It is clear that large fires are not desirable, and that combustion
should be slow, provided that the necessary temperature can be maintained.
The lines along which the development of furnaces needed to extend are
therefore plain. The simplest device adopted was the digging of pits in the
ground. Sometimes these pits received the addition of an iron truncated
cone which was movable. Naturally the combustion was slow, but sufficient
heat was obtained if the pits were large enough or in sufficient number. An
objection was that the ash had to be cleared _in situ_, and in the process
the earthen pits gradually increased in size. In all cases it was necessary
to suspend an iron baffle-plate above the furnaces to distribute smoke and
arrest any sparks.
"POT" FURNACES.--The next development was the employment of "pot-furnaces."
These consist of iron drums, sometimes merely resting on the ground, and
sometimes mounted on trucks for easy withdrawal. These drums radiate
sufficient heat if present in sufficient numbers, and the fuel consumption
is low. They are usually manipulated by starting a fire in the bottom and
packing in logs cut to the necessary length. Some have no lids, while
others are fitted with perforated caps.
It was considered necessary in some instances to punch a few small holes
near the base of the drum in order to ensure a very slight upward draught.
In a few cases this perforation has been exaggerated to the form of a
hinged door. Unless this can be closed with ease, and is closed according
to instructions, part of the object of this type of furnace is defeated;
fuel consumption is rapid, and the temperature is too high. In the original
form "pot-furnaces" have been found to be effective on many estates, and
are still employed with satisfaction.
IRON STOVES.--Working on exactly the same principle, on some estates one
finds small iron stoves in use. Sometimes broad pipes are attached for the
better distribution of the smoke; if this is the case it should be noted
that the pipes should have a slight downward slope, and that the "bend" at
the end should be turned downwards. In this way condensed moisture and
creosotic matter falls to the ground, and does not lodge in the pipe. The
life of the conduit is thus prolonged. Usually such stoves are in use where
the "head-room" of a smoking chamber is insufficient for other types, or
where the nature of the site does not permit of sunken furnaces being
installed. They are of value likewise on occasions where the fuel supply is
limited to a rich timber such as mangrove-logs ("bakau"), when it is
necessary to ensure a low combustion with low cost of fuel.
HORIZONTAL DRUM-FURNACES.--To overcome difficulties inherent to drums or
"pot-furnaces," the next development was that in which the drum was made to
assume a horizontal position, and adapted ingeniously to a simple system of
working from the outside of the building. Reference to the drawings given
will explain how this is effected. In the first illustration (No. 2) it
will be noted that the drum is supported upon brick pillars, with one end
projecting through the wall of the building. At the other end a short
chimney is mounted, having within it a "damper" which is adjustable from
the outside. Over this chimney is suspended a simple baffle-plate, made
from a Chinese iron cooking-pan. The outer end of the drum is furnished
with a hinged and latched door, in which a small air-regulator is
accommodated.
In the second set of drawings (No. 1) the drum is increased in size and
fitted in a special manner for incorporation with a distinct type of
building. Such a scheme was first put into effect by Mr. R. C. Sherar, the
manager of Third Mile Estate, Seremban, F.M.S., and for ease of reference
the house and furnace will hereafter be mentioned when necessary as the
"Third Mile" type.
[Illustration: "THIRD MILE" TYPE; HORIZONTAL DRUM.
This type of furnace is suitable for adapting to existing buildings with
perpendicular lower walls.]
[Illustration: "THIRD MILE" TYPE OF FURNACE, USED IN CONJUNCTION WITH
"THIRD MILE" SMOKE-HOUSE.]
It will be seen that the furnace has at the farther end a door for the
removal of ash. As this, if badly fitting, may result in too great a
draught, it is well to insist upon good workmanship. Other adjustable
air-inlets are provided, and the drum is enclosed in a brick chamber.
RATE OF COMBUSTION.--However successful this furnace may have proved in the
hands of trained coolies, one must feel that with such a number of
air-inlets (whether accidental or designed) there would always be present
the possibility of obtaining too rapid a combustion. In the original forms
of drums or pot-furnaces of various kinds, a very slow rate of combustion
was attained. Naturally a relatively larger proportion of carbon remained
unconsumed, and there was a small proportion of ash. In these respects the
furnaces resembled charcoal-burners. In point of fact, some estates used
this principle for the dual purpose of smoke-curing the rubber, and at the
same time obtaining a supply of charcoal to provide fuel for their
suction-gas engines. This is a consideration in times when managers are
desirous of discovering any devices which tend towards reduction of costs.
It will be clear that, under ordinary circumstances, the condition of what
remains after the combustion of the fuel gives an indication of the rate at
which the wood has burned, and this test should apply to all furnaces. That
in which there is the most ash and the least charcoal is the one least to
be desired. In direct connection with this consideration, one must
recognise that a fire which is sunk below the level of the ground exposes
the least surface from which heat may radiate; and hence, in order to
obtain the maximum benefit of heat from a slow-combustion furnace, it
should be above ground-level, or should have a superstructure from which
the heat may be dissipated.
Simple drum furnaces, with slow combustion, have the further advantages
that a "charge" of fuel will need no attention for possibly eight to ten
hours, and practically no ash is found to be ejected. These advantages have
great practical importance. The first minimises any disabilities arising
from neglect on the part of coolies, and the second makes for increased
cleanliness in the drying-chamber. While these advantages would appeal to
most estates, there would appear to be a further advantage to small
estates which have only temporary timber smoke-houses. With a slow rate of
combustion in a furnace of this type, danger from fire is diminished
considerably.
Bearing in mind the slow rate of combustion, and hence the comparatively
low temperature obtained, it will be plain that drum furnaces should be
employed in larger number than ordinary open-hearth fires; and the drums
can be so placed as to ensure the best possible uniform distribution of
heat and smoke.
Large furnaces are sometimes seen, with flues of brickwork. In view of the
foregoing remarks, it will be obvious that these tend to large fires and a
rapid combustion, and hence must be classed as undesirable.
BRICK STOVES.--Developing from "drum" furnaces, another type comes into
existence. In principle it consists of an enclosed brick furnace, with
feeding door, and a low conical dome surmounted by an adjustable cap or
spark-arrester. The rate of combustion can be influenced by a suitable
movement of the cap, which is operated by a screw. This type of furnace has
been installed on several estates by the engineering department of Messrs.
Harrisons and Crosfield, and is understood to give satisfaction.
PATALING TYPE.--With the exception of the "Third Mile" type already
mentioned, all the furnaces described are open to a strong objection, in
that the coolies have to enter a room, usually filled with hot smoke, in
order to attend to the fires. The mere opening of the door of the building
is sufficient to fan most fires into a blaze and to raise sparks. Apart
from these points, it is natural for coolies to avoid entering too often,
with the result that they generally stoke with the maximum load of timber.
Even should they not sleep the danger is clearly great.
[Illustration: SIDE SECTIONAL ELEVATION (PATALING TYPE OF FURNACE).]
[Illustration: PATALING TYPE OF FURNACE.]
To obviate these drawbacks, furnaces which are fed from the outside of the
building were designed. There have been various forms, but as they were
first installed on Pataling Estate, in the present form, they may be known
under the description of the Pataling type of furnace. They are eminently
satisfactory, and have a low rate of fuel consumption. They are very
safe, and in fact, if worked with average intelligence in supervision, can
be regarded as being fool-proof. There is practically no ejection of fine
ash, and no fine-mesh screens need be employed. They can be adapted to any
building having either vertical or sloping walls of galvanised iron.
[Illustration: LARGE SMOKE-HOUSE OF ORDINARY CONSTRUCTION, WITH SHIELDED
VENTILATORS PERMANENTLY OPEN.
In foreground, movable folding racks on which sheets "drip" in the open
air. This smoke-house is equipped with brick furnaces fed from the outside
(Pataling Estate).]
In essential the furnace consists of a shallow pit below ground-level,
lined with brick, and having a square brick superstructure rising 4 feet
above the floor of the building. On top of the brick walls rests a sheet of
boiler-plate perforated with small holes. The hearth being below
ground-level, and with the extra 4 feet of height above the floor, it
follows that if ash is disturbed it is confined.
From the drawings it may be seen that the pit is prolonged to the side wall
of the building, with steps leading up to the ground-level. The top and
sides of the opening are made with galvanised sheeting, forming a kind of
short tunnel in which the coolie may stand upright. The outer face of the
brick furnace forms the inner end of the tunnel, and accommodates the door
of the furnace. The bottom of the pit is filled up with clay and stones
almost to the level of the bottom of the door. This ensures a very shallow
hearth, and guards against an unduly large fire. Obviously it is not
desirable or necessary to make the hearth of fire-bars, as was done in one
instance, with the provision of a door below for removing the ash. This
would lead only to a strong draught being created, with a high rate of fuel
consumption.
[Illustration: BRICK AND CEMENT SUPERSTRUCTURE OF FURNACE INSIDE THE
BUILDING, BUT FED FROM OUTSIDE.
On the top of the superstructure rests a sheet of perforated boiler-plate.
The actual fire-pit is below ground-level, and to the left may be seen
parts of the sides and top of the downward approach, from the outside, to
the door of the fire-pit.]
The openings can be screened by a narrow sloping lean-to, which serves to
keep out rain, and provides shelter for the stock of fuel and the coolie.
The iron furnace-door should be well made, with an easily worked latch; but
it is not necessary that it should be perfectly fitting. Any slight
aperture will serve to provide the necessary air-inlet, but in any case it
should not be more than slight.
CONSUMPTION OF FUEL.--Regarding this furnace, it may be said in conclusion
that it is more satisfactory in general working than any other furnaces yet
encountered. Obtaining information from over sixty estates, on the question
of fuel consumption compared with output of rubber, it was found that, as
far as ordinary smoke-houses were concerned, the Pataling type of furnace
showed the lowest unit consumption of fuel.
[Illustration: GENERAL VIEW OF SHELTERS COVERING APPROACHES TO FURNACES.]
This was at the rate of slightly less than 1 lb of fuel per 1 lb of
thoroughly cured sheet rubber. The figure on some estates mounted as high
as 4-1/2 lbs. of fuel per lb. of rubber. Naturally this factor may have
been affected by failure to utilise the drying space to its fullest
capacity, but in the main the high rate of consumption could be attributed
solely to the deficiencies of the furnaces.
FLOOR OF FURNACE-ROOM.--As a rule no attempt is made to improve the natural
earthen floor. Whether open-hearth fires, truck furnaces, or drums are
employed, it is usual to find a floor with an inch or two of dust upon it.
Where all endeavours are directed in other directions towards cleanliness,
it appears strange that this should be overlooked. In contrast, houses
employing the Pataling type of furnace (or others) have concrete and cement
floors, which can be kept quite clean. Cleanliness should be as zealously
attempted in the smoke-house as in other departments.
[Illustration: NEAR VIEW OF SHELTER.
Steps lead downwards where the wall of the smoke-house has been removed.]
ROOF.--In any type of smoke-house, the roof should fit tightly at the
eaves, and the only vent should be in or near the roof-ridge.
In an ordinary smoke-house, the opening should take the form either of a
low jack-roof or of squat chimneys protected against rain. If a jack-roof
is chosen, it may be so low as to need no scheme of adjustment, or
otherwise adjustable swing shutters must be provided. The chimneys may be
made with such low fitting between the cap and the body that no interior
swinging flaps are required.
During the operation of smoke-curing the smoke vents must remain open to a
degree which is arrived at by experience. Failure to provide a
comparatively free egress for smoke and moisture will bring trouble in its
train. After a house has been in use for some time, it will be noted that
the timber becomes covered with a shiny tarry coating deposited by the
smoke. If the rubber remained in the house for an equal period, it would
take on the same appearance. During the interval between the entry and the
exit of the rubber some amount of deposit does take place, and it is this
mixture of creosotic substances which plays a part in fitting the rubber to
withstand growths of mildew which would otherwise form.
If proper smoke-vents are not provided, the moisture evaporating from the
sheets is unable to escape quickly enough, with the result that a great
deal condenses at night-time upon the inner surface of the comparatively
cool roof, and falls back upon the rubber in unsightly black "drips," which
leave a distinct mark on the sheet. Even if vents are open, this may happen
during seasons of rain. The temperature of the moist smoke in the
roof-ridge may be as high as 130 deg. to 140 deg. F., while the outer atmosphere
may have been cooled by rain to 70 deg. F. Such a difference on the two
surfaces of the roof must lead to condensation within the house, with
consequent "dripping." It used to be the custom to drape sacking material
above the bays of racks in order to prevent the drops of liquid falling
upon the rubber; but often for want of renewal the last state was worse
than the first. Modern houses have often an inner lining, a few inches
below the roof. This is made of soft wood which receives any product of
condensation and absorbs it.
OTHER TYPES OF SMOKE-HOUSE.--So far we have confined the arguments to
smoke-houses of the usual type. There are others which vary in either
design and method of working, or in the material of the structure. Mention
may be made of the most prominent of these.
BRICK HOUSES.--Some houses are constructed of brick, and may have one or
two storeys above the furnace chamber. The floors are sometimes made of
ferro-concrete, and the furnaces may also be of this material. These brick
houses give satisfaction, but there would seem to be some difficulty in
obtaining and maintaining the desired temperature, although it is not quite
plain why this should be so. The principle of these buildings is the same
as that of the ordinary iron house, and the suggestions made in previous
paragraphs apply with equal force.
"THIRD MILE" TYPE.--Reference has been made to the "Third Mile" type of
furnace. This is an integral part of a smoke-house, which for clearness of
distinction may be known as the "Third Mile" type of smoke-house, the
original of which was erected on the Third Mile Estate, Seremban, F.M.S.
[Illustration: "THIRD MILE" TYPE OF SMOKE-HOUSE.]
In essence the design consists of a building, having two storeys for
rubber-drying, and a shallow inverted pyramidal base, ending on the ground
in "Third Mile" furnace, already described and illustrated.
It will be seen that the principles of ventilation employed are those
indicated for an ordinary house--viz., air-inlet near the ground (with
little draught), and smoke-vent at the roof-ridge. The windows shown in the
drawing are only for purposes of inspection of the rubber during the day,
and form no part of the scheme of ventilation during the hours of smoking.
It is claimed that the efficiency of the house is high. Certainly the work
of attending to the furnaces is simplified, and there should be small
ground for excuse if negligence is displayed.
JACKSON HOUSE.--This was brought into notice under the description of the
"Jackson Cabinet," and it was claimed that average sheets could be dried in
a few days. It consisted of a small house of one storey, having several
tiers of racks. Smoke and heat were generated in a small stove placed
outside the wall. A smoke vent was provided in the roof. These cabinets had
a certain vogue as part of a small unit installation, with a fair degree of
success. It is not clear, however, that such speed in drying is required.
(This point will receive further attention in a subsequent chapter.)
"DEVON" TYPE.--In its full original design this type owes its origin to Mr.
H. E. Nixon, General Manager of the Devon Estates, Malacca, where it forms
part of unit divisional installations worked under a scheme of
decentralisation.
The original units consisted of a building erected with an iron framework
covered with sheets of asbestos-slate, and a roof of galvanised iron.
The novelty in design lies in the utilisation of external platforms upon
which the racks of bars supporting the sheets of rubber may be drawn out of
the smoking chambers, and on which the racks are loaded and unloaded. By
this device it is possible to remove the contents of any compartment bodily
without interfering with the continuity of curing in the other
compartments. That is to say, smoking in such a house can proceed day and
night if necessary, and yet the rubber in any part of the house can be
examined, can be removed, or can be replaced without cessation of smoking.
It will be seen from the illustrations that the house is more or less of
the same general design as the "Third Mile" type, with the addition of
external platforms. It has two storeys for the reception of rubber; and a
basal furnace-room with sloping sides converging downwards into a pit
containing a large drum-furnace. This is mounted on a low truck, and
travels on a short length of railway.
[Illustration: GENERAL VIEW OF DOUBLE "DEVON" TYPE OF SMOKE-HOUSE.
The platforms are common to both units. Building of brick with iron roof
(Batu Caves Estate).]
Each of the curing-rooms is divided into four compartments (making eight
compartments in all). These are closed by swing doors, each of which is the
full width of a compartment, and has a slight overlapping edge. Through
these doors light railways run into the house and out upon the platforms.
On the rails "bays" of racks run, and when fully loaded they are easily
moved. The racks were designed with a frame of stout hard wood, but light
angle-iron could be utilised.
[Illustration: GENERAL VIEW OF DOUBLE "DEVON" SMOKE-HOUSE AND FACTORY
BUILDINGS.
Timber in foreground cut to length for stoking. Note water-tower and engine
cooling-tanks adjacent to factory.]
The chimney style of smoke-vent has an internal butterfly flap, which is
controlled by means of a wire from the outside. In the ordinary course of
smoke-curing, it is advised that this flap should be permanently open so as
to reduce the possibility of internal condensation of moisture and
creosotic matter. The exact degree to which it should be open must be found
by experience.
[Illustration: VIEW OF PLATFORM OF "DEVON" SMOKE-HOUSE; DOORS OF
COMPARTMENTS OPEN, AND ONE RACK PARTIALLY WITHDRAWN.
Note below each rack opening through which smoke rises, covered with wire
netting.]
Although reference has been made several times to compartments, it should
be understood that the chambers are not subdivided internally by means of
partitions. There exists only the external effect of compartments in the
form of the eight swinging doors which allow for the withdrawal of, or
insertion of, any one unit of racks at any time without interference with
the bulk of the rubber.
[Illustration: DOUBLE "DEVON" SMOKE-HOUSE OF BRICK, WITH ROOF OF CHINESE
TILES, SHOWING LOADING PLATFORMS WITH RACKS WITHDRAWN FROM SMOKING
CHAMBERS.
Federated Engineering Co., Ltd., Kuala Lumpur.]
[Illustration: SIDE VIEW OF PRECEDING PHOTOGRAPH, SHOWING EXTERNAL
ARRANGEMENT FOR STOKING FURNACES.
Federated Engineering Co., Ltd., Kuala Lumpur.]
DETAILED DESCRIPTION.--As enquiries are often received it is permissible to
reproduce the following detailed description of the original house. This
appeared in the Fourth Local Report (Malaya) 1916, issued to subscribers by
the Rubber Growers' Association.
"The house has a steel frame-work, 22 feet long, 16 feet wide, and 22
feet high. Of the length, 14 feet is occupied by the platforms, and 8
feet by the chambers. These measurements can be varied. The whole of
the width (16 feet) is occupied by compartments of which one series is
placed above the other.
[Illustration: FRONT VIEW OF DOUBLE "DEVON" TYPE OF SMOKE-HOUSE.
Glenmarie Estate: Batu Tiga Co.]
"_Platforms._--The loading verandahs or platforms are of ordinary
'seriah' timber.
"_Compartments and Furnace Chamber._--These are enclosed with Bell's
'Poilite' sheets, each of which measures 8 feet by 4 feet by 3/16
inch. The sheets are affixed to the steel stanchions, doors, etc., by
galvanised bolts (1 inch by 1/4 inch) which pass through iron flats
measuring 8 feet by 2 inches by 3/8 inch (about). These iron flats
hold the sheets at the edges. The dimensions of the compartments are 8
feet by 8 feet by 4 feet.
"_Racks._--These are eight in number, and measure just under 8 feet by
8 feet by 4 feet. The capacity of each is roughly about 450 lbs., of
dry sheet rubber. The racks are mounted on 6-inch iron wheels, running
on rails of stock size, 'T' iron (1-3/4 inches by 1-3/4 inches by 1/4
inch).
"The sheets are hung on split bamboos. To prevent these projecting
over the edge of the rack and catching in the doors when the rack is
moved in or out, a thin strip of wood, about 1/2 inch high, is nailed
along the sides of the rack.
[Illustration: SIDE VIEW OF DOUBLE "DEVON" TYPE OF SMOKE-HOUSE.
Building constructed of galvanised iron. Shows door to furnace
chamber, and ventilator.]
"_Furnace._--This is of the type that aims at slow combustion. It
consists of a cast-iron cylinder, 3 feet in diameter and 4 feet high,
carried on a truck made of a sheet of boiler-plate, and mounted on
small wheels, so that the whole can be moved easily out of, and into,
the furnace chamber for easy cleaning and stoking.
"The furnace chamber is a pit lined with concrete, just wide enough
to take the trolley, and about 12 feet long. The top of the furnace,
which is almost flush with the ground-level, consists of a sheet of
zinc or galvanised iron with numerous holes about 3 inches in
diameter. Over these holes are strips of mosquito gauze, as flame and
dust arresters (see note below). There are no holes in the sides or
bottom of the cylinder.
"Over the furnace is hung a baffle-plate, measuring 4 feet by 4 feet.
Above this, on the first floor-level, the bottom of the compartments
is covered with wire netting, to prevent any rubber dropping
accidentally into the furnace chamber. The furnace chamber is fitted
with an iron-frame door, swinging on perpendicular hinges.
"_Method of Stoking._--The timber used is a mixture of jungle wood and
rubber-tree wood, cut to lengths of about 1-1/2 feet. In the ordinary
way the furnace is charged at 6 p.m., and at six-hour intervals a
little more fuel is added, but a new charge is not necessary. During
the daytime, when the heat of the sun is sufficient to raise the
temperature appreciably, a smaller fire is maintained.
"_Temperature._--There is no difficulty in maintaining a temperature
of 120 deg. F. By continuous smoking, average sheets prepared from
standardised latex can be fully cured in five days. This represents
110 hours of smoke-curing, which is at least equal to ten days'
intermittent smoking in an ordinary house.
"_Capacity._--There are eight racks, each accommodating 450 lbs. of
standardised sheet rubber. The loading capacity of the house,
therefore, is 3,600 lbs. As each charge is cured in five days, the
monthly output may be 21,000 lbs.
"The cubic capacity is 2,048 cubic feet. As there are no gangways,
etc., this is fully utilised. This gives a rate of monthly output
capacity to over 10-1/4 lbs. dry rubber per cubic foot of drying
space; an excellent figure much in advance of values obtained in the
great majority of ordinary smoke-houses."[18]
[18] Since the above was written, it has been found possible to eliminate
the gauze. A mild steel top has been made, perforated with 2-inch holes.
Practically no dust is ejected from the furnace, and there are no flames.
Owing to shortage of supplies during the War, similar buildings have been
erected with frames of well-seasoned hard wood, which was protected by
strips of asbestos-slate or galvanised iron. The latter material was also
substituted in the covering walls. Later, houses were erected of brick,
with other minor modifications. As a natural development, the latest
buildings consist of two of the original houses face to face, under a
common roof, and served by common platforms.
As originally designed, the house was intended to meet the needs of a small
estate, or a division of an estate, having a maximum output of about 20,000
lbs. of sheet rubber per month. The possibility of an extension of this
idea has been shown to be great.
The furnace has been described as situated in a pit. Situated on a bank or
on sloping ground, it was easy to arrange for withdrawal of the furnace. In
some cases this has not been possible, and various modifications have been
effected. The most satisfactory yet encountered is that in which a shallow
brick pit is surmounted by an iron cone, about 4 feet in height. This is
fitted with a cap having small perforations. The fire burns in the pit, and
the heat is radiated by the cone. It would have been more effective to have
allowed greater height in the furnace chamber, and to have employed the
travelling drum-furnace as in the original design.
In order to avoid interference in draught by a space between the bottom of
the doors of the compartments and the platform (due to the presence of
rails), the floor of the platform is laid level with the top of the rails;
or to the bottom of the doors is attached a swinging flap, notched for
accommodating the rails when in position.
* * * * *
There are in use houses of other designs, which all more or less vary only
in some modifications from the types described. Hence they do not call for
special comment. Recently a rather distinct departure has been noted in a
structure designated the "Barker" smoke-house.
BARKER PATENT.--In essential this consists of a long narrow structure
erected with an appreciable slope from one end to the other. At the lower
end is a small furnace enclosed in a brick compartment. The smoke from this
furnace travels up the slope to the other end, at which the rubber enters.
The sheets are hung on bars which are attached to a unit framework. This
frame slides, by its own weight, upon timber side supports. A sufficient
number of these units occupies the full effective length of the structure.
The removal of "stops" at the lower end enables the foremost frame to be
removed, and the succeeding frames slide into a new position. Thus the
freshly prepared sheets, entering at the higher end, gradually and
automatically move towards the furnace as the frames of dry rubber are
removed from the lower end.
[Illustration: THE NEW "BARKER" TYPE OF SMOKE-HOUSE: A SMALL UNIT.
The racks slide automatically from top to bottom on withdrawal of the lower
frames through door at front. The furnace is contained in the brick
compartment at the lower (front) end.]
Thus far only small units have been seen. It is claimed that, properly
prepared, sheet rubber can be smoke-cured in about five or six days, and it
is stated that installations have been in successful working for
sufficiently long periods to prove their efficacy. The device is better
known in Java and Sumatra than in Malaya. The capacity of a unit building
is stated to be 7,000 lbs. per month, calculating on a six days' cycle of
working. In a more recent design provision is made at the lower end for a
water tank, into which all rubber can be discharged in case of fire.
CHAPTER XVI
_OTHER BUILDINGS (continued) AND SITUATION OF BUILDINGS_
SORTING-ROOM AND PACKING-ROOM.--It is in these departments that most
factory installations are lacking. More often than one cares to
acknowledge, sorting and packing are done under conditions which place a
premium upon poor work. As a consequence, consignments of rubber are often
marred by the inclusion of defective specimens. The result is that
shipments may be rejected when tendered against contracts, or that
allowances in price have to be made. In many instances it would not be fair
to lay the blame upon the manager or an assistant, as it is obviously
impossible for an individual to inspect every piece of rubber. Neither
would it be strictly fair in some cases to ascribe the fault to pure
carelessness on the part of the coolies.
Often the only provision made for this important work is the lower room of
a drying-shed, which may also contain hanging rubber. Under these
circumstances, space is cramped, and the light often poor. Small defects
may pass unnoticed, and the general surroundings do not conduce to keen
work.
Where, for economic reasons, the sorting and packing operations are
conducted in the drying-shed, there should be ample space free from hanging
rubber, and it should not be possible for wet rubber placed in the upper
room to drip upon the dry rubber below or upon packed cases. There should
be plenty of light, and for this reason windows should be ample. Usually
the window-frames are fitted with wooden shutters, which are preferably
hung on horizontal hinges from the top of the frame. By this device it is
not necessary to close all windows during a shower of rain, and rubber may
be stacked near a window with reasonable chance that direct sunlight will
not be allowed to fall upon it.
In dealing with smoked sheet, it is advised that the rubber to be examined
should be placed upon tables facing the windows, so that each piece may be
scrutinised in a strong light.
Crepe rubber also is best examined in a strong light, but preferably with
one's back towards the source of light or at an angle to it. For this work
coolies usually are most efficient when sitting on the floor.
It will be clear from the foregoing remarks that the best conditions would
be secured in a separate building especially constructed. A single room
would be all that is required; at one end sorting could be undertaken,
while packing could be done at the other end. No hanging rubber should be
allowed in the room.
The floor should be of hard timber, and raised from the ground, to the
height approximately of a bullock-cart or motor-lorry, as the case may be.
The boxes of rubber could thus be transported by small hand-trucks on a
level with the transport vehicle, reducing labour to the minimum.
The ventilation of the building should be good, especially if cases of
rubber are to be stored therein; and the entire structure should be
weather-proof.
STORE-ROOMS FOR RUBBER AND STORAGE.--The question of storage of rubber in
factory buildings has always possessed importance, but has demanded
increased consideration recently.
From experience in this country, it is clear that cement floors for
store-rooms or packing-sheds are the least suitable. They are often visibly
damp, especially in the early morning. To allow rubber, packed or unpacked,
to remain upon a cement floor in the tropics, is to court trouble from
moulds, external or internal. If the employment of a cement floor is
unavoidable, the rubber and boxes should be raised on wooden supports,
giving a clearance of at least 3 or 4 inches, and there should be clear
ventilation space between tiers of boxes.
Experience indicates that the best type of floor is that already advised
for sorting and packing rooms--_i.e._, a good hard timber floor raised at
least 3 feet above ground-level. Apart from the advantage in labour
specified in the previous paragraphs, this provision of ample ventilation
space below the floor is a great consideration in the preservation of the
timber. Raised store-rooms become essential in low-lying districts which
are at all subject to flooding, yet the writer has seen many boxes of
rubber damaged by flood-water entering a packing-room situated on the
level.
The question has often been raised recently as to the length of the period
during which rubber may be safely stored in this country. The answer can be
only supplied by experience, of which up to the present we have none
possible of being classed as reliable. Whatever storage may have been done
in the past has been influenced greatly by the unsuitability of the storage
accommodation, and the fact that often the rubber was not prepared with a
view to prolonged storage.
While the market demand was strong, rubber was being shipped and passed
into circulation, at a rate which did not demand investigation of the
subject of local storage. In the year 1918 conditions were such as to bring
the matter into prominence, and we were able to tender advice on the lines
given in this chapter. The necessity passed, but has again arisen.
Our experience goes to prove that if rubber is properly prepared and
thoroughly dried before packing, it will remain in good condition for a
period of a year or more in this country. How much beyond a year it may be
kept remains to be determined. The assumption of "proper preparation"
leaves great room for reservations.
In the case of crepe rubbers, there is no great difficulty, provided that
the recognised methods and formulae are employed, and that the rubber is
packed only when perfectly dry. Under those conditions, the higher grades
of crepe remain apparently unaffected on storing. Any appreciable
deterioration may be attributed to defective preparation or external
causes, such as accidental damage by water.
The prolonged storage of lower grade rubbers is attended by more risk,
especially in the case of the lowest grade (earth-scrap) from estates which
neglect the practice of regular and frequent collection of the raw product.
The same reservation applies to crepes made from tree-scrap which is not
collected daily. In these types of crepe rubber "tackiness" may be
initially present only in small degree, but the final damage may be
immensely greater by close contact of the folded rubber during prolonged
storage.
When we come to discuss the possibility of storage of smoked sheets, the
difficulties become immensely greater. We have yet no reliable experience
as to the keeping properties of this grade when properly prepared, fully
cured, correctly packed, and stored under the best of local conditions. It
is understood, of course, that in the qualification by the term "local"
conditions, we assume it to be more difficult to store rubber generally in
Malaya than in a temperate climate. The average temperature and humidity of
the atmosphere are here much more favourable to the development of mould
growths than would be the case, say, in Great Britain.
In discussing this question, as far as it refers to the preservation by
storing of smoked sheet rubber, it is not fair to draw conclusions as to
the likely behaviour of packed rubber from data based upon observation of
loose specimens. We have samples of smoked sheets prepared in 1910, and
these, superficially, appear to have remained unchanged. No mould is
present and, as far as intermittent observation enables us to judge, moulds
have never been incident. Whether such rubber would have been preserved in
this condition had it formed part of a packed case, is a point upon which
we have no experience; neither can we give any opinion. It seems true,
however, that loose specimens "keep" better than bulk samples of the same
preparation.
It cannot be argued that the present good condition of these old specimens
may be due to correct preparation. In those days methods and formulae were
rather haphazard, especially in view of the fact that the daily variability
of dry rubber content of latices was not then recognised.
One would rather submit the factor of adequate smoke-curing as the chief
influence in the superficial preservation of smoked sheets. Ten or eleven
years ago it was considered advisable to allow the rubber to remain in the
smoke-house for a period extending well beyond that necessary for ordinary
drying. As a result, very dark rubber was produced, which was thoroughly
impregnated with the products of wood combustion. There would seem to be
little doubt that this procedure was responsible for the prolonged freedom
from mould growths.
Market standards have varied to some degree since, with a tendency to
prefer a paler product than that in vogue, say, six or seven years ago.
Moreover, standardised methods of preparation have been introduced, with
the result that sheets of a desirably high standard can be produced in from
ten to fourteen days, when smoke-curing is conducted only during night
hours. Some estates are equipped with smoke-houses which, by continuity of
working day and night, provide smoke-dried rubber in from five to six days;
but the actual hours of smoke-curing are approximately equal to those of
the ordinary type of house.
This tendency towards the production of sheets paler in colour than the old
standard is probably largely responsible in the present for the commonly
observed incidence of surface moulds on stored smoked sheets, and also for
some complaints of "under-curing," where the term specifically refers to a
failure to dry and cure the rubber thoroughly. Boxes of smoked sheets,
which had been stored for varying periods up to five months, were recently
inspected, and, in the majority of instances, surface moulds were found to
be plentiful. In all cases it was observed that the trouble was intensified
where boxes of rubber were stored in contact with cement floors.
This "under-curing" is not a question solely of the duration of
smoke-drying, although probably the modern practice of curtailing the
period has exerted a great influence. To make this clear, it may be stated
that, given two batches of uniformly prepared wet sheets, it would be
possible to smoke-cure them for equal periods in different houses, so as to
produce one batch very much paler in colour than the other, although the
total hours of actual smoke-curing would be identical. In order to produce
such effects, all that is necessary is to employ different timbers for fuel
or different types of furnaces. In the one case there would be produced
heat and very little smoke, while in the other the necessary heat would be
obtained plus plenty of smoke. The best results naturally are obtained by
the employment of the happy medium, and if smoked sheets have to be stored,
the ordinary period of smoke-curing should be prolonged to an interval
consistent with the capacity of the smoke-house.
All precautions taken in preparation and curing can be nullified, as
already indicated, by unsuitable storage conditions.
TOOL-SHEDS AND STORE-ROOMS.--In some factories it is the rule to see lime,
cement, spare rolls, sieves, and a general heterogeneous assortment
occupying part of the rubber-drying rooms. The inconvenience is often
great; and it certainly seems that these stores and tools are of sufficient
value to be accommodated in suitable buildings.
SITUATION OF FACTORY BUILDINGS.--There can be no doubt that a great deal of
the "spot" disease trouble, and the general slowness of drying, can be
attributed in many factories to the unsuitability of the site chosen.
Probably the idea which actuated those responsible for the choice of site
generally was proximity to a water supply. This would account for the fact
that a number of factories are situated in valleys or near swamps. More
often than not, also, the actual clear space is very limited, and rubber
trees grow close up to the walls of the buildings. Under such
circumstances, it is difficult to see how these buildings can be anything
but dark and damp, and it is not difficult to understand the slow rate of
drying. In a few cases the sites chosen proved to be so unsuitable that the
estates were confronted with a very serious problem, the solution to which
was, either the erection of another complete set of buildings in a more
suitable spot or the installation of artificial driers.
It must be laid down as an axiom that the first essential in a suitable
site is that water may be brought to it easily, but, as already indicated,
this does not mean that the buildings need be placed in actual proximity to
the water-supply. The mistakes made by pioneers in this work are not likely
to be repeated, and it is common now to note well-designed and
comprehensive schemes in which the water is pumped to a reservoir placed at
a suitable elevation, whence the supply is gravitated to bungalows, coolie
lines, and the factory. The importance of securing a plentiful supply of
good water for factory purposes cannot be exaggerated, and it is a point
which is only thoroughly appreciated on estates where smoke-sheet rubber
has to be prepared.
The second essential, but of equal importance, is that there shall be an
ample open space on which the sun may shine all day. There must be no trees
too near the buildings, and there should be no adjacent swamps. Preferably,
the site should be on a raised position, so that it will be impossible for
surrounding trees to cut off sunshine, even when they are fully grown. From
such an arrangement it will follow that the factory will be light and airy,
and the drying-houses will receive the maximum of benefit to drying from
direct sunshine on the roof and walls. There can be little doubt that these
considerations play a most important part in determining the rate of drying
of the rubber, and where comparisons are made between the rates of drying
in various drying-houses all these factors enter into the question and
contribute to the total result. Presuming that the thin crepes made in two
factories are equal in thickness, it is not uncommon to find that in a
drying-house, situated in a wide open space, the period of drying may be as
low as six or seven days; while in another drying-house, situated near a
swamp and surrounded by trees, the period may be as high as eighteen days
to twenty-one days. The figures quoted are not fictitious, but are facts
actually noted in the course of the writers' experience.
A great deal also depends upon the exact position of buildings. Thus, to
obtain the maximum of light in a factory, it will be obviously beneficial
to erect it with the long sides running east and west, so that the windows
face the north and south, and the large end doors face the east and west
respectively. At first sight it would appear that the best position for the
machines would be on the north side of the building where no sun can enter;
but a moment's consideration shows that the south side would give the best
results. By the time the sun has come round to the south, it is usually
high in the heavens, and the direct sunshine does not fall very far into
the room. Even should it play upon the machines for an hour or two during
the day, no harm could result to the rubber which was being worked, as no
piece would remain there a sufficiently long time to be injured in the
slightest degree. Placed in this position, the maximum benefit of light
would be obtained, whereas if the length of the building ran east and west,
the machines would have only either the morning or afternoon light.
[Illustration: SUGGESTED ARRANGEMENT OF BUILDING.]
While it is advisable to erect a factory running east and west, the
drying-houses should run north and south. In this position the maximum wall
area will be exposed to the sun during the day, and it will be possible to
manipulate the windows of the drying-rooms so that those along one side are
open, and it will never be necessary to close all the windows at any time
of the day. Thus the windows facing east will be closed, and those facing
west will be open until after midday; then _vice versa_. With such an
arrangement a more uniform temperature may be obtained than by any other
arrangement of the buildings. If the building ran east and west, the
windows on the north side could remain open all day, while those facing
south would have to remain closed practically all day. The south side of
the house would be heated by the sun, while the north side would remain
cool, and the rates of drying would be correspondingly unequal. The total
wall area heated by the sun at any time of the day would be less in this
position than if the house ran north and south.
Similarly, to obtain the best drying effect during the daytime in a
smoke-house the building should run north and south. By this means the
temperature will be maintained to the maximum possible by sun heat, and the
rate of drying will correspond.
_References to Sketch Plan._
Drying-house No. 2 should be of two storeys, and unless a separate sorting
and packing room is to be built, No. 1 should also have two floors (see
previous notes on packing-rooms).
In the factory--
_V_ shows the position of the verandah, which may be quite open and
only divided from the inner room by
_S_, a wall composed of very strong expanded metal, which allows light
and air to enter the factory.
_T,T_ are the glazed tile tanks for the reception of latex, scrap
rubbers, and bark-shavings.
_M_ shows the position of the machines on the south side of the
factory, with the direction of extensions, and
_E,E_ the compartments in which the engines are bedded. In these
positions it is possible to obtain direct drive to the machines.
_D,D_ are large double swing or sliding doors (the latter for
preference always). These, while suiting transport of rubber, provide
also for a free draught of air.
If possible the scrap-washing machine should be placed outside the wall of
the factory, and tanks for the reception of scrap rubbers may then be
situated in convenient proximity.
Economy of labour is obtained by grouping all factory buildings as closely
as possible, but it should be borne in mind that smoke-houses should be
regarded as a possible source of danger from fire. This point has a
practical bearing upon rates of insurance, and it is essential that the
smoke-house should be situated at a minimum of 50 feet from any other
building or group of buildings. In this connection, also, it may be noted,
as being of further practical interest, that, in the insurance of
smoke-houses, preferential rates are given to those having a good type of
slow-combustion furnace.
CHOOSING A FACTORY SITE.--Sufficient has been written to make it clear that
the choice of a site for factory buildings is a matter demanding weighty
consideration. Much, of course, depends upon the planted area, and the rate
at which it comes into bearing. Under certain circumstances which will be
obvious, it is permissible to instal first a group of buildings of a
temporary nature only, the future site and permanent buildings to be chosen
later when the main portion of the estate comes into bearing. Often,
however, one finds that, from lack of forethought, the estate has been
committed to considerable expense in the establishment of equipment, which
later is proved to be unfavourably situated with regard to the majority of
the area in ultimate bearing. In such case, transport of latex is fraught
with difficulties and may be expensive.
In the instance of an estate which will gradually come into bearing, it is
not easy to decide whether a temporary installation shall first be
provided, or whether, in anticipation of future demands, a complete
equipment shall be erected. So much depends upon the financial aspect of
the question, and upon the rate at which areas will come into bearing. As
far as is possible, the best policy would be that of a compromise under
which the site would suit later requirements, and the factory would be so
planned as to be capable of future easy extensions both of buildings and
machinery.
It is not possible to lay down any definite data as regards requirements
based on acreage, or to make comparisons between any two estates of similar
acreage. The important factors determining such requirements are:
(_a_) Area.
(_b_) Shape of the estate.
(_c_) Topography of the estate.
(_d_) Available supplies of water.
Naturally the ideal site for factory buildings would lie in a central
position, given other favourable conditions.
CENTRALISATION OR DECENTRALISATION.--It is the experience of a number of
estates that, all other conditions being favourable, there is a limit
beyond which the centralisation of factory work leads to an unwieldy
position. We are not here concerned with the few extremely large estates
running into tens of thousands of acres. In those cases the total area
would be divided into economic sections. The argument there would resolve
itself into a discussion on the size of an economic section. This, in turn,
would be dependent upon the type of main product, involving the question of
transport of latex or coagulum, and the possible provision of batteries of
heavy machinery.
The differentiation between the transport of latex and coagulum,
respectively, is a most important one, and has a powerful influence in
determination of the maximum of centralisation possible. Whereas properly
prepared coagulum may be safely transported by bullock-cart, light-railway,
or motor vehicle for many miles, latex, on the other hand, demands very
careful treatment. Anti-coagulants may be employed to preserve fluidity,
but only within certain limits. Even under these conditions, other factors
(chiefly climatic) exert an influence which renders the transport of latex
for any distance a matter of anxiety.
It will be plain, therefore, that the limits of centralisation of factory
work are much narrower for the preparation of sheet rubber than is the case
when crepe rubber is to be made. In actual experience the preparation of a
high standard and a high percentage of smoked sheet is attended with
considerable difficulty in those cases where the factory processes have
been ultra-centralised. Apart from the difficulties inherent to the
transport of latex in a state of good preservation, there is the added
difficulty of dealing quickly with large volumes of latex brought from
various quarters. None of these should be allowed to remain standing if the
best results are to be secured; but obviously there must at times be some
congestion. Even on a small scale it is often found that the latest batches
of latex are unfit for the preparation of good sheet rubber, and the
trouble may be easily exaggerated when working on a large scale.
The centralisation of work on crepe preparation, therefore, is limited only
to a comparatively slight degree by distance of transport, and in the main
only by the size of the necessary equipment of machinery and drying
accommodation.
The successful preparation of sheet rubber is, on the contrary, governed
chiefly by the factor of transport. With this consideration in view,
several large estates, preparing sheet rubber as the chief grade, have
found it necessary to decentralise the factory work, with very satisfactory
results. Outlying sections are given uniform and complete equipments of
necessary buildings on a small scale, and hand-driven light machines.
Uniform coagulating tanks are installed, and the methods and quantities of
chemicals employed are carefully standardised. Experience has shown that
often the best sheet rubber coming to the market has been prepared on small
estates; and the same applies to the product of these decentralised
stations on large estates. There is no _a priori_ reason why the product
from one station should differ in the smallest particular from that of
another, apart from minor fluctuations which are due to variable weather
conditions affecting the latex. If the contrary is found to be the case, it
indicates failure on the part of the person responsible to follow the
regular rules and methods.
In the natural scheme of development of a large estate, it would be
necessary, of course, to have a comparatively small centrally situated
factory, equipped with power and heavy machinery for working scrap rubbers
in the preparation of crepe grades below No. 1 in quality. As the yield per
acre increases, or the area in bearing expands, it would be advisable later
to increase the size of the central factory and buildings so as to permit
of the preparation of a proportion of the crop in the form of No. 1 crepe
rubber, in order to be able to comply with prevailing market demands under
which preferential rates fluctuate between pale crepe and smoked sheet.
PART IV
THE FINISHED RUBBER
CHAPTER XVII
_DEFECTS IN CREPE RUBBERS_
GENERAL STYLE OF FINISH.--Broadly, there is no single and definite style of
finish, but on the whole it may be stated that the greater proportion of
crepe rubbers are prepared in a thin form and with a close-knit texture or
finish.