_WATER FOR LOCOMOTIVE BOILERS._
HOW WATER GETS MIXED WITH LIME.
Throughout a very wide area of territory in the United States and
Canada, limestones, or various forms of calcareous rocks, constitute
the upper rock stratum immediately underlying the subsoil of the great
agricultural regions. During the stupendous operations of Nature in
building up this continent, the rocks have been subjected to vast
disintegrating agencies: they have been torn and eroded by huge masses
of ice; they have been burned by the rays of the unshadowed sun;
fractured by the congealing power resulting from deep-searching frost;
melted by water,--that most universal solvent in nature; then scattered
far and wide by ice and flood. This process has been so complete, that,
in the whole limestone territory, all the earth seems charged with
lime. Limestones are very sparingly soluble in pure water; but the
rain that falls from the clouds is not pure, but contains a charge of
carbonic acid that acts chemically upon the lime, forming salts, which
the water readily dissolves. Owing to this circumstance, there are few
streams, and fewer wells, in the calcareous districts that are not
contaminated with lime. The water that passes into streams, generally
runs over surfaces that have been washed partly free from lime; and, in
consequence of this, creeks and rivers are not so badly tainted with
lime-salts as the water in wells that stands saturating the rocks. The
appearance or taste of water gives no indication of the quantity of
lime held in solution; for the ice-cold well, or sparkling spring, that
supplies water so pleasant to drink, may yield so much lime-salts that
the water would be ruinous to sheets and flues when used for boiler
purposes.
EXPENSE ENTAILED BY USING BAD WATER.
Considering the financial influence of the matter alone, it might be
supposed that parties building railroads would exercise diligence in
selecting the best water that possibly could be secured for boiler
purposes, since the operating expenses are largely magnified by using
impure water; but for many years the subject appeared to receive no
attention whatever from those best able to regulate the water supply,
and water stations were established without any consideration as to the
character of the water available.
It is owing to the absence of care in the original locating of water
stations, that numerous tanks are to-day drawing their supply from
bad wells, where surface water could easily be obtained. Railroad
companies are peculiarly conservative about making changes that
entail expenditure of money: and existing evils in the water supply
arrangements are often continued, because some expense would be
incurred in making them; although no kind of money expenditure would
bring a more ample return in economy.
EFFORTS OF MASTER MECHANICS TO SECURE GOOD WATER.
The paramount importance of the quality of water used in locomotive
boilers, has been long recognized by nearly all master mechanics;
for the effect of bad water is brought to their attention in an
unmistakable manner. The subject has been frequently before the Master
Mechanics’ Association for investigation. A report of a committee
appointed at an early meeting to investigate the subject, declares
that “Master mechanics have had the conviction forced home, that
impure water is the bane of good boilers;” and, even then, a vigorous
effort was being made to eliminate the injurious ingredients from
the water; and the work was carried on in a hopeful and confident
spirit, which was indicated by the words of a subsequent report, which
asserted that “Different waters differ widely in the component parts
of the impurities they contain, and each requires separate study and
treatment;” but the committee were satisfied that the engineering
and mechanical skill of railway men could readily devise a suitable
appliance for each particular case. In those days, railroad men thought
that they could, by mechanical and chemical means, purify bad water,
and render it suitable for boiler use. Purifying bad water proved
about as difficult an undertaking as reforming the average bad man is
recognized to be; and few railroad men can now be found who believe a
purifying process can be successfully performed on the large quantity
of water needed for locomotive boiler feeding.
LOSS OF FAITH IN PURIFYING METHODS.
The conclusion that artificial methods of purifying bad water can not
be carried out in railroad water supply, was not arrived at hastily. It
was reached by slow degrees, and through the convincing ordeal of many
disappointments, with methods and nostrums that promised to effect the
desired results.
Experience demonstrated, that, in the limestone regions, the proper and
only way to avoid trouble from lime incrustation in locomotive boilers,
is to obtain soft water from streams, or by collecting the rainfall in
ponds or reservoirs.
SCALE-MAKING AGENCIES.
Water, as has been mentioned, is the most universal solvent in nature;
and what is known as hard water contains many foreign ingredients,
but those that exercise such a pernicious influence upon locomotive
boilers are lime and magnesia. The scale-making lime appears in two
forms,--sulphate of lime, and carbonate of lime. The former is the
more dangerous and troublesome scale-making agent; the latter is most
frequently met with.
Ordinary well-water will be found to contain solid matter in solution
varying from 10 to 100 grains to the gallon. Under 20 grains to the
gallon of impurities may be considered fair water if the principal
ingredient is carbonate of lime, but that amount of sulphate will
make highly objectionable boiler water. Where the use of well-water
is unavoidable on a road, quite a saving to boilers can be effected
by ascertaining the quantity and character of the impurities received
from each water-tank, and directing the engineers to avoid those that
contain the worst scale formers.
TO ASCERTAIN THE QUALITY OF WATER.
The proper way to ascertain with accuracy the character of water, is
to send specimens to a competent analytical chemist for quantitative
analysis. But, as few railroad companies will incur the expense of
having the water of the water stations systematically tested, master
mechanics may, by a little labor, study, and practice, learn to make
tests for themselves that will indicate near enough for practical
purposes the character of each water station supply.
As master mechanics are the railroad officials most directly interested
in the kind of water supplied for locomotive use, they ought to have
direct control of all the water stations on the roads where they are in
charge.
APPLIANCES NEEDED IN TESTING WATER.
The chemical apparatus needed for the examination of well-water are,
a balance that will weigh accurately to half a grain; an oil stove
for evaporative purposes; a few pint porcelain evaporating dishes; a
sand-bath, which can be made from a piece of sheet-copper; a dozen
test tubes; half a dozen vials to hold solutions of chemically pure
chemicals; some pieces of glass tubing; a small mortar and pestle;
a supply of filtering-paper; and the vessels needed for measuring
accurately. For the solution of the chemical re-agents to be used, a
supply of distilled water is necessary; and water of this kind is also
necessary to make comparisons with. A piece of pure crystalline ice,
when melted, will generally produce water pure enough for experimental
purposes.
PREPARING FOR THE EXPERIMENTS.
In bringing in water for examination, it is best to have it drawn from
the water-tank into a perfectly clean jug, which should be corked and
labeled. Weigh an evaporating dish, noting down the exact weight, and
on a sand-bath evaporate one quart or half a gallon of the water to
be inspected. When the dish becomes dry, rub off all dust that may
be adhering to the bottom, and weigh the dish. The added weight will
indicate approximately the total amount of solid matter in the water.
Note that down, and every other detail of the experiments.
LIME HELD IN SOLUTION BY FREE CARBONIC ACID.
Sometimes a large quantity of bicarbonate of lime is held in solution
by free carbonic acid, which escapes as soon as the water is boiled,
leaving the lime to subside in the form of mud. Water of this kind may
appear very hard, yet not be very objectionable for boiler use; since
the deposit can be blown out if the blow-off cock is used freely.
To test this, boil a pint of water for two or three minutes in a
perfectly clean dish, then pass it through a filter paper that has been
previously dried and weighed. When the operation is finished, dry and
weigh the filter paper again; and the added weight will indicate the
amount of solid matter held in solution by free carbonic acid gas.
TEST FOR LIME SALTS.
Superficial tests that will indicate the condition of the water from
the coloring produced by the impurities combining with chemicals that
take them out of solution, can be made in the following manner: Five
test tubes are half filled with water to be tested. The first one will
be examined for lime in any form. A teaspoonful of aqua ammonia is put
in the water for the purpose of stimulating the chemical action, then
twenty drops of a solution of oxalate of ammonia are added. The degree
of turbidity will indicate the quantity of lime in the water. Should
the quantity of lime be very small, the test tube would have to be kept
in a warm place a few hours before the re-action showed itself.
TEST FOR SULPHATE OF LIME.
The water in the second test tube will be examined for sulphate of
lime. A few drops of hydrochloric acid are first put into the water,
then twenty drops of chloride of barium. A white precipitate, which
generally makes its appearance at once, indicates the presence of
sulphuric acid. In water belonging to the calcareous regions, it may
safely be concluded that the sulphuric acid is held in the form of
sulphate of lime. An exception has sometimes to be made for water drawn
from the vicinity of coal mines, and such places, where sulphate of
iron abounds. Water that holds sulphuric acid in this form is readily
identified by a test for iron salts.
When it is found that water gives a strong re-action indicating
sulphate of lime, the inference may safely be drawn that the tank it
came from should be avoided.
TEST FOR CARBONATE OF MAGNESIA.
The third test tube may be examined for carbonate of magnesia, which is
found freely mixed with the water of many wells. Put aqua ammonia in
this tube, and add twenty drops of a solution of phosphate of soda. A
crystalline precipitate will indicate the presence of magnesium. Where
carbonate of magnesia is present in considerable quantities in water,
it sometimes forms along with lime a thick, porous scale; and in other
cases it is apt to float on the top of the water, causing trouble by
making the boiler foam. If an engine boiler has got scale formed from
water free from magnesia, and goes on to a division where this impurity
abounds, the magnesia will take off the old scale before it begins to
form new incrustation. A few pounds of common salt put into the tender
daily will have a good effect in preventing trouble with magnesia;
since it forms chloride of magnesia, which is a decided preventive of
lime scale.
TEST FOR SALTS OF IRON.
In the fourth test tube we will search for iron salts. A solution of
potassa or ammonia will produce, should iron be present, a whitish
precipitate, which presently turns to a dirty green, and, ultimately,
a reddish-brown color, owing to its absorption of oxygen from the
air. A more delicate test for iron is ferro-cyanide of potassium, or
sulpho-cyanate of potassium; but other mineral combinations might
deceive a novice using these reagents into the belief that iron was
present when it was not. A light trace of iron in water is very common;
and, so long as it is in minute quantities, the salt seems quite
innocent. But occasionally water is found saturated with iron in the
form known by chemists as _FeSOᵥ{4}_. Then it is very objectionable for
boiler-feeding; since it exercises a strong corrosive action on the
plates, pitting and furrowing being a common result of its action.
Scale formed by water of this character is nearly always a hard, thin
substance, that sticks with intense tenacity, and generally takes away
part of the skin of the iron when it is taken off.
TEST FOR CHLORINE.
The fifth tube we will examine for common salt, which is nearly always
present in water. This test is done by dropping in some nitrate of
silver solution, which produces a white precipitate, caused by the
silver combining with the chlorine, which is the principal element
in common salt. This is an excessively fine test, and the nitrate of
silver will detect an incredibly small trace of common salt in water.
The worst effect that common salt has in water, is to cause priming.
Where it is present to any great extent, the blow-off cock should be
used frequently on the road; and a surface-cock is quite an aid in
keeping the boiler in order. Water that is taken from wells or streams
about cities, and found to give strong chlorine re-actions, is nearly
always contaminated with sewage.
LEARNING THE MANIPULATION OF TESTS.
Practice in making superficial qualitative tests of water, produces
skill in reading the meaning of the various chemical re-actions. This
skill can be rapidly developed by practice on prepared specimens. Water
for experiments on carbonate of lime can be prepared by dissolving
calcite crystals or marble dust in hydrochloric acid, or by mixing
chalk with clean rain-water, and filtering it till free from turbidity.
While the chalk is mixed with the water, and unfiltered, the specimen
will be made stronger by blowing air from the lungs through a glass
tube into the water. A preparation for testing sulphate of lime may
be made by dissolving some gypsum in distilled water. Fluid magnesia,
dropped into pure water, will provide carbonate of magnesia specimens;
and Epsom salts will give the magnesia re-action, with the addition
that it will indicate sulphuric acid under the chloride of barium
test. A grain of salt no larger than a pin-head dropped into a pint of
distilled water, will give a distinct chlorine test when nitrate of
silver solution is added. Stronger, or even weaker, salt solution can
be used by the experimenter while he is working into practice. A small
piece of sulphate of iron, dissolved in water, will provide a test for
iron.
MAKING QUALITATIVE TESTS.
While pursuing the apprentice practice of tests with these solutions,
care must be taken to have the test tubes perfectly clean. Go over the
tests in something like the following order. The carbonate of lime test
is to be made first. Four test tubes will be used. In the first we put
distilled water alone; in the second we put ten drops of the chalk
solution; in the third we put twenty drops of the solution; in the
fourth we put thirty drops, then add distilled water till all the test
tubes are about two-thirds filled. Drop into each tube about the same
quantity of oxalate of ammonia solution, and the degree of turbidity
will help to indicate the hardness of each specimen. The first tube,
containing pure water, will give no re-action if the chemicals are pure.
This process should be extended to all the other solutions, and will
be found very helpful. In carrying out experiments of this kind,
much assistance will be obtained from having a work like Stuckhardt’s
_Chemistry_ at hand for reference.
THE SOAP-TEST FOR HARDNESS.
Most people are aware that hard water has a peculiar effect upon soap,
making it curdle instead of lather when used for washing purposes. This
peculiarity was made use of some years ago by Dr. Clark of Aberdeen,
Scotland, in devising a test for the hardness of water, in which the
quantity of a standard soap solution needed to produce a permanent
lather on water, indicated the degree of hardness of the water. A
modification of the Clark process can be used very conveniently by
master mechanics in making superficial tests of the hardness of water,
and the plan has the advantage of being easily applied. With a test
tube and a small bottle of soap-solution, the investigator is ready
at any time or place to make tests; and a few minutes spent over each
specimen will give him an idea of the value of the water for boiler
purposes.
The original Clark soap-test was made with a soap-solution of known
strength, of which a certain measured quantity was required to
produce a permanent lather on a gallon of water containing a given
quantity of carbonate of lime. The degrees of hardness of other
specimens were computed according to the quantity of the soap-solution
required to produce a permanent lather. Preparing soap-solution of a
certain strength, and water of a certain hardness, for the purpose
of indicating a point for beginning the computations, is a tedious
operation; and the soap-test can be used in a much simpler way. While
making numerous tests of water on the Burlinglington, Cedar Rapids, and
Northern Railway some years ago, to ascertain the condition of water
tanks at different seasons of the year, and in examining the supply of
proposed water stations on extensions of the road, I used the following
modification of the Clark process:--
MODIFICATION OF THE CLARK SOAP-TEST.
The Cedar River, during its normal flow in summer, contains about ten
grains of solid matter, mostly calcium carbonate, to the American
gallon of 58,373 grains. This I considered good boiler-water, and
made it the standard of comparison for my tests. Beside the shop,
there is a well, which the people who built the road dug for supplying
boiler-water; although the Cedar ran a few rods distant. This
well-water contained about forty grains of solid matter to the gallon,
one-fourth of the impurity being sulphate of lime. This water I made my
“awful example” standard of comparison, so that water approaching this
in hardness was condemned.
The soap-solution I made by dissolving seventy grains of castile soap,
or white soap-powder, in a pint of alcohol. Care must be taken that
all the soap is dissolved, and then it is best to keep the mixture in
an even temperature not below 60° Fahr. The tests can be made more
accurately by having the water under examination brought to the same
temperature as the soap-solution.
APPLYING THE SOAP-TEST.
In making the tests, a measured quantity of the Cedar water was put
into a stoppered bottle. One ounce of water put into a two-ounce bottle
is a convenient quantity. The soap-solution was then measured out with
a pipette made to hold thirty drops, and the bottle was well shaken
after each measure till it was found that a lather was formed which
held on for five minutes. The operation was then repeated; and the last
charge from the pipette was put in, drop by drop, till the point where
a permanent lather formed was noted. A similar performance was gone
through with the bad well-water, and very little practice enabled the
operator to ascertain where a specimen of water stood between the range
of the good and bad water.
The soap-solution must be kept in a properly stoppered bottle; and,
every time a new solution is made, its strength must be tested in the
above fashion. The solution deteriorates when kept longer than a month
or six weeks.
The degree of turbidity caused by the first charge of soap-solution, is
an indication to the practiced experimenter of the degree of hardness
of the water.
Most men interested in ascertaining the condition of boiler-water, can
devise means for obtaining water of known hardness wherewith to make
comparative tests.
If water under examination prove very hard, the test will be more
accurately done by diluting it with its own volume of distilled water.
The soap-test is good for lime in all its forms, and magnesia; but the
latter impurity uses up more soap than lime does. So, where magnesia
abounds in water, the specimen under trial will seem harder than it
actually is. Magnesia is also slower than lime in acting upon the soap.
Water that contains magnesia will produce a lather when enough solution
is put in to overcome the lime present; but if it be allowed to stand
a few minutes, till the magnesia acts, the lather will not then form.
The presence of certain alkaline salts in water, such as the carbonates
and sulphates of soda and potash, injuriously affects the soap-test by
making the water appear softer than it is; since they accelerate the
forming of a permanent lather. Keeping these facts in mind will often
prove of valuable service in making tests of water.
When the soap-test indicates that water contains hardening ingredients,
representing more than fifteen grains to the gallon, other tests should
be at once made to ascertain what the leading ingredients are.
DIFFICULTIES OF PURIFYING WATER FOR LOCOMOTIVES.
The nostrums offered to railroad managers for purifying feed-water
are legion, but it is doubtful if a single remedy has proved entirely
successful. In most instances, the material or means used have been
worthless or impracticable; but, in other cases, the appliances have
not received justice from those attending their application. Most
people underrate the magnitude of the task involved in undertaking to
render the impurities of feed-water innocent in locomotive boilers.
The case of a learned professor who undertook to doctor the feed-water
for locomotives on a prominent road, where he made his arrangements
for each engine using one thousand gallons of water a day, is
representative. When provision has to be made for some engines using
double that quantity each hour, the difficulty of the transaction
becomes apparent. As has already been said, I believe that obtaining
soft surface-water is the proper way to avoid trouble with locomotive
boilers; but, where this is impracticable, considerable saving can be
effected by “doctoring” the water if the operations are intelligently
conducted.
MUD.
Mud is the most universal impurity of feed-water; and, in many cases,
it causes the destruction or injury of sheets, particularly the
crown-sheets of fire-boxes. Where the water of a road is habitually
muddy, it would pay to filter the water, or to have two tanks at each
water station, so that a system could be followed of letting the water
settle in one tank while the other was in use. The settled mud, by this
means, could be washed out regularly before a tank were refilled.
CARBONATE OF LIME.
Dr. Clark, inventor of the soap-test, recommended a method of purifying
water containing carbonate of lime, which has been successfully
followed in many places, especially in England. It consists of adding
caustic lime to water containing carbonate of lime. By this process,
28 grains of caustic lime result in the precipitation of 100 grains
of lime carbonate. Or, to put it in a practical shape, where a tank
contains 30,000 gallons of water, each gallon being impregnated with 30
grains of lime carbonate, 36 pounds of caustic lime will be sufficient
to precipitate the whole of the impurity, making a total deposit of 164
pounds.
SULPHATE OF LIME.
Where the water impurity is principally sulphate of lime, the caustic
lime remedy will not work; but a precipitate of the objectionable
compound can be made by treating the water with caustic baryta or
caustic soda. In the first case, the baryta takes possession of the
sulphuric acid holding the lime in solution, allowing the latter to
fall down as mud: when the soda cure is applied, the sulphuric acid
deserts the lime, and combines with the soda, for which it has greater
affinity, leaving the lime to precipitate, unless it be preserved in
solution by the carbonic acid that accompanied the soda.
Where the water contains a mixture of lime sulphate and carbonate,
the soda treatment may be advantageously used in combination with the
caustic lime system.
Attempts have frequently been made to purify water by putting chemicals
into the locomotive tenders, the impurity being precipitated in the
boiler. The leading objection to this system is, that it leads to
enormous quantities of sediment being deposited inside the boiler;
since, in some instances, the purifying substance is as bulky as the
original impurity. In other cases, the chemical introduced into the
boiler causes foaming. Let us take the case of water that contains
fifteen grains of sulphate of lime to the gallon, and is treated with
sulphate of baryta. To do so properly, one grain of the chemical will
be required for each grain of lime. A freight engine uses seventy-five
gallons of water to the mile, and runs one hundred miles a day. This is
light service, both for water and mileage; yet, within ten days, nearly
three hundred pounds of solid matter is injected into the boiler.
To purify water by injecting chemicals into locomotive boilers, and
prevent the boiler filling up rapidly with mud, or giving trouble from
foaming, the blow-off cock and surface cock must be used so frequently
as to be felt on the consumption of coal. Where purifying of feed-water
_must_ be done, the right place to carry on the process is in the
station tanks, or in special appliances beside them. By carefully
watching the character of the impurities in the water, and treating
them with their proper precipitants, labor and expense devoted to the
purification of feed-water may bring in good returns: where attempts
are made to improve the water over a whole road by one method of
treatment, failure is certain.