_HARD-STEAMING ENGINES._
IMPORTANCE OF LOCOMOTIVES STEAMING FREELY.
As the purpose of a locomotive engine attached to a train is to take
that train along on time, and as engines are generally rated to pull
cars according to their size, it is of the utmost importance that
they should make steam freely enough to keep up an even pressure on
the boiler while the cylinders are drawing the supply necessary to
maintain speed. A locomotive that does not generate steam as fast as
the cylinders use it, is like a lame horse on the road, a torture to
itself, and to every one connected with it.
ESSENTIALS FOR GOOD-STEAMING ENGINES.
To steam freely, an engine must be built according to sound mechanical
principles. The locomotives constructed by our best manufacturers, the
engines which keep the trains on our first-class roads moving like
clock-work, are designed according to proportions which experience
has demonstrated to be productive of the most satisfactory results
for power and speed, combined with economy. There are certain
characteristics common to all good makers. The valve-motion is planned
to apply steam to the pistons at nearly boiler pressure, with the
means of cutting off early in the stroke, and retaining the steam long
enough in the cylinders to obtain tangible benefits from its expansive
principle. Liberal heating-surface is provided in the boiler, its
extent being regulated by the size of the cylinders to be supplied with
steam. With a good valve-motion, and plenty of heating-surface served
with the products of good coal, an engine must steam freely if it is
not prevented from doing so by malconstruction or adjustment of minor
parts, or by the wasting of heat in the boiler or in the cylinders.
An engine of that kind will steam if it is managed with any degree of
skill. But as the best lathe ever constructed will turn out poor work
under the hands of a blundering machinist, so the best of locomotives
will make a bad record when run without care or skill. Regular
feeding--the water supplied at a rate to equal the quantity evaporated,
which will maintain a nearly level gauge--is an essential point in
successful running. It is hardly second in importance to skillful
firing.
CAUSES DETRIMENTAL TO MAKING STEAM.
When an engine is steaming badly, almost the first action of an
experienced engineer is to examine the petticoat-pipe. The influence
which this pipe exercises on the steaming qualities of an engine has
already been adverted to, but its importance can not be too strongly
urged upon the attention of the young engineer. It is one of the most
successful devices invented for regulating the vacuum in the smoke-box,
so that the currents of hot gases shall flow evenly through all the
flues. Any thing which interferes to disturb the flow of these
currents, crowding them away from any section of the flue-surface,
will have a prejudicial effect upon the steam. The pipe may be set too
high to produce an even draught, or the fault may be in the opposite
direction. Its diameter may not be suitable for the conditions of
smoke box and stack, or its shape may be at fault. Not unfrequently
the pipe is fastened obliquely, so that the blast impinges on the side
of the stack, producing evil results; or the braces which keep it in
position occasionally break, and the draught is permitted to shoot in
every direction but the direct way to the atmosphere, and the effect is
immediately apparent on the steam-gauge.
PETTICOAT-PIPE.
The petticoat-pipe performs, in relation to draught, functions of
a similar nature to those performed by the tubes of an injector in
inducing the flow of water; and its efficiency is reduced by the same
disturbing agencies. The pipe must have a size in proportion to the
diameter of stack, and it must be set so that it shall deliver the
exhaust-steam to make a straight shoot through the stack. When these
conditions are properly arranged, the exhaust-steam goes through the
stack like a piston, leaving a vacuum behind. The petticoat-pipe is
a device confined mainly to American locomotives; and its purpose is
to regulate the draught in the smoke-box so that the currents of hot
gases are drawn uniformly through the flues, the top, bottom, and
sides getting about the same heating intensity as passes through the
middle rows. The opportunity for the exhibition of good firing depends
greatly upon the petticoat-pipe being constructed properly, and secured
at the right position. It is impracticable to lay down a positive
rule for dimensions and best position of these pipes, for engines
of the same proportions frequently require different petticoat-pipe
arrangements to make them steam freely. For our 17 × 24 engine, there
is a petticoat-pipe 11½ inches in diameter, with a flare, at bottom,
17 inches wide. The pipe reaches within 3 inches of the bottom of the
stack, and is set one inch above the nozzle. This gives good results
in our case. When engines with sufficient heating-surface do not steam
freely, the trouble nearly always lies in malproportioned or badly
set petticoat-pipes. Sometimes a very small change in the position of
this pipe will have a wonderful effect upon the steaming qualities of
the engine. If the pipe is set too high, most of the draught will pass
through the lower flues; and the upper rows will become filled with
soot, and many of them are likely to get choked with fine ashes, which
remains there for want of draught to force it out. Should it be too
low, the bottom rows of flues will suffer from the effect of defective
draught. When the petticoat-pipe is just right, the flues will look
uniformly clean inside, which can be ascertained by a close inspection
of the smoke-box. In addition to making the engine lose the benefit of
its full heating-surface, a badly arranged petticoat-pipe concentrates
the draught so much that it tears the fire to pieces at one particular
point; and the only resource for the man who wishes to keep up steam
is to fire heavily, thereby preventing cold air from being drawn
through the crevices. Many engines will not steam with a light fire,
and yet do well with a heavy body of coal on the grates. In nearly
every instance of this kind, the fault lies in the petticoat-pipe;
and, if this is properly adjusted, the engine will be found capable of
carrying a light fire, and will show far more economical results than
could be reached with heavy firing. Some engineers assume that the
petticoat-pipe must be right when an engine steams freely, even though
a heavy fire is necessary to produce this result. This is a mistake.
It may be badly set or badly proportioned, only a degree smaller
than it is where the engine will not steam to keep the train going.
By closely watching the action of the blast on the fire of an engine
that calls for heavy firing, the engineer learns where the fault lies.
When the engine is laboring on a hard pull, he should open the door;
and if he finds, that, in a particular section of the fire-box, the
smaller pieces of coal are dancing and glowing with an incandescence
more brilliant than the other parts, and if he finds that this is
repeatedly the case, he may conclude that the nozzles are too small,
or the petticoat-pipe is working the mischief with his coal-account.
Should the nozzles be the proper size, he had better lose no time in
beginning to experiment with this pipe. He can lower it a quarter of an
inch at a time, and mark the effects of the change on the fire. Should
that produce no improvement, he may try raising it; or, if there is a
movable sleeve on the top, that may be set in different positions. An
engineer can test a petticoat-pipe much better by manipulating it on
the road than in the round-house. If no change of position will improve
the working of the pipe, one of different dimensions should be tried.
Perseverance in this line will bring the right thing in the end. I
knew an engineer who tried five different petticoat-pipes before the
proper one was reached. Such a thing causes labor, and needs patience;
but it pays when the fuel-account for running ten thousand miles comes
in.
THE SMOKE-STACK.
The ordinary purpose of the smoke-stack is to convey the smoke and
exhausted gases to the atmosphere. If it is intended to perform its
functions in a straightforward manner, it is made about the same
diameter as the cylinders, and its highest altitude rises from 14
to 15 feet above the rail. The stack is a simple-enough article to
look at, yet a vast amount of inventive genius has been expended upon
attempts to expand its natural functions. Attempts have been made
to utilize it as an apparatus for consuming smoke, and hundreds of
patents hang upon it as a spark-arrester. Patentees, in pushing their
hobby, seem occasionally to forget that a locomotive requires some
draught, as a means of generating steam; and stacks are frequently so
hampered with patent spark-arresters that the means of making steam are
seriously curtailed. Were it not for the danger of raising fires by
spark-throwing, it would be more economical to use engines with clear
smoke-stacks; and the extended front end, with open stack, is a good
move in this direction.
OBSTRUCTIONS TO DRAUGHT.
Every obstruction to free draught entails the use of strong artificial
means to overcome it. The usual resort is contracted nozzles, which
induce a sharp blast, and use up more fuel than would be required
with an open passage to the atmosphere. Among the obstacles to free
steaming, that come under the category of obstructed draught, may
be placed a wide cone fastened low, and netting with fine meshes.
When the draught passage is interrupted to a pernicious extent by
spark-arresting appliances, their effects can be perceived on the fire
when steam is shut off; for the flame and smoke prefer the fire-box
door to the stack as a means of exit. Sometimes steam-making is
hindered by the netting getting gummed up with spent lubricants and
dirt from the cylinders. Cases occur where this gum has to be burned
off before free draught can be obtained. Waste soaked with coal-oil
will generally burn off the objectionable coating.
CHOKING THE NETTING WITH OIL.
Gumming of the netting is usually caused by carelessness in oiling
the valves. Some runners will shut off for a minute while the fireman
oils the valves, and the lubricant scarcely gets time to reach the
steam-chest when the throttle is opened wide again; and instead of
soaking over valves and cylinders, and into the remotest part of
piston-packing, the oil goes through the stack with the first puff of
steam. It is best, in oiling the valves, to leave the cup-plugs open
long enough for the oil to be sucked out of the pipes. Then, when steam
is applied, it should be done by slightly opening the throttle, so that
it will work the oil into the piston-packing; and, after a few turns
run this way, there will be no loose oil left to defile the netting.
SILICIOUS DEPOSIT ON FLUE-SHEET.
Certain kinds of coal deposit a hard, silicious substance upon the back
flue-sheet, which gradually accumulates till the draught is seriously
impeded. This, of course, prevents the full benefit of the hot gases
being obtained; and consequently the steam goes down. Flues stopped
up with cinders produce a similar effect. The flues getting choked up
with cinders is not always an indication that the petticoat-pipe is
performing its duty improperly. Stopping up of flues is often caused
by wild, unskillful firing. A shovelful of coal pitched high, deposits
part of its load direct in the flues; and some pieces that are a close
fit do not go through. They stick half way; and small cinders soon
follow, that quickly close up the entire passage.
THE EXTENDED SMOKE-BOX.
By this arrangement, the spark-arresting device is transferred from the
smoke-stack to the smoke-box, and the exhaust steam escapes direct to
the atmosphere, without meeting obstruction from a cone or netting. The
netting is generally an oblong screen, extending from above the upper
row of flues to the top of the extended smoke-box, some distance ahead
of the stack. This presents a wide area of netting for the fire-gases
to pass through. The draught through the flues is regulated by an
apron or diaphragm-plate, extending downwards at an acute angle from
the upper part of the flue-sheet. With the long exhaust-pipe used with
the extended smoke-box, the tendency of the exhaust is to draw the
fire-gases through the upper row of flues. The diaphragm-plate performs
the same duties here, of regulating the draught through the flues
equally, as the petticoat-pipe does with the diamond-stack. It is of
great consequence, for the successful working of the engine, that the
draught should be properly regulated: otherwise there will be trouble
for want of steam.
When an engine having an extended smoke-box does not steam properly,
experiments should be made with the diaphragm fastened at different
angles, till the point is reached where equal draught through the flues
is obtained. Closing the nozzles, as a means of improving the steaming
of such an engine, is certain to make matters worse.
STEAM-PIPES LEAKING.
The blowing of steam-pipe joints in the smoke-box is very disastrous
to the steaming qualities of a locomotive. This has a double action
against keeping up steam. All that escapes by leaking is so much
wasted, and its presence in the smoke-box interrupts the draught.
If the steam-pipe joints are leaking badly, they can be heard when
the fire-door is open and the engine working steam. Some experienced
engineers can detect the action of leaky steam-pipe joints on the fire;
but the safest way to locate this trouble is by opening the smoke-box
door, and giving the engine steam.
DEFECTS OF GRATES.
Grates that are fitted so close as to curtail the free admission of
air below the fire prevent an engine from steaming freely. The effect
of this will be most apparent when the fire begins to get dirty. This
is not a common fault. I once knew of an engine’s steaming being very
seriously impaired by two or three fingers in one section of grate
being broken off. The engine steamed well with a light fire, till, in
dumping the fire at the end of a journey, the men knocked some of the
fingers off. Next trip, it seemed a different engine. Nothing but heavy
firing would keep up an approach at working-pressure. I experimented
with the petticoat-pipe without satisfaction, assured myself that no
leaks existed among the pipes; the stack, with its connections, was
faultless; and the engineer was puzzled. The defect was discovered by
watching the effect of the blast upon the fire. Signs of air-drawing
were often to be seen at the point where the broken fingers were. This
was where the mischief lay. Too much cold air came through, unless the
opening were bedded over by heavy fire.
A drop-grate that did not close properly had a similar effect upon
another engine which came under the author’s notice; and a change,
which shut the opening, effected a perfect remedy.
LIME, SCALE, AND MUD.
In calcareous regions, where the water-supply for locomotives is drawn
from wells, the most common cause for bad-steaming engines is leaky
heating-surfaces, or water-surfaces incrusted with lime deposits.
When he sees water pouring from flues and stay-bolts, an engineer has
no difficulty in divining the reason why his engine steams poorly;
nor need he be far-seeing to perceive a remedy in the boiler-maker’s
calking-tools skillfully applied. The case of incrustation is,
however, more difficult to comprehend in all its bearings. When water
containing lime-salts touches the hot flues or fire-box, evaporation
takes place; and the solid substance previously in solution is left
behind, and adheres to the heating-surfaces, gradually forming a
refractory scale which is an indifferent conductor of heat. As this
scale becomes thick, it stands up, like a non-conducting barrier,
between the water and the hot sheets; and it takes a much greater
expenditure of heat to evaporate the water inside, just as a kettle
coated with scale is much harder to boil than a clean one. When a
boiler gets badly fouled with scale and mud, these impurities exercise
a pernicious effect upon the steaming qualities of a locomotive.
PREVENTING ACCUMULATION OF MUD IN BOILERS.
Mud-drums, with blow-off cocks attached, serve to check the growth
of this evil when the engineer is careful to make frequent use of
these appliances; and a strong pressure of washing-out water, poured
frequently through the boiler, has an excellent cleansing effect: but
some kinds of scale defy mud-drums and the best methods of washing
out, leaving the only resort to be the removal of flues for cleansing.
The filling up of a boiler with scale and mud, so as to prevent the
engine from steaming freely, is necessarily a gradual process; and
an observant engineer has time to note the change, and recommend the
proper remedy.
TEMPORARY CURES FOR LEAKY FLUES.
Leaky flues or stay-bolts may sometimes be dried up temporarily
by putting bran, or any other substance containing starch, in the
feed-water. Care must be taken not to use this remedy too liberally,
or it will cause foaming. It is, however, a sort of granger resort, and
is seldom tried except to help an engine to the nearest point where
calking can be done.
GOOD MANAGEMENT MAKES ENGINES STEAM.
No engine steams so freely but that it will get short under
mismanagement. The locomotive is designed to generate steam from water
kept at a nearly uniform temperature. If an engine is pulling a train
which requires the evaporation of 1,500 gallons of water each hour,
there will be 25 gallons pumped into the boiler every minute. When
this goes on regularly, all goes well; but if the runner shuts the
feed for five minutes, and then opens it to allow 50 gallons a minute
to pass through the pump, the best engine going will show signs of
distress. Where this fluctuating style of feeding is indulged in,--and
many careless runners are habitually guilty of such practices,--no
locomotive can retain the reputation of doing its work economically.
INTERMITTENT BOILER-FEEDING.
The case of Fred Bemis, who still murders locomotives on a road in
Indiana, is instructive in this respect. Fred was originally a butcher;
and, had he stuck to the cleaver, he might have passed through life
as a fairly intelligent man. But he was seized with the ambition to
go railroading, and struck a job as fireman. He never displayed any
aptitude for the business, and was a poor fireman all his time through
sheer indifference. But he had no specially bad habits; and, in the
course of years, he was “set up.” He had the aptitude for seeing a
thing done a thousand times without learning how to do it. All his
movements with an engine were spasmodic. Starting from a station with a
roaring fire and full boiler, the next stopping-point loomed ahead; and
to get there as soon as possible was his only thought. He would keep
the reverse-lever in the neighborhood of the “corner,” and pound the
engine along. The pump would be shut off to keep the steam from going
back too fast, till the water became low: then the feed would be opened
wide, and the steam drowned down. In vain a heavy fire would be torn to
pieces by vigorous shaking of the grates. The steam would not rally,
and he would crawl into the next station at a wagon pace. A laboring
blower and shaker-bar would resuscitate the energies of the engine in a
few minutes if the flues and fire-box were not leaking too badly, and
the injector would provide the water for starting on; but no experience
of delay and trouble seemed capable of teaching Bemis the lesson how to
work the engine properly. He soon became the terror of train men, and
the boiler-makers worked incessantly on his fire-box. But he is still
there, although he will not make an engineer if he runs for a century.
TOO MUCH PISTON CLEARANCE.
On one of our leading railroads a locomotive was rebuilt, and fitted
with the extension smoke-box, which was an experiment for that road,
and consequently was looked upon with some degree of distrust. When
the engine was put on the road, it was found that it did not steam
satisfactorily. Of course, it was at once concluded that the draught
arrangements were to blame; and experiments were made, with the view
of adjusting the flow of gases through the tubes to produce better
results. The traveling engineer of the road had charge of the job, and
he proceeded industriously to work at locating the trouble. He tried
every thing in the way of adjusting the smoke-box attachments that
could be thought of, but nothing that was done improved the steaming
qualities of the engine. He then proceeded to search for trouble in
some other direction. The result of his examination was the discovery
that the engine was working with three-fourth inch clearance at
each end of the cylinders. This, he naturally concluded, entailed a
serious waste of steam; so he had the clearance reduced to one-fourth
inch. When the engine got out after this change, it steamed very
satisfactorily; and the extension smoke-box is no longer in disrepute
on that road.
BADLY PROPORTIONED SMOKE-STACKS.
Mistakes are frequently made when the open stack is adopted, as is
practicable with the extended smoke-box, of making the stack too wide
for the exhaust. This leads to deficiency of draught for the steam
that is passing through the stack, because the steam does not fill the
stack like a piston creating a clean vacuum behind it. Where an engine
fails to steam freely after being equipped with an extended smoke-box,
attention should be directed to the proportion of stack diameter to the
size of cylinders.
THE EXHAUST NOZZLES.
Locomotives, with their limited heating-surface, require intense
artificial draught to produce steam rapidly. Many devices have been
tried to stimulate combustion, and generate the necessary heat; but
none have proved so effectual and reliable as contracted exhaust
orifices. As the intermittent rush of steam from the cylinders to
the open atmosphere escapes from the contracted openings of the
exhaust-pipe, it leaves a partial vacuum in the smoke-box, into which
the gases from the fire-box flow with amazing velocity. As the area of
the exhaust nozzles is increased, the pressure of steam passing through
becomes lessened, and the height of the vacuum in the smoke-box is
decreased. Consequently, with wide nozzles, the velocity of the gases
through the flues is slower than with narrow ones; for there is less
suction in the smoke-box to draw out the fire products: and, where the
gases pass slowly through the flues, there is more time given for the
water to abstract the heat. Any change or arrangement which will retain
the gases of combustion one-tenth of a second longer in contact with
the heat-extracting surfaces, will wonderfully increase the evaporative
service of a ton of coal. Experiments with the pyrometer, an instrument
for measuring high temperatures, have shown that the gases passing
through the smoke-box vary from 400 degrees up to 900 degrees
Fahrenheit; and they show that increase of smoke-box temperature keeps
pace with contracted nozzles. From this, engineers can understand
why lead gaskets do not keep blower-joints in a smoke-box tight, the
melting-point of lead being 627 degrees.
Inordinately contracted nozzles are objectionable in another way.
They cause back pressure in the cylinders, and thereby decrease the
effective duty of the steam. Double nozzles are preferable to single
ones; because with the latter the steam has a tendency to shoot over
into the other cylinder, and cause back pressure.
Engineers anxious to make a good record, try to run with nozzles as
wide as possible. Contracted nozzles destroy power by back pressure:
they tear the fire to pieces with the violent blast, and they hurry the
heat through the flues so fast that its temperature is but slightly
diminished when it passes into the atmosphere. The engineer, who, by
intelligent care, reduces his smoke-box temperature 100 degrees, is
worthy to rank as a master in his calling.
The other day an engineer came into the round-house, and said, “You had
better put 3½ inch nozzles in my engine: I think she will get along
with that increase of size.” He had been using 3¼ inch nozzles. The
change was accordingly made. When he returned from the next trip, he
expressed a doubt about the advantage of the change. But it happened
that his own fireman was off, and a strange man was sent out, who,
although a good fireman, failed to keep up steam satisfactorily. On
the following trip, however, the fireman who belonged to the engine,
returned, and found no difficulty in getting all the steam required.
But this fireman is one who would stand far up among a thousand
competitors. Considerable practice and intelligent thoughtfulness,
combined with unfailing industry, have developed in this man an
excellence in fire management seldom attained. He follows a unique
system, which seems his own. It is the method of firing light carried
to perfection. His coal is all broken down fine, and lies within easy
reach. His movements are cool and deliberate, no hurry, no fuss. When
he opens the door, his loaded shovel is ready to deposit its cargo
over the spot which a glance shows him to be the thinnest portion of
the fire. On the parts of the run where the most steam is needed, he
fires one shovelful at brief intervals, keeping it up right along. In
this way the steam never feels the cooling effect of fresh fire, for
the contents of the fire-box are kept nearly uniform. This plan is a
near approach to the automatic stoker which mechanical visionaries
predict will effect perfect firing in the vague future. To follow out
such a system requires perseverance and self-denial, but these are well
rewarded to the man whose work is his pride.