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.
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 x 24 engine, there is a petticoat-pipe
112 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 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 bang 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
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.
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
The other day an engineer came into the round-house, and said,
"You had better put 32 inch
nozzles in my engine: I think she will get along with that increase
of size." He had been using 34
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 be-longed 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.
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