PRINCIPLES OF GOOD FIRING
To obtain the maximum amount of heat for the
production of steam, the best method of firing is to limit the amount
of coal put into the firebox at one time, and to fire again only when
the last charge of coal has burned away.
Although steam locomotives appear to work harder
up rising gradients they also travel more slowly, and use little (if
any) more steam in a given period of time, than when working more easily
but travelling faster on easy gradients. This means that because the
demand for steam remains fairly constant all the time the regulator
is open, there is no need to increase the rate of firing to any great
extent when climbing up rising gradients.
Fire sparingly - work systematically. This is
the essence of good firing and has been proved conclusively not only
by tests, but by analysing the way the best firemen work in practice
on the road. No hard and fast rules can be laid down, because locomotives
vary as much as the work they perform and the men who man them. However
for the larger locomotives, the best results are found in practice to
be achieved by not exceeding twelve shovelfuls at one time, and by firing
no more often that is necessary for good combustion. Smaller locomotives
need proportionately less at a time, but the actual rate of firing will
be found by simple observation, for when too many shovels of coal are
being persistently thrown into the firebox, black smoke will result,
and the thickness of the firebed will increase excessively.
For all classes of locomotives the most common
mistake is over-firing. Whether by large amounts of haphazardly fired,
or by small amounts fired too often. Not only is valuable coal wasted
as a result, but the job is also made harder it need be, because combustion
is less efficient.
The preparation of the fire
The fire should be made up in stages and immediately
prior to leaving the depot, should be well burned through and showing
good combustion; the firebars free from clinker and the primary air
passing through quite freely from the ashpan. A careful examination
of the fire should be made when backing on to the train; if there are
any holes or hollow places these should be filled up. The condition
of the fire prior to the start of a journey plays a very important part
in the subsequent performance of the locomotive using any system of
firing. The water level in the boiler should be checked to ensure that
the height shows about three quarters of the glass; this will allow
for additional water to be put into the boiler should the steam pressure
rise so that the safety valves operate. An effort should be made by
the fireman to prevent steam escaping needlessly from the safety valves
as that is waste - waste of coal, water and power. He should keep his
fire under observance to ensure that the boiler pressure is kept as
high as possible without steam escaping from the safety valves and that
there is no dense smoke emitted.
Starting away with the train
On no account should the locomotive be fired
when starting away. When the right away signal is given, the Fireman
should close the firedoor proportionately. At the commencement of a
journey the temperature of the firebed and brick arch are much lower
than they will be at any other stage of the journey, and the object
in not firing the locomotive at this time is to raise the temperature
as quickly as possible and this is done by partly closing the firedoor,
thus making the greater part of the air flow through the firebed. It
has to be remembered that the amount of volatiles being given off by
the fire at this stage is small on account of the low temperature and
it is not necessary to allow a large amount of air through the firedoor.
It must be strongly impressed upon trainees that the practice of firing
when starting away is a bad one, as to do so means that an open firedoor
allows a large amount of secondary air to enter the fire and further
reduces the already low temperature. Further, the addition of coal at
this stage merely cools the fire.
After the train has started it is a good practice
for the Fireman to watch the movements of his Driver and when lie has
notched up the gear, that is, drawn the locomotive up in expansion,
it is time to fire. It has to be remembered that during this period
the temperature in the firebox will have increased and the fire will
almost be incandescent and this is the ideal state for Firing. The Fireman
should now fire where the fire is thinnest and if the fire is being
pulled into holes, these should be filled up smartly and if there are
patches which are not burning properly these should be missed to allow
them to burn.
He should place the coals into the firebox in
that an even firebed is maintained and usually the method of firing
up the sides and behind the door is a good one. He should watch the
chimney and if the fire is in good order there will be in about 5 seconds
after firing a light grey smoke at the chimney top which should disappear
in about two minutes. When the smoke disappears it is a sign that the
volatiles have been consumed and it is time to fire again. Should heavy
black smoke appear at the chimney it means that incomplete combustion
of the fire is taking place and the Fireman should regulate the secondary
air through the firedoor.
Firing on the journey
There is a strong belief among some Firemen that
when a locomotive is climbing or about to climb a heavy gradient, it
is necessary that a greater rate of firing is needed, in fact, in many
cases Firemen begin to fire heavily prior to ascending the incline.
The result is that a heavy black fire is on the firebed, the temperature
and pressure falls and when this happens the Fireman, getting anxious,
adds more coal in excessive quantities and the steam pressure falls.
Locomotives burn more coal per mile when climbing
gradients than when running on the level, but since they ascend the
gradient at a slower speed than that at which they travel on the 1evel,
they have more time in which to burn it. It is a mistake, therefore,
to think that much more coal is required in a given space of time when
travelling up rising gradients, therefore there is no need to increase
the rate of any great extent. The more constant the rate of firing over
the whole run the more efficient the firing, and the less the coal consumption.
It may be necessary to say a few words about
the steam consumption rate. It is difficult to give a direct figure
for the rate actually used, unless the locomotive is suitably equipped
with a steam meter. It is. however, possible to make a calculation of
steam consumption by the method of speed and the percentage cut-off.
The product Speed x Cutoff is proportionate to the amount of steam used
per minute. This, of course, is not strictly correct as a portion of
the steam is used for other purposes, such as steam heating, injectors,
brakes, etc. The following shows the steam consumption rates for various
speeds and cut-offs.
Speed
% Cut off Steam Used
Units
80 M.P.H.
15
1,200
70 M.P.H.
17
1,190
60 M.P.H.
20
1,200
50 M.P.H.
24
1,200
40 M.P.H.
30
1,200
30 M.P.H.
40
1,200
20 M.P.H.
60
1,200
12 M.P.H.
Max.
1,200
These figures show, apart from periods when the
steam is shut off, that steam consumption rates do not vary considerably,
and definitely do not increase on the Up gradient. This is not the opinion
held by certain Firemen who hold that an increased amount of steam is
used on heavy rising gradients and, owing to this, heavy firing must
take place. On tests made this has been disproved and on some of the
graphs produced a decreased steam consumption was shown when ascending
heavy inclines. The explanation of this is that the increase in percentage
cut-off employed on a heavy rising gradient is more than compensated
for by the drop in speed.
No hard and fast rules can be laid down about
the exact amount of coal to be fired, and how often to fire it, because
engines vary as much as the work they perform and the men who man them.
However, for the larger locomotives the best results are found in practice
to be achieved by not exceeding an average of twelve shovelfuls at a
time, and by firing no more often than is necessary for good combustion.
Smaller locomotives need proportionately less at a time.
The fire irons should only be used when absolutely
necessary. If the fire should be caked, the fire-irons should he used
to break it up. If there is a good depth of fire and the ash and clinker
are lifted up and mixed with the red hot fuel then the ash will melt
and run into the spaces between the firebars and so make things worse.
If the fire does clinker, it will be necessary to break it up and this
can he best done by running down the fire, as it will be easier to deal
with.
PROCEDURE FOR THE PREPARATION
OF STEAM LOCOMOTIVES
1. Walk around locomotive to ascertain if any
persons are working on the loco and check for the application of "Not
to be moved" boards or red flags.
Apply a "Not to be moved" board and
chocks (if required) before attemping to prepare locomotive.
2. Enter cab and ensure locomotive is secured,
reversing gear is centred and locked.
3. Test water gauges and/or test cocks (where
fitted).
4. Examine interior of firebox (where possible)
for leakage or distortion including: stays, tubes, fusible plugs, grate,
brick arch etc.
5. Examine accessable areas of boiler for leaks
i.e. Mudhole doors, washout plugs etc.
6. Open smokebox and examine contents for leaks
and check fixtures e.g Spark arrestor etc are fully secured. Check door
seal is correct and close tightly.
7. Raise steam steadily excessive smoke.
8. Check water tank contents.
9. Check coal supply is sufficient, trim to avoid
lumps falling from bunker.
10. Draw tools from stores and examine. Report
any deficiences to Running Foreman or shed staff. Examine detonator
canister seal to ensure it is intact.
11. Oil all relevant motion parts with the correct
grade of oil including couplings, buffer shanks and tender rubbing plates.
Check trimmings are correctly positioned (where possible) and appear
to be working satisfactorily. Whist oiling examine motion/springs for
loose bolts, cracks or distortion or signs of brass or white around
bearings.
12. Drain and refill all axleboxes as required.
13. Fill mechanical lubricators (where fitted)
and hydrostatic lubricators with the correct grades of oil, ensuring
they are not overfilled.
14. Lubricate other accessories as necessary.
i.e Air pumps, generators, brakes cylinders.
15. Drain and refill all axleboxes as required.
16. Refill all oil bootles and cans for supply
of oil during days work.
17. Clean cab and windows.
18. Ckeck all sanboxes and refill as necessary.
Brush off gangways and steps of any sand spillage of dust.
19. Examine couplings, vacuum/air brake and steam
heating pipes for damaged coupling heads and ensure they are secured
on the fastenings provided.
20. Test both injectors and fill boiler. min
3/4 full.
21. Blow down boiler until 1/4 and refill boiler
as required.
22. Allow safety valves to lift once to ensure
they are working correctly.
23. Test loco and automatic brake.
24. Fill tank/tender as required.
25. Ensure head and tail lamps are cleaned, filled,
trimmed and positioned correctly and lit of required.
26. Report any problems to Running Foreman or
shed staff before going "off shed".
