STEAM LOCOMOTIVE ENGINEMAN’S. Manual - part 20

Chapter 11: - General Engine Questions and Answers

On opening the steam cock, steam passing through these
holes expands and passes up the funnel, causing gases and
air in the smokebox to be discharged. This results in a
partial vacuum being formed in the smokebox, and cause a
draught of air at atmospheric pressure to pass through the
dampers, grates and firebed to destroy the vacuum, this
draug ht makes the fire burn fiercely and give off greater
heat.

The blower should only be used lightly to raise steam and
should not be used when the fire is withdrawn, banked low
or burnt through, as this causes cold air to be drawn into the
firebox and unequal contraction of the boiler plates to occur,
which results in leakage of tubes and stays. If used too
strongly or at the wrong time, the blower becomes an abuse
and will damage the boiler.

The duty of the blower is to create a draught on the fire to
prevent gases in the firebox from entering the cab, and to
start a fresh fire and raise steam pressure gradually. If used
judiciously in conjunction with firing, it will do away with
dense black smoke.

Name the parts in the smoke box of a locomotive.

The smoke box of an engine contains a blast pipe and
nozzle to exhaust the steam to atmosphere after it has done
its work in the cylinders.

Steam pipes to convey the steam to the steam chests;
deflector plates for the purpose of giving a more even flow of
gases through the tubes, a spark arrester to break up
cinders that are drawn in from the firebox, the small mesh
allowing particles of ash to be broken up so finely that they
cannot cause damage.

The Westinghouse pump exhaust pipe, which is connected
to the blast pipe, washout plugs for washing out the barrel;
an ash ejector chute for removal of smokebox ash; a blower
pipe and perforated ring to induce the flow of gases from the
fire door and raise steam gradually.

When should the ashpan water be used?

It should always be turned on before any attempt is made to
open the ashpan slides preparatory to cleaning the fire, and
should be left on fully all the time fire cleaning is in progress.

Chapter 11: - General Engine Questions and Answers

It is essential to flood the ashpan to prevent fine ash dust
from rising and coming into contact with the bearings, and
also to quench all fire de-ashed. Fine ash mixed on oiled
bearing faces causes the latter to wear quickly, resulting in
pounding.

Name the parts of a Sellers injector?

The outside connections to the body of the injector are the
steam supply pipe, water supply pipe, and delivery pipe and
overflow pipe.

The internal parts of the injector include the steam and water
valve, overflow and non-return check valve, and
supplementary water valve. It also contains the lifting
nozzle, forcing nozzle, and combining and delivery tubes.

Refer in FIGURE 9a - b in Annex A.

What are the likely defects of injectors and their
remedies?

The defects likely to occur and the remedies of some are as
follows:

Storage of water in tender.

Tenders should be filled.

Dirty screens in the union hose of the suction
pipe.

−

To be uncoupled and cleaned. Whilst
uncoupled, the overflow valve should be
closed with the cam lever, the water
valve and steam valve opened, and
steam blown back through the
uncoupled suction pipe.

The overflow valve should then be re-
opened, and the water cock on the
tender opened to make sure that a full
supply of water passes through the
uncoupled water pipe. At the same
time, the position of the handle when the
water is flowing full on is noted, the
conical screen is then replaced and the
suction pipe coupled up.

Chapter 11: - General Engine Questions and Answers

A tight lid on the back of the tender may cause
an air lock and hold the water back. If so the lid
of the tender should be lifted.

Steam and clack valves blowing will cause the
injector to overheat, resulting in water flashing
into steam, preventing a vacuum from being
created in the suction pipe.

−

The defective valves should be booked
for attention and meanwhile, the injector
should be cooled down with cold water
to enable it to be operated. Reduced
steam pressure will often assist to work
an injector tending to overheat.

At leakage into the suction pipes will also cause
trouble in correcting a vacuum. In such cases,
loose joints should be tightening up.

How is an injector operated?

To operate the injector it is first ascertained that the tender is
supplied with water and that sufficient steam is available for
the use of the injector. The steam valve to the supply pipe is
fully opened, the water supply valve on the tender is opened,
and it is ascertained that the clack valve stop cock is
opened.

The water regulating valve is then opened, and the steam
valve opened just sufficient to allow a small amount of
steam, passing through the lifting nozzle and through the
body of the injector, to lift the overflow valve and escape at
the overflow pipe.

This creates a vacuum in the body of the injector and suction
pipe. This vacuum, in turn, is destroyed by the action of the
atmospheric pressure acting on the top of the water in the
tender, forcing the water into the body of the injector and out
of the overflow pipe.

When water appears at the overflow pipe, the steam valve
starting lever should be drawn out to the full travel to allow a
full flow of steam to pass through the forcing nozzle. The
steam mixing with the water in the combining and delivery
tubes condenses and forms a solid stream of water, and its
velocity through the delivery pipe is such that it opens the
clack valve and enters the boiler against the boiler pressure.

Chapter 11: - General Engine Questions and Answers

The combining tube is perforated and is surrounded by
water, which is drawn into the combining tube to maintain a
constant stream of water into the boiler when the injector is
operating.

If the clack valve becomes stuck while in the open
position, what action should be taken to remedy the
trouble?

An attempt should be made to close the valve by tapping the
clack box with a piece of wood or by pouring cold water over
it. If this is not successful, the stop cock must be closed and
the clack valve given attention.

What are the principle causes of boilers failing to steam
freely?

Tubes blocked up or dirty, defective brick arch or deflector
plate, leaky wall stays, flanges or tubes; dampers not
properly opened or adjusted, dirty or choked fire, bad firing,
smoke box drawing air at the door, steam pipes, saddle
casting or ash ejector chute; spark arresters blocked up;
blast pipes choked up, out of line or blowi ng through at base;
pump exhaust pipe and blower pipe leaking at connections
inside smokebox; and valves and pistons blowing through
badly.

What are the causes of spark arresters blocking up?

Working with the fire door closed lightly, when the engine is
under heavy steam, uneven feeding of coal to the firebed,
dampers not opening sufficiently; choked blast pipe; working
the fire bars when the engine is under heavy steam or when
the blower is hard on; opening of the regulator full wide at
first pull when running into a rising grade; and the boiler
priming.

If steam pressure falls quickly when the regulator is
opened, what are the principle causes?

Valves and pistons blowing through, steam blowing from the
super heater header, elements, or steam pipe joints.

How may a test be made for steam blows causing bad
steaming?

The brakes should be applied hard on, the smokebox door
opened, the reversing lever placed in the central position
and the regulator opened, all joints in the smokebox are then
examined for leaks.

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