STEAM LOCOMOTIVE ENGINEMAN’S. Manual - part 30

Chapter 13: - General Westinghouse Brake – Questions and Answers 

 

 

NO 4 BRAKE VALVE 
 
Q. 

What would be the result if the pipe to the black hand on 
the gauge or the pipe to the equalising reservoir broke? 

 
A. 

Air would escape from the chamber on top of the equalising 
piston, thus permitting train pipe pressure under the piston to 
force it up, allowing air to escape past the discharge valve 
through the secondary exhaust and causing the brakes to be 
applied. 

Q. 

How should a broken pipe to the gauge be remedied? 

 
A. 

If the pipe is broken between the T-piece and the gauge, 
blank the pipe on the gauge side of the T-piece; this will 
retain pressure in the equalising reservoir and in the 
chamber on the top of the equalising piston and service 
reductions could be made as usual, but the black hand on 
the gauge would not register any pressure. 

 
 

Return to Box Flat and withdraw the locomotive from traffic 
until repair. 

 
Q. 

How should a broken main reservoir pipe  to the gauge 
be remedied? 

 
A. 

Blind joint the pipe at the main reservoir connection. 

 
Q. 

What would be the result if the pipe from the main 
reservoir to the pump governor broke, and how would 
you overcome this defect? 

 
A. 

It would cause leakage of air from the broken pipe and the 
governor would not have control of the pump. 

 
 

Blind joint the pipe at the main reservoir end and control the 
pump with the steam valve.  Return to Box Flat and withdraw 
the locomotive from traffic until repaired. 

 
Q. 

What is the object of the equalising feature of the brake 
valve? 

 
A. 

It prevents the Driver from reducing air direct from the train 
pipe when making service applications of the brake.  The 
equalising feature allows the train pipe pressure to be 
reduced through the secondary exhaust at a uniform rate 
regardless of the length of the train, and the flow of air from 
the train pipe is gradually stopped.  This gives a smoother 
breaking action throughout the train. 

 

Chapter 13: - General Westinghouse Brake – Questions and Answers 

 

 

Q. 

What is the object of equalising reservoir? 

 
A. 

To enlarge the space above the equalising piston so as to 
provide sufficient air on top of the equalising piston, from 
which the Driver is able to draw when making service 
reductions; at the same time, the equalising feature is 
brought about gradually, both in reducing and cutting off the 
escape of train pipe pressure, when making service 
reductions. 

 
Q. 

How should a test be made for a defective equalising 
piston? 

 
A. 

After charging the train pipe to standard pressure of 70 lb, 
place the automatic brake valve handle in the lap position; 
open the train pipe cock on the front of the engine and if the 
black hand on the gauge falls rapidly it indicates that the 
equalising piston is defective. 

 
 

A further test can be made by placing the automatic brake 
valve handle in the service position, and if no discharge from 
the secondary exhaust occurs by the time the equalising 
reservoir pressure drops 5 lb, the piston would be defective, 
after making sure that the train pipe leakage is not 
excessive. 

 
Q. 

How should a test be made  for leakage from the 
equalising reservoir or its connections? 

 
A. 

After charging to standard pressure, make a 5 lb service 
reduction and hold the automatic brake valve handle in the 
lap position.  If air discharges intermittently from the 
secondary exhaust it indicates leakages form the equalising 
reservoir or its connections to the brake valve and gauge. 

 
Q. 

If a continuous discharge of air occurs at the secondary 
exhaust when the brake valve is in the release or 
running position, what would be the cause? 

 
A. 

The discharge valve or its seat damaged, or dirt holding it off 
the seat. 

 
Q. 

When making a service reduction, does the secondary 
exhaust remain open longer on long trains than on short 
trains? 

 
A. 

Yes. 

 

Chapter 13: - General Westinghouse Brake – Questions and Answers 

 

 

Q. 

Why? 

 
A. 

Due to the greater volume of train  pipe pressure below the 
equalising piston having to be got rid of before equalization 
takes place. 

 
Q. 

If for any reason the Driver feels the brakes being 
applied, or the Black Hand on the gauge shows a 
reduction of pressure, what should he do? 

 
A. 

He should immediately place the brake valve handle on lap, 
allow the train to stop and ascertain the cause.  If on a 
passenger train, he should avoid stopping on a bridge or 
tunnel where passengers are likely to alight. 

 
Q. 

How should a test be made for a leaky rotary valve? 

 
A. 

Before starting he pump place the brake valve handle on lap.  
If the Black Hand on the gauge rises or if there is any 
leakage out of the main exhaust it indicates leakage past the 
valve. 

 
Q. 

How should the break be worked with the rotary valve 
leaking? 

 
A. 

Before applying the brake, close the isolating cock; when 
release is required, re-open the isolating cock.  Return to 
Box Flat and withdraw the locomotive from traffic until 
repaired. 

Q. 

How should the train pipe and main reservoir be tested 
for leakages? 

 
A. 

Charge the system to standard pressures, ascertain that the 
rotary valve and equalising piston are in good order, then 
make a 15 lb service reduction, and leave the brake valve on 
lap.  Triples will not be in the lap position.  Close the isolating 
cock and then put the brake valve in full release. 

 
 

If the Black Hand falls quickly it indicates the amount of train 
pipe leakage.  To test the main reservoir for leakages, 
charge to 90 lb, close the steam valve to the pump, and also 
close the isolating cock.  If the red hand on the gauge falls, it 
indicates the amount of leakage. 

 

Chapter 13: - General Westinghouse Brake – Questions and Answers 

 

 

Q. 

What should be done in the event of the following 
failures? 

 
 

(A) 

Broken pipe to equalising reservoir? 

 

(B) 

Broken pipe from main reservoir to pump 
governor? 

 

(C) 

Broken train pipe in front of engine? 

 
A. 
 

  (A) 

Blank the pipe at its connection to the brake 
valve body and plug up the secondary exhaust.  
If a plug cannot be obtained, secure the 
4equalising piston down, closing the secondary 
exhaust. 

 

 

 

To apply the brake, move the brake valve handle 
judiciously towards the emergency position and 
judge by the sound of the escape of air from the 
train pipe, for making light reductions.  Be guided 
by the sound in starting and guard against 
stopping train pipe reductions abruptly. 

 
(B) 

Blank the pipe at the main reservoir connection. 

 
 

This cuts out the governor.  Control the operation 
of the pump with the steam valve, to avoid main 
reservoir pressure rising above 90 lb per spare 
inch. 

 
(C) 

Retrace the broken pipe back to the  first union 
coupling and remove the broken section, 
replacing it with the hose off the front of the 
engine and securing dummy in hose to make it 
airtight.  Failing this, drive a wooden plug tightly 
into the broken pipe, this will avoid a total failure. 

 
 

In all cases the locomotive is to be returned to the Box Flat 
until repaired. 

 
Q. 

What would be the effect of a leak in the auxiliary 
reservoir? 

 
A. 

When the brake is applied, it will cause auxiliary pressure to 
drop below the pressure in the train pipe and the triple valve 
will be moved to release position, allowing that brake to 
release.  When the triple valve is in release position, the leak 
will be fed through the feed groove in the triple piston 
bushing, bringing about conditions equivalent to a train line 
leak.