Air brake system of locomotive

1
CONTENTS
History of locomotive workshop
Air brake concept
 Single pipe braking system
 Twin pipe braking system
Loco brake system
 A-9 Automatic brake valve
 SA-9 Independent brake valve
 Relay air valve
 Distributor valve
 Control valve
 Emergency valve

2
NORTHERN RAILWAYS
Brief history of Railways workshop:
The Northern Railways Loco Workshop at Charbagh is a good
example of successful adaptation to change and growth.
The railways came to Lucknow on 23rd April 1867 under the
banner of Indian branch Railways Company. This company was
formed in England in 1862 and have begun construction of the
Lucknow – Kanpur railway line as a light mode meter gauge in 1868
crossing Sai River near Harauni and the Nagwa at Lanka.
Later in 1867 the company obtained a contract to build a full scale
broad gauge system in the area north of the gauges and altered its
tittle to the Oudh and Rohailkhand Railways. The O&RR grew to
have three divisions at Allahabad, Lucknow & Moradabad joining up
with the EIR at Kanpur and Ghaziabad.
The railway’s headquarters were at Lucknow. O & RR realized the
need for good maintenance of rolling stock-locus, carriages and

3
manager Mr.T.A.Waide was in position within 18 months of the
opening of the railways to Lucknow in September 1868.
It seems that the workshop started with almost all its work coming
from Britain. The O & RR however was quick to recognize the
advantages of hiring peasants for certain tasks by 1870. The
Charbagh workshop was successful employing native labour. A large
number of people being brought from Bihar. Till 1950 all the
locomotive remaining in India were imported from Britain for every
20 Locomotive imported in the assembled condition one.
Locomotive was imported in knocked down condition to provide
vital spare parts. The first Locomotive of the O & RR come from M/S
Neilson. Periodic overhaul to a Locomotive means that the entire
Locomotive is stripped down. various components cleaned,
inspected, repaired, replaced & assembled again major components
attended to being the boiler, wheels & the engine .Obviously there
was no industry which could manufacture the consumables
required or provide components broken or damaged in accidents .
These items had to be made in the workshop & therefore POH shops

4
had to have basic engineering facilities of blacksmith, foundry &
machines where iron / steel would be cast formed & otherwise
manipulated to produce components for the all-powerful steam
locomotives. Assets of the O&RR along with the shops at Alambagh
&Charbagh were taken over by EIR in 1925. FIR ration aligned their
locomotive POH workload only shunting and small Locomotive.
POH workshop only were sent to Charbagh main line locomotive
being repaired at the EIR’s premier workshop at Jamalpur a district
of Bihar.
During the Second World War as in the first ammunitions of
war produced in the Charbagh workshop practically hand grenades
workshop administrative office itself was used at armory. There was
a small ordinance factory next to the Charbagh shops when the
ordinance work reduced after the war staffs of the factory were
observed in the workshop in 1946 and later the factory itself along
with its land etc. merged with Railways workshop.
Charbagh shops become a part of Northern Railways in1952
regrouping. This Charbagh workshop did not have any Loco POH

5
shops where its Locos could be comfortable based as Mughalpura,
the famous shops of N/W railways had Already gone to Pakistan &
Jamalpur shops were now with Eastern Railways. A major effort was
therefore mounted to develop CB shops increasing its manufacturing
as well as overhauling capabilities from dealing with shunting
Locomotives to that of locomotive working mainline services.
Manufacturing activities continued & reached its peak in the 1960’s
losing way only in the 1970’s. When industries in the country
developed & steam began to be slowly replaced by Diesel
Locomotives, for which components were bought from trade or
specialized components obtained from U.S.A. or the Diesel
Locomotives works Varanasi.
Fortune of the work underwent an ellipse within the importance of
steam traction as Diesel Loco repaired did not demand the same
amount of labour or in-house manufacture of components. Thus ,
while Diesel Loco overhaul was begin at Charbagh in1975 & that of
Electric Locos in1985, there was as extent job , surplus manpower,
loss of relation importance, also lead to reduced investment for

6
machinery, plant & infrastructure. Not with standing these changes,
Charbagh workshops holds a proud distinction of being the only
workshop in Indian Railways overhauling steam, diesel & electric
locos at the same time for a period of 7 years.
In June 1992, the ministry of Railways decided that all steam loco
repair be discontinued & staff employed on such activities,
redeployed in a period of three months.
It is a matter of pride that targets laid down by the ministry were
met. The country’s lost BG steam Locomotive “YUGANTAR” duly
potted was seen off in September 1992. Success in redeployment of
such a large body of staff in a very short period into other lines of
authorities has given the loco works a measure of pride & self-
esteem besides a feeling of belongingness. Staff now clearly
understands that these
Loco works can survive & prosper only by their own hard work,
commitment & good relations. In the year 1993, the rehabilitation of
BOX wagon was started & closed down in the year 1996 .Charbagh
shops were modified to give POH attention to diesel. Electric

7
Locomotive In 1975 from a beginning of one or two locomotive, 10
Locomotive are now given POH/IOH attention per month CB shops
have POHed. Electric Loco have been over hauled till now.
The Charbagh shop is currently blazing a new trail in understanding
work of diverse nature for Indian Railways by emphasis or
innovation cost effectiveness & above all employee involvement. In
this direction the achievement in manufacturing 1500 ballot boxes
for use in Parliamentary Election 1996 within a short time of one
week is a significant step. The POH of DEMU’s consists of
overhauling, repairing & testing of complete electrical & mechanical
control systems & repair of coach including Passenger amenities. CB
loco shop has POHed DEMU coaches till Jan-2005.
Indian railways previously divided into zonal wise in 9 zones. Now a
days it is further extended up to 16 zones mentioned below. Each
zone is headed by General Manager itself who is fully responsible for
operating staff, technical staff and sheds etc.

8
TARGETTED OUT TURN (POH) PER YEAR:
DIESEL LOCO ELECT. LOCO DEMU LOCO
108.0 15.0 50.0
BASIC DATA OF WORKSHOP:
1. Total area 132 x 1000 square
meter
2. Total covered area 575 x 1000 square
meter
3. Railway line 7.5 Km.
4. Road in shop 4.71 Km.
5. Machine tools installed 720
6. Water storage capacity 5.75 x 1000 liter
7. Consumption average (drinking water) 1.575 x 100000
liter/day
8. Requirement of power/month 272326 KWH
9. Compressed air capacity 7204 CPM

9
ZONAL RAILWAYS:
Indian railways previously divided into zonal wise in 9 zones. Now a
days it is further extended up to 16 zones mentioned below. Each
zone is headed by General Manager itself who is fully responsible for
operating staff, technical staff and sheds etc.
1. Northern Railway
2. Southern Railway
3. Eastern Railway
4. Western Railway
5. Northeast Frontier Railways
6. North Eastern Railway
7. South Eastern Railway
8. South Central Railway
9. Central Railway
10. East Central Railway
11. East Coast
12. North Central

10
13. North Western
14. South Western
15. West Central
16. Bilaspur Zone
This workshop came in the NR zone but the diesel loco, electric loco
and DMU coaches that are coming from other zonal railways and
these are said to be Foreign Railways.
This Loco Work Shop comes under the category of I.S.O.9000
certified because the quality of the P.O.H. and Technical ability of
staff is according to the above standards. This Work Shop is awarded
in 2008-2009 for the best P.O.Hed quality of Electric Loco, Diesel
Loco and D.M.U. coaches also.

11
BRANCH WISE (TECH) WORK GROUP OF LOCO WORKSHOP:
There are 4 branches according to the different types of work, these
are:
1. MECHANICAL BRANCH
2. ELECTRICAL BRANCH
3. ACCOUNTS BRANCH
4. METALLURGICAL BRANCH
5. PERSONAL BRANCH
SUMMARY REPORT:
The summary report related to Diesel/Electric/DMU Coaches covered
in a report is named as DSL_HOLD_OUT .This report shows about
the locos whether they are coming from NR railways or other than
NR railways (which are known as foreign railways).
The outturn, holding, total out-turn during the financial years, last
five years out-turn and targeted out-turn for coming years have also
been shown in this summary report.

12
Points for POH/IOH/SR:
The points required for calculation of casting for each loco has been
shown below:
Repair Category Points
POH 1.0
IOH 0.75
SR 0.25
POH+SR 1.25
IOH+SR 1.0

13
AIR BRAKES
Introduction
The air brake is the standard, fail-safe, train brake used by railways
all over the world. In spite of what you might think, there is no
mystery to it. It is based on the simple physical properties of
compressed air. So here is a simplified description of the air brake
system.
Contents
Basics - The Principal Parts of the Air Brake System - Operation on
Each Vehicle - Release - Application -Lap - Additional Features of
the Air Brake - Emergency Air Brake - Emergency Reservoirs -
Distributors -Two-Pipe Systems - Self-Lapping Brake Valves -
Other Air Operated Systems - Comment - loco brake.
Basics
A moving train contains energy, known as kinetic energy, which
needs to be removed from the train in order to cause it to stop. The
simplest way of doing this is to convert the energy into heat. The
conversion is usually done by applying a contact material to the
rotating wheels or to discs attached to the axles. The material
creates friction and converts the kinetic energy into heat. The

14
wheels slow down and eventually the train stops. The material used
for braking is normally in the form of a block or pad.
The vast majority of the world's trains are equipped with braking
systems which use compressed air as the force to push blocks on
wheels or pads on to discs. These systems are known as "air brakes"
or "pneumatic brakes". The compressed air is transmitted along the
train through a "brake pipe". Changing the level of air pressure in
the pipe causes a change in the state of the brake on each vehicle. It
can apply the brake, release it or hold it "on" after a partial
application. The system is in widespread use throughout the world.
The Principal Parts of the Air Brake System

15
Compressor
The pump which draws air from atmosphere and compresses it for
use on the train. Its principal use is for the air brake system,
although compressed air has a number of other uses on trains.
Main Reservoir
Storage tank for compressed air for braking and other pneumatic
systems.
Driver's Brake Valve
The means by which the driver controls the brake. The brake valve
will have (at least) the following positions: "Release", "Running", "Lap"
and "Application" and "Emergency". There may also be a "Shut
Down" position, which locks the valve out of use.
The "Release" position connects the main reservoir to the brake
pipe. This raises the air pressure in the brake pipe as quickly as
possible to get a rapid release after the driver gets the signal to start
the train.
In the "Running" position, the feed valve is selected. This allows a
slow feed to be maintained into the brake pipe to counteract any
small leaks or losses in the brake pipe, connections and hoses.
"Lap" is used to shut off the connection between the main reservoir
and the brake pipe and to close off the connection to atmosphere
after a brake application has been made. It can only be used to

16
provide a partial application. A partial release is not possible with
the common forms of air brake, particularly those used on US freight
trains.
"Application" closes off the connection from the main reservoir and
opens the brake pipe to atmosphere. The brake pipe pressure is
reduced as air escapes. The driver (and any observer in the know)
can often hear the air escaping.
Most vehicles brake valves were fitted with an "Emergency"
position. Its operation is the same as the "Application" position,
except that the opening to atmosphere is larger to give a quicker
application.
Feed Valve
To ensure that brake pipe pressure remains at the required level, a
feed valve is connected between the main reservoir and the brake
pipe when the "Running" position is selected. This valve is set to a
specific operating pressure. Different railways use different
pressures but they generally range between 65 and 90 psi (4.5 to 6.2
bar).
Equalizing Reservoir
This is a small pilot reservoir used to help the driver select the right
pressure in the brake pipe when making an application. When an
application is made, moving the brake valve handle to the

17
application position does not discharge the brake pipe directly, it lets
air out of the equalizing reservoir. The equalizing reservoir is
connected to a relay valve (called the "equalizing discharge valve"
and not shown in my diagram) which detects the drop in pressure
and automatically lets air escape from the brake pipe until the
pressure in the pipe is the same as that in the equalizing reservoir.
The equalizing reservoir overcomes the difficulties which can result
from a long brake pipe. A long pipe will mean that small changes in
pressure selected by the driver to get a low rate of braking will not
be seen on his gauge until the change in pressure has stabilized
along the whole train. The equalizing reservoir and associated relay
valve allows driver to select a brake pipe pressure without having to
wait for the actual pressure to settle down along a long brake pipe
before he gets an accurate reading.
Brake Pipe
The pipe running the length of the train, which transmits the
variations in pressure required to control the brake on each
vehicle. It is connected between vehicles by flexible hoses, which
can be uncoupled to allow vehicles to be separated. The use of the
air system makes the brake "fail safe", i.e. loss of air in the brake pipe
will cause the brake to apply. Brake pipe pressure loss can be
through a number of causes as follows:
1. A controlled reduction of pressure by the driver

18
2. A rapid reduction by the driver using the emergency position
on his brake valve
3. A rapid reduction by the conductor (guard) who has an
emergency valve at his position
4. A rapid reduction by passengers (on some railways) using an
emergency system to open a valve
5. A rapid reduction through a burst pipe or hose
6. A rapid reduction when the hoses part as a result of the train
becoming parted or derailed.
Angle Cocks
At the ends of each vehicle, "angle cocks" are provided to allow the
ends of the brake pipe hoses to be sealed when the vehicle is
uncoupled. The cocks prevent the air being lost from the brake pipe.
Coupled Hoses
The brake pipe is carried between adjacent vehicles through flexible
hoses. The hoses can be sealed at the outer ends of the train by
closing the angle cocks.
Brake Cylinder
Each vehicle has at least one brake cylinder. Sometimes two or more
are provided. The movement of the piston contained inside the
cylinder operates the brakes through links called "rigging". The
rigging applies the blocks to the wheels. Some modern systems use

19
disc brakes. The piston inside the brake cylinder moves in
accordance with the change in air pressure in the cylinder.
Auxiliary Reservoir
The operation of the air brake on each vehicle relies on the
difference in pressure between one side of the triple valve piston and
the other. In order to ensure there is always a source of air available
to operate the brake, an "auxiliary reservoir" is connected to one side
of the piston by way of the triple valve. The flow of air into and out
of the auxiliary reservoir is controlled by the triple valve.
Brake Block
This is the friction material which is pressed against the surface of
the wheel tread by the upward movement of the brake cylinder
piston. Often made of cast iron or some composition material, brake
blocks are the main source of wear in the brake system and require
regular inspection to see that they are changed when required.
Many modern braking systems use air operated disc brakes. These
operate to the same principles as those used on road vehicles.
Brake Rigging
This is the system by which the movement of the brake cylinder
piston transmits pressure to the brake blocks on each wheel. Rigging
can often be complex, especially under a passenger car with two
blocks to each wheel, making a total of sixteen. Rigging requires

20
careful adjustment to ensure all the blocks operated from one
cylinder provide an even rate of application to each wheel. If you
change one block, you have to check and adjust all the blocks on that
axle.
Triple Valve
The operation of the brake on each vehicle is controlled by the "triple
valve", so called because it originally comprised three valves - a
"slide valve", incorporating a "graduating valve" and a "regulating
valve". It also has functions - to release the brake, to apply it and to
hold it at the current level of application. The triple valve contains a
slide valve which detects changes in the brake pipe pressure and
rearranges the connections inside the valve accordingly. It either:
1. recharges the auxiliary reservoir and opens the brake cylinder
exhaust,
2. closes the brake cylinder exhaust and allows the auxiliary
reservoir air to feed into the brake cylinder
3. Hold the air pressures in the auxiliary reservoir and brake
cylinder at the current level.
The triple valve is now usually replaced by a distributor - a more
sophisticated version with built-in refinements like graduated
release.

21
OPERATION ON EACH VEHICLE
Brake Release
This diagram shows the condition of the brake cylinder, triple valve
and auxiliary reservoir in the brake release position.
The driver has placed the brake valve in the "Release"
position. Pressure in the brake pipe is rising and enters the triple
valve on each car, pushing the slide valve provided inside the triple
valve to the left. The movement of the slide valve allows a "feed
groove" above it to open between the brake pipe and the auxiliary
reservoir, and another connection below it to open between the
brake cylinder and an exhaust port. The feed groove allows brake
pipe air pressure to enter the auxiliary reservoir and it will recharge

22
it until its pressure is the same as that in the brake pipe. At the same
time, the connection at the bottom of the slide valve will allow any
air pressure in the brake cylinder to escape through the exhaust port
to atmosphere. As the air escapes, the spring in the cylinder will
push the piston back and cause the brake blocks to be removed from
contact with the wheels. The train brakes are now released and the
auxiliary reservoirs are being replenished ready for another brake
application.
Brake Application
This diagram (left) shows the condition of the brake cylinder, triple
valve and auxiliary reservoir in the brake application position.
The driver has placed the brake valve in the "Application"
position. This causes air pressure in the brake pipe to escape. The
loss of pressure is detected by the slide valve in the triple
valve. Because the pressure on one side (the brake pipe side) of the

23
valve has fallen, the auxiliary reservoir pressure on the other side
has pushed the valve (towards the right) so that the feed groove over
the valve is closed. The connection between the brake cylinder and
the exhaust underneath the slide valve has also been closed. At the
same time a connection between the auxiliary reservoir and the
brake cylinder has been opened. Auxiliary reservoir air now feeds
through into the brake cylinder. The air pressure forces the piston to
move against the spring pressure and causes the brake blocks to be
applied to the wheels. Air will continue to pass from the auxiliary
reservoir to the brake cylinder until the pressure in both is
equal. This is the maximum pressure the brake cylinder will obtain
and is equivalent to a full application. To get a full application with
a reasonable volume of air, the volume of the brake cylinder is
usually about 40% of that of the auxiliary reservoir.
Lap
The purpose of the "Lap" position is to allow the brake rate to be held
constant after a partial application has been made.

24
When the driver places the brake valve in the "Lap" position while
air is escaping from the brake pipe, the escape is suspended. The
brake pipe pressure stops falling. In each triple valve, the suspension
of this loss of brake pipe pressure is detected by the slide valve
because the auxiliary pressure on the opposite side continues to fall
while the brake pipe pressure stops falling. The slide valve therefore
moves towards the auxiliary reservoir until the connection to the
brake cylinder is closed off. The slide valve is now half-way between
its application and release positions and the air pressures are now is
a state of balance between the auxiliary reservoir and the brake
pipe. The brake cylinder is held constant while the port connection
in the triple valve remains closed. The brake is "lapped".
Lap does not work after a release has been initiated. Once the brake
valve has been placed in the "Release" position, the slide valves will
all be moved to enable the recharge of the auxiliary
reservoirs. Another application should not be made until sufficient

25
time has been allowed for this recharge. The length of time will
depend on the amount of air used for the previous application and
the length of the train.
Additional Features of the Air Brake
What we have seen so far is the basics of the air brake system. Over
the 130 years since its invention, there have been a number of
improvements as described below.
Emergency Air Brake
Most air brake systems have an "Emergency" position on the driver's
brake valve. This position dumps the brake pipe air
quickly. Although the maximum amount of air which can be
obtained in the brake cylinders does not vary on a standard air brake
system, the rate of application is faster in "Emergency". Some triple
valves are fitted with sensor valves which detect a sudden drop in
brake pipe pressure and then locally drop brake pipe pressure. This
has the effect of speeding up the drop in pressure along the train - it
increases the "propagation rate".
Emergency Reservoirs
Some air brake systems use emergency reservoirs. These are
provided on each car like the auxiliary reservoir and are recharged
from the brake pipe in a similar way. However, they are only used
in an emergency, usually being triggered by the triple valve sensing

26
a sudden drop in brake pipe pressure. A special version of the triple
valve (a distributor) is required for cars fitted with emergency
reservoirs.
Distributors
A distributor performs the same function as the triple valve, it's just a
more sophisticated version. Distributors have the ability to connect
an emergency reservoir to the brake system on the vehicle and to
recharge it. Distributors may also have a partial release facility,
something not usually available with triple valves.
A modern distributor will have:
 a quick service feature - where a small chamber inside the
distributor is used to accept brake pipe air to assist in the
transmission of pressure reduction down the train
 a reapplication feature - allowing the brake to be quickly re-
applied after a partial release
 a graduated release feature - allowing a partial release
followed by a holding of the lower application rate
 a connection for a variable load valve - allowing brake
cylinder pressure to adjust to the weight of the vehicle
 chokes (which can be changed) to allow variations in brake
application and release times
 an in shot feature - to give an initial quick application to get
the blocks on the wheels
 brake cylinder pressure limiting
 auxiliary reservoir overcharging prevention.

27
All of these features are achieved with no electrical control. The
control systems comprise diaphragms and springs arranged in a
series of complex valves and passages within the steel valve
block. Distributors with all these features will normally be provided
on passenger trains or specialist high-speed freight vehicles.
Two Pipe Systems
A problem with the design of the standard air brake is that it is
possible to use up the air in the auxiliary reservoir more quickly
than the brake pipe can recharge it. Many runaways have resulted
from overuse of the air brake so that no auxiliary reservoir air is
available for the much needed last application. The problem can be
overcome with a two-pipe system as shown in the simplified
diagram below.

28
The second pipe of the two-pipe system is the main reservoir
pipe. This is simply a supply pipe running the length of the train
which is fed from the compressor and main reservoir. It performs
no control function but it is used to overcome the problem of critical
loss of pressure in the auxiliary reservoirs on each car. A connecting
pipe, with a one-way valve, is provided between the main reservoir
pipe and the auxiliary reservoir. The one-way valve allows air from
the main reservoir pipe to top up the auxiliary reservoir. The one-
way feature of the valve prevents a loss of auxiliary reservoir air if
the main reservoir pressure is lost.
Another advantage of the two-pipe system is its ability to provide a
quick release. Because the recharging of the auxiliaries is done by
the main reservoir pipe, the brake pipe pressure increase which

29
signals a brake release is used just to trigger the brake release on
each car, instead of having to supply the auxiliaries as well.
Two pipe systems have distributors in place of triple valves. One
feature of the distributor is that it is designed to restrict the brake
cylinder pressure so that, while enough air is available to provide a
full brake application, there isn't so much that the brake cylinder
pressure causes the blocks to lock the wheels and cause a skid. This
is an essential feature if the auxiliary reservoir is being topped up
with main reservoir air, which is usually kept at a higher pressure
than brake pipe air.
Needless to say, fitting a second pipe to every railway vehicle is an
expensive business so it is always the aim of the brake equipment
designer to allow backward compatibility - in much the same way as
new computer programs are usually compatible with older
versions. Most vehicles fitted with distributors or two-pipe systems
can be operated in trains with simple one-pipe systems and triple
valves, subject to the correct set-up during train formation.
Self Lapping Brake Valves
Self lapping is the name given to a brake controller which is position
sensitive, i.e. the amount of application depends on the position of
the brake valve handle between full release and full application. The
closer the brake handle is to full application, the greater the
application achieved on the train. The brake valve is fitted with a

30
pressure sensitive valve which allows a reduction in brake pipe
pressure according to the position of the brake valve handle selected
by the driver. This type of brake control is popular on passenger
locomotives.
Other Air Operated Equipment
On an air brake train, the compressed air supply is used to provide
power for certain other functions besides braking. These include
door operation, whistles/horns, traction equipment, pantograph
operation and rail sanders.
Comment
The air brake system is undoubtedly one of the most enduring
features of railway technology. It has lasted from its initial
introduction in 1869 to the present day and in some places, still
hardly different from its Victorian origins. There have been many
improvements over the years but the skill required to control any
train fitted with pure pneumatic brake control is still only acquired
with long hours of practice and care at every stage of the
operation. It is often said that whilst it is easy to start a train, it can
be very difficult to stop it.

31
LOCO BRAKE SYSTEM
Introduction
Loco brake system is provided to stop the Locomotive, whenever it
runs as light engine. It is purely compressed air brake system known
as independent brake system. For this separate air circuit is provided
in 28LAV-1 & IRAB-1 Brake system which is independent to other

32
air circuit. SA9 Independent brake valve is provided in driving
control stand for application & release of loco brake. Valve has three
positions i.e. Quick release, release and application.
Purpose of this system
Independent Brake System is designed to apply and release brake on
locomotive. When locomotive is moving itself Independent Brake is
applied. This system is introduced to run air brake train. Air Brake
system can sustain better brake power and can haul a long train.
System is designed for Locomotive brake application during train
brake application through A9 handle. This is known as
synchronising brake system also.
Loco brake valves
SystemconsistsSA9 Independent Brake valve, Double check valve and
C2-Relay valve.
Description of loco brake system
The SA9 Valve handle is kept normally in release position (right
side). MR air is always available at port no.30 of SA9 valve. When
handle is brought in application potion (left side) than SA9 port 30
connects port 20 and starts supplying pilot air to C2- Relay air valve.
The pilot air passes through MU2B Valve port no. 2&20 and inters to
C2-Relay at port no.2. See the line diagram of loco brake system. The
pilot air pressure depends upon the handle position, at maximum it

33
is 3.5kg/cm2. The C2-relay air valve actuates after getting pilot air
and connects MR pressure to brake cylinders of locomotive through
port no.1&3. The brake cylinder pressure depends upon pilot air
pressure, supplied into C2-Relay chamber through port no.2. For full
brake application SA9 handle is moved to maximum travel position.
In this way independent brake/loco brake is applied. There is a gauge
line taken from front truck of locomotive to driver’s cabin control
stand for indicating brake cylinder pressure. When SA9 handle is
placed in release position, loco brakes are released. How MR air is
reduced to 3.5kg/cm2 see internal function of the SA9 valve & C2-
Relay valve. SA9 Brake valve handle is normally kept in release
position. Loco brake can be applied through SA9 Valve handle. It can
be applied any desired pressure between the minimum and
maximum. This pressure will be automatically maintained in the
locomotive brake cylinders against normal leakage from them. The
locomotive brake can be graduated on and off with either the
automatic (A9) or the independent brake valves (SA9). It is always
possible to release the locomotive brakes with the SA9 valve.
Brake Pipe System
Introduction
BP system is introduced to run Air Brake train, where train brake is
controlled through BP pipe instead of vacuum pipe. Additional C2-

34
Relay valve is introduced in this system to supply sufficient air to BP
system.
BP system valves
BP system consist A9 Automatic brake valve, MU2B valve, Add. /C2-
Relay valve, Air flow measuring valve, R-6 Relay air valve and Air
flow indicator.
Description of BP system
MR air is connected to A9valve at port 30 and Add. /C2-Relay valve
at port 1. Normally A9 handle is kept at release position and
maintains 5kg/cm2-air pressure in brake pipe. In this position
brakes are found released position. When A9handle is moved to
application zone, B P pressure drops through Add. C2-Relay valve,
port 3 is connected to exhaust. In this condition brakes are applied.
Brake release When A9 handle is moved to release position, Add.
C2-Relay valve port3 is connected to port1 and B P pipe is charged
to 5kg/ cm2 and brakes are released.
Feed pipe system
Introduction
Air Brake system has two brake pipes, BP pipe and FP pipe.

35
BP Pipe is provided for brake application and release whereas FP Pipe
is provided to help in release time.
FP system valves
System consist Feed valve and Duplex check valve, which are
connected from MR-1.
Purpose of the system
Feed Pipe system is introduced to reduce the release time after brake
application in air brake trains.
Description of the system
FP System is charged 6kg/cm2 through MR pipe and Feed valve. Air
flows from MR-1 to Duplex check valve, which allows air to outlet
when MR pressure becomes more than 5kg/cm2. Air reaches directly
to feed valve through cut-out cock. Feed valve supply air to feed pipe
at 6kg/cm2. How Feed valve reduces the MR pressure to 6kg/cm2 see
the internal function of the valve.
A-9 Automatic Brake Valve
The A-9 Automatic Brake Valve is a compact self-lapping, pressure
maintaining Brake Valve which is capable of graduating the
application or release of locomotive and train brakes. A-9 Automatic
Brake Valve has five positions: Release, minimum Reduction, Full
Service, Over Reduction and Emergency.

36
Objective
The A9 Automatic Brake Valve maintains 5kg/cm2-air pressure in
Brake Pipe System against normal leakage at its release position. It
also maintains air pressure drop in the system according to its
handle position.
Construction
The A-9 Automatic Brake valve consists of a self-lapping regulating
portion, which supplies or exhausts the brake pipe pressure, and a
vent valve which is actuated only when the brake valve handle is
placed in Emergency position for the purpose of venting brake pipe
pressure at an emergency rate. The self-lapping portion is actuated
by regulating cam dog 3 on the brake valve handle shaft 32 which
controls the supply or exhaust of brake pipe pressure. The vent valve
19 is actuated by special cam dog 23 attached to the brake valve
handle which is operative only in Emergency position of the brake
valve handle.

37
The A-9 Automatic Brake Valve is provided an adjusting handle or
set screw 15 which serves to permit the proper adjustment of the
automatic brake valve to supply brake pipe air to the required
operating pressure. There is an inlet valve assembly along with
double ball check valve, which moves up and down, when handle
moves.
Operation
Charging
The A9 automatic brake valve handle is kept at release position
normally. The regulating cam dog 3 holds the inlet and exhaust unit
at farthest down ward position. While the regulating valve spring 12
will cause the double ball check assembly 5 to be seated at the
exhaust valve and unseated at the inlet valve (see diagrammatic).
Main reservoir air is supplied at port No. 30 in the pipe bracket and
passes through a strainer to the open inlet valve in to port No.5. This
air in port 5 is also ported through a choke passage to the face of
regulating valve diaphragm 9. When the pressure on the face of the
regulating valve diaphragm 9 overcomes regulating valve spring 12
tension, the regulating valve diaphragm assembly moves down ward
and allow the inlet valve spring to seat the double ball check
assembly at the inlet valve seat. The A-9 Automatic Valve resumes a
lap position.
Application

38
When the brake valve handle is moved into the minimum reduction,
service application zone or full service position, the regulating cam
dog 3 on the brake valve handle shaft 32 will permit the inlet valve
assembly to move away from the exhaust port by the exhaust valve
spring 7. The inlet valve assembly will carry the double ball check
assembly with it. This movement will unseat the double ball check
valve at exhaust valve seat, thus allowing brake pipe air to flow to
exhaust. With the reduction of pressure on regulating valve
diaphragm 9, the regulating valve spring 12 will cause a movement
of the diaphragm assembly toward the inlet valve and the double
ball check valve assembly will be seated at the exhaust valve seat
again. The brake valve is to assume a lap position.
Pressure drop in-
Minimum reduction-----.5/.7kg/cm2
Full service-------------1.7/2kg/cm2
Over-reduction---------2.5kg/cm2
Release after application
Movement of the brake valve handle toward release position will
cause regulating cam 3 to move the inlet valve assembly toward the
regulating valve diaphragm assembly. This movement will cause the
double ball check valve 5 to be unseated at the inlet valve. Main
reservoir air will then flow through the inlet valve to port No. 5. The

39
supply of main reservoir air to the face of regulating valve
diaphragm 9 will increase and move down word, resulting in the
compression of the regulating valve spring 12. When the force have
equalized across the regulating valve diaphragm 9, the double ball
check assembly 5 will again seat at the inlet valve due to the force of
the inlet valve spring and the brake valve will assume a lap position.
Thus it can be seen that the brakes can be graduated off in
proportion to the brake valve handle movement from an application
position toward release position.
Emergency position
When the brake valve handle is moved to emergency position, the
brake valve will perform all the service operations. In the emergency
position, the emergency cam dog 23 is actuated through special cam
dog 23 to open vent valve 19 and allow brake pipe air to be vented
at an emergency rate. Release after an emergency is the same as
previously described under release after service.
SA-9 Independent Brake Valve
SA-9 Independent Brake Valve is a compact self-lapping, pressure
maintaining Brake Valve which is capable of graduating the
application or release of Locomotive Air Brakes independent of
Automatic Brake. The SA-9 Independent Brake Valve is also capable
of releasing an automatic brake application on the Locomotive

40
without affecting the train brake application. The SA-9 Brake Valve
has three positions: quick release, release and application.
Objective
The SA9 Independent Brake Valve maintains 3.5kg/cm2-air pressure
in the independent brake system against normal leakage through
C2-Relay valve. It is supposed to maintain graduated application and
release according to its handle position.
Construction
The SA9 Independent Brake Valve consists of a self–lapping
regulating portion, which supplies or exhausts air pressure for
piloting the graduated application or release of brake cylinder
pressure on the locomotive. This brake valve also includes a quick
release valve. Both the self-lapping regulating portion and quick
release valves of the SA9 Independent Brake valve is actuated by
cams attached to the brake valve handle stem. It has regulating valve
spring 12, which regulates supply pressure. Exhaust valve spring 7
regulates the movement of exhaust valve. Inlet valve spring keeps

41
inlet ball valve at seat. Quick release valve 17 keeps port no.1&7
separate through its rubber ` o’ rings.
Operation
Charging
In the release position of the brake valve handle, the inlet valve, due
to the spring tension of exhaust valve Sparing 7, is positioned at its
farthest travel from the regulating valve diaphragm assembly.
Which will unseat the double ball check valve at the exhaust valve
while being seated at the inlet valve by the inlet valve spring. With
the exhaust valve open, there is no air pressure in the independent
application port no. 20. Main reservoir air is supplied through port
30 in the pipe bracket and a strainer to the spring chamber of the
inlet valve where it is blanked. Vacuum pressure in the vacuum
brake pipe is supplied through port No. 1 in the pipe bracket to the
spring chamber of the quick release valve where it is blanked.
Vacuum reservoir pressure coming from the control valve is
supplied through port No. 7 in the pipe bracket and is also blanked
to the position of release valve 17.
Application
When the brake valve handle is moved in to the application zone,
the regulating cam dog 3 on the brake valve handle shaft 24 forces
the inlet valve assembly towards the regulating valve diaphragm
assembly and causes the double ball check valve to seat at the

42
exhaust port and open at the inlet valve, thus supplying main
reservoir air through the open inlet valve in to the independent
application and release pipe (Port 20) which will pilot the
locomotive brake application. Main reservoir air is also ported
through a choke passage to the face of the regulating valve
diaphragm 9. When the pressure on the face of the regulating valve
diaphragm 9 overcomes the force exerted by the regulating valve
spring 12, the regulating valve diaphragm assembly will move down
word. This will allow the inlet valve spring to move the double ball
check assembly to the inlet valve seat, thus the brake valve will
assume a lap position.
Release after application
When the independent brake valve handle is moved toward release
position, the regulating cam dog 3 allows to move the inlet valve
assembly up word, carrying the double ball check valve assembly
with it, thus unseating the exhaust port while inlet valve remaining
seated at the inlet valve seat. A graduated release of brake cylinder
pressure will be there, in proportion to the movement of the brake
valve handle. At the same time, pressure will be released from top of
the diaphragm. When the forces across the regulating valve
diaphragm 9 have equalized, the double ball check valve assembly
will be seated at both the inlet and exhaust valve seats, and thus the
independent brake valve will again assume a lap position.

43
Quick release position
The quick release position of the independent brake valve provides a
means of releasing an automatic brake application on the locomotive
without affecting the automatic brake application present on the
train brakes. When the independent brake valve handle is placed in
the quick release position, the release valve cam 19 positions the
release spool valve 17 to connect vacuum control reservoir port 7 to
vacuum brake pipe port 1. Since the automatic brake application is
in effect on the train, the vacuum pressure in the vacuum control
reservoir will be greater than that of vacuum brake pipe, thus the
vacuum control reservoir will be Permitted to equalize with the
vacuum brake pipe. This will cause the proportionate brake valve to
assume a release position and subsequently cause the release of the
brake cylinder pressure on the locomotive. The equalizing of the
vacuum control reservoir and vacuum brake pipe will have no effect
on the VA1–B control valve, thus the vacuum train brakes will
remain applied.
F-1 Selector Valve
The F-1 Selector Valve performs the function of commanding the
brake equipment on the locomotive to lead or trail position of the
adjacent locomotive and ensures operation of brakes in the trail
locomotives when initiated from the lead locomotive.

44
C2W Relay Air Valve
The C2W Relay Air Valve is a diaphragm cooperated self-lapping
valve having higher capacity which is used as a remote controlled
pneumatic device to relay a large quantity of main air reservoir
pressure to the operating system for brake application.

45
The C-2 Relay Valve is a diaphragm operated, self-lapping valve
which functions to supply and exhaust brake cylinder air pressure
during brake applications and release.
Objective
The C2-Relay valve maintains 3.5kg/cm2-air pressure in locomotive
brake system against normal leakage.
Operation
Application
While supply air pressure present in port 1 and no air pressure
present on control diaphragm 36, both supply valve 6 and exhaust
valve 23 will be seated by the respective springs. Assume that air
pressure is admitted to the control port 2 of the valve. This pressure
will be delivered to the upper side of diaphragm 36 causing it to
move downward, carrying diaphragm stem 20 with it. During this
movement, the diaphragm stem will contact the differential type
supply valve 6 and unseat it by compressing supply valve spring 5.
Supply air from port 1 will then flow past the unseated valve to the
delivery port 3 where it is piped to the brake cylinders. Supply air
also flows through a choke in the exhaust valve to the underside of
the control diaphragm 36.
When the pressure under the diaphragm is substantially equal to the
control pressure on top of the diaphragm, the diaphragm assembly

46
will move back toward its initial position, and supply valve 6 will
seal, aided by spring 5 , thus cutting off further flow of supply air to
the delivery port.
The relay valve will maintain this delivery pressure against leakage.
In the case of a reduction in delivery pressure, the high pressure on
the upper side of diaphragm 36 will cause movement downward,
repeating the application cycle and restoring the delivery pressure to
the desired valve.
Release
When the control pressure to the valve is reduced, the high pressure
on the underside of diaphragm 36 will cause it to move upward,
carrying stem 20 with it. During this movement, the shoulder on the
diaphragm stem will contact differential type exhaust valve 23 and
unseat it by compression of spring 27. Air from the delivery port will
then flow past unseated exhaust valve 23 to atmosphere, reducing
the pressure in the brake cylinders. When the pressure has been
reduced to balance the pressure in the diaphragm, the diaphragm
assembly will move back to its initial position and exhaust valve 23
will seal, aided by spring 27, thus cutting off the flow of brake
cylinder air to exhaust. If the control pressure is completely removed
from diaphragm 36, the valve will completely exhaust the delivery
pressure to the brake cylinders.

47
MU-2B valve
The MU-2B Valve is a manually operated, two position and multi-
ported valve arranged with a pipe bracket and is normally used for
locomotive brake equipment for multiple unit service between
locomotives equipped with similar system in conjunction with F-1
Selector Valve. The MU- 2B valve is a two-position valve with a pipe
bracket. It is used in multiple unit service. The MU-2B valve pilots
the F-1 selector valve. It is a device that enables equipment of one
locomotive to be controlled by equipment of another. It also controls
the movement of the VA1 release valve. The two positions used in the
MU-2B valve is "LEAD" and "TRAIL or DEAD."
Objective
This valve is provided to work in multiunit operation. In trail unit
brake application valves are isolated through this valve.
Construction
MU2B Valve has two positions, which works as a spool valve. It has
number of port connections.

48
Operation
In "LEAD" position, main reservoir air piped to port 63 is connected
to port 53 and thus to the double check valve that leads to the piston
of the VA–1 release valve.
Independent brake control pressure is connected to port 2 &20 of
the MU– 2B valve. Port 13 and port 3 are connected as a means of
providing the passage to charge the brake pipe from the automatic
brake valve. Port 30 connected to the F1 selector valve provides the
connection for a supply of MR air that positions the F1 selector valve
when the locomotive is used as a trailing unit.
When the unit is used as a trail locomotive, the MU-2B valve is
positioned in "TRAIL or DEAD" position. Ports 2, 3, and 20 are
blanked at the MU-2B valve. Port 53 is connected to exhaust at the
MU- 2B valve. Main reservoir piped to port 63 is connected to port
30, which in turn, positions the F-1 selector valve of trail position
operation. At the F- 1 selector valve, brake cylinder equalizing pipe
air, port 14, is connected to ports 16 and 20, both of which are
connected through a double check valve and thus to the control port
of the relay valve. This provides a passage for air emanating from the
lead unit during a brake application.
C3W Distributor Valve

49
C3W Distributor Valve is a graduated release UIC approved
Distributor Valve for application in the Coach Brake System used for
initiating the brake application. These valves are supplied in
Aluminium version as well as Cast Iron version as far as Body, Top
covers and Bottom Covers are concerned.
VA-1B Control Valve
The VA-1B Control Valve proportions the amount of vacuum in the
vacuum brake pipe to the air pressure in the compressed air brake
pipe on the locomotive and acts as a pilot valve to operate the train
vacuum brake, thus securing an application simultaneously with,
and in proportion to the locomotive air brake application.

50
Objective
VA1B control valve is deployed in vacuum brake system to apply and
release the train brake.
Construction
The control valve has three portions. Top cover, valve body and
bottom cover with protection valve. The valve body contains sleeve,
control valve 6, contacted on its upper side through its upper pusher
pin 7 to small diaphragm 8 through diaphragm follower 9. It is also
contacted on its bottom side through lower pusher pin 19 to large
diaphragm 21 through diaphragm follower 22. The VA1B Control
valve has six pipe connections (see piping diagram).
3 – Brake Pipe pressure
6 – Vacuum train pipe
2 --Vacuum train pipe
1 – Vacuum Control pipe
7 – Vacuum Reservoir Pipe to exhauster

51
8 – Atmosphere through GD-80 filter
Top diaphragm makes two chambers, chamber A is connected to B P
pressure 5kg/cm2 through port 3 and chamber B is connected to
atmosphere through a breather port. Bottom diaphragm makes two
chambers, chamber C is connected to vacuum train pipe through
port2 and chamber D is connected to vacuum control pressure
1.7kg/cm2 through port1.
Operation
The VA1B control valve is actuated through A9 valve. The deferent
positions of A9 is described below.
Release
When 5kg/cm2 pressure is available in chamber A, 56cm vacuum in
chamber C, and 1.7kg/cm2 pressure in chamber D, the valve
remains in balanced or lapped position and all the ports are closed.
Suppose there has been a brake application, in chamber a pressure
will drop and in chamber C vacuum will drop. When the A9 valve
handle is moved in release position the brake pipe pressure starts
increasing, the pressure in chamber A also increases, the control
valve moves down connecting port 7 to port 6. In this way the
exhauster starts creating vacuum in the train pipe. As the vacuum is
restored in the vacuum train pipe and in chamber C of the control
valve, the 1.7kg/cm2 pressure supplied to chamber D moves the
diaphragm 20 and valve 6 upward.

52
When the vacuum in chamber C is increased to approximately 56cm
the upward movement of the valve 6 will lap itself leaving only
enough opening to permit the exhauster to maintain vacuum against
leakage in the train pipe.
Application
When the vacuum is restored in the vacuum brake system and it is
desired to apply the brakes, the brake valve handle is moved to
application position, causing a reduction in brake pipe pressure. As
chamber A of the VA1B Control Valve is connected to the brake pipe,
a reduction in pressure in this chamber also takes place. The
1.7kg/cm2 pressure in chamber D then moves the diaphragm
follower and control valve upward as the brake pipe pressure is
reduced. The control valve connects pipe 6 and chamber C to
atmospheric port 8. Thus, atmospheric air pressure enters the
vacuum train pipe. Thereby the vacuum brakes are applied on train.
The pipe connection no. 2 between chamber C and pipe 6 allows
drop in vacuum in chamber C through a choke also and the valve
comes to lap position. The constant braking force is maintained
against normal leakage. It is understood that two pressure i.e. brake
pipe and vacuum are varying and for different combination of these
two forces the valve gets lapped position giving different braking
forces.

53
D-1 Emergency Brake Valve
The D-1 Emergency Brake Valve is a manually operated device
which provides a means of initiating an emergency brake
application.
When it is desired to make the shortest possible stop, the brake valve
handle is moved to Emergency position, causing an emergency rate
of brake pipe reduction. The HS4 control air valve also contains
provision for reducing any excess pressure in the delivery pipe, as
when the pressure called for by the setting of adjusting handle 15 is
lowered. Excess pressure in the chamber above diaphragm 11 moves
the diaphragm and exhaust valve seat 10 downward away from
exhaust valve 5b, The excess air pressure then flows past the
unseated exhaust valve 5b, through the exhaust valve spring
chamber and the diaphragm spring chamber and out to atmosphere
through the opening in the bottom cover.
J-1 Safety Valve

54
The J-1 Safety Valve installed vertically in the main reservoir system
vents pressure at a predetermined setting to atmosphere in order to
prevent excessive main reservoir pressure build up.
D-1 Automatic Drain Valve
The D-1 Automatic Drain Valve automatically discharges
precipitated moisture from reservoir with each operating cycle of
the control device. The drain valve may be installed on main
reservoir with a sump.

55
D-24 B Feed Valve
The D-24 B Feed Valve is a large capacity highly sensitive relay valve
which is designed to direct the flow of air under pressure to various
devices in air brake equipment arrangement at a predetermined
pressure.

56
N-1 Reducing Valve
The N-1 Reducing Valve reduces the pressure of compressed air
supply to a constant predetermined value and delivers the same
usually for operation of auxiliary devices.

57
24-A Double Check valve
The 24-A Double Check Valve is used to permit a device to be
controlled by either of two other devices. Double check valve is used
to provide control of two sources without interaction between the
two.

58
Objective
The double check valve has two receiving ends that is why this valve
is used at several points in air brake system, wherever two air
sources are possible.
Construction
There is an internal floating check valve with "O" ring seal 7,
automatically directs the flow of air from one or the other of the two
controlling devices to a common discharge. At the same time,
prevents this air from flowing to the inoperative controlling device.
Operation
Referring to the assembly view, when a pressure differential exists
between the two end ports, the higher air pressure forces the check
valve 4 over to seal against its seat 3 on the flow pressure side. This
closes the passage between the low-pressure port and the common

59
port in the body 2. Air then flows from the high-pressure port
through the common port to the control device.
Important feature of the brake system
1. Locomotive brakes may be applied with any desired pressure
between the minimum and maximum. This pressure will be
maintained automatically in the locomotive brake cylinders against
normal leakage from them.
2. The locomotive brakes can be graduated on & off with either the
automatic or the independent brake valve.
3. It is always possible to release the locomotive brakes with the
independent brake valve, even when automatically applied.
4. The maximum braking position emergency, ensuring the shortest
possible stops distance.
5. It is always possible to haul both vacuum / air brake trains.
6. Automatic brake application and power cut off with idle rpm of
engine is always possible during train parting.
7. Multiple unit operation is also possible.
Releasing of brake
When handle is moved to release position, A9 valve starts supplying
full control pressure to add. C2 Relay valve causing BP pressure start
increasing to 5kg/cm2 and brakes are released.

60
Application of brake
A9 handle is moved in application zone for brake application. A9
reduces Control pressure to Add.C2 Relay valve. Add. C2 Relay
reduces BP pressure in proportion to control pressure drop. BP
pressure may be zero if A9handle moved at over reduction position.
If handle is placed at emergency position BP will drop to zero
immediately within 3 sec. After dropping BP pressure brakes are
applied.

Air brake system of locomotive

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (20)

Semelhante a Air brake system of locomotive

Semelhante a Air brake system of locomotive (20)

Último

Último (20)

Air brake system of locomotive