SC-1 Empty/Load
Equipment
Operation, Adjustment & Testing
November 2002
Copyright © 2002 by Wabtec Corporation
Operation of the SC-1
The SC-1 empty/load equipment includes the use of an:
•
S-1 Sensor Valve
•
P-1 Proportional Valve
•
Equalizing Reservoir
Piping Arrangements
The brake cylinder pipe from
the control valve is connected
to the P-1 Proportional Valve.
· The pipe from the Proportional
Valve directs air to the brake
cylinder and sensor valve.
SC-1 Empty/Load Brake Arrangement
· A pipe from the sensor valve is
connected to the Equalizing
Reservoir.
Equalizing
Reservoir
· From the Equalizing Reservoir
there is a pipe connection back to
the Proportional Valve.
AB Type
Control Valve
P-1 Proportional
Valve
S-1 Sensor
Valve
Truck Side Frame
Brake
Cylinder
Combined Aux.
& Emergency
Reservoir
S-1 Sensor
It is secured to the car body bolster at a point where the sensor arm contact ball
will touch the truck side frame on a brake application.
· The contact ball of the sensor arm will extend on each brake application to contact
the truck side frame and provide an accurate loaded or empty brake application. The
distance the sensor arm travels is controlled by the car weight compressing the truck
springs.
· The sensor arm contact ball must be set properly to maintain accurate brake cylinder pressure for each brake application.
· There is no partial load or partial empty braking available. A loaded brake application occurs when there is approximately 20% loaded weight in the car.
SENSOR ARM
CONTACT BALL
P-1 Proportional Valve
Air pressure from the control valve must go through the Proportional Valve before
it is directed to the brake cylinder.
· The Proportional Valve provides a balance of brake
cylinder pressure and equalizing reservoir for an
empty brake application.
· A 50% or 60% Proportional Valve may be used
based on the car empty weight versus the car loaded
weight.
· The 50% and 60% Proportional Valves are not
interchangeable.
· The 50% Proportional Valve is designed to provides
50% of the brake cylinder pressure to the brake
cylinder for a full service brake application on an
empty car.
· The 60% Proportional Valve is designed to provide
60% of the brake cylinder pressure to the brake
cylinder for a full service brake application on an
empty car.
Equalizing Volume
· This is a small reservoir in line
from the Sensor Valve to the
Proportional Valve.
· It will provide an air pressure
balance with the brake cylinder on
an empty car brake application.
The amount of air pressure in the
Equalizing Reservoir depends
upon the type of Proportional
Valve on the car, 50% or 60%.
· With the SC-1 Brake
Arrangement functioning properly
and the sensor valve set correctly,
there is air in Equalizing Reservoir
only on an empty brake
application.
Operation – Empty Car
Service Brake Application
1
Air pressure from the auxiliary reservoir is directed
by the control valve to the P-1 Proportional Valve.
2
In the proportional valve, the air is allowed to flow
to the brake cylinder and sensor valve.
3
Air in the sensor valve forces the sensor arm
down. As the car is empty there is no weight to
compress the car truck springs. As a result the
sensor arm will move all the way down.
4
This opens a passage within the sensor valve to
allow air to flow to the equalizing reservoir.
5
Air in the equalizing reservoir will also flow back to
the top side of the proportional valve’s internal
valve assembly.
6
This return air from the equalizing reservoir will
cause the proportional valve to provide the correct
balance of air in the brake cylinder and equalizing
volume.
Brake Application - Empty Condition
AB Type
Control Valve
Equalizing
Reservoir
P-1 Proportional
Valve
S-1 Sensor
Valve
Brake
Cylinder
Truck Side Frame
Combined Aux.
& Emergency
Reservoir
Operation – Loaded Car
Service Brake Application
1
Air pressure from the auxiliary
reservoir is directed by the control
valve to the P-1 Proportional
Valve.
2
The proportional valve will allow the
air to flow to the brake cylinder and
sensor valve.
3
With a loaded car the truck springs
are compressed making the car
body closer to the truck side frame.
The sensor arm’s travel is now
restricted.
4
With limited travel the sensor will
not allow air to flow to anywhere but
the brake cylinder.
5
This provides 100% of the brake
cylinder air pressure to the brake
cylinder.
Brake Application - Loaded Condition
Equalizing
Reservoir
AB Type
Control Valve
P-1 Proportional
Valve
S-1 Sensor
Valve
Truck Side Frame
Brake
Cylinder
Combined Aux.
& Emergency
Reservoir
Operation – Brake Release/Empty Car
Brake Release - Empty
1
Air from the brake cylinder is directed
back through the proportional valve to
the control valve.
2
With no brake cylinder air at the
sensor valve. The sensor valve arm
will move up to the release position.
3
The air in the equalizing reservoir is
restricted from flowing back to the
control valve.
4
The air from the equalizing reservoir is
allowed to vent out the exhaust port on
the bottom of the sensor valve.
5
The sensor arm must move up to the
release position thus allowing the air in
the equalizing reservoir to escape.
This ensures the correct brake
cylinder pressure for each successive
brake application.
Brake Release - Empty Condition
Equalizing
Reservoir
Equalizing
Reservoir
AB Type
Control Valve
Retainer
Valve
P-1 Proportional
Valve
S-1 Sensor
Valve
Truck Side Frame
Brake
Cylinder
Combined Aux.
& Emergency
Reservoir
SC-1U Empty/Load Equipment
· The SC-1U (Unitized) Empty/Load equipment is designed for intermodal articulated cars. The SC-1U
assembly is mounted on the truck assembly to ensure correct brake cylinder pressure is directed to
that truck brake cylinder according to the load the truck is carrying.
· The S-1 Sensor Valve and P-1 Proportional Valve are mounted on a pipe bracket which also incorporates
the Equalizing Volume. There are only two pipe connections to be made; “IN” from the Control Valve and
“OUT” to the brake cylinder. With the S-1 mounted on the pipe bracket, the whole assembly must be
mounted adjacent to the truck bolster to allow the sensor valve to measure the spring deflection.
· Flexible hoses are generally used to allow for truck swing and travel.
· There are four distinct models of the SC-1U. Each unit has its own piece number, available in right hand
and left hand versions, with two different mounting arrangements.
· The P-1 and S-1 portions used on the SC-1U equipment are standard components. The pipe bracket
determines the different piece numbers.
SC-1C Empty/Load Equipment
· The SC-1C equipment has the Sensor Valve and Proportioning Valve sharing a
common casting. The required volume is contained within the pipe bracket portion,
which may be increased by the addition of extra volume. As with the SC-1U
equipment, only two pipe connections are required.
· The SC-1C Sensor/Proportional Valve is an Integrated Load Sensor Valve,
Proportional Valve and Equalizing Volume.
· The Sensor/Proportional Valve consists of an operating portion which is mounted to
a pipe bracket. The Pipe Bracket Portion also acts as the equalizing volume. This
arrangement permits the easy removal of the operating portion without disturbing the
car piping.
· The SC-1C is designed for use in specific equipment arrangements where the air
pressure does not exceed 110 psig.
S-1 Sensor Adjustment
Sensor valve adjustment may be necessary when:
1
The sensor valve is changed in accordance
with AAR Rule 4 of the Field Manual of
Interchange Rules. See AAR Rule 3, Chart A.
2
The sensor is not providing a correct brake
cylinder pressure as noted on the brake
cylinder measurement gauge. Pressure must
be at least 20 psi lower for an empty brake
application versus the loaded full service
brake application. (AAR S-486-02)
3
On the brake application of a loaded car, there
is air directed to the equalizing reservoir. This
will indicate the freight car is braking as an
empty car. This is determined by low
pressure in the brake cylinder as noted on
the brake cylinder measurement gauge
during the brake application or an exhaust
of air from the sensor valve exhaust on a
release of the brakes.
* Components of the S-1 Sensor Valve and the
set up of the valve for adjustment purposes are
depicted to the right.
Plug
Securement
Screws
Contact
Ball
Sensor Arm
Adjusting
Block
Truck Side Frame
Tools & Equipment Requirements for Adjusting
· Car must be on a level section of track.
· The freight car must be secured against
movement.
· AAR Approved Single Car Test Device
must be used for testing and adjustment.
· Car must be empty.
· Block used for verifying loaded condition
is 2 ¼”
· Adjusting block thickness to be equal to
1
/5 the spring deflection between light and
loaded car.
· Where spring deflection is unknown use a
7
/16” block. We recommend that if new
center plate lubricator pads are installed,
1
/8” maximum be added to the adjusting
block thickness. If new springs, subject to
settling have been installed, an additional
1
/4” maximum thickness is recommended.
· Brake cylinder measurement gauge (see
AAR S-4020)
Sample Adjustment Block
2 ¼”
7/16”
Brake Cylinder
Measurement Gauge
Adjustment of Sensor Valve – 1
1.
2.
Connect the Single Car Test Device as noted in AAR S-486, latest revision.
With the branch pipe cut-out cock in the open position, and the test device in the high
pressure position, place the test device handle in Position 1.
Adjustment of Sensor Valve – 2
3
Ensure there is a blow of air through the car at the opposite end by making sure the angle
cock is in the open position. If not already open, use caution when opening the angle cock
as shown to avoid injury.
Adjustment of Sensor Valve – 3
4.
Once this is noted, attach a dummy coupling to the air hose to allow charging of the car air
brake system.
5.
Place the empty adjustment block under the
sensor arm on the truck side frame at a
point where the sensor arm will make
contact with the block.
Adjustment of Sensor Valve – 4
6
Loosen the securement
nuts on the adjusting screw.
7
Turn the adjusting screw counterclockwise to
extend it and thus allow for adjustment.
Adjustment of Sensor Valve – 5
8. Using a 9/16” wrench, remove the plug from the sensor valve body. On older
style sensor valves an Allen Wrench may be required to remove the plug.
9
Charge the brake system to a
point where the flowrator ball
is below the top of the tube.
Adjustment of Sensor Valve – 6
10
Move the test device handle to Position 5 and reduce the brake pipe pressure
to 60 psi. Slowly move the test device handle back to Position 3 or lap.
11. Brakes must apply as noted by the brake cylinder piston being extended.
Adjustment of Sensor Valve – 7
12
The sensor arm must move down and
and the contact ball must touch the
adjustment block. With the adjustment
screw extended there should be no blow
of air from the sensor plug hole at this
time. If there is, the adjustment screw
may have not been turned down far
enough or the arm may be damaged or
the sensor valve may have failed.
13
Turn in on adjusting screw until a light blow of air is noted at open hole on the sensor
valve.
Adjustment of Sensor Valve – 8
14.
When this is noted, replace the plug in the sensor body.
15. Tighten the adjusting screw securement nuts to the sensor arm to maintain the screw in
the correct position.
Adjustment of Sensor Valve – 9
16.
Carefully remove the adjustment block.
17.
Check for leaks at the sensor plug using soap and water, no leakage allowed.
Adjustment of Sensor Valve – 10
18
19
Place test device handle back into Position 1 and note that the brakes release.
As the sensor arm rises during the brake release, note air exhausting at vent
of sensor valve. This is air allowed into the equalizing reservoir indicating the brakes
applied as if the car was empty.
Testing – Empty Car/Empty Condition
1
With the car charged to a point where the flowrator ball is below the top of the tube, make
a 30 psi reduction in Position 5. Move the test device handle to LAP or Position 3.
2
Make sure sensor arm contact ball
touches the side frame and the brakes
are applied. Check the brake cylinder
pressure measurement gauge. The
brake cylinder pressure should be
proportionally lower than the loaded
brake application pressure depending
upon the type of proportional valve. See
the Wabtec Single Car Test Manual
(WAB/SCT-1) for a chart of empty brake
cylinder pressures.
Testing – Empty Car/Empty Condition
3. Move test device handle back to
Position 1 and recharge the car.
4
Check to ensure the brakes release, the sensor
arm raises up and there is a blow from the sensor
valve exhaust.
Brake Release
A Blow of Air Here
Testing – Empty Car/Loaded Condition
1
Insert a 2 ¼” block between the truck side frame and the sensor valve contact ball. Check
the sensor arm contact ball will touch the block when the brakes are applied.
2
With the brake pipe charged to a point
where the flowrator ball is below the top of
the tube, move the test device handle to
Position 5 and make a 30 psi reduction.
Testing – Empty Car/Loaded Condition
3.
Slowly move the test device handle to LAP or Position 3.
4.
Brakes must apply and sensor contact ball must make contact with 2 ¼” block.
Testing – Empty Car/Loaded Condition
5
With the brakes applied, check the brake cylinder pressure as noted on the
brake cylinder measurement gauge. Pressure in the brake cylinder should have reached
equalization between 60 – 70 psi.
Testing – Empty Car/Loaded Condition
6
Place the test device handle back into Position 1 and recharge the brake pipe. On the
release of the brakes note there is no exhaust of air from the exhaust port of the sensor
valve.
NOTE: In accordance with AAR S-486 the 2 ¼” block must remain in place for part of the brake
cylinder leakage test and or the Single Car Test procedure. See AAR Field Manual of Interchange Rules - Rule 3, Chart A for test requirements.
Problems & Troubleshooting
1
Brakes do not apply with a 30 psi reduction.
With the control valve operating correctly, air from the control valve is directed to the P-1 Proportional
valve. The Proportional valve must function as designed to allow the air pressure to flow to the brake
cylinder and the sensor valve.
2
Brakes will not release when the test device handle is returned to Position 1.
The sensor valve or the proportional valve may be at fault. The sensor must allow air to exhaust to the
proportional valve this is shown by the sensor valve arm moving upward. If the arm does not move up,
air is trapped at the proportional valve. If the arm moves up, the air from the brake cylinder will exhaust.
3
During the adjustment of the sensor, air exhausts from the plug hole
as soon as the plug is removed.
Is the sensor valve adjustment arm contact ball to its maximum extension? If so, the sensor arm may
be damaged or the valve may have failed. Change out the valve if no visual defects exist.
4
The sensor arm contact ball is to it’s maximum extension and there
is air exhausting from the plug hole.
The sensor arm may be bent/damaged or the valve may have failed. Change out the
valve if no visual defects exist.
Problems & Troubleshooting
5 On a new car application, the brakes apply on a brake pipe
reduction but the sensor arm does not move down to contact the side frame.
The sensor may be piped incorrectly or the tape/plugs used to protect the valve for shipping were
not removed before the sensor was applied. Make necessary repairs and retest.
6 The sensor arm will not move back up to the release position when the brakes release even through the brake piston
returns to release position. Is this a problem?
Yes, if the sensor arm does not move back up to the release position with an empty car, it will trap
air in the equalizing reservoir. On the next empty brake application the pressure in the equalizing
reservoir will have higher pressure and could result in higher brake cylinder pressure.
Quiz - Page 1
1.
The size of block used to check for loaded operation of a sensor valve when the car is empty is:
a. 2”
c. 2 1/4”
b. 2 5/8”
d. 1 3/4”
2
On a car with a 60% proportional valve, how much pressure will be directed to the brake cylinder
when the car is empty?
a. 50%
c. 60%
b. 40%
d. 100%
3
What size adjustment block is used to set the sensor arm for an empty car when the spring travel
is unknown?
a. 3/4”
c. 5/8”
b. 7/16”
d. 1/4”
4.
The sensor arm travel can only be set properly on a empty car?
True
False
5
Add 1/2” shim to the adjustment block when applying all new truck springs.
True
False
6
The SC-1 Empty/load brake equipment will provide partial braking on a car if it has a partial load.
True
False
Quiz - Page 2
7. From the diagram on the right side of the page, identify each part or component part
by name.
A
______________________
B
______________________
C
______________________
D
______________________
E
______________________
F
______________________
A
B
C
D
E
F
Quiz - Page 3
8.
Match the following component to their function by placing the correct letter in front of the
statement that best describes its function:
A.
Truck side frame
__ Directs air to the equalizing reservoir for an empty
application.
B.
2 ¼” block
__ Used to set the sensor adjustment on a empty car.
C.
Securement nuts
__ Used to hold a portion of the brake cylinder air
pressure for an empty application.
D.
S-1 Sensor Valve
__ Holds the S-1 adjusting screw in place.
E.
Proportional Valve
F.
Equalizing Reservoir
G.
7/16” block
H.
1/8” block
__ Used to check for loaded operation of the sensor
valve on an empty car.
__ Ensures there is the correct percent of air pressure
in the brake cylinder for an empty car.
__ A shim added to the adjustment block when
lubrication pads are added to the center plate of a
car.
__ The contact point for the sensor arm contact ball.
The End
If you have questions or comments related to this SC-1/Empty Load equipment
Training module, feel free to contact Michael Zenert as listed below.
Michael Zenert
Manager Air Brake Training
Wabtec Global Services
1001 Air Brake Avenue
Wilmerding, PA 15148
Phone: 412-825-1453
Fax: 412-825-1499
E-mail: [email protected]
Click here to send comments
Quiz Answers
1.
C
2.
C
3.
B
4.
True
5.
False
A
6.
False
7. From the diagram on the right side of the page,
identify each part or component part by name.
A
B
C
D
E
F
Plug
Securement Nuts
Contact Ball
Sensor Arm
Adjustment Block
Truck Side Frame
B
C
D
E
F
Quiz Answers
8.
A.
B.
C.
D.
E.
F.
G.
H.
Match the following component to their function by placing the correct letter in front of the
statement that best describes its function:
Truck side frame
2 ¼” block
Securement nuts
S-1 Sensor Valve
Proportional Valve
Equalizing Reservoir
7/16” block
1/8” block
D. Directs air to the equalizing reservoir for an empty
application.
G. Used to set the sensor adjustment on a empty car.
F. Used to hold a portion of the brake cylinder air
pressure for an empty application.
C. Holds the S-1 adjusting screw in place.
B. Used to check for loaded operation of the sensor
valve on an empty car.
E. Ensures there is the correct percent of air pressure
in the brake cylinder for an empty car.
H. A shim added to the adjustment block when
lubrication pads are added to the center plate of
a car.
A. The contact point for the sensor arm contact ball.
Operation – Empty Car
Service Brake Application
1
Air pressure from the auxiliary reservoir is
directed by the control valve to the P-1 Proportional Valve.
2
In the proportional valve, the air is allowed to
flow to the brake cylinder and sensor valve.
3
Air in the sensor valve forces the sensor arm
down. As the car is empty there is no weight
to compress the car truck springs. As a result
the sensor arm will move all the way down.
4
This opens a passage within the sensor valve
to allow air to flow to the equalizing reservoir.
5
Air in the equalizing reservoir will also flow
back to the top side of the proportional
valve’s internal valve assembly.
6
This return air from the equalizing reservoir
will cause the proportional valve to provide
the correct balance of air in the brake cylinder
and equalizing volume.
Brake Application - Empty Condition
AB Type
Control Valve
Equalizing
Reservoir
P-1 Proportional
Valve
S-1 Sensor
Valve
Brake
Cylinder
Truck Side Frame
Combined Aux.
& Emergency
Reservoir
Operation – Brake Release/Empty Car
Brake Release - Empty
1
Air from the brake cylinder is directed
back through the proportional valve to
the control valve.
Brake Release - Empty Condition
2
With no brake cylinder air at the
sensor valve. The sensor valve arm
will move up to the release position.
3
The air in the equalizing reservoir is
restricted from flowing back to the
control valve.
4
The air from the equalizing reservoir is
allowed to vent out the exhaust port on
the bottom of the sensor valve.
Equalizing
Reservoir
Equalizing
Reservoir
The sensor arm must move up to the
release position thus allowing the air in
the equalizing reservoir to escape.
This ensures the correct brake
cylinder pressure for each successive
brake application.
Retainer
Valve
P-1 Proportional
Valve
S-1 Sensor
Valve
Truck Side Frame
5
AB Type
Control Valve
Brake
Cylinder
Combined Aux.
& Emergency
Reservoir
Adjustment of Sensor Valve – 7
12
The sensor arm must move down and and
the contact ball must touch the adjustment
block. With the adjustment screw extended
there should be no blow of air from the
sensor plug hole at this time. If there is, the
adjustment screw may have not been turned
down far enough or the arm may be
damaged or the sensor valve may have
failed.
13
Turn in on adjusting screw until a light blow of air is noted at open hole on the sensor
valve.
Operation – Empty Car
Service Brake Application
1
Air pressure from the auxiliary reservoir is
directed by the control valve to the P-1
Proportional Valve.
2
In the proportional valve, the air is allowed to flow
to the brake cylinder and sensor valve.
3
Air in the sensor valve forces the sensor arm
down. As the car is empty there is no weight to
compress the car truck springs. As a result the
sensor arm will move all the way down.
4
This opens a passage within the sensor valve to
allow air to flow to the equalizing reservoir.
5
Air in the equalizing reservoir will also flow back
to the top side of the proportional valve’s internal
valve assembly.
6
This return air from the equalizing reservoir will
cause the proportional valve to provide the
correct balance of air in the brake cylinder and
equalizing volume.
Brake Application - Empty Condition
AB Type
Control Valve
Equalizing
Reservoir
P-1 Proportional
Valve
S-1 Sensor
Valve
Brake
Cylinder
Truck Side Frame
Combined Aux.
& Emergency
Reservoir
Operation – Brake Release/Empty Car
Brake Release - Empty
1
Air from the brake cylinder is directed
back through the proportional valve to
the control valve.
2
With no brake cylinder air at the sensor
valve. The sensor valve arm will move
up to the release position.
3
The air in the equalizing reservoir is
restricted from flowing back to the
control valve.
4
5
Brake Release - Empty Condition
Equalizing
Reservoir
Equalizing
Reservoir
The air from the equalizing reservoir is
allowed to vent out the exhaust port on
the bottom of the sensor valve.
The sensor arm must move up to the
release position thus allowing the air in
the equalizing reservoir to escape. This
ensures the correct brake cylinder
pressure for each successive brake
application.
AB Type
Control Valve
Retainer
Valve
P-1 Proportional
Valve
S-1 Sensor
Valve
Truck Side Frame
Brake
Cylinder
Combined Aux.
& Emergency
Reservoir
S-1 Sensor Adjustment
Sensor valve adjustment may be necessary when:
•
•
•
The sensor valve is changed in accordance with
AAR Rule 4 of the Field Manual of Interchange
Rules. See AAR Rule 3, Chart A.
The sensor is not providing a correct brake
cylinder pressure as noted on the brake cylinder
measurement gauge. Pressure must be at least
20 psi lower for an empty brake application
versus the loaded full service brake
application. (AAR S-486-02)
On the brake application of a loaded car, there is
air directed to the equalizing reservoir. This will
indicate the freight car is braking as an empty
car. This is determined by low pressure in the
brake cylinder as noted on the brake cylinder
measurement gauge during the brake
application or an exhaust of air from the
sensor valve exhaust on a release of the
brakes.
* Components of the S-1 Sensor Valve and the
set up of the valve for adjustment purposes are
depicted to the right.
Plug
Securement
Screws
Contact
Ball
Sensor Arm
Adjusting
Block
Truck Side Frame