SD-03-2205
Bendix® SC-3™ In-Line Single Check Valves
inlet outlet
spring
inlet outlet
(one sc-3™
valve model
features
this 1/16”
Pipe plug)
wafer-type
check valve
FIGURE 1 - SC-3™ Single check valves FIGURE 2 - SC-3™ single check valve: wafer-type
(Exterior and cross-sectional views)
DESCRIPTION
inlet
The Bendix® SC-3™ in-line single check valve is a device
placed in an air line to allow air flow in one direction only spring
and to prevent flow of air in the reverse direction.
outlet
The two types of SC-3™ in-line single check valves are:
1. The wafer-style type (Figure 2).
2. The ball type (Figure 3). outlet
An arrow indicating the direction of air flow is found on the
body of the valve. ball
OPERATION FIGURE 3 - SC-3™ angle check valve: ball type
(Exterior and cross-sectional views)
Air flow in the normal direction moves the check valve
from its seat, and the flow is unobstructed. Flow in the No two vehicles operate under identical conditions; as
reverse direction is prevented by the seating of the ball or a result, maintenance intervals may vary. Experience is
wafer-type disc, which is caused by a drop in up-stream a valuable guide in determining the best maintenance
air pressure and assisted by the spring. interval for air brake system components. At a minimum,
the SC-3™ valve should be inspected every 6 months or
PREVENTATIVE MAINTENANCE 1500 operating hours, whichever comes first, for proper
operation. Should the SC-3™ valve not meet the elements
Important: Review the Bendix Warranty Policy before of the operational tests noted in this document, further
performing any intrusive maintenance procedures. A investigation and service of the valve may be required.
warranty may be voided if intrusive maintenance is Replace any check valves leaking or showing signs of
performed during the warranty period. wear or deterioration.
Installation General Safety Guidelines
wARNING! Please READ and follow these
The straight SC-3™ check valve consists of a two piece
instructions to avoid personal injury or
body. When installing the valve, tighten using the hex
death:
surface that is closest to the port that it is being installed in.
When working on or around a vehicle, the following
See Figure 4. This will prevent breaking the seal between
general precautions should be observed at all times.
the two halves which would cause leakage.
1. Park the vehicle on a level surface, apply the parking
brakes, and always block the wheels. Always wear
Use this surface Do NOt Use this safety glasses.
for tightening surface for 2. Stop the engine and remove ignition key when working
tightening under or around the vehicle. When working in the engine
compartment, the engine should be shut off and the
ignition key should be removed. Where circumstances
require that the engine be in operation, EXTREME
CAUTION should be used to prevent personal injury
resulting from contact with moving, rotating, leaking,
heated or electrically charged components.
FIGURE 4 - SC-3™ Check Valve with 2 piece Body
3. Do not attempt to install, remove, disassemble or
assemble a component until you have read and
thoroughly understand the recommended procedures.
OPERATION & LEAKAGE CHECKS
Use only the proper tools and observe all precautions
NOTE: Depending upon installation, it may be easier or pertaining to use of those tools.
necessary to completely remove check valves so that the 4. If the work is being performed on the vehicle’s air brake
following checks may be made. system, or any auxiliary pressurized air systems, make
certain to drain the air pressure from all reservoirs
With air pressure present at outlet side of check valve and before beginning ANY work on the vehicle. If the
the inlet side open to atmosphere, coat the open end of vehicle is equipped with an AD-IS® air dryer system or
the check valve with soap suds; a 1” bubble in 5 seconds a dryer reservoir module, be sure to drain the purge
is permissible (100 SCCM). reservoir.
5. Following the vehicle manufacturer’s recommended
If the check valve does not function as described, or procedures, deactivate the electrical system in a
leakage is excessive, it is recommended that it be replaced manner that safely removes all electrical power from
with a new genuine Bendix part available at any Bendix the vehicle.
parts outlet. 6. Never exceed manufacturer ’s recommended
pressures.
REMOVAL
7. Never connect or disconnect a hose or line containing
Block and hold vehicle by means other than air brakes. pressure; it may whip. Never remove a component or
plug unless you are certain all system pressure has
Completely drain all reservoirs. been depleted.
Disconnect air lines at single check valve and remove. 8. Use only genuine Bendix ® replacement parts,
components and kits. Replacement hardware, tubing,
DISASSEMBLY/ASSEMBLY hose, fittings, etc. must be of equivalent size, type
and strength as original equipment and be designed
Note: There are no Disassembly/Assembly procedures for specifically for such applications and systems.
SC-3™ valves. They are non-serviceable items. If a valve
9. Components with stripped threads or damaged parts
does not meet the Operational and Leakage tests, it should should be replaced rather than repaired. Do not
be replaced at any authorized Bendix parts outlet. attempt repairs requiring machining or welding unless
specifically stated and approved by the vehicle and
TESTING AND TROUBLESHOOTING component manufacturer.
Perform “Operating and Leakage Checks”. 10. Prior to returning the vehicle to service, make certain all
components and systems are restored to their proper
operating condition.
11. For vehicles with Antilock Traction Control (ATC),
the ATC function must be disabled (ATC indicator
lamp should be ON) prior to performing any vehicle
maintenance where one or more wheels on a drive
axle are lifted off the ground and moving.
BW1892 © 2007 Bendix Commercial Vehicle Systems LLC. All rights reserved. 3/2007 Printed in U.S.A.
