Bendix Commercial Vehicle Systems R-6 User Manual

®

Bendix® R-6™ Relay Valve

SERVICE

PORT

SUPPLY PORT

(RESERVOIR

MOUNT TYPE)

DELIVERY

PORTS (4)

RETURN

SPRING

SD-03-1060

RELAY PISTON

SUPPLY

PORT

FIGURE 1

EXHAUST

DESCRIPTION

The relay valve in an air brake system functions as a relay
station to speed up the application and release of the brakes.
The valve is normally mounted at the rear of the vehicle in
proximity to the chamber it serves. The valve operates as a
remote controlled brake valve that delivers or releases air to
the chamber in response to the control air delivered to it
from the foot brake valve or other source. The R-6™ relay
valve is a piston operated valve. For ease of servicing, an
“insert” or “cartridge” type inlet/exhaust valve is employed.
This feature permits service of the inlet/exhaust valve without
line removal. The R-6™ relay valve may be mounted directly
to or remotely from the reservoir which provides its supply
pressure. Standard porting consist s of one (1) service port
and four (4) delivery ports. There are two (2) supply ports in
the reservoir mounted valve and one (1) supply port in the
remote mount valve.

™

R-6

RELAY

VALVE INSERT

FIGURE 2

OPERATION

APPLYING

Air pressure delivered to the service port enters the small
cavity above the piston and moves the piston down. The
exhaust seat moves down with the piston and seats on the
inner or exhaust portion of the inlet/exhaust valve, sealing
off the exhaust passage. At the same time, the outer or inlet
portion of the inlet/exhaust valve moves off its seat, permitting
supply air to flow from the reservoir, p ast the open inlet valve
and into the chambers.

BALANCED

The air pressure being delivered by the open inlet valve also
is effective on the bottom area of the relay piston. When air
pressure beneath the piston equals the service air pressure
above, the piston lifts slightly and the inlet spring returns
the inlet valve to its seat. The exhaust remains closed as
the service line pressure balances the delivery pressure.
(NOTE: Some valves are equipped with a piston return spring
which will assist the lifting of the piston). As delivered air
pressure is changed the valve reacts instantly to the change
holding the brake application at that level.

1

RELEASING

When air pressure is released from the service port and air
pressure in the cavity above the relay piston is exhausted,
air pressure beneath piston lifts the relay piston and the
exhaust seat moves away from the exhaust valve, opening
the exhaust passage. With the exhaust passage open, the
air pressure in the chambers is then permitted to exhaust
through the exhaust port, releasing the brakes.

PREVENTIVE MAINTENANCE

Important: Review the Bendix Warranty Policy before

performing any intrusive maintenance procedures. A warranty
may be voided if intrusive maintenance is performed during
the warranty period.

No two vehicles operate under identical conditions, as a
result, maintenance intervals may vary. Experience is a
valuable guide in determining the best maintenance interval
for air brake system components. At a minimum, the valve
should be inspected every 6 months or 1500 operating hours,
whichever comes first, for proper operation. Should the valve
not meet the elements of the operational tests noted in this
document, further investigation and service of the valve may
be required.

4. Make and hold a brake valve application; coat the exhaust
port with soap solution and check for leakage; 1" bubble
in 3 seconds leakage permitted.

If leakage is detected, replacing the inlet/exhaust valve may
correct the problem. If leakage still occurs, leakage may be
caused by relay piston o-ring or exhaust valve seat.

5. Make and hold a brake valve application; coat outside of
valve body in area where cover joins the body for cover
o-ring leakage No leakage permitted. If the valve does
not function as described above, or if leakage is
excessive, it is recommended that the valve be replaced
with a new or remanufactured unit, or repaired with
genuine Bendix parts available at Bendix outlets.

REMOVING AND INSTALLING

REMOVING

Block and hold vehicle by means other than air brakes.
Drain air brake system reservoirs.
If entire valve is to be removed, identify air lines to facilitate

installation.
Disconnect air lines from valve*.

OPERATING AND LEAKAGE TEST

1. Fully charge air brake system and adjust brakes.

2. Make several brake applications and check for prompt
application and release at all appropriate wheels.

3. With brake valve in released position, coat the exhaust
port with soap solution and check for inlet valve and valve
guide o-ring leakage; 1" bubble in 5 seconds leakage
permitted.

BRAKE

VALVE

COMPRESSOR GOVERNOR

SUPPLY

RESERVOIR

Remove mounting bolts, then valve.
*It is generally not necessary to remove entire valve to service

the inlet/exhaust valve. The inlet/exhaust valve insert can be
removed by removing the two exhaust cover cap screws
and cover. Insert then may be pulled out.

CAUTION: DRAIN RESERVOIRS BEFORE REMOVING
INSERT. Use care so as not to damage inlet/exhaust valve

or guide o-ring.

RELAY
VALVE

SERVICE

RESERVOIR

TYPICAL RELA Y V AL VE PIPING SINGLE CIRCUIT SYSTEM

2

BRAKE

CHAMBERS