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Bendix

®

 R-12DC

 Relay Valve with Biased Double Check

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 chambers it serves.  The valve
operates as a remote controlled brake valve that delivers

FIGURE 1 - EXTERIOR VIEWS

EXTERIOR R-12DC

 VALVE

(MODEL WITH 2 HORIZONTAL PORTS)

PRIMARY

SERVICE

DELIVERY

SUPPLY (2)

SD-03-1068

SECONDARY

SERVICE

EXTERIOR

R-12DC

 VALVE

(MODEL WITH

4 VERTICAL

DELIVERY PORTS)

EXTERIOR

R-12DC

 VALVE

(MODEL WITH 2

HORIZONTAL AND 2

VERTICAL DELIVERY

PORTS)

PRIMARY

SERVICE

PORT

FIGURE 2 - R-12DC

 RELAY VALVE WITH BIASED DOUBLE CHECK SECTIONAL VIEW

RELAY

PISTON

VALVE

RETAINER

EXHAUST

SEAT

RETAINING

RING

EXHAUST

PORT

SECONDARY

SERVICE PORT

DOUBLE CHECK

DIAPHRAGM

GUIDE

SPRING

CAP SCREW

SEALING

RING

COVER

RELAY

PISTON

O-RING

SPRING

O-RINGS

INLET

EXHAUST

VALVE

or releases air to the chambers in response to the control
air delivered to it from the foot brake valve.

The R-12DC

 relay valves are designed for either reservoir

or frame mounting.  (See Figure 1).  For ease of servicing,
the inlet/exhaust valve can be replaced without the need for
line removal.

Summary of Contents for R-12DC DBL CHECK RELAY VALVE

Page 1: ...LVE MODEL WITH 4 VERTICAL DELIVERY PORTS EXTERIOR R 12DC VALVE MODEL WITH 2 HORIZONTAL AND 2 VERTICAL DELIVERY PORTS PRIMARY SERVICE PORT FIGURE 2 R 12DC RELAY VALVE WITH BIASED DOUBLE CHECK SECTIONAL...

Page 2: ...e will move shutting off the primary service line and instead allow the secondary service line to apply the air pressure needed to operate the valve Note Secondary service line may leak out of the pri...

Page 3: ...ded 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 det...

Page 4: ...NTAL DELIVERY PORTS DIFFERENTIAL SPRINGS FIGURE 7 R 12DC EXPLODED VIEW 1 Remove the four cap screws securing the mounting bracket and cover to the body Retain the cap screws for reuse 2 Discard the mo...

Page 5: ...cover assembly 16 2 Install o ring 8 on piston 9 3 Install sealing ring 7 on cover 1 4 Install retainer 12 on inlet exhaust valve 11 and insert both in the body 10 5 Install spring 13 in the body 10 6...

Page 6: ...R R 12DC RELAY VALVE COMPRESSOR FIGURE 8 TYPICAL PIPING SCHEMATIC DC 4 DOUBLE CHECK VALVE ANTI COMPOUND LINE GAUGE SR 1 SPRING BRAKE VALVE SERVICE BRAKE VALVE SPRING BRAKES PARKING VALVE ABS ECU MODUL...

Page 7: ...he vehicle If the vehicle is equipped with an AD IS air dryer system or a dryer reservoir module be sure to drain the purge reservoir 5 Following the vehicle manufacturer s recommended procedures deac...

Page 8: ...8 BW1933 2007 Bendix Commercial Vehicle Systems LLC All rights reserved 3 2007 Printed in U S A...

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