BENDIX R-12DC Mounting instructions

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

or releases air to the chambers in response to the control

air delivered to it from the foot brake valve.

Figure 1 – Exterior Views

EXTERIOR BENDIX®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 – Bendix®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

Bendix®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.

GENERAL SAFETY GUIDELINES

WARNING! PLEASE READ AND

FOLLOW THESE INSTRUCTIONS

TO AVOID PERSONAL INJURY OR DEATH:

When working on or around a vehicle, the following

guidelines should be observed AT ALL TIMES:

▲Park the vehicle on a level surface, apply the parking

brakes and always block the wheels. Always wear personal

protection equipment.

▲Stop the engine and remove the ignition key when working

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.

▲Do not attempt to install, remove, disassemble or

assemble a component until you have read, and thoroughly

understand, the recommended procedures. Use only the

proper tools and observe all precautions pertaining to use

of those tools.

▲If the work is being performed on the vehicle’s air brake

system, or any auxiliary pressurized air systems, make

certain to drain the air pressure from all reservoirs before

beginning ANY work on the vehicle. If the vehicle is

equipped with a Bendix®AD-IS®air dryer system, a Bendix®

DRM™dryer reservoir module, or a Bendix® AD-9si®air

dryer, be sure to drain the purge reservoir.

▲

Following the vehicle manufacturer’s recommended

procedures, deactivate the electrical system in a manner

that safely removes all electrical power from the vehicle

▲Never exceed manufacturer’s recommended pressures.

▲Never connect or disconnect a hose or line containing

pressure; it may whip and/or cause hazardous airborne

dust and dirt particles. Wear eye protection. Slowly open

connections with care, and verify that no pressure is

present. Never remove a component or plug unless you are

certain all system pressure has been depleted.

▲Use only genuine Bendix®brand replacement parts,

components and kits. Replacement hardware, tubing, hose,

ﬁ ttings, wiring, etc. must be of equivalent size, type and

strength as original equipment and be designed speciﬁ cally

for such applications and systems.

▲Components with stripped threads or damaged parts should

be replaced rather than repaired. Do not attempt repairs

requiring machining or welding unless speciﬁ cally stated

and approved by the vehicle and component manufacturer.

▲Prior to returning the vehicle to service, make certain all

components and systems are restored to their proper

operating condition.

▲For vehicles with Automatic 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.

▲The power MUST be temporarily disconnected from the

radar sensor whenever any tests USING A DYNAMOMETER

are conducted on a vehicle equipped with a Bendix®

Wingman®system.

▲You should consult the vehicle manufacturer's operating

and service manuals, and any related literature, in

conjunction with the Guidelines above.

Figure 3 – Typical System Schematic

PARK

CONTROL

VALVE

MODULATOR

SUPPLY #1 SERVICE

RESERVOIR

#2 SERVICE

RESERVOIR

DOUBLE

CHECK VALVE

BRAKE

VALVE

BENDIX®

R-12DC®

VALVE

SPRING

BRAKE

CHAMBER

SLACK

ADJUSTER

QUICK

RELEASE

VALVE

BENDIX®

R-14®

RELAY

VALVE

BENDIX®

SR-1™

VALVE

OPERATION

APPLICATION

Under normal conditions, the internal biased double-check

valve ensures that the primary service signal controls

the valve. Air pressure delivered to the primary 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

ow from the reservoir, past the open inlet valve and into

the service brake chambers. In the event of a loss of the

primary service line, (see Figure 5) the double-check valve

mechanism in the cover of the Bendix®R-12DC®valve 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 primary

service at control pressures up to 20 psi when the primary

signal is not present.

BENDIX®R-12DC®

VALVE

ANTILOCK SENSOR

TONE RING

ANTILOCK

MODULATOR

BRAKE VALVE

(DELIVERY

LINES ARE

SHOWN)

RESERVOIR

BRAKE

CHAMBERS

Figure 4 – Bendix®R-12DC®Valve Sectional View with

Typical System Components

RELAY PISTON

EXHAUST

PORT

INLET

EXHAUST

VALVE

BALANCE

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. As delivered air pressure is changed,

the valve reacts instantly to the change, holding the brake

application at that level.

EXHAUST OR RELEASE

When air pressure is released from the service ports, air

pressure in the cavity above the relay piston is exhausted

through the primary circuit of the brake valve. At the same

time, air pressure beneath the 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 brake 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 rst, 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.

BRAKES

APPLIED

Figure 5 – Bendix®R-12DC® Valve Applied Position (Showing Biased Double-Check Operational Views)

SECONDARY

CONTROL LINE

SUPPLIES RELAY

PISTON

CONTROL LINE

FAILURE

NORMAL: BIASED

DOUBLE-CHECK VALVE-

PRIMARY

CONTROL LINE SUPPLIES

RELAY PISTON

BRAKE PEDAL

APPLIED

BRAKE PEDAL

APPLIED

BRAKE PEDAL

APPLIED

BRAKE

CHAMBERS

MAINTAIN

APPLICATION

Figure 6 – Bendix®R-12DC®Valve Balance Position

AIR PRESSURE

ABOVE RELAY

VALVE IS

EXHAUSTED

HERE

BRAKE

CHAMBERS

RELEASED

Figure 7 – Bendix®R-12DC®Valve Exhaust Position

AIR PRESSURE

FROM BRAKE

CHAMBERS IS

EXHAUSTED

HERE

BRAKE PEDAL

POSITION

HELD

BRAKE

PEDAL

RELEASED

REMOVAL AND INSTALLATION

REMOVAL

1. Block and hold the vehicle by means other than the air

brakes.

2. Drain the air brake system reservoirs.

3. If the entire valve is to be removed, identify the air lines

to facilitate reinstallation. Prior to disassembly, remove

as much contamination as possible from the exterior of

the device taking care to keep all contamination from

entering the open ports.

4. Disconnect the air lines from the valve*.

5. Remove the valve from the reservoir or, if remotely

mounted, remove the mounting bolts and then the

valve.

*It is generally not necessary to remove the entire valve

to service the inlet/exhaust valve. The inlet/exhaust valve

insert can be removed by removing the snap ring, exhaust

cover assembly and then the inlet/exhaust valve.

Caution: Drain all reservoirs before attempting to remove

the inlet/exhaust valve.

DISASSEMBLY

Note: Prior to disassembly, mark the location of the

mounting bracket to the cover and the cover to the body.

CAUTION: The valve body may be lightly clamped in a

bench vise during disassembly, however, over-clamping will

result in damage to the valve and result in leakage and/or

malfunction. If a vise is to be used, position the valve so

that the jaws bear on the supply ports on opposing sides

of the valve’s body. Refer to Figure 8.

1. Remove the four cap screws securing the mounting

bracket and cover to the body. Retain the cap screws

for reuse.

2. Discard the mounting bracket.

3. Remove and discard the sealing ring (7) from the cover

(1).

a. Remove the two Torx®screws securing the double-

check cover (6) to the cover (1).

b. Remove the double-check cover (6) from the

valve cover (1) and remove and discard the spring

(2), guide (3), double-check diaphragm (4), and

o-ring (5).

KEY NO. DESCRIPTION

1 VALVE COVER

2 VALVE SPRING

3 CHECK VALVE GUIDE

4 CHECK VALVE

5 O-RING

6 DOUBLE CHECK COVER

7 O-RING

8 O-RING

9 RELAY PISTON

10 VALVE BODY

11 INLET & EXHAUST VALVE

12 VALVE RETAINER

13 SPRING

14 O-RING

15 O-RING

16 EXHAUST COVER

17 RETAINING RING

18 DIFFERENTIAL SPRING (IF USED)

*Crack pressure is the amount of control

pressure required by the valve to initiate

air delivery. For crack pressures other

than 4 psi, a differential spring is used

in the assembly to produce the required

valve response.

(Models designed to have a 4 psi crack

pressure do not require a differential spring.)

PRIMARY CONTROL

PORT 1/4 NPT

SECONDARY

CONTROL PORT

1/4 NPT

CAP SCREW

CAP

SCREW

DIFFERENTIAL SPRING

(CONTROLS CRACK PRESSURE*)

(NOT REQUIRED FOR MOST

MODELS.

SEE BELOW)

VERTICAL

DELIVERY

PORTS

SUPPLY

PORT

HORIZONTAL

DELIVERY

PORTS

DIFFERENTIAL SPRINGS

Figure 8 – Bendix®R-12DC®Exploded View

9. Remove and discard the following parts:

a. Exhaust cover assembly (16)

b. O-rings (14 & 15)

c. Spring (13)

d. Inlet/exhaust valve (11)

e. Retainer (12)

4. Remove and discard the sealing ring (7) from the cover

(1), and mounting bracket.

5. Remove the piston (9) from the body (10) and retain for

reuse.

6. Remove and discard the o-ring (8) from the piston (9).

7. Depress and hold the exhaust cover assembly (16)

and remove and discard the retaining ring (17) from

the valve body (10).

8. Slowly release the holding force on the exhaust cover

assembly (16) to relax the spring.

CLEANING AND INSPECTION

1. Wash all metal parts in mineral spirits and dry them

thoroughly.

(Note: When servicing the Bendix®R-12DC®valve, all

springs and all rubber parts should be replaced.)

2. Inspect all metal parts for deterioration and wear, as

evidenced by scratches, scoring and corrosion.

3. Inspect the exhaust valve seat on the relay piston for

nicks and scratches which could cause excessive

leakage.

4. Inspect the inlet valve seat in the body for scratches

and nicks, which could cause excessive leakage.

5. Inspect the check valve seat in the R-12DC valve cover

and make sure all internal air passages in this area are

open and clean and free of nicks and scratches.

6. Replace all parts not considered serviceable during

these inspections and all springs and rubber parts. Use

only genuine Bendix replacement parts, available from

any authorized Bendix parts outlet.

ASSEMBLY

Note: All torque specied in this manual are assembly

torque and can be expected to fall off slightly after

assembly. Do not re-torque after initial assembly torque

fall. For assembly, hand wrenches are recommended.

Prior to assembly, lubricate all o-rings, o-ring bores and

any sliding surface with a silicone lubricant equivalent to

Dow Corning®#10.

Wash all remaining parts in mineral spirits and dry thoroughly.

Using the lubricant provided in this kit, lightly lubricate all

o-rings, o-ring grooves, body bores and sliding surfaces.

1. Install o-rings (14 & 15) in the exhaust cover assembly

(16).

2. Install o-ring (8) on piston (9).

3. Install sealing ring (7) on cover (1).

4. Install retainer (12) on the inlet/exhaust valve (11) and

insert both in the body (10).

5. Install spring (13) in the body (10).

6. Install exhaust cover assembly (16) in the body (10).

Depress and hold the exhaust cover assembly in the

body.

7. Install retaining ring (17) in the body (10). Make certain

the retaining ring is completely seated in the groove in

the body.

8. Install piston (9) in the body (10).

9. Install o-ring (5) on double-check cover (6), install spring

(2), guide (3) and double-check diaphragm (4) in cover

(1). Install cover (1) and torque torx head screws to

80–100 in-lbs.

10. Referring to the marks made during disassembly, install

cover (1).

11. Install the mounting bracket (not shown) on the cover

(1).

12. Install the four cap screws in the cover (1) and torque

to 80–100 in-lbs.

13. Test the valve as outlined in the Operational and

Leakage Test section before returning the valve to

service.

INSTALLATION

1. Clean the air lines.

2. Inspect all lines and/or hoses for damage and replace

as necessary.

3. Install the valve and tighten the mounting bolts.

4. Connect the air lines to the valve (plug any unused

ports).

5. Test the valve as outlined in Operational and Leakage

Tests.

OPERATIONAL AND LEAKAGE TEST

1. Chock the wheels, fully charge the air brake system

and adjust the brakes.

2. Make several brake applications and check for prompt

application and release at each wheel.

3. Check for inlet valve and o-ring leakage. Make this

check with the service brakes released. Coat the

exhaust port and the area around the retaining ring

with a soap solution; leakage of a one inch bubble in

three seconds is permitted.

4. Check for exhaust valve leakage. Make this check with

the service brakes fully applied. Coat the outside of

the valve where the cover joins the body to check for

seal ring leakage; no leakage is permitted.

If the valves do not function as described above, or if

leakage is excessive, it is recommended that the valves

be replaced with new or remanufactured units or repaired

with genuine Bendix parts, available at any authorized

Bendix parts outlet.

Log-on and Learn from the Best

On-line training that's available when you are 24/7/365.

Visit www.brake-school.com.

Table of contents

Other BENDIX Control Unit manuals

BENDIX

BENDIX RE-4 RELAY EMERGENCY VALVE User manual

BENDIX

BENDIX R7 VALVE 3-04 SPANISH Instruction Manual

BENDIX

BENDIX QR-L INLINE QUICK RELEASE VALVE User manual

BENDIX

BENDIX SR-5 TRAILER SPRING BRK VALVE User manual

BENDIX

BENDIX QRV QR-1 QUICK RELEASE VALVES Service manual

BENDIX

BENDIX TP-3 Mounting instructions

BENDIX

BENDIX R-12DC DBL CHECK RELAY VALVE User manual

BENDIX

BENDIX DV-2 Mounting instructions

BENDIX

BENDIX MV-3 DASH CONTROL MODULE User manual

BENDIX

BENDIX R-6 RELAY VALVE User manual

BENDIX

BENDIX SR-2 TRAILER SPRING BRAKE VALVE User manual

BENDIX

BENDIX PRESSURE PROTECTION VALVES User manual

BENDIX

BENDIX RV-1 PRESSURE REDUCING VALVE User manual

BENDIX

BENDIX R-8 RELAY VALVE User manual

BENDIX

BENDIX ATR-2 ANTILOCK TRACTION VALVE User guide

BENDIX

BENDIX PP-1-2-5-8-RD-3 PUSH-PULL VALVES User manual

BENDIX

BENDIX SS-1 SHUT OFF VALVE User manual

BENDIX

BENDIX RV-4 PRESSURE REDUCING VALVE Operating and maintenance instructions

BENDIX

BENDIX TC-7 TRAILER CONTROL BRAKE VALVE User manual

BENDIX

BENDIX R-12-R-14 RELAY VALVES User manual

BENDIX

BENDIX M-40QR Mounting instructions

BENDIX

BENDIX TW-12 User manual

BENDIX

BENDIX E-10 Mounting instructions

BENDIX

BENDIX E-7 DUAL BRAKE VALVE User manual

Popular Control Unit manuals by other brands

Festo

Festo Compact Performance CP-FB6-E Brief description

Elo TouchSystems

Elo TouchSystems DMS-SA19P-EXTME Quick installation guide

JS Automation

JS Automation MPC3034A user manual

JAUDT

JAUDT SW GII 6406 Series Translation of the original operating instructions

Spektrum

Spektrum Air Module System manual

BOC Edwards

BOC Edwards Q Series instruction manual

KHADAS

KHADAS BT Magic quick start

Etherma

Etherma eNEXHO-IL Assembly and operating instructions

PMFoundations

PMFoundations Attenuverter Assembly guide

GEA

GEA VARIVENT Operating instruction

Walther Systemtechnik

Walther Systemtechnik VMS-05 Assembly instructions

Altronix

Altronix LINQ8PD Installation and programming manual

Eaton

Eaton Powerware Series user guide

WAGO

WAGO 750-407/040-000 manual

Sony

Sony CCU-590 Operation manual

Graco

Graco 25D614 instructions

Task Force Tips

Task Force Tips YE-RF-900 Instructions for installation, safe operation and maintenance

Shini

Shini SPV-U Series manual