BENDIX R-8 RELAY VALVE Manual - Página 2

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BALANCED

The air pressure being delivered by the open inlet valve also

is effective on the bottom area of the relay piston. When this

delivery air pressure beneath the piston equals the service

air pressure above, the piston moves up slightly and the

inlet spring returns the inlet valve to its seat. The exhaust

remains closed as service line pressure balances delivery

pressure.

RELEASING

When air pressure is exhausted from the service port, the

diaphragm in the quick release moves, blocking the service

inlet and opening the exhaust of the quick release allowing

the air that was acting on the relay piston to be exhausted

at the quick release. When the air above the relay piston is

exhausted, the air beneath the piston will lift the piston and

the exhaust seat moves off the exhaust valve exposing the

exhaust passage to atmosphere. With the exhaust passage

open, the air pressure in the emergency or park actuators

exhausts out the exhaust port to atmosphere.

ANTI-COMPOUNDING (SIMULTANEOUS

SERVICE AND PARK APPLICATION)

In those applications where the R-8

control spring brake chambers, the anti-compound feature

may be utilized. With the anti-compound feature of the R-8

valve connected, a service application made while the vehicle

is parked is countered by a release of the parking brakes.

To utilize this feature, the exhaust cover of the quick release

portion of the R-8

valve is removed and a line is installed

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which is connected to the delivery of the service brake valve

or relay valve. With no air pressure at the service port of the

R-8

valve, the parking brakes are applied. If a service brake

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application is made, air from the service brake valve enters

the exhaust port of the quick release on the R-8

moves the diaphragm, blocking the service port. Air then

proceeds into the cavity above the relay piston, forces the

piston down, closing the exhaust and opening the inlet to

deliver air to the spring brake cavity as described under the

section of this manual entitled APPLYING.

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.

relay valve is used to

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valve and

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OPERATING AND LEAKAGE TEST

1. Check the wheels and fully charge the air system.

Adjust the brakes.

2. Apply and release the parking brakes several times and

check for prompt response of the brakes at all

appropriate wheels.

3. With the park control valve in the brakes "applied position",

coat the exhaust port with a soap solution to check for

inlet valve and o-ring leakage; a 1" bubble in 5 seconds

is permissible.

4. Place the park control valve in the "brakes released"

position and again check at the exhaust port for leakage

of the exhaust valve; a 1" bubble in 3 seconds is

permissible. Apply soap solution around the valve where

the cover joins the body to check for seal ring leakage;

no leakage permitted.

5. With the park control still in the brakes released position,

apply soap solution to the quick release exhaust port to

check the diaphragm exhaust seat; a 1" bubble in 3

seconds is permitted.

(NOTE: If the anti-compound feature is in use, the line

attached to the R-8

must be disconnected to perform this test.)

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

1. Block or hold the vehicle by means other than the

brakes.

2. Drain all air brake system reservoirs.

3. Identify, mark, and disconnect all air lines from the R-8

relay valve.

4. Remove the R-8

valve from its mount on the vehicle.

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(NOTE: The inlet and exhaust valve assembly, (generally

referred to as the insert) can be easily removed and

replaced. Remove the exhaust cover cap screws

and cover. Normally the insert can be removed

without disturbing the valve mounting or connecting

lines. CAUTION: DRAIN ALL RESERVOIRS

BEFORE ATTEMPTING TO REMOVE THE

INSERT.

DISASSEMBLY

1. Prior to disassembly of the R-8

relationship of the cover and body to facilitate assembly.

2. Remove the four 5/16" hex head cap screws and

lockwashers that secure the cover to the body and

separate the valve halves: remove the piston spring.

valve quick release exhaust

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valve, mark the

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