Bendix E-7 DUAL BRAKE VALVE User Manual

®

Bendix® E-7™ Dual Brake Valve

SD-03-818

DESCRIPTION

The Bendix® E-7™ dual brake valve is a suspended,
pedal-operated type brake valve with two separate supply
and delivery circuits for service and emergency braking,
which provides the driver with a graduated control for apply­ing and releasing the vehicle brakes.

The circuits in the E-7
follows: The primary circuit portion is that portion of the valve
between the spring seat which contacts the plunger and the
relay piston; the secondary circuit portion is that portion
between the relay piston and the exhaust cavity .

The primary circuit portion of the valve is similar in operation
to a standard single-circuit air brake valve, and under nor­mal operating conditions the secondary circuit portion is
similar in operation to a relay valve.

The primary circuit portion of the valve is part of a removable
cage which also houses the relay piston and the cage which
can be removed without removing the entire brake valve.

Both primary and secondary circuit portions of the E-7
dual brake valve use a common exhaust protected by an
exhaust check valve.

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dual brake valve are identified as

MOUNTING

PLATE

SECONDARY

DELIVERY

SECONDARY

SUPPLY

PRIMARY

SUPPLY

PRIMARY

DELIVERY

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OPERATION

APPLYING: NORMAL OPERATION - PRIMARY
CIRCUIT PORTION

When the brake pedal is depressed, the plunger exerts force
on the spring seat, rubber graduating spring, and primary
piston. The primary piston which contains the exhaust valve
seat, closes the primary exhaust valve. As the exhaust valve
closes, the primary inlet valve is moved off its seat allowing
primary air pressure to flow out the delivery port.

APPLYING: NORMAL OPERATION ­SECONDARY CIRCUIT PORTION

When the primary inlet valve is moved off its seat, air is
permitted to pass through the bleed passage and enters the
relay cavity. The air pressure moves the relay piston, and
the relay piston, which contains the exhaust seat, closes
the secondary exhaust valve. As the secondary exhaust

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FIGURE 1 - E-7

DUAL BRAKE VALVE

valve closes, the secondary inlet valve is moved off its seat
allowing secondary air pressure to flow out the delivery port.
Because of the small volume of air required to move the
relay piston, action of the secondary circuit portion of the
valve is almost simultaneous with the primary circuit
portion.

APPLYING: LOSS OF AIR IN SECONDARY
CIRCUIT

Should air be lost in the secondary circuit, the primary
circuit portion will continue to function as described above
under Normal Operation: Primary Circuit Portion.

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APPLYING: LOSS OF AIR IN PRIMARY CIRCUIT

PREVENTIVE MAINTENANCE

Should air be lost in the primary circuit, the function will be
as follows: As the brake pedal is depressed and no air
pressure is present in the primary circuit supply and delivery
ports, the primary piston will mechanically move the relay
piston allowing the piston to close the secondary exhaust
valve and open the secondary inlet valve and allow air pressure
to flow out the delivery port.

BALANCED: PRIMARY CIRCUIT PORTION

When air pressure delivered to the brake actuators and air
pressure in the cavity on the delivery side of the primary
piston equals the mechanical force of the brake pedal appli­cation, the primary piston will move and the primary inlet
valve will close, stopping the further flow of air from the pri­mary supply line through the valve. The exhaust valve remains
closed preventing any escape of air through the exhaust
port.

BALANCED: SECONDARY CIRCUIT PORTION

When the air pressure on the secondary side of the relay
piston approaches that being delivered on the primary side
of the relay piston, the relay piston moves closing the sec­ondary inlet valve and stopping further flow of air pressure
from the supply line through the valve. The exhaust remains
closed as the pressures balance.

When applications in the graduating range are made, a bal­anced position in the primary portion is reached as the air
pressure on the delivery side of the primary piston equals
the effort exerted by the driver’s foot on the pedal. A bal­anced position in the secondary portion is reached when air
pressure on the secondary side of the relay piston closely
approaches the air pressure on the primary side of the relay
piston.

When the brake pedal is fully depressed, both primary and
secondary inlet valves remain open and full reservoir pres­sure is delivered out the delivery ports.

RELEASING: PRIMARY CIRCUIT PORTION

With the brake pedal released, mechanical force is removed
from the spring seat, rubber graduating spring, and primary
piston. Air pressure and spring load moves the primary pis­ton, opening the primary exhaust valve allowing air pressure
in the primary delivery line to exhaust out the exhaust port.

RELEASING: SECONDARY CIRCUIT PORTION

With the brake pedal released, air is exhausted from the
primary side of the relay piston. Air pressure and spring
load move the relay piston, opening the secondary exhaust
valve allowing air pressure in the secondary delivery line to
exhaust out the exhaust port.

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 E-7™ valve
should be inspected every 6 months or 1500 operating hours,
whichever comes first, for proper operation. Should the
E-7™ valve not meet the elements of the operational tests
noted in this document, further investigation and service of
the valve may be required.

Every 3 months, 25,000 miles, or 900 operating hours:

Lubricate fulcrum and roller pin with Barium grease per
BW-204-M (Bendix part 246671).

Free pedal travel should be checked as follows: Check to
be certain plunger is in contact with spring seat. The stop
button should be adjusted so that the roller and plunger just
contact.

Apply a thin layer of Barium grease, per BW-204-M (Bendix
part 246671), between plunger and mounting plate – do not

over oil!

Clean exhaust check depending on type of service.

SERVICE CHECKS

OPERATING

Check the delivery pressure of both primary and secondary
circuits using test gauges known to be accurate. Depress
the pedal to several positions between the fully released
and fully applied positions, and check the delivered pres­sure on the test gauges to see that it varies proportionately
with the movement of the brake pedal.

When the treadle is fully applied, the reading on the test
gauge should fall off to zero promptly when the application
is released. It should be noted that the primary circuit deliv­ery pressure will be about 2 psi greater than secondary circuit
delivery pressure with primary and secondary circuit supply
reservoirs at the same pressure. This is normal in this valve.

IMPORTANT

An increase in stopping distance or a low pressure warning
indicates a malfunction in one or the other brake circuit, and
although the vehicle air brake system may continue to func­tion, the vehicle should not be operated until the necessary
repairs have been made and both braking circuits are oper­ating normally .

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EXHAUST CHECK

VALVE

INLET-EXHAUST

ASSEMBLY (1)

RETAINER (17)

SCREW (21)

WASHER (22)

DIAPHRAGM (13)

PISTON SPRING (8)

RETAINER (20)

O-RING (7)

O-RING (6)

RETAINER (18)

RUBBER SPRING (10)

RUBBER SPRING SEAT (19)

O-RING (2)

O-RING (3)

RELAY SPRING (5)

INLET-EXHAUST

ASSEMBLY (4)

O-RING (11)

O-RING (9)

O-RING (12)

SPRING SEAT NUT (16)

STEM SPRING (23)

SPRING SEAT (15)

LOCK NUT (14)

MANIFOLD*

*OPTIONAL MANIFOLD FOR INSTALLATIONS

REQUIRING SUPPLY & DELIVERY LINE

CONNECTIONS ON ENGINE SIDE OF ENGINE

COMPARTMENT BULKHEAD.

PLUNGER FULCRUM PIN

ROLLER

SEALING

RINGS

STOP BUTTON

PEDAL

FIGURE 2 - E-7™ DUAL BRAKE VALVE

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