3
BALANCED: NO. 2 OR SECONDARY CIRCUIT
When the air pressure on the delivery side of the relay
piston (20) approaches that being delivered on the primary
side of the relay piston, the relay piston moves closing the
secondary inlet valve and stopping further fl ow of air from
the supply line through the valve. The exhaust remains
closed as the secondary delivery pressure balances the
primary delivery pressure.
When applications in the graduating range are made, a
balanced position in the primary circuit is reached as the
air pressure on the delivery side of the primary piston (22)
equals the effort exerted by the driver’s foot on the treadle.
A balanced position in the secondary portion is reached
when air pressure on the secondary side of the relay piston
(20) closely approaches the air pressure on the primary
side of the relay piston.
When the brake treadle is fully depressed, both the primary
and secondary inlet valves remain open and full reservoir
pressure is delivered to the actuators.
RELEASING: NO. 1 OR PRIMARY CIRCUIT
With the brake treadle released, mechanical force is
removed from the spring seat (26), graduating spring (23),
and primary piston (22). 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: NO. 2 OR SECONDARY CIRCUIT
With the brake treadle released, air is exhausted from the
primary circuit side of the relay piston (20). Air pressure
and spring load move the relay piston, opening the second-
ary exhaust valve, allowing air pressure in the secondary
delivery line to exhaust out the exhaust port.
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 E-8P
™
or E-10P
™
valve should be inspected every 6
months or 1500 operating hours, whichever comes fi rst,
for proper operation. Should the E-8P
™
or E-10P
™
valve
not meet the elements of the operational tests noted in this
document, further investigation and service of the valve
may be required.
Visually check for physical damage to the brake valve such
as broken air lines and broken or missing parts.
OPERATION
- Refer to Figure 3
APPLYING: NORMAL OPERATION - NO. 1 OR
PRIMARY CIRCUIT PORTION
When the brake treadle is depressed, the plunger exerts
force on the spring seat (26), graduating spring (23), and
primary piston (22). 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 to fl ow out the No. 1 or
primary delivery port.
APPLYING: NORMAL OPERATION - NO. 2 OR
SECONDARY CIRCUIT
When the primary inlet valve (33) is moved off its seat, air
is permitted to pass through the bleed passage and enters
the relay piston cavity. The air pressure moves the relay
piston (20), which contains the exhaust seat, and closes the
secondary exhaust valve. As the secondary exhaust valve
closes, the inlet valve (13) is moved off its seat allowing the
secondary air to fl ow out the delivery of the same circuit.
Because of the small volume of air required to move the
relay piston (20), action of the secondary circuit of the valve
is almost simultaneous with the primary circuit portion.
APPLYING: LOSS OF AIR IN THE NO. 2 OR
SECONDARY CIRCUIT
Should air be lost in the No. 2 or secondary circuit, the No.
1 or primary circuit will continue to function as described
above under
Normal Operation: No. 1 or Primary Circuit
Portion
.
APPLYING: LOSS OF AIR IN THE NO. 1 OR
PRIMARY CIRCUIT
Should air be lost in the primary circuit, the function will be
as follows: As the brake treadle is depressed and no air
pressure is present in the primary circuit supply and delivery
ports, the primary piston (22) will mechanically move the
relay piston (20), allowing the piston to close the second-
ary exhaust valve and open the secondary inlet valve and
allow air to fl ow out the secondary delivery port.
BALANCED: NO. 1 OR PRIMARY CIRCUIT
When the primary delivery pressure acting on the primary
piston (22) equals the mechanical force of the brake pedal
application, the primary piston (22) will move and the
primary inlet valve (33) will close, stopping further fl ow
of air from the primary supply line through the valve. The
exhaust valve remains closed preventing any escape of
air through the exhaust port.
