All BRADEN hoists employ a spring-applied, hydrauli-
cally released, multiple disc brake inside the hoist hous-
ing. This brake holds a suspended load when the direc-
tional control valve is in its neutral position, or when
hydraulic power is lost. An over-running brake clutch, or
sprag-type clutch assembly, permits the power train and
drum to rotate in the direction to lift a load, while the
brake remains fully applied. A load cannot be lowered,
however, without first applying hydraulic pressure to the
release port and releasing the brake.
Hoists ordered for personnel handling cranes will also
have a needle valve installed in the brake release line
and a tee fitting installed between the needle valve and
the brake release port on the hoist. One end of the tee
is capped. The needle valve is shipped in the open posi-
tion and held open with a lock wire. With the valve
closed and the cap removed from the tee, the brake is
now isolated from system pressure and vented to
atmosphere. The brake cannot be released under these
conditions by actuating the directional control valve.
BRAKE TEST PROCEDURE
(For Internal Spring-Applied Load Holding Brake)
"DR" PORT ON
COUNTERBALANCE
VALVE
"BR" PORT ON
COUNTERBALANCE VALVE
MOTOR CASE DRAIN
BRAKE RELEASE PORT ON WINCH
HOIST PORT
ON MOTOR
NEEDLE VALVE
The needle valve/tee combination serves (2) purposes:
1. Provides a means to test the brake.
2. Provides a means to lower a suspended load when power is lost.
18
Relative position of the needle
valve to other components and
fittings on the winch, motor and
counterbalance valve.
Brake Test Procedure (for API designated hoists):
NOTE: Brake test to be performed with no load on the
hoist. The weight of the wire rope, hook block and over-
haul ball or hook weights are acceptable.
NOTE: If the hoist is equipped with a ratchet and pawl
mechanism, the pawl lever
MUST
be disengaged from
the ratchet wheel by disconnecting the cylinder and
rotating the pawl lever
clear
of the drum and ratchet
wheel.
1. Remove the lock wire on the needle valve handle
and close the valve tightly.
2. Remove the cap from the tee in the brake release
circuit.
3. With the hydraulic power unit (HPU) running, move
the directional control valve handle slowly to the full
open, lowering position.
4. Increase the engine speed, if necessary, to bring the
system pressure up to the relief valve setting. The
hoist drum should remain stationary.
5. This procedure utilizes the hoist hydraulic motor to
test the brake's ability to resist approximately 115%
of the hoist rated capacity.
Once the brake test is completed, be sure to reinstall
the cap on the tee, fully open the needle valve and
replace the lock wire in the handle.
If the drum rotates or slips during the test, the hoist
should be disassembled and the brake should be exam-
ined for wear or damage. In addition, for hoists using
helical brake springs, the springs should be measured
for the correct free length.
Replace any parts exhibiting excessive wear, and any
spring whose length is outside the dimensions defined
in the manual. Reassemble the brake and hoist and
repeat the test.