For Units Employing Only the Internal
Spring-Applied Load Holding Brake
An emergency load lowering condition exists when a
load is suspended and the hydraulic power supply to
the hoist has been disabled for some reason.
The following procedure releases the multiple disc
brake while leaving the brake valve closed. Since gear
type motors are not zero leakage devices, internal
motor leakage permits the load to slowly rotate the
motor although its outlet is blocked by the closed brake
valve. This procedure will
NOT
work if there is little or no
oil in the motor. Using properly rated pipe and fittings
the standpipe described below may be permanently
installed in the hydraulic system to avoid installing one
in an emergency.
The standpipe is simply a length of pipe (approximately
12 inches (305 mm long) attached to a 90° elbow. The
other end of the elbow is attached to a short nipple and
fitting suitable for mounting to the motor port or mani-
fold. The standpipe is installed with the standpipe point-
ing up in a vertical position. While the load is being low-
ered, oil
MUST
be added to the standpipe as necessary
to prevent the motor from running dry.
1. Remove the lock wire on the needle valve handle
and close the valve tightly.
2. Remove the plug in the tee.
3. Remove both main hoses from the motor and attach
a standpipe to the motor port on the opposite side of
the motor from the brake valve.
NOTE:
This port
may be fitted with a manifold.
4. Fill the standpipe with hydraulic oil, making certain
that oil is not running out of the brake valve. If oil is
running out of the brake valve, stop the emergency
lowering procedure. Remove the spring retainer and
tap the main spool of the brake valve to the closed
position. Replace the spring retainer. If the main
spool was stuck in the open position, after complet-
ing the emergency lowering procedure, the brake
valve
MUST
be repaired or replaced.
5. Connect a hand pump to the opening in the tee.
6. Operate the hand pump up to about 1,000 psi (6,900
kPa). A suspended load will slowly come down.
Releasing the pressure on the hand pump will cause
the load to stop. If a chattering noise is heard while
the load is coming down, increase the pressure until
the noise stops.
DO NOT
exceed 1,500 PSI (10,350
kPa) to the brake release port.
7.
Always
inspect the brake plates for signs of over-
heating and replace if necessary following this pro-
cedure. Refer to the service section of this manual
for details.
8. If this procedure was performed due to a malfunction
of the hoist, remove the hoist from service and per-
form a teardown and inspection to correct the cause
of the malfunction before returning the hoist to serv-
ice.
For Units Employing the Auxiliary Brake
System
An emergency load lowering condition exists when a
load is suspended and the hydraulic power supply to
the hoist has been disabled for some reason.
Equipment required for this procedure is as follows:
- (2) hand pumps
Note: Two (2) hand pumps will be required for
this procedure. One should be equipped with
-4 JIC adapters, and one should be equipped
with -6 JIC adapters.
- A stand-pipe will be installed on the lowering port of
the hoist as described in the previous section.
- Common hand tools and approximately 10 gallons
(39 l) of hydraulic oil in a container or funnel that can
be easily poured into the stand-pipe.
- Drain pans and absorbent material to contain
spilled oil.
1. Remove the pilot hose from the release port of the
ABS housing.
2. Install the hydraulic hand-pump with the -6 adapters
to the open release port of the ABS housing. With
20
EMERGENCY LOWERING PROCEDURES
The standpipe defined above
MUST
be used.
Attempting this procedure with no oil in the motor or
with the brake valve stuck in the open position will
cause the load to free fall, which could result in prop-
erty damage, personal injury or death.
Do not touch the motor, brake valve or standpipe
while lowering a load. They may become hot enough
to cause burns.
