Bleeding - JLG 600A Service And Maintenance Manual

Bleeding

1. Install brake in system and connect pressure lines.
2. Bleed pressure release section of brake by pressurizing
side inlet port and allowing air to escape from top port.
Pressure should not exceed 100 psi (6.9 bar) during
bleeding.
PROBLEM
Brake slips Excessive pressure in hydraulic system
Oil in brake if designed for dry use
Disc plates worn
Springs broken or have taken a permanent set
Brake drags or runs hot Low actuation pressure
Bearing failure
Brake will not release Stuck or clogged valve
Bad o-rings
Discs frozen
3121201
Table 3-2. Troubleshooting
CAUSE
If there is back pressure in the actuation line of the
brake, holding torque will be reduced.
Wet linings generate 67% of the dry torque rat-
ing. If the brake has oil in it, check the type of oil
hydraulic or gearbox.
1. Gearbox oil
2. Hydraulic oil
The thickness of the disc stack sets the torque
level. A thin stack reduces torque.
Broken or set springs can cause reduced torque - a
rare occurrence.
The brake should be pressurized to minimum of
1.38 bar (20 psi) over the full release pressure
under normal operating conditions. Lower pres-
sures will cause the brake to drag thus generating
heat.
If the bearing should fail, a large amount of drag
can be generated.
Brakes are designed to come on when system
pressure drops below stated release pressure. If
pressure cannot get to brake, the brake will not
release.
If release piston will not hold pressure, brake will
not release.
These brakes are designed for only limited
dynamic braking. A severe emergency stop or pro-
longed reduced release pressure operation may
result in this type of damage.
SECTION 3 - CHASSIS & TURNTABLE
3. Apply sufficient pressure to release brake and check for
proper operation in system.
EXPLANATION
Check filters, hose size, restrictions in other
hydraulic components.
Replace oil seal in brake.
Check motor seal
Check piston seals
NOTE: Internal components will
Check disc thickness.
Check release pressure. (See spring replacement).
Place pressure gauge in bleed port & check pres-
sure with system on.
Replace bearing.
Place pressure gauge in bleed port - check for ade-
quate pressure. Replace inoperative line or com-
ponent.
Replace o-rings.
Replace disc stack.
ACTION
need to be inspected,
cleaned and replaced as
required.
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