3-13
Brake Accumulators
: Mounted under covers behind the operator’s seat. The brake
accumulators store hydraulic oil under pressure for use at the brake calipers. They are
bladder-type accumulators, and require a pre-charge pressure in the gas bladder. The
brake accumulator pre-charge pressure must be maintained on a monthly basis as follows:
1. Set park brake or put machine on outriggers. Turn off engine.
2. Pump the brake pedal several times to discharge stored oil pressure.
3. Remove the covers above the accumulators. If oil is found on the covers,
determine the source before proceeding.
4. Remove protective cap from the accumulator.
5. Connect a pressure gauge to the accumulator valve stem.
W A R N I N G
Accumulator pressure gauges will not detect accumulator pre-charge pressure if
improperly used. Carefully review pressure gauge and pre-charging instructions
included with commercially available gauge kits.
6. Measure accumulator gas pre-charge pressure. Nominal pressure is 1000 ± 100
psi (69 ± 6.8 bar).
W A R N I N G
NEVER use shop air or oxygen to pre-charge accumulators. ONLY use inert dry
nitrogen (N
2
) gas. Failure to use proper gas can cause accumulator damage or
failure, leading to property damage, injury, or death.
7. If necessary, add only dry nitrogen gas (N
2
).
C A U T I O N
Always replace caps and covers after pre-charging accumulators. In the event of a
leak, missing covers could allow high pressure oil to enter the operator’s
compartment. High pressure hydraulic oil can be injected into the skin, causing
serious injury.
8. Disconnect all gauges. Replace valve caps and covers.
If the accumulators are unable to hold a pre-charge pressure, or if the brakes fail to
operate properly, they may be damaged. The accumulator pressures should cycle
between 2175 psi (150 bar) and 2675 psi (184 bar). Accumulator bladder replacement
instructions and accumulator replacement instructions ship with replacement parts. In the
event that instructions are not included, contact BMC. Proper procedure is necessary to
prevent damage or premature failure of replacement parts.
Courtesy of Crane.Market
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