Owner's manual

Series 322 Load Unit
82
Maintenance
Use the following guidelines to determine when maintenance is required.
• Check the precharge pressure at periodic intervals. The length of time
between checks depends on how the system is used. Some factors to
consider when establishing this time interval are operating frequency,
displacement, and duration. Start with one month intervals until you
determine another interval is more appropriate.
• Maintain a log book on the condition of the precharge at each check. Use
this data to determine if the time between checks should be increased or
decreased and if maintenance is required.
• Because the precharge pressure level varies with a temperature change, the
level should always be checked at the same temperature. If it is not, use one
of the following formulas to determine if the precharge level is acceptable.
Degrees Celsius:
Degrees Fahrenheit:
• If a pressure line accumulator has a pressure level change of ±1.4 MPa (200
psi) between checks, the accumulator requires maintenance or the time
interval between checks needs to be shortened.
• If a return line accumulator has a change of ±50% of the original pressure
level between checks, the accumulator requires maintenance or the time
interval between checks needs to be shortened.
• If the precharge pressure level increases at each check interval, this indicates
that fluid is collecting on the gas side (a small amount of fluid leakage is
normal). When the precharge pressure level cannot be maintained within the
limits, remove the fluid and charge the accumulator. If the levels are again
exceeded at the first check interval, replace the piston seals after the initial
fluid has been changed.
• If the precharge pressure level decreases at each check interval, this
indicates gas leakage to the fluid side. When the precharge pressure level
cannot be maintained within the limits stated in the previous guidelines,
replace the accumulator piston seals.
• During normal operation, the accumulator piston should be near the center
of the accumulator cylinder. To check the approximate piston location, note
the warm-to-hot transition point on the accumulator cylinder wall during
operation. If the piston is near the charging stem end, the accumulator may
need charging. If the piston is at the other end, the accumulator may have an
excess charge, or more likely an excessive amount of hydraulic fluid has
collected in the gas chamber.
current pressure original pressure
273 current temperatrure()+
273 original temperature()+
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×=
current pressure original pressure
460 current temperatrure()+
460 original temperature()+
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×=