Series 111 Accumulators
Maintenance
15
Changing the Precharge Pressure
Often the precharge of an accumulator mounted on a hydraulic supply line
is increased to enhance system performance and reduce the transient HPS
flow demands. Accumulators may be precharged to 10 MPa (1500 psi) or
more, although amounts above 14 MPa (2200 psi) will have less and less
performance effect in most situations. Be sure that you read the following
warning before you charge your accumulator.
Accumulators have specific pressure ratings.
If the precharge pressure is too high, the accumulator can bottom out
causing the release of metal particles into the hydraulic fluid. Charging
accumulators above their rated level can damage system equipment.
Do not charge accumulators to pressures above their rated level. Charge
accumulators below their rated fatigue pressure of 21 MPa (3000 psi) for the
Model 111.11B and 22 MPa (3200 psi) for the Model 111.12C. Use a suitable
regulator and gage set to an accumulator’s charges.
Before you begin
Go to
“Checking the Accumulator Precharge”
on page 13 to determine if
you need to change the precharge pressure.
Decreasing pressure
Complete the following steps to decrease the precharge pressure.
1. Slowly open the bleed valve on the accumulator charging kit until gas
begins to escape. When the pressure reading on the appropriate
pressure gage drops to the level required, close the bleed valve.
2. Close the locknut (or close the chuck valve if you have a core-type
valve). Open the bleed valve on the accumulator charging kit and
remove the chuck valve from the accumulator.
3. Install the valve stem cap and protective cover.
Increasing pressure
Complete the following steps to increase the precharge pressure.
1. Close the locknut on the accumulator (or close the chuck valve for a
core-type valve).
2. Open the bleed valve two turns.
Mixing gases can produce unpredictable results.
Do not use another gas to precharge an accumulator.
Use only dry nitrogen gas to precharge accumulators.
3. Connect the nitrogen supply hose from the supply bottle pressure
regulator output to the input check valve on the charging kit.
WARNING
WARNING
