MTS Series 505 SilentFlo Hydraulic Power Unit Model 505-11 - Manual (Page 71)

Precharging the Surge Suppressor Accumulator
Model 505.07/.11 SilentFlo™ HPU Accessories 71
A. Press the Start switch.
B. Run the HPU at low pressure for about three hours to filter the new
hydraulic fluid.
C. Run the HPU in high pressure to check for leaks.
D. Press the Stop button.
Precharging the Surge Suppressor Accumulator
It is normal for a small amount of surge suppressor precharge loss to occur during
operation. Because of this gradual reduction in precharge pressure, the pressure
should be checked and recharged (if necessary) at regular intervals.
Determining a
pressure check
interval
The precharge pressure checking intervals of your surge suppressor depends on
how your system is used. Vigorous use causes more rapid pressure loss and thus
requires checking and recharging more often.
Initially, check the surge suppressor precharge pressure every month or 160
operating hours. If the precharge pressure changes more than 200 psi during this
time period, recharge the surge suppressor and check the pressure twice as often
in the future. If the precharge pressure changes less than 200 psi, check the
pressure half as often.
When you have established a regular interval for checking the precharge
pressure, note the amount of pressure loss that occurs each time the pressure is
checked. An increase in pressure loss during the period between checks may
indicate that the surge suppressor seals or bladder require replacement.
Checking precharge
pressure
The nitrogen precharge should be about 50–60% of the output pressure. To check
the surge suppressor precharge:
1. Turn off the HPU and ensure that the pressure is at zero before proceeding.
2. Connect the charging kit chuck valve to the valve stem on the surge
suppressor, or to the remote charge valve on the reservoir top, if supplied.
3. With an open-end wrench, turn the locknut counterclockwise on the
accumulator valve assembly to open the valve. Read the pressure on the
high pressure gage.
• If the pressure reading is outside the range of 10.3–12.5 MPa (1500–
1800 psi), perform the procedure “Changing the precharge pressure.”
• If the pressure level is within the range of 10.3–12.5 MPa (1500–1800
psi), turn the locknut clockwise to close the valve and continue this
procedure.