Operation
Series 505G2 SilentFlo™ Hydraulic Power Unit 47
Recovering from an Interlock
This section describes how to reset each type of HPU interlock. If a fault occurs (Low Level, Over
temperature, Dirty Filter), the HPU will not start. You must determine the source of the interlock and
correct the cause before using the HPU.
If the Main screen is selected, the presence of a fault condition is evident by one of the fault or alarm
indicators and a blue Status indicator. Other indicators can be lit depending on the interlock.
Click on the Status button to display the Status screen and identify the fault conditions.
Hyd fluid low level
A low fluid level interlock is indicated on the Main screen by a red Faulted indicator, a red Oil Level
indicator, and a blue Status indicator. The interlock is generated when the hydraulic fluid falls below
the setting of the low level switch mounted through the top of the reservoir. Perform the following steps
to correct a low level interlock:
1. Determine the cause for the low fluid level and correct it.
2. Add hydraulic fluid to the reservoir until the sight glass on the side of the HPU indicates the
proper level.
3. Verify that the hydraulic fluid level sensor is detecting the proper fluid level.
4. Press Reset to clear the interlock and change the unit status back to normal.
Hyd fluid overtemperature
A hydraulic fluid overtemperature interlock is indicated on the Main screen by a flashing red Faulted
indicator, a blue Bypass indicator, a red Oil Temp indicator, and a blue Status indicator. The interlock
is generated when the temperature exceeds 55°C (131°F). The interlock will automatically shut down
the HPU. The HPU cannot return to normal operation until the fluid has cooled. Perform the following
to correct an overtemperature interlock:
1. Start cooling the hydraulic fluid by circulating hydraulic fluid through the heat exchanger
(Overtemp Bypass mode).
A. If necessary, press the Main button to select the Main screen.
B. Ensure that Module #1 Enabled is green.
C. Press the Bypass button. Pump module #1 will start and run to circulate the hydraulic
fluid through the heat exchanger. The red flashing Faulted indicator changes to
yellow Overtemp Bypass and the Bypass button changed to Stop.
2. If the there is no change in the Oil Temp reading after several minuets, determine if the
hydraulic fluid is receiving adequate cooling.
l The cooling water inlet temperature affects the efficiency of cooling the hydraulic fluid.
l Check the cooling water inlet-to-outlet pressure differential. It should be between
0.24–0.31 MPa (35–45 psi). If necessary, adjust the water pressure at its source.
3. After the displayed fluid temperature drops below 55°C (131°F), press the Stop button.
4. Press the Reset button to clear the interlock and turn the indicator off.
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