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8.5 Performance Check of
Relief Valve
8. PERIODIC MAINTENANCE [Relief Valve, Capacity Control System]
q Set Discharge Pressure to 0.69 MPa.
w Open the front door and pull up the ring of the
relief valve by the hand.
e If the compressed air comes out, release your
hand from the ring.
8.6 Performance Check of
Capacity Control System
8.6.1 In case of P-type and I-type control
(For S-type, no P-type control is available.)
q By closing the Stop Valve on the discharge side
gradually until its pressure reaches to the speci-
fied pressure level, the Integral Unloader actu-
ates and discharges the compressed air from the
Oil Separator out into the ambient air.
w If the Integral Unloader actuates, make Stop
Valve on the discharge side full-close immedi-
ately.
e Check if inner pressure in the Separator is
settled within 0.2 to 0.34MPa.
r Fully open the Stop Valve on Discharge side
and check if the Load returns to the former
pressure level.
8.6.2 In case of U-type Control
q Adjust the Stop Valve so that the discharge
pressure reaches to its specified level.
w By closing the stop valve gradually, and check
if the discharge pressure settles within the
range specified in the table below.
e In case where discharge pressure exceeds the
range of the table below, or if the relief valve
actuates, adjustment of the capacity control
equipment is required. Ask your dealer or
Hitachi Service Station.
If its reservoir capacity on the discharge side is less
than 40 liters, pressure in the Separator returns to the
Load which the Separator had before its reaching to the
stable pressure.
Note) For 37 kW type, two relief valves are equipped
0.69 0.83
0.76to0.80 0.87to0.90
MPa
MPa
Specified
Discharge Pressure
Full-Close
Discharge Pressure
NOTE (1) means standard specifications.
(2) Do not select U-type control for 0.92 MPa
discharge pressure model.
Do not place your face near Relief Valve when
to check its performance. Compressed air
can come out and it is dangerous.
WARNING
Pull up
Ring
Relief Valve
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