8.9 Inspection and Replacement of Minimum Pressure/Check Valve
8.9.1
Adjustment of Minimum
Pressure / Check Valve
Adjustment pressure is preset to 0.45 MPa at the deliv-
ery from the factory.
If some deviation occurs to the control pressure, read-
justment can be done by the following procedures.
① Open the valve at the compressor’s discharge side.
Set the unit to blow operation and check the pressure
by the oil separator tank internal pressure gauge.
② Remove the cap, fix the adjustment screw by a hexa-
gon wrench, then unfasten the lock nut.
③ Fastening the adjustment screw will increase the
control pressure, and unfastening will decrease.
④ When a specified pressure is obtained, fix the adjust-
ment screw again with a lock nut, then fasten the
cap again.
Element Head
Cap
Adjustment
Screw
Body
O-ring
Minimum
Pressure
Valve Piston
Z-ring
Check Valve
Spring
Check Valve
Piston
Lock Nut
Pressure
Control
Spring
8.9.2
Replacement of Minimum Pressure Valve
Piston / Check Valve Piston
①
Press the
STOP
button.
② Disconnect the power.
③ Close the stop valve on discharge side.
④ Open the front door and wait until the oil separator
tank internal pressure gauge reads 0 MPa.
⑤ Loosen a hexagonal portion of the minimum pres-
sure / check valve body by spanner. Do not unfas-
ten its lock nut portion, remove the body in whole
instead.
⑥ There are a pressure control spring, minimum pres-
sure valve piston, check valve spring, check valve
piston left on the element head side. Take the part
out and replace it with a new one, if required.
⑦ Clean if there is dirt inside the element head.
⑧ If there is stain on the sheet surface of the element
head side, clean it. Spread grease on the Z-ring por-
tion of the minimum pressure valve piston, or thinly
spread the lubricant (NEW
SCREW OIL NEXT)
over the piston sliding portion and sheet surface
O-ring portion of the check valve piston, and reas-
semble them.
⑨ At this time, make sure that the larger diameter side
of the check valve spring face down. As shown in the
figure in this page. Be careful about the mounting
direction of the check valve spring (broader surface
to its bottom).
If it is hard to loosen the body of the minimum pressure /
check valve when replacing, wait until the body reaches
cools to temperature.
Control pressure adjustment must be carried
out while the unit is in operation.
Therefore, ask your dealer or Hitachi regional
office for the work.
CAUTION
IMPORTANT
49
8. PERIODIC MAINTENANCE [Minimum Pressure/Check Valve]
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