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8. Maintenance Procedure
8.1 Troubleshooting
Problem
1． Incorrect pressure is being used.
2． Strainer [26] is clogged.
3． Foreign matter exists between
Pressure does not
4． Piston ring [14] is damaged.
reach the desired
5． Nominal size is too small for the
value.
6． Pressure is not adjusted correctly.
7． Strainer installed before pressure
8． Pressure gauge is faulty.
9． Operating air pressure is being in-
1． Foreign matter exists between
2． Foreign matter exists between
Reduced
pressure
raises above than
3． Foreign matter exists between
the specified value.
4． Trap is not provided for dead-end
5． By-pass valve is leaking.
6． Diaphragm [5] is damaged.
1． Nominal size is too large for the
2． Pressure reducing ratio is too large.
3． Drainage problem is caused.
Abnormal noise is
4． An abrupt OPEN/CLOSE valve is
heard.
5． Outlet pipe is too small.
Other
1． Springs and diaphragm are worn.
l Foreign matter and scales in a pipe may cause most of problems of pressure reducing valve. Be
careful sufficiently to foreign matter in a pipe.
l Phenomenon alike valve trouble may happen by fault of pressure gauge, fluid leakage from by-
pass valve, forgetting to close the by-pass valve, clogging strainer, and etc. First, check the said
particulars before above troubleshooting.
l Consult factory when cannot make a judgement whether parts need replacement or not.
Cause
piston [12] and cylinder [13].
specifications.
reducing valve is clogged.
sufficient.
main valve [9] and main valve seat
[11], or scratches exist.
pilot valve [17] and pilot valve seat
[18], or scratches exist.
piston [12] and cylinder [13].
line.
specifications.
located too close to the pressure
reducing valve.
1． Correct the pressure.
2． Disassemble and clean the strainer.
3． Disassemble and remove the foreign
matter. When any scratches are
identified, polish them away using a
paper. Change the parts if scratches
still exist after polishing.
4． Replace the piston ring.
5． Change the nominal size appro-
priately.
6． Observe the adjustment procedures
and readjust pressure.
7． Disassemble and clean it.
8． Replace it.
9． Raise the operating air pressure to
necessary set pressure.
1． Disassemble and remove the foreign
matter. When any scratches are
identified, lap the main valve and
main valve seat. Change the parts if
scratches still exist after lapping.
2． Disassemble the pilot valve as-
sembly, and clean or replace it.
3． Disassemble and remove the foreign
matter. When any scratches are
identified, polish them away using a
paper. Change the parts if scratches
still exist after polishing.
4． Install a trap.
5． Repair or replace it.
6． Replace the diaphragm.
1． Change the nominal size appro-
priately.
2． Reduce pressure in two stages.
3． Install a trap.
4． Allow as much as possible between
the valves.
5． Select a pipe size that will produce a
flow velocity of 30m/s or less.
1． Replace the springs and diaphragm.
‑9‑
Solution
■EPDT-101■
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