Hitachi NEXT Series Instruction Manual page 42

5. INSTALLING AND PIPING THE DSP [Piping the DSP Air Compressor]
5.4.3 Motorized Isolation Valve
Pressure detecting pipe
(for VSD control model or Auto option)
Stop Valve
Motorized
isolation valve
The V type is equipped with an AUTO operation as a
standard function, and gets its structure from the second-
ary side of the motorized isolation valve.
Mount the pressure detecting pipe (customer supplied)
and motorized isolation valve (standard accessory).
Connect the pressure detecting pipe from the position on
the upper pipe, which is as close as possible to the sec-
ondary side of the motorized isolation valve, to the
receiver pressure detecting port of the compressor.
Also, avoid operating the equipment without mounting
the pressure detecting pipe. The safety valve actuates
because pressure is not detected.
IMPORTANT
As shown in the figure above, if the compressor is stopped
by the AUTO function, the motorized isolation valve closes.
If a motorized isolation valve is not mounted, back pres-
sure rises in the after cooler, check valve, etc., when the
compressor stops running. These conditions promote
drainage, and are contributing factors to rusting inside the
after cooler and early rusting of the check valve, etc.
40
Discharge
Air
Air Receiver Tank
5.4.4 Parallel Piping / Operation with a
Reciprocating Compressor
Stop Valve
IMPORTANT
(1) This is to prevent the reciprocating compressor's air
pulsation from affecting the DSP.
(2) Usually, continue to operate the DSP as long as possi-
ble and start and stop a reciprocating compressor in
parallel as required by the compressed air demand.
CAUTION
Do not install a check valve between the DSP
and the air receiver tank. Otherwise, the DSP
may hunt, that is, load and unload very fre-
quently ; the capacity control system may not
work normally.
Check Valve
Discharge Air
Stop Valve
Connect the DSP's
discharge pipe to the
secondary part of the
air receiver tank.