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Piping The Air Compressor - Hitachi NEXT Series Instruction Manual

Oil-free rotary screw air compressor
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5. INSTALLING AND PIPING [Piping the Air Compressor]

5.4 Piping the Air Compressor

5.4.1 General Instructions
① Use the degreased pipe as a plant airline pipe.
② Install an isolation stop valve on the compressed air
outlet pipe (see figure below). Close the isolation
stop valve when stopping the air compressor.
Stop Valve
Discharge Air
③ Using flange joint to connect the air compressor to an
existing compressed air piping installation allows for
minimal disassembly of the enclosure panels (see
figure above).
④ If the plant compressed air piping installation is
extensive in length, using a larger diameter pipe
assists in lowering pressure drop throughout the
piping system.
⑤ If there is an area in the compressed air piping that
is concaved or vertical (see figure below), provide a
condensate drain valve at its bottom as a drip leg.
Condensate Drain Valve
Prevent the backflow of condensate from the plant
compressed air system back to the air compressor.
⑥ If the compressed air piping near the air compressor is
to be elevated, keep a space of 20inches (500mm)
between the elevated piping and the enclosure for ease
of maintenance (see figure below)
20inches or more
Stop Valve
⑦ If the air compressors discharge pipe is connected to
the main compressed air piping, run the discharge
up above the main compressed air piping and then
down into the top of the main compressed air piping
(see figure below). This prevents the backflow of
From air compressor
5.4.2 Parallel piping
Stop Valve
Air Receiver Tank
Stop Valve
Motorized isolation valve
If one air compressor is operated, close the stop valve
of the stopped air compressor. For automatic operation,
such as lead/lag and multi unit controlled, replace the
stop valve to an optional motorized isolation valve.
Ensure that the motorized isolation valve is closed
while the compressor is not running. If you use a
solenoid valve as the automatic stop valve, consult your
Hitachi distributor or local Service Station given on the
rear cover.
Contact the local HITACHI distributor/master dealer
or representative office for more detail.
As shown in the figure above, when one compressor is
operating and the other is stopped with opening the stop
valve, back pressure is applied to the aftercooler and
check valve of the stopped air compressor. This may
cause more condensate going into the air compressor
and more rusting of aftercooler and check valve.
Main compressed air pipe
Motorized isolation valve
Operating DSP
Non-Operating DSP

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