Initial Setting Of Omr Regulator - Hitachi NEXT Series Instruction Manual

Oil-free rotary screw air compressor
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6. STARTUP OPERATION [Initial Setting of OMR Regulator]

6.2 Initial Setting of OMR Regulator

① Set a control air pressure to a maximum level.
Example: If a control air pressure varies between
80 psi (0.55 MPa) and 95 psi (0.65 MPa),
maintain it at its maximum 95 psi
(0.65 MPa).
② Pull up the regulator knob, and then the regulator is
unlocked or settable.
Turn the regulator knob so that the pressure gauge
reads as follows:
③ The pressure gauge readings may increase/decrease
by 4 psi (0.03 MPa) as the control air pressure
decreases/increases by 15 psi (0.10 MPa),
respectively. Due to the regulator's characteristics,
the pressure gauge reading rises as the control air
pressure drops.
Standard Setting of Regulator
psi (MPa)
22 - 26 (0.15 - 0.18)
1. Maintain the pressure of a control air at the regulator setting value or more. If a control air pressure
of this level cannot be obtained, the ejector cannot operate and as a result, the gear case internal
pressure rises.
When the gear case internal pressure reaches approximately 196 Pa (20 mmH
valve opens to atmosphere to prevent excessive rise. This results in the venting of oil fume to
Therefore, if a control pressure cannot be maintained at the regulator setting, value, take
precautions to keep the air compressor from inhaling the oil fume back into the air intake.
2. If two or more air compressors are in parallel, the system may force a specific unit to unload for a
long period of time. The unloaded air compressors oil mist remover ejector may seldom operate,
thus opening its OMR relief valve frequently and venting oil mists to atmosphere. To solve this
problem, connect the unloaded air compressors control air pipe to an area in the plant air piping
system where pressure is consistently available, minimizing the amount of time the OMR relief valve
3. The OMR relief valve shortly opens when the air compressor starts and stops, even when control air
pressure is high. After repeated starts and stops, the OMR relief valve may ooze a slight amount of
oil. This is not unusual.
4. The oil mist remover consumes compressed air of approximately the value indicated above table.
The exact air consumption depends on the setting of the regulator.
5. Take precautions if the air compressor is used in AUTO operation mode, as the air compressor may
not stop automatically, due to the uninterrupted consumption of the compressed air by the oil mist
Air Flow Rate
cfm (liter/min)
Approx. 1.8
(Approx. 50)
④ Make sure that the vacuum indicator does not show a
red mark.
⑤ Make sure that there is no leak of the control air pipe
⑥ Press down the regulator knob to lock.
⑦ The oil mist remover makes the gear case internal
pressure negative during operation reducing the oil
pressure by 0.7 psi to 1.5 psi (0.005 to 0.01 MPa).
This is not abnormal. Reset the oil pressure on the
OMR relief valve.
⑧ Stop the air compressor. Make sure that the solenoid
valve is de-energized to the closed position and the
vacuum indicator shows a red mark.
O), the OMR relief

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