Vilter VSM 71-701, Руководство по эксплуатации и обслуживанию

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Operation
the temperature controller adjusts the speed
of the pump/motor combination to maintain
a constant oil temperature.
NOTE:
See separate V-PLUS
®
instruction manual for
detailed start-up and operation.
4. Thermosyphon Oil Cooling
Using a brazed plate or an one pass shell
and tube type vessel, similar to the water
cooled oil cooler, oil is circulated on the shell
side and liquid refrigerant from the receiver
is
circulated through the tubes.Thermosyphon
systems use a 3-way temperature sensing
control valve to regulate oil at 120°F. Oil is
bypassed around the thermosyphon oil cooler.
When oil is higher than 120°F, the oil is
passed through the thermosyphon oil cooler.
A 1/4” tubing line w/valve adds high pres-
sure gas to the oil to quiet the sound of injec-
tion. Open this valve in small amounts, until
noise subsides.
The closed type cooling circuit is free from
the fouling problems associated with open
circuit water cooling. Since the oil cooling
load is rejected in the condenser, this type of
cooling is practical. The temperature limits
here are the same as those regarding the
water cooled oil coolers.
II. CONTROL SYSTEM
Equipped for automatic operation, the screw com-
pressor unit has safety controls to protect it from
irregular operating conditions, an automatic start-
ing and stopping sequence, capacity and volume
ratio control systems.
Check all pressure controls with a remote pres-
sure source, to assure that all safety and operat-
ing control limits operate at the point indicated
on the microprocessor.
The unit can be equipped with optional block and
bleed valves that are used to recalibrate the pres-
sure transducers. To use the block and bleed
valves to recalibrate the pressure transducers, the
block valve is shut off at the unit and the pressure
is allowed to bleed off by opening the bleed valve
near the pressure transducer enclosure. The trans-
ducer can then be calibrated at atmospheric pres-
sure (0 psig), or an external pressure source with
an accurate gauge may be attached at the bleed
valve.
The discharge pressure transducer cannot be iso-
lated from its pressure source, so it is equipped
with only a valve to allow an accurate pressure
gauge to be attached and the pressure transducer
calibrated at unit pressure.
Recheck the transducers periodically for any drift
of calibration.
A. Screw Compressor Control And
Operation
1. Starting, Stopping and Restarting
the Compressor
Before the screw compressor unit may start,
certain conditions must be met. All of the
safety setpoints must be in a normal condi-
tion, and the suction pressure must be above
the low suction pressure setpoint to assure
that a load is present. When the “On-Off”
switch or “Manual-Auto” button is pressed,
the oil pump will start. When sufficient oil
pressure is built up and the compressor ca-
pacity control and volume ratio slide valves
are at or below10%, the compressor unit will
start.
If the compressor is in the automatic mode,
it will now load and unload and vary the
volume ratio in response to the system de-
mands.
Stopping the compressor unit can be accom-
plished a number of ways. Any of the safety
setpoints will stop the compressor unit if an
abnormal operating condition exists. The
compressor unit “On-Off” or stop button will
turn the compressor unit off as will the low
pressure setpoint. If any of these conditions