RWB II ROTARY SCREW COMPRESSOR UNITS
OPERATION
S70-200 IOM
Page 18
For high-stage packages, the cold-start valve is equipped
with a large spring that creates 30 psi of pressure in the oil
separator (above suction pressure), for lubrication of the
com pres sor.
DO NOT ATTEMPT TO SERVICE THE COLD START
VALVE. PLEASE CONTACT THE FRICK SERVICE
DE PART MENT.
Once the compressor is running it will begin to force gas to
the condenser at connection P2. As the condenser heats up
it will begin to rise in pressure as the compressor suc tion
pulls down in pressure. As soon as differential pres sure is
developed between the condenser and suction, these pres-
sures act across a piston inside the cold-start valve to par tial ly
overcome the spring force. When the differential pres sure
reaches and exceeds 30 psi, the piston fully over comes the
spring force and powers the valve fully open for very low
operating pressure drop.
For booster applications, the valve is equipped with a light er
spring which produces 15 psi oil pressure above suction
pres sure before it fully powers open.
The RWB II package is also equipped with a suction check
valve by pass. The oil separator will slowly bleed down to
sys tem suction pressure when the unit is stopped. This al lows
the compressor drive motor to have an easier start, and the
dis charge check valve will seat more tightly. See the "SUC-
TION CHECK VALVE BYPASS" section for op er a tion.
NOTE: For alarm descriptions and shutdown or cutout
pa ram e ters, see publication S90-010 O.
COLD START VALVE
DEMAND PUMP OIL SYSTEM
This system is designed to provide adequate compressor
lubrication for some high stage ap pli ca tions that operate with
low differential pres sure across the com pres sor suc tion and
dis charge and all booster applications.
During the period from start-up to normal operation the oil
pressure alarm and oil pressure cutout setpoints will vary
according to formulas built into the mi cro pro ces sor con trol
program.
NOTE: For alarm descriptions and shutdown or cutout
pa ram e ters, see publication S90-010 O.
COMPRESSOR OIL SEPARATION SYSTEM
The RWB II is an oil fl ooded screw compressor. Most of the
oil discharged by the compressor separates from the gas fl ow
in the oil charge reservoir. Some oil, however, is dis charged
as a mist which does not separate readily from the gas fl ow
and is carried past the oil charge reser voir. One or more
coalescer fi lter elements then COALESCE the oil mist into
droplets which fall to the bottom of the co a lesc er sec tion of
the oil separator. The return of this oil to the com pres sor is
controlled by a throttling valve on both high stage and boost er
applications (see Figure 19).
NOTE: Open throttling valve only enough to keep co-
a lesc er end of separator free of oil.
The sight glass located near the bottom of the coales cer sec-
tion of the oil separator should remain empty during nor mal
operation. If an oil level develops and remains in the sight
glass, a problem in the oil return separation sys tem or com-
pres sor operation has developed. Refer to MAIN TE NANCE
for information on how to correct the prob lem.
NOTE: Normal op er at ing lev el is mid way be tween the
top sight glass and bot tom sight glass.
OIL SEPARATION SYSTEM
Figure 18
Figure 19
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