Frick SGXH-4021 - Oil System Requirements; Oil Pressure Requirements; Balance Piston Oil Requirements

070.650-IOM (JUL 19)
Page 26
SGC/SGX ROTARY SCREW COMPRESSOR
INSTALLATION
Once the compressor is rigged into place, its feet must be
shimmed to level it. There must be absolutely no stresses
introduced into the compressor body due to bolting of the
feetandanges.
The compressor motor mount is not designed to carry the
unsupported weight of the motor. The full motor weight
must be supported using the motor lifting point during the
motor installation process. After the necessary bracket
to support the motor have been welded into place on the
package and the rear motor feet and the motor mount
have been bolted into place, the weight of the motor can
rest on the support bracket and the motor mount.
In any screw compressor installation, support suction and
discharge lines in pipe hangers, preferably within 2 ft of
vertical pipe run, so that the lines won’t move if discon-
nected from the compressor. See Table 4 for Allowable
Flange Loads.
Table 4: Allowable ange loads
Noz. Moments (ft-lbf) Load (lbf)
size Axial Vert. Lat. Axial Vert. Lat.
NPS M
r
M
c
M
l
P V
c
V
l
1 25 25 25 50 50 50
1.25 25 25 25 50 50 50
1.5 50 40 40 100 75 75
2 100 70 70 150 125 125
3 250 175 175 225 250 250
4 400 200 200 300 400 400
5 425 400 400 400 450 450
6 1,000 750 750 650 650 650
8 1,500 1,000 1,000 1,500 900 900
10 1,500 1,200 1,200 1,500 1,200 1,200
14 2,000 1,800 1,800 1,700 2,000 2,000
CUSTOMER CONNECTIONS
Asaminimum,connecttothelocationsspeciedinFig-
ures 3 to 9, 26, and 27 in addition to suction and discharge.
Other connections are available for instrumentation, oil
return, and service as noted on the Dimensional Outline
drawing. The electrical connections for the slide stop and
the slide valve transmitters and the solenoid valve coils
must connect to your control system.
OIL SYSTEM REQUIREMENTS
Warning
Access valves in brass material must be removed and
the holes lled with steel plugs when package is as-
sembled.
Figure 15: Caution/Identication tag on access valve
The oil system must provide oil to the compressor within
limitation on:
• Oil selection
• Oil pressure
• Oil temperature
• Oil cleanliness
OIL SELECTION
The oil must be suitable for the application, refrigerant,
and operation condition. Compressor bearings require
a minimum viscosity based on size and speed (rpm). A
maximum viscosity of 100 cSt must not be exited.
FRICK compressor oils are recommended — refer to
160.802-SPC. Coolware provides FRICK oil properties and
information on viscosity requirements for a given com-
pressor selection.
OIL PRESSURE
Design the complete oil system so that the pressure does
notdropmorethan15psiwithacleanoillterelement.
This is critical for the proper function of the balance piston
and to ensure the life of the axial bearings. For low pres-
sure and low pressure differential operation, an oil pump
mustbebuilt-intoprovidesufcientoilpressure.
The control system needs to be capable of checking the
oil pressure and compare to both suction and discharge
pressures. In general, oil pressure must be a minimum of
1.5 times suction pressure plus 15 psi, and greater than
the discharge pressure minus 25 psi. For applications with
economizer and/or sideloading, the oil pressure must addi-
tionally be more than 15 psi above the pressure at the side
port when in operation.
Advanced control systems like the FRICK Quantum HD
monitor the oil pressure in many more ways in order to
keep the compressor running beyond these basic limits.
This advanced control keeps the compressor running
safely in partial load conditions.
See Oil Pump section for additional information.
BALANCE PISTON OIL REQUIREMENTS AND REGULA-
TIONS
All SG compressors have a balance piston on the male
rotor inlet end (see Figure 13). Oil is fed to the balance
piston to counteract a portion of the force of gas pressure.
For models using 193 mm to 283 mm rotors, the balance
piston oil feed is internal using the common oil connection
throughtheSB-3port(standardconguration).Aseparate
congurationisavailableforhighpressureoperation.On
355 and 408 compressors the oil is fed separately through
the SB-2 port (see Figure 14). Generally, 355 mm balance
piston regulation must meet requirements of CES 6605.
408 mm balance piston pressure must meet requirements
ofCES6607.Keeptheoilpressurewithinthespecied
range on all compressors.
added text " (standard
conguration).Aseparate
congurationisavailable"
for high pressure opera-
tion.