070.750-IOM (MAY 2018)
Page 6
HPSH Rotary Screw Compressor
Installation - Operation - Maintenance
OIL PUMP (OPTIONAL)
A demand oil pump is required for low differential pressure
applications (CoolWare will provide a warning when the
oil differential pressure is too low). Oil being supplied to
the compressor from the oil separator is at system dis-
charge pressure. Within the compressor, oil porting to all
parts of the compressor is vented back to a location in the
compressor’s body that is at a lower pressure than com-
pressor discharge pressure. All oil entering the compressor
is moved by the compressor rotors, out the compressor
outlet, and back to the system oil separator.
CONSTRUCTION DETAILS
HOUSING: All HPSH screw compressor castings are 60-40-
18 ductile iron to ensure structural integrity and mechanical
and thermal stability under all operating conditions.
ROTORS: The rotors are made from quality, wear-resistant
rolled steel to the exacting tolerances of the latest industry
standard asymmetric prole. The six-lobed male rotor is
directly connected to the driver. The eight-lobed female ro-
tor is driven by the male on a thin oil lm.
BEARINGS: Antifriction bearings with L10 rated life in excess
of 50,000 hours (using Frick SuperFilters™) at design condi-
tions are used for reduced frictional horsepower and supe-
rior rotor positioning, resulting in reduced power consump-
tion. Cylindrical roller bearings are provided to handle the
radial loads and the thrust loads are absorbed by preloaded
angular contact ball bearings (ACBB).
BALANCE PISTON: The male rotor is equipped with a bal-
ance piston to reduce load on the male axial bearing. Oil
pressure provides the force and therefore shall be within
limits of discharge pressure, 1.5 bar (22 psi) below and 3.3
bar (50 psi) above discharge pressure.
Shaft Seal: The compressor shaft seal is a single-face bal-
anced type with a spring-loaded, silicon carbide stationary
hardened surface riding against a rotating seat. Carbon and
graphite added provide self lubrication. During operation it
is vented to low pressure to provide extended life.
UNLOADING VALVE: Reduced current (power) requirement
at start-up is achieved by use of a plug valve. The plug valve
reduces torque by approximately 10%. Also, the plug valve
provides overload protection in more situations: power
overload, low oil pressure, low compression ratio, and high
internal compression.
MOTOR MOUNT: The HPSH series is designed with a drive-
end ange that mates with a cast iron motor mount (avail-
able as a sales order option). The motor mount is precision
machined so that it ensures proper alignment of the com-
pressor and motor coupling.
DESIGN LIMITS
Please use CoolWare™ to determine the limits for a spe-
cic application.
NOTES FOR DESIGN LIMITS:
(1) The HPSH 1510 compressor has minimum viscosity
requirements as shown in Fig. 4 to maintain proper
bearing lubrication. Consideration must be given to
viscosity changes due to refrigerant or gas dilution.
Figure 4 - Requirement for Viscosity as function of speed
(2) Maximum discharge temperature depends on oil type
used - normally 150°C (300°F). Please see Frick oil
data for more detail.
(3) In applications using miscible oil types POE and PAG,
it is extremely critical to keep water content to the
lowest possible to avoid corrosion and formation of
acids. The installation must have large lter dryers
with replaceable elements that can be effectively
serviced and vacuum dried before being put back in
service.
(4)
If the temperature difference becomes greater than or
equal to 140°C (250°F) between suction and discharge
- the plug valve must be unloaded immediately.
(5) For heat pumps, it is often practical to select an oil
temperature that equals condensing temperature.
VIBRATION AND SOUND DATA
The rotors balance grade is G 2.5 according to ISO 1940.
The male rotor drive end has a keyway and has been bal-
anced with a half key in the keyway, to be considered as a
round, full body shaft.
Reference Frick publication 070.902-IB for vibration sever-
ity limits.
Male rotor, # of lobes 6 Main Exciting
Frequencies (Hz)
Female rotor, # of lobes 8
Driver Speed, rpm Typical
Exiting Member / Event 3000 3600 4200 6000
Male rotor, rotational, 1st order 50 60 72 100
Male rotor, rotational, 2nd order 100 120 144 200
Female rotor, rotational, 1st 37.5 45 54 75
Female rotor, rotational, 2nd 75 90 108 150
Discharge gas pulsation, 1st 300 360 432 600
Discharge gas pulsation, 2nd 600 720 864 1200
Vibration level on the package can be higher, especially on
piping elements and when the natural frequency of an ele-
ment falls together with one of the exciting frequencies. If
the vibration level gets too high, a skip frequency function
in the control system shall be activated. When activated,
the motor will run through the critical speed very fast, not
causing any continuously high vibration.