070.750-IOM2 (JAN 21)
Page 6
HPS 273 ROTARY SCREW COMPRESSOR
INSTALLATION - OPERATION - MAINTENANCE
• The HPS 273 compressor models are designed with
multiple ports, including:
–
Economizer port located at 1.32 Vi
–
Liquid injection port located at 1.25 Vi
–
Two main oil injection ports - SM2 (1.05 Vi ) for the
two lower Vi ranges (1.3 to 1.96 and 1.7 to 3.0) and
SM1 (1.3 Vi) for the 2.2 Vi to 5.0 Vi range
• All bearing and control oil is vented to lower pressure
locations inside the compressor allowing operation
without an oil pump for most applications.
• The shaft seal is designed with a seal ring made of
silicon carbide mated against a similar material, with
carbon and graphite added to the matrix to provide
self-lubrication, especially for startups.
The shaft seal housing is designed to maintain operat-
ing pressure on the seal much lower than discharge
pressure for increased seal life.
• Oil injected into the compressor is directed between
the rotor threads to maintain good volumetric and
adiabatic efficiency.
• The shaft rotation is clockwise when facing the com-
pressor drive end and is suitable for all types of drives.
Warning
Compressor rotation is clockwise when facing the
compressor drive shaft. Never operate the compres-
sor in reverse rotation because this can result in
damage.
•
The suction and discharge flanges are ANSI B16.1 Class
600 type for the HPS 273 compressor models.
• Suction strainers for the HPS 273 compressor models
are external to the compressor. The strainer specified
must meet the following requirements as a minimum:
–
Filter cloth: SS 304, 30 x 150 Mesh, plain Dutch
Weave with 0.009 in. WARP diameter and 0.007 in.
WEFT diameter
–
Filter cloth support: 6 mesh with 0.035 in. wire di-
ameter, 0.132 in. openings with 62.7% open area
Compressor lubrication system
The lubrication system on a HPS 273 screw compressor
unit performs several functions:
• Provides lubrication to bearings, seal, and rotors.
• Provides a cushion between the rotors to minimize
noise and vibrations
• Helps keep the compressor at the proper temperature
and prevents overheating
• Provides oil supply to hydraulically operate the slide
valve and slide stop for the HPS 273 to provide capacity
and volume control
• Provides oil pressure to the balance piston assemblies
to help increase bearing life
• Provides an oil seal between the rotors to prevent ro-
tor contact or gas bypassing
Volumizer variable volume ratio control
The Frick compressor includes a method of varying the
internal volume ratio to match the system pressure ratio.
Control of the internal volume ratio eliminates the power
penalty associated with over- or under-compression. Vol-
ume ratio control is achieved by the use of a slide stop, a
movable portion of the rotor housing assembly that moves
axially with the rotors to control discharge port location.
Stepless capacity control
Capacity control is achieved by use of a movable slide
valve. The slide valve moves axially under the rotors to
provide fully modulated capacity control from 100% to
approximately 20% minimum load capacity. Approximate
minimum load capacity varies slightly with compressor
model, pressure ratio, discharge pressure level, and rotor
speed.
The slide valve is positioned by hydraulic movement of its
control piston. When in the unloaded position, gas is by-
passed back to suction through a recirculation slot before
compression begins and any work is expended, providing
the most efficient
unloading method available for part-
load operation of a screw compressor.
Oil pump (optional)
A demand oil pump is required for low differential pressure
applications
Note:
CoolWare provides a warning when the oil differen-
tial pressure is too low.
Oil being supplied to the compressor from the oil separa-
tor is at system discharge pressure. In 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 pres-
sure than compressor discharge pressure. All oil entering
the compressor is moved by the compressor rotors, out
the compressor outlet, and back to the system oil separa-
tor.
Construction details
Housing
All HPS 273 screw compressors 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 stan-
dard
asymmetric profile. The six-lobed male rotor directly
connects to the driver. The eight-lobed female rotor is
driven by the male on a thin oil film.
Bearings
HPS compressors are designed for optimal bearing life.
The HPS 273 compressor models are designed with a
conventional single-radial bearing design (HPSS). A
double-radial bearing arrangement (HPSD) is available as
an option to handle higher discharge pressure applications.
When evaluating operating conditions of the compres-
sor in CoolWare for performance, give consideration to
changes in those conditions based on operating transients
and seasonal changes. CoolWare automatically configures
the bearing arrangement for optimal life based on these
conditions.