070.250-IOM1 (NOV 2013)
Page 6
TDS_ Rotary Screw Compressor
Installation - Operation - Maintenance
4. Provides an oil supply to hydraulically actuate the slide
valve and slide stop.
5. Provides oil pressure to the balance piston to help increase
bearing life.
6. Provides an oil seal between the rotors to prevent rotor
contact or gas bypassing.
Oil pump
A demand oil pump is required for low differential pres-
sure 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 pressure lower 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 TDS_ screw compressor castings are close
grain, pressure tight, grey cast iron to ensure structural
integrity and mechanical and thermal stability under all
operating conditions. Ductile iron and steel housings are
also available for special applications. Contact Johnson
Controls – Frick Sales for additional information.
Rotors: The rotors are made from the highest quality
rolled steel to exacting tolerances of the latest industry
standardasymmetricprole.Thefour-lobedmale rotor
is directly connected to the driver. The six-lobed female
rotorisdrivenbythemaleonathinoillm.
Bearings: Antifriction bearings with L
10
rated life in
excessof50,000hours(usingtheFrickSuperlter
™
) at
design conditions are used for reduced frictional horse-
power and superior rotor positioning, resulting in reduced
power consumption, particularly at higher pressure ratios.
Cylindrical roller bearings are provided to handle the
radial loads and the thrust loads are absorbed by two-
point or four-point angular contact bearings. In addition,
a thrust balance piston is provided to reduce the thrust
load and improve bearing life.
Shaft seal: The compressor shaft seal is a single-face
type with a spring-loaded carbon stationary surface riding
against a cast iron rotating seat. The seal is capable of
withstanding static pressure up to 400 psig. During opera-
tion it is vented to low pressure to provide extended life.
Volumizer variable volume ratio control: The Frick com-
pressor 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 associ-
ated with over- or under-compression. Volume ratio control
is achieved by the use of a slide stop which is a movable
portion of the rotor housing that moves axially with the
rotors to control discharge port location. The slide stop is
moved by hydraulic actuation of a control piston. The range
of adjustment is listed in Table 3.
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 con-
trol from 100% to minimum load capacity. Minimum load
capacity varies slightly with compressor model, pressure
ratio, discharge pressure level, and rotor speed. See the
Table 1 for minimum capacity for all TDS_ models.
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
themostefcientunloading method available for part-
load operation of a screw compressor.
Table 3: Compressor volume and capacity ratio
Model Min
Vi*
Max
vi*
Min.
Capa-
city
%
Slide
valve
travel
(in.)
Slide
stop
travel
(in.)
TDSH 163S
2.2 5.0
Refer to Coolware
™
5.494 2.140
TDSH 163L
2.2 5.0 6.918 2.694
TDSH 193S
2.2 5.0 6.497 2.530
TDSL 193L
2.2 5.0 8.662 3.374
TDSH 233S
2.2 5.0 7.843 3.055
TDSH 233L
2.2 5.0 9.877 3.847
TDSH 233XL
2.2 5.0 9.889 4.752
TDSH 283S
2.2 5.0 9.526 3.710
TDSH 283L
2.2 5.0 11.996 4.672
TDSH 283SX
2.2 4.2 11.951 4.680
TDSH/B 355S
2.2 5.0 10.360 5.690
TDSH/B 355L
2.2 5.0 14.127 5.031
TDSH/B 355XL
2.2 5.0 15.443 6.373
TDSB 355U
2.4 4.5 15.482 6.399
* Optional 1.7 min. to 3.0 max.
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