HPS Rotary Screw Compressor Units
070.700-IOM (MAR 21)
Page 10
Installation
The level-control method (see
) uses a
float level
control on the receiver to close a
solenoid valve feeding
the evaporator when the liquid falls below that amount
necessary for 5 min of
liquid injection oil cooling.
Figure 12: Level control
Table 5: Liquid injection system line sizes
Refrigerant HPS
model
Line
size
5 min supply,
lb (kg)
Liquid volume,
ft
3
(m
3
)
R-744
Cascade
36
0.75
51 (23.13)
0.85 (0.024)
42
57 (25.85)
0.95 (0.027)
60
88 (39.92)
1.46 (0.041)
Conditions:
Cascade: -60°F (-51.1°C) Evap, and 20°F
(-6.7°C) Cond, 10°F (-12.2°C) suction (line) superheat.
Water or glycol oil cooling
(optional)
The plate-and-shell and welded-plate type water or glycol
oil cooler is mounted on the unit complete with all oil pip-
ing. The customer must supply adequate water connec
-
tions. Determine the size of the oil cooler supplied with
the unit, as outlined on the Frick P&I diagram and general
arrangement drawings.
The water or glycol supply must be
sufficient to meet the required flow.
The glycol or water entering temperature must be no
lower than 60°F (15.6°C).
A
closed-loop system is best practice for the water or glycol
side of the oil cooler. Careful attention to water treatment
is essential to ensure adequate life of the cooler if
cooling
tower water is used.
It is imperative to regularly analyze the
condition of cooling water or
glycol closed-loop fluids as
necessary, and maintain at a pH of 7.4, but not less than 6.0
for regular
heat exchanger life
.
After initial start-up of the
compressor package, clean the
strainer at the inlet of the oil
cooler several times in the first 24 hours of operation.
In some applications, the plate and shell oil cooler may
be subjected to
severe water conditions including high
temperature and/or hard water conditions. This causes
accelerated
scaling rates, which degrades the perfor
-
mance of the heat exchanger. A chemical cleaning process
extends the life of the plate and shell heat exchanger. It is
important to establish regular cleaning schedules.
Cleaning:
A 3% solution of phosphoric or oxalic acid is ap-
propriate. Other cleaning solutions can be obtained from
your local distributor, but they must be suitable for stain-
less steel. The oil cooler may be cleaned in place by back
flushing with an appropriate solution for approximately 30
min. After back flushing, rinse the heat exchanger with
fresh water to remove any remaining cleaning solution.
Figure 10: TSOC piping arrangement
• The thermosyphon oil cooler is supplied with oil side-
piped to the compressor unit and stub ends supplied on
the refrigerant side.
•
A refrigerant-side safety valve is required in this loca
-
tion only when refrigerant isolation valves are installed
between the cooler and thermosyphon receiver. If no
valves are used between the cooler and TSOC receiver,
the safety valve on size the TSOC receiver to handle
the volume of both vessels. Then, you an eliminate the
safety valve on the cooler vent (liquid refrigerant side).
• The system receiver must be below the thermosyphon
receiver in this arrangement.
Liquid injection oil cooling
(optional)
The liquid injection system provided on the unit is self-
contained but requires the connection of the liquid line,
sized as shown in
It is
imperative that an uninterrupted supply of high pres‑
sure liquid refrigerant be provided to the injection system
at all times. Two items of
extreme impor tance
ar
e the
design of the receiver/liquid injection supply and the size
of the liquid line.
It is best practice that the
receiver be sufficient ly oversized
to retain a 5-min supply of refrig erant for oil cooling. The
evaporator supply must be secondary to this consider-
ation. There are two methods of accomplishing this.
) uses two dip
tubes in the receiver. The liquid injection tube is below the
evapor ator tube to ensure continued oil cooling when the
receiver level is low.
Figure 11: Dual dip tube
CALCULATED
HEIGHT
