Engineering manual - SAB 193-233-283 S A-frame (including ATEX)
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008831 en 2022.02
To control the rate of the V
i
change, throttle the needle valve at the SC3 port.
4.17
Compressor oil cooling systems
The unit can be equipped with one of several systems for controlling the compressor oil tem-
perature. They are single or dual-port liquid injection and refrigerant-cooled (thermosyphon) or
water-cooled oil coolers. Each system is automatically controlled, independent of compressor
loading or unloading.
Oil cooling systems should maintain oil temperature within the following ranges for R717 and
HCFC/HFC:
Liquid injection
oil cooling
External*
oil cooling
55-77°C
[130-170°F]
49-71°C
[120-160°F]
* : Refrigerant cooled (Thermosyphon) oil cooling (TSOC) or water-cooled oil cooling (WCOC.)
Table 5: Oil cooling
Single-port liquid injection.
The single-port liquid injection system is designed to permit liquid
refrigerant injection into one port on the compressor at any given moment and operates as
outlined.
Solenoid valve, YY5, is energised by the microprocessor when the temperature sensor, in-
stalled in the compressor discharge, exceeds the LIOC (Liquid Injection Oil Cooling) set point.
High-pressure liquid refrigerant is then supplied to the temperature control valve (TCV). See
Fig. 27 and Fig. 28.
Dual-port liquid injection
The dual-port liquid injection system is designed to obtain the most efficient compressor per-
formance at high and low compression ratios by permitting injection of liquid refrigerant into
one of two ports optimally located on the compressor. This minimises the performance penalty
incurred with liquid injection oil cooling.
The dual-port system contains all the components of the single-port system with the addition of
a double-acting solenoid valve, YY9, and it operates as outlined.
The solenoid valve, YY5, is energised by the microprocessor when the temperature sensor, in-
stalled in the oil manifold, exceeds the LIOC set point. Liquid refrigerant is then passed through
the temperature control valve (TCV) to the double-acting solenoid valve, YY9. Depending on
the compressor’s operating volume ratio (V
i
), the microprocessor will select the flow of the
liquid refrigerant to either compressor port SL-1 or SL-2, whichever is more efficient.
When the compressor operates
below
3.5 V
i
, the compressor port, SL-1, supplies the liquid
cooling. When the (V
i
) rises
above
3.5 V
i
, port SL-2 supplies the liquid cooling.
Liquid injection adjustment.
For discharge temperature set point and PID regulator parame-
ters, refer to the operating manual for the control system. The discharge temperature set point
is set to the required oil temperature, see
in subsection 4.17