Johnson Controls SABROE UniSAB III Engineering Manual page 49

Alarms and shutdowns
Note 35 For HPC compressors released for 50 bar design pressure (Mk 4 LL or newer), the
max. settings for discharge pressure high alarm and high shutdown are raised to
44.0/45.0 bar.
For HPC compressors released for 40 bar design pressure (Mk 4 or older), the
max. settings for discharge pressure high alarm and high shutdown are 40.0/40.0
bar.
For HPC/HPO compressors, the present max. setting for high alarm limit is 44.0
bar and the present max. setting for high shutdown limit is 45.0 bar.
When using R600 as refrigerant, these limits are lowered to: high alarm limit 35.5
bar and high shutdown limit 36.0 bar.
Note 36 For SAB 193 H, 233 H, 283 H, 355 H and SAB 273 S, the Oil balance reduction
pressure is calculated as follows:
Oil balance reduction pressure = Discharge pressure (abs) - Oil pressure 2 (abs).
The oil pressure 2 is measured at the compressor balance piston port (SB-2).
The Oil balance reduction pressure function is optional and must be enabled in
Configuration - Parameter Balance pressure reduction (Yes/No).
Note 37 For SAB 193 H, 233 H, 283 H, 355 H and SAB273 S, the Discharge temperature
difference is calculated as follows:
Discharge temperature difference = Discharge temperature - Oil temperature.
Alarm monitoring is only active when the compressor is operating at full capacity,
defined as capacity >/= 98%.
The alarm default limit and min. and max. limits depend on whether the Oil flow
control function is enabled.
At compressor start, alarm monitoring is delayed as set in the Discharge diff. start
timer. When the Discharge diff. start timer has run out, the alarm is further delayed
during operation as set in the Discharge diff. delay timer.
The Discharge temperature difference function is optional and must be enabled in
Configuration - Parameter Oil flow control (Yes/No).
Note 38 The Suction Pressure gradient is calculated as follows:
Suction pressure gradient = dP
The Suction pressure gradient function is optional for all compressor types and must
be enabled in Configuration - Parameter Suct. press. grad (Yes/No).
Note: For screw types SAB 193 H, 233 H, 283 H, 355 H, SAB 157 HR and SAB 273
S and for reciprocating types HPC, HPO, HPX using refrigerant R717, the Suct.
press. grad parameter is enabled as default.
For more information on how to set appropriate alarm and shutdown limits for the
Suction pressure gradient function; see 6.4.3 Compressor block, 22: Suction press.
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