Johnson Controls SABROE Unisab III Control, Engineering Manual, Page: 50 / 348

Engineering manual - UniSAB III 1.10.8
50/346
001930 en 2021.06
Alarms and shutdowns
grad.
Note 39 For SAB 193 H, 233 H, 283 H, 355 H and SAB 273 S screw compressors, the internal
pressure inside the compressor block is calculated as follows:
Internal pressure = P
suct,abs
* Vi K
Where the Vi K parameter is a function of the actual volume ratio of the compressor,
depending on whether the economizer is activated or not.
When the internal pressure is higher than the high alarm limit, capacity will be limited
and a
High internal pressure alarm is issued.
When the internal pressure is higher than the high shutdown limit, at a capacity
above 70%, a
High internal pressure shutdown alarm is issued.