Engineering manual - SAB 193-233-283 S A-frame (including ATEX)
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008831 en 2020.10
Technical description
Fig. 29: Suction check valve by-pass
Check valve CV-4 is installed on all units with suction pressure below atmospheric or installed with
economiser option utilised on multiple compressor plants.
On high-stage systems, the check valve, CV-4, should be installed with a 3.1 bar [45 psi] spring
to avoid the possibility of back-feeding to a shutdown compressor from a common economiser
vessel.
On booster systems, the check valve, CV-4, should be installed with a 1.7 bar [25 psi] spring to
avoid the possibility of air ingress into the system if the system suction pressure is below
atmospheric.
NV-2 must be closed if the oil pump should run for long periods of time when the compressor is
stopped. This is important in order to avoid oil being pumped up the suction line.
F
rom
separator
cold-start
valve
For 8” and larger suction valve
customer supplied line
Compressor end view
Suc
tion gas
to the compr.
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