Isolation valves upstream of safety valves

[bkay]

A reciprocating compressor has a safety valve at its discharge, set at 140 Kg/cm2. There is also an automatic vent control system and a 2 out of 3 high pressure shutdown of compressor. The safety valve is passing frequently and plant management want to install an isolation valve (full bore opening) upstream of the safety valve so that it can take it out for maintenance when the compressor is running.
Can anyone explain the codes that permit an isolation valve to be installed upstream of a safety valve? Is LOPA and SIL analysis mandatory for this case?

[Qalander]

I will consider this in a way Criminal unless alternate provision of equivalent capacity/rating is available and commissioned in place.
Best regards
Qalander

[mobek]

Although i've never seen such a thing, but you can do so provided you've the isolation valve on lo position during normal operation. However, you should consult the compressor manufacturer.