Swing compressor dual hp switches setup.

[jjgixer]

Good morning ladies and gentlemen.

I have a GEA LT screw in a swing configuration. In LT mode the discharge feeds a open type flash intercooler. MT modes feeds the cooling towers.
LT -38c /-10c
MT -10 / 32c

Valves are manually changed between LT and MT. LT hp setting is set for 13.4b and the MT hp set for 19.7b.

I have a fellow colleague saying that both hp switches should set for the lowest value. I have scoured the internet trying to find a “good working practice” for swing compressor operation. I cannot find any source(s) as to why this needs to be the case.

I thought I would open this up to like minded individuals who could light the way....

Many thanks

[Brian_UK]

What are the switches operating?

[jjgixer]

HP safety switch...

[seanf]

What are the PRVs pressures?

[RANGER1]

jjgixer,
Normally HP trip settings are 10-15% lower than lowest relief valve for that part of system
Interstage/High stage.

Other things to consider is relief between compressor discharge to suction, HP should be below this
Local compressor pressure transducers
Any other HP protection, like a hardwired pressure switch, most common is Danfoss KP7ABS dual protection switch.

So in order compressor unloads on high pressure or high motor amps/ local transducer trip/hard wired pressure switch trip, which stops starter/internal relief valve opens/relief to atmosphere, last line of safety protection.

I think in UK would be similar

In your case I would try to set at lower setting, as what scenario would you want compressor to be running up to 19.7 bar when design of 32 SCT 1.136 bar.

You need to check all relief settings on plant to make informative decision.

Most compressor manufacturers have high relief settings on packages so to meet most design scenario's, does not mean you have to set it that high.