Several manifolded inlet lines to one common thermal PSV

[SNORGY]

Several spiral heat exchangers in parallel, each liquid-liquid cross exchange (warm water / oil emulsion; warm oil / oil emulsion; steam / oil emulsion).

Can thermal relief be provided by one single device manifolded to all liquid inlets / outlets (one per side, total two)? Code (ASME Section VIII Div. 1) does not appear to disallow it, but without CSO valves on each line to the PSV, isolation of individual exchangers for cleaning or maintenance becomes problematic, if at all possible. Also, it sets up the inescapable scenario of cross-contamination of fluid streams on at least one side (non-emulsion side) of the exchanger.

I am being asked to do this (due to piping space constraints and "not enough room for separate PSVs"), and although "Code allows it", so far, I am refusing to do it because I think it's dumb. I am thinking that if there is room for separate CSO valves, there is room for separate thermal PSVs, so suck it up and fit them in.

Am I being inflexible and uncooperative? Bearing in mind that it is my professional endorsement that is being called for on the drawings.

Regards,

SNORGY.

 

[Duwe6]

Both scenarios are "legal" but I'd build it like you want to. For thermal relief, a very small PRV is plenty. There has to be a spot that a 1/2" o'let can be added, and the 1/2" pipe snaked out to a convenient location for a PRV.

Bottom line SNORGY, you're right.

 

[SNORGY]

Thanks Duwe6.

The issue sort of died when the cross-contamination potential was pointed out.

Regards,

SNORGY.