Simple question about PSV location

[hswang2]

I would like to ask a very mundane question.
Why does the PSV locate on the cooling water return line instead of cooling water supply line?
I tried to deduct the reason. Cooling water return line is in low temp condition; therefore, valve closing may cause the saturated liquid in the return line flash.
Could any experience process engineer explain detail to me? Thank you very much.

 

[chemjock]

If the valve relieves, cooling water has to flow through the exchanger to discharge. This is almost always safer than no flow through the exchanger. But if the relieving case is when the cooling water is blocked in, it probably does not matter whether the PSV is on the supply or return.

 

[ajs1972]

Because if the supply and return lines are blocked, the hot side in the heat exchanger could warm the trapped water and increase the pressure, and the heat exchanger could breake. Other way to avoid this is, in addition to PSV, could be to place a lock in the valve of the cooling water return and avoid the close of valve.