Hello,
We are having two parallel filters (F1 is online and F2 is stand-by) located downstream of Mercury removal beds. These filters are equipped with inlet motor operated isolation valves and each filter is equipped with one PSV sized for fire case as it is the credible scenario (see sketch).
PSV2 is due for testing date however we are not able to do so because M3 is passing. Hence in the current situation, PSV 2 might not pop up in case of fire in F2. M3 requires total train shutdown so that it can be fixed as per which the management would not like to do a shutdown.
As a mitigation for that, I would like to put both F1 and F2 online (M1 and M3 to be fully open), so that in case of fire case in F2, the overpressure can be released by PSV1 located in F1. since PSV2 is no more reliable and PSV1 was recently tested.
Note that the calculated orifice size required for the calculated relief load for both PSV 1 and PSV 2 is 0.2 cm2 each and the installed orifice size for PSV1 and PSV2 is 0.7 cm2 each. Hence I assume that even in the case of external fire for both F1 and F2, PSV1 is sufficient to release the required relief load of both filters.
Kindly let me know if the above mitigation is correct.
Regards,