Khun Suradech,
I interpret that even through there is BDV in the fire circle, we still need to consider multiple PSV. Multiple PSV is typically associated failure of utilities such as cooling water, heating medium or instrument air, power or fire in the fire circle. As mentioned earlier, the multiple PSV for offshore facilities is typically associated with fire. CES stipulates that we use the sum of the calculated relief loads and not the sum of the wide-open capacities of PSV for sizing the sub-headers. I have previously advised that we should use the wide-open capacity of the largest PSV plus the calculated relief loads for the rest of the PSVs in the fire circle. Apparently, it is too conservative and should use the CES’s recommendation of using the sum of the calculated relief loads.
Although CES stipulates that for fire circle, we need to use the depressurizing rate (if a depressurizing system is provided) or fire relief rate (if no depressurizing system is provided). I would personally check the sub-headers in the fire circle for both depressurizing rate or fire relief rate (even if depressurizing system is provided). In other words, the sub-headers should be adequately sized for either depressurizing rate or fire relief rate.
Khun Suradech,
I interpret that even through there is BDV in the fire circle, we still need to consider multiple PSV. Multiple PSV is typically associated failure of utilities such as cooling water, heating medium or instrument air, power or fire in the fire circle. As mentioned earlier, the multiple PSV for offshore facilities is typically associated with fire. CES stipulates that we use the sum of the calculated relief loads and not the sum of the wide-open capacities of PSV for sizing the sub-headers. I have previously advised that we should use the wide-open capacity of the largest PSV plus the calculated relief loads for the rest of the PSVs in the fire circle. Apparently, it is too conservative and should use the CES’s recommendation of using the sum of the calculated relief loads.
Although CES stipulates that for fire circle, we need to use the depressurizing rate (if a depressurizing system is provided) or fire relief rate (if no depressurizing system is provided). I would personally check the sub-headers in the fire circle for both depressurizing rate or fire relief rate (even if depressurizing system is provided). In other words, the sub-headers should be adequately sized for either depressurizing rate or fire relief rate.
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