3 replies to this topic

[harini]

Dear All,

This is my first post in the forum. I have been a regular visitor to this Forum to read about the several discussions on the PSV's.
I would like to have some thoughts and suggections regarding the protective measures suggested by API 521, in case of the relieving temperature is higher than the recommended maximum wall temperature of the vessel material.
API 521 Ed 2007 - 5.15.4.2 Pg No 46 suggests that " Under Ideal Condition, water films covering the metal surface can absorb most incident radiation from pool-fire - flame impingement. The realiability of water application depends on many factors. Freezing weather, high winds, clogged systems, unreliable water supply and vessel surface conditions can prevent uniform water coverage. Because of these uncertainities, no reduction in environment factor is recommended; however as sated previously properly applied water can be very effective".

My question is,
1. Do we take reduction in the heat load in case of properly designed deluge system as per NFPA 15 or API 2030?
2. If the credit can be applied, what should be the value for F factor, as API 521 gives formulae only for calculation in case of insulations.

Would really appreciate your valuable comments.

Thanks and Regards
Harini

[skearse]

Because of these uncertainities, no reduction in environment factor is recommended

I would say that no, even with a "properly" deisgned deluge system, you should not take any credit for it. That also goes for determining whether to use the 21,000 or 34,500 heat input coefficient as well-I don't count a deluge or sprinkler system as adequate fire-fighting when choosing the fire heat-flux coefficient.

[JoeWong]

...Do we take reduction in the heat load in case of properly designed deluge system as per NFPA 15 or API 2030?...

I would say NO as the reliability, availability, effectiveness, efficiency, compatibility, maintenance and testing interval and etc of the "properly designed deluge system" may not reach the "acceptable level" (i think they are yet to be determined and derived by authoritative party).

[harini]

Dear All,

Thank you very much for the responses. In my calculation i have not given credit for the deluge system and have considered the F factor calculation as per API 521 - for insulation alone. But when this was discussed some of the engineers said we have deluge system and we can take credit for that and avoid fire insulation.
But finally i have submitted the calculations without talking credit for deluge system.

Thanks
Harini