Dear All

I think there is a confusion created while using the equation for flow rate calculations for External fire case (API 521 section 3.15.2.1 equation 8).

If we use the equation directly without checking the minimum recommended value of Environmental Factor, we end up in wrong results. Fortunately my calculations were checked & error discovered !!!

care to expand on what the "error" or confusion is?

I agree with "Kdal"; ;what's the error?

There is no "recommended" environmental factor, just what is allowed. The environmental factor can be used to reduce the required relieving capacity of a system (reduce the relieving rate because I have approved insulation or good drainage or good fire fighting ability/sprinkers). You have the choice to use them or not. The codes do restrict their use so you can't just apply all you want haphazardly. If you chose to use too many of them, then yes, this would be an error. If you just didn't use what you are allowed to use, well, then you get a larger relief than you might otherwise. Is this an error? I wouldn't classify it as such.

Sorry my mistake. Its not the Environment Factor F but F' that I was referring to.

Equation no 8 is derived from equation 2 (API 520) & Equation 5 & 6 (API 521). In one of the cases that I was calculating, the value of F' was much below 0.01. In that case if we use equation 8 directly, the value of W comes out to be very low. So what we did was taking the value of F' as 0.01 & once again rearranging Equation 2 (API 520) calculated the value of W. Thats why I think equation 8 has to be used with care.

Thanks

Kiran G Parihar