How to size a slop oil tank vent?

[kallne2]

I have never sized vents before, and am asked to confirm slop oil tanks (quantity -2) vent sizings for inter-tank transfer as well as in-flow from upstream sources. The tanks are 45' ID by 35' high. DP is 2.5" water int. & 1.24" water ext. at -50 F. The current vent sizes are 12 x 14" at +/- 0.5 oz. There are 2 vents per tank.

I've looked at the API std. 2000; but I'm confused as to how it'll tell me about vent sizes. Based on the data sheet, the oil movement in/out is 240,000/120,000 gph respectively. I've calculated the breathing required for oil movement to be 16000 scfh air in and 68571 scfh air out. The thermal breathing required was found from the tables to be both 10,000 scfh air in/out. How exactly do I go about ensuring that 12 x 14" is adequate size for a vent? I've tried to speak to the vendor to no avail. What exactly should I go about doing?

 

[MJCronin]

Call one of the vendors of tank vents and beg for help..

The folks at Protectoseal and Varec are very helpful..

-MJC

 

[kallne2]

Do you know of any good contacts, because I called Varec with no response.

 

[IFRs]

Get from them a vent catalog. Their catalog should have flow rates for their vents as a function of pressure.

 

[shahyar]

What I do is using the curve at the end of API 2000. It is a typical test curve but I used it to check vendor sizes, and it is always matched with what they said.

Hope this help