Oil tank vent

Ron Schroeder

NFPA31-2006 is now out and the vent size was changed back to 1-1/4" in NFPA31-2001. I would also always make sure the vent is as large or larger than the fill

An ineresting read, wait a few seconds after the link page is loaded in your browser, and you should be taken to the correct spot on the page.

http://www.steeltank.com/library/tanktalk/vol151.aspx#fire

Jason_15

Oil tank vent

I know that it is O.K. to have a 2" fill and a 1&1/4 vent pipe. Following that logic, the vent is 3/4 smaller than the fill. At my house the fill is 1&1/2 and the vent alarm is 1" but after the alarm the installer reduced it down to 3/4 for the run to outside. So, my vent is also 3/4 smaller than the fill. The distance from the tank to outside is only about 3 feet. We don't have any local codes in my area ( farm country Wisconsin ) This wouldn't meet codes back east by most of you I am sure, but I am just wondering if I should be worried about tank pressure while filling? I watched the fill, and the whistle stops very quickly after the fill. Are there many 3/4 vents out in the field?? Is this situation an unreasonable risk?? Thanks, guys!! Regads, Jason.

Brad White_70

I believe that NFPA-30

as a reference standard if not a code, stipulates a 1-1/4" vent for oil tanks as a minimum size up to 660 gallons, IIRC.

It is not the difference in diameter to the fill but the area of the pipes for venting purposes.

Key to the vent size is to relieve pressure when filling and draining. The tank is not a pressure vessel or more to the point is a limited pressure vessel, generally not over 5 psi. If your vent were clogged (mouse, spider or wasp nest) you could be at risk. (Hypothetical, I know). But the point is a small vent is more likely to clog.

Does what you have work? Apparently. Is is to an acceptable standard? Not in my opinion.

My $0.02,

Brad

p.s. No codes in local Wisconsin farm country? Such lawlessness

chapchap70_2

Very few 3/4\" vents where I am

The 3/4" reduction logic doesn't hold because the oil hose nozzle opening is either 1 1/4 or 1 1/2". Since on an oil delivery, you are venting air and not oil, you have witnessed no problems. The older the tank gets and the possibility of the tank being overfilled....well??? thats where the problems may come in, especially if the vent cap reduces the venting capacity further.

I wouldn't leave it like that.

Brad White_70

I agree with equal size

vents to fill. Much more peace of mind.

What had the vent size been before being restored to 1-1/4", Bruce? I cited NFPA-30 (Flammable and Combustible Liquids Code) because of my work supporting emergency generators), although 31 is more specific to home heating. I thought as far as vents they were congruent; I will have to check.

Thanks

Brad

Ron Schroeder

Brad

Thet had gone to 2" vents with 1 1/4" fill, had to do with some crossover mishaps but after the studies were done they reverted back.

Brad White_70

Thanks, Bruce

I knew you would know.

Weezbo

vent the tank well

it the tank is not a pressure vessel.

tanks should arrive on the job site with a vaccum.