Should I vent diesel storage

TractorGuy · Jan 4, 2017

I bought a couple of 55 gal oil drums to store diesel fuel in. They have the typical 2 inch bung and 3/4 inch vent holes with caps. I'm thinking it might be a good idea to keep them vented to prevent expansion and contraction. Ordered a couple of compressor filter silencers with 3/4 male fittings. The drums will be stored outside under a shed. They will get damp from dew and blowing rain. Should I leave them vented or just put the vent in when they are in use?

What are your opinions or knowledge on this? Will keeping it vented promote or reduce condensation in the drums?

The plan on these is to purchase 100 gallons of off road diesel to have on hand and use. I purchased a military surplus diesel generator that is equipped with an auxiliary fuel supply system. It has a bung adapter and pickup tube that fits the large hole in the drums. A secondary fuel pump and float switch senses when the tank drops below a certain level and pumps fuel from the drum to the generator tank. I figure I will use fuel from the drums in my tractor and backhoe to keep it rotated and fresh.

LD1 · Jan 4, 2017

I dont know, it will be interesting to see what others have to say about this.

On one hand, I see what storing fuel in buckets does as the temp changes. I swear sometimes it looks like a bucket is gonna pop.

But on the other hand, liquid is stored and sealed tight in barrels all the time with no issues. And there is no chance of getting moisture in there from temp and humidity changes.

CurlyDave · Jan 4, 2017

If the drums are vented, water will condense in the fuel for several reasons.

1) The ullage (volume of drum above fuel, where there is air) will breath due to expansion and contraction of the air inside with temperature change, this brings in fresh water vapor, which condenses when temperatures fall, and

2) as temperature of the fuel increases its vapor pressure increases, as temperature falls, the vapor recondenses, and

3) the fuel itself has dissolved air in it, as temperature increases some of the air comes out, as temperature falls some air goes back into solution, and

4) the fuel itself will expand and contract with temperature change.

The only way to prevent this is to seal the drums. The pressure in the drum will increase as temperature increases, for all of the reasons above. The best way to prevent overpressure is to not fill the drum completely before sealing it.

I would seal the drums, being sure to leave enough room for some expansion.

Egon · Jan 4, 2017

That's as good an explanation as you can get.

TnAndy · Jan 4, 2017

Never had any trouble with stored gas or diesel as long as you put 55 gallons in a 55 gallon drum (it leaves about an inch or so of head space at the top of the liquid). I don't vent, in fact, I seal mine with paint after the bung is screwed in tight. Gasoline keeps fine for about 4-5 years using PRI-G, and diesel I suspect about forever with PRI-D.

But if you seal a 55 gal barrel of gas good and tight that is about half full, and the weather turns off cold, THIS is what happens

Which I suppose was better than the reverse, sealing it in cold weather, and when the temp increased, something blew. The fitting on the 3/4" is to connect an air hose...I blew the drum back out, then used it for scrap oil.

Texasmark · Jan 4, 2017

I don't. I have 3 of those in a dedicated trailer which sits under a covering similar to a car port. They stay tightly sealed till I install my electric pump on a tank and it is partially sealed....partially because when I start pumping the ends would suck in otherwise. It stays till the tank is empty at which I move to another pump and seal off the empty. I leave an air gap at the top of about 5 gallons for expansion. Been that way for 20 years and have zero problems with fuel loss, algae and water accumulation. I use Power Services storage additive also which keeps my injectors clean as an added bonus.

richriddle · Feb 13, 2017

CurlyDave, thank you for the explanation. You answered several pertinent questions to our newly acquired hobby farm. Our local off-road diesel supplier recommended placing a filter in the system to help eliminate water.

Texasmark · Feb 17, 2017

richriddle said:
CurlyDave, thank you for the explanation. You answered several pertinent questions to our newly acquired hobby farm. Our local off-road diesel supplier recommended placing a filter in the system to help eliminate water.

I didn't mention it but I have one at the outlet of the pump too. The Goldenrod that TSC sells make a water absorption cartridge for their after market filter cannister. That's the one I use.

CADplans · Feb 17, 2017

My two fuel tanks (100 gal, 50 gal) are not vented,,,, kinda,,,

They came with a fill cap that works like a radiator cap,,, pressurized in, or out at about 5-10 psi.

I would bet they sell these at TSC,,, it fits their tanks. They are pipe thread,, might fit a barrel?

I have had the 100 over a decade,,, no moisture gets in! :thumbsup:

RandyT · Feb 17, 2017

CADplans said:
My two fuel tanks (100 gal, 50 gal) are not vented,,,, kinda,,,

They came with a fill cap that works like a radiator cap,,, pressurized in, or out at about 5-10 psi.

I would bet they sell these at TSC,,, it fits their tanks. They are pipe thread,, might fit a barrel?

I have had the 100 over a decade,,, no moisture gets in! :thumbsup:

that is the type of cap I have on my 300 gallon overhead gravity flow tank. the cap assembly was purchased at TSC.