Buried LP tank - InspectionNews

Rick Hurst · #1 (**permalink**) 06-02-2007, 07:57 PM

Ran across my first buried LP tank today.

Wouldn't you think it could be a potential hazard with the tank in close proximty of the driveway. I'm think someone comes home at night tipsy, runs off the drive and this the top of this buried tank. KABOOM

Would some bollards be appropriate?

Also the copper line where it entered into the structure was exposed and not protected against possible damages.

Bruce Breedlove · #2 (**permalink**) 06-02-2007, 08:52 PM

Rick,

It looks dangerous to me. I can think of a few more scenarios:

Spark from lawn mower ignites fumes

Heat from catalytic converter (vehicle parked over tank) ignites fumes

Bollards around the tank would be a good start.

Tim Moreira · #3 (**permalink**) 06-02-2007, 11:56 PM

I've never heard of an Lp tank being burried..but than again...what do I know? Is that legal?

Bob Harper · #4 (**permalink**) 06-03-2007, 06:57 AM

Wow, you guys need to get out more often! (teasing)

If you look at the tank clearance diagrams in the appendix of NFPA 58, you'll see three diagrams: DOT cylinders, ASME above ground tanks and ASME buried tanks. There is a 10 foot clearance from this tank bonnet to the building or property lines where buildings could be built up to 2000 gallons. There is a chart for clearance per tank size.

3.2.9.1
a) containers installed in areas with no vehicle trafiic shall be installed at least 6" below grade
b)In areas where vehicle traffis is expected, a noninterchangeable underground container shall be installed at least 18" below grade or the container shall be protected from damage from vehicles. Protection shall be provided for the fitting housing (bonnet), housing cover, tank connections, and piping against vehicle damage.
It also addresses construction or excavation near the tank.

Seriously, buried tanks are all the rage around Philly. I guess it is a regional thing. BTW, size being the same, a buried tank performs better than an above ground cylinder as far as vaporization rate goes.

The copper high pressure line coming up out of the ground should be coated, sleeved or protected. It should run into an approved gas cock then a second stage regulator then enter the building again with a sleeve. Rarely done.

HTH

Jerry Peck · #5 (**permalink**) 06-03-2007, 03:43 PM

I've seen buried gas tanks all over for decades. Almost put one in at our old house, except that would have put it over 100 feet from the road and the gas companies hoses are only 100 feet long.

Nick Ostrowski · #6 (**permalink**) 06-03-2007, 05:31 PM

Like Bob said, buried tanks are the norm around here in newer developments. It's cheaper to install underground tanks than to run new gas lines to areas that have none present.

Jerry Peck · #7 (**permalink**) 06-03-2007, 06:31 PM

A reminder - if you are in a flood zone, that underground tank will float when flooded over if it is not counter balanced down.

Most requirements are either anchors or concrete pads with enough uplift resistance / weight to keep an empty tank down.

Let's say you have a 250 gallon tank, that means it would hold 250 gallons of water, which means it displaces 250 gallons of water, which means it displaces 1870 pounds of water (I believe water weight 7.48 pounds per gallon), and if the tank weighs in at 470 pounds empty (just a guess), then the tank needs to be anchored down to concrete which weighs at least 1400 pounds. That would be two footings (running under the tank perpendicular to the tank, not parallel alongside it) approximately 1 foot by 2 feet by 10 feet long.

If the footings ran alongside the tank, each would need to be approximately 2 feet by 2 feet by 10 feet long as each would need to restrain the entire displaced water weight.

Or just a 4 foot by 6 inch by 10 foot slab below the tank with the tank anchored to it.

Bob Harper · #8 (**permalink**) 06-04-2007, 06:55 AM

NFPA 58 addresses the flood issue as Jerry pointed out.

JP, according to the NAtional Propane Gas Assn, I have water at 8.34 lbs/ gallon and propane (1.50 vapor density) at 4.2 lbs./ gallon.

Of course, in flood areas, they need to secure the coffins in the cemetary, too. Seriously, if you are inspecting a house along a river and the house has a high water mark from frequent floods, I would be looking not only for tank restraints but to see if the regulators are above this floor line. If they appear to have gone swimming, they should have been replaced as with any gas control that has been submerged.

Jerry Peck · #9 (**permalink**) 06-04-2007, 01:00 PM

Quote:

Originally Posted by Bob Harper

JP, according to the NAtional Propane Gas Assn, I have water at 8.34 lbs/ gallon and propane (1.50 vapor density) at 4.2 lbs./ gallon.

Yeah, after I posted that I started wondering if I was thinking of gallons per cubic foot instead pounds per gallon, but my mind just could not remember which was which. Thanks.

8.34 pounds per gallon

7.48 gallons per cubic foot

Someone needs to check that last one too, losing memory here.