We should all be aware that supposedly the pores of the steel can still hold propane after they have been rinsed several times or so I've been told. I couldn't find any local welding shops that would touch my already rinsed tanks.
Petroleum products, sure, but significant volumes of propane gas escaping from pores in steel?
Even so, propane is heavy and venting for a year doesn't necessarily mean all the propane is gone. It's just a matter of flowing air though the tank in a way that guarantees any combustibles are diluted to non-explosive levels, no water filling required if properly vented with sustained flows of fresh air that will displace any remaining propane.
Now that they have sat vented for another year, I think I may fill them with water and cut some holes with a holes saw (2 5/16 to slip a 2" pipe into). I always thought the fittings needed to be cut thru the very ends of the bells of the tank, but now I'm wondering if the holes could all be made on the top side of the tank (normal horizontal position) then welded is place after draining 6" or so of water.
[I assume you're talking about vertical tanks.] You can weld half-couplings to the ends of the bells and cut the holes afterwards with a good hole saw. I plumbed the completed manifolds to the couplings and tacked the couplings in place and then got the manifolds out to the way before the final welds, which I suspect saved some grief fitting the manifolds to the tanks after they were in place. I used diffusers to cut down on jetting from vertical ports, but I think it was a waste of time. The flow rates are pretty low, and even if there's a layer of mixed water who cares.
However although I built the shed to fit the tanks, space above an below the tanks was crowded enough without the plumbing. If I had to do it over again I'd figure out some way to come in from the side. Some guys have been using short angled risers and dip tube to reach the top and bottom of the tanks from the side.
Granted the water wouldn't enter or exit at the very top or very bottom but I don't think that would matter all that much. A benefit of this also would be less mixing since the water would enter from the side rather than the top.
The closer to the ends the better, but no sense chasing the last five gallons if it makes things easier to let it go.
One would still need a way to bleed the air out of the top of the bell (when mounted vertical as a storage tank) but I believe the thickness of the bell is enough that a 1/4 or 3/8" hole could be drilled and tapped without the need to weld a fitting. Anyone have any thoughts on this? If this is not viable I may have to see if an actual tank place would weld mine but since the tanks are scrap I'm betting they won't touch them for that reason.
Tank should be plenty thick enough for 1/8" pipe, just make sure you have the right size drill bit and then tap carefully. A little Permatex and you're good to go.
Had everything cleaned up and tacked in place and called a few places that wouldn't do the final welding. But this one guy that ran a bona fide boiler repair business told me to run shopvac air in the top, with exhaust from a diptube into the bottom of the tanks for a few hours before I brought them over and he went ahead and welded the couplings with the tanks on the trailer while I waited. Two passes of 6011.
I had on ear gards for noise on and cant here good anyways but even with that on I heard this, a 2 foot blue flame shot out top of tank for about 10 seconds I ran across yard and stood there shaking, I could not believe what just happen and how lucky I was it did not blow up. I dont understand how this hapened when I had it air out so long and looked inside seen nothing??
