Welding on RV frame close to propane bottle

Most of us have welded on automobile frames at one time or and other and while I'm immediately leary the closer I get to the fuel tank while
striking an arc, prevalent thinking is that it is not "unsafe" to do so. Walk into any muffler shop and watch a while. They arc away all day long on underbodies and I wonder if the weldor performs even a cursory check for any type of fuel leak before he starts MIG-ing away.
I've got a job to do for a buddy on a small RV camper putting him on a welded rear bumper suitable to a fix a towing hitch reciever to. Looking the job over I notice he's got a propane bottle in an enclosed aft compartment about 18 to 24 inches from where I may have to stike an arc. The bottle is currently fully charged.
Just wondering what the "rule" is for welding near propane bottles vs regular automobile fuel tanks. Obviously I would be concerned about leaks and will make sure no gas is venting before I start but also I'm wondering about any risks associated with passing current through the frame to which the bottle is in direct physical contact with.
Is there anything in the nature of propane that makes for greater risk of explosion compared to regular fuel tank as regards my secondary concern outlined above?
Dennis van Dam
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Most states do not allow the transport of a Propane in an enclosed space. The thinking is that any leaks will produce an air/fuel mix in a confined area, good way to have an explosion. With you supplying a nice ignition source, I'd pull the tank out before doing any welding.
Dennis van Dam wrote:

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Roy,
Yeah, I thought about that. When I went to look at the job the tank was located in an aft compartment down low that has an access hatch opening to the outside. At a glance the opening is too small to pass the bottle so I'm not sure how it was installed into the enclosure.
When the vehicle shows up for the work I need to look at that again and see it there is a way to get the bottle out. If not, surely the enclosure is vented to atmosphere for the very reason you mention. (Is propane heavier or lighter than air? I'm guessing lighter but I'm not sure.)
Even if I reasonably establish there are no leaks/fumes I will purge the enclosure with a fan and put up shielding between the arc and the enclosure.
But I'm still wondering about any risk associated with passing current through metal to which that bottle is directly attached.
Thanks for the reply.
Dennis

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In article
snipped-for-privacy@mindspring.com (Dennis van Dam) wrote:
(Is

And I see after a quick Google that it is *heavier* than air. Good to know.
Dennis
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As long as you are working in an open area and not an enclosed space, there are no vapors emitted from a propane tank like there is from a gasoline tank. Propane WILL vent if the tank gets hot and the liquid propane expands and vents thru the pressure relief valve (I have seen this where the RV burned and smelled old tanks venting when overfilled and sitting in the sun but not on newer tanks that can't be overfilled. I consider it safer to work around propane tank than gasoline tank. Just close the tank valve and be sure it doesn't get hot enough to need to release pressure. Even if it does, it will not continue to burn like gasoline will.
Dennis van Dam wrote:

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Yep -
Don't park a propane tank over a pit to work on. IF there is a leak - the propane drops down into the pit. It is heavier than air.
I'd have a fan or plenty of ventilation (somewhat standard welding anyway getting the fumes from you and gas from you as well).
If stick or mig or tig - keep the return between you and the tank and the work between you and the return clamp. Don't want current through the tank.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member http://lufkinced.com /
Dennis van Dam wrote:

-
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Slightly OT.... I work in an auto salvage yard, and we recently started to buy scrap steel also, stuff like washers, dryers, ect. Anyway, the only way we take tanks of any type is if they have a hole or are cut in half. Several weeks ago, we got in some small propane tanks from a grill, and they had about a 6x6 inch hole cut WITH A TORCH in the side of each one... you could see the burn marks on the paint and everything! You could also still smell the propane smell from the tanks, I don't know if the odor was imbedded in the steel or what but it was strong. I can't imagine what kind of idiot would torch on a tank, or how he did it without blowing himself into next week! I wouldn't have believed it if I hadn't seen it with my own eyes..... < shakes head > Earl
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big e lewis wrote:

Remove the valves, fill them with water, cut them with plasma. The "propane" smell is an odorant that really sticks around even if there is no trace of propane left BTW.
Pete C.
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I recently saw a guy at a scrap yard recycling hundreds of the old 20lb bottles. He was using a spear point on a log splitter mounted on the back of a diesel tractor. I moved further away when I realized that many of the bottles were not empty. There was occasionally a real big cloud when the bottle was pierced. Apparently no effective ignition source was within range but it sure looked scary. It amazes me what people sometimes do without causing a disaster!
Don Young
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Don Young wrote:

That propane tank in the car shredder on Monster Garage comes to mind...
Pete C.
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Maybe they were full of water when cut. We can only hope.
A guy - native worker - used a cutting torch on a Jet fuel drum overseas. He tried to cut the end out - for a trash can. He didn't last but for a minute.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member http://lufkinced.com /
big e lewis wrote:

-
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As others have pointed out, propane is less hazardous than gasoline. I can see very little risk that the current through the vehicle frame could produce any ignition hazard.
It is important, however, that you welding ground return fairly close to the weld, and particularly, don't cause the current to flow through any ball bearings, or such.
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Understood. Thanks Leo and thank you to all who replied. The consenus appears to be employ all the usual precautions.
The RV is now sitting in my driveway. The bottle is permanently built into the enclosure so there's no removing it however, commensurate with the heavier-than-air quality of propane, there is a large hole set in the floor of the enclosure to keep from accumulating fumes.
Also as Robert indicated the tank is the newer type that can only be filled to 80% capacity and it's parked in the shade so spontaneous venting should not be a problem (but I *will* keep the enclosure ventilated with a fan) and, as a few of you have mentioned, always be aware of where my ground clamp is set with respect to where the tank is and where I'm striking an arc.
Thanks again for all the replys, I appreciate the help.
Dennis van Dam
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replying to Leo Lichtman, Hannah wrote: Thank you for sharing Leo. I was wondering this for welding on a bus with a 100lb tank bolted to the frame.
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Nice website Mr. Eastburn. Have you looked into industrial/commercial work as well?
JTMcC.

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replying to Leo Lichtman, Hannah wrote: Thank you for sharing Leo. I was wondering this for welding on a bus with a 100lb tank bolted to the frame.
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