Step 3: Chop the top off

Originally I was going to remove the valve before I started this part but I had trouble getting a spanner around it as there is a safety valve on one side and the gauge on the other, I pulled the gauge off with pliers but it had a long brass section sticking out which got in the way. on the other 2 sides was the handle.

If you can get a spanner around your valve I would recommend heating the bottle where the valve connects, they seal these valves with a liquid weld which will return to liquid when heated up, this will make it a little easier to get off. I would also recommend using a length of steel pipe on your spanner to give you extra leverage.

ok back to the cutting, you need to allow enough on the top of the bottle for about 2 inches of refractory, I measured up 5 and a half inches from the top of the centre seem and marked them with a mark pen.

cut along the marked line using your angle grinder with a cutting disc, I managed to con my brother in to doing most of the work for me while I cooked him dinner ;-)

once the top has been cut off grind off the sharp edges with a grinding disc

here is by brother grinding the sharp edges off.

radarguy3 years ago
This is SUPER SUPER DANGEROUS! Please recommend against this. Unless you can remove the valve and flush the remaining gas out before grinding you have a potential bomb!

Although I would recommend against cutting it without flushing it out, it is not actually all that dangerous. I cut open an old propane tank a ways back and the sparks from the grinder ignited the propane. Instead of an explosion it simply made a whooshing sound as a blue flame jetted from the slot I had made with the grinder.

blenz3 years ago
It is pretty funny reading all of the posts talking about how dangerous this all is. A couple of years ago the city had to change the supply tap from the main gas line to my house. Anything with these lines has to be welded, but they don't shut down the gas main. They drilled a hole into the main and lit it on fire until he was ready to weld in the new tap! For the old supply tap he did the same after he hammered in a steel plug! the entire time he was welding a 2 foot tall jet of flame was searing the cold February air. When it was all done he checked for leaks, you guessed it by playing his lit welding torch over all of the repair areas. So lets just all agree that "dangerous" is a relative term :)
firesirt blenz3 years ago
If you think about it, you need oxygen for propane to burn, so it really isn't dangerous until it is well mixed with air.
Bald23 years ago
In the past I have had to repair by brazing the odd car gas tank. I think this dangerous operation can be made a lot safer by dropping a few chucks of dry-ice in the tank and leave one vent hole opened and let the CO2 purge bit before you start. With that in place my hand doesn't shake nearly as bad with the torch.