I had to put some Tri-Clover fittings on a S.S. tank yesterday that is being used to make hard liquor. It’s a stand up tank that measures 2’ in diameter and 5 ˝’ tall. Because it has to deal with a consumable product it has to have smooth welds on the inside, but it’s not possible to weld the inside. The only way to achieve this is by back purging the inside with argon, crank the heat up a little and allow the metal melt on the inside for a full-penn weld. So I threw a hose inside connected to a bottle at about 15cfm for about 5 minutes and then I welded the bottom fitting. I had it capped off so none of the argon could escape. I looked inside the fitting to see that it did work okay. So I started the purge again for the top fitting and waited. After about 20 minutes I still wasn’t sure if it was fully purged and didn’t know how to test it until I came up with an idea. I used a lit lighter and placed it down inside the tank to see if there was any oxygen left and it still burned. So I checked it 10 minutes later and the lighter went out as soon as I got it close to the top of the tank. So I was good to go on my welding.
Just thought I would share my new trick on purging big tanks with you all.