Ive been using a mix of sweated fittings on copper tube and NPT. But I've only seen NPT used on natural gas which is at very low pressure. I was wondering what is approved for propane at pressures upto 40psi?

Thanks

On my gasser I just used black and brass pipe fittings. I pipe doped the threads and just rechecked all of the connections with soapy water. No leaks. I used re-enforced fuel line for the hose. :)

NPT connections will take far higher pressures than 40PSI. They are used for air lines which are 120+, and hydraulic systems too. Be careful mixing fittings IE; galvanized, and brass. This can lead to dissimilar metals corrosion.

Thread it , dope it, run it up, and check for leaks.

For a dissimilar metal connection - iron to brass, etc. look for what are called "di-electric unions". Can be found in many plumbing supply houses. They are often used in hooking up water heaters and water inlets to low pressure boilers. Joins two pipes together and features isolating insert(s) that reduces the amount of electricity created. Two dissimilar metals will expand and contract at different rates creating an electrical charge, usually measured in millivolts (its how they make thermocouples used as temp indicators - dissimilar metals bonded together permanantly). At least that is the way I remember it ... :)

Thanks for the info.

Since it's propane at high pressure, I want to take reasonable precautions to do things right. I slip a piece of that flexible spiral electric cable armor over the hose leading to the tank to protect it from cuts and burns.

Do I really need to worry about dissimilar metals in this case? My set up is indoors and the climate is bone dry. So far I have never seen a trace of corrosion where brass fittings are mated to black pipe.

The only time to worry about corrosion of fittings is copper to steel. If you need to connect a copper pipe to a steel pipe a brass nipple or coupler stops the reaction of the dis-similar metals. Or use a di-electic union if you like maintaining gaskets.
Rob

The only time to worry about corrosion of fittings is copper to steel. If you need to connect a copper pipe to a steel pipe a brass nipple or coupler stops the reaction of the dis-similar metals. Or use a di-electic union if you like maintaining gaskets.
Rob

I have propane plumbed into our house for the kitchen stove---black pipe, pipe dope, and the official inspections said it was "well done".

BTW it's *not* "expand and contract at different rates creating an electrical charge".

Do NOT put pipe dope or teflon tape on or near the burner, it will emit toxic fumes at temps much over 400f.

I use teflon sealant on the connections away from the forge and copper pipe and flare fittings on the forge. The only time I've had a leak was the time we were demoing on a windy day and the copper tubing vibrated the brass fitting loose on one of the burners. Made a little flare but not an event. Shut it off, tightened the fitting and went back to work.

Frosty the Lucky.

Do NOT put pipe dope or teflon tape on or near the burner, it will emit toxic fumes at temps much over 400f.

I use teflon sealant on the connections away from the forge and copper pipe and flare fittings on the forge. The only time I've had a leak was the time we were demoing on a windy day and the copper tubing vibrated the brass fitting loose on one of the burners. Made a little flare but not an event. Shut it off, tightened the fitting and went back to work.

Frosty the Lucky.

hmm I usually put teflon tape on the MIG tip since the NF threads dont seal up well. I assume you are talking about flourine being emitted. I dont mean to be contentious. I am just trying to understand clearly. With the quantities involved should one worry? Flourspar is used in ceramic work and also sometimes for forge welding. Teflon coated cookware can get overheated on the stove. (Not that I have ever done that but it happened to a friend of mine ) Is the pipe tape worse?

Yeah, flourine is pretty toxic and accumulative in effect. Overheating (smoking) a teflon pan is a good way to check out permanently. Flourine is also one reason I don't forge weld SS; maintaining the phosphorous and calcium levels in your bones is important to avoid floppy syndrom.

To avoid needing pipe dope don't tap the 1/4" x 28 FPT for the mig tips so deeply. Stop tapping at a point where the mig tip will stop before reaching the shoulder. If the fittings leak at this point it doesn't really matter as it's inside the burner and will just richen the mix slightly, zero chance of an accident.

Frosty the Lucky.

Thank you everyone for your advice.

Frosty, I will try that idea of tapping short for the mig tip. I remain unconvinced about the risks from the Teflon tape but thank you for taking the trouble to explain the issue.

Just a note about all this dissimilar metal fittings on lp gas. Here in NJ in the student shop the gas inspector told me that using dissimilar metals of any kind was against code. When I pointed out that the burner orifices were brass and some copper and the feed lines were black iron all I got was a blank stare!!! :blink:

I can't necessarily back this up with data and I know myself included often fabricate against what is specifically recommended and I have done this myself, but I have been told by more than one knowledgeable party that sweat soldered copper fittings should NOT be used for LP.

Hey ThomasPowers ...
Please send me a PM please tried to send you one but it said you couldn't receive. I want to update my understanding of thermocouples ... check this out first http://en.wikipedia.org/wiki/Thermocouples

sorry for highjacking the thread

Tim