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Having trouble with maintaining pressure to burner


MrMaelstrom

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A bit of background:

Back in October/November I made the switch from forced air to NA. My previous burner was a fuster-cluck that had been hacked and welded and recreated a few times as I switched forges/air sources. That being said though, I was able to achieve welding heat with about 2 PSI coming from the regulator, and my 30lb tank had no problem with that. The issue I had with the forced air was that I needed power wherever I went. Although not frequent, I do occasionally take my forge places and try and get people interested, and needing an extension cord had gotten a bit tiring.

Fast forward a bit. I installed my new T-Rex burner. Everything seemed to be going fine, but I noticed that after a few hours, the output pressure began slowly dropping, and I was unable to actually maintain pressure for any decent amount of time. Given that I was now running at 10 PSI, I figured that I was pulling too fast out of a used tank (It was starting to frost a bit). Filled the tank, had the same problem.

Given that the regulator had been bashed around a lot, I figured it was time to retire it and bought a new one. New gauge, new regulator and I was still having the same problem with a completely full (and not frosted) tank. Went out and got a 100lb tank just to see if that was really the issue (I was just using this as an excuse to buy one), and for a while, didnt seem to have a problem. After a few weeks of use, the issue came back again so I figured that the tank was running on empty. I went out, got it filled and still have the same problem. When I start off, I have no problem setting it to 15 PSI for forge welding (even with 3" high-temp blanket and a sealant I cant manage to get it lower than that and still get to 2100+) but after about an hour or so I begin dropping and it isnt long after that I am below 10 PSI.

I have my regulator plugged right into the tank and a ball valve just off the regulator. From there it goes right to the burner. I am thinking that the regulator might be bad, but it is pretty new.  I have a lot of experience dealing with forced air burners, but am pretty new to NA ones, but i doubt that the burner is the issue. 

Any help would be appreciated. 

Thanks,

Dan

 

 

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Is the jet clean? A small bit of dirt or sand could cause that. If it is loose in there and keeps blowing up and blocking the jet, then falling back in the hose when you disconnect and fiddle with tanks and regulators. I would clean the jet and disconnect the fuel line to blow it clean with compressed air. 

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If you dont find any debris or blockage in the jet or line then place the propane tank in hot water to eliminate the cooling effect. I have seen the tank pressure drop in half without there being frost present. Also feel the regulator to make sure its not freezing up.

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Ok,

 

So, there doesnt seem to be any blockages within the hose or the jet. The regulator is cool, but not cold during operation, and I dont really think the tank is cooling. Its about the same temp as it is in my garage, about 60 degrees F. 

 

Something I did notice though, is that when I took the line off the regulator, turned on the gas and opened the ball valve on the other side, the regulator dropped to zero. Is that how that is supposed to work? I thought the regulator regulated the outgoing pressure and that it shouldnt matter whether I have a line hooked up to it or not, if it is set to 15 PSI, it should stay at PSI whether the ball valve is open or closed.

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Not on an open circuit. A regulator only allows a maximum psi, not a minimum so the deliverable volume is an issue. It shows pressure through the jet, an open hose or fitting allows enough flow the pressure will be below the gauge's read level.

I've been thinking about your problem and the blockage was my first thought, followed by icing in the regulator or jet but if those aren't the problem I'm kind of stumped.

Okay, here are a couple back ground issues that might help me get a handle: 1, Are you using propane rated hose? 2, did you use teflon tape or ANY thread sealant?

What size Rex do you have?

Frosty The Lucky.

Edited by Frosty
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Yeah it might be a bad reg but the pressure starts out good and diminishes after time. A transient blockage is what it sounds like to me but between the tank and reg? Perhaps moisture is collecting in the reg and freezing up without the exterior temp falling cold enough to ice over?

Hmmmm. Do you live in a high humidity region Mr.Maelstrom?

Frosty The Lucky.

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Frosty,

Yes I am using a propane rated hose. It is actually the same hose I have had for years. Didnt think there could be something wrong with it, I would say it was the least banged around out of most of my gear. As far as sealant goes, I have teflon tape on everything - even the threads from the tank to the regulator.

It has been pretty humid lately. Recently, Kentucky got a nice foot of snow (A lot for them, I just moved here and it isnt that much for me), and with that melting, and the rain we have had, It is a bit sticky out. I honestly couldnt be able to tell you what the humidity was when I have had this problem in the past. 

I haven't fired up the forge since Monday, given that I have been trying to finish up a few pieces and that involves a lot of one on one time with my grinder. Since I have cleared the lines, and taken the thing apart to check it, I think we need another test. I will report sometime this evening if I notice anything else, or if the problem has resolved itself. 

Thanks for the help. 

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So, just to be sure, i replaced the teflon tape on all my fittings and made sure once again that my line was clear of debris (turns out I had a small leak right out of the regulator). Fired the forge up, set it to 10 PSI and in about half an hour I was down to 5 PSI, and sputtering about a 20 minutes after that. 

I did not mention though previously, but I am unable to turn the regulator's pressure up after it has gone down and by closing and opening the ball valve doesnt consistently return me to the pressure it was before I closed it in the first place. For example, if it was set at 12 and I closed/opened the valve it might go to 10 next, then I do it again and it might go back to 12.

Once again, thanks for the help, guys.

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Sounds like a bad regulator to me. Propane is a very chemically active gas, using the wrong hose can cause the hose to degrade. Using T tape on a propane system is a BAD thing. Propane does weird things to T tape I think that's because there are so many different kinds. There is a special paste thread sealer for propane sittings. Check with the propane dealer for the paste thread sealant, the real dealer, not the corner quickymart that sells propane. <grin>

If you've been using T tape all along I'm thinking it's degraded and contaminated the reg. I suppose certain daughter compounds might have attacked and damaged the reg. I'm not a chemist so I'm speculating on the reg. erosion. idea. The Propane guys got pretty excited when I even mentioned T tape to them. I was double checking, the guy who hooked up our kitchen range top. He'd told me a couple scary stories about T tape and propane when he saw I'd sealed the pipe to run it into the kitchen with it. He took every single fitting apart and cleaned the snot out of them and pasted the threads to reassemble.

Frosty The Lucky.

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I had an acetylene regulator that would drop pressure as you used it. Start out at 5psi and within a few minutes you would see it down to 2 psi. When I got it used it had been left cranked in for a long period of time so the internals were damaged. 

Local Welding supply shop overhauled it for reasonable price

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Thanks guys. I will look into getting some paste and seeing about either replacing or repairing the regulator. Frosty, I knew that propane was pretty reactive (took quite a few chemistry courses in school), but I didnt even consider that it didnt party well with the teflon tape. One of those things that makes sense in hindsight. 

If it works, great, if not, I might be back      ;)

 

Either way, thanks again!

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<snicker> I think I would like your Mum.

Mine had some choice sayings as well, we're probably lucky they were half a world apart. One of Mother's things was flash cards till I was so sick of the things I learned the subject in self defense.

Frosty The Lucky.

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Yeah, it sure would. Not only clean underwear but BATHE regularly! I can just see Earth's Head Mother shaming ISIS into utter humiliation then making them sit in a corner till they were straightened out.

OOH, another up side to Mothers running the world, politicians would have to get REAL JOBS! Oh wait, I remember some of the . . . disagreements some of our mothers had when I was a kid. Maybe not so great a world.

I know for sure the boys WOULD take out the garbage on time, clean out rooms and not track "stuff" on clean floors. Floors WE cleaned I'm sure.

Frosty The Lucky.

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So, quick update. 

I still haven't gotten a new regulator yet, but I did try and fire up the old one to do some mokume gane. I had no issues with it what so ever running at 10 psi for a few hours. 

In a week or so, I will.see if the news regulator makes any difference

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  • 1 month later...

The world would be a very different place if Mothers ruled it.

We'd all have to wear clean underwear every day... just in case we were hit by a truck 

​My grandmother used to say a poor excuse was better than none. :-)

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  I have witnessed the aftermath of someone using teflon on a computerized/calibrated pneumatic function generator.  Not pretty, the stuff totally clogged up both the pressure and vacuum plumbing.  As a result, I only use teflon on water, and for compressed air I now use gasoila when I'm dealing with compressed air, unless the fittings are self-sealing/flare fittings.

  I've always used that yellow stuff on propane, since it's good enough for building code.

  As far as oxy/fuel torch rigs go, all of those fittings are precision brass flares and don't need sealant unless something is wrong.  If you think it is leaking, spray with soapy water, look for bubbles, and tighten a little at a time.  Don't crank too hard though or you will strip the threads.  If it's really tight and still leaking' have the bottle/regulator/fittings checked at a weld supply shop.

Hope this info helps someone.

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