Author Topic: acetylene... not getting enough pressure, need advice  (Read 4266 times)

Offline jonogt

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acetylene... not getting enough pressure, need advice
« on: March 23, 2009, 01:49:15 PM »
I have my oxygen and acetylene cylinders (both 40 CF), and I'm only getting about 6 psi on the output gauge of the acet regulator.  I got my tanks from praxxair and used them for the first 3 or 4 days with no problems at all.  About a month later I was home from school for a long weekend and was met with this problem. 

Would you guys suspect that the problem is in the regulator or the tank itself?  My acet regulator does have a tank pressure gauge, but it doesn't work (got most of this stuff extremely cheap from a school equipment liquidation sale), so i can't determine by using that.  I tried cracking the tank to see if I get the sharp woosh, and it was definately weaker than before.  I've tried using it twice now since finding this problem, and for the first minute it can give almost 10 psi, then it quickly drops to 4.  My uncle has been using oxy/acet torches for years and he seemed pretty confident that it was the regulator, and said I should send it to the manufacturer and they should be able to clean it, but I'd like some other opinions before doing so. 

The main reason I think it could be the tank is because it's the type that requires a tank wrench, and it's just way to difficult to turn.  I really can't beleive that it's supposed to be this hard.  I have to hold my tank wrench in a vice grip to get enough leverage to close it.  Could it have a slow leak? 

Everything I read online when I was considering a torch states that the tank wrench style is the norm, but my uncle said that's crap, cause his has a knob and almost all of the tanks either of us have seen in person do too.  What gives? 

If it's the regulator, is there a good way I can try to clean it myself?  If it's a leaky tank, could/would Praxxair test it and credit me toward a replacement if it proves faulty?


thanks for any help,
-Jon








Offline Bernd

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Re: acetylene... not getting enough pressure, need advice
« Reply #1 on: March 23, 2009, 04:40:23 PM »
Jon,

If you had a leak you would smell the actelyne and if it was in an enclosed area could have had an explosion. So if you don't smell the gas then I'd say either a faulty tank valve not allowing you to open the valve all the way on the tank or the regulator is not working properly. Best to get a new set of regulators, much cheaper than blowing up your place of work, home, yourself and others.

Regards,
Bernd
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Offline PTsideshow

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Re: acetylene... not getting enough pressure, need advice
« Reply #2 on: March 23, 2009, 04:54:21 PM »
DO NOT mess with the regulator, If you have no clue as to what you are doing you can can your family a lot pain and suffering. You don't list where you live the colder the temp outside or the bottle temp the lower the pressure of the gas in the bottle.

If you have bought used tanks, from a private party you may have gotten burned on the tank valve being damaged.  Could the acetylene tank that has a tank wrench be a B tank instead of a 40 cuft one.
Does it look like the larger tank Which is called a bus tank from the old days of being the size they used on the lighting systems for buses. Now used as an tank for air/acetylene torches.

The valve can be leaking, because it is bent, or the seals are damaged from the repeated cranking down to seal it when closing.  @ 70'F the pressure on an acetylene tank is 225psi When full. Because of the low pressure compared to oxygen 2,250psi @70psi.

You open the tank valve no more than one turn, but I was taught in the 60's that turn works and if there is a problem is faster to turn off.

Because the acetylene tanks valve has only one seat and @ relatively low pressure leak by isn't considered a problem. Oxygen tank valves have two seals and should be opened all the way to seat the back seal to stop any leak by.

And the newer tanks all have valve handles, older tanks (acetylene) had wrenches. As the B and MC sized tanks in the above picture.

If the ambient temp and all other things are ok. best safest and cheapest is find out what the LWS will charge for valve replacement. And check what they will charge for a rebuild of the gauges. And remember always take the pressure off the regulator when you turn off the set up. This prevents problems with the springs, diaphragms and seals on both the regulators.
It also can prevent blow out of the regulator when opening a full fresh tank.

good luck and be safe.
glen
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glen

Offline jonogt

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Re: acetylene... not getting enough pressure, need advice
« Reply #3 on: March 23, 2009, 06:26:54 PM »
I bought new tanks on ebay and then took them to praxxair and traded them for full tanks.  From what I understand, gas supply places have to make sure that all the tanks they sell people are within their pressure test date, correct? 

and it's the B tank, not the MC.

Should I take it back to the place where I got it and have them take a look?  The thing about the tank valve not allowing proper flow seems pretty likely.

-Jon

Offline PTsideshow

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Re: acetylene... not getting enough pressure, need advice
« Reply #4 on: March 23, 2009, 07:04:18 PM »
If you had the tank exchanged at the local Welding supply then by all means take it back and have it checked. The B tank is no way near 40cu ft. I have had a bad valve tight like you describe. And have taken it back, it is now a Praxair. But then I have been dealing with the guy behind the counter for 25 plus years.

And while you are there, check into what the regulator will cost to get repaired. Again DO NOT ATTEMPT repairs on the gauges or regulator itself.

glen
"The internet just a figment, of my imagination!' 
 
 There are only 3 things I can't do!"
Raise the Dead!
        Walk on water!
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and I'm working on the first two!
glen

Offline SPiN Racing

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Re: acetylene... not getting enough pressure, need advice
« Reply #5 on: March 23, 2009, 11:22:14 PM »
http://blogs.tampabay.com/breakingnews/2008/04/explosion-level.html (forgot to add the link)

I dont remember the specific reason that the garage blew up... but I live around 10 miles from this location... and when it went up... We heard it.

My brother lives about a mile and a half from it, and he said his whole house shook.

I gather they were finding rubble for a half mile around the location. And it is RIGHT on a busy 6 lane road. It looks like the owner kicked it off himself, from what little I scanned from the article.

Today..the spot is still bare ground with the rubble of the foundation still there. The debris was there for months and months after.

My wife didnt hesitate when I bought the tri-mix for the welder, cause I spent the extra cash on a good regulator etc from the welding supply house.


Be very careful with that thing...
GO to a welding shop and ask them to show you the styrofoam cup trick. Then picture your garage as the cup. You will make sure its top notch.

I look at welding gas tanks like I do with Scuba related air tanks. Your life is 100 percent tied to your equipment. If either of them fails at the wrong time. it goes very badly, very very quickly.
SPiN Racing

Offline jonogt

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Re: acetylene... not getting enough pressure, need advice
« Reply #6 on: March 24, 2009, 09:56:33 AM »
thanks guys, will do.

I'm away at school right now, but the next time I'm home I'll make sure to get all this taken care of.  Right now both cylinders are tucked away safely w/their valves tightly shut.  I wrapped the connections in plastic bags and smelled inside for any gas leaks, and I got nothin.

I won't try and mess with the regulator... unless they have a confident explaination for the problem and they're sure that it will then be fine to use, I'll just buy a new one.  Do you guys think anyone on here might have a used one that I could buy from them?  The cork board only has 4 topics, but I would imagine there are more people actually looking to buy/sell stuff.  For the money I spend, I would rather buy a used but higher quality tried-n-tested piece of equipment from someone here who is upgrading than a new piece of equipment at new price.


If you're reading this and have an acet regulator that works but you don't use anymore, let me know  :dremel:

thanks
-Jon

bogstandard

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Re: acetylene... not getting enough pressure, need advice
« Reply #7 on: March 24, 2009, 10:02:21 AM »
Jon,

It would be very helpful if we knew what part of the world you are from. Then maybe you might even find someone local to help you with your problems.

John

Offline jonogt

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Re: acetylene... not getting enough pressure, need advice
« Reply #8 on: March 24, 2009, 01:05:08 PM »
Overland Park, KS....  It's on the South-ish side of the Kansas City metro area if that helps (midwestern United States).  I won't be there much until summer (mid may), but if somebody is in the area I could arrange to meet up on a Saturday or Sunday afternoon.  Right now I'm in Manhattan, KS and don't have the outfit or the tanks with me, but if any of you guys are near here I could still go for meeting up just to shoot the breeze, discuss projects, etc.

-Jon

Offline PTsideshow

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Re: acetylene... not getting enough pressure, need advice
« Reply #9 on: March 24, 2009, 03:06:25 PM »
They only problem I have with buying regulators used is they are like a cheap watch spring may be working fine when you buy it. And the second time you use it it goes bong! Better to save up or see if the local weld supply will give you an exact estimate on the costs of repairs of the one you already own first while saving up.

glen
"The internet just a figment, of my imagination!' 
 
 There are only 3 things I can't do!"
Raise the Dead!
        Walk on water!
                 Fix a broken heart!
and I'm working on the first two!
glen

Offline Rog02

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Re: acetylene... not getting enough pressure, need advice
« Reply #10 on: April 11, 2009, 01:21:25 PM »
Overland Park, KS....  It's on the South-ish side of the Kansas City metro area if that helps (midwestern United States).  I won't be there much until summer (mid may), but if somebody is in the area I could arrange to meet up on a Saturday or Sunday afternoon.  Right now I'm in Manhattan, KS and don't have the outfit or the tanks with me, but if any of you guys are near here I could still go for meeting up just to shoot the breeze, discuss projects, etc.

-Jon

Hi Jon:

Just caught this thread as I am recently back online after a relocation to the lovely boondocks of NW Missouri.

In a previous post I saw you got your supplies from "Praxxair" but did not specify which "Praxxair" distributor.

I would personally take the set up down to the Linweld store on Front Street and 435 on the Missouri side and have them check it out.  The counter guys pretty much know their stuff, unlike some of the other distributors in the greater Kansas City area, and Linweld has facilities to repair about anything you can think of in the realm of welding equipment.

Last regulator I had rebuilt was a Victor two stage and it set me back about $75 and took a week from drop off to pick up.  "Dave", the chief counter guy, told me he had some "cheap" single stage regulators he could sell me for about the same money, but since I weld with such low pressures (sheet metal, steel and aluminum) we opted to rebuild what I had. 

PM me off list and I might be able to tag up with you some Saturday when I make a run down to Horrible Fright.  I am north of St. Joseph now (Yeah, Jesse James and the Pony Express for all you Brits).
Roger
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