pancake repair

[550Doug]

I hace a small pancake compressor and an air leak has developed in the bottom of the tank. I still use it to fill tires etc, but at 100 psi it will take about 15 minutes to leak out.
Here are my options:
1. Clean and weld the hole or put a plate over it
2. Try JB weld
3. get another tank

Option 3 is probably the safest, but are the others actually dangerous? I would think the greatest danger occurs when the repaired section is stronger than the rest of the tank, this makes the JB weld option seem possible.
Any ideas?
Thanks

 

[Anonymous-0]

The tank is most likely rusted out. Replace it. Not worth the risk if it decides to let go. Dave

 

[big jt]

Well here I thought we were gonna talk about what kind of syrup or butter to put on your pancakes to fix them up right LOL.

As to your question option 3 is the only safe one. To give you a idea of what you are dealing with figure up the surface area of your tank. Even just the diameter area (since we are talking a short tank) Multiply it by 100 and I you are talking tons of force that you are trying to contain. For what a new tank or even whole compressor costs it just isn't worth it. This quite literally your life we are talking about here.

jt

 

[Dalex]

Doug , I see this story all the time . If it's so dangerous ,why didn't it blow up when THAT pinhole appeared ?? People get confused between stopping a leak and having the safty valve stick. If you have a brand new tank and the safty doesn't open , there's your explosion. If you fix the leak ,you are right back to where you were the day before it started leaking. If your air hose gets weak at the end and starts to leak , will the whole hose explode if you cut off a foot of it and repair it ?? Not in my experience, Every one of my hoses has been repaired on both ends ! I would take the ball end of a ball peen hammer and tap around the side of the tank and then with equal force tap around the bottom . If it's as solid as the sides, just braze the hole shut. If it dents real easy , it is too rusty and thin to be worth fixing, and will just leak again. If you get the area real clean ,using lacquer thinner or acetone and medium sandpaper, JB might work , but I think oil will still get under it and and it will leak again......

 

[bjb in TX from Ne]

The hole itself didn't cause the tank to blow up b/c the area currently has low residual stress and the steel in the area is still ductile. As soon as you apply heat through brazing or worse welding, you create a heat affected zone around the weld. This changes the property of the steel from ductile to brittle and can cause fatigue cracking that could cause the tank to go BOOM. It take special training, techniques and equipment to weld a pressure vessel safely. Not something the average home mechanic should try.

 

[Pair-a-dice farm]

I've brazed air tanks before and braze hydraulic lines that have over 2000# of pressure, quite often. I may just be lucky but I've never had a problem.

 

[Dean]

JB Weld will NOT work in this application.

Dean

 

[BIG ED]

I've got a "pancake" bad pump but good tank,but shipping probably would sour the deal??? I'm in Georgia

 

[Dalex]

Pair -a- dice has a good point ! I too have braised dozens of steel hyd lines with 2-3000psi ratings , and there is never any problem with them , and some of them vibrate when energized !! Where is that hardening issue now ??

 

[Uncle Ernie]

JB weld it but make sure some of the JB oozes into the tank so it plugs bigger than the hole.

 

[36 Coupe]

I bought 2 small compressors last year for 100 bucks each, gave one to my son.They were on sale this spring for 80 bucks.There may be a lot of weak places in that tank.It may blow up at any time.Punch some holes in it and junk it.If parts are available check the price of a new tank.

 

[circus]

Everyone is correct. That said, solder it closed. The heat needed wouldn't effect anything and soldering is easy.

 

[ASEguy]

You never stated what the leak was from. Rust? Impact? I wouldn't use it. Buy a new tank. Life's too short. No need to make it shorter.

 

[MarkB_MI]

If the tank is rusted out, you would be insane to fix it, particularly when new pancake compressors are available at Home Depot or Lowes for less than 100 bucks.

The subject of repairing rusted air tanks comes up every couple of weeks. The thing to remember is that compressed air has a phenomenal amount of energy. Perhaps the odds of a rusted tank rupturing aren't that great, but if it does it will do a lot of damage.

 

[redtom]

I JB welded a regular style tank and it lasted a few years. I cleaned a bigger area and laid a sheet of metal over the are like you would for a tire tube patch. It worked quite good.

 

[Anonymous-0]

So if it does decide to let go, there's a nice piece of shrapnel to go flying? Dave

 

[MarkB_MI]

Meant to say "less than TWO HUNDRED bucks". Still dirt cheap. Compared to having your head blown off by a ruptured air vessel.

 

[TomH in PA]

A friend of mine was pumping up a tire when the bead broke. He's a big guy, well over 200 lbs, it picked him up and threw him against the wall. I'd never take a chance on a suspect tank.

 

[Fred Martin]

He didn't tell you that he attached a piece of chain to it and anchored it to the pump. ohfred

 

[52 M37]

This has been discussed on here many times.
Air tanks are extremely dangerous to work on.
I am a welder, Certified Welding Inspector and hold the following API certifications. API-510 (for pressure vessels) API-570 (for process piping) API-653 (for storage tanks). I work for a company with an "R" stamp for repairing pressure vessels. I have repaired every type of vessel out there with the exception of Nuclear. I know how to repair and test pressure vessels. I will never repair one of those cheap air tanks.
We only pressure test with water because of the explosive nature of compressed air. The only time we test anything with air is when it is less than 15psig and we are doing a bubble test.
Please stop attempting to repair these tanks before you kill yourself or someone else. Just because the air is leaking now does not mean it will just leak when the repair is done. When welding on these ou can add to the amount of hoop stress causing the vessel to suddenly rupture. Same principal has a handgrenade when the pressure inside gets too great for the shell and it explodes sending shrapnel everywhere.
Of course all of this is just my 2¢ but I have only been doing this for 30 years.

 

[Inno]

Seems to me that repairing a leaking air tank is kind of like drinking and driving. You may get away with it...........you may get away with it many times, but that doesn't make it right and it doesn't make it safe!

Where is trucker? I need a good laugh.

 

[trucker 40]

Ill say this,I am about half crazy.Ive driven tractor trailers for 15 years,over mountains and downtown in big cities,before that I was a mechanic and before that I was a welder.Back when I was in High School I had a car that was a Police Interceptor and it would fly.I drove it at least 90 MPH every where.Some people will tell you these stories like I tell and you think Reah Right!I have witnesses.
Now the other day I was driving a dump truck and I had a flat and the boss told me to take it to the shop and get some new tires.Its a Firestone place with field trucks and several bays.It was hot so I was inside talking to another driver and he pointed to a piece of big inner tube stuck in the insulation in the ceiling.The ceiling is about 15 or 20 feet high.He said thats where that guy that worked here got killed.A tire blew up and it was one of those split rim wheels and when it blew it took him,wheel tire and all and slammed him against the ceiling and killed him.

Many years ago when I was about 20,around 1975, I worked in a gas station.We had a wrecker with those split rims.The bosses son was changing tires on the wrecker and I went in the shop and was looking for something on the workbench and I heard a real loud bang.I thought we were being robbed so I turned around and I saw the bosses son who was a fat guy,and a tire,flying up in the air and he hit the roof and came back down and had all his ribs busted and nearly died.I remember blood was coming out of his ear and mouth,he went unconscious before the ambulance got there,it was pretty bad.

Another time I was working in the shop,and we had a truck tire in the cage and kaboom!The cage tire and all hit the roof,which was about 20 feet up.That was a new recap that zippered out the sidewall.

So now,if the air tank you weld on blows up it can kill you.I dont know why anybody would put JB Weld on a rusted out air tank?The right answer is probably to get another tank.

Since I know there will be people who are going to do this,Ill tell you this,get a piece of new metal the same thickness as the tank.Grind all the paint off of where you are going to weld the patch.Round the corners of the patch.Do not weld anywhere there is a radius and at least an inch away from any radius.Hopefully you have a MIG or TIG and know what you are doing.Check it when you are done for leaks with soapy water at like 10 psi,then I think I would put it outside somewhere and air it up a couple of times before I got close to it.

I already know some people here are going to jump all over me for posting this.However if you buy a air tank from China,I doubt they are any safer right out of the box.Welding on something like that might be crazy.

Whatever anybody does,do not ever braze something like that,especially if you dont know how to braze.I would say arc welding is about as bad as brazing it because you will just make it worse probably.Plus you need to know what you are doing to even think about that,or any way that you would weld it.

So first,it can kill you.You have a MIG OR TIG,and know what you are doing.You are going to put this thing someplace where it wont kill you if it blows up.Then you are going to test it and see what happens before you get close to it.Right?You wont listen to any arguments for arc welding or brazing as they are not what you want to do unless you are a very good arc welder and know what you are doing.Also if you do this and it blows up,its all on you.I already said I was half crazy anyway.You dont want to do something I say to do.I could be wrong.I didnt say to do this anyway.I just said I knew there would be people who would do this

 

[Anonymous-0]

You spoke too soon. LoL Dave

 

[JML755]

Love to read all the posts on this as there seems to be a great difference of opinions and I'd love to see the mythbusters do an explicit test of this. I think they've done SIMILAR tests but could not find any episode regarding a rusted tank.

I've got a 30 yr old Craftsman portable. I brazed a pinhole leak on the BOTTOM of it about 5-10 yrs ago, can't remember exactly. OK, that's my confession and you can call me an idiot. But reading all the posts on this and after searching the Internet for case evidence, it got me thinking.

A rusted tank will have a weak area where the wall has thinned and no longer has structurally sound metal. Any failure from overpressurization would start here. This is on the bottom where the condensation has collected. Working in the industry of manufacturing automation, I have seen stuff "let go". (I have been hit by hydraulic fluid from a burst hose at 900+ psi, got my shirt and face wet). Stuff that blows and is directed at the floor (i.e. bottom of the machine) is a lot less dangerous than stuff that shoots across the shop horizontally. OK, that doesn't make me want to create situations that are dangerous, just saying that some conditions are more dangerous than others. So, are there ANY documented cases of people getting killed/maimed by an exploding air compressor due to a RUSTED tank that wasn't overpressurized? Just asking.

From what I've found by research, OVERPRESSURIZATION due to faulty relief valves is probably a more likely cause of an "explosion". There are also cases of HIGH pressure vessels/lines causing injury. My compressor never gets above 100 psi. If the valve failed, I've probably got a problem, regardless of a rusted tank or not. But I suspect that the circuit breaker may pop due to the motor trying to do more work than it could. This frequently happens in cold weather before the compressor warms up.

Trucker's post about a guy getting hurt by a tire machine is irrelevant. I've built equipment to test car airbags (by inflating them and tearing them to shreds). A LARGE tank pressurized 100+ psi air and a 6" ball valve that opens in 30 msecs WILL kill you if you're standing in front of the valve when it opens. Those machines will lift the roof off of a building if you don't have a blast door open, set car alarms off within a block. All of our tanks were tested/certified. Would I braze a hole on one of them? Or would I repair a hole in one of our large shop 3 phase air compressors? Not a chance.

But, do I feel pretty safe with my compressor repair? Yup. Plus I have so much junk stored in front of it in my garage that if it did go kablooey, my boxes of nuts/bolt, rags, etc. would provide an effective shield from shrapnel. :lol:

Seriously, I respect all of your expert opinions on welding, testing, certifications, etc., but there is risk in all of our daily lives. I am sure that if I followed 135fan or trucker or buickanddeere around all day, I'd find something that I could say, "uh, uh, that's not safe" to which the reply would be "I do it all the time". For example, do you wear arc-flash protection everytime you open a control panel?

BTW, how many of you guys extolling how dangerous it is to fix a small air tank go out on the 4th of July and shoot off fireworks? There are far more injuries from doing this than I've ever read about exploding air compressors.

 

[bc]

One difference is that the old compressors like my 30 year old 3/4 horse belt driven compressor with 10 gallon tank didn't put much out in cubic feet a minute. I have a new pancake that puts out over 5 cubic feet a minute at 90 psi into a couple 1 gallon tanks. Works ok for nail guns but it really winds up fast and doesn't have the volume to keep up with a lot of nailing. That old compressor will run for 5 minutes before it builds up to a 100 psi. I have hooked them up in tandem or in tandem with an extra 5 gallon air tank.

100 psi is still 100 psi than can blow up but the rate of fill makes a difference. My old compressor would probably stall out at some point if the safety valve stuck. The new pancake compressor is another story.

My problem is with those cheap quick connect fittings that always seem to leak depending upon how I twist them, hold the hose, and hold my tongue right. That is the main reason I don't keep any compressors plugged in full time. Hope I don't have to worry about them blowing up.

 

[Anonymous-0]

First of all, don't put me in the same category as trucker. B&D at least has some credentials to back up his reply's. Everyone does dangerous things everyday. The difference is that most of these things are a calculated risk, like driving a vehicle to work and back. Trying to save money by fixing an old rusted out $100 compressor? Come on! Did you see the link on a post by Rod(NH)that showed an exploded air tank and other exploded pressure vessels? An air tank is a high pressure vessel and there is a reason they are certified.

I have seen where 2 PSI would almost blow a person over. I worked at a shop that built large oilfield tanks. They only used 1 1/2 to 2 PSI to test them. When you open the valve to let the air out, you'd swear there was 100 psi in the tank. The valve is only 3/4" and if it were 6", I bet it would blow a person over. If a tank is rusted or somehow compromised, how do you know what the over pressurization is? It could only be 40 PSI. It's not about how often it happens, it's about what happens if it does blow up. It also doesn't make much difference if it's a large 3 phase compressor or a small cheap one. 100 PSI is 100 PSI! Lot's more volume in a bigger tank but that's the only difference. Ever heard a tire blow out with only about 30 PSI. There's not a lot of difference. Dave

 

[trucker 40]

I knew it would happen!Here you are on here saying that you think it would be alright to BRAZE an air tank.Then a bunch of blah,blah,blah about how the tire machine(?)I was talking about was irrelevant?

I said nothing about a tire machine.I gave examples of where people were hurt when a TIRE exploded off of a wheel with less than 100 PSI.My air compressor kicks off at 125 PSI.Some go to 150,maybe higher.

When I do say something, you dont try and belittle it!Duh!

I was also thinking today about all of this myself and I cant think of anybody having a tank blow up that it wasnt the pop off valve being bad.

I will go as far as to say that some of these guys will say stuff thats not true,to try and justify some point they are making.

Here is what Im trying to say.I was looking at an air tank that was made in China the other day and saw a real nasty looking weld on it.After I looked some more there was stuff wrong everywhere.Undercut,slag,places where it wasnt finished right.It was in a store,but I wouldnt buy it.Im surprised it would hold air.I doubt they even test this crap enough to see if it holds air or not.

So it brings us to this,I dont see what is so bad about somebody who knows what they are doing,welding an air tank.The problem is there are lots of people who dont know what they are doing,and they are working in factories,turning out crap,and selling it here.

Some of these guys posting here think they know everything,and they will try and prove to you that they do.They will tell you that you cant do this or that because it will kill you or somebody else.Well yes you are right.There is all kinds of stuff that would kill you before fixing an air tank would.I wouldnt go so far as to say that I would braze it.Braze weld is about the same as soldering.Its not strong enough,but I know its been done.

Ive cut a couple of cars in two,then took a good front half and a good back half and welded them back together.An old man showed me how to do this.As he was explaining this all to me and how to overlap it and all he told me that he was riding down the road one time with this guy back in the 1960s and he was telling him about doing that to a car,cut two in two and make one out of the good parts and that he brazed it together and told him to look at the windshield post.He did and he said there was a real bad looking braze weld on it,and he made the guy stop and got out.Now there is a place where everybody draws the line of what they will and wont do,but I dont want to ride down the road at 60MPH in a car thats brazed together.If you think about it,neither do you.I guess its better than walking maybe,at least until it breaks in two pieces.

So yeah if the air tank blows up it can kill you.There is probably a good chance a new one from China could blow up.Oh yeah,it was welded in China.I dont feel good about that even if it is new.Also what can anybody say about a tank thats welded together being made worse because somebody welded on it to fix it?I dont get that.

If you weld so poorly that your patch blows off,you have no business welding anything.Im real sure about this.

Also it stands a better chance of the pop off sticking and blowing up because of that.Hey you can buy a pop off thats made in the USA maybe.I think that would be a good idea after seeing that blown up tank,even on a brand new China one.It could still stick and blow up the tank though.

A rusted out tank is not good,but where are you going to find a tank?You can buy a new compressor,but what if you dont have any money?Its hard to buy anything if you are broke and still have electricity,a welder,and know how to do it.

So partially you are right.Yeah it probably is not the best.You dont want to braze it,and if you weld it any kind of way,you need to be a good welder and know about the radius stuff and use a good piece of the same size metal.Then if you are lucky it wont do anything unless the pop off sticks.You have to make a judgement call if its rusty as to whether its worth fixing.If you think its worth fixing,then fix it if you can.I cant see some of their arguments against fixing an air tank.
I have had to fix air tanks on big trucks and Ive seen where other people welded on an air tank on a big truck.You can buy a whole compressor or 3 for what a big truck air tank costs.

 

[trucker 40]

Now you too? Alright 100 PSI is bad when it explodes.Should you fix an air tank?An air tank that was welded in China?What kind of test do you think they gave it?Plus the tank is welded to start with,how is welding on it to fix it going to make it worse,as long as you theoretically know what you are doing when you weld it to begin with?

Im not sayin you are wrong.If My tank starts leaking ,Im going to look for a tank or an air compressor.Im saying what makes welding a Chinese air tank a bad idea?Also if welding an air tank is no good then why is it made that way?

If you are broke,you tend to fix what you have rather than buy a new one.If you are a good welder,why would it be bad to fix an air tank?I guess your answer is it could explode,but it could explode before you weld it.It could explode right out of the box if welding an air tank was wrong.

I see how the tank blew up because the pop off stuck.I have even seen tanks that exploded before.On a big truck a few times I saw an exploded tank and it blew out the side.Im thinking a pop off valve stuck there too.

Sure nobody wants anybody getting hurt,but sometimes when you look at one of these arguments it doesnt really stand up.

Im thinking that you have a lot better chance of being walking down the sidewalk and a passing big truck has a blowout right next to you,and flying shrapnel kill you,or something exploding like a gas line,or an earthquake opening up the land and swallowing you than your welding an air tank will kill you.

I think I will say its not recommended.I wont say air tanks are just blowing up because of even poor welds.Air tanks are blowing up because of stuck pop off valves.Plus they are rusting out from the inside because people dont drain them.Being lazy and not draining your air tank can kill you if it rusts out and explodes then couldnt it?What actually happens that Ive seen is that it just leaks air.You wouldnt want to fix it wrong,and its not recommended to try and fix it,but there are worse things than that.