Repairing an air compressor receiver

My big compressor has a couple of pinholes in the bottom of the tank, no doubt caused by the previous owner not getting the water out. It’s a good solid machine that runs well so I’m reluctant to replace it. I’m thinking I could grind the holes back(they’re tiny at present) to some better material and then plug weld them or put a patch over? Is this feasible? It would definitely be cheaper than replacing the tank or building one. Or is there a way I could use an existing pressure vessel and modify it to suit? The tank is about 200 litre size.

If you have pinholes the the entire bottom section has probably seen better days, if you a a accomplished welder you could do a cut and shut.

First thing I would do is inspect the internals. If it's encrusted with scale it could be a waste of time affecting any repair.

STOP !
Do not use this tank for another moment.
You are in danger while it is in use.. Replace the tank.

If the air compressor tank is punctured even a little while working at peak capacity (or near to), the result could be an immediate, explosive release of all pressurized air through the puncture mark, potentially ripping apart the tank completely and sending dangerous metal shards through the air.

If in doubt a phone call to your local Non destructive test company or State Govt Work Health and Saftey Dept will verify what I have outlined here.
These tanks are certified pressure vessels and should only be built by certified welders. Commercial tanks are certified,stamped and recorded.

Commercially used compressor tanks are subject to regular inspection and report in my state of Queensland.

I will assume the same applies in the rest of the country.

Grahame

Quote:

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Originally Posted by Grahame Collins

STOP !
Do not use this tank for another moment.
You are in danger while it is in use.. Replace the tank.
Grahame

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Video of someone getting injured by an exploding compressor air reservoir:
https://www.youtube.com/watch?v=KVP_...nel=Davidevans

I'd agree with Grahame - treat your existing tank as cactus - don't mess with it.

While I wouldn't want to encourage anyone to repair or modify their own pressure vessel, if someone was to go ahead and do it anyway then the very least they should do is a basic pressure test afterwards using a non-compressible medium such as water. Plenty of info online on how to achieve that practically in a DIY situation, and I know some members here have done in on used receivers for their own peace of mind.

You could definitely use a different pressure vessel and adapt it (as in plumbing adapt - not a cut and shut!!).
LPG tanks and bottles are pressure vessels, and get tested at 330psi from memory. Auto LPG tanks are often free. Not saying they are an ideal replacement, but logically safer than repairing or using what you have now.
Used air receivers can sometimes be bought cheap. I was lucky to pick up a used receiver from work that was being upgraded. Its a vertical one so put it outside the shed on a concreted pad and just plumbed it into the output of my smaller compressor to provide about 200L of additional storage.
You may also pick up an old 3ph compressor with decent tank for cheap as your average home workshop guy wants single phase, and businesses want modern high capacity compressors.
Just check the tank is in good condition - most of that sort of size will have an inspection port. Selling the motor and pump separately should get a few dollars back.

Keep in mind that you don't need a single receiver of exactly the same size - potentially you could get by with a smaller one, or use multiple smaller ones to get the same volume you have now.
Also gives you the opportunity to separate the compressor motor/pump and the receiver if there was any advantage for you in doing that (ie so you could stick the noisy bits in a sound enclosure etc).

Steve

Thank you Lamestlama ,

A classic "picture is worth a thousand words scenario "

Its to the point and no misunderstanding of what could happen.

To just add a little bit more to the information pool here is a Utube Vid from Mr Pete- Tubal Cain.

https://www.youtube.com/watch?v=XfLzFR-TOBc

Watch carefully at 9mins.25 seconds to appreciate how thin the material was. I was aware of this many years ago and always drained the shell after each use.

Grahame

Quote:

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Originally Posted by lamestllama

Video of someone getting injured by an exploding compressor air reservoir:

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To be fair, we have no idea why it failed, but a 200l receiver does give me pause for thought.

Quote:

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Originally Posted by riverbuilder

My big compressor has a couple of pinholes in the bottom of the tank, no doubt caused by the previous owner not getting the water out. It’s a good solid machine that runs well so I’m reluctant to replace it. I’m thinking I could grind the holes back(they’re tiny at present) to some better material and then plug weld them or put a patch over? Is this feasible? It would definitely be cheaper than replacing the tank or building one. Or is there a way I could use an existing pressure vessel and modify it to suit? The tank is about 200 litre size.

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Air compressor repair can be simple. The air compressor is built into the pressure switch assembly. So when you repair your compressor, you turn off the switch, then no risk. When the air gets into the arc while you're welding, it causes air bubbles to form within the molten metal, creating a weak and very ugly weld. However, the company should do thicker-walled pressurized air compressor tanks with the automated K-TIG welding method, usually only available through welding companies. If you fear repairing, you can go to the company that improves your air compressor.

Quote:

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Originally Posted by erjri

Air compressor repair can be simple. The air compressor is built into the pressure switch assembly. So when you repair your compressor, you turn off the switch, then no risk. When the air gets into the arc while you're welding, it causes air bubbles to form within the molten metal, creating a weak and very ugly weld. However, the company should do thicker-walled pressurized air compressor tanks with the automated K-TIG welding method, usually only available through welding companies. If you fear repairing, you can go to the company that improves your air compressor.

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Hi erji,

Firstly ,welcome to the Metalwork Forums.

Thank you for your reply to the Repairing an air compressor receiver thread.

You have replied to the original posters question. His location is in Australia where the where the Keyhole Tig process was invented.
https://www.k-tig.com/keyhole-gtaw-welding

In any case the poster is inquiring from a diy standpoint .It would be probably cheaper for him to buy a brand new quality compressor air receiver, rather to pursue a Key hole Tig repair.

I have worked in the pressure vessel industry and in Non Destructive testing and very much doubt the use of this process would be permitted for use on compressor air receiver repair.

If you explore our pages you will find bits and pieces of interesting things all over the place.

Go to the FORUM box at top LH corner and click on it.

A drop down menu appears and you can select Forum Home at the top of the drop down menu list. Scan down through the pages to look at what we have.

Please make sure read the Terms of Use -our Rules - pretty standard for many forums these days.By joining the forum its automatic that they apply to you as a member.

Normally the soft ware works so you can't post pics or links until 10 posts are made ( or such links and pics are cleared by a mod)

Its anti spam thing.

There's a number of sub forums forum that might be parallel with your some of your interests found as described above.
You may like to go to our Welcome Wagon and introduce yourself and your metalwork interests.

https://metalworkforums.com/f300

If any questions contact me via PM and I'll try to help you.
Again, a big welcome to the Forums.

Grahame

I was called away and forgot to add this. Its the most salient point ,really. Tig 101 ,you might say.

The Tig process requires a virtually spotless surface and the same on the penetration side.

The air receiver cylinder in question is crusty inside -no way of cleaning it properly from the air receiver inside. That discounts the use of any tig welding process- keyhole or not.

Grahame

Thanks for all the replies, appreciate the experience.
I cut a hole in the tank yesterday and found that the whole thing was covered in rust scale and tendrils all around it, it was s lot worse than I expected it to be just at the bottom. So it’s a scrap job and purchase a new tank from Pilot compressors , a 200 litre tank is about $850, with certification,and my motor and pump should fit straight on, so it’s a fairly good result.

Just as a side note the reason I suggested it could be repaired is many years ago I did some unpaid work at a large welding company they built and routinely repaired air receivers.

I know of two welders who died trying to leak test a new pressurised receiver because it was late in the afternoon and draining it and then refilling took too long. My welding teacher who was a DLI inspector had to do the investigation on the incident and he said their bodies left large dents in the roof of the building.