What happens when an air compressor tank rusts?

[John K Jordan]

Looks like the weld blew out on that tank. A weld, if done properly, should be stronger than the surrounding metal. I question the quality of that weld.

That's a good point. As a former welding inspector I agree.

But this makes me wonder which welds on which of our compressors have been done properly. That's one reason my shop compressor is in a separate room. Maybe air compressors should be encased in reinforced concrete or kevlar wrap.

Did anyone else ever read the label the little portable tanks we buy at Walmart to carry compressed air from the shop to the lawn mower? Mine has an expiration date. I'm sure they would point that out in court.

JKJ

[Dan Hintz]

I read through the comments on that post. A few folks made some good points about that tank appearing to have been modified. Despite the video's author swearing his grandfather made no modifications, he also said it was purchased second-hand... so mods could have been made by the prior owner. In fact, a later comment said some Google image searching showed several components on that tank that are not there on the "as purchased" version, particularly in the blow-off valve and output area. Considering the age, it's likely that tank was suffering from a bit of rust on the welded seam that was lying on the bottom of the machine (so any moisture would collect along the seam), as well as a faulty cut-off switch, leading to an over-pressure situation.

[Keith Outten]

An observation, if I may.

Scaring people with stories of 10,000psi tanks failing makes for a good tale, but some readers are going to look at their 125-200psi compressors and go "order of magnitudes less, not to worry."

This video shows the explosion of a normal home garage compressor.

John,

Read my first post about a 20 gallon air compressor that destroyed a two car garage in the county where I live. The point is that people are often in close proximitry to pressure vessels of various types and sizes including simple hot water heaters that can cause a catastrophic failure, its not just small shop air compressors that are dangerous. Some may work around large compressors on their day jobs that their company has not been keeping up with the maintenance and it might be a good idea to remind their supervisor about servicing their equipment.

Not to many years ago a group of children were killed when a boiler ruptured at a school and there are countless other accidents that go unnoticed by the media but they are reviewed by safety committees in various areas all over the country. It was the 20 gallon compressor that failed in Gloucester County that caused us to undertake a complete inspection program at NASA and Langley Air Force Base. Several years later I was involved in a review of the 48" main steam pipe that ruptured and killed 5 people at Surry Power Station which kicked off another inspection program at NASA Langley that involved inspection of every single steam line and facility.

If this stuff scares a few people that's a good thing because it a very serious safety problem that is as common as dirt on the floor.
.

[Keith Outten]

That's a good point. As a former welding inspector I agree.

But this makes me wonder which welds on which of our compressors have been done properly. That's one reason my shop compressor is in a separate room. Maybe air compressors should be encased in reinforced concrete or kevlar wrap.

Did anyone else ever read the label the little portable tanks we buy at Walmart to carry compressed air from the shop to the lawn mower? Mine has an expiration date. I'm sure they would point that out in court.

JKJ

In the United States there is a law that requires all air compressor tanks to have an ASME stamp. Its a big steel plate that is tack welded to the compressor tank and it assures you that the manufacturer has complied with the American Society of Mechanical Engineers Boiler and Pressure Vessel Code when they fabricated the tank. This includes both a volumetric inspection and a surface inspection of all welds I believe....but its been decades since I was in the business.

The problem isn't that the welds fail because they were improperly made, its the constant vibration the tank is subjected to when its in operation that can cause a failure which is almost always at the toe of the weld in the heat affected zone.

Go out in your shop tonight and look for the ASME stamp on your compressor tank. If you don't see an ASME stamp scrap the tank.
.

[Randy Rizzo]

Is there a "rule of thumb" to apply to the age of a tank? I suppose there's a lot of issues that factor in, how often was the tank drained? How and where is the tank located? Mine happens to be in an unheated garage. So do you scrap the tank in 1 year, 5 years, how do you know? Then there's the thickness of the tank wall. Does an ASME stamp specify wall thickness? A tank meeting ASME standards would/should last how many years under worst case scenarios? I just went out to look at mine, no welded on plate but a sticker certifying a 26 gallon tank to ASME standards. There's also a warning sticker, "Drain Daily". I did today just to see, can't remember the last time I did it, let's say a lot more water than I would have liked to have seen! THis happens to be a 5HP Husky compressor I got at Home Depot, probably more than 10 years ago. Then you gotta consider the"China" factor. Did the tank actually meet ASME standards or did they just slap on a sticker regardless.

[Michael W. Clark]

I don't believe the ASME tags designate wall thickness. It is likely the heads and shell are different thickness anyway. There is a difference between having the actual tag and stating that it was designed to meet the standard. The actual tag means it was designed, fabricated and tested to meet the requirements at the pressure and temperature listed on the tag.

Some vessels are only designed to meet the standard. They may not have been welded by a certified welder, inspected, or hydrotested. This is not to say that because it was made in China that it is not ASME. I'm sure there are many shops in China that are ASME certified, we have a shop there that is ASME.

[Mike Cutler]

Glen

if a person is getting indications of visible rust, it is time to start looking for a new tank or compressor.
My background, with respect to high pressure, pressurized process systems, is very similar to Keith's background, so I do support Keith's position.
There will always be cases of catastrophic or, infant failure, that cannot be detected, but once you have knowledge of the degradation of a pressurized cylinder, or vessel, you need to act accordingly.
125psi can do a lot of damage given the correct conditions. More than people give it credit for. If nothing else, it's going to be very loud when it finally blows out a small hole. It won't be "polite" about it.

[Michael W. Clark]

Not to hijack, but does anyone have a source where you can buy an ASME compressed air tank?

I saw a few on the internet, but they looked fairly costly compared to a complete new compressor with ASME tank.

Mike

[Keith Outten]

I suspect that the majority of the cost of a new air compressor is the ASME stamp. The requirements to become an ASME certified manufacturer are very difficult and costly to achieve and the cost to fabricate vessels in accordance with the ASME B&PV Code are very high. When I was in the business an insurance company's inspector verified and then issued an authorization for a manufacturer to install an ASME plate. They were always steel plates that were tack welded to the vessel or a piping system and I watched an Insurance Company's Boiler Inspector personally witnessing the plates being installed many times. In a factory I expect the situation is somewhat different but it would still be an official procedure that is very strict and verification would be part of the process. In many cases the paperwork and inspection documentation alone would weigh more than the vessel.

Michael, I expect that it would be better to purchase a new compressor than to try to acquire just an ASME vessel given the costs involved.