Horizontal vs Vertical Compressor and Tank

Ralph, thanks for this very detailed response. This is very helpful !
 
Yes, well... I can't help myself when the conversation turns to industrial equipment I know something about. It's like a compulsion.;)

And the folks on this forum have been pretty good to me over the years.
 
Our compressor is vertical and has auto drain.

Controlled by the unloader

When unloader opens the vent pressure opens the drain valve and after unloaded drain closes.

Works well.

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I think with verticle tanks, most of the moisture sits on the heavy welded in bung. While the horizontial tanks have a lot sit along the whole bottom of the tank, slowly making iron oxide.
 
tanks that are rusted through under rust pits generally just leak, and lose pressure. the tanks that actually explode are the modern thin, poor quality steel ones that have been subjected to overpressure by either a faulty pressure switch, or some bozo winding it down to try to get more pressure out of the machine. You can't fight stupid! Whilst I would not recomend it, I do know of ppl who have welded tanks with perforation leaks, but you should not try to repair a modern tank, especially one with a seam leak, unless you are prepared to grind the old weld right away, and reweld, which is simply not worth the trouble and risk! One of the great advantages of older tanks is that they usually have inspection plates that can be removed to inspect the internal surfaces for pitting.
 
I recently picked up an old 30 gallon Craftsman 220v horizontal compressor.
The story is, the neighbor had it, never used it and gave it to my friend. He gave it to me.
I would venture to say many of us have these older better quality tanks that have had little use.
When I saw the thread a few weeks ago about the exploding compressor, it made me think about my recent acquisition.
Good idea about the bore scope, I have access to a good one.
At work, we have two large industrial Ingersol Rand compressors that get inspected every five years.
We had one that was at least 40 years old that sounded like the African Queen. (For you youngsters, the African Queen was the name of an old single lung steam engine in a Humphrey Bogart movie, knock a knock a )
The tanks outlived the pumps.
 
Regulation probably isn't needed in a place like North Dakota where your neighbors compressor is 1/4 mile away from you. But in NYC where there might be dozens of people living within the kill zone, and unskilled operators that aren't concerned or aware of common safety practices it's absolutely necessary.

Most regulations come about because of something that went horribly wrong. I worked at an airbag production facility once that had expereinced several fatal accidents and had to change/enforce safety practices to hopefully keep that from happening again, just imagine working at a production facility that didn't have oversight from OSHA....

Here's a video someone put together after his grandfather was severely injured from a compressor explosion.


Please don't make this into a political issue, in the US most of us can choose to live in a community where we feel safe and welcome. There are plenty of low regulation/enforcement areas for those who want them. But in places where your actions have consequences for others, safety regulations are a good thing IMHO.


John
 
hermetic said:
tanks that are rusted through under rust pits generally just leak, and lose pressure. the tanks that actually explode are the modern thin, poor quality steel ones that have been subjected to overpressure by either a faulty pressure switch, or some bozo winding it down to try to get more pressure out of the machine.
Click to expand...

I have to politely disagree. My experience is that corrosion pits in pressure vessels can cause a loss of containment both through pinhole leaks and through catastropic cracking.

The pinholes are obvious, but in other cases the pits are close enough together that when the pressure reaches the critical point the remaining material in the bottom of the pit tears - and if there are other pits nearby you get a 'connect-the-dots' effect and we now have a linear discontinuity and the tank unzips explosively.

"Modern" vs. "Old" vessels is a meaningless comparison. One cannot conclude that modern tanks are of lesser quality than older tanks without knowing the steel specification, original thickness, fabrication techniques, quality control, and other factors which add up to suitability for intended service.

The only difference between Modern and Old, from an engineering standpoint, is that older tanks may be slightly thicker for a given pressure/temperature rating. This is because modern steels - from responsible suppliers - are of generally higher quality than older steels. Higher strength materials can be made thinner - and less expensive - and still retain the same component strength.

In addition, Modern tank manufacturing methods can include automated examination methods to reduce the likelihood of defects in the welds and base materials. That 1950's tank was not subject to continuous eddy current examination of the coil stock, nor were the welds ultrasonically tested after fabrication - those technologies simply didn't exist outside of NASA back then.

The steel manufacturing industry has changed quite a bit in 50 years, as has the commodity vessel business. I would argue that a discount Sears Craftsman air tank from 1970 is of lower quality than a modern tank supplied by Quincy. Even then I'd be guessing unless I had the pressure vessel construction documents in front of me.

The above does not apply, of course, to ultra low cost vessels made from HuFlungPu Good Luck Joy Tank, Ltd. Or to situations where there is some contaminate in the tank which causes environmental cracking. A leaking compressor can dump oil in to the tank. If that oil has a high level of sodium hydroxide or other caustic (used as a detergent in the oil) and the detergent concentrates near a weld - the weld can crack. No pits, no rust - just bang.

hermetic said:
Whilst I would not recomend it, I do know of ppl who have welded tanks with perforation leaks, but you should not try to repair a modern tank, especially one with a seam leak, unless you are prepared to grind the old weld right away, and reweld, which is simply not worth the trouble and risk!
Click to expand...

Agreed, but I would expand this to say that you should not try to weld on a modern or old vessel without knowing what you're doing - and that doesn't include 20yrs of experience welding stuff around the house.

There is no jurisdiction in the US (or UK) which permits anyone to weld on a pressure vessel without following quite a lot of rules. In most of the US, you have to obtain an R-stamp license from the National Board of Boiler & Pressure Vessel Inspectors. The welder has to be qualified in accordance with ASME Section IX, as does the welding procedure. The welding consumables & replacement materials have to be supported by signed documents attesting to the chemical and physical properties, and the examination techniques must follow ASME Section V.

The exceptions are the oil-country states (TX, LA, etc.), but they have similar restrictions and use American Pertroleum Institute standards and not the National Board.

In the UK the HSE controls the repair of vessels much the same way, but with even more restrictions on welder & inspector certifications.

Remember kids... we in the failure analysis business quantify stored pneumatic energy by calcualting the equivalent release of energy in units of dynamite. i.e. "This vessel at such and such pressue equals xxx kilograms of dynamite."

The regulations about licensing compressors may be irritating, especially because they're written by politicians who are generally clueless about the subject they're regulating. But the engineering principles behind the actual technical regulations is sound, and those priciples are based on real people getting really dead when stuff blows up.

-Ralph
 
So for the dynamite formula, What is the rating for a typical 20 gallon tank at 125 psi?
 
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