How do I keep my compressor from exploding?

[kwindham]

I've been trying to research how to refurbish a used bauer verticus compressor by reading the manual and forum entries here, but haven't encountered a lot of specific information about possible failures that can occur and how to prevent them. Specifically, I am most nervous about swagelok tubes possibly flying apart violently at 3600 psi and/or the effect of minor external rust spots on the tube. Also, I don't have much information about the history of the unit and wonder about the integrity of the moisture separators. I have heard that they can fail even more violently than a swagelok tube rupture.

This unit was built in the early nineties and is weathered for sure. What sort of things should I check / test before bringing the unit up to full pressure for the first time? How worried should I be about a final stage water separator failure? The compressor unit is in its own sheet metal enclosure, which is itself in a heavy gauge steel storage shed. Is this enough protection?

Is Bauer's sheet metal enclosure enough to absorb flying debris in case of failure or do I need to do something extreme like surround it with sand bags just to be safe? I'm not really sure how to gage the risk, especially since I've never worked with high pressures like this before.

 

[Wookie]

Your tubing is rated to 21,000 PSI. Your fittings are rated for 6,000 psi. Take a chill pill. Look inside the final moisture separator like you would a scuba cylinder to see if there is any pitting. If there is, replace it. Same for the filter tower.

And, if something does explode, it'll take out the sheet metal enclosure, the building it is in, as well as you, if you're standing within 100 feet. Your wife will be pissed.

 

[rcontrera]

Awww ... Wookie is just messing with you. Your wife won't be pissed.

He is right about takin a chill pill. Yes, high pressure air can be dangerous. Yes, fittings, tubing, cylinders, etc can fail. But it is primarily the separator and filter chamber that can hold any volume of air that can do damage so do the inspection.

Don't mess with sandbags since it may restrict the air flow and reduce cooling. Change the oil regularly, insect for leaks regularly, change filters regularly and keep it all clean and cool. You should have no problems for a long time that didn't come with the machine.

 

[iain/hsm]

IMHO Your concern is justified, depending on the age, condition, service life and hours run on your compressor in question.

My experience on the failure of a small 3/8" diameter tube at 3600psi is that it will bruise your eardrums at a distance of 3 foot (1 metre)
However for reference a 2 inch diameter tube at only 300 psi can kill you. Its the pressure over volume risk and where your body bits are at the time.

On small Bauer compressors catastrophic failure of the separators was of concern some years ago when they were manufactured under the German TUV standard with only a poor 2.3:1 safety factor. These old parts should have been recalled/replaced at the service intervals.

Consider also that these quoted steel fittings pressure ratings are when new, not when they are old and rusting. These quoted "Pressure ratings" should also be verified as to the safety factor and condition. Most pressure ratings quoted are for hydraulic oil liquid service at 3:1.

When a liquid service line fails it makes only a puddle. Where as for gas the more conservative 4:1 working pressure to burst is recommended.

For the separator the "pressure cycling" of the vessel has been subjected to is critical. To be fair most of the explosions have been on auto dump separators that cycle from full working pressure to zero in an instant four (4) to ten (10 times) an hour with the old TUV 15,000 pressure to zero cycle design life for a compressor running 1000 hours a year it's a three year life!

Bauer incidentally as with a number of others use standard steel industrial hydraulic fittings for there compressors taper threaded into soft aluminium.

Over time the steel fitting thread corrode and expand as oxidised rusting metal, this expansion "roots out" the soft aluminium female thread. At best it's a replacement part during service inspection, at worst it takes an orbital trajectory back to earth.

To give you an idea of the damage a separator failure at pressure will cause the enclosed photo shows a new separator failure and its operator condition.

Hope it helps and doesn't put you off, In practice before you buy a second hand compressor a detailed inspection and a known life history with a logbook of the pump is always better than a second hand blind purchase off some pump dealer or internet Ebay vendor with there obligatory "just serviced" claims and vague attention to detail to the hours run. Iain Middlebrook

 

[Doc Harry]

...Specifically, I am most nervous about swagelok tubes possibly flying apart violently at 3600 psi...

As you should be. Welcome to the world of high-pressure gas.

Do not compromise on your fittings and make sure than you connect everything properly. The tubing should be anchored at regular intervals to minimize the risk of having flailing segments of tubing flapping all over the place. Why do you think they call them "whips?"

... the effect of minor external rust spots on the tube...

That's why you disassemble, clean and inspect everything every year.

...or do I need to do something extreme like surround it with sand bags just to be safe? I'm not really sure how to gage the risk, especially since I've never worked with high pressures like this before.

Some facilities place the operator controls behind reinforced concrete walls. If you can afford to do that, then go for it.

Here's the "gas station" between Tulum and Playa del Carmen. There are concrete walls to protect the fill station operators.

Me... I just put the cylinder between my legs and figure that if anything bad happens, at least it will be over quickly...

 

[frogman62]

Like Doc, I have a concern for older equipment that MAY not have been maintained or checked periodically.
I used military filters and moisture traps for many years because most were manufactured with 4 to 1 safety factor and the use was 3000PSI or lower. BUT with the advent of 5000PSI common applications, I went to installing all commercial new equipment on my compressors. Check valve in HP lines also limit the amount of whip. The compressors are all military surplus, however everything after the final stage is new stainless HP tubing. I also limit the length of lines from the compressor to the moisture trap and filter.
IF the COMPRESSOR fails, you have an oily mess and some small pieces bouncing around but no explosion. If the moisture trap or filter fails you have a major problem and lots of damage and flying parts, so check them at least every year. I was in an auto repair shop many years ago when an O2 cylinder was knocked over and broke off the valve. The cylinder went through two cinder block walls and stopped 1 city block away. I don't ever want to be that close again. Caution on handling filled cylinders is also a concern.
Jim Shelden

 

[kwindham]

Hey thanks for the detailed replies, and the pics. A failure is actually less destructive that I imagined :blinking:. I pulled the interfilter as was suggested earlier, but the threads are rusted enough that the retaining ring won't let go. I'm afraid to fight it too much so I haven't been able to inspect the interior, however, I did notice that Ian was correct about this separator. It is indeed marked as an older 2.3:1 safety factor aluminum vessel. I figured that it was a foregone conclusion based on the stuck ring and safety factor that it must be replaced, but the bauer 4:1 safety interfilter replacement is $1300. Wow!

Now I'm back to square one. A local outfit here says I should just get it hydro'd and forget about replacing it, however it bugs me that I can't get into it. I'm tempted to use heat, but don't want to ruin the temper. Thoughts?

 

[Wookie]

Not tempered, it's aluminum. Most likely corroded in the threads. Place the base in a vise with lots of sheet rubber to protect it, screw the two bolts into the holes in the lid meant for them, use a long end wrench with cheater bar to unscrew the lid.

 

[frogman62]

I sell the commercial filters shown on my web site for $515 plus shipping. 5,000PSI working pressure.
Jim Shelden 316-992-0505
sheldensportinggoods.com

 

[kwindham]

http://www.bauergroup.com/pdf/produkte/ersatzteillisten/serviceunterlagen/behaeltertausch_e.pdf

Just thought I'd share this link with you guys. I ran across this technical bulletin on Bauer's website which shows the dangers of using aluminum pressure vessels under repeated fatigue stress loads. In short, they recommend mandatory replacement of aluminum interfilters after 15 years or after their cycle lifetime. Here's a pic of a failed aluminum filter: