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On a large commercial job a pipe fitter was putting an air test on his work. 120 psi on a lot of chiller circulating pipe, large diameter. Most of the joints were welded with a few mechanical joints. The test was performed at a free standing chiller building dedicated to HVAC, remote from the main jobsite.

It was breaktime so this guy keeps up with the test alone. His helpers and other trades returned from break to the out building to find a disaster. The air test became a stick of dynamite as a failed mechanical joint exploded. It threw a large welding machine to the roof joists, 15 feet. The welding leads were wrapped liked spaghetti strings up in the ceiling. The rack of copper pipe above was squished flat. Mud and debris was spattered all over the underside of the roof structure.

Okay, let's move down to the foundation where the pipe blowout occured. The failed mechanical pipe joint was below grade, at the footing level. The slab was blocked out to accomodate this tie-in work, but the edges of the floor slab was blown out. The adjacent steel column had its grout blown out from under its baseplate and shifted one inch from location, nearly shearing the anchor bolts. The exterior masonry wall at this location had the bottom shot out and folded like an accordian.

Here's the kicker. The HVAC man was at this inside location of the corner of this building where the blow-out occured. He was blown to the outside, through and with the masonry wall, which then fell on top of him.

EMT was there in moments. The contractors removed much of the CMU wall off the guy, whose only sign that he was there was a protruding forearm and hand, unmoving. They were strapping onto the last segment of wall over the man when the EMT's stopped them to insist on using airbags (something they bought from a glossy brochere, no doubt). The airbags were a joke and they finally let the contractors remove the wall from off the guy with straps and equipment, like they wanted to do from jumpstreet.

He was a mess. His nose layed over his face, his legs a wreck. Lucky to be alive?

Well, they amputated one leg below the knee and his shoulder has painful plates and screws. He has a prosthetic leg now and wants to get back to work. Gotta like this guy. :cool:

What happened? The lawyers will say, but you can either under-tighten or over-tighten a mechanical joint (90ft/lbs?).

My question for you all is this, "How often you take the routine for granted"?

How can a hundred psi kill someone? Volume and location. I walked by, verified and been around it so much that I still have trouble accepting the reality of it all.

I've been walking in minefields and didn't know it. What do you take for granted? But I'm going back to be around it tomorrow morning without worries, and will tell this story to my pipe dude.
 

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WOW!! First of all thank God you're co-worker is alive.

Before I got into the plumbing trade a friend of mine was working for a company that makes large underground tanks for like gas stations. His job was to climb inside these huge tanks and grind all the welded seams and then test the tanks with 5 psi of air. One day while taking one of these tests for granted and not paying attention the cast iron cover blew off and grazed the top of his head!! If it had hit him it would of likely been fatal. 5 psi is a lot of pressure and I never forgot that and brought that near accident into the trade with me. I use 5 psi when testing drains and 125 psi when testing water!! This is code and dangerous!!

Thank you for sharing that accident with us it certainly has jump started my awareness once again.Keep us posted on his recovery and the jobsite.
 

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GCMan said:
On a large commercial job a pipe fitter was putting an air test on his work. 120 psi on a lot of chiller circulating pipe, large diameter.
I have to wonder why a high pressure test, on a large bore fluid circulating pipe, was being conducted with air when the potential for such a disaster is well known.
In my experience, high pressure testing is conducted with water because the properties of water (it's barely compressible) precludes the kind of explosion that can occur with compressed air. Like plumguy pointed out, just 4 or 5 PSI of air pressure is enough to get someone hurt - or worse.
In addition to being dangerous, it can also be costly to conduct air testing in lieu of watertesting. Certain gasket assemblies (like mechanical joints) will frequently pass air when they would otherwise hold water. This scenario can lead to the expense of remedying 'false leaks'.
 

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Pipe guys right, who in the hell would do a test of that size with air?
Any large diameter system we will make our test with as little air as possible just for these reasons.
I am quite sure any plumber can attest to having a test cap blow off on a simple water line test, this can also be quite upsetting.

BJD
 

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Pipeguy and Bjd you guys are exactly right. That much pressure on a large diameter job like that, you are making a bomb.In our code we have the option of testing with water or air. I do mostly residential so I use air(as stated above) which is easier to work with if you have a leak especially in the winter. Draining water lines in February is not fun (in the northeast) and getting wet can ruin one's day real fast!!
 

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GCMan said:
...Most of the joints were welded with a few mechanical joints...The air test became a stick of dynamite as a failed mechanical joint exploded.
A disaster like this points to something that is probably all too often overlooked - it's not just a leak test. You're also testing for mechanical restraint.
I've talked with plenty of guys who mistakingly believe that a properly made up mechanical joint has restraint properties. While you might not be able to pull an mj fitting apart by hand (or even with some mechanical help) if you subject it to pressure over a long enough period of time it will separate without proper restraint or thrust blocking. I can see how mixing mj fittings in a system with welded joints could lead to something terrible like this accident.
 

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Discussion Starter #7
Interesting comments, thanks. Will do some checking around.
 

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Fun story. Back when I was a beginning engineer, I worked for the City of *****. Two crews, one water, the other, a sludge line had a conflict as to which one could lay the most pipe in a day. They were working on opposite sides of the road.
Iwas in charge of the water side and we won with 138 lenghts in one day, all backfilled properly.
The real fun part came when the pressure test guy showed up. We passed and the sludge guys had nearly 200 ft. of pipe exit the ground. Most impressive and I won $500.00. Side bet.
 
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