Another pneumatic test image for the files 3

[StressGuy]

I've been having trouble finding anymore details than what were in the email I received - I embedded the comments into the PDF file to keep it all together. It looks like the yellow pipe originally came off the machine and then went down into the ground.

We've certainly had plenty of discussions regarding the pro/con of pneumatic testing. To be certain, there are situations where a pneumatic test is the correct choice and may be the only practical choice.

Still, when the choice of a pneumatic test is made, Images like this provide the engineer with good ammunition when push back comes from management regarding the extra precautions that need to be taken.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.

 

[europipe]

I wonder why they didn't test with water.

 

[vpl]

Thanks for the photos Ed.

Patricia Lougheed

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[blacksmith37]

I wonder why they didn't have any toughness requirement on the flange forging (assuming they weren't testing at -50F ).
In OCTG business, testing threaded conections with 5,000 -10,000 psi water, failures are still impressive.

 

[StressGuy]

Blacksmith,

That's a good point that I forgot to mention. Just looking at the scale of things, this was a pretty heavy pipe wall. I think people can forget about the effect that has on raising the brittle/ductile transition temperature so that a brittle failure like what the images show is that much more likely.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.

 

[1gibson]

Wonder if any PWHT was performed, or any radiography. I'm far from an expert but it looks like it may have started at the edge of HAZ right next to the start/stop of the weld.

 

[DLite30]

Thanks for sharing.

It's really hard to balance the potential risk of an event like this versus the time/money savings of a hydrotest.

 

[zdas04]

Properly designed and executed pneumatic tests are safe. We are guessing what happened, but I agree with the suggestions above that it was a brittle failure. I did a nitrogen test once where I was starting with liquid nitrogen. I specified a minimum temperature and thank god my inspector stopped the nitrogen driver when the inspectors temp gun read 10F on the pipe wall. The driver had bypassed his heaters and was putting VERY cold nitrogen into the line to "speed up the process". He joined the ranks of the unemployed that afternoon.

I can't say what happened in China, but from the looks of the pipe it could very well have been similar to the moron I got fired that day.

I'm betting that there was an engineering operations failure at the root of this event.

David

 

[BigInch]

Should-a been a law.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus