Welding and pressure transients

Welding and pressure transients

Postby pauldear » Sun Sep 13, 2009 7:17 pm

Hi Peter,

You mentioned elsewhere that pressure transients were blowing your welds? I was wondering how transient they are. We use various flow systems at work (for totally different porpoises), and in some systems we have pressure-buffers such as short bellows sections (metal), or glorified balloons which sit inside the system and can absorb some of the transients. May be completely out of the question for your application, but thought I'd mention it. Might save over-engineering everything to cope with a transient problem.
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Re: Welding and pressure transients

Postby Peter (Nebula) » Sun Sep 13, 2009 8:43 pm

Hi Paul

Thanks for the advice, and yes - your suggested method of transient damping isn't a bad one at all. It amounts to lowering the Q of a tuned circuit formed by the existing system and is one way of damping the positive feedback that would otherwise contribute to potentially damaging resonances.

Unfortunately, my problem is practical rather than theoretical in that I'm currently forming interfaces bosses by building weld up upon weld - something that I'm now convinced is a very bad idea (I can almost hear the mechanical engineers cringe). The answer is simple, ie do it properly. I'm now machining the bosses individually from stainless and welding the complete units in place.

This isn't as big a job as it may sound and I should be ready for another test in couple of days.

Best

Peter
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Re: Welding and pressure transients

Postby Peter (Nebula) » Mon Sep 14, 2009 10:47 am

Of course if I get a tank failure (the test ones are rated at 405psi) then I might need to find out just how big these transients are!

Best

Pete
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Re: Welding and pressure transients

Postby pauldear » Mon Sep 14, 2009 7:10 pm

Ah yes, I can see that creating something out of weld is not a great idea - I'm sure the metallurgical properties of weld are less than great! Any chance of piccies for Wired? Would you be interested in being one of the featured teams if they decide to go with the article?
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