RE: Vessels not failing in hydro test

From: <Tony>
Date: Mon Aug 29 2005 - 11:27:00 EDT

An approximate burst pressure for a straight cylinder is:

                         Pfail = (2)(Su)(t)/D

Where Su is the actual tensile strength and (t) is the actual thickness.

Tensile will govern SA106 B up until around 600F.

If the allowable is (1/3)Su, then the cylinder design pressure is 1/3 of the pressure it will take to burst it.

You would roughly have to double the hydrotest pressure to produce a boundary failure (longitudinal fishmouth opening) in the cylinder, although actual values are a bit higher.

-----Original Message-----
From: <a href="/group/PipingDesign/post?postID=vb0NPt21mYJy6Ba6D-_PcerA6Mc35rW8ySjAyXjnJzEGx5sPxThThwYBgMlNS1hx9RqMQ2ilNaxPYKyfqKbhWp90Y5o">PipingDesign@yahoogroups.com</a> [mailto:<a href="/group/PipingDesign/post?postID=vb0NPt21mYJy6Ba6D-_PcerA6Mc35rW8ySjAyXjnJzEGx5sPxThThwYBgMlNS1hx9RqMQ2ilNaxPYKyfqKbhWp90Y5o">PipingDesign@yahoogroups.com</a>] On Behalf Of Tomy John
Sent: Monday, August 29, 2005 3:35 AM
To: <a href="/group/PipingDesign/post?postID=vb0NPt21mYJy6Ba6D-_PcerA6Mc35rW8ySjAyXjnJzEGx5sPxThThwYBgMlNS1hx9RqMQ2ilNaxPYKyfqKbhWp90Y5o">PipingDesign@yahoogroups.com</a> Subject: [PipingDesign] Vessels not failing in hydro test

Hi ,
My question is,
1. Why vessels are not failing in hydro Test, where the pressure is 1.5 times the design pressure.Becauce t=PD/(2*Str)(Hoop stress).

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