Re: [PipingDesign] How is Tensile Strength Established by Tube Spec?

From: <Christopher>
Date: Mon Jan 14 2008 - 14:33:00 EST

On Jan 14, 2008, at 12:38 PM, Ken Nisly-Nagele wrote:

> I'm working with an unlisted B31.3 material for a tubing spec. I
> want to
> determine the allowable stress for the flexibility analysis.
You need to use a listed material with B31.[anything], and you've discovered the reason why. Materials used for code purposes require that the minimum mechanical properties and weldability be established or the structural design would be invalid. There are ways around it, but they require that properties be established by testing. In your case the 1016 material probably doesn't have a reliable yield point because of variations in manufacture or thermal treatment. If it were me, I'd say no-go--use something permitted by the Code.

If you're doing some kind of design analysis, you can use Machinery's Handbook to get typical properties and reduce them by at least 15% and run the calculations, but that won't make the design conform to B31.3. I've been asked to pretend that I were rating an existing design to find the 'Code' pressure, and I don't proceed until my client realizes that it's not going to be a Code-equivalent vessel with Code design margins--and that the exercise has all the value of putting lipstick on a pig.

Christopher Wright P.E. |"They couldn't hit an elephant at chrisw@skypoint.com | this distance" (last words of Gen.

.......................................| John Sedgwick, Spotsylvania
1864)
http://www.skypoint.com/~chrisw/ Received on Mon Jan 14 14:33:00 2008

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