Re: Schedule No. and High Cycle./ Low Stress Pi

From: <Christopher>
Date: Mon Jun 18 2001 - 10:44:00 EDT

>1.What is the concept of the Schedule No. e.g. Schedule 40. How does it
>relate to the pipe wall thickness?

Developed from bundling schedules based on weights used long, long ago. There is no simple relationship to thickness--use Machinery's Handbook for info and don't forget the 12.5% thickness undertolerance.

>2. What is the basis of the 7000 cycles for the stress reduction factor f of
>1.0 shown on Table 302.3.5

If it's the same rationale as the boiler code the rationale is that anything below 7000 Hz is such a low number of cycles that non-cyclic service governs.

>4.The calculation of the wall thickness for straight pipe under internal
>pressure is farily easy using the hoop stress or the modified Lame equation
>per 304.1. But what about the calc of wall thickness considering external
>pressure such as those used in double jacketed pipe
Use external pressure methods such as shown by Appendix 5 of Div 1. For long thick pipes the calculation is fairly simple because the tube buckles into an elliptical shape, so rib stiffeners don't help. Short thin-wall pipes are different and may need rib-stiffening. I can't tell you what the piping code reference for this is since I don't have an up-to-date version handy.

Christopher Wright P.E. |"They couldn't hit an elephant from <a href="/group/PipingDesign/post?postID=l7qwRMyqzCtGpuS1YNaiq6_RLbMayge1sy1qXkb3iLNwEkLRLu-G2-X8XETRYZfiRANawnDxlYjUQJZx1yM">chrisw@skypoint.com</a> | this distance" (last words of Gen.

___________________________| John Sedgwick, Spotsylvania 1864)

<a href="http://www.skypoint.com/~chrisw">http://www.skypoint.com/~chrisw</a> Received on Mon Jun 18 10:44:00 2001