On Jan 17, 2008, at 6:26 AM, M. Engineer wrote:
> The test pressure producing hoop stress of 90% of SMYS
> is for newly constructed in-plant piping.
I've seen this before on the list and it really seems like a high
proof factor. It isn't uncommon to have local secondary stresses that
exceed the hoop stress by 50% or more. Testing the a hoop stress level
of 90% of Sy will cause visible distortion in some areas, which n turn
is grounds for rejecting a vessel during a shop hydro. Much more
important is the possibility of extending a sharp defect like a weld
crack to the point where the vessel or pipe run ruptures during the
test. Or you might extend the crack to the point where subsequent
stress cycles ultimately brings about a fracture. I've been through
this a couple of times, and it really could spoil your whole afternoon.
> There are
> several
Christopher Wright P.E. |"They couldn't hit an elephant at chrisw@skypoint.com | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania1864)
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