CW,
you are correct about the relief valves (10% accumulation in specifoed
circumstances)
, but the pressure eqpt can go to 10% over up to
100hrs and 33%overpressure up to 10hrs as excursion, but it has to be
recorded and you have to know this isnt exceeded... rarey happens.'' i'l
have to look up the ref.
you are also correct , its heavily abused and misinterpreted. You cant plan
to do it in advance.
then its not an upset , but a design condition... many pi...ing matches on
that one.
>
> On Sep 7, 2005, at 5:19 AM, Venkat hariharan wrote:
>
> > What if an existing piping is rerated to a higher pressure and the
> > available pipe thickness just satisfies the new operating pressure,
> > Is the 1.5xtimes test pressure is mandatory in this case? Can the
> > piping withstand the new test pressure? Operating temprerature is
> > around 350 deg F. Code allows only upto 33% overpressure for less than
> > 10 hrs at any one time.
> How certain are you about this? Again, referring to the ASME PV Codes,
> no such over-pressure is permitted under any circumstances of service.
> Commonly-held mis-information is that a 10% over-pressure is permitted,
> but that's an incorrect interpretation of the rules for safety relief
> valves, which state that the internal pressure may rise 10% only while
> the relief device is opening fully.
> Christopher Wright P.E. |"They couldn't hit an elephant at
> chrisw@skypoint.com | this distance" (last words of Gen.
> .......................................| John Sedgwick, Spotsylvania
> 1864)
> <a href="http://www.skypoint.com/~chrisw/">http://www.skypoint.com/~chrisw/</a>
>
>
>
>
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Received on Wed Sep 07 17:52:00 2005
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