Re: elevated temperature hydro when client wants to go to flange limits.

FYI - re the temp re-rating question on hydro, next is how they do the caramel thing.

the answer from a constr guy who has done heaps of hydro, nothing else for many years for a big contracting is that hydro to the flange limit on the offchance the line service will change is nuts. We agreed it excess stresses the line needlessly. He cited cases of HGL difference where the added head pressure made the line stress much higher than it should be to satisfy some pedantic bookworm who wanted the max press reached at the top, including to the flange limit. Gets more serious with temp "up-PRESS" RErating. My thoughts are if the line changes service the odds are rehydro will be done regardless, likely theres a hardware change anyway.

he agrees it should be derated (for high temp). Note it shouldnt exceed the allowables of the flange at temp limits and the YS anyway. my concl. i'm going with the flange limit tables at temp. compared with 1.5P st/s and will hydro to the least allowed and that will set the line limit. Interpretation and understanding is the key. I wonder how different code inspectors rule.
ABSa has policy guidelines but nothing on this. Do any other AI agencies have internal policies
and rulings??

cheers
Al

• Original Message ----- From: John Luf To: Al Kaye Cc: aluser2 Sent: Friday, January 13, 2006 5:29 PM Subject: Re: elevated temperature hydro when client wants to go to flange limits.

   Gentelemen,

   I'm in PR on a shutdown and my wife is visiting this weekend so I won't digest this and other matters until next week sometime.....

   Sorry but the Wife is numero Uno!

     ( I do have glynns book (ie.woods + baguley:: CASTI))

     B16.5 My 1996 and 1999 copies say 1.5 times. (@100F rating)

     Does 8.2.2 rev2003 says something different. (something new?)

     My understanding , from B16.5 1996/1999 is that  the limits at temp
     are set by the tables, for the appropriate material group limited by the
values
     at the appropriate temperature. But this is operating limits.

     From Glynns notes:
     2. Compare the calculated value [eqn 24]  to that allowed by para 8.2.2.
     Looking at B16.5 1996/99 clause 8.3.0 it isn't an allowance, but a minimum
required.
     Isn't 2003 para 8.2.2 just the same.

     There are two separate minimum requirements; based on ambient test temp.
     Eqn 24 min test pressure  1.5 P.St/S (b31.3 eq24)
     and 1.5x (+/ up to25psi) minimum (B16.5 Clause 8.3)

      Is there a new equation for an "allowance" in 2003?

     My point is shouldn't the hydro (to flange limits) of 1.5x be derated if you
are
     operating at higher temperatures, and thereby the upper pressure derated

     I'm looking for a max allowed (in temperature ratio scenario) not a minimum required.

     It appears this is not addressed unless the new B16.5 says something or the intent is

     there (to derate for high temp) but not widely understood or applied.

     One way would be to take 1.5x (rounded up to next 25psi) of the
     Table limited working pressure at temperature, and limit to that.
     This would seem logical.

   Best Regards,

   John C. Luf
   Cleveland Ohio U.S.A when I'm not in Austria

   Member B31.3, Piping Engineer - Stress Analysis, Pipe Supports, Component Design, and Surge Analysis... and according to my daughters master of unimportant trivia

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[Non-text portions of this message have been removed] Received on Sun Jan 15 22:50:00 2006