H_Exchenger,NACE0175,PWHT!!!
H_Exchenger,NACE0175,PWHT!!!
(OP)
Hi all
we have some H_Exchenger in NACE MR0175 condition.
Tube is S.S. 316L & Tube Sheet is C.S.(A-105).
Tubes double expanded & seal weld to tube sheet.
electrode is E-309 & W.P.S. is `nt content PWHT.
but impacted & 200 brinel is it`t hardness.
in start up seal weld is cracked & leak from them.
Please explain me What is the matter?is PWHT mandatory?
we have some H_Exchenger in NACE MR0175 condition.
Tube is S.S. 316L & Tube Sheet is C.S.(A-105).
Tubes double expanded & seal weld to tube sheet.
electrode is E-309 & W.P.S. is `nt content PWHT.
but impacted & 200 brinel is it`t hardness.
in start up seal weld is cracked & leak from them.
Please explain me What is the matter?is PWHT mandatory?





RE: H_Exchenger,NACE0175,PWHT!!!
Leaks sometimes do occur at tube to tubesheet seal welds. Locally remove the cracked seal weld depsoit, and weld repair using E309 with a 250 deg F preheat. After welding is performed , so cool and verify the seal weld repair using Liquid penetrant (PT).
RE: H_Exchenger,NACE0175,PWHT!!!
I think that you need to look at the shell and tube side temperatures and calculate the differential expansion. During start up it may actually be the worse case. Then get the manufacturer of the HE to confirm that he has designed the HE for this (and other) case.
I think that the requirement for PWHT is concerned with the thickness of the welds and not the requirement for NACE. Therefore please can you provide more information about the HE to allow others to answer this part of the question.
RE: H_Exchenger,NACE0175,PWHT!!!
you may be able to reroll and reweld the tubes to repair the problem, I hope you are still on time
ER
RE: H_Exchenger,NACE0175,PWHT!!!
my H_Exchenger is floating head type & differential expansion don`t make stress.
sure service is in Tube .
i think NACE have somethig about weld with different
base metal but i don`t fond it.
RE: H_Exchenger,NACE0175,PWHT!!!
Why is the tubesheet straight carbon steel?
Should this not be carbon Steel (A105) with a stainless steel cladding face on it?
RE: H_Exchenger,NACE0175,PWHT!!!
Why should it be a clad tube sheet? There are numerous reasons for having a straight CS one:- cannot add corrosion allowance to the tubes, availability of st st tubes.
I have made S&T HE's with all CS construction apart from the tubes.
Microeng
What type of floating head does the exchanger have? Is there sufficient room for differential expansion?
RE: H_Exchenger,NACE0175,PWHT!!!
Why the tubesheet must be S.S.?
is it mandatory in NACE?(for H2S content)
the corrosion is`nt my problem becose all of piping is C.S.
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tickle
the room is sufficient for expantion.