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Up Topic Welding Industry / ASME Codes / ASME-B31.3-REPEATED PWHT-IS IT ACCEPTABLE?
- - By Nalla (***) Date 12-08-2009 01:49
Dear Friends
Process Piping - Carbon Steel Piping - 6" Sch XXS ( 21.9mm )- PWHT done on the same butt joint twice. RT done after 1st PWHT-It passed.Is it acceptable to ASME B31.3?
What harm done the joint ( weld metal & HAZ ) undergone PWHT twice, in terms of Mechanical Properties.... etc.
Parent - By 3.2 Inspector (***) Date 12-08-2009 05:13
I ask you, is it acceptable?
You are the only one here with knowledge about your PQR/WPS, project specs, etc.

Parent - - By G.S.Crisi (****) Date 12-08-2009 10:21
My opinion:
Why did you carry out two PWHT's if only one is sufficient? Possibly because the first one wasn't well done and it became necessary to make a new one.
The RT was OK, the second PWHT was OK, so everything is OK. The PWHT is carried out at a temperature below the critical one (i.e., the one at which ferrite becomes austenite and viceversa), so there are no structural changes in the metal. About mechanical properties, tensile strength and hardness decrease after PWHT, but as the first one wasn't well done, they decreased all they had to decrease after the second one. Regarding grain growing, it depends on temperature and time, so, once you've reached the soaking ones, the grains grew all thay had to grow. 
So, don't bother and have pleasent dreams.
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - - By Nalla (***) Date 12-08-2009 23:17
Dear Friends
Why 2 time PWHT?- Simply due to miscommunication/late receiving data/reports.1st PWHT + RT done at Batam , the spools sent to Singapore. But Traceability Records/report came in very much late.But Hydro-Test must go on. So we did the "2nd PWHT followed by RT-It passed.Client say not acceptable.-WHY? -JUST HE REFUSE TO ACCEPT!
Lets say RT after PWHT Failed-Then it has to be repaired >> RT >> 2nd PWHT >> RT. So does the mech. properties/TS / YS affected much more, isn't.

Does ASME Codes prohibit  2 time PWHT on the same joint eventhough RT Passed before and after PWHT?
Parent - By js55 (*****) Date 12-09-2009 13:58
I think maybe they need to tell you why they think its unacceptable.
With the info provided I see nothing that violates the code or compromises the weldment.
Parent - - By G.S.Crisi (****) Date 12-09-2009 17:34
Let's put our Horse Sense to work.
The piping is designed and built according to B31.3 "Refinery and chemical plant piping". Refinery and chemical plant piping is subject to heavy corrosion. It's a well known fact that metal supporting stress is much more sensitive to corrosion than metal which doesn't. That's why piping in oil refineries and chemical plants must undergo PWHT more often than piping in power stations, for example, designed and built to B31.1, where corrosion is much less.  
When B31.3 was written, the only reliable method to know whether the PWHT had reached its aim, i.e., soften the weld to make it less sentitive to corrosion, was hardness. The harder the metal, the more stress it's supporting, and consequently the less resistant to corrosion it is. That's why B31.3 had a requirement that other codes (B31.1 for example) did not: after PWHT the Brinell hardness of the weld had to be less than a certain value; if I remember well was 240 BHN. If not, the PWHT had to be repeated so as to achieve that figure. The hardness requirement is still valid, even though nowadays you can measure very precisely the residual stress by means of a portable Xray difractometer. You know, standards take time to adapt to technological advances.
Conclusion: B31.3 Code foresees the possibility ot make a second PWHT when the hardness requirement hasn't been achieved, so I can see no reason why your piping can't be approved.
Giovanni S. Crisi
Parent - - By ssbn727 (*****) Date 12-09-2009 21:27

I think you really meant to say that there are different types of corrosion found between chemical/process piping and power plant piping that are unique to their own individual environments as opposed to always finding more corrosion in one environment over the other - if I may. ;)

Parent - - By G.S.Crisi (****) Date 12-09-2009 22:57
what I wanted to say is that the corrosion found in a power plant, where B31.1 applies, is far less severe than that found in a chemical plant, where B31.3 is to be followed.
In power plant you have mainly water and steam, some chemicals for boiler water conditioning and some chemicals for the demineralizing plant. The chemicals for boiler water conditioning (hydrazine, morpholine, chelating agents) are only weakly corrosive. The chemicals for the demineralizing plant (sulphuric or hydrochloric acid and caustic soda) are strongly corrosive but they're limited to the demineralizing plant, i.e., a small part of the total one, where their pressure is low and their temperature is room one. B31.1 doesn't require that a maximum hardness be achieved after PWHT, because it considers that corrosion isn't a main concern in a power plant, although it can't be forgotten.
In a typical chemical plant highly corrosive substances like acids, alkalies and others reign all over the place, often at high temperatures (when corrosion is more severe) and high pressures (when a weld rupture is a real danger). That's why B31.3 requires that a maximum hardness be achieved after PWHT. If I remember well, that maximum is 240 Brinell. It's a well known fact that the harder a metal is, the less resistant to corrosion. 
I hope I've answered your question.
Giovanni S. Crisi
Parent - - By ssbn727 (*****) Date 12-10-2009 00:39
Yes I uderstand what you are saying, but what I was trying to point out to you is the fact that there are different types of corrosion cells, and I didn't mean stronger or weaker when I used the word different types of corrosion which are unique to power plant situations like inside boiler tubing where certain types of pitting, or erosion & caustic corrosion situations can only be found in a boiler of the types which are found in power plants as well as unique yet similar types of corrosion cells where the results of the same type of corrosion may be different based on either the type of boiler being used, or the fuel being used to heat them as well, and then there is the design factors as well that need to be taken into consideration such as the materials and the variety of components found in a utility boiler which will be different than what is mostly found in boilers used in chemical plants, pulp paper plants, process refinery plants as well...

There's a whole bunch of corrosion going on in the anti pollution devices found in utility plants that have been replaced more than once already since their initial installations as well which really doesn't get mentioned that much either, but I'm not going to get inot that here because that's a whole different animal all together. ;)

So water formed and steam formed deposits are quite common in utility boilers that originate from other areas of the boiler that are causes of corrosion, as well as from both short term and long term overheating which deos play a role in accelerating the creep potentials at various locations in the tubing/piping along with other components as well, then there's the clogging of the superheater tubing which can vary widely in the types of deposits found that eventually lead to clogging these pipes completely eventually causing them to bulge then rupture at a variety of locations and resulting in catastrophic failure more often than usually reported!!! ;) Of course there's also Water wall fire side corrosion which occurs in boilers no matter where they are used.

Then there's the usual caustic, and chelant corrosion cells that from over time as well as low Ph service corrosion as well as during acid cleaning also. Then of course there's the uniqueness of oxygen corrosion in far higher levels in utility boilers than would be found in chemical plants or process refineries too. But what is really unique about utility boilers or even some paper mills would be the coal ash type of corrosion, or the oil ash corrosion like from black liquor in the paper mills which is why a lot of duplex SS cladding was addded to these black liquor plants in the seventies in order to mitigate some of the oil ash corrosion found in a variety of locations and on many different components.

Then of course there's cold end corrosion during service as well as dew point corrosion during idle periods... Hydrogen damage, materials deficiency cavitation, dealloying, graphitic corrosion, corrosion fatigue cracking, stress corrosion cracking, etc. In other words, all of these corrosion environments and situations and unit cells occur in boilers both in utilities as well as in chemical plants but, certain corrosion cells form uniquely in a utility boiler, yet do not always mean that one is stronger than the other because that was NOT my point! My point was that there are certain corrosion cells that occur only in utility type boilers and NOT found in boilers found in chemical or process plants with the exception of the black liquor fuel used in a paper mill, meaning that the fuels used to heat the boilers are an important factor as to why some of these unique corrosion cells even form at all in a utility plant as opposed to a different type of boiler used in a chemical plant which more than likely would be using natural gas of some sort to heat the boiler up to produce the steam from the water running through those tubes/pipes - CAPECHE??? In other words, the B31.1 part of the system in a power plant... So I hope I clarified what I was initially attempting to point out to you previously Giovanni! ;)

Parent - - By Nalla (***) Date 12-10-2009 06:02
Dear Friends
This subject getting very interesting, though my question very simple.This is Process Gas Piping installed on FPSO.Am I violating the B31.3 Code?
Thanks a lot for very interesting info.
Parent - - By 3.2 Inspector (***) Date 12-10-2009 06:47
Does your WPS support 2 times PWHT?
As I wrote to you several days ago, YOU has the answer :)

Parent - - By Nalla (***) Date 12-10-2009 14:47
Hi, 3.2 Inspector
Is there such requirement in WPS/PQR as per ASME Codes? If yes pls advise respective section.

I used WPS/PQR with PWHT for Process Piping with THK>19mm.I use the same WPS/PQR to repair the RT Failed Joints.Code do not prohibit that, isn't

Parent - By 3.2 Inspector (***) Date 12-10-2009 15:01
I suppose your WPS has the PWHT holding time written?

Parent - By ssbn727 (*****) Date 12-10-2009 15:45

it would be a lot easier for all of us to communicate with you if you and possibly advise you better if you would just write out in your next post, everything that is written in the WPS/PQR that you are working from... This way there can be a lot of wasted time and effort going back and forth going over each and every line or feature eliminated, and realistically speaking of course, you may receive the appropriate answer for your query in a relatively efficient manner although, I believe Professor Crisi has already given you the answer notwithstanding any other pertinent informattion which you my or may not have revealed to us as part of your initial query! ;)

So please give us all of the details and facts, and please take your time in translating it as best as you possibly can because when one rushes to translate to English, sometimes the order in which the words are translated tend to become translated in a reverse or random order which only adds to the confusion that's always part of the translation process.

Most important is NOT to hold back from including all of the necessary, and possibly helpful information which may or may not be part of the WPS/PQR... For instance, There has to be a reason as well as an explanation describing why the client refused to accept the work, so you might want to include this in your next post as well as all of the information written into the WPS/PQR as well as anything in these reports that were not filled in also. Do not hold anything back!!! No matter how insignificant you may think it is!!! ;)

After all, we can only help you with your problem if you make every effort as possible to communicate in as much detail as possible, with as much information as possible, by describing as much as possible what exactly you are working from, otherwise it tends to read as if the blind are being led by the blind to walk across a very busy interstate just before rush hour traffic when speeds are averaging at about 67 miles per hour - CAPECHE???

Parent - - By G.S.Crisi (****) Date 12-10-2009 17:19
read again the Conclusion of my posting of December 9.
No, ASME B31.3 does not prohibit to run two PWHT on the same weld.
Now, I notice that the piping was pre-fabricated in Batam and shipped to Singapore. So, the contractor is from Batam and the client from Singapore. Is English their mother language? If not (mine isn't, so nothing against those whose mother language isn't English), is the client sure to have understood exactly what the Code says? I've lived and worked my whole life in non English speaking countries, and more than twice the apparently big problem was due just to the poor knowledge of English of both parties.
Giovanni S. Crisi  
Parent - By ssbn727 (*****) Date 12-10-2009 17:54 Edited 12-10-2009 18:06
Yes Nalla I understand what you are trying to say, but if there is an explanation from the client as to why they rejected the spool regardless of what language it is written, then you need to interpret it to whatever language you can understand in order to get a better understanding as to why they rejected the second PWHT you or Batam performed on it!!!

In other words, ask them for some form of clarification as to why they rejected it, so you can then have something to debate their reasoning, and since there isn't anything in the code which prohibits it, and it was not specifically prohibited in the contract documents, you will then have the basis to dispute their claim. but the main point I am trying to show you Nalla, is that you need to make a better effort to communicate with them regardless of English not being your "Mother" language because after all, if the customer speaks English, then if you want to satisfy the customer, you need to communicate better with them via the English language regardless whether the components were made in Batam or not! The same would be required if the circimstances were in reverse!!!

So find out what the people in Batam actually did in as much detail as you can get, then translate it as accurately as you, or with the help of someone else who is fluent in their "mother" language, who can translate the language they speak in Batam which I suspect is Philipino correct? Once this is performed, you will have a better understanding of what is written in the WPS/PQR with respect to PWHT as well as in the contract documentation just as Professor Crisi and 3.2 alluded to in their previous posts... And if there is nothing that suggests at all that more than one PWHT is prohibited, then resubmit the dispute of procedure rejection or whatever it is that has been agreed to in the contract documents to them and see what their reaction will be then, and make sure you include to ask where in the code does it say that the extra PWHT is not allowable, so that you can finally clarify it once and for all! ;)

Parent - - By js55 (*****) Date 12-10-2009 17:40
The question has been answered a couple of times.
I would also suggest a thorough review of the PWHT sections of B31.3.
It is quite concise and readily understandable (its the impact testing stuff that is messy-but thats another thread).
And essentially, if it isn't prohibited there it isn't prohibited.
There is no code limit to the number of times you can cook a piece.
And the microstructure really doesn't care if its done all at once or many times.
With some alloys of course stresses may become a consideration but for medium or low carbon steels, a practical limit of two or three cooks is virtually insignificant.
Parent - - By 3.2 Inspector (***) Date 12-10-2009 17:50
But his WPS shold still list the time at temp?
Obviously only is impact testing is required.

Parent - By js55 (*****) Date 12-10-2009 19:40
I would agree time at temp needs to be addressed in some manner connected to, or directly on, the WPS.
We usually handle it with PWHT travelers that determine specific requirements beyond code requirements.
Parent - By MBSims (****) Date 12-11-2009 02:56 Edited 12-11-2009 03:29
I think it's been said here (several times) already, but the answer is no.  The number of times PWHT is performed is not limited by B31.3.  The only time limit is that the WPS must be qualified for at least 80% of the total time at PWHT temperature IF notch toughness testing requirements apply.  This limit is in ASME Section IX (QW-407.2), which is referenced by B31.3 for qualification of welding procedures and welders.
Parent - - By G.S.Crisi (****) Date 12-10-2009 17:06
If I've understood well, you're talking on corrosion that occurs in boilers, either in utilities (i.e. those that produce electricity sold to the general public) and industrial facilities (i.e., those that produce electricity used in industrial plants). Both are considered power boilers, because both produce electricity.
May I remind you that power boilers fall under the jurisdiction of ASME Code Division I. 
Nalla, on the other hand, is talking about piping in a power station, which falls under the jurisdiction of ASME B.31 Code for Pressure Piping, Division 1, which applies to Power Plant Piping.
I agree with all of what you say, but you're talking about boilers and Nalla wants to talk about piping.
Giovanni S. Crisi
Parent - By ssbn727 (*****) Date 12-10-2009 17:33

No need to remind me, of the differences... I was merely expressing a point regarding corrosion which was part of what you brought up, that's all. ;) Nothing more!

Nalla needs to put forth IMHO, a better effort in translating what he is attempting to ask in his queries because trying to understand what he asks can sometimes be very confusing as well! ;) He doesn't need to be perfect I might add, but he sure needs to do a better job than the way he is presently attempting to do so.

Parent - - By Shane Feder (****) Date 12-11-2009 00:34
Hello Giovanni,
I think you will find Nalla is talking about B31.3 - Process Piping and not B31.1 Power Piping.
He mentions FPSO so it is oil or gas piping he is talking about.
Parent - - By Nalla (***) Date 12-13-2009 03:24
Dear Friends
Applicable Code ASME B31.3 / WPS/PQR Qualified to ASME Sect IX. Please refer attached
Attachment: pwhtdetail.pdf (187k)
Parent - - By ssbn727 (*****) Date 12-13-2009 05:00 Edited 12-13-2009 05:03
Pardon me Nalla... But could you please explain to us why you are showing us this test report from PTS Pte ltd. that is dated all the way back to 02/29?/1996 (was that a leap year?)? In other words, what is the relevance of this test report if you don't mind me asking you??? And is the ASME Section IX code you're working to is of a 1995 version??? The other question that comes to mind is why the ABS stamp on WPS # 7088-88???

Parent - By 3.2 Inspector (***) Date 12-13-2009 06:51
That should have been typed in bold Henry.

Parent - - By Nalla (***) Date 12-13-2009 09:04
Dear Sir

1)The attachment is part of WPS # 7088-88. WPS has no expiry date.
2) It is norm practice in this region PQR Qualification and all the related tests witnessed by Third Party,ie ABS.

From the above positive responses, one thing is clear. Multiple/Triple PWHT on CS Butt Welds does not have any effect on micro-structure of the weld zone/HAZ.

Btw, your good  advise on "PWHT is not required for carbon steel under B31.3. refer to 341.3.1 (a)".  

BTW, 3.2 Inspector-Does my question sound stupid to you?If so pardon me.

Thanks to all the answers.
Parent - - By ssbn727 (*****) Date 12-13-2009 17:24
Hi Nalla!

I didn't give you that advice: "PWHT is not required for carbon steel under B31.3. refer to 341.3.1 (a)". 

So I'm not going to take any credit for it...Please do not take this the wrong way, because I don't mean to be rude towards you intentionally, but it is very difficult for most if not all of us to understand what you are trying to ask us sometimes, and it's not like we do not want to help you or anything like that at all... It's just hard for most of us to understand the questions you pose in here, and that is why sometimes the thread can take quite some time in order to finally come to the conclusion of what you were asking us in the first place.

Is there a possibility that you can use some sort of translating web site to use as a possible aid for us to better understand you??? Are you currently using one now? I don't know what your native language is, but is it at all possible for you to type in the future, in both your native language, and in English as well so that some of us can use translators also to get hopefully a better understanding of what you are actually asking??? I know that it sounds like at first, too much of a request, but if you do this only a few times it will help us as well as yourself in understanding each other better that eventually there will be no need to type your questions, or statements in both languages as we will become more familiar with how you express yourself and you will become more comfortable in expressing yourself in English as well...

So in summary, this spool is to be used on a tanker that carries some sort of gas, or does it connect to the tanker so the the gas can be off loaded? is it LNG?

Parent - - By Nalla (***) Date 12-14-2009 01:13
Dear Sir
I only asked your for advise/thought in regard  of this statement-"PWHT is not required for carbon steel under B31.3. refer to 341.3.1 (a)".

Parent - - By ssbn727 (*****) Date 12-14-2009 02:38
Hello Nalla!

If the Client's contract documents require PWHT, then it must be performed for whatever reason the EOR (Engineer OF Record) for the client requires it... The governing code according to you is ASME Section IX, and it only outlines what is the minimum that must be met with respect to requirements, so the Client can request additional requirements that must be met beyon what the code allows or doesn't deem necessary...

So what I'm trying to explain to you is no matter what is written in ASME Section IX, or any other code/standard you are working from, if the client has specifically requested a procedure to be performed regardless if the code stipulates that it is not required for you to do so, then you must satisfy the requirements of your client based on what was already previously agreed to in the contract - UNDERSTAND Nalla??? In other words, the client can demand work beyond what is the minimum specified in the code even if the code does not require it as long as it is agreed upon and written as such in the contract documents regardless if the code doesn't require it! ;)

Now, if this PWHT was NOT part of the original contract documents, and was NOT listed as a required procedure to be performed in a specific manner by the client and written into the welding procedure at all and the client cannot produce any proof that is was in the original contract documents, then you were NOT required to perform PWHT on the piping, but according to the one document which you did attach to a previous post, it sure looks like you were required to perform the PWHT in the first place unless you can prove otherwise and that would be something you and your client would have to settle between both parties!

I hope you can understand what I am trying to say to you, because I do not wish to belittle you or mistreat you in any way Nalla. ;)

Parent - By Nanjing Date 12-29-2009 11:24
Are you sure the material you are welding is A106? I would have thought it should be a333 Gr6 for blow-down conditions on process gas.
- - By sreedhar Date 02-02-2018 12:17
dear friends,
i have 45mm thickness pipe of SA 335- grade P92
As per ASME B31.1 the temperature for PWHT is 730-775 degrees C
the time given was 1hr per 25mm, by this i got time for PWHT was 1hr48min
is there any possibility to complete the PWHT before 1hr48min by increasing temperature, there should be no change in mechanical properties and microstructure,

if any option, suggest the time and temperature to complete
Parent - - By Jeff feng Date 04-03-2019 04:01
you can't. you should consider the upper transformation temperature
Parent - By Jim Hughes (***) Date 05-08-2019 11:35
There is a lot to consider. B31.1 Table 132 Note 7.

(7) The Ni+Mn content of the filler metal shall not exceed 1.2% unless specified by the designer, in which case the maximum temperature
to be reached during PWHT shall be the A1 (lower transformation or lower critical temperature) of the filler metal, as determined by
analysis and calculation or by test, but not exceeding 1,470°F (800°C). If the 1,470°F (800°C) was not exceeded but the A1 of the filler
metal was exceeded or if the composition of the filler metal is unknown, the weld must be removed and replaced. It shall then be
rewelded with compliant filler metal and subjected to a compliant PWHT. If the 1,470°F (800°C) limit was exceeded, the weld and the
entire area affected by the PWHT will be removed and, if reused, shall be renormalized and tempered prior to reinstallation.
Up Topic Welding Industry / ASME Codes / ASME-B31.3-REPEATED PWHT-IS IT ACCEPTABLE?

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