Socket weld gap requirement

[Naresh Kumar]

Dear experts,

As per ASME 3.1.& 31.3 socket weld gap requirement is 1/16” before welding. Whether it is required for after welding, if its require kindly provide the code details.In our project we're done RT for socket welds. But after welding did not find the 1/16” gap, its less than 0.5mm. Our client decision is to cut and reweld the all joints.

 

 

Thanks & Regards,

Naresh

[Raghuram Bathula]

no it it not required after welding, many times gap closes to zero due
to shrinkage during welding. if your client requires the gap after
welding (I don't see any reason for this) probably you need fit up
with more gap.

[ranen...@gmail.com]

The gap is required to release the fume gases which generated during welding. No gap required after welding(I don't see any reason). You can check with 4 mm gap during fit up to meet client requirement.
Sent on my BlackBerry® from Vodafone

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[pgoswami]

Hi Naresh,

Please see the interpretation of ASME on requirements of gap for socket welds and the NDE following welding . The prime function of this gap is to facilitate the expansion and contraction of the thinner components in the  socket weld fit-up, especially the piping.

This gap is required during the fit-up , not after welding. In your case(as mentioned below) there should not be any violation of code approved practice.

Thanks.


Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario, Canada.
Email-p...@sympatico.ca,
pgos...@quickclic.net

Interpretation: 19-5- http://cstools.asme.org/csconnect/pdf/CommitteeFiles/23730.PDF

[Hernan Arturo Castillo Mier]

Your information is not true.
The gap its necessary for thermal expansion of tube been welded according to the operation temperature.
Its necessary to calculate the expansion expected according to the op temp.



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[Pradeep kumar hormis]

Dear All

I would like to introduce my self first. I am working as QC WELDING INSPECTOR for one of SAUDI ARAMCO project. we are using most of socket joints for plant piping . SAUDI ARAMCO  having special standards , procedures and check lists for all the cases. so here i attached one of the check list for socket joints fit ups. even it is a client specification , I hope you will get help for your clarification. please note the CLAUSE -C2  on the SAIC.

Thanks & Regards

PRADEEPKUMAR HORMIS
QC WELDING INSPECTOR
ARAMCO PROJECT(JEDDAH REFINERY)
Mob:+966 - 59 11 36 36 9

[Rajagopal Kannan]

Dear Pradeep,

What is 25mm marking method, mentioned in the attachment?

Thanks and Best regards,

K.Rajagopal

[John Henning]

The statement in Saudi Aramco Clause C2 is correct.

 

More often than not, the gap will “disappear” after welding.  The common misconception is that you must have the gap after welding.  The purpose of the gap is to permit shrinkage of the weld without creating additional mechanical stresses on the finished joint.  Obviously, in weldor parlance, if the joint “sucks in” the gap will close.

 

Note that at one time, the EPRI NDE center was doing some investigation into the necessity of gaping socket joints.  The opinion at that time was that the gap was unnecessary and that this “rule of thumb” was a nearly universal myth.  If memory serves me correctly, the recommendation was that a more important modification for socket joints was to make the length of the horizontal leg of the weld twice the length of the vertical leg.  This type modification was reportedly very effective especially in minimizing fatigue cracking.  I wouldn’t mind knowing if this has been investigated further or if there was any additional information published on this.

 

John A. Henning

Welding & Materials

 

From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of Pradeep kumar hormis

Sent: Monday, September 24, 2012 3:14 AM
To: material...@googlegroups.com

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[Ryan Carbonara]

Guys,

    Exxon Mobil spec. states RT 10% of all socket welds on branch connections for complete fusion and gap.

 

When the welding is done you have to be able to slide a piece of paper or sharpened paper clip in the gap. If it’s bottomed out, it is a cut out.

 

A tacked socket joint should pull the full 1/16” during welding

 

Accept this comment as you like, but you need to confirm gap in most real world instances these days.

 

ONLY POSITIVE GAP. We’ve used small horoscopes with magnification and literally have shown the ExxonMobil (XOM) inspectors .005” gap to alleviate cut out.

 

If it is bottomed out it is identified as indeterminate whether gap was present in the joint prior to welding.

 

Ryan Carbonara

Welding / QA   

 

---

[John Henning]

The last line is the operative one, XOM is using the remnant of a gap as evidence that the gap existed prior to welding -  this not a Code requirement, just XOM over exuberance.  Most know, after reviewing XOM specifications, that you will have to gap an extra amount so that some gap still remains after welding.  My experience in the power generation, it is typical practice to scribe a line at full insertion, pull the pipe back the 1/16”, then tack.  Unfortunately, the scribe mark usually gets welded over so there is no proof that the joint was gapped if it sucks up tight.   It would require the owner-inspector to at least randomly inspect fit-ups to verify correct practice is being followed. 

 

One thing that should bother everyone is that some socket fittings are now being bored with drill rather than an end mill leaving a tapered bottom – guess that will confuse things a bit.

 

A secondary cure to the inspection issue is to use “gap-o-lets”.  The presence of the “gap-o-let” on the RT is then proof positive that the joint was gapped properly.  There is of course the cost of stuffing a “gap-o-let” into each joint but there is no p&m about whether a joint was gapped or not.

 

John A. Henning

Welding & Materials

 

[Pradeep kumar hormis]

Sir
 
    I would like to know  , any criteria for maintaining the GAP between ID of female part and OD of pipe or male part especially in SOCKET joints.. Any standards or specification given details of it?. There was an issue between client inspector and contractor.

[Naresh Kumar]

Dear experts,

Thanks for every comments and suggestions.  Our client point of view, pipe shall be expanded during operation.

Material: A312 TP316L

Size:1 ½”,1” Sch40

Design temp.:96 C

Operating temp.:68 C

 

Thanks & Regards,

Naresh

---

From: Naresh Kumar <snaresh...@yahoo.com>
To: "material...@googlegroups.com" <material...@googlegroups.com>
Sent: Saturday, September 22, 2012 8:21 PM
Subject: Socket weld gap requirement

[John Henning]

All of the following require a 1/16 inch minimum gap prior to welding for socket type joints:  ASME I, ASME VIII, ASME B31.1, ASME B31.3.  None of these Codes address the condition after welding.  My familiarity with the Code would indicate that this is intentional as it is generally recognized that the joint often will close completely after welding.

 

Customer’s can demand anything, whether rational or not.  In many cases the customer will assume if there is no gap after welding the socket weld was not properly gapped prior to welding (where were their inspectors during fit-up?) .   Physics be damned.  No amount of scratch marking etc. will convince these customers.  The only way is to gap to greater extent or through the use of gap-o-lets^Ò.

 

Bottom line:  read your customer specifications carefully before you begin fabrication. 

[Desai Jignesh (Mumbai - Piping)]

Below interpretation of B 31.3 and Shell  std. Extract are quite convincing for subject matter.

 

1.      B 31.3 Interpretation

 

 

 

2.      As per SHELL Spec DEP 31.38.01.11 Gen. Aug 2005

 

Socket-welded connections cannot be properly radiographed to verify weld quality; they can only be inspected by surface techniques such as magnetic particle or liquid penetrant. Radiography may be selectively applied to check that a fit-up gap remains after the weld has been made.

 

Regds/Jignesh

 

From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of John Henning

Sent: 25 September 2012 19:07
To: material...@googlegroups.com

[Pradeep kumar hormis]

Si
I had a query related to same subject. one of our client is asking 2 cases in same socket weld joint configuration. at the time of fit up we need th make sure those things. the main points are follows,,same time i attached a sketch from ASME B 31.3- 328-5-2A WITH MARKED.

1. GAP BETWEEN INNER DIAMETER OF SOCKET AND OUTER DIAMETER OF PIPE.

2. PENETRATION AT THE ROOT .

is this mentioned  in Any International standards or Company specification. ? if that just share to me ..

[Murugesan Jeyaraman]

Hi Naresh 

As per code 1/16" gap for socket welding is before welding. There is no mention in code about gap after welding. Even  the code committee have discussed  on the issue. But, still ASME code committee have decided to mention the gap before welding and do not want to address the gap requirement after welding is completed.  

I have handled many projects in my experience and almost most of the Client specifications call for maintenance of gap after welding. 

I have had many arguments with Client inspectors and they always want see the gap in RT films.  But, even though client inspectors understand the explanation, no body wants to accept socket welds without the minimum gap 1.5mm, because it has been either specification requirement or followed up everywhere like a tradition. 

Client specifications have been written keeping in view of possible thermal expansion of pipelines during process, which in turn may induce stress and crack if there is no Socket weld gap after welding. 

Technically, this also seems to be correct. But, it seems no research or study has been done to prove this. 

You have no other option but to accept the clients advise. 

Some client inspectors accept if the gap is atleast 1mm instead of 1.5mm. 

It is only client's call with reference to their specification. 

Thanks 

Murugesan

On Wed, Dec 19, 2012 at 12:24 PM, Materials & Welding <material...@googlegroups.com> wrote:

Interpretation 20-01 attached

--

[John Henning]

This has been discussed previously.  But here is my knowledge of the requirement.   Every ASME Code (e.g. ASME I, VIII, B31.1, etc.) requires that a socket weld have a 1/16 inch gap between the bottom of the socket and the end of the inserted tube/pipe before welding.  This gap is to provide some cushion to allow weld shrinkage without inducing significant residual stress. It is not the intention of any of these Codes to have a 1/16 inch gap present after welding.  It is a misinterpretation of the Code(s) to require the gap to be present after welding as the gap before welding would have to be much greater than 1/16 inch. 

 

There are a whole lot of people out there, including some major petro-chems that seem to ignore the Code specific wording; i.e. “before welding”. 

 

My own opinion is that there is no viable way for an inspector looking at the joint after welding to assure that the socket weld was gapped properly before welding.  So, rather than the customer having their inspectors doing any real work on the job impose the spurious requirement that a 1/16 inch  be present after welding.  As Grace Slick said “when logic and proportion have fallen sloppy dead” . . .    

 

The only way I know around this is to use products akin to Gap-O-Lets . . . but that is an additional cost and really unnecessary.

 

Bottom line :  if you are finding any open gap after welding, you have obviously achieved what was intended in the Code requirement; minimizing/eliminating residual stress resulting from the bottoming out of the socket joint due to weld shrinkage.  Your Client should go pound sand.

 

John A. Henning

Welding & Materials

 

From: material...@googlegroups.com [mailto:material...@googlegroups.com]
Sent: Tuesday, December 18, 2012 10:25 PM
To: material...@googlegroups.com
Subject: [MW:16259] Re: Socket weld gap requirement

 

Interpretation 20-01 attached

On Saturday, September 22, 2012 8:19:28 PM UTC+5:30, Nareshkumar Subramanian wrote:

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[M.P.N MUTHUKUMARAN]

Dear Naresh

         Socket Joint gap requirement of 1/16” before welding is basically required to accomodate the thermal expansion of pipe inside the scoket during welding, Which will avoid the stress created by rectriction.

 

         Check one sample joint with RT at fitup stage and the same joint after welding with RT following the same RT Technique.

Compare the all the values,I.e., Gap Physical dimension, Dimension in RT at Fit-up stage and Dimension in RT after welding.You can find out where It has went wrong.

 

                                                                             or

 

           Cross Cut one rejected joint and check the gap dimension- This will also give Idea on the RT technique to be used. 

 

Best Regards,
M.P.N.Muthukumaran

From: Murugesan Jeyaraman <jmuru...@gmail.com>
To: material...@googlegroups.com
Sent: Wednesday, 19 December 2012 8:46 AM
Subject: Re: [MW:16261] Re: Socket weld gap requirement

Hi Naresh 

As per code 1/16" gap for socket welding is before welding. There is no mention in code about gap after welding. Even  the code committee have discussed  on the issue. But, still ASME code committee have decided to mention the gap before welding and do not want to address the gap requirement after welding is completed.  

I have handled many projects in my experience and almost most of the Client specifications call for maintenance of gap after welding. 

I have had many arguments with Client inspectors and they always want see the gap in RT films.  But, even though client inspectors understand the explanation, no body wants to accept socket welds without the minimum gap 1.5mm, because it has been either specification requirement or followed up everywhere like a tradition. 

Client specifications have been written keeping in view of possible thermal expansion of pipelines during process, which in turn may induce stress and crack if there is no Socket weld gap after welding. 

Technically, this also seems to be correct. But, it seems no research or study has been done to prove this. 

You have no other option but to accept the clients advise. 

Some client inspectors accept if the gap is atleast 1mm instead of 1.5mm. 

It is only client's call with reference to their specification. 

Thanks 

Murugesan

On Wed, Dec 19, 2012 at 12:24 PM, Materials & Welding <material...@googlegroups.com> wrote:

Interpretation 20-01 attached

On Saturday, September 22, 2012 8:19:28 PM UTC+5:30, Nareshkumar Subramanian wrote:

Dear experts,

As per ASME 3.1.& 31.3 socket weld gap requirement is 1/16” before welding. Whether it is required for after welding, if its require kindly provide the code details.In our project we're done RT for socket welds. But after welding did not find the 1/16” gap, its less than 0.5mm. Our client decision is to cut and reweld the all joints.

 

 

Thanks & Regards,

Naresh

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[Khandaker Imamul Hasan]

Dear Experts,

Could any body share the maximum range of this gap, i mean, what should be the maximum gap be kept after welding?

FYI, Now we are accepting upto 4mm (evaluating by RT film ) but constructor are requesting to allow upto 5mm gap.

Code or RP will be highly appreciable.

--

Best Regards

Khandaker Imamul Hasan

Bureau Veritas (Bangladesh) Private Ltd.