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
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Ryan Carbonara
Sent: Monday, September 24, 2012 11:21 AM
To: materials-welding@googlegroups.com
Subject: RE: [MW:15381] Re: Socket weld gap requirement
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
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of John Henning
Sent: Monday, September 24, 2012 9:51 AM
To: materials-welding@googlegroups.com
Subject: RE: [MW:15380] Re: Socket weld gap requirement
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: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Pradeep kumar hormis
Sent: Monday, September 24, 2012 3:14 AM
To: materials-welding@googlegroups.com
Subject: Re: [MW:15378] Re: Socket weld gap requirement
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.
On Sun, Sep 23, 2012 at 7:20 PM, Hernan Arturo Castillo Mier <Hernan.Castillo@ecopetrol.com.co> wrote:
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.
Enviado desde mi iPhone
El 23/09/2012, a las 10:28 a.m., "ranendrac6@gmail.com" <ranendrac6@gmail.com> escribió:
> 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
>
> -----Original Message-----
> From: Raghuram Bathula <raghurambathula@gmail.com>
> Sender: materials-welding@googlegroups.com
> Date: Sun, 23 Sep 2012 08:10:03
> To: Materials & Welding<materials-welding@googlegroups.com>
> Reply-To: materials-welding@googlegroups.com
> Subject: [MW:15368] Re: Socket weld gap requirement
>
> 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.
>
> On Sep 22, 7:49 pm, Naresh Kumar <snareshkuma...@yahoo.com> 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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Thanks & Regards
PRADEEPKUMAR HORMIS
QC WELDING INSPECTOR
ARAMCO PROJECT(JEDDAH REFINERY)
Mob:+966 - 59 11 36 36 9
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