If there is a through-thickness pinhole, and your welding process is GTAW, the pinhole is most likely not caused by a lack of shielding gas or contamination. This type of pinhole on a groove weld is caused by the arc is being removed suddenly from the molten pool, resulting in a heat shrinkage pinhole.
This can be corrected by:
1. The welder gradually reducing the amperage as he terminates the arc (throttling down with his thumb throttle on the GTAW torch handle).
2. Travelling forward with the arc after he ties in to close the root bringing the molten puddle on top of solid metal.
When this defect occurs, with hydrotest failure, it usually indicates that the weld was performed with only one pass. Some Specifications require that pressure retaining welds be performed by no fewer than 2 passes. Investigate the welder's work practice.
Darcy Morin
Bantrel Management Services
o - 780 979 6225
c - 780 782 5692
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Dick Overkleeft
Sent: December 27, 2011 1:10 PM
To: materials-welding@googlegroups.com
Subject: Re: [MW:13339] Hydro testing failure
Dear Mr. Shankar,
The porosity can be caused, by the following causes;
1) dirty or not clean piping or filler rod
2) unsufficient gasprotection from the torch
3) unsufficient backing gas
other causes may be excluded.
best regards,
Dick Overkleeft
2011/12/27 Dinesh Ravi Shankar <dinesh_ravi2001@yahoo.com>
Thank you jesti.I already verified PMI reports,but it is 2" line so we cannot check pmi under root pass.& may be after 2/3 days RT taken after welding.yes thru PT one round indication found on capping...after some grinding also its going like pin hole. thats y i m asking that in GTAW process,how pin holes will occur..? we have to avoid such a things during welding.Thank you & Best Regards,
S. Dinesh Ravi Shankar.
Mechanical Inspector,
Saudi Aramco Project Inspection Division (SAPID),
Manifa Core Hydrocarbon Facilities Project.Kingdom of Saudi Arabia.,Mobile : +966 562944695,
Tel : +966 3 379 2018.
From: jesti fer <jesti_fer@yahoo.com>
To: "materials-welding@googlegroups.com" <materials-welding@googlegroups.com>
Sent: Tuesday, December 27, 2011 8:05 AM
Subject: Re: [MW:13320] Hydro testing failure
--Dear Mr. Shankar,Is it possible to check the PMI in root weld, (the welder may use CS filler wire for root pass) and what is the time duration between completion welding and RT. You are getting any indication in PT?Best regardsK>M>HFrom: Muhammad Ashraf <mohdashrafr@gmail.com>
To: materials-welding@googlegroups.com
Sent: Monday, December 26, 2011 1:35 PM
Subject: Re: [MW:13313] Hydro testing failure
IT MIGHT BE DUE TO (Microbiologically Influenced Corrosion) MIC. LET ME KNOW IF YOU HAVE CARRIED OUT FLUSHING AFTER HYDROTEST AS RESIDUAL WATER, AT LOW POINTS IN THE 300 SERIES PIPING, LEADS TO SUCH FAILURES.RANAOn Mon, Dec 26, 2011 at 8:57 AM, Dinesh Ravi Shankar <dinesh_ravi2001@yahoo.com> wrote:
Thank you Mr.Karanth for excellent information.Anyway as per catagory we cannot cover 100% RT,but we have to avoid such a things during welding.In GTAW process,how pin holes will occur..?Dinesh.From: shankar narayan karanth <karanthequipments@gmail.com>
To: materials-welding@googlegroups.com
Sent: Sunday, December 25, 2011 4:57 PM
Subject: Re: [MW:13308] Hydro testing failure
Dear Shankar,
It looks that there are pin holes which you might have considered them to be rounded indication with in the limits of acceptance while Radiography interpretation.When optical density of rounded indication is quite high, you have to suspect them to be pin holes and had you carried PT on them it is quite likely that you have detected the defects.It is quite likely that very small rounded indications may not get picked up while carrying out MT. Hope this has answered your query.
P.S.Karanth
98251 29987
On Sun, Dec 25, 2011 at 5:41 PM, Dick Overkleeft <dick.overkleeft@gmail.com> wrote:
Dear Mr. Shankar,Could you please sent some more information?Can you inform us what kind of stainless steel you applied.What welding process you used, and which filler material.Is it plate or tube welding.What kind of water ( is there any chlorid in the water) did you use for hydrotesting and did you air test before hydrotesting.What kind of defects did you see on the X-ray?After this we might be able to give an answer on your question.bets regards,Dick Overkleeft EWEBureau Veritas2011/12/24 Dinesh Ravi Shankar <dinesh_ravi2001@yahoo.com>
--Dear friends,During hydro testing of stainless steel, recently 2 tests leak occurred at welded joint area. I verified RT films, PMI reports...etc.Just I want to find root cause.Please advise me that what proactive surveillance need to take of further hydro test failure & how it is happening..?Thank you & Best Regards,
S. Dinesh Ravi Shankar.
Mechanical Inspector,
Saudi Aramco Project Inspection Division (SAPID),
Manifa Core Hydrocarbon Facilities Project.Kingdom of Saudi Arabia.,Mobile : +966 568059765,
Tel : +966 3 379 2018.
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