Re: [MW:11231] pittings on surface of Shell

Hi,

Often engineers conclude that having provided a corrosion allowance has solved many problems associated with corrosion, unfortunately CA does not account for any of the localized corrision.

One pit in a large system can be enough to produce the catastrophic failure of that system, though measured depth is within corrosion allowance but if this is new fabricated, any pitting shall be subject to rejection.

Actions:- Identify the casue of Pitting and steps to avoid its occurence again, Pitting is something which once start can thin down thickness below required (Required thickness- Pressure containment + CA)

Regards
Manpreet Singh



On Tue, 31 May 2011 12:40:40 +0530 U WYNN-NAING <u.wynn-naing@total.com> wrote
>

As this vessel is low pressure water service, you could dobuttering onto the shell pitting areas by using qualified WPS & welder.

Make smooth grinding and MPI before buttering and do MPI afterbuttering.

(Of course, ASME SEC VIII DIV1 requirement to be checked and derogateas required)

Rgds,

WN

From:materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] OnBehalf Of Ahmed Eissa
>Sent: Saturday, May 28, 2011 10:36 PM
>To: materials-welding@googlegroups.com
>Subject: Re: [MW:11177] pittings on surface of Shell

please refer to API 510 (corrosion and minimum thickness evaluation) clause , since you have corrosion allawance 3mm, thus you do not to fear, but we have smillar case in our plant so we applied internal coat (joutn marthon) as this coat is hard and applied to splash zone in offshore rig, and we inspect it after one year the condition of paint was excellent and no pitting was observed , you have to think in internal coating to stop pitting from proceeding. > > --- On Sat, 5/28/11, asad azmi <azmiasadayub@gmail.com> wrote: > From: asad azmi <azmiasadayub@gmail.com> > Subject: Re: [MW:11173] pittings on surface of Shell > To: materials-welding@googlegroups.com > Date: Saturday, May 28, 2011, 5:44 AM vessel is newly consturcted. there is no problem regarding thickness. corrosion allowance is 3 mm. Regards On Sat, May 28, 2011 at 7:36 AM, Suresh <bobsuresh24@gmail.com> wrote: Hii, You should mentioned below info requirement prior to take any decision . 1. How long period in service . 2.What is previous Corrosion allowance as Inspection was carried out . 3.you should mentioned in what area to be taken under serious consideration and how much depth in major areas. Thank you Suresh On Fri, May 27, 2011 at 12:44 PM, asad azmi <azmiasadayub@gmail.com> wrote: Dear All, Greetings. Pittings (not more than 0.5 mm in depth) observed on the surface of a shell of a Vessel. pls find photos for your reference. Shell material is SA 36. thickness 8mm. service fluid - water Code of construction is ASME SEC VIII DIV1 After grindings also pittings can be observed on the large surface of the shell. Whether these pittings can be accepted as it is OR further grinding is required. Please Suggest. Thanks and Regards Asad Azmi -- To post to this group, send email to materials-welding@googlegroups.com > To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com > For more options, visit this group's bolg at http://materials-welding.blogspot.com/ > The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents. > > -- > Thanks & Best Regards, > > Suresh > > Mobile No: 91-92 92 905 905 -- > To post to this group, send email to materials-welding@googlegroups.com > To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com > For more options, visit this group's bolg at http://materials-welding.blogspot.com/ > The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents. -- > To post to this group, send email to materials-welding@googlegroups.com > To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com > For more options, visit this group's bolg at http://materials-welding.blogspot.com/ > The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.

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