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HomeHomeDiscussionsDiscussionsGeneral Corrosi...General Corrosi...Approach on weld inspectionApproach on weld inspection
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5/30/2010 10:00 AM
 
What I have wrote is based on the practical implications involved in conducting NDT after PWHT especially when construction projects are underway. The same I have witnessed in construction phase / construction specifications of large projects. P11 and P22 generally do not come up with cracks if your welding controls are OK but agree with you that no welding is 100% perfect always. In high Cr alloys P5 & P9 crack initiation / susceptibility is higher and UT controls are always specified after PWHT. I have conducted UT on more than 50 weld joints in P11 & P22 recently and did not find any crack. This may be due to good controls of PWHT operation. I respect your comments however what I would conclude is that UT after PWHT on P11 & P22 is good to do but may overkill the cause and can delay construction activities. Regards, Ashfaq Anwer http://thepetrostreet.com >I dont agree with Ashfaq, >P11 and P22 needs critical control pre, during and post >welding. These material depending upon J and X factor are >susceptible to delayed hydrogen cracking and temper >embrittlement. >This careful NDT control is required. RT is suggested >minimum 72 hrs after welding. >In normal practice no welding team is 100% full proof and >thats why careful NDT is desired. UT is often dictated by >QC Inspectors and Consultants as an ultimate NDT after PWHT >as UT can detect finer cracks which can generate in P11 and >P22 material due to material chemistry, impurities and lack >of control in welding / PWHT. > >Thus it is better to keep 100% RT followed by UT as best >engineering practise but depending on service criticality >and cost of failure impact on Plant and Management this need >to be decided by the Inspection and Planning team. > >regards > >>1. It is advisable to have 100% RT on all weld joints in P11 >>or P22 material whatever the weld joint thickness and type >>is. It may be waived off on socket welds having throat >>thickness below 8 mm provided they have not to be operated >>in hydrogen service. >>2. What we have experienced is that UT after PWHT on P11 or >>P22 does not yield any finding. You just need to monitor >>PWHT in the right way. But yes on P5 and P9 having higher >>chromium content, this should be the practice to conduct >>100% UT after PWHT as probability of crack initiation during >>PWHT is higher due to higher Cr content. >> >>Hope this would help. >> >>Regards, >>Ashfaq Anwer >>http://forums.thepetrostreet.com
 
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5/30/2010 10:00 AM
 
Bigpond Your question on P 11 & P 22 PWHT - RT related questions had raised different views / different practising standards to be followed or expressed by Ashfaq & Debasis. Ashfaq seems to have some practical experience with Debasis talking on theoretical approaches while expressing each one's individual views. Delayed hydrogen and temper embrittlement cracks do not come in < 30,000 hr service hours in hydrogen related services at higher temperature operation. Every plant designer / operator should know this. For any major engineering designer / operating company / top engineering consultant of major plants would easily recognize this as a possibility after 30000 hours, it is worth spending both from 100% RT and 100% UT after PWHT for P 11 or P 22 materials in high temperature hydrogen service. Specification for this should incorporate this additional incorporating built-in testing or inspection from future safety. The delays in construction activities or plant completion should be given a back ground related effect while considering the damages or destruction a hydrogen related fire (from delayed hydrogen related cracks combined with temper embrittlement failures), Plants which had experienced such failures and devastation would vouch for the same. I have had occasions to review both from failure investigation and from bringing back to plant operations on such failures experienced by different plant operators ( failures related to P 11 or P 22 piping in operating plants in hydrogen service and the huge material and production loss each plant had suffered). If it is a heat exchanger using such improperly thought out or left out initial scanning using RT/UTF techniques at the construction stages or manufacturing stages due to over sight or complacence, many plants had repeated problems and sometimes frequent loss in plant capacities. Lessons learnt from such experience should form the background for future care when using such materials than discussing the merits of one technique or a combination of techniques when evaluating the over all damage such omissions could cause. I am sure this forum would take all aspects into account while suggesting or discussing the merits and de-merits of each technique to be used for evaluation from project engineering or project completion. Ultimate aim is to have less pin pricks for a plant operator whether it occurs after 1000 hrs or after 30000-50000 hours due to omissions at the design and plant implementation stages. Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India May 31, 2010 E-mail: nishi@vsnl.com >Bigpond > >P 11 & P 22 alloy steel welds should be 100% RT only to meet >code practices. WPS / PQR should also specify only 100% RT. > >Some project engineering specifications and purchase orders, >using P 11 or P 22, do specify second RT / UT Flaw >detection after heat treatment just to ensure that during >heat treatment any undue stresses from forming or welding in >HAZ or parent plate does not show up as sub-surface cracks >or any surface or sub surface cracks had not developed after >heat treatment. > >If you experience hard zones after H.T and you propose to >use this P 11 or P 22 material in high temperature hydrogen >or syn gas services, second RT and UTF would certainly help. > >If it is meant for hydrogen or syn. gas service at high >temperature, it is worth doing second RT (100% and not any >random 25%) and again 100% UT Flaw check of the welds > >Hope this helps >C.V.Srinivasan Nishi Engineers Pvt Ltd India August 4, 2009 >E-mail : nishi@vsnl.com > >>Hi, I have a query regarding inspection approach different >>consultants follow in terms of alloy steel pipe welds mainly >>P11 and P22 pipes. We have come across a spec where it >>insists 100% radiography all the weld joints for all alloy >>steel joints. We have also worked in similar projects where >>alloy steel piping with same criticality had only 25% >>radiography if it follows the same WPS and carried out by >>same welders. Is it wise to have 100% RT for alloy steel? >>And also, it is worth having second RT or UTI after heat >>treatment on such joints? >>regards
 
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