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HomeHomeDiscussionsDiscussionsOil Refinery Co...Oil Refinery Co...Use of Nickel alloy filler for welding in VGO serviceUse of Nickel alloy filler for welding in VGO service
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4/9/2004 9:00 AM
 
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Dear Sir, We need to cut and reweld a interconnecting nozzle joint of Feed/Effl exchanger in Hydrocraker unit. As per original procedure, E347 filler was used for root & Inconel-182 for remaining welding. P22 nozzles are internally overlayed with E347 to resist high temperature sulfidation and root lip of SS347 was made for site welding with E347 to match that. After cutting the joint, I attempted to restore lip using E347 filler, but failed as it was cracking badly. The suspected reason was nickel pick up by molten metal from old Inconel weld leading to brittle austenitic crack. Removal of whole inconel weld metal is going to take lot of time and may require additional stress releiving etc. Operating condition of exchanger is: Max. Operating temp- 350 -360 deg.C Max. Opearting pressure- 165 kg/cm2 Service- VGO with 2.5wt% 'S' (total) reportedly, reducing sulfur atmosphere is expected in the service. Questions: 1. Can I use Inconel 625 filler for welding of full joint without use of E347. 2. API RP 582 recommends use of inconel 625 in sulfur atmosphere upto 590 deg.C. But other guidliness not recommends due to sulfidation problem of nickel alloys at high temp. Please share your experiance. MParasuraman Dy. Manager (Inspection)
 
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4/10/2004 9:00 AM
 
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Nickel Alloy filler wire and your cracking problem in VGO Service. Nickel bearing filler wire may not serve any useful purpose under reducing conditons and with sulfidic environment. The welds will develop cracking after some time. Reason why a P 22 with S.S 347 filler wire matched weld cracked even with Inconel filler wire for top run may not be due to molten Nickel flow. This could be due to Sulphide Stress cracking (Tyope 1 or Type 2) - at 350-370 deg centigrade at this hgh pressure (165 Kg/Sq.cm) in VGO Service. Most probablay the problem could be due to SSC Type 2 cracks which will be difficult to repair weld except with care in welding. If multiple stress cracks were noted, you may have no other choice other than to repair till crack removal is done at the nozzle P22 to S.S weld joints including the over-lay welds. PWHT will be necessary for P22 to S.S joint and also to reduce the stresses after welding to bring down below the threshold stress for SSC Type 1 or SSC Type w cracking at this temp. Trust this is of help to your problem. C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai 600020 India April 11, 2004 e-mail: nishi@vsnl.com
 
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HomeHomeDiscussionsDiscussionsOil Refinery Co...Oil Refinery Co...Use of Nickel alloy filler for welding in VGO serviceUse of Nickel alloy filler for welding in VGO service


  

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