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Discussion Forums - The Hendrix Group
HomeHomeDiscussionsDiscussionsGeneral Corrosi...General Corrosi...cracking in weldscracking in welds
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10/20/2008 9:00 AM
 
Is there aproblem of developing cracking if old ASTM 106 Gr B pipes are welded to low alloy steel elbow A234 WP-22 and operate at 170 deg C in a preheater of kerosene recovery unit
 
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10/20/2008 9:00 AM
 
Maushumi No problem to weld old A 106 Gr B pipe with new A 234 WP 22 flange Take caution to: 1. Edge prepare to suit the thickness of pipe and weld neck flange 2. pre heat job both at c.s and low alloy steel ends 3. weld using alloy steel electrode matching p 22 composition 4. MPT of root run to ensure no minor surface fissures in root run after proper wrapping after root run welding 5. Post weld heat treat at 720 deg cent the weld joint 6. Take hardness after S.R Hardness should be < 220 BHN. 7. Finally take RT and MPT of the heat treated weld joint Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India Oct 21, 2008 E-mail: nishi@vsnl.com >Is there aproblem of developing cracking if old ASTM 106 Gr >B pipes are welded to low alloy steel elbow A234 WP-22 and >operate at 170 deg C in a preheater of kerosene recovery >unit
 
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10/21/2008 9:00 AM
 
Thankyou Mr. Srinivas. I was apprehensive because one welding expert from L&T suggested that such weld may give rise to cracking. Hope to interact in future. Maushumi
 
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10/22/2008 9:00 AM
 
In general the heater designer will not mix the metallurgy inside the process heater mainly due to difference in thermal expansion for dissimilar material.May be in cold service it may not give problem.I am afraid if such dissimilar combination are there inside the furnace there is a possibility of cracking during running condition due to differential thermal expansion. It is better to use similar metallurgy inside the process furnace to avoid craks/weld failure. with regards,
 
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10/22/2008 9:00 AM
 
Maushumi Heater design of the same metallurgy is preferable - no doubt. Heater design with different metallurgy exist in some plants and work well if enough care is taken from beginning. Thermal expansion problem may be more with two dissimilar combinations than with same combinations ( i.e.,ferritic to ferritic combinations may not give thermal expansion problems seriously). With an existing old A 106 B pipe and weld necessity to use P 22 flange, with precaution in welding and post weld HT- as outlined in my first posting - may not give any problem for successful use. Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India Oct 23, 2008 E-mail: nishi@vsnl.com >In general the heater designer will not mix the metallurgy >inside the process heater mainly due to difference in >thermal expansion for dissimilar material.May be in cold >service it may not give problem.I am afraid if such >dissimilar combination are there inside the furnace there is >a possibility of cracking during running condition due to >differential thermal expansion. It is better to use similar >metallurgy inside the process furnace to avoid craks/weld >failure. > >with regards,
 
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