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Discussion Forums - The Hendrix Group
HomeHomeDiscussionsDiscussionsGeneral Corrosi...General Corrosi...Stress corrosion on LTCSStress corrosion on LTCS
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2/16/2009 9:00 AM
 
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Hi, I have a query regarding possible stress corrosion of low temp carbon steel with liquid ammonia. some of the weld specs stongly recommend PWHT to control hardness while some do not. i would like to know 1. how critical is SCC on LTCS with liquid ammonia (in presence of min 1% water) 2. How important is hardness that any repair on ammonia storage tank and pipework shall require PWHT regards regards
 
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2/17/2009 9:00 AM
 
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Bigpond In presence of water ( water =0.5% or above) SCC trend is inhibited in liquid ammonia service. For LT carbon steel - if hardness as welded or in HAZ or in parent plate or pipe exceeds 210 BHN ( approx: 21 HRc) it is advisable to carry PWHT to limit the trend of SCC in ammonia service. For tanks > 20 mm wall thickness, if repair welded hardness is > 210 BHN (approx: 21 HRc) then depending on hardness and code regulations PWHT may be needed. Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India Feb 17, 2009 E-mail: nishi@vsnl.com >Hi, >I have a query regarding possible stress corrosion of low >temp carbon steel with liquid ammonia. some of the weld >specs stongly recommend PWHT to control hardness while some >do not. i would like to know >1. how critical is SCC on LTCS with liquid ammonia (in >presence of min 1% water) >2. How important is hardness that any repair on ammonia >storage tank and pipework shall require PWHT > >regards >regards
 
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