Lock for sigma phase and sensitazation
From: rzoubi [rzoubi@just.edu.jo]
Sent: 20/12/2009 09:45 GMT
To: <materials-welding@googlegroups.com>
Subject: [MW:3854] Stress Corrosion Cracking in expansion joints
Dear Forum Members,
We have consructed a high temperature hot water disrict heating system early in the year 2000,the initial insallation of the system was not so good -there were some axial and lateral deflection in the system- .The expansion joints are made fromS.S304,after 3 to 4 years of operation ,we noticed cracks in the bellows ,starting from inside to outside the layers(9 layers).When refering this prblem to some experts in our country, they called it stress corrosion cracking related to chloride content in the sarrounding envr..W e asked an expert to ckeck the presence of chloride in the envr., he found no traces of this gas.As we have no budget to replace all the expansion joints in the future,we are obliged to replace the defected exp.joint when the joint starts to leak.In order to vercome this problem we are thinking to paint these joints with a high temp. resisiting paint up to 200degree c,as the max.operating temp. is 150degree.(the operating pressure is around 20 bar).
Plase advise whether this idea is right,if not please give us another solution.
Thank you in advance
ENG.RIYAD ALZOUBI
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