Dear Members, I would firts like to convey my sincere regards to every one who shares their valuable information on this dicussion forum. I am a new member to forum and found this forum very informative and interactive. Please find below the post which I have initiated. We have observed Hydrogen blistering on our Crude Overhead accumulator. As a corrective measure we have planned to internally linned the Cs vessel with monel - 400 and as requirement we have specified the folowing requirements. 1. Explosion bonding 2. Cross section microstructure of the bonding to confirm complete bonding. MR-175-2002 was also referred for the hardness requirement but their is no hardness requirement for the monel-2002 where as for some other Nickel-copper alloys the hardness mentioned as 35 HRC. Till date we have not observed any cracking on any of the monel cladded vessels, but cracking seems to be quite common phenomenon observed. Please share your views regarding the hardness requirements, if any of the monel-400 cladded material. Regards, Shabbar Corrosion Engineer

Thanks for the reply. In fact we dont have the copy of the latest edition of MR-175. From your reply it seems that MR-175-2003 is the latest edition which speaks about the Monel-400 Hardness. Regards, Shabbar

Shabbar I am not so sure if you intention planning of internally Monel lining your C.S crude overhead vessel is the good one. %B7 Instead you should replace your carbon steel vessel according ANSI/NACE Standard TM0284-2003 Item No. 21215 “Evaluation of Pipeline and Pressure Vessel Steels for Resistance to Hydrogen-Induced Cracking” and NACE TM0177 – “laboratory testing of metals for resistance to sulphide stress cracking in H2S environments”. You should note that: “Hydrogen induced damage describes any of a number of forms of degradation of metals caused by exposure to environments (liquid or gas) which cause absorption of hydrogen into the material to cause degradation in mechanical performance. Examples of hydrogen-induced damage are: Formation of internal cracks, blisters or voids in steels. Prevention or Remedial Action for internal cracking or blistering are: 1-use of steel with low levels of impurities (i.e. sulphur and phosphorus). 2-modify environment to reduce hydrogen charging. 3-use of surface coatings and effective inhibitors. Regards Luis Marques