Paul A 351 Gr HK 40 is the same as SA 351 HK 40. HK 40 - a medium carbon Fe-Cr-Ni alloy - is used in heaters - as centrifugally cast tubes or static cast for heater coil support upto 900 -950 deg C. HK 40 material is intended for high temperature use - generally upto 900-950 deg C for use in medium pressure ( 5-40 Kg/sq.cm at 900-950 deg C) in reformer furnaces, methanol plant and pyrolysis furnaces in Fertilizer, Refinery and Petro-chemical plant with service life calculated to last for 100,000 hours. Hope this helps you C.V.Srinivasan Nishi Engineers Pvt Ltd India Feb 23, 2008 E-mail: nishi@vsnl.com >My question is: > >What is the difference between SA351 Gr HK40 and A351 Gr >HK40? > >If they are same material (alloy) , does it used in heaters? >What is the limiting temperature for this alloy? > >If the heater is under ASME Sec.VIII pressure vessel code, >can this materil used under this code? > >My information is we cannot use this material as a tube >support for a pressure vessel if the pressure vessel is >under the ASME SEC VIII code. If this is true, how come API >heaters used HK40 material as a support? > >I really need to understand the difference and >interpretation on this topic. > >Thank you very much for you all. > >Paul