Sharjee If you are likely to operate at -29 deg C, then SA 516 Gr 70 should be impact tested < - 29 deg C and not at just - 29 deg C. SA 36 is a general structural quality steel - with some Cu additions (mainly from atmospheric corrosion resistance for structural use). You will not be adequately compenstaed even if it is killed steel so far your use for low temperature use at - 29 deg C. I would suggest you to think of a low temperatture tested structural or pressure vessel steel material even for structural use if you continuously see < -29 deg C even for structural components attached to pressure vessel components. A 193 B 7 can be used at your service temperature i.e., for low temperature use at -29 deg C. Impact test requirement should be specified - as agreed between you and the supplier - at the time of ordering as a supplementary requirement for impact tests. Better still if your bolts are to see continuously < -29 deg C- you consider A 320 L 7 /L 7B where impact test to your requirement is mandatory to be done. Hope this helps you C.V.Srinivasan Nishi Engnieers Pvt Ltd India Feb 17, 2008 E-mail : nishi@vsnl.com >Hello, > >We are designing a vessel whose operating temp. is 20 deg C >and pr. is 5 barg. But the ambient temp. is -5 deg C hence >the MDMT is chosen as -29 deg C. The pressure parts will be >made from SA 516 Gr. 70 impact tested at - 29 deg C which >should absorb 27 J. > >For the structural members connected to the vessel which >will experience -29 deg C, the designer has chosen SA 36. > >According to me, if used below 0 deg C, SA 36 should be >fine grained fully killed. Fine grained structure would >promote notch toughness while killed steels have a higher >yield point. Also the designer should specify impact testing >at -29 deg C. > >For the fasteners connected to the structural members, the >designer has chosen SA 307 Gr. B. I think bolts which are >experiencing - 29 deg C should be SA 193 Gr. L7 and impact >tested. > >Please comment and clarify. > >Thank you very much in advance. > >Good day. > >Sharjeel