BFW Preheater loated between HT shift and LT shift converter with Tube Sheet A 182 F 1 is OK. You are generating steam at 110 Kg/Sq.Cm2 (1500 PSI) in this exchanger. Hardness of Tubes of 192 BHN is OK. It is not too hard except that teh manufacturer should have done cold forming to get a little higher hardenss in the range 185-200 BHN. You may experience a different problem in the BFW Preheater with causic carry over may develop SCC (stress corrosion Cracking) if S.S. expansion bellow had been used in this exchanger. This problem will come after some years . Expansion bellows if made of S.S may develop cracks after some years. If you have used a double "U" or Omega type thin walled expansion bellows, the chances will be less or this may take more time to develop cracks. If "V" or Single "U" designed expansion bellow had been used then chances of cracks will be much sooner. Some bellow manufacturers supply Inconel. If that be the case chances of cracking will be much less. Trust this is of help to you. C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai 20 India June 06 >Our exchanger specs. are as follows: > >BFW preheater >Installed between High temperature shift converter and low >temp. shift converter >Tube side operating temp. = 143 / 193 deg. centigrades >Shell side operating temp. = 335 / 220 deg. centigrades >Tube side operating pressure = 115 Kg / sq cm >Shell side operating pressure = 29.8 kg / sq cm >Tube side service fluid = BFW >Shell side service fluid = Process Gas >Tube material = ASTM A 209 T1 >Shell material =ASTM A204 Gr. B >Tube sheet material = ASTM A 182 F1 > >Hardness monitored at U bends 192 HB. >Pl. comment.