I%60m an operator with a company using a process that generates steam with its process water. The steam exits the vaporization excangers at approximately 300-340F and 65-80PSIG. We use MEA to maintain pH control at 7.5 to 8.5. Our vaporization exchangers are exhibiting what I believe is amine induced corrosion/erosion at the vapor outlet of the tubes and the tubesheet. I haven%60t tried to calculate steam velocity through the tubes. Our process at this stage has been intimate with CO2 and H2S. Several yrs. ago, we quit stress relieving or "baking" our exchangers and I believe this could be a major contributor to the problem as the tubes are rolled into the sheet and I believe the stresses attendant with this action may be making the tubes and sheet susceptible to amine induced cracking that presents itself as what looks like erosion. Any suggestions? Thanks a bunch, Plain

Erosion - Corrosion - Tube to 'tube Sheet end - Vapor Outlet end Vaporaization Exchanger in Amine service 1. Possibility of higher temperature than design could result in more vapor generation at the vapor outlet end . Tubes might have been adequately designed for Steam service but with steam + carryover CO2 / H2S - if amine stripping is not proper at the Amine Absorber (CO2 Absorber tower) could result in erosion - corrosion. Tubes and tube sheet might not have been designed properly for higher vapor velocity at the exit. It might have been designed for liquid exit. Please check from this point. Measuring steam or vapor velocity would give enough indication + also the temperature measurement at the exit end of tube to tube sheet . Generally speaking, in MEA service with liquid entrainment and some vapor load - 3m/sec velocity would be OK. Please check if there is a possiiblity of higher velocity > 3 m/sec in MEA absorobtion tower with both liquid and vapor carry over in the process flow. 2. Second possibility exists if the tube -tube sheet had seen more erosion - corrosion - a preferential trend of erorsion -corrosino only at one end viz., preferential erosion only at the steam inlet nozzle at the shell side, then it could be relaated to higher temperature during start-up and shut down time when steam enters the shell side. 3. Did you observe only preferential erosion-corrosin signs in some tube to t ube sheet areas or throughout the tube sheet? 4. This need not be amine induced but could be more due to CO2 / H2S carry over if the CO2 absorber had not performed well or there is tray collapse at some portions of the CO@ tower. MEA Absorber towers wtih tray collapse will result in steam with CO2 /H2S carry over which can result in this type of problem. 5. If you had experienced erosion -corrosion + some SCC then it could be a problem of tight rolling and higher stresses in those tube to tube sheet rolled areas contributing to SCC problem also. Pleae examine from these possibilities also. Trust this answeres your querry. C.V.Srinivasan Tech Dir Nishi Engineers Pvt Ltd Chennai 20 India April 29, 2004