Over-lay welding on CO2 Absorber - Corroded portions with Potassium Carbonate as inhibitor Step 1: Remove all pits and corroded areas in the abosorber by metal grinding and make the surface as much near same as possible Step 2: Pre-heat the localized areas - corroded portions and ground out portions to 120-150 deg cent - if possible before weld over-lay. Step 3: If you can maintain pre-heat during welding this will vastly improve quality of repair welding during first /second and thrid runs For this provide, asbsestos cover suit for welders. Pull out each welder after 15-20 mintues of welding. Welder will get de-hydrated fast after first two days of welding in such massive repair welding of corroded portions of CO2 Absorber. Step 3: S.S. 310 or S.S 309 is OK. Inconel 82 is costly to do. If dilution of greater than 40% is expected during first run with 4 or 5 mm electrode , then use S.S 310- Mo or Cb/Ta stabilized grade ( S.S. 310 Mo / Cb/ Ta electrode)> Step 4: After first run covering the first weld layer - Dye penetrant inspect and grind where excess building done or areas which have not been properly welded. For this weld has to be cooled and pre-heat to be discontinued Step 5: Pre-heat and do the same for the second and third or if requried fourth cover runs of welding . From the second or thirid run you can choose to use even S.S. 308 L - Mo stabilized grades electorde. S.S. 309 L- Mo stabilized can also be used. Step 6: After each run, grinding to smooth finish and D.P. test is essential. Step 7: Finally a thorough grinding and smooth surface finish is essential so that the welded rough portions do not cause problems of corrosino after two years. Step 8> Final weld cover run to Dye Penetrant Inspected. Step 9: Use Infra-red heating element pads to stress relieve the weld over-lay portions with insulation lagging from outside so that heating dissipation is avoided as much as possible. Hold at 600-610 deg cent as much as 4-6 hours if you can attain this temp without dissipation of heat. If you cannot achieve this temp, heat to 500-550 deg cent and hold for atleast 7-9 horus ar that temp. Step 10> Release temp from S.R temp of 500-600 deg cetn at the rate of 100 deg cent per hour to come to lower than 250 deg cent. Step 11 : Remove insulation and allow air cooling to amibinet temp. Step 12. RE-inspect the entire weld over lay portions and grind locally where surface roughness is noted. Also take a Hardness profile to ensure that hardnesss is lower than 20 HRc ( 200 BHN). Step 13: Use local Poldi type Harness testers to record profile of hardness. Dye Check all welds once again before fizing trays and loading and boxing the Absorber. This will vastly improve your Absorber corrosion in future If you have any questions, please e-mail to nishi@vsnl.com C.V.Srinivasan Tech Director Nishi Engineers Pvt Ltd Chennai 20 India June 02, 2004 >At our plant we have a carbon-di-oxide absorber . CO2 is >being absorbed by K2CO3. It operates on 27 bar pressure and >120 Centigrades temperature. Presently we are experiencing >high corrosion of Carbon Steel . So we have planned weld >overlay on Carbon Steel. Can you please suggest me the >appropriate material for weld overlay in this service. Can >SS-309 or inconel 82 be used here. Please note that vessel >is stressed relieved Carbon Steel there fore after weld >overlay what will be the requirements of heat treatment >considering sensitization of overlaid Stainless Steel >material.

CO2 Absorber with Pot. Carbonate as inhibitor - even plain carbon steel is good enough. S.S. over lay weld even if stress relieved will not give you any problem except the weld shoudl be smooth ground and there should not be ruogh surfaces after ground finishing. Trust this is of help to you C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai 20 India June 03 >Over-lay welding on CO2 Absorber - Corroded portions with >Potassium Carbonate as inhibitor > >Step 1: Remove all pits and corroded areas in the abosorber >by metal grinding and make the surface as much near same as >possible > >Step 2: Pre-heat the localized areas - corroded portions and >ground out portions to 120-150 deg cent - if possible >before weld over-lay. > >Step 3: If you can maintain pre-heat during welding this >will vastly improve quality of repair welding during first >/second and thrid runs >For this provide, asbsestos cover suit for welders. Pull out >each welder after 15-20 mintues of welding. Welder will get >de-hydrated fast after first two days of welding in such >massive repair welding of corroded portions of CO2 >Absorber. > >Step 3: S.S. 310 or S.S 309 is OK. Inconel 82 is costly to >do. >If dilution of greater than 40% is expected during first run >with 4 or 5 mm electrode , then use S.S 310- Mo or Cb/Ta >stabilized grade ( S.S. 310 Mo / Cb/ Ta electrode)> > >Step 4: After first run covering the first weld layer - Dye >penetrant inspect and grind where excess building done or >areas which have not been properly welded. For this weld has >to be cooled and pre-heat to be discontinued > >Step 5: Pre-heat and do the same for the second and third >or if requried fourth cover runs of welding . From the >second or thirid run you can choose to use even S.S. 308 L - >Mo stabilized grades electorde. >S.S. 309 L- Mo stabilized can also be used. > >Step 6: After each run, grinding to smooth finish and D.P. >test is essential. > >Step 7: Finally a thorough grinding and smooth surface >finish is essential so that the welded rough portions do not >cause problems of corrosino after two years. > >Step 8> Final weld cover run to Dye Penetrant Inspected. > >Step 9: Use Infra-red heating element pads to stress relieve >the weld over-lay portions with insulation lagging from >outside so that heating dissipation is avoided as much as >possible. >Hold at 600-610 deg cent as much as 4-6 hours if you can >attain this temp without dissipation of heat. If you cannot >achieve this temp, heat to 500-550 deg cent and hold for >atleast 7-9 horus ar that temp. > >Step 10> Release temp from S.R temp of 500-600 deg cetn at >the rate of 100 deg cent per hour to come to lower than 250 >deg cent. > >Step 11 : Remove insulation and allow air cooling to >amibinet temp. > >Step 12. RE-inspect the entire weld over lay portions and >grind locally where surface roughness is noted. >Also take a Hardness profile to ensure that hardnesss is >lower than 20 HRc ( 200 BHN). > >Step 13: Use local Poldi type Harness testers to record >profile of hardness. Dye Check all welds once again before >fizing trays and loading and boxing the Absorber. > >This will vastly improve your Absorber corrosion in future > >If you have any questions, please e-mail to > nishi@vsnl.com >C.V.Srinivasan Tech Director Nishi Engineers Pvt Ltd >Chennai 20 India June 02, 2004 > >>At our plant we have a carbon-di-oxide absorber . CO2 is >>being absorbed by K2CO3. It operates on 27 bar pressure and >>120 Centigrades temperature. Presently we are experiencing >>high corrosion of Carbon Steel . So we have planned weld >>overlay on Carbon Steel. Can you please suggest me the >>appropriate material for weld overlay in this service. Can >>SS-309 or inconel 82 be used here. Please note that vessel >>is stressed relieved Carbon Steel there fore after weld >>overlay what will be the requirements of heat treatment >>considering sensitization of overlaid Stainless Steel >>material.