To all, Here is a link to an an interesting report on the catastopic failure of an amine pressure vessel (an amine absorber tower) that was improperly repaired. After the explosion, the top portion of the vesssel was propelled 1 km.... http://nvl.nist.gov/pub/nistpubs/sp958-lide/350-352.pdf It is interesting to note that: 1) The root cause of the failure was improper welding and thermal cycling in a hydrogen environment 2) Vessels in amine service seem to me to require additional design and welding features not typically perfomed ( these requirements would be similar to the ANSI "K" standard for pressure vessels in anhydrous ammonia service) I would like the comments of the participants above on this article.... CV ?.....what do you think......???? MJC

M.J Cronin et all Your observation on repair and care needed for Rich Amine Stripper / columns. Thank you for your comments and warning of care to repair weld amine vessels by citing this publication of catastrophy in such vessels. I agree that there is a possibility of catastrophic failure due to entrapped hydrogen in amine rich stripper / columns before and while and after doing repair welding. You have rightly stressed this point. If enough care is taken while evolving repair procedure for partial repair of shell portions (corrosion - erosion affected portinos of the shell - which happens mostly due to tray dislocationsand resulting gas-liquid impingement on less inhibited shell portions) catastrophic failures can easily be averted. I was instrumental and we have successfully repair welded a shell portion of CO2 Absorber affected with 10-12 mm thickness reduction in a 44 mm thick shell of over 100- 120 square meter area in one portion of the shell due to tray dislocation and resultant carbon steel shell erosion-corrosion (due to gas-liquid impingement). First time we did with Carbon steel welding only which lasted just for two years. We did this first in 1978. The second time we did built-up with S.S the same 100 Sq Meter area of shell portion and successfully stress relieved at site without any repurcussion of hydrogen entrappment and likely consequential blow out of the vessel. After repairs we did not hae any problem since 1980 for five years before i left the plant. I have inspected personally the vessel five times after repairs - first with carbon steel over-lay and second time with SS over lay welding. All repairs were done in situ and the partial stress relief anneal was done with Infra-red pads meeting to code requirements and care in evaluating the post weld stress and after effects in such service. In this plant, the repaired CO2 Absorber tower is still in service for the last > 22 years without any major problem. - i guess. I had seen similar repair welding done in some other plant doing repair welding. In the other plant also the CO2 absorber tower is in service - i guess- for more than 12-15 years. In both the plants costly replacement of towers did not take place and the vessels are still in service after successful repairs for more than 12- 24 years - i guess. It is important to develop a welding procedure taking into account the design code, process parameters (hydrogen absorption /adsorbption), the likely stress on the shell portions due to welding, the likely relief from stress relief anneal (in-situ stress relieving in the tower itself), the likely distortin in shell during and after welding partial portions in a large tall tower etc. I have reasons to believe catastrophic failures can easily be avoided in such vessels - with care and well developed procedure - taking the metallurgy, corrosion, process and design engineering aspects. Any attempt done without these may lead to catastrophy as mentioned in your web site. I will go through this article - which i am not aware so far. Thanks for the input. Trust this helps and also answer your questions. C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai 20 India E-mail:nishi@vsnl.com/nishi@hathway.com Sept 10,2004 >To all, > >Here is a link to an an interesting report on the catastopic >failure of an amine pressure vessel (an amine absorber >tower) that was improperly repaired. After the explosion, >the top portion of the vesssel was propelled 1 km.... > >http://nvl.nist.gov/pub/nistpubs/sp958-lide/350-352.pdf > >It is interesting to note that: > >1) The root cause of the failure was improper welding and >thermal cycling in a hydrogen environment > >2) Vessels in amine service seem to me to require >additional design and welding features not typically >perfomed ( these requirements would be similar to the ANSI >"K" standard for pressure vessels in anhydrous ammonia >service) > >I would like the comments of the participants above on this >article.... > >CV ?.....what do you think......???? > >MJC