To my understanding you are facing pitting at tube insides. MIBK is non-corrosive nature. MIBK coolant heat transfer lead to moisture condensastion inside tube and in case of low-flow, stagnancy this condensed moisture can cause pits. Use some moisture absorber to dry the inert gas. Other pl. opinion. regards

Krish Inert gas supply to tubes: Are you sure that the tube side is moisture free always? I had seen plants using inert gas generators and the exit line from IG generator had traces of moisture either at the start of generator time or during shut down time of inert gas generator. This has happened even for lines where catalysts have to be maintained with Inert gas purging or boxing up during major turn-arounds (to preserve the catalysts in process plants). Problems faced dur to moisture traces in I.G system affecting the catalyst performance in process plants are too well known(during re-satrt of the process (due to basic assumption is made that the inert gas supplied is free of moisture trace). It looks like your pitting in the chiller tubes could be initiated inside the C.S tubes once inert gas supplied has moisture traces in the tube. Once pitting is initiated, failure rate depends on how frequent your I.G supply is shut down and re-started or the lines supplying inert gas to this particular heat exchanger is having traces of moisture. If moisture trace is the problem (likely to be present in the supply line during start up or shut down conditions of either upstream or down sream equipment in a process plant), then try improvemetn with S.S 304 tube. If moisture trace is analyzed and identified as the likely problem for this exchanger, better monitoring of moisture trace and use of silica gel filtrationat the inlet entry to tube side for this particular chiller cooler should help you to solve this problem. With moisture analysis in inert gas and improvement with silica gel filtration at the extry point, even carbon steel may serve you well and more long lasting than this frequent failure. Trust this is of help to you C.V.Srinivasan Nishi Engineers Pvt Ltd India June 03,2006 E-mail: nishi@vsnl.com >We had frequent failure of inert gas cooler in chilled >solvent service. Shell side is MIBK Solvent and tube side is >inert gas with little moisture. The present metallurgy is >carbon steel and due to pitting the service life of the >particular cooler is only 12-18 months.Any better metallurgy >to combat the corrosion problem. Pitting type corrosion is >more prodominant.