Answering to .Ramesh's questions on chlorides affecting surface condenser tubes : Surface condenser Tubes : Tubes are normally Inhibited Admiralty Brass is specified. In specific cases, where due to likely sediments at the bottom, some users prefer cupro-nickel (90-10). Chloride levels will not be abnormal in surface condenser tubes normally speaking unless some leaks somewhere in cooling water recirculatin system or in turbine outlet contribute to the chloride level pick up. Admiralty tubes may suffer de-zincification problem after some years where steam condensation takes places. Steam (containing hydrazine in excess - given in boiler water treatment) may produce small traces of ammonia which affects surface condenser tubes (specially inhibited admiralty tubes ) and these tubes fail due to de-zinfication and possible stress corrosion cracking at un-supported portions between the tube sheets due to steam impingement and also due to leaching of de-zincified areas acting as additional stress raisers for admiralty tubes. Admiralty tubes procured in quater hard or half hard condition may also fail faster due to de-zincifcation and scc due to condensing steam having traces of ammonia. In some large surface condensers the bottom portions of the exchanger if not having enough gradient and draining is done improperly may fail due to de-zincification and scc. These are the known causes of failure of admiralty tubes in surface condensers at the exit of large steam turbines. Failure of surface condenser tubes (Brass tubes) due to chloride leaching is not normally heard of . Trust this answers your query. C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai 20 India June 30, 2004 >Dear Sir: > >We hesitate to provide specific upper limits, as the overall >water chemistry issues are too complex. However, Admiralty >brass excanger tubes are quite often used in recirculating >water with typical residual levels of chlorine (usually 1-2 >ppm). > >Hope this helps! > > >David Hendrix >The Hendrix Group Inc.

M.J.Cronin has stated correctly that a discussion forum cannot serve as a material selection / corroion prevention / design criteria /NDT testing selection to be directly adopted / or to be driectly used for predictive inspection method selection except that it may serve to know the problems faced in a particular plant and to share possible experience of some users /designers / corrosin specialists / material specialists who may have seen / solved similar problems elsewhere. M.J Cronin has further amplied correctly that however well intended the discussion forum may serve, it can at best be a guide only for sharing of information f or a particular problem, Each plant is specifically designed to certain known process conditions with limitations on design, material selection, corrosion factors taken into account, corrosion prevention methods adopted, selective inspection techniques used for monitoring conditions etc. Each user may still experience specific unknown problems which need to be studied in detail with proper diagnosis, analysis and consulting the right personnel experienced in the fields of design engineering, corrosion engineering, materials engineering, NDT engineering . Congrats to M.J Cronin for highlighting this aspect clearly. Regards C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai India July 03 >Although this is a simple question to state, the selection >of materials for a steam surface condenser involves a lot of >corrosion knowledge as well as "guesswork" about future >water conditions. > >While admiralty brass has served well for many applications, >some power plants have also used AL6Xn, duplex stainless >steel as well as titanium tubes. > >The selection of tube/tubesheet materials also affects the >physical layout of supports inside the condenser. For >example, titanium tubing, because of its low modulus cannot >be simply retubed into another unit designed for stainless. > >Because the materials selection typicaly involves large >differences in the cost of the unit, I suggest solicitation >of a recommendation from a power plant/thermal consultant. > >I would not base my materials selection on the >recommendations found in an engineering forum, no matter how >well intended......... > >Additionally, estimates and guesses about the future >condition of circulating waters must be made. Many plants >find themselves in a situation where water conditions have >degraded to the point where new materials must be >considered. > >What is the size of the unit and how much chlorides are we >considering here ? > >More info..... > >My opinion only > >MJCronin PE