Krish True: High vapor velocity would give problems in "T" (directional change) and this would be worse comparatively at elbows (bends) and at immediate downstream locations of control valve (TCV,PCV, orifice plates, TI, PI points) where straight lengths if piping designer had not taken adequate care to have minimum straight lengths as per piping code needs for a particular fluid velocity at high tempertaures. Loose coke should get genrally carried away in the piping system with high vapor vaelcity at high temperature except at dead ends of flanged joints or end caps in piping. Thermal imgaing will give a quantitative indication of drop in skin temp profile due to coking problem but it does not help at all in any qualitative and quantititive assessment of erosion related damge due to coke built up or loose coke scales being continuously blown with high vapor velocity streams in process fluid piping. Continous operaton with coking and high temperature close to design or above design conditions may affect piping from both short term rupture and long term creep related damages. Trust that this helps you to look at UT thickness during a shut down. C.V.Srinivasan Nishi Engineers Pvt Ltd India Nov 20, 2006 E-mail; nishi@vsnl.com >Thanks Mr.Srinivasan, >Due to high operating temperature and inaccessibility >carrying out UT Thickness measurement is a difficult task >due to safety point of individual.Since we have thermal >imaging camera with that we could measure the skin and >process fluid temperature.We could see the drop in >temperature at coke location and normal reading at remaining >sound portion.Due to coking at dead end (area like T-Joint >with manhole cover for inspection)and due to high vapor >velocity voritis are formed around coke and localised >erosion is taking place. >regards,

In my previous posting intead of pipe wall thickness I should say Skin Temperature Excuse me for the misunderstood Regards Luis