Salmanffc Could you elaborate a little further - what is the distance between the M.P. condensate tube and the intermediate tube sheet ? Is 4 Meter distance (space) is available only at the bottom of M.P. condensate area ? or any space is available at the intermediate tube sheet between M.P condensate and BLS separation? From your description it is not clear if such distance is available or it is not clear how did the original fabricator rolled accurately the tubes and what type of tooling they used to have such a tight clearance rolling at the intermediate tube sheet to tube clearances? If M.P. Condensate is leaking from high pressure 28 KSC to low pressure (BLS) side - 7 KSC, your shell side SRV should be blowing quite often? Is it occuring regularly? Or is the shell designed for 28 KSC ? There is also a possibility of condensing steam creating vacuum in the down stream equipment? Do you have any vacuum breaker against such possibility in your system in upset conditions of leaks in exchanger? Is it only condensate carry over or erosion in the tube to tube sheet joints you suspect? (i.e,only some erosion - corrosion at the intermediate tube sheet to tube rolling joints?). Is it occuring only after 15 years of opertaion or it has been happening regularly in the last 15 years ? or is it some urea carry over occuring at the intermediate tube to tube sheet rolled joints? Unless these points are explained clearly, it is difficult to guess. Please elaborate further on all these. It may possibly help to think of some repair approach. Off-hand solution may be difficult to come for such complicated vertical exchanger design (with medium pressure combined with low pressure steam). Trust this helps you C.V.Srinivasan Nishi Engineers Pvt Ltd India July 18,2006 E-mail: nishi@vsnl.com >One of our vertical heat exchanger installed at Urea Plant >in Pakistan has leakage problem in its intermediate tube >sheet. > >The exchanger consists of two sections. Boosted low pressure >steam (BLS) at 7 kg/cm2 is used in the upper part while >Medium Pressure (MP) Condensate at 28 kg/cm2 is in the >bottom part as heating medium on the shell side. > >The two parts are separated with an intermediate tube-sheet, >which is leaking and causes mixing of MP condensate with BLS >in the upper part. > >The exchanger is 15 years old and in continuous service. The >tubes were expanded in the tube sheet during manfacturing. >The thickness of tube is 2.11 mm and its OD is 38.1 mm >(Material: SS 316L), Tube-sheet material is ASTM A-266 Class >2 and thickness=146 mm. > >Can any one suggest repair method for the rectification of >intermediate tube-sheet leakage? > >Space of 4 meters is available at the bottom for re-rollig >of tubes in the tubesheet but for re-rolling we have >following concerns: > >1. Damage to tubes during repairs by re-expansion to rectify >the tubesheet leakage. >2. Presence of foreign particles between tube-tubesheet. >3. Condition of tube and tube sheet at leaking area is not >known. Thickness reduction of tubes is also not yet >measured. > >Do any one has any experience to share with respect to >intermediate tube-sheet leakage repair for old exchangers? > >Comments and repair methods for the said problem is >requested on urgent basis and will be highly appreciated.