To some degree all tube to tubesheet joints leak. Low pressure water or air 2. For welded and expanded joints the author further recommends welding and expanding criteria and nondestructive examinations.
seal welded tube to tubesheet joint
After completion of non destructive examinations the pullout.
Seal welded tube to tubesheet joint. Design engineers have basically two weld options for a tube to tubesheet joint. The seal weld is subjected for visual examination helium leak test hlt and floroscent lpe as per astm e 165 type 1 method c for examination of lack of fusion at the edge of hole in the tubesheet surface pores cavities cracks etc. 1 roll or expand with grooves milled in tube holes and seal welded or 2 strength welds no grooves required. Evaluating tube to tubesheet welding types.
Roll or expand only without grooves strength is poor leak resistance is poor tube replacement is very easy application is limited ie. Standards and codes worldwide the vast majority of shell and tube heat exchangers used in the cpi are built according to the standards of the. Arnab tema code standards prescribe conditions for class b class c class r type exchanger manufacture. Tube to tubesheet seal welding is carried out by autogenous pulsed tig process after rolling.
This is based on leak tolerance permitted in joints from process fluids or vapor exchanges tube to tube sheet roll tolerances and the leak permitted with seal or strength welding and also based on the type of explosive limit to which crititcal solvent exchange takes place. Tube to tubesheet joint details acceptable weld joints where a is not less than 14t acceptable tube to tubesheet welds acceptable weld joints where a is less than 14t thermal rating and vibration analysis thermal performance rating calculations are required in order to show that the heat exchanger will perform as expected. While welded expanded joints are the most leak resistant hydrogen may pass through welded joints. To ensure leak tightness the author suggests using seal or strength welding followed by expanding tube to tubesheet joints.
When welding the tubes to the front face of the tubesheet for tightness or strength subsequent expanding beginning about 38 to 12 beyond the weld should be called out to avoid failure of the welds which may result due to cyclical loads from. There are four types of tube to tubesheet joints.
