Shell & Tube
The end-user and the end-maker The end-user has first-hand experience of the performance and the reliability of maintenance ; the most crucial feedback for the manufacturer . In its absence , we at Tema India believe that we have ownership of the equipment we sell . This automatically gives us an overview of the problems encountered in maintenance and the improvements that follow . The main lesson learnt is that the product ' s quality should be beyond the code specifications . This varies from type to type if the equipment has to be built for trouble-free service throughout its lifecycle , with maximum efficiency and ease of maintenance . How does this happen ? With important quality parts such as baffles made in-house to the most stringent specifications , the entire tube bundle is produced as per the critical standards established by the manufacturer . The manufacturer assumes the dual responsibilities of checking out on the maintenance side and making changes in the design to accommodate the requirements of the maintenance team . Moreover , the manufacturing sequence is to be adopted and changes made according to the type of equipment . For example , a feedwater heater with a condenser inbuilt is prone to leakages that drastically reduce efficiency . The other example is that of a Hi-Hi screw-plug exchanger with internal leaks in the inner-shell-totubesheet joint . This not only reduces the efficiency but also allows the sulphur-dirty fluid to leak into the clean fluid .
Criteria for lowering cost and increasing efficiency This being the end goal , the manufacturer must aim for :
• Optimisation of the size of the equipment
• Ease of procurement of raw materials
• Ease of manufacturing in terms of time taken and quality attained
• Ease of installation and maintenance at the user ’ s end
To do this , the manufacturer ' s involvement must begin from the very onset of the project when the process parameters are defined . These include operating & design temperature and pressure , heat duty ( total heat transfer rate ), inlet / outlet temperature for hot fluid and cold fluid , maximum allowable pressure drops on the hot and the cold side , and the type of construction ( as per Tema India standards or proprietary ). Finally , the most critical parameter is the selection of fluids concerning the shell side and the tube side . The manufacturer plays an essential role in selecting the shell side or the tube side as hot or cold . For example , in a Hi-Hi screw-plug construction , the side that is at a higher pressure is preferably the tube side . Correct stream allocation simplifies the design , manufacturing , operation and maintenance of the heat exchanger . How to achieve the end goal in the process design of a shell-and-tube exchanger is , therefore , an open-ended question . There are many more variables to choose from when setting the parameters . This calls for a trial-anderror calculation , such as iteration with the help of computational fluid dynamics or CFD .