The tubesheet is usually made of a circular flat plate with holes drilled in it to make the position and shape of the tube or tube accurate with respect to each tube. That tubesheet is used to support and isolate pipes in heat exchangers and boilers or to support filter elements. The tubes are connected to the tubesheet by hydraulic or roller expansion.
The tubesheet can be covered with coating material, which is used as anticorrosive coating and insulator. Low carbon steel sheet can include a layer of higher alloy metal bonded to the surface to provide more effective corrosion resistance without the use of solid alloy, which means it can save a lot of cost.
Perhaps the most famous use of tubesheets is as support elements for heat exchangers and boilers. These devices consist of a dense array of thin-walled tubes in a closed tubular shell. The two ends of the tube are supported by plates drilled in a predetermined pattern to allow the tube end to pass through the plate. The end of the tube passing through the tubesheet is expanded to lock it in place and form a seal.
The hole pattern or "pitch" changes the distance from one tube to another, the relative angle between tubes, and the flow direction. This allows manipulation of fluid velocity and pressure drop and provides maximum turbulence and tube surface contact for effective heat transfer.
Design of heat exchanger tube sheet
If fluid mixing has to be avoided, double tubesheets can be provided. Tubesheet design is a fairly accurate and complex process; it is necessary to determine the exact number of tubes and calculate the pattern of holes in order to distribute them evenly on the tubesheet surface. Large heat exchangers may have thousands of tubes passing through them, arranged in precisely calculated groups or bundles. Sheet design and production are largely automated by computer software (such as CAD) that performs calculations and tubesheet drilling on computer numerical control (CNC) machines these days.
In this design, the outer tubesheet is located outside the enclosure loop, effectively eliminating the opportunity for fluid mixing. The inner tubesheet is ventilated with the atmosphere, so it is easy to detect any liquid leakage.