Tube expansion methods and issues

Durable, tight seating of tubes in tubesheets is vital in the manufacturing of boilers for conventional power generation, heat exchangers for steam generators, and pharmaceutical and food processing systems. When selecting the better method for tube expansion, manufacturers must look at factors such as speed, safety, operator skill requirements, cost, overall quality and repeatability.

With the amount of tubes in a sheet ranging from hundreds to thousands, and the process having to be carried out manually, the stakes are high for achieving a good balance between quality and cost. This blog will cover the common methods used – tube expansion, swaging, and manipulation.

When expanding the tube inside a tubesheet, swaging makes sure that the space between both components is always closed. Hydraulic expansion is direct application of high pressures within a sleeve or tube to form a tight joint between the two components. There are two processes used to achieve such expansions: explosive and direct hydraulic.

Another method is the mechanical rolling method. This works by the use of a set of hardened rolls that rotate in a cage around a mandrel. The rolls create an increasing force which moves the tube material to the desired contact ID. Two other primary techniques for tube expansion are rotary swaging, and linear swaging.

There are some issues that can come with tube expansion. Regardless of method, the general rule is the smaller the clearance the better. The clearance is established by the manufacturers and their ability to fill the tubes through the baffles and tubesheets. This can vary depending on the structure and size of the tube. Some issues that manufacturers come across include leaks, near contact explosions, and axial scratches.

Luckily, Multiform Tubes are highly experienced in tube expansion, manipulation and swaging. Our clients can be assured that their project requirements will be followed in accordance with our methods. If you require our services, please get in touch today.