Connection between plate heat exchanger and tubesheet

Plate heat exchanger is a kind of heat exchanger composed of a series of corrugated metal sheets. A thin rectangular channel is formed between various plates for heat exchange. Plate heat exchanger is an ideal equipment for liquid-liquid and liquid vapor heat exchange. It has the characteristics of high heat exchange efficiency, small heat loss, compact and lightweight structure, small floor area, wide application and long service life. Under the same pressure loss, its heat transfer coefficient is 3-5 times higher than that of tubular heat exchanger, the floor area is one third of that of tubular heat exchanger, and the heat recovery rate can be more than 90%.

The connection modes of heat exchanger and tubesheet include expansion, welding, expansion + welding, etc. Ordinary shell and tube heat exchangers are usually connected by welding to ensure the sealing performance and tensile strength of the connection between tube and tubesheet. For the heat exchanger, due to the requirements of working medium and service conditions, the connection mode between the tube and tubesheet of the heat exchanger is expansion + welding. Expansion joint can eliminate crevice corrosion and improve the fatigue resistance of weld. Tubesheet expansion of heat exchanger can be divided into mechanical expansion, explosive expansion, hydraulic expansion and pulse expansion according to different processes. Mechanical expansion joint uses ball to expand pipe, which has the advantages of simple operation and low manufacturing cost, so it has been widely used.

In the actual production, the requirements for the sealing performance of the heat exchanger are often high. In some applications, there is gap corrosion, sometimes accompanied by vibration and fatigue load. Therefore, the structural form of expansion welding is required for the tubesheet connection of the heat exchanger. Therefore, we still need to pay attention to many problems in the actual operation process.