What is the expansion joint of heat exchanger
The heating conditions of tube bundle and shell of tube heat exchanger are different, so the thermal expansion rate is also different. In order to prevent the stress caused by different thermal expansion and damage the heat exchanger, it is necessary to add a component that can buffer the stress. This component is the thermal expansion joint.
In the heat exchange process of fixed tube sheet heat exchanger, there is a certain temperature difference between the tube bundle and the shell, while the tube sheet, the tube bundle and the shell are rigidly connected. When the temperature difference reaches a certain temperature, the excessive temperature difference stress will often cause the damage of the shell or the bending of the tube bundle, so when the temperature difference stress is large, floating head, U-shaped and stuffing box heat exchangers can be selected.
However, the cost of the above heat exchanger is relatively high. If there is no need to clean between tubes, the fixed tube sheet heat exchanger can also be used, but the temperature difference compensation device, such as expansion joint, needs to be set.
Expansion joint is a flexible component installed on the shell of fixed tubesheet heat exchanger. Because of its large axial deflection, small axial force can produce large deformation.
The deformation difference between the tube bundle and the shell is compensated by the flexible component, so as to reduce the temperature difference stress between the tube bundle and the shell caused by the temperature difference, and at the same time, it is also conducive to the connection between the tube bundle and the tube sheet not to be pulled off.
The expansion joint can also be used in various industrial equipment, machinery and pipelines as a component to compensate displacement and absorb vibration.
The main part of the expansion joint is the bellows (also known as wave shell). There are many kinds of expansion joints, such as flat expansion joint, Ω expansion joint and corrugated expansion joint.
As shown in the figure below.
In production practice, the most widely used is the corrugated expansion joint, followed by the Ω expansion joint. The former is generally used in the situation of large compensation, while the latter is mostly used in the situation of high pressure.
The thinner the expansion joint wall is, the better the flexibility is, the stronger the compensation capacity is, but the lower the pressure it can bear. There are two types of corrugated expansion joint: single layer and multi-layer.
If the wall is multi-layer, the pressure it can bear will increase, and it can still maintain a large compensation capacity.
The structure of multi-layer corrugated expansion joint has many advantages over single-layer expansion joint. Because the wall of multi-layer expansion joint is thin and multi-layer, it has large elasticity, high sensitivity, strong compensation capacity, high bearing capacity and fatigue strength, long service life and compact structure. If more compensation is required, multi wave expansion joint can be used.
The compensation capacity of one wave of expansion joint is determined by its shape, size and material. For example, the lower the wave height is, the better the pressure resistance is, and the worse the compensation capacity is; the higher the wave height is, and the larger the wave distance is, the greater the compensation capacity is, but the worse the pressure resistance is.
Source: China Expansion Joints Manufacturer – Yaang Pipe Industry (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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