What are the Chinese design standards for heat exchanger tubesheet?
The tube plate is one of the main parts of the shell and tube heat exchanger. The reasonable design of the tube plate is important for the correct selection and saving of materials, reducing the difficulties of processing and manufacturing processes, reducing costs and ensuring safety in use. Therefore, the strength of the tube plate must be properly analyzed to reasonably determine the thickness of the tube plate.
GB151 “heat exchanger” for the design and manufacture of shell and tube heat exchangers, inspection and acceptance of a set of technical requirements must be followed. As a whole, the heat exchanger parameters to which the standard applies are specified. The standard gives the calculation method for the tube plate (see Chapter 7), which can be applied to all pressure and diameter parameters of shell and tube heat exchangers with PN ≤ 35 MPa.
GB151 gives the U-shaped tube heat exchanger, floating head heat exchanger and fixed tube and plate heat exchanger of common structural forms of the tube plate design calculation method. Different structural forms of heat exchanger tube plate, due to the load situation, support conditions, boundary constraints of the different strength calculation methods are different.
U-shaped tube heat exchanger only a tube plate, the standard gives six different forms of connection structure, the calculation model is to the tube plate as a uniform load and by the tube hole uniformly weakened by the ordinary round flat, the calculation method takes into account the influence of the tube plate around the non-clothing tube area on the plate stress.
For the floating head heat exchanger and filler heat exchanger, the fixed end of a tube plate is mostly bolts, gaskets clamped between the shell process flange and tube box flange. The calculation model is to the tube plate of the cloth tube area as an elastic base, by the uniform weakening of the tube hole round flat, the outer perimeter of the tube plate is not cloth tube part as a ring plate, the entire tube plate around the simple support, subject to uniform load. For other forms of connection of the tube plate according to JB4732 standard design.
In the fixed tube plate heat exchanger in the two tube plate and shell process cylinder fixedly connected together, this fixed tube plate can be extended around as a flange, the formation of “extended part of the tube plate as a flange”, can also be directly connected with the shell process and tube box cylinder, the formation of “without the flange of the tube plate”. According to the shell process cylinder and tube bundle thermal expansion requirements, fixed plate heat exchanger may have to set up expansion joints.
In the case of fixed heat exchangers, regardless of the specific structure, the size and material properties of almost all structural elements of the heat exchanger directly or indirectly affect the strength of the tube plate. Because the strength of the plate analysis and calculation process is very complex, so far, most of the national specifications for the calculation of the thickness of the tube plate formula is the actual tube plate for different degrees of simplification and assumptions, the tube plate is seen as a uniform load, placed on an elastic basis and by the tube hole uniformly weakened equivalent circular plate. Professor Huang Keming, Tsinghua University, headed by the preparation team of the pipe plate specification proposed by our standard method, namely GB151 method on the basis of the above simplification also quantitatively consider the following factors on the impact of stress on the pipe plate.
- ① the influence of the presence of the unclothed area around the tube plate (ring plate) on the stress of the tube plate.
- ② the restraining effect of the shell process cylinder (and flange), tube box cylinder (and flange), bolts and gasket system on the corner of the tube plate edge.
- ③ when the extension of the tube plate is also used as a flange, the effect of the flange moment on the stress of the tube plate.
- ④ when calculating the elastic stress of the tube plate, distinguish between the pressure load and the flange moment caused by the primary bending stress and the secondary stress caused by the thermal expansion difference between the tube and shell process, and qualify it with different allowable values.
Source: China Tubesheet Manufacturer – Yaang Pipe Industry Co., Limited (www.ugsteelmill.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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