What are the materials that can be used for plate heat exchanger rubber pads? _
What are the materials that can be used for plate heat exchanger rubber pads?
795 gasket is a key component of plate heat exchanger. The working temperature of the plate heat exchanger is essentially the temperature that the gasket can withstand, and the working pressure of the plate heat exchanger is also restricted by the gasket. According to analysis, the length (m) of the periphery of the seal is 6 to 8 times the heat exchange area (m2), (for example: a single plate heat exchanger with an area of u200bu200b0.5m2 plate, the expansion length of the gasket is about 4m ). The plates are very thin and have poor rigidity, and only elastic materials can be used to make sealing gaskets, and they are not high in temperature. The rubber gasket of the plate heat exchanger should have a compressive amount that can be sealed, and the amount of compression should ensure that the groove is not deformed. 1. Non-adhesive gaskets, compared with traditional adhesive gaskets, are complicated, time-consuming, material-consuming, inconvenient to assemble and disassemble, and may even affect human health and cause plate gaskets due to harmful components in adhesives and cleaning agents. The groove is corroded and cracked. Therefore, the application of non-adhesive gaskets is becoming more and more extensive, and in some occasions, local application methods can also be used. Generally, it only takes a few minutes to install (replace) one gasket, which saves 80%-95% and 70% of the time and labor compared with pasted gaskets. It is especially convenient for on-site replacement and greatly reduces maintenance costs and downtime losses. The non-adhesive gasket and the corresponding parts of the plate have special structural shapes. The two are connected by mechanical methods. There are many varieties. They can be roughly divided into two types: 'embedded' and 'clip type'. The applicable temperature reaches 165 ℃ , The pressure is 2.5 MPa. 2. Reliable plate positioning system In order to make the plate and gasket seal position accurate and reliable, prevent up and down or left and right slippage, and extend the life of the gasket, ALFA-LAVAL, APV, GEA, BN, etc. all use different Plate positioning structure. 3. Gasket material and performance evaluation The weaker link of PHE is the gasket. Over the years, it has been the focus of public attention and exploration, and some progress has been made in temperature and corrosion resistance materials and their performance evaluation. (1) Nitrile rubber (NBR) is generally suitable for working conditions below 120 ℃, the newly developed high-temperature NBR can reach 145 ℃, and the hydrogenated NBR can reach 160 ℃; EPDM was only used for 150 in the past. ℃, high temperature EPDM has increased to 160 ℃; Fluoro-propylene rubber (FPM) can be used at 175 ℃; graphite laminated gaskets can be used at temperatures up to 400 ℃, which can well replace compressed asbestos fiber gaskets. (2) Coated gaskets use general rubber or metal blocks as the core, and are coated with polytetrafluoroethylene (PTFE) or fluorinated synthetic materials. They can be used for highly corrosive media or to increase the temperature limit. HISAKA is the first to use PTFE-coated NBR gaskets, which greatly expands the application areas of PHE and extends the service life of gaskets. ALFA-LAVAL has used this gasket for double-plate welding PHE. (3) With the development of non-adhesive gaskets, the formulation of materials for non-adhesive gaskets must be slightly changed, requiring more stable performance, more durability and better tear resistance. (4) To evaluate the temperature resistance of gaskets, there are two main indicators: compression set and hardness at rated temperature. For new gasket materials, generally the ring sample test and the overall test of the plate and the gasket are required, and the test time is 5-40 days. The recommended use temperature limit of gaskets should be lower than the compression set curve after considering a certain safety factor. The quality and service life of the plate heat exchanger largely depend on the quality and service life of the gasket. For large logarithmic heat exchangers, the plates are generally not damaged, and the gasket is prone to ageing and cause leakage. Therefore, the quality of the gasket determines the quality and service life of the heat exchanger.