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Domestic control valve used in the process of problems
If the domestic control valve design level, the level of production and advanced countries compared to a certain gap is real, but if there is a big gap, it may not be realistic. So, why the use of domestic control valve and the time is far less than the introduction of products? As long as the comparison of China's valve selection calculation form selection table with foreign calculations, not difficult to find that our content is too simple. Such as the American Society of Instrumentation standard format listed 49 serial numbers, our form less than 20 serial numbers, many of which are not included, inevitable selection, not comprehensive, resulting in "congenitally deficient"; then there is the domestic standardization of the valve is too high , To be a changeable, rather than "the right medicine", be treated differently. Only to the valve leakage, for example, the user reflected more intense. It involves not only the selection of structures. Also involved in unbalanced force calculation. Who carefully consider it? If not, it will inevitably result in the uselessness of the system, such as death, inseparability, large leaks and poor reliability of the seal (which can be started and will not take long). To solve it, it must be carefully considered, it includes: (1) According to the valve closing differential pressure, calculate the unbalanced force to determine the size of the valve structure and actuator, first of all to ensure that the required output power sufficient. (2) to determine the best flow to facilitate sealing. (3) valve structure considerations, the pressure, large diameter valve (such as DN100 valve, △ P = 20MPa, the imbalance thrust up to Ft = 0.25π × 102 × 20 = 15.7t), the structure of careful consideration Very important, including balance and resistance to cavitation erosion, erosion considerations. (4) not clean media, fouling of the anti-clogging media considerations, blocked, stuck, how can be sealed? (5) Corrosive media, throttle parts of the corrosion resistance to be considered, and inevitable Reliable, many valve leaks on the run soon exceeded, the reason is that the throttling pieces are corroded. (6) on the type of seal considerations. a. hard seal or soft seal; b. whether the need for surfacing wear-resistant alloy, to improve reliability; c soft seal type and soft seal material. (7) Leakage level, test method, test pressure, acceptance method and so on. This shows that rough considerations, inevitably get the rough effect of use: most of the general products can, therefore, a slight consideration owed and special occasions, the valve certainly not good to use. To sum up, the main problem of the application of domestic control valve is: Calculation, selection is not comprehensive, resulting in "congenitality"; manufacturers too single product, can not meet the various needs. The solution is: first grasp the quality of the first pass (also the manufacturer does not attach importance to the one off) signed the contract, the review of the selected valve can effectively meet the working conditions and requirements, to overcome the "congenitality"; followed by the production plant Production of various products, especially special products, variant products to meet the needs of special occasions. To do these two points, both the selection personnel and the manufacturer must be proficient in the application of the regulating valve.