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Judge the three kinds of control valve cavitation damage
Comparative analysis of three kinds of control valve cavitation damage diagnosis method, it is recommended that the valve selection, make full use of the law, control the outlet flow rate to avoid or reduce valve damage. Control valves play a significant role in the fluid industry. Nowadays, as the requirements for energy-saving and emission reduction, improved efficiency, continuous and steady operation, reduction of spare parts for control valves and quick response to after-sales service have been gradually raised, more and more attention has been paid to the problem of how to optimize, select and use control valves. Because the control valve plays the role of actuator in the device, it directly determines the running status of the device. According to the statistics, the ratio of the device stopping due to the control valve is as high as 65%. The selection of the control valve also determines the quality of the produced product And production. Review of the past five years, the rapid development of control valve technology, some of the world's leading control valve manufacturers have introduced the valve in special circumstances, such as high temperature, high pressure, cavitation, flash, part of the abrasive medium, high noise At the same time intelligent diagnostic positioner come out one after another, through the positioner valve can be a good real-time detection, to provide maintenance alarm information to optimize the use of the valve. Undoubtedly, the above mentioned improvements in technology have greatly ensured the stable operation of the device and reduced the number of weaknesses. But how can we calculate and choose the right valve? Experience from the use of that in harsh conditions, cavitation often cause damage to the valve trim, accompanied by high noise, internal vibration, blocking flow and so on, in the calculation of the valve selection, how to reduce, to avoid steam Erosion occurs, the correct use of the valve is essential. At present, valve manufacturers have different evaluation methods of cavitation. In this paper, KE method, δ method and XFz method are mainly used to analyze how to reduce and avoid cavitation and correct selection of valves. Control valve cavitation (cavitation) Control valve cavitation phenomenon refers to the media flow through the valve chamber contraction, the maximum flow rate, the pressure can be the lowest, if the pressure is lower than the saturation vapor pressure of the medium, the liquid gasification, Partially converted to bubbles containing steam or gas. When the medium flow through the shrinkage Department, the pressure rises, if the saturation vapor pressure exceeds the value, the bubble rupture, re-phase from gas (vapor) to liquid phase, the process known as cavitation or cavitation, See Figure 1. When the bubble burst, the release of huge energy jet, and the generation of vibration wave, the laboratory proved that the collapse of 150μm diameter bubble burst jet velocity of 400km / h, resulting in burst pressure up to thousands of kilograms of the valve surface Causing serious impact, erosion and wear (see Figure 2), will lead to severe vibration and high noise, blocking the flow of occurrence. For severe cavitation, the trim will be damaged or the valve operating characteristics will change in a short period of time.