Valves important parameters are the valve flow coefficient and cavitation coefficient, which in the advanced industrial countries generally available in the valve information, and even printed in the sample also. China's production of the valve is basically no information in this area, because access to this information need to do experiments can be made, this is our country and the world's advanced level of the valve one of the important performance gap. First, the flow coefficient of the valve The flow coefficient of the valve is a measure of the ability of the valve flow index, the greater the value of the flow coefficient, the smaller the pressure loss when the fluid flows through the valve. According to KV value calculation formula: KV-flow coefficient Q-volume flow m3 / hΔP-valve pressure loss barP- fluid density kg / m3 Second, the cavitation coefficient of the valve cavitation coefficient δ value to select For control of flow, choose what kind of valve structure type. Where: H1 - the pressure after the valve (outlet) mH2 - the difference between the atmospheric pressure and the saturated vapor pressure corresponding to its temperature mΔP - the pressure difference before and after the valve m due to different structures of various valves, so the allowable cavitation coefficient δ is also different. as the picture shows. If the calculated cavitation coefficient is greater than the allowable cavitation coefficient, then it is available and no cavitation will occur. If the butterfly valve allows cavitation coefficient of 2.5, then: If δ> 2.5, then cavitation does not occur. When 2.5> δ> 1.5, slight cavitation can occur. When δ <1.5, vibration occurs. δ <0.5 continued to use the case, it will damage the valve and downstream piping. The basic characteristics of the valve and operating characteristics of the valve, the valve cavitation occurs at a time when it is out of sight, not to mention that at that point to reach the operating limit. Through the above calculation is clear at a glance. So cavitation, because the liquid flow acceleration process of rotor pump through a tapered section, the part of the liquid gasification, the resulting bubble followed by the valve after the open section burst, the performance of three: (1) the occurrence of noise (2) vibration (In severe cases, it can cause the destruction of the foundation and related structures, resulting in fatigue fracture.) (3) Damage to materials (erosion of valve body and pipeline) From the above calculation, it is easy to see that there is cavitation and pressure behind valve H1 Big relationship, increase H1 will obviously make the situation change, to improve the method: a. The valve installed in the pipeline lower. b. Install the orifice plate on the pipe behind the valve to increase the resistance. c. Open the valve outlet, direct reservoir, so that the bubble burst space increases, reduced cavitation. Based on the above four aspects of analysis, discussion, summed up the gate valve, butterfly valve main features and parameter list easy to choose. Two important parameters in the valve used to play a decisive role. More Keywords Search: Valve