Typically, in the valve using the process will encounter many problems, why these problems? Then JINGYI valve tells us: The first is through the valve or in the downstream pipeline, a large pressure difference to produce a high speed. In liquid operation itself will produce turbulence and vibration, high noise level generated in the gas operation. The velocity and pressure loss is inversely proportional to and obtained when the the logistics movement to contraction sectional speed in slightly by contraction sectional exactly maximum peak, where the pressure is at its lowest point.
Generally, a temperature close to the saturation point of the process liquid must be to maintain the speed of less than or equal to the 30ft / s (9m / s) in order to avoid the fluid pressure drops below the vapor pressure and cavitation. This 30ft / s shall also apply to cavitation operation, here a higher speed to cause the greater cavitation damage of the downstream pipeline. The lower speeds will also reduce the flash and wear problems. Followed by flashing, in liquid operation, when the downstream pressure is equal to or lower than the vapor pressure, at a vena contracta to generate steam vapor bubble and maintain not injury and not pinched. Because pressure recovery high enough to produce such a situation. This phenomenon is called a flash. When the generated flash downstream fluid is a mixture of vapor and liquid and a high velocity mobile, resulting in wear within the valve and the downstream pipeline. The curve represents the pressure outlet pressure below the vapor pressure, resulting in flash Unfortunately, the complete elimination of the flash relates to improve the system itself, especially the downstream pressure and vapor pressure. However, not all systems are easy to be improved and these may not be a choice of program. To consider the position of the valve, especially if the pneumatic control valve downstream logistics emissions into a large container, such as storage tanks or condensers. The valve placed close to the container at the enable logistics collision within the larger volume into the container and away from any major surface. The event of flash to remove hardened spool material on the valve design solutions, such as the commonly used anti-cavitation valve core or cavitation control spool.
Finally, the water hammer effect, in liquid operation, regardless of where the logistics suddenly stopped, and produce large amounts of vibration waves both in the upstream and downstream, and this phenomenon is called water hammer effect. It is normally closed when the valve close to the closed element suddenly suction valve seat the (dissolved cylinder latchup), caused by the sudden closure of the sudden closure of the pump or valve. Control valve dissolved cylinder latchup is caused by the implementation of the low-thrust mechanism, the actuator does not have sufficient rigidity in order to keep close to the valve seat. In some cases, having a quick-opening or installed linear flow characteristics of the valve can also cause the water hammer effect. Although water hammer is a lot of noise, but true it sense the damage is caused by mechanical failure caused. Changed dramatically by the kinetic energy into the static pressure of the pipeline, known water hammer will break through the pipeline or damage the pipe bracket and damage to the pipeline joints. Vibration through the spool valve, water hammer, it may lead to the failure of the spool, gaskets or packing.
Therefore, the valve, the best defense the way of the water hammer is to prevent any sudden change in pressure. These include slowing down the closure of the valve itself, or when the closing element close to the valve seat to provide a greater degree of rigidity. To prevent pressure fluctuations, the valve should be closed. Uniform changes in speed In some cases, when using the quick opening or fix the linear features (it is close to the quick opening characteristics), the requirements change equal percentage characteristics. For the throttle of the control valve must be close to the seat when using the abnormal stiffness executing agencies, such as the the spring cylinder pneumatic actuator or a hydraulic actuator, or in manual fourth stroke of the operation of rotating on the sleeve setting special notches , will reduce or prevent the dissolution cylinder latchup. In the pipeline system, some type of fluctuation preventing measures can also reduce water hammer. Which can use pressure relief valve or inflatable hose completion the inflatable hose can reduce the length of the pipeline. In addition, the gas may be injected into the system, the injection of gas can reduce the density of the fluid to deal with any sudden fluctuations and provides some compression.
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