Why do not open the valve when the speed switch off? In the pipeline quickly open and close the valve, it will produce a water hammer phenomenon, in close to the valve at the pipe section produced a water hammer pressure value. According to the calculation, the pipeline liquid flow rate changes every 1m / s, the liquid generated pressure value can reach 1MPa, not only the pressure value is also in the form of water shock wave from the valve close to the pipe section to the speed of sound velocity upstream to spread ( The speed of the sound in the water 1500m / s, the speed of gasoline in the 1100m / s), and it points along the original pipe pressure to add up, it may reach the extent of the pipeline rupture. Slow, and gradually open and close the valve, due to the instantaneous time, the speed of change is small, the initial pressure generated by the value is small, and because of the time, water hammer wave propagation to the upstream, will produce a reflected wave, The initial water hammer pressure, so to avoid the pipeline overpressure accident. 1) Reasons: there are debris in the medium, solid particles pad between the valve and the valve seat. Stem and the valve flap is not good, so that the valve flap and valve seat deflection can not be in strict contact. 2) approach: to ensure that the media clean, close the valve when the valve is found pad phenomenon, not hard hard off, can be used several times the rapid switch approach to the mat stuffed out. Often to the stem and stem nuts add lubricant to ensure that the valve switch and flexible. The valve does not open, not on the reasons and treatment is what? I) reasons: the stem and the stem nut between the debris or meshing is not good, stem and disc from the stem and stem nut corrosion , The valve flap force is too large and the packing pressure too tight. 2) treatment: often to the stem and stem nut lubrication and removal of debris; stem and valve flap, should be disintegrated overhaul; valve force is too large, when the pressure after opening the valve.
Do not shut down the speed of the valve and the reasons for the valve is not on the approach
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