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Controlled self-priming pumping station Startup water hammer water hammer, off valve and water hammer Water hammer. As long as the pump is started according to the normal operation procedure, it will not cause the start-up water hammer causing the damage, but it will aggravate the change of pressure when the air in the tube can not be discharged in time. Off valve water hammer in normal operation will not cause excessive water hammer pressure. However, due to a sudden power outage or misoperation caused by accident pump stop pumping station generated water hammer often larger values, usually up to 1.5 times normal pressure or greater, so that the pipeline rupture, resulting in a large number of drainage, submerged pump Housing and equipment, great harm.
The dangers of water hammer pumping station in the high-lift or long distance water supply pumping station is particularly prominent. Because of the high-lift pump station or water supply pump station head high, the water pipe long, pipe water storage, water discharge pressure is also large. Therefore, the prevention and treatment of water hammer in pump station should be regarded as an important technical issue. In the new pumping station planning and design, pumping station outlet pipe system should meet the various possible normal and non-normal operating conditions under the conditions of the maximum pressure head or take the necessary control measures, and should pay attention to the pipeline layout, pipe flow rate , Gate selection and valve closure time. The construction of pumping station water hammer prevention and treatment more attention should be paid, because these pumping stations in the open-air laying of the pipeline, subject to wind and rain erosion, rust spalling; internal flow of sand particles drive the friction wall, pipe corrosion, with the passage of time , The wall gradually thinning, can not afford to withstand the original can withstand the pressure of water, coupled with the operation of the water hammer to expand its pressure, pipeline rupture greater probability, it is necessary to take measures to prevent water hammer.
The current water hammer prevention and control measures are more commonly used measures are summarized below.
Pressure tank
Pressure tank is generally used for small flow, high head pump unit. Pressure tank is cylindrical, installed in the outlet valve after the check valve. When the pump is running normally, the water pressure in the outlet pipe compresses the air in the tank. When the pump is shut down, the air in the tank expands rapidly due to the pressure drop in the outlet pipe, and the outlet water pipe is rapidly supplied to the lower part of the water pipe, When the check valve is closed, the pressure in the pipeline rises, and part of the water enters the pressure tank, raising the water level in the tank and compressing the air in the tank, thereby reducing the pressure increase in the water outlet pipeline.
2 pressure regulating tower
The pressure regulating tower is a buffered water hammer protection facility. When the pressure in the pipeline is reduced, it can replenish the pipeline quickly to prevent negative pressure in the outlet pipeline and reduce the pressure rise in the outlet pipeline.
Pressure regulating tower built in the pipeline may produce negative pressure parts. Pressure regulating tower In the horizontal single-stage centrifugal pump start-up, operation and shutdown process, the tower water level changes little, and the pressure wave can be reflected back to the upstream side of the pressure regulating tower, but there should be large enough cross-sectional area and volume , In case of replenishment in the process of water will drain the tower to make the air into the main pipeline.
3 slow closure Min
Normal check valve due to the valve plate closed for a short time, causing a lot of water hammer boost value. Slow-closing check valve is based on the buffer mechanism to make the check valve plate slowly closed water-type water hammer protection equipment, mainly used to prevent the pipeline system pressure rise.
Slow-closing check valve with large and small drain hole damping cylinder, piston and other components. When the accident is shut down, the water flow in the pipeline starts to flow backwards. The swing-type valve plate starts to close under the weight and the backflow water. When the shut-off valve reaches a certain opening degree, the oil discharge hole of the damping cylinder is converted into a small hole, Reduce, form the damping, cause the valve plate to close slowly, so as to reduce the impact of the valve plate on the valve seat and the increase of the water hammer pressure in the pipe. In addition, the normal operation of the valve plate weight balance with the lever to reduce the resistance of the flow of the valve plate, the water flow through the check valve head loss is greatly reduced.
Air valve
Air valve, also known as into the exhaust valve, when the pressure within the pipeline less than atmospheric pressure inhaled air, higher than the atmospheric pressure of air discharge. This valve does not allow liquid to flow out of the line and has an automatic shut-off function after the air in the line has been eliminated. Usually installed in the long water pipeline height or obvious bulge.
Air valve has the advantages of simple structure, low cost, safe and convenient, not subject to installation conditions and other advantages.
Water hammer eliminator
Water hammer eliminator is mainly used to prevent the pressure from rising. It is installed in the outlet side of the check valve, stop the pump after the first tube pressure is reduced, the valve flap falls, the drain open; then the tube pressure rises, the pipeline part of the high-pressure water from the drain outlet, so as to reduce the pressure Increase, protect the purpose of the pipeline.
Flue tube
For the lower head, pressure hose short wear-resistant mortar pump, mixed flow pump, the general cut off the door. In order to discharge the influence of the air in the pipeline on the start of the unit and reduce the impact of closing the door when the stoppage is shut down, the vent pipe should generally be provided. Before starting the unit to be filled with water, the valve should be set on the vent pipe, the valve will be closed when the unit is filled with water, the valve should be opened after the unit is started and put into normal operation. The height of the ventilation tube should be higher than the highest level of the pressure tank.
Water hammer prevention and control measures are more, there are many other ways, according to the specific circumstances of the pumping station, select the appropriate control measures.
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Due to the drastic changes of the flow velocity in the outlet pipe, the hydraulic impact that causes the pressure of water flow in the pipeline to alternately increase and decrease rapidly is called the water hammer phenomenon or water hammer phenomenon.