In the multi-stage centrifugal pump pressure pipeline, due to the drastic changes in the flow rate, a series of sharp hydraulic pressures that alternately rise and fall are called water hammers, also called water hammers. The hazards of stopping the pump water hammer are mainly manifested as: the general water hammer accident caused the destruction of multi-stage centrifugal pumps, valves and pipelines, causing “running water” and stopping water; serious accidents caused the pump house to be flooded, and some equipment was hit. Bad, hurting the operator and even causing the death of the person. The following is a description of measures to prevent excessive boosting of multistage centrifugal pumps:
1. Set the air cylinder. It utilizes the principle that the gas volume is inversely proportional to the pressure. When a water hammer occurs and the pressure inside the pipe rises, the air is compressed and acts as an air cushion. When a negative pressure is formed in the pipe, even when the water column is separated, it can replenish the pipe. It can effectively reduce the hazard of stopping the pump water hammer. Its shortcoming is that steel is needed, and the air can be partially dissolved in water. It is necessary to have an air compressor to constantly supply air into the cylinder (for example, if a rubber airbag is installed in the cylinder to isolate the air from the water, the air supply equipment may not be used frequently) . At present, air cylinders with rubber airbags have been promoted at home and abroad.
2. Set the open water hammer eliminator. When the multi-stage centrifugal pump is in normal operation, the upward pressure of the water pressure on the valve plate in the pipeline is greater than the downward pressure of the weight and the valve plate, the valve plate is in close contact with the valve body, and the water hammer canceller is in the closed state. . When the pump is suddenly stopped, the pressure in the pipeline drops, the downforce acting on the valve plate is greater than the upper support force, the weight falls, and the valve plate falls in the water taper, thereby connecting the pipe to the drain port. When the water flow in the pipeline reverses and closes the check valve and causes the pressure in the pipeline to rise, a part of the water is discharged from the drain port, so that the water hammer pressure is greatly weakened, and the pipeline and the fitting are protected.
3. Automatically reset the open water hammer eliminator. It has the advantages of a common lower open eliminator and can be automatically reset. The working principle is as follows: after a sudden power failure, a pressure drop occurs at the beginning of the pipeline, and water outside the water hammer canceler cylinder flows downward through the gate valve, and the water in the cylinder flows through the check valve. At this time, the force of the lower part of the piston is reduced. Under the action of the weight, the piston descends into the cone and the nozzle of the drain pipe opens. When the maximum water hammer pressure comes, the high pressure water flows out through the eliminator drain pipe, and a part of the water passes through the single. The borehole on the gate valve is poured into the cone, and the water hammer gradually disappears with time. The amount of water in the lower part of the piston in the cylinder gradually increases, and the pressure increases until the weight is reset. In order to make the weight smooth, the upper part of the eliminator is provided with a damper piston rising, and the drain pipe port is closed again, so that the water hammer elimination function is automatically completed.
4. Cancel the check valve to cancel the check valve at the pump outlet. When the water flow is reversed, it can be drained back to the suction well through the multi-stage centrifugal pump. This will not generate a large water hammer pressure; it can also reduce the head loss. Save power. However, reversing the water flow will impact the pump to reverse 'may cause the sleeve to retreat and heavy} the black plug is loose (when the bushing is threaded). In addition, other corresponding technical measures should be taken to solve the new problems brought about by the elimination of the check valve. In the case of canceling the check valve, the calculation of the pump water hammer should be performed.
5. The use of slow-closing valve slow-closing valve has a slow-closing check valve and a slow-closing check butterfly valve, they can be used in the pump station to eliminate the pump water hammer.
6. Other measures include setting the automatic slow-closing hydraulic gate valve; if the gate is controlled, there is no check valve, and according to a certain procedure, the standing water is used to slowly close the water outlet valve to eliminate the water hammer damage; after the sudden power failure, the pump shaft ( Or the motor shaft) adopts the "brake" measure. After the pump loses power, the water flow is allowed to fall back, but the impeller does not rotate, which can greatly reduce the boost voltage, and also avoid some problems caused by the high-speed reversal of the impeller.
