Centrifugal pump in the start, need to pay attention to a lot of things, but centrifugal pump start need not need to close the outlet valve? Let's find out together:

    Why do you need to close the outlet valve when the centrifugal pump starts?

    Centrifugal pumps in the start, the pump is not yet water in the export pipeline, so there is no pipeline resistance and lifting height resistance, in the centrifugal pump start, centrifugal pump head is very low, the flow rate is very large, at this time, the pump motor (axial power) output is very large (according to the pump performance curve), it is very easy to overload, it would be made to the pump motor and the line is damaged, so the start to shut down the export valve, in order to make the pump run normally.

    If the pump with axial flow on the opposite situation, it must be open-valve start, the power of the motor at this time the minimum for a short period of time due to the absence of resistance, will be partial to large flow operation, often pump vibration, noise, and even motor overloading, the motor will be burned. Close the outlet valve, equal to the artificial set pipe resistance pressure, with the pump after normal operation, slowly start the valve, so that the pump along its performance curve law gradually normal work.

    Centrifugal pumps must be guaranteed before starting two points.

    1, the pump casing is filled with water, the purpose is to form a vacuum.

    2, must close the gate valve on the outlet pipe, so that the pump did not form the flow, can reduce the motor starting current, conducive to the smooth start of the pump, with the smooth start of the pump should slowly open the gate valve in time.

    Centrifugal pump is relying on the impeller centrifugal force to form a vacuum suction to lift the water, so the centrifugal pump start, you must first close the outlet valve, water. Water level over the impeller parts above, discharge the air in the centrifugal pump, before starting, after starting, the formation of a vacuum around the impeller, the water upward suction, which can be automatically opened to lift the water. Therefore, the outlet valve must be closed first.

    About centrifugal pumps

    Centrifugal pump is a kind of vane pump, relying on the rotating impeller in the process of rotation, due to the interaction between the vane and the liquid, the vane will transfer the mechanical energy to the liquid, so that the pressure energy of the liquid is increased, to achieve the purpose of transporting the liquid. Centrifugal pump work has the following characteristics:

    ① Centrifugal pump pump in a certain speed under the head produced by a limited value. The working point flow rate and shaft power depend on the situation of the device system connected with the pump (level difference, pressure difference and piping loss). The head varies with the flow rate.

    ② Stable operation, continuous delivery, no pulsation in flow and pressure.

    ③ Generally, there is no self-priming ability, and the pump needs to be filled with liquid or the pipeline needs to be vacuumed before it can start working.

    ④ Centrifugal pumps are started under the closed state of the valve of the discharge pipeline, and vortex pumps and axial flow pumps are started under the fully open state of the valve to reduce the starting power.

    Before the pump starts, the pump casing is filled with the liquid to be transported; after starting, the impeller is driven by the shaft to rotate at high speed, and the liquid between the vanes must also rotate with it. Under the action of centrifugal force, the liquid from the center of the impeller is thrown to the outer edge and get energy to leave the outer edge of the impeller at a high speed into the worm-shaped pump casing.

    In the worm shell, the liquid due to the gradual expansion of the flow path and deceleration, and part of the kinetic energy into static pressure energy, and finally to a higher pressure into the discharge pipe, sent to the place where it is needed. Liquid from the center of the impeller to the outer edge of the flow, in the center of the impeller to form a certain vacuum, due to the reservoir above the liquid surface of the pressure is greater than the pressure of the pump inlet, the liquid will be pressed into the impeller continuously. It can be seen that as long as the impeller is constantly rotating, the liquid will be continuously sucked in and discharged.

    Starting of other centrifugal pumps

    The above are centrifugal pumps, for other types of pumps, the situation is as follows.

    1, axial flow pump large flow startup characteristics - full open valve startup

    Axial pumps in zero-flow conditions when the shaft power is the largest, 140% to 200% of the rated shaft power, the maximum flow rate when the power is the smallest, so in order to minimize the start-up current, the start-up characteristics of the shaft power should be a large flow rate to start (i.e., fully open valve start).

    2, mixed flow pump startup characteristics - full open valve startup

    Mixed flow pump in zero-flow conditions when the shaft power between the above two pumps, for the rated power of 100% to 130%, so the mixed flow pump startup characteristics should also be between the above two pumps, the best fully open-valve start.

    3、Starting characteristics of the vortex pump--Full open valve startup

    Vortex pump in zero-flow conditions when the maximum shaft power, 130% to 190% of the rated shaft power, so similar to the axial pump, vortex pump start-up characteristics should be a large flow start (i.e., fully open valve start).