What Is a Multistage Pump?

Posted on Oct 20, 2020

Multistage pump

A multistage pump, also known as a multistage centrifugal pump, is a device that is used to give high pressure to the liquid that flows through it, in order to provide sufficient power to the flowing of the liquid. The multistage pump can be applied to a variety of places, which is often seen in industrial, agricultural, or daily application.

For the industrial aspect, the multistage pump can be used in power plants, for example. The power plants convert the liquids that they use to the electric power, which is relatively environmentally-friendly comparing to other methods. As for the application in agriculture, the multistage pump can be used in the irrigation of the large area of farmland.

The farmland receive irrigation by the standardized water supply by the operating of multistage pump, which not only provides irrigation evenly to the farmland but also saves the time that the farmers work manually. When it comes to daily usage, the multistage pump is commonly used in fire-fighting operations. When there is fire on a tall building, the fire fighter will hold a sprinkler that delivers water to put out the fire. Since the channel of the water supply is extended to the long length, the high pressure that gives to the water is required, and that’s why the fire-fighting operations use multistage pumps to work.


How Does a Multistage Pump Form?

A multistage pump consists of several parts that makes it an effective device to provide pressure to the liquids that pass through it. Look at the multistage pump in a cross-section, there is a suction inlet above the stages. Under the suction inlet is a pump casing, which is around the pump shaft and is non-rotating. Between the pump casing and the pump shaft, there is a mechanical seal.

Move to the right section of the pump shaft, there are two or more stages that are set in a row, and each stage is made up by an impeller and a diffuser. on the right end of the stages, there is a discharge pipe that delivers the liquids out of the multistage pump. Here we will look deeply into the formation of a multistage pump.

  • Suction Inlet
    The suction inlet is the entry of the liquids, and is set vertically on the left side of the pump, so the direction of the coming of the liquids is downward. The end of the suction inlet would be fed into the eye of the first impeller, where the liquids are delivered through.
  • Impellers and Diffusers
    One impeller and one diffuser make a stage of the pump, and a multistage pump comprises two or more stages. An impeller is equipped with vanes or blades that makes flow deflection, which produce mechanical power to the delivering of the liquids. A diffuser is stationary and wrapped around the outside of an impeller, and is a component that lowers down the flow velocity and increases the static pressure in order to provide force that is strong enough to push the liquids out. These two components should be worked together to make the optimal effectiveness of a multistage pump.
  • Mechanical Seal
    The mechanical seal of a multistage pump is set between the pump casing and the pump shaft. It seals the rotating shaft so as to prevent the liquids inside from leaking to the atmosphere or block the air from the outside to enter the pump casing, which may influence the operating of the multistage pump. It seems to be a tiny component of the multistage pump, but it plays a quite important role in the operating of the multistage pump.
  • Ball Bearing
    The ball bearing is on the left end of the pump shaft, which is used to keep the shaft in correct alignment with the stationary parts under the operating of the pump. Since the pump shaft keeps rotating during the procedure of operating the multistage pump, it should be hold in place by the ball bearing in conjunction with the mechanical shaft, in order to reduce the failure in the delivering of the liquids. Therefore, the ball bearing is also a critical role in the setup of the multistage pump.
  • Discharge Pipe
    The discharge pipe is set beside the last stage, on the right end of the multistage pump, and is the exit of the liquids. When a liquid pass through the multiple stages, it would come out upward from the discharge pipe, and compete the procedure.

How Does a Multistage Pump Work?

The direction of the delivering of liquids is from left to right horizontally. First, the liquid would enter the suction inlet, and go down through the eye of the impeller. Then the liquid would be pushed by the rotating of the pump shaft, and the ball bearing holds the pump shaft to keep it from deflecting, with the mechanical shaft block the leakage of the liquid or the entry of the air.

When the liquid passes through the first impeller, the impeller vanes offer higher level of power to push the liquid, and the diffuser inside controls the flow velocity and gives pressure to the liquid at the same time, in order to make the flow strong enough to deliver the liquid. This process would be repeated several times as much as the numbers of the stages. Once the liquid passes through the last stage, it would be discharged upwards from the discharge pipe, then the whole procedure is finished.

:: Read more : You Will Be Surprised at How a Multistage Centrifugal Pump Can Help


What Types of Multistage Pumps Are There?

Depending on the different formation of the multistage pumps, they can be divided into two main types, including the barrel multistage pumps and the ring section multistage pumps.

  • Barrel Multistage Pumps
    The barrel multistage pump is used for high-temperature and high-pressure applications, and usually appears as smaller pieces. A barrel multistage pump would be enclosed by a casing which looks like a barrel, and it allows for the internals of the pump to be removed without disconnecting the casing outside of them, which is relatively easy to maintain when it is not used.
  • Ring Section Multistage Pumps
    A ring section multistage pump is relatively bigger pieces, since it allows for more stages to be added or removed. The multiple stages are arranged in tandem inside the casing. When the liquid passes through each stage, the pressure that is given to the liquid would increases, and reaches the highest pressure until the last stage. However, when adding or removing the internals of the ring section multistage pump, the outer casing and piping must be removed, which takes more time and work when being maintained.

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