Posted on Jul 22, 2020

Multistage centrifugal pump

Multistage centrifugal pumps are designed with two or more impellers. Depending on the make and configuration, the rotors can be mounted on the same or different shafts. If high discharge pressures are required, the rotors can also be connected in series, while in the case of high capacity they are usually connected in parallel.

Multistage centrifugal pumps are used to create high pressure on a common shaft in the same housing is more economical than a pump with only one impeller. As part of the pump design, the channels in the pump housing operate by directing the discharge of one impeller to suck the other.

Water enters the pump and then passes through a series of rotors in series, going from left to right. From there, water flows from the spiral surrounding the spiral of one rotor to suck the next rotor. Most of these types of pumps are single-stage. A multi-stage centrifugal pump is many times better.

In some multistage centrifugal pumps, axial pressure forces are balanced by so-called balancing blades located at the rear of the impellers. The remaining forces are then absorbed by the angular ball bearing on the drive side and the heavy duty ball bearing on the drive side.

Multistage centrifugal pump with two outer bearings, a seal pressure balancing line is provided that releases pressure from the seal area on the discharge side back to the pump suction side. Thanks to this unique design function, more economical seals can be used, even when the pump is operating under high pressure.

The pumps are sold in various sizes, again based on budget, but also application and volume. For heating plants, water pipelines, fire-fighting operations, irrigation, agriculture, autoclaves, boiler feed, hydrocarbons and handling lightly soiled but also clean liquids, a smaller pump would suffice.

Multistage centrifugal pumps are one of the most popular types of pumps in recent years. Their ability to provide engineers with a flexible flow range and lifting height, as well as their high degree of energy efficiency, makes them an excellent choice for many applications. Can they be appropriate for yours?

:: Read more : A Brief Introduction: What Is An Industrial Pump? 

How centrifugal pumps work: Single-Stage vs. Multi-Stage

The more stages the pump has, the higher the outlet discharge pressure is. These pumps have the unique ability to generate ever higher pressures after adding each stage, but the flow range always remains constant at a given speed. Each stage consists of a rotor, diffuser and directional return blades (usually in combination with a diffuser), which are all in one and the same stage housing.

The head of a single-stage centrifugal pump is largely governed by the type of impeller and the circumferential speed. If the rotational speed cannot be increased due to other operating conditions and a larger impeller diameter would lead to very low specific speeds resulting in uneconomical efficiencies, fitting several stages in series (also see Series operation) can be an economic option of increasing the head. If the number of stages is altered at unchanged dimensions and speeds, the flow rate of such a multistage pump remains constant while the power input and head increase proportionally to the number of stages.​

Multi-stage pumps are defined as pumps in which fluid flows through several impellers connected in series. Multistage centrifugal pumps have many fluid chambers (or stages) that are connected in series. The fluid enters the first chamber under pressure in the suction line and drops at a certain elevated pressure. After leaving the first stage, the fluid goes to the second stage, in which the pressure is further increased.

Multi-stage pumps are an economical way to cover higher pressure ranges in the pump series selection charts. Another advantage is that multi-stage pumps can be easily slid down the stage or that mannequins can be used for future pressure increases. The disadvantage of a very large number of stages is the increasing sensitivity of the pump rotor to external or natural vibrations.

An example of a pump with several stage casings of the same type fitted in tandem arrangement is the ring-section pump. This type of pump is often used in power station applications, e.g. as a boiler feed pump and in industrial applications requiring high pressures.

The individual stages of a multistage pump do not necessarily have to be arranged in tandem.  The balancing of axial thrust can be enhanced by arranging the stages back to back in pairs or groups (see Back-to-back impeller pump). A typical example would be the pipeline pump.The individual stages of a multi-stage pump need not necessarily be arranged in tandem. Axial thrust balancing can be improved by setting the steps back to back in pairs or groups (see Rotor pump back to back). A typical example would be a pipeline pump.

Regardless of the number of stages, the inlet housing with the radial or axial inlet nozzle is positioned before the first stage, and the last stage is located in the outlet housing containing the balancing device and the shaft seal. Only the common pump shaft, tie rods and base plate must be adjusted to accommodate the required number of steps.

:: Read more : What Is A Commercial Pump And What’s its benefits

Horizontal and Vertical multistage centrifugal pumps: There are several different types of multistage pumps. Those with horizontal shaft and those with vertical shaft.

Horizontal multistage centrifugal pumps

This type of pump has a segmented housing with modular interstages. The swivel assembly is held between the bearing housings, making the assembly more balanced for high pressures. They usually support higher flow rates than vertical multi-stage pumps (except for vertical turbine pumps).

The horizontal configuration of multi-stage pumps is best used in such applications:

● Reverse Osmosis
● Boiler Feed
● Shower
● Spray
● Cogeneration
● Pressure Boosting
● High Pressure Cleaning
● Snow making
● Condensate
● Mine dewatering

This type of pump, however, requires quite maintenance. Working with these pumps requires a large set of skills and making sure that they are properly assembled. They can also be quite expensive in advance, depending on the degree of specification required and the construction materials.

Vertical multistage centrifugal pumps

Vertical multistage centrifugal pumps have a vertical shaft in which the stages are stacked on top of each other. Although vertical turbines are technically multi-stage pumps, they are not the types of pumps we are discussing here.

In these pumps, the intervals are small, which is why the best for this pump are applications for clean water:

● High pressure shower systems
● Boiler feedwater
● Desuperheater feed

Vertical multistage pumps are ideal for areas where there is not much space to lose. Its ability to deliver high pressure through one pump body and motor kit is also a plus.

However, it should be remembered that this type of pump does not tolerate dirt and significant solids, and is also susceptible to deadlock conditions.

Multi-stage pumps provide many key benefits, from energy savings to the ability to work in a wide range of flow / height scenarios. If you think this may be appropriate for your application, first consult a qualified engineer. They will make sure that the right pump is selected especially for your purposes

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