The term multistage refers to a centrifugal pump that has more than one impeller. A multistage pump is used when it is necessary or desirable to increase the pressure while maintaining or even increasing flow.
You might have heard the term “multistage centrifugal pumps” and wondered what it means. The word multistage is applied to the centrifugal pump when it is designed to have more than one impeller.
Multistage pumps are used for applications that require increased pressure, flow or head. These pumps are used in a wide range of industries including oil and gas drilling, water treatment and power generation.
This additional stage might be added to boost the pressure by using another centrifugal stage, or it might be added for other reasons such as for more flow or for more head.
A multistage pump is much like a centrifugal pump, but instead of just one impeller and casing, there are several impellers and casings. The first stage uses the lower-pressure water from the inlet side of the main pump to create high-pressure water that’s sent on to another casing where even higher pressures can be achieved.
The second reason, bypassing flow from one impeller to another is not recommended so we will discuss only the first case, boosting pressure.
The first case is called multistage centrifugal pump. The main purpose of this type of pump is to produce high pressure at low flow rate (HP). It means that we need a small amount of water with large pressure head and this can be achieved by using multiple impellers on a single shaft rotating in the casing or on individual shafts connected together inside a casing by balancing tubes.
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One of the most important things to understand about multistage centrifugal pumps is that adding a centrifugal stage means that the pressure has been increased, but at the cost of a reduction in flow because of the added friction loss through the extra impeller and casing.
When selecting your pump, it is important to consider how much pressure you actually require. If you have an existing system and need to increase your discharge pressure by 40 psig (2 bar), then one multistage pump will likely do the job just fine. However, if you need an additional 35 psig (2 bar) on top of what your existing system can provide—for example if you're building an addition onto your building—then two multistage pumps might be better suited for this task because they would give you more total head than one larger single stage model would provide.
Pressure boosting pumps are commonly multistage pumps. The first stage of the pump is designed to handle high-pressure fluids at a reduced volume, and it delivers this pre-pressurized fluid to a second stage that increases the pressure even further. This design allows for more efficient operation, as there is no need for an additional pump to boost pressure after the first stage has done its job.
Multistage centrifugal pumps are not limited to just using one suction and discharge ports. They can also be used in either direction (i.e., they can be "open" or "closed"). These two types of pumps are called open/closed loop systems:
In this article we discussed the advantages of using a multistage centrifugal pump and how it can be used to increase pressure. We also covered some of the disadvantages like pumping fluids with high viscosity or temperature, which are not suitable for multistage pumps. If you want to know more about this topic, check out our other articles on multistage pumps.