Centrifugal pump: Single-stage, double-suction type and other types
A Comprehensive Guide to Cost-Effective Centrifugal Pumps for Various Needs
A centrifugal pump is a type of mechanical equipment that uses centrifugal force to transport liquids. It belongs to the category of vane pumps. As a general-purpose machine, centrifugal pumps are indispensable flow delivery tools in modern industry, agriculture, municipal works, and daily life.
There are many types of pumps. Here, we will focus on centrifugal pumps, a subtype of vane pumps.
1: Horizontal Volute Pump — Single-Stage End-Suction Centrifugal Pump
One end of the pump shaft is supported by bearings inside the bearing bracket, and the other end extends outward, called the cantilever end, where the impeller is mounted. This type of pump structure is called a cantilever pump. It contains bearings and mechanical seals. The impeller usually has balance holes to balance axial thrust. For ease of maintenance, some cantilever pumps are designed with a back-opening structure so that the suction and discharge pipes do not need to be disassembled during inspection.
There is also a type that removes the bearing bracket and housing; the impeller is directly mounted on the extended motor shaft. This type is called a direct-coupled structure.
2: Horizontal Volute Pump — Single-Stage Self-Priming Centrifugal Pump
The self-priming centrifugal pump is a kind of volute single-stage centrifugal pump. One end of the shaft is supported by bearings inside a bracket. The self-priming pump can automatically draw liquid during startup. A reflux plate is installed at the pump inlet to retain a certain amount of liquid inside the pump (for initial use).
When starting, the liquid inside the pump mixes with some gas from the suction pipe, forming a gas-liquid mixture due to the high-speed rotation of the impeller. This mixture is sent to the separation chamber, where the gas separates and is expelled through the exhaust port. The separated liquid returns to the impeller via a reflux hole to mix with residual gas repeatedly until all gas is expelled. Once the gas is completely removed from the suction pipe, the pump switches to normal centrifugal pumping mode, continuously delivering liquid.
Due to many operating conditions and installation constraints, a self-priming centrifugal pump can be chosen.
Similarly, a direct-coupled structure type exists, where the impeller is directly mounted on an extended motor shaft, eliminating brackets and bearings.
3: Horizontal Volute Pump — Two-Stage Cantilever Pump
When the head provided by a single-stage end-suction cantilever pump is insufficient, a two-stage cantilever pump can be used. This pump is similar in structure to the single-stage cantilever pump but has two impellers, a discharge chamber, and a stage partition plate.
The two impellers are usually arranged back-to-back to balance axial thrust. However, two-stage cantilever pumps are relatively less common, as the centrifugal pump selection is broad.
4: Horizontal Volute Pump — Single-Stage Double-Suction Pump (Split Casing Pump)
Single-stage double-suction pumps are widely used for large flow applications. Essentially, two identical impellers are mounted back-to-back on one shaft, working in parallel. This design not only allows larger flow rates but also automatically balances axial thrust.
The double-suction pump typically adopts a semi-spiral suction chamber, and the pump casing is horizontally split (split casing pump). Bearings are installed on both sides of the pump, providing stable and reliable operation with easy maintenance. Opening the casing cover allows the entire rotor to be removed.
Flow rates typically range from 120 to 20,000 m³/h, and heads from 10 to 120 m.
5: Horizontal Volute Pump — Multi-Stage Double-Suction Pump (Multi-Stage Split Casing Pump)
The multi-stage double-suction split casing pump combines high head and large flow features in a highly efficient centrifugal pump. It uses a horizontal split casing structure, with liquid suction from both sides of the impeller, doubling the flow. Axial thrust is automatically balanced.
Multiple impellers are connected in series, progressively increasing head per stage. The casing splits along a horizontal plane, allowing internal maintenance (impeller, seal) without dismantling inlet/outlet piping.
It is widely used in high-pressure, large-flow conditions such as urban water supply, large water plants, boiler feedwater, crude oil transportation, refinery high-pressure water injection, power plant circulation systems, petrochemical fields, etc.
6: Horizontal Guide Vane Pump — Sectional Multi-Stage Centrifugal Pump
Sectional multi-stage pumps are widely used. Multiple impellers are mounted on one shaft in series, providing high head. Each impeller stage has its corresponding guide vane. The first stage is usually single-suction, but sometimes double-suction to improve cavitation performance.
To balance axial thrust, a balance disk is generally installed behind the last impeller stage. The entire rotor can shift slightly during operation, and the balance disk maintains the rotor in a balanced position.
Flow rate generally ranges from 20 to 700 m³/h, head from 100 to 650 m. High-pressure sectional pumps can reach pressures up to 28 MPa.
For high-temperature and high-pressure liquids, thermal expansion and cooling must be considered. This structure is used for high-pressure pumps, ultra-high-pressure pumps, boiler feedwater pumps, thermal oil pumps, etc.
Vertical Structures
7: Vertical Volute Pump — Vertical Single-Stage End-Suction Pump
Typically driven by a vertical motor mounted on a pump base, connected via a transmission shaft. The motor and rotor assembly are connected by a coupling. The rotor’s weight and axial thrust are supported by the thrust bearings of the vertical motor (usually angular contact rolling bearings).
The suction and discharge ports are on the same horizontal plane. This simple structure is easy to maintain and suitable for medium and small flow, low to medium head liquid delivery.
There is also a direct-coupled version where the impeller is directly mounted on an extended motor shaft, removing the coupling and bearing housing.
8: Vertical Volute Pump — Vertical Single-Stage Double-Suction Centrifugal Pump
This pump adopts a horizontal split casing structure with liquid suction from both sides of the impeller. The motor and pump are vertically mounted coaxially. Motor bearings (angular contact ball bearings or thrust bearings) handle all axial loads.
The double volute casing balances radial force and reduces vibration. The back-to-back double suction impellers plus vertical structure perfectly balance high flow, low cavitation, and space-saving requirements, making it the preferred choice in municipal and industrial large-flow applications.
9: Vertical Guide Vane Pump — Vertical Single-Stage Submersible Centrifugal Pump
Submersible pumps lift water from underground to the surface by immersing the motor and pump together in the water. The motor directly drives the impeller, saving the pump base, transmission shaft, and coupling, improving rotational speed and simplifying structure and cost.
Submersible pumps use wet motors (water-cooled), where water fills the space between rotor and stator. The motor windings are insulated with plastic-coated wire. A thrust bearing at the motor bottom supports the entire rotor weight.
10: Vertical Guide Vane Pump — Vertical Multi-Stage Centrifugal Pump
A high-efficiency, high-pressure pump consisting of multiple impellers in series for progressive pressure increase. Liquid enters the bottom impeller and flows through guide vanes to subsequent stages, converting kinetic energy into pressure energy. After multiple stages, high-pressure liquid exits the pump.
The pump features efficient hydraulic design with optimized impellers and guide vanes, reducing energy loss. Rotor components are dynamically balanced for low noise and vibration. Modular design allows internal parts replacement without dismantling pipes, ideal for high-rise building water supply, fire-fighting, boiler feedwater, and industrial boosting.
11: Vertical Guide Vane Pump — Vertical Multi-Stage Deep Well Pump
When water sources are underground or in deep wells, deep well pumps are used. These pumps are slender due to well diameter limits. They use wet or oil-immersed motors, with vertical motors driving impellers via a transmission shaft.
Multiple impellers and guide vanes in series increase head. The pump is submerged, and high-pressure water is pumped to the surface through discharge pipes. Deep well pumps feature high head, small diameter, high efficiency, and energy saving.
12: Vertical Guide Vane Pump — Vertical Multi-Stage Long Shaft Pump
The motor and pump are aligned vertically, connected by a long shaft (assembled in sections), which can reach tens of meters. Intermediate bearings reduce vibration. Multiple impellers in series achieve high pressure. The impeller is submerged below the liquid surface, preventing cavitation.
The motor drives the shaft via a flexible coupling. The shaft is supported by multiple radial bearings (usually water-lubricated rubber bearings, but can also use silicon carbide, graphite, bronze, ceramic, etc.). Axial thrust and rotor weight are supported by the pump thrust bearing. The discharge is located above the installation base.
Long shaft pumps are used in petrochemical, ports, offshore platforms, power plants, municipal engineering, steel, metallurgy, etc., pumping water, rainwater, mine water, sewage, and seawater under 55°C.
In conclusion, each type of water pump has its own advantages and disadvantages, which makes them suitable for different application scenarios. Whether you are planning a home renovation project, managing an industrial facility, or designing an irrigation system, understanding these common types of water pumps will help you make informed decisions and ensure optimal performance.
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