Centrifugal pumps are available in a broad range of configurations. Each type is engineered for a specific set of process conditions. The following overview covers the main variations found in hygienic and industrial applications.

Standard centrifugal pump (LKH Range)

The Alfa Laval LKH is a highly efficient centrifugal pump designed for hygienic, gentle product treatment and chemical resistance. It is available in thirteen sizes with flow rates up to 500 m³/h (at 50 Hz) and differential pressures up to 11.5 bar. The LKH suits demanding applications across dairy, food, beverage, home and personal care, and chemical industries. A real-world use case: raw milk transfer from a balance tank to a pasteuriser section.

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Evaporation centrifugal pump (LKH Evap)

The LKH Evap is tailored for evaporation-type applications — liquid concentration, powder processing, and equipment dewatering in the dairy, food, beverage, brewery, starch, and chemical industries. It features a low NPSHr design and an optional ClearFlow scraper impeller that prevents product build-up during high-solids operations, prolonging production time between cleaning cycles. Available in ten sizes with flow rates up to 280 m³/h.

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High inlet pressure centrifugal pump (LKHI)

The LKHI range handles inlet pressures up to 16 bar thanks to an internal shaft seal design. It is used downstream of high-pressure process stages, such as after heat exchangers or homogenisers. Available in nine sizes with flow rates up to 240 m³/h (50 Hz).

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Multi-stage centrifugal pump (LKH Multistage)

Multi-stage centrifugal pumps are used when high outlet pressure and low capacity are required — for example in reverse osmosis, ultrafiltration, and brewery applications. Two, three, or four impellers are mounted on the same shaft, each stage boosting pressure further. Discharge pressures reach up to 40 bar, with flow rates up to 75 m³/h at 50 Hz.

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High-pressure centrifugal pump (LKHPF)

The LKHPF is built with a reinforced pump casing and back plate for inlet pressures up to 40 bar. Application areas include reverse osmosis, mono-filtration, and ultrafiltration. Flow rates reach 280 m³/h at 50 Hz.

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Self-priming centrifugal pump (LKH Prime)

The LKH Prime combines centrifugal pump efficiency with self-priming capability. An airscrew in an offset priming chamber evacuates air from the suction line, making it suitable for tank emptying and CIP return applications where the suction line may not always be liquid-filled. The LKH Prime is designed for the food, dairy, beverage, and home-personal care industries. Available in three sizes with flow rates up to 280 m³/h.

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UltraPure centrifugal pump (LKH UltraPure)

Designed for high-purity applications in the biotechnology and pharmaceutical industries, the LKH UltraPure meets ASME BPE and GMP requirements. It is supplied with a complete Q-doc documentation package for material traceability and validation. A 45° casing outlet ensures self-venting, and improved surface finishes prevent biofilm build-up. Available in eight sizes with flow rates up to 280 m³/h.

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All-purpose centrifugal pump (SolidC)

The SolidC is an all-purpose centrifugal pump for less demanding duties — CIP solution transfer, utilities, cooling or heating water, and simple transport applications across dairy, food, beverage, and personal care. It is designed for CIP and available in four sizes with flow rates up to 75 m³/h and differential pressures up to 8 bar.

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Standard-duty centrifugal pumps (FM / GM)

The Alfa Laval FM and GM centrifugal pumps serve general-duty sanitary applications. They provide a reliable, compact option when advanced features such as high inlet pressure ratings or self-priming are not required.

Which centrifugal pump fits your process line? — selection criteria

Selecting the right centrifugal pump requires gathering two categories of data before any sizing begins: product/fluid data and performance data. Missing or inaccurate inputs lead to incorrect pump selection, premature seal failure, cavitation, or motor overload. Below are the key factors to evaluate.

1. Fluid viscosity

Centrifugal pumps are designed for viscosities up to 800 cP. Above this threshold, the pump's capacity, head, and efficiency drop whilst power consumption rises. If your product viscosity exceeds 800 cP at the pumping temperature, consider a positive displacement alternative.

2. Flow rate and head (pressure)

Define the required capacity in m³/h and the total system head in metres or bar. The total head accounts for static head differences, friction losses in pipework and fittings, pressure drops across heat exchangers or filters, and any vessel pressure on the discharge side. Use the pump's Q-H curve to confirm the duty point falls within an efficient operating range.

3. Temperature and vapour pressure

Temperature affects viscosity, density, elastomer compatibility, and — critically — vapour pressure. A high pumping temperature raises vapour pressure, which reduces the Net Positive Suction Head available (NPSHa) and increases the risk of cavitation. Always calculate NPSHa at the highest expected temperature and verify that it exceeds the pump's NPSHr.

4. NPSH — avoiding cavitation

NPSHa must be greater than NPSHr under all duty conditions. Factors that improve NPSHa include shorter and wider suction lines, higher static suction head, and lower fluid temperature. Cavitation damages impellers, seals, and pump casings and must be avoided.

5. Inlet pressure

Standard LKH pumps handle inlet pressures up to 10 bar. For higher inlet pressures, the LKHI (up to 16 bar) or the LKHPF (up to 40 bar) are the correct choice. Selecting a pump that cannot withstand the actual inlet pressure risks mechanical seal failure and damage.

6. CIP and SIP requirements

All Alfa Laval centrifugal pumps are designed for Clean-In-Place. If your process also requires Sterilisation-In-Place, confirm that the selected seal configuration and elastomer materials can handle the sterilisation temperature — typically around 145 °C in dairy applications.

7. Hygiene certifications

Determine whether your application requires 3-A, EHEDG, FDA, USP Class VI, or ASME BPE compliance. The LKH range conforms to 3-A; the LKH UltraPure and LKH Prime UltraPure additionally comply with ASME BPE and USP requirements.

8. Material compatibility

Product-wetted parts on Alfa Laval centrifugal pumps are AISI 316L (Werkstoff 1.4404). Elastomers are available in EPDM, FPM, PTFE, FFPM, and other grades — each suited to different fluid chemistries and temperatures. An elastomer compatibility guide helps match the right material to your product.

9. Motor and speed control

Centrifugal pumps are generally available with two-pole (3,000 rpm synchronous at 50 Hz) or four-pole (1,500 rpm) motors. A frequency converter allows stepless speed control to adjust the duty point, reduce energy consumption, and minimise pressure shocks during start-up and shutdown.

10. Self-priming requirement

Standard centrifugal pumps cannot evacuate air from the suction line. If your application involves tank emptying or CIP return where the pump may encounter air, specify the LKH Prime or LKH Prime UltraPure with their built-in airscrew priming capability.

What is a centrifugal pump — and how does it differ from a positive displacement pump?

To summarise: a centrifugal pump uses centrifugal force generated by a rotating impeller to transfer fluid. It belongs to the rotodynamic family of pumps, where rotating mechanical energy is converted into fluid velocity and pressure. This makes it fundamentally different from a positive displacement pump, which traps a fixed volume of fluid and pushes it from inlet to outlet with each revolution.

The practical consequences of this difference are significant for pump selection:

* The LKH Prime self-priming centrifugal pump is the exception — it can evacuate air from the suction line using its airscrew technology.

Choose a centrifugal pump when your fluid is thin (below 800 cP), the required flow rate is high, and gentle treatment with smooth, non-pulsating flow is desired. Choose a positive displacement pump — such as a rotary lobe, circumferential piston, or twin screw pump — when viscosity is high, the product contains delicate solids, or you need a flow rate that remains constant regardless of discharge pressure.

Understanding how a centrifugal pump works starts with the impeller — the rotating element at the heart of the pump. The process follows a clear sequence of energy conversions.

1. Fluid enters the impeller eye. Liquid flows axially into the centre of the impeller through the pump's inlet port. A flooded suction or sufficient Net Positive Suction Head (NPSHa) ensures the liquid reaches the impeller without cavitation.
2. The impeller accelerates the fluid. As the impeller rotates (typically at 1,450 or 2,900 rpm for 50 Hz motors), its vanes transfer mechanical energy to the fluid. The rotation forces the liquid outward along the impeller channels by centrifugal force, increasing both velocity and pressure.
3. The pump casing converts velocity into pressure. Once the fluid leaves the impeller periphery, it enters the volute-shaped pump casing. The expanding cross-section of the casing decelerates the fluid, converting kinetic energy (velocity) into static pressure before the fluid exits through the outlet.
4. Flow is continuous. Because the impeller spins without interruption, the centrifugal pump delivers steady, non-pulsating flow — a key advantage over positive displacement pumps for many low-viscosity applications.

In a multi-stage centrifugal pump, several impellers are mounted on the same shaft. Each stage further increases the pressure whilst the flow rate remains constant — effectively operating as multiple pumps connected in series within a single housing.

Key components of a centrifugal pump

A centrifugal pump is deliberately simple in construction. Fewer parts mean easier servicing, lower risk of contamination, and reliable long-term operation in hygienic environments. The following components define the pump's performance.

Impeller

The impeller is the only moving part inside the pump head. In Alfa Laval centrifugal pumps, the impeller is of cast, semi-open design — meaning the vanes are open at the front for easy visual inspection and thorough cleaning. Impeller diameter and width vary by model and determine the pump's head and flow characteristics. Product-wetted impellers are manufactured from AISI 316L stainless steel (Werkstoff 1.4404).

Pump casing

The pump casing is a rigid stainless steel housing with male screwed connections. It collects the high-velocity fluid leaving the impeller and converts that velocity into pressure. The casing is designed for multi-position outlet with 360° flexibility, allowing installation in almost any orientation.

Back plate

The back plate is a pressed steel component that, together with the pump casing, forms the fluid chamber. It seals the rear of the impeller area and houses the mechanical seal arrangement.

Mechanical seal

The connection between the pump shaft and the pump casing is sealed by a mechanical seal. Seal face combinations include carbon vs. stainless steel, carbon vs. silicon carbide, and silicon carbide vs. silicon carbide — selected based on fluid viscosity, temperature, and chemical compatibility. Seal types range from single and single flushed to double flushed configurations for hazardous or high-viscosity media.

Pump shaft and adaptor

Most centrifugal pumps use a stub shaft fixed to the motor shaft via a compression coupling — eliminating keyways and reducing vibration. The adaptor connects the motor to the back plate and can be attached to any standard IEC or NEMA frame electric motor.

Shroud and legs

An insulated shroud reduces noise and protects the motor. Adjustable legs allow precise levelling during installation and help ensure the pump meets hygienic clearance requirements.