Pumps in the dairy industry are specialised machines used to transfer fluids like raw milk, cream, and whey through various stages of processing and cleaning. Their primary function is to move liquid products gently while maintaining strict hygiene standards to prevent bacterial contamination and preserve product integrity. By converting mechanical energy into hydraulic energy, these pumps ensure a consistent flow across pasteurisers, separators, and filtration systems.
As a competent partner for plant engineers and system suppliers across Germany, we understand that selecting the right equipment is about more than just moving liquid. It is about maximising efficiency in dairy production and ensuring sustainable operations. Whether you are handling a low-viscosity fluid like skimmed milk or a thick cultured product like stabilised yoghurt, the mechanical design of the pump determines your process uptime and energy consumption.
How pumps work in dairy processing
Pumping in a dairy environment follows specific physical principles depending on whether the pump is rotodynamic or positive displacement. The process generally follows these stages:
- Induction: Fluid enters the pump inlet port. In a centrifugal pump, it is directed to the impeller eye. In a positive displacement pump, the movement of rotors creates a partial vacuum that allows atmospheric pressure to force the fluid into the chamber.
- Energy Transfer: For centrifugal pumps for dairy plants, rotating vanes transfer mechanical work to the fluid, increasing its velocity and pressure via centrifugal force. In positive displacement models, the fluid is trapped in discrete volumes between rotors or screws.
- Displacement: The fluid is directed towards the outlet. Centrifugal force presses the liquid against the pump casing, while positive displacement rotors mesh to diminish the cavity size, forcing the liquid into the discharge line.
Key components of sanitary dairy pumps
Dairy pumps must be constructed from materials that possess product integrity, meaning they are resistant to both the media being pumped and the chemicals used in cleaning cycles.
Impellers and Rotors
In centrifugal models, we typically utilise semi-open impellers. This design allows for visual inspection of the vanes and makes the component easy to clean and polish. In positive displacement pumps, rotors can take various forms, such as Tri-lobe or Bi-piston configurations, often made from non-galling alloys to allow for the close clearances required for high volumetric efficiency.
The mechanical seal
The shaft seal is often considered the most critical part of the pump. Dairy applications frequently use single mechanical seals for standard products like milk. However, for products that crystallise—such as sugar-heavy concentrates—or for abrasive media, flushed or double mechanical seals are used to provide a liquid barrier and prevent 'dry' running.
Pump casing and back plate
The pump casing and back plate form the actual fluid chamber. For dairy use, these are manufactured from rigid stainless steel, such as AISI 316L, which provides superior resistance to corrosion and pitting. The casing is often designed with 360° flexibility, allowing the outlet to be positioned for optimal pipework alignment.
Elastomers
Static and dynamic seals utilise elastomers like EPDM or FPM (Viton). These must be FDA and 3-A conforming to ensure they are safe for food contact. EPDM is particularly valued in dairies for its resistance to the tough alkaline and acidic detergents used in Clean-In-Place (CIP) cycles.
Pump types and their dairy use cases
Different dairy products exhibit unique rheological behaviours, necessitating different pump technologies.
| Pump Type | Suited For | Dairy Example |
|---|---|---|
| Centrifugal | Low viscosity | Raw milk transfer |
| Self-Priming | Air-mixed fluids | CIP return duties |
| Rotary Lobe | Delicate solids | Fruit-filled yoghurt |
| Twin Screw | Universal duty | Concentrate & CIP |
Centrifugal pumps
Standard duty centrifugal pumps are the workhorses of the dairy plant. They are ideal for low-viscosity Newtonian fluids. A real-world audit showed that replacing inefficient models with high-efficiency Alfa Laval LKH pumps can result in 20% energy savings and a significant reduction in maintenance costs (Alfa Laval Case Story).
Self-priming pumps
In applications like tank emptying or CIP return, liquid often contains entrained air. Specialised pumps like the LKH Prime use an airscrew technology to remove gas from the suction pipe, ensuring the pump does not lose its prime during phase changes.
Positive displacement pumps
For viscous products like cream or butter, positive displacement pumps are essential. These create constant torque and handle shear-sensitive media gently. The DuraCirc range, for instance, offers high volumetric efficiency and is certified to EHEDG and 3-A standards, ensuring it can be cleaned effectively via CIP.
Twin screw pumps
The Twin Screw pump, such as the OS range, is highly versatile, capable of handling both high-viscosity product transfer and the high speeds required for CIP fluids. This 'two-in-one' operation can reduce the total number of pumps needed in a process line.
Applications across the dairy line
Modern dairy processing requires efficiency at every step, from the balance tank to final packaging.
- Pasteurisation: Centrifugal pumps transfer raw milk to plate heat exchangers. Efficiency here is paramount; implementing accessories like biofilm-reducing upgrades can increase uptime by 50% between cleanings (Alfa Laval Sustainability Story).
- Separation: Centrifugal pumps are often used to feed separators, where milk is split into cream and skimmed milk. High-inlet pressure variants like the LKHI are suitable for these demanding stages.
- Evaporation and Filtration: Filtration processes, such as whey concentration, require pumps that handle high solids. The LKH Evap range features a ClearFlow impeller to prevent protein build-up, extending production time between cleanings.
- Cleaning (CIP): Pumps must handle the circulation of hot caustic and acid washes. A typical cycle involves a pre-rinse, an alkaline wash at 70°C to 95°C to remove fats, followed by an acid wash to remove mineral salts and lime.
Selecting the right pump for your facility
Choosing a pump requires balancing initial capital costs against long-term operational savings. We recommend evaluating the following factors:
- Viscosity and Rheology: Does the fluid's viscosity change with shear? Milk is Newtonian, but yoghurt is often Pseudoplastic, requiring lower speeds to maintain cell structure.
- Net Positive Suction Head (NPSH): You must ensure the NPSH Available (NPSHa) in your system is higher than the NPSH Required (NPSHr) by the pump to avoid cavitation.
- Temperature: Viscosity generally increases as temperature falls. Always calculate your pump size based on the specific pumping temperature.
- Compliance: For dairy safety, ensure the pump meets 3-A or EHEDG standards. This guarantees that the internal surfaces are cleanable and the materials are safe for food contact.
- Sustainability Targets: Efficient pumps reduce CO2 emissions. Upgrading to energy-efficient models can reduce carbon emissions by over 200 tonnes per year in large-scale filtration applications (Alfa Laval Case Story).
Summary and next steps
The success of your dairy processing line depends on reliable, hygienic, and efficient fluid handling. By understanding the differences between centrifugal and positive displacement technologies and strictly adhering to sanitary construction standards, you can optimise your productivity and reduce waste. We support plant managers and engineers in selecting and designing systems tailored to these requirements.
As an Alfa Laval Master Distributor, Euroflow GmbH provides the expertise needed to navigate these technical decisions. Whether you are replacing a single unit or designing a complete filtration line, our team can assist with pump selection and process optimisation to ensure your facility reaches its sustainability and production goals.
