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With its smooth, low-shear pumping action, the SRU is Alfa Laval’s core rotary lobe pump for the gentle handling of sensitive process fluids within the dairy, food and beverage, biotechnology and pharmaceutical industries.


Alfa Laval SRU rotary lobe pumps are carefully engineered to provide reliable performance, trouble-free operation and superior energy efficiency for demanding applications. It is an excellent choice for duties that require contamination-proof pumps to meet high standards of hygiene, low-shear and low-pulsation operation. This EHEDG-approved pump handles both Cleaning in Place and Sterilization in place, and can be supplied with thorough documentation to support rigorous validation requirements.

For even more demanding hygienic and ultra-clean duties, Alfa Laval offers the SX rotary lobe pump.

Consistent performance, minimal risk of contamination

SRU rotary lobe pumps are designed with features that maximize performance and minimize the risk of contamination. These include a defined compression front cover sealing, rotor nut retention design, drainable pump head and ultra-clean surface finishes.

Safeguarding product quality

Understanding of flow patterns is vital to ensure high efficiency fluid transfer with low pulsation, low shear and low noise characteristics. Alfa Laval employs Computational Fluid Dynamics (CFD) to establish exact geometry for the rotors and rotor case.

Greater flexibility and application fit

The modular design of the SRU provides greater flexibility to configure exactly the right solution for specific process requirements.

To meet different process requirements, the SRU features an R90 external shaft seal, which may be specified in various materials and configurations in order to ensure the correct shaft seal for the application. Alternatively the SRU can be fitted with Hyclean mechanical seals as well as other seal solutions.

In addition to a broad range of models and capacities available in horizontal or vertical porting, the SRU has a wide selection of options, including standard and custom seals, heating/cooling saddles and jackets, an integrated pressure relief valve and a rectangular inlet for pumping high viscosity fluids.

Robust construction – low maintenance

To deliver reliable operation and low maintenance the SRU features a robust gearbox construction with heavy-duty shafts, torque locking assemblies and taper roller bearings throughout.

Supply and delivery

The SRU range is available with twelve different pump head displacements, flow rates up to 106 m³/h, differential pressures up to 20 bar, temperatures up to 200°C and port sizes from 25 to 150 mm in diameter.

Certification, specification and standards

SRU rotary lobe pumps comply with EHEDG, 3-A, 3.1 and FDA hygienic standards and have ATEX approval for use in explosive environments. For more information, please consult the documentation provided.

                                            SRU - How it works

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How it works


Alfa Laval rotary lobe pumps are positive displacement pumps with rotor case, rotor case cover, rotors, rotor nuts, shafts, gearbox and shaft seals and elastomers, which are available in different materials. The pumps operate with no internal contacting parts in the pump head.

The SRU can be supplied either as a bare shaft pump or mounted on a base plate complete with coupling, guard, gear motor and shroud for easy plug-and-play installation.

The standard materials of construction are 316L stainless steel for all wetted parts and painted cast iron for the gearbox. Other materials are available on request.

Operating principle

A gear train in the pump gearbox drives the rotors and provides accurate synchronization, or timing, of the rotors. The contra-rotating propulsion system has two rotors spinning in opposite directions within the pump head. Fluid is carried through the pump in the cavities formed between the dwell of the rotor and the interior of the rotor case. The illustration (below) shows the displacement of fluid from pump inlet to outlet.  

 Rotary lobe pump - operating principle

The movement of the counter rotating rotors creates a partial vacuum that allows atmospheric pressure or other external pressures to force fluid into the pump chamber. As the rotors revolve, an expanding cavity forms, filling with fluid. As the blades disengage, each dwell forms a cavity. As the rotor blades engage, the cavity diminishes and fluid is, displaced into the outlet port.

Download the product models in Neutral or Native CAD file formats. It is also possible to download 3D PDF files.

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Part of a broad range of hygienic pumps

Alfa Laval offers a comprehensive range of pumps for use in hygienic applications. These include:

  •  LKH (Premium centrifugal pump)
  •  SolidC (Standard centrifugal pump)
  •  MR (Liquid ring and CIP return pump) 
  •  SX (Multi-lobe rotary lobe pump) 
  •  OptiLobe (Standard tri-lobe rotary pump)
  •  SCPP (Circumferential piston pump)

For the biotech and pharmaceutical industry:

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