DescriptionFeaturesDetailsHow It Works360° Service and maintenance videosDocumentation



Alfa Laval’s SRU rotary lobe positive displacement pump features a smooth, low shear pumping action. The SRU is Alfa Laval’s core rotary lobe pump for the gentle handling of sensitive process fluids.

This EHEDG-approved pump handles both clean-in-place (CIP) and sterilization-in-place (SIP), and can be supplied with thorough documentation to support rigorous validation requirements. The advanced Hyclean™ seal technology of the SRU series combines versatility with easy maintenance.

Related Industries:

Processed Foods, High-Acid Foods, Dairy, Beverages, Brewery, Home & Personal Care, Pharmaceutical, Biotech, Chemical


  • SRU1
  • SRU4
  • SRU2
  • SRU5
  • SRU3
  • SRU6

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.


The SRU range of rotary lobe pumps has been designed for use on a wide range of applications within the brewing, dairy, food, pharmaceutical, and chemical industries. The SRU pump can handle low to high viscosity media, is suitable for CIP and SIP, and conforms to 3-A sanitary standards. The characteristic smooth, low-shear pumping action is ideal for products such as creams, gels, emulsions, aerated mixtures, delicate cells, and organic solids in suspension.

The SRU range is compact in size and highly efficient, capable of flow rates up to 466 gpm and pressures up to 290 psig. The new, improved modular design provides for greater application flexibility and cost-effective easy maintenance.


The SRU pump, with its conventional lobe pump design concept, has a robust cast iron gearbox, which provides maximum shaft rigidity and easy oil seal replacement. The SRU range in series 1 – 4 has a universal gearbox design. This offers flexibility when mounting pumps, allowing the inlet and outlet ports to be in either a vertical or horizontal plane by changing the foot position. The SRU range in series 5 & 6 has dedicated gearbox castings, which also allows the inlet and outlet ports to be in either the vertical or horizontal plane. A quality epoxy paint system is used on the gearbox exterior for optimum protection against natural and corrosive elements.


The SRU, in standard specification, has sanitary design full-bore inlet and outlet ports to International Standards, maximizing inlet and outlet port efficiency and NPSH characteristics. Enlarged diameter and rectangular ports are also available to handle very high viscosity products.

The SRU, in standard specification, has tri-lobe rotors with the option of bi-lobe rotors for handling fluids containing large delicate solids. All rotors are available in three temperature ratings allowing the pump to be operated at maximum process temperatures of 158°F, 266°F, and 392°F for both fluid-pumped and CIP.


To correctly size a rotary lobe pump some essential information is required. Provision of the information listed below enables our customer support personnel to determine the optimum pump selection:

  • Fluid to be pumped
  • Viscosity
  • SG/Density
  • Pumping temperature — minimum, normal, and maximum
  • CIP temperature(s) — minimum, normal, and maximum

The positive displacement of the SRU pump is provided by non-contacting, contra-rotating tri-lobe or bi-lobe rotors within a fully swept pump chamber. All SRU pumps are capable of bi-rotational flow without modification.

Pump Gearbox High quality grey cast iron
Pumphead Product wetted components in 316L and 329L
Product Wetted Elastomers USP Class VI EPDM, NBR, FPM all FDA conforming. Also PTFE for chemical applications.
Pump Model Max Size of Spherical Solids – Bi-lobe Rotors(in) Max Size of Spherical Solids – Tri-lobe Rotors(in)
SRU1N 0.31 0.24
SRU1W 0.31 0.24
SRU2N 0.31 0.24
SRU2W 0.51 0.35
SRU3N 0.51 0.35
SRU3W 0.63 0.43
SRU4N 0.63 0.43
SRU4W 0.87 0.59
SRU5N 0.87 0.59
SRU5W 1.06 0.71
SRU6N 1.06 0.71
SRU6W 1.46 0.94
Pump Model Bare Shaft Pump – Horizontal Porting(lbs) Bare Shaft Pump – Vertical Porting(lbs)
SRU1N 33 35
SRU1W 37 40
SRU2N 62 66
SRU2W 64 68
SRU3N 117 123
SRU3W 123 130
SRU4N 231 245
SRU4W 243 256
SRU5N 335 335
SRU5W 353 353
SRU6N 573 573
SRU6W 584 584


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.

SRU - How it works

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.

Alfa Laval SRU rotary lobe pumps – Dismantle, Seals and Fittings