Alfa Laval SRU Rotary Lobe Pump

The SRU range of rotary lobe pumps has been designed for use on wide ranging applications within the Brewing, Dairy, Food, Pharmaceutical and Chemical industries. The SRU pump can handle from low to high viscosity media with its characteristic smooth, low shear pumping action being ideal for products such as creams, gels, emulsions, aerated mixtures, and delicate cells and organic solids in suspension. The SRU range is suitable for CIP (Cleaning In Place) and conforms to USA 3-A Hygienic Standard. In addition the SRU pump range is certified by EHEDG (European Hygienic Equipment Design Group) as fully CIP cleanable to their protocol.

The SRU pump range is also classified for use in potentially explosive atmospheres under the ATEX Directive 94/9/EC Group II, Categories 2 & 3, with temperature classification T1 to T4. The SRU range is compact in size and highly efficient, capable of flow rates up to 106 m³/h and pressures up to 20 bar. The modular design provides for greater application flexibility and cost effective maintenance. The SRU range is compact in size and highly efficient, capable of flow rates up to 106 m³/h and pressures up to 20 bar. The new improved modular design provides for greater application flexibility and cost effective easy maintenance.

Standard Design

Pump Gearbox

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 gives the flexibility of mounting pumps with the inlet and outlet ports in either a vertical or horizontal plane by changing the foot and its 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.

Pump head Construction

The SRU in standard specification has hygienic design full bore inlet and outlet ports to International Standards, maximising 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 70°C, 130°C and 200°C for both fluid pumped and CIP.

Maximum Solid Size Capability

Materials of Construction

Pump gearbox – high quality grey cast iron. Pumphead – product wetted components in 316L . Product wetted elastomers of EPDM, NBR, FPM all FDA conforming. Also PTFE for chemical applications.


Shaft Seal Options

  •  Single or single flush/quench. R90 or Hyclean type mechanical seals.
  •  Double R90 type mechanical seal for flush (steam barrier for aseptic application).
  •  Packed gland (unflushed or flushed versions).
    Note: EHEDG compliance only for Hyclean type mechanical seals.

Materials for Mechanical Seals

Carbon/Stainless steel, Tungsten Carbide/Tungsten Carbide, Silicon Carbide/Silicon Carbide or variations of these materials to suit fluid being pumped and/or application requirements. (N.B. Material variants are not available on all R90/Hyclean seal types)

Pump Sizing

In order to correctly size a rotary lobe pump some essential information is required. Provision of this information listed below enables our Technical Support personnel to obtain the optimum pump selection.

Product/Fluid Data

  •  Fluid to be pumped
  •  Viscosity
  •  SG/Density
  •  Pumping temperature, minimum, normal and maximum
  •  Cleaning in Place temperature(s), minimum, normal and maximum

Performance Data

  •  Flow rate, minimum, normal and maximum
  •  Discharge head/pressure (closest to pump outlet)
  •  Suction condition

Standard Specification Options

  •  Specification of inlet and outlet ports (Screwed male to BSP, DIN11851, Rdg, SMS. ISS/IDF, RJT, IAMD/3A, or Flanged to BS4504/DIN2533, ASA/ANSI 150, BS10E and other standards)
  •  Rotorcase Cover with integral Pressure Relief Valve.
  •  Heating/Cooling Saddle Jackets for Rotorcase and Jacket for Rotorcase Cover (not available when relief valve fitted).
  •  Bi-lobe Rotors in stainless steel and non-galling alloy.
  •  Electropolished product wetted components.
  •  Full material traceability on request to BS EN10204 3.1
  •  Electroless nickel plated gearbox.
  •  ATEX compliance.
  •  Complete pump unit comprising: Pump + Baseplate (mild or stainless steel) + coupling with guard + Geared electric motor suitable for (or supplied with) frequency speed control or manual variable speed drive (advise motor enclosure and electrical supply)

Working Principle

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.




Note 1. These pressure ratings may vary for pumps with certain threaded connections.


Horizontally ported
A1 denotes hygienic port dimension
A2 denotes enlarged port dimension

Vertically ported

A1 denotes hygienic port dimension
A2 denotes enlarged port dimension

Keeping you processing

For more information about our products and services please get in touch!

Internal Sales Manager

Call: 01777 712101