This article centres on Valutech’s Rotary Lobe Pumps, providing an overview of the basic operating principles of rotary lobe pumps, as well as their design considerations and what features set apart Alfa Laval from competitor offerings. Rotary lobe pumps are widespread throughout a wide range of hygienic manufacturing industries, such as the cosmetics, pharmaceutical, biotechnology, food, beverage, and personal care industries due to their versatility and efficiency in handling a large breadth of fluid types commonly seen in these industries.
Operating Principles
Rotary lobe pumps are what are known as ‘positive displacement pumps’, and more specifically as ‘rotary positive displacement pumps’; this refers to their principle of moving fluids by trapping a fixed volume using continuously rotating components and physically pushing material through a system. The benefit of this positive displacement operating mechanism is that flow rates will be consistent regardless of discharge pressure, which is ideal for precise metering in cases where materials are expensive and/or must be used in very precise amounts in a manufacturing process. Rotary positive displacement pumps are adept at handling fluids of widely varying viscosities, boasting a notable advantage over other types of positive displacement pumps at higher viscosities while also having the ability to gently handle shear-sensitive or fragile solid-containing fluids without deterioration.
A rotary lobe pump, as stated in the name, uses rotating lobes to drive pumping action. As one lobe moves and leaves a cavity of specified volume in its place, this creates a suction action; at the same time, on the discharge side, a cavity contracts pushing out the same specified volume of fluid.
Design Considerations
Rotary lobe pumps can be specified in various different ways to suit the needs of a variety of processes and industries — below is a summary of design considerations when designing or selecting a rotary lobe pump for an industrial process:
Surface Finish
Industries such as the food, dairy, or pharmaceutical industries use may require electropolishing of the surface to Ra ≤ 0.5 µm to reduce bacterial buildup in the pump leading to product contamination.
Maximum Process Temperature and Pressure
Higher pressures or temperatures require reinforced casings, stronger shaft designs, and upgraded seals and elastomers to prevent leakage or damage.
Numbers of Lobes
Rotary lobe pumps typically have 2–4 lobes; pumps with fewer lobes are better at handling fragile solids with lower shear, while having more lobes provide smoother flow/less pulsation.
Port Orientation
Vertical port orientations aid in drainage of pump contents while horizontal ports are easier to align with product piping and are often more compact.
Heating Jackets
Heating jackets are used to maintain product viscosity, prevent crystallization (ex. in honey or fats), or maintain operating conditions for temperature-sensitive media or where freezing/blockage is a concern.
Elastomer & Stationary Face Materials | Shaft Seal Types
Seal materials (e.g. EPDM, FKM, PTFE) and face materials (e.g. carbon, silicon carbide) are selected based on chemical compatibility and process temperatures. Double mechanical seals or flushed seals may be required in place of single mechanical seals for abrasive/hazardous products.
Pressure Relief Valves
Integrated PRV’s protect the pump from over-pressurization in applications with blockage risks or higher viscosity fluids.
Valutech’s Offerings- Manufactured by Alfa Laval
OptiLobe
A cost-effective alternative for general applications — this pump is very flexible in its design and has a robust design, allowing it to meet a variety of process needs within its long lifespan. The OptiLobe is available with 10 different pump head displacements based on five gearbox modules and tri-lobe rotors in order to supply flow rates of 3.6- 77 m3/h. It is available with EPDM and FPM elastomeric seals, and can be specified up to a maximum process pressure of 8 bar and maximum process temperature of 130°C.
SRU
A mid-level variant for generic and more demanding applications — the SRU offers improved handling of sensitive fluids with smooth, low-shear pumping action for media such as gels, emulsions, and suspended-solid solutions of varying viscosities. It is available with 12 different pump head displacements based on six gearbox modules in order to supply flow rates of 3.2- 106 m3/h. It is available with a large range of elastomeric seals, including NBR, FPM, and USP Class VI EPDM, and can be specified up to a maximum process pressure of 20 bar and maximum process temperature of 200°C. The SRU can be specified in a complete range of port sizes and connections including DIN, ISO, and ASME (Tri-Clamp) and is available with tri-lobe and bi-lobe rotors.
SX
Alfa Laval’s premier rotary lobe offering, the SX is designed with improved pump head geometry and features multi-lobe (4 lobes) rotors to reduce shear and pulsation to optimal levels; it is the ultimate choice for maintaining product integrity of shear-sensitive and fragile solid-containing media. The SX is available with 14 different pump head displacements based on seven gearbox modules in order to supply flow rates of 3.6- 115 m3/h. It is available with EPDM, FPM, and Silicon elastomeric seals, and can be specified up to a maximum process pressure of 15 bar and maximum process temperature of 150°C.
Alfa Laval also offers the SX Ultra Pure model that uses the SX platform to offer a pump for industry applications adhering to the strictest possible sanitary regulations. The SX Ultra Pure offers the same process flow rates and maximum process conditions as the SX while being available with USP Class VI elastomers (EPDM, FPM, and Silicon) and a surface finish Ra ≤ 0.38 µm.