Lobe pumps are not good for metering duties because fluid slips between the lobes and the case. Watson-Marlow peristaltic pumps have a true positive displacement action – fluid is pushed in front of a tube pinched closed.
Lobe pumps are known for low shear pumping, but Watson-Marlow peristaltic pumps are even lower shear.
Lobe pumps are not good with abrasive fluids or with hard solids. These wear the lobes and can get trapped in the space between lobe and case, causing scoring. Worn or damaged lobes reduce flow rates through increased slip.
Lobe pumps have two shafts and so two sets of mechanical seals. These are expensive to maintain and the timing gears need careful resetting after maintenance to ensure lobes do not clash.
The fluid does not contact a Watson-Marlow peristaltic pump and vice versa, so abrasives are handled with ease; and one-minute maintenance is achieved with LoadSure tube elements.
For CIP applications, lobe pumps require by-pass pipework to divert some of the flow. Watson-Marlow 800 series peristaltic pumps have a full flow path through the tube for CIP duties. Installation costs are lower.
Lobe pumps are difficult to clean because of dead spots in the casing. Mechanical seals need swabbing to verify cleaning procedures have been effective.
Lobe pumps are not flexible and must be specifically designed for the application. Changing parameters can cause pumping problems. Temperature changes, for example, can result in "galling", where flakes of metal from the lobes are released into the fluid, causing contamination.
Watson-Marlow Bredel peristaltic pumps score on all counts:
- Accurate metering
- Low-shear pumping
- Good abrasive and hard solids handling
- No mechanical seals
- Low and simple maintenance
- Simple installation
- Flexible operation
Find out more about the Watson-Marlow range