The case for peristaltic pumps

Every fluid has different handling requirements and some are easier to handle than others, but operational and maintenance issues can ease with the right type of pump. While one solution may not fit all pump applications, comparing the type of pump in use with a peristaltic pump is a place to start

Peristaltic pumps are easy to clean and maintain

Every fluid has different handling requirements and some are easier to handle than others. Cole-Parmer’s Beth Dumey and Jaime Robles look at how operational and maintenance issues can ease with the right type of pump

In real-world conditions, pumps can be challenging: some do not handle particulates; some are difficult to use with high-viscosity materials; others have valves that stick and seals that fail – all common complaints for everyday pump users. Maintenance issues, such as cleaning and replacing parts, which result in costly downtime, can be added to this list.

While one solution may not fit all pump applications, comparing the type of pump in use with a peristaltic pump is a place to start. A peristaltic pump works by an alternating pattern of squeezing and releasing flexible tubing to move fluid through the pump. As a roller passes over the tubing, it is first occluded (squeezed) then released.

The progression of this squeezed area forces fluid to move in front of the roller. The tubing behind the rollers recovers its shape, creating a vacuum and drawing fluid in behind it. As the roller moves faster, vacuum pockets are created more quickly and the fluid moving through the system picks up speed. The rollers act as check valves to prevent siphoning or loss of prime.

Diagram showing the workings of a peristaltic pump

The following application examples illustrate some specific advantages of peristaltic pumps.

Chemical processing applications:

International company HEL specialises in process safety and development and provides pre-pilot scale chemical reactors and systems to the pharmaceutical, fine chemical and petrochemical industries and academia.

HEL’s project team prepared three automated reactor systems for a process chemistry application in which the client required phase separation. The client needed an automated system and HEL project leaders turned to Cole-Parmer for help in outfitting the system with the correct pumping technology.

Chemical reactor systems require a pump system that can deliver an accurate volume of fluid while maintaining purity. Cole-Parmer recommended its Masterflex peristaltic pump for this application. This range of robust pumps offers high accuracy. Additionally, the only wetted part is the pump’s tubing, ensuring high purity.

‘The wide variety of Masterflex tubing formulations includes chemically compatible tubing that meets EP, USP, FDA, 3A and NSF approvals. Replacing the tubing is very easy and quick, simplifying clean-down processes and avoiding cross-contamination,’ says Colin Heathfield, Cole-Parmer technical sales manager and fluid handling specialist.

The drives are available in analogue, digital, or command protocol control options, enabling easy integration into HEL’s enterprise library software (ELS) control software.

Each HEL application requires a customised approach, as well as good understanding of the customer’s requirements. In this case, after discussing the options with a Cole-Parmer technical expert, HEL selected a Masterflex L/S Precision Standard pump system with Easy-Load II Pump Head, ideally suited to metering, feed and transfer applications, together with Masterflex Chem-Durance Bio Tubing.

The advantages of this system are that it is simple to integrate with control software; easy to make tubing changes; there is a wide range of compliant tubes and fittings; there is no cross-contamination; it can pump shear-sensitive media; and produces stable flow rates when handling solids.

An example of the Masterflex line of peristaltic pumps for a variety of markets – from lab applications to manufacturing

Lab applications:

A research laboratory needs to pump dilute sulfuric acid and a copper sulfate solution 24 hours a day for five days in a row. Technicians need to recirculate these two chemicals at 60ºC for a cell lab. In addition, they need to be able to vary the flow rate with a maximum flow of 15 litres/minute at 15psi.

Initially, a flexible impeller pump might make sense for its durability, material handling flexibility and positive displacement features. Yet the flexible impeller pump cannot handle higher pressures at higher flow rates well. Variable flow control is difficult, as is finding chemically compatible internal pump parts. The pump is hard to clean and it cannot run dry.

When compared with a peristaltic pump, the flexible impeller pump is less beneficial. The peristaltic pump handles higher pressures at higher flow rates. Variable-speed pump drives make it easy to control flow. Once again, chemically compatible tubing is available, and the pump can run dry.

What a peristaltic pump can do
While they are not the perfect solution for every scenario, peristaltic pumps rank highly in terms of being low maintenance and simple to operate. Their advantages can be summarised as follows:
Particulate handlingPeristaltic pumps can handle undissolved solids and dirty fluids containing particulates. For manufacturing and industrial applications, they can pump wastewater, suspended solids, harsh chemicals, and more
High viscositiesThe design of peristaltic pumps makes them suitable for abrasive and/or viscous fluids such as lubricants, slurries, paints, liquid waste and more
Maintenance of sterilityBecause the fluid that is pumped does not come into contact with the internal pump parts, the fluid is not contaminated and the parts remain clog-free. Simply using sterilised tubing and other fluid path components will maintain fluid sterility
Chemical compatibilityThe composition of the tubing used in the pump is the key factor in chemical compatibility. Hundreds of tubing options are available and free databases (such as ColeParmer.com/Chemical-Resistance) allow users to compare tubing materials to assess their compatibility with a chosen chemical
Ability to run dryPumps gases, liquids or mixed phases without damaging the pump
Ease of useMost peristaltic pumps can be installed within minutes. Their interfaces are easy to use and those with digital displays can be read from across an average-sized room. Some have reversible motors to purge tubing and some have remote control capabilities
Reduced maintenanceWith no seals, valves or glands, these pumps are easier to maintain. Tubing is easy to replace and requires few or no tools; simply switch the old tubing with new tubing. Some tubing is formulated for longer life, which further reduces costs. Actual tubing life depends on pump speed and pressure, tubing material, chemical compatibility and the abrasiveness of the media being pumped

Handling viscous materials:

A manufacturer needs to pump 100% glycerol from a 55-gallon drum into six smaller containers. Once these six containers are filled with glycerol, the chemical is used to lubricate needles for the manufacturer’s process.

A solenoid diaphragm pump may seem like a valid choice as a typical metering pump, but it does not work well with high viscosities. The flow of this pump would be significantly reduced due to the 1400-cp viscosity of glycerol. The solenoid diaphragm pump is also difficult to clean and has numerous replacement parts, including diaphragms and internal valves. Finally, the check valves may stick, rendering the pump inoperable.

Instead, the peristaltic pump handles high viscosities well and would improve the manufacturer’s flow rate. Because the fluid in a peristaltic pump does not come in contact with internal pump parts – it is in contact only with the tubing – the pump remains clean and free of residue. Tubing is easily replaced, reducing overall maintenance time, and the pump has excellent self-priming capabilities.

Manufacturers can choose from an array of pump options, from gear pumps to drum pumps to air-operated double diaphragm pumps to centrifugal pumps, and more. Yet, when discerning between these options, the deciding factor should be functionality that complements, not impedes, the production process. When weighing precision, versatility and ease of use, a peristaltic pump often performs best.

When is a peristaltic pump not the answer? With the pulsating nature of the peristaltic pump, applications that require a consistently smooth flow may be better served by a centrifugal or gear pump. In many cases, however, peristaltic pumps provide significant advantages that enhance production.

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