The Case for Peristaltic Pumps

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. Add to this list: maintenance issues such as cleaning and replacing parts that result in costly downtime.

While one solution may not fit all pump applications, comparing the type of pump in use to a peristaltic pump is a good 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, creates a vacuum, and draws 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.

Consider:

A rubber manufacturer needs to dispense 1-mL doses of Methyl Ethyl Ketone (MEK) as a primer in the first step of the vulcanization process (treating rubber to give it certain properties). The manufacturer needs a pump that is easy to operate.

The tendency may be to get a piston pump for its relative accuracy when pumping small volumes. In this case, though, a piston pump makes it difficult to regulate the 1-mL doses. The chemical compatibility of the internal parts in the piston pump is challenging and the pump head and valves are hard to clean. Finally, the piston pump can’t run dry.

A peristaltic pump would be a better choice. Its controls are simple to operate, satisfying one of the key requirements of the manufacturer. Tubing formulations are available that are chemically compatible with MEK. The tubing is easy to change and cleaning the pump is also simple, reducing labor for operators. The pump has no service kits or valves to maintain. Peristaltic pumps can run dry to prime.

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. Plus, they need to be able to vary the flow rate with a maximum flow of 15 LPM at 15 psi.

Initially, a flexible impeller pump might make sense for its durability, material handling flexibility, and positive displacement features. Yet the flexible impeller pump can’t 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 to a peristaltic pump, the flexible impeller pump is less favorable. 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.

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 only contacts 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.

For industrial applications, 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.

Common applications which use peristaltic pumps include plating chemicals, manufacturing adhesives for cement,
dispensing glue emulsions, handling dyes in fabric manufacturing, monitoring pulp quality, transferring fluids between tanks, feeding etching chemicals for plate processors, developing caustic detergents, and many more.

What a Peristaltic Pump Can Do

While they are not the perfect solution for every scenario, peristaltic pumps rank high in low maintenance and simplicity of operation. Their advantages:

• Handle particulates: Peristaltic 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.
• Manage high viscosities: The design of peristaltic pumps makes them suitable for abrasive and/or viscous fluids such as lubricants, slurries, paints, liquid waste, and more.
• Maintain sterility: Because the fluid that is pumped does not come in contact with the internal pump parts, the fluid is not contaminated and the parts remain clog-free. Simply using sterilized tubing and other fluid path components will maintain fluid sterility.
• Offer chemical compatibility: The composition of the tubing used in the pump is the key factor in chemical compatibility. Hundreds of tubing options are available and free databases allow users to compare tubing materials to assess their compatibility with a chosen chemical.
• Can run dry: Pumps gases, liquids, or mixed phases without damaging the pump.
• Provide ease of use: Most 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.
• Reduce maintenance: With no seals, valves, or glands, these pumps are easier to maintain. Tubing is easy to replace with few or no tools needed; 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.

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, though, peristaltic pumps provide significant advantages that enhance production.