Peristaltic Pump: Basics and Applications

A peristaltic pump uses positive displacement to pump different types of fluids. The principle of positive displacement uses a mechanism to repeatedly expand a cavity, so as to allow fluids to flow into the cavity, and then seal it. After this, the fluid moves forward.

Normally, the fluid is in a flexible tube and a rotor or a number of rollers, shoes, or wipers, are attached to the external surface of the tube. As the rotors or the rollers move, a part of the tube is pressed, causing the fluid to be pumped onward.

As the rotors or rollers move back, a restitution fluid can be sent into the pump. This process is known as 'Peristalsis' and it is the basic function of a Peristaltic Pump. A similar kind of process can also be seen in the gastrointestinal tract in the human body.

In peristaltic pumps, this operation is conducted in either a circular or in a linear fashion. This means that the process can be conducted in motors where such tubes are arranged either in a circular fashion or in a straight line.

The pumps which use the circular arrangement of the tubes, usually have the motor encased with the tube, with rollers or shoes moving along the edge, which cause the pumping of the fluid within the tube. These are known as 'Rotary Peristaltic Pumps'.

There are 2 types of peristaltic pumps based on the kind of pressure they use.
They are:

• High Pressure Peristaltic Pumps: These are generally used in high pressure environment (up to 16 bar) and use shoes. They have casings which are filled with lubricants to help avoid damage caused by abrasion to the exterior and to help dissipate the heat created during the process.

They use reinforced tubes so that the liquids do not leak out of the tube due to the high pressures used while pumping.

• Low Pressure Peristaltic Pumps: These usually have dry casings and use rollers. Non-reinforced tubes are also used in these, because the pressure on the tubes is not very high.

Different types of tubing materials are used in such pumps. This material has to be resistant to chemicals and high pressures. The different types of tubing material normally used are:

• Polyvinyl chloride or PVC
• Silicone rubber
• Fluoropolymer

Peristaltic Pumps find their uses and applications in a variety of places where fluids are needed to be moved in clean and sterile conditions. They have also found their uses in some everyday applications as well.

• Dialysis machines
• Infusion pumps
• Beverage dispensing machines
• Aquariums
• Analytical chemistry experiments
• Open heart bypass pump machines
• Pharmaceutical production
• AutoAnalyzers
• Carbon Monoxide monitors
• Removal of sewage sludge
• Industrial dishwasher rinse aid dispensers
• Decorative fountains and waterfalls

Peristaltic pumps are preferred for use in a clean and sterile environment, because only the interior of the tubes are in contact with the fluid. This makes it easy to clean and sterilize. Due to the fact that the liquids pumped with these can be isolated from their environment quite easily, they are also used in places where it is preferred that the product and its environment be kept isolated and separate from one another.

The maintenance of peristaltic pumps is relatively easy as the replacement of tubes is a low cost affair and they do not use any valves, seals, or glands.