A peristaltic pump is a type of positive displacement pump that moves fluid by compressing a flexible tube, creating a wave-like motion that pushes the liquid forward. The pump’s name is derived from peristalsis, the biological process where sequential muscle contractions transport contents through a tube, such as in the human digestive tract. This mechanical action contains the pumped fluid entirely within the tubing, isolating it from the internal pump mechanism.
Fundamental Mechanism of Fluid Movement
The core principle of a peristaltic pump relies on a process called occlusion, where a roller or shoe presses the flexible tubing completely shut against a fixed housing. This temporary seal traps a specific volume of fluid between two compression points, effectively creating a “pillow” of liquid. The pump’s rotor then begins to turn, causing the compression point to advance along the length of the tubing.
As the compression moves, the sealed volume of fluid is displaced toward the pump outlet. Behind the moving roller, the tubing relaxes and returns to its original shape, which creates a vacuum effect at the inlet side. This vacuum draws a new volume of fluid into the tube, ready for the next cycle of compression.
This sequential squeezing and releasing motion results in a continuous, positive displacement flow. The volume of fluid dispensed per revolution is fixed by the tube’s inner diameter and the geometry of the rotor, providing highly predictable and repeatable flow rates. Since the fluid is physically pushed forward by the moving compression, the pump can handle liquids with varying viscosities and even slurries with high solids content.
Essential Components and Tubing Selection
A peristaltic pump is composed of three primary parts: a drive motor, a pump head or casing, and the flexible tubing. The motor provides the rotational power to the rotor, which is equipped with rollers or shoes. The pump head is the stationary track against which the tubing is compressed by the rotating elements.
The flexible tubing is the single most important component because it is the only part that contacts the fluid being pumped. Tubing material selection is determined by several factors, including the required durability to withstand repeated mechanical stress from the rollers and its chemical compatibility with the fluid. Incompatible materials can degrade quickly, leading to contamination or pump failure.
Materials such as silicone are frequently used for medical and food-grade applications due to their high flexibility and biocompatibility, but they lack resistance to strong acids or oils. Conversely, fluoropolymers offer outstanding chemical resistance, making them suitable for aggressive chemicals, though they are often more expensive. Other options like Tygon, PVC, and Viton offer different balances of flexibility, chemical resistance, and temperature tolerance.
Operational Characteristics and Design Advantages
The design of the peristaltic pump offers several unique performance features. Fluid isolation is a primary advantage; the liquid remains confined within the tubing, never touching the mechanical components, seals, or valves of the pump. This prevents contamination of the fluid and protects the pump from corrosive or abrasive materials.
The pump has an inherent self-priming capability, meaning it can draw fluid from a source below its own level without external assistance. The strong vacuum created when the compressed tubing recovers its shape is responsible for this powerful suction, which can typically lift fluids up to eight or nine meters. Furthermore, the precise volume of the fluid “pillow” trapped between the rollers allows for high metering accuracy, making these pumps excellent for precision dosing and dispensing applications.
Peristaltic pumps provide gentle fluid handling, exerting low shear force because the liquid flows in a single, continuous stream, unlike the high-speed impeller action of other pump types. This low-shear action is beneficial for pumping delicate fluids, such as live cell cultures, emulsions, or shear-sensitive polymers. The pump also acts as its own check valve; the complete occlusion of the tube creates a seal that prevents backflow when the pump is stopped.
Common Applications Across Industries
Peristaltic pumps are utilized across diverse industries due to their ability to handle a broad range of fluids while maintaining isolation and precision. In medical settings, they are commonly found in devices like dialysis machines, infusion pumps, and heart-lung bypass systems. The sterile nature of the fluid path is a defining factor for their use in these sensitive applications.
The food and beverage industry uses these pumps for dispensing viscous liquids like sauces, syrups, and flavorings, as the gentle action handles shear-sensitive products. In pharmaceutical and biotechnology manufacturing, they are used for precise dosing of Active Pharmaceutical Ingredients (APIs) and transferring sterile media in bioreactors.
Industrial and environmental applications include the accurate injection of chemicals, such as chlorine or flocculants, in water and wastewater treatment plants. They are also robust enough to handle abrasive slurries in mining operations, where the fluid-containing tube protects the mechanical components from wear. Laboratory and research environments rely on them for chromatography, filtration, and automated liquid handling systems requiring precise volume control.