Multiple-Channel Peristaltic Pumps and Their Advantages
Peristaltic pumps are invaluable to many industries, from medicine and pharmaceuticals to environmental protection. Because a single drive mechanism can pump several fluid streams simultaneously without cross-contamination, peristaltic tubing pumps can be a flexible and economical solution to multichannel fluid transfer applications.
Among the other advantages of peristaltic pumps are that they can pump fluids over long distances, are self-priming, and can pump fluids that contain suspended solids. The pumps can provide continuous flow, consistent results, and reliable performance. In addition, they can pump several fluid streams at once, without cross-contamination, when equipped with multi-channel pump heads.
The following topics will be covered below. Click on any of these topics to go directly to that part of the page.
- Introduction to multichannel peristaltic pumps
- Components of peristaltic pumps
- Pump tubing and fluid characteristics
- Types of peristaltic pump heads
- Pump head drives
- Fluid applications
- Choosing multichannel peristaltic pump solutions
Introduction to multichannel peristaltic pumps
Technicians in research laboratories and process facilities often need to pump multiple fluids and several fluid channels simultaneously. Multichannel peristaltic pumps can be an affordable and efficient way to meet that need while saving time, space, and resources.
Multichannel peristaltic pumps use one drive motor to drive multiple pump heads simultaneously. That helps save space by providing multi-channel pumping in a compact package. Variable motor speeds allow technicians to control the timing and amount of flow in each channel at the same time. That lets users simultaneously and proportionately vary fluid flow in all channels.
Multichannel peristaltic pumps have lower operating costs and help reduce energy use Because they use a single drive motor, take up less space, and use fewer moving parts than other types of pumps. That makes peristaltic pumps easy and inexpensive, though they require routine maintenance for best performance. One of the most common maintenance items is that the tubing needs to be replaced periodically because it can wear over time. Peristaltic pumps are available with a wide range of interchangeable pump heads, drives, and tubing and can be used in many applications, including general fluid transfer, metering, and dispensing. They can be successfully used in a variety of industries, including pharmaceutical, chemical, biotech, and food processing, as well as printing, agriculture, and water treatment.
One of the most significant advantages of peristaltic pumps is that they use flexible tubing as the pump chamber. Fluids being pumped remain inside the tubing, so the tubing is the only wetted part of the pump. This significantly reduces the risk of contamination and gives you great control over the content and purity of the fluid and the integrity of your process.
Other advantages of peristaltic pumps include ease of installation, built-in backflow prevention, Among the specifications and selection criteria you should consider when you evaluate peristaltic pumps are:
- Fluid flow rates
- Fluid characteristics
- Chemical compatibility of tubing
- Ease of tubing changes
- Flexibility in pump design, such as stackable versus cartridge heads
- Overall accuracy and accuracy between channels
- Torque requirements
- Drive control features.
Components of peristaltic pumps
Peristaltic pumps contain three primary components: the motor, the pump head, and the tubing. Because the tubing is the only component that comes into contact with the fluid beings pumped, it is the only component that requires compatibility. Read more about tubing and chemical compatibility here.
Four types of motors
Peristaltic pumps typically use one of four types of motors. They are:
- Alternating current (AC) motors that use the same power source as lighting and other equipment.
- Brushed direct current (DC) motors use brushes to transfer direct current electricity to a rotor that sits inside a magnetic field. When the charge is applied to the rotor, the rotor moves in one direction.
- Brushless direct current (BLDC) motors use electronic controllers to apply current to the rotor inside a motor. Brushless motors require less maintenance because there are no brushes that may need replacement.
- Stepper motors apply an electrical current to a series of magnets surrounding a rotor rather than to the rotor itself. Because the current can be applied as a series of digital pulses, stepper motors can provide more accuracy and precise control.
Pump tubing and fluid characteristics
Flow rates and fluid dynamics through peristaltic pumps can be affected by the dimensions of the tubing, the design of the pump manifold, the geometry of the tube occlusion bed, the number of rollers, and the overall diameter of the roller assembly.
Every combination of tubing and pump head has a unique set of performance characteristics.
For example, tubing with a higher wall thickness to inside diameter (ID) ratio can generate greater suction lift relative to thin wall tubing of the same ID and is recommended for more viscous fluids.
Pump tubing
The tubing’s inside diameter (ID) is directly proportional to the flow rate for all pump heads. Larger tubing sizes and larger diameter rotors have a greater "pillow" volume—the fluid space in the tubing between adjacent rollers in the pump head—and this volume determines the flow per revolution of the pump head.
It is essential to use high-tolerance precision pump tubing and calibrate the pump with that tubing to ensure accuracy. "High tolerance" means that the tubing's internal diameter and wall thickness have been held within very narrow variance limits during manufacture. Minimal variations in the tubing dimensions directly correspond with minimal variations in flow rates.
Calibrating pumps by adjusting motor speed, run time, or occlusion—the squeezing force applied to the tubing—can further reduce variation and improve repeatability. Pumps should always be calibrated under actual application conditions, including fluid type and operating temperature.
Most tubing materials have a break-in period, during which the shape memory of the tubing and the fluid flow rate adjust and stabilize. The length of this break-in period varies depending on the tubing size and material. For high accuracy, operate a pump fitted with new pump tubing for at least 10 to 15 minutes before calibrating the flow through individual channels.
Manifolds
The flow channels of multichannel pumps can be used independently or split into multiple flows with a manifold, such as a Y-connector. When a manifold is constructed to provide a common inlet or outlet for several tubes, it reduces the number of plumbing lines from the source to the receiving vessel. Channels on the discharge side of a pump can be combined to increase the flow rate.
A combination of channels can help reduce flow pulsation when you use an offset pump head. Remember to use larger diameter tubing on the single-channel side of the manifold (either upstream or downstream of the pump) to minimize pump cavitation and backpressure.
Masterflex offers double-Y tubing assemblies that use our platinum-cured silicone tubing.
Type of fluid
Fluid characteristics are the same for single and multichannel pump applications. Low-viscosity, water-like fluids move easily through many different sizes of tubing. Higher viscosity fluids may require larger diameter tubing and have a relatively slower pumping speed.
Low-viscosity fluids move easily and with minimal wear through different sizes of tubing. Higher viscosity fluids, however, require larger-diameter tubing and work at a slower pumping speed (rpm).
Types of peristaltic pump heads
There are three types of peristaltic pump heads. They are:
- Stackable single-channel heads
- Multichannel heads
- Cartridge heads
Multichannel and cartridge heads allow multiple tubing channels within a relatively small space.
Frequent tubing changes can significantly affect pump setup and maintenance time. Some stackable pump heads must be dismantled or removed from the drive to replace the tubing. Other stackable head styles, including the Masterflex Easy-Load® pumps or most cartridge and multichannel pump heads, are easier to set up and service because operators can remove and replace tubing without dismantling the pump head.
Stackable single-channel pump heads
Stackable single-channel heads can be added or removed as needed for different applications. That is one reason why stackable pump heads are a popular choice for applications that need the flexibility to reconfigure pump design frequently. In addition, stackable heads are preferred for use with larger-size tubing or when the application requires high-suction lift or high discharge pressures.
Depending on the drive's speed range and horsepower, you can mount two to four stacked heads on a drive. The dual-channel Masterflex L/S Easy-Load II pump head can give you up to eight channels with four heads stacked on a single drive. Multiple pump heads can be either the same type or with pump heads that accept a different range of tubing sizes. This allows you to mix and match tubing sizes or pump head styles get the proportional flow rates your applications require. Proportional flow rates of over 100:1 are possible.
Stackable pump heads that use offset roller designs limit torque loading on the drive circuit when two or more are mounted together. Stacked heads with offset rollers may deliver slightly different volumes from channel to channel when used for short dispensing times or low volumes, depending on the final roller positions. Those variations can disappear when the pumps run continuously or dispense fluid volumes of several hundred milliliters.
Cartridge pump heads
Cartridge pump heads can accept a predetermined maximum number of channels. You can use any number of the available channels, up to the capability of the head and the drive. Cartridge pump heads are available separately or are an integral part of the pump. Masterflex L/S cartridge heads are modular and can be mounted on most Masterflex L/S drives. You can mount up to 12 channels on a single head with flow rates as low as 0.0005 mL/min per channel.
Cartridge pumps have long rollers to provide synchronous fluid delivery between cartridges and have more rollers than single-channel heads. That results in lower pulsation flows and higher accuracy at low volumes and flow rates. That makes cartridge pump heads ideal for low-volume and low-flow-rate fluid transfer applications.
Cartridge heads are available with adjustable occlusion for the highest between-channel accuracy of all pump head types. You can make fine adjustments to the occlusion in individual channels to compensate for minor variations in tubing dimensions that can lead to slight variations in flow.
Multichannel pump heads
Multichannel pump heads combine many of the best features of both cartridge heads and stacked single-channel heads.
Multichannel pump heads can be stacked for up to 32 channels, depending on tubing size, fluid formulation, and drive power. They offer relatively low pulsation flow from two, four, or eight channels with no cartridges. Their between-channel flow is synchronous without adjusting occlusion. That combination of features gives multichannel heads the flexibility of stacked single-channel heads with cartridge heads' synchronous flow and channel capacity.
Masterflex L/S multichannel pump heads are available for microbore tubing and Masterflex L/S tubing sizes.
Choosing pump head drives
The best choice of pump drive for your applications will depend on the torque, horsepower, and speed you require. Lower-speed drives offer greater torque and can be mounted with more stacked heads and tubing channels than high-speed drives.
Fixed-speed drives are often satisfactory for basic transfer applications. Variable-speed drives let you adjust flow rates simultaneously for all channels, with flow rates in secondary channels proportionate to the first channel.
Different speeds and gear ratios provide a range of torque outputs, and different tubing sizes allow for different flow rates. That means you can get a wide range of flow rates by adjusting drive speed or selecting different tubing sizes.
Digital drives provide the most precise and repeatable speed control for accurate flow rates. Digital drives may also display flow rate, pump motor speed (rpm), dispense volume, and cumulative volume over multiple cycles. Flow rates and volume display will typically be for only one channel unless you build multiple flowmeters into your system.
Fluid applications
Fixed-speed and fixed-occlusion pumps are popular for their flow rate repeatability, consistent tube loading, and ease of use. When used with precision extruded tubing, these pumps can deliver fluids with an accuracy of 3 to 5% between channels. That degree of accuracy is acceptable for many applications, including bulk fluid transfer, heat exchangers, and ink transfer in printing. Complete Masterflex I/P fixed-speed pump systems that are washdown-rated for process applications are available in 3-channel and 4-channel configurations.
Cartridge and multichannel pump heads are popular for applications requiring accurate sampling, dispensing, and fluid metering. Synchronous rollers provide coordinated fluid delivery between channels in the pump head.
Among applications that demand high levels of performance and accuracy are precision dispensing and metering, analytical techniques in research and quality assurance, and environmental sampling and monitoring. Multichannel heads deliver between-channel flow accuracy of 1.5 to 2%. Cartridge pump heads with adjustable occlusion can deliver 1% flow accuracy between channels.
Choosing multichannel peristaltic pump solutions
Peristaltic tubing pumps can provide the combination of fluid handling characteristics and configuration flexibility you need for multiple-channel applications. The variety of interchangeable tubing sizes, tubing materials, pump heads, and drives lets you configure your pumping system to provide the performance you need at an economical cost.
Multichannel peristaltic pumping systems can be used in many applications with tremendous time, space, and resource savings. Contact us today to discuss the pump, head, and tubing options available to meet your needs.