Peristaltic Tubing Pumps in Dispensing Applications
Properties inherent to peristaltic pumps, and features designed into Masterflex® digital pump drives, make these pumps ideal for laboratory and process dispensing applications. Accuracies in the range of ±0.5% and better are readily achievable with careful pump system selection and by following some simple procedural guidelines.
Dispensing Benefits of Peristaltic Pumps
- Fluid does not contact any part of the pump except the tubing.
- Easy and fast product changesimply change tubingno cross-contamination
- Many formulations of tubing are available to ensure chemical- and biocompatibility with your fluid; several of these formulations meet USP, FDA and other relevant classifications.
- One continuous piece of tubing from inlet to outlet lets you minimize obstructions and interruptions in the fluid path
- Some tubing materials can be easily sterilized.
- Gentle pumping action is ideal for shear-sensitive fluids, semisolids, heterogeneous mixtures, and fluids containing proteins and other large molecules.
- Wide range of flow rates provides flexibility in volume and time of dispense.
- Simple and reliable calibration to ensure accuracy and repeatability
- Non-siphoning; prevents backflow and enhances dispensing accuracy
- Multiple channel applications with either synchronous or independently controlled channels
Research, Development, and Quality Control
Masterflex tubing pumps offer accuracy and repeatability in low volume dispensing applications. Common laboratory research and development applications include transfer and distribution of fluids into smaller containers, serial dilutions, test sample preparation, and media dispensing.
Pharmaceutical and Biotechnology
Non-contamination, sterilization options for tubing, and agency classifications have all led to the popularity and utility of peristaltic pumps in pharma and biotech applications. Dispensing microbiological media, pill coating, dilutions, and packaging and filling are all everyday applications for tubing pumps in these markets.
Food and Beverage
The availability of wash-down pumps in console and modular formats and tubing formulations that meet USP, FDA, NSF, and 3A requirements all contribute to the popularity of tubing pumps in food and beverage markets. Common uses include dispensing nutraceuticals, flavorings, colorings, vitamins, and other additives in processing applications, and simple dispensing of end products on production lines or into shelf packages.
Pump Head Selection
Masterflex Standard, Easy-Load®, Easy-Load® II, and High Performance pump heads will all deliver excellent performance in dispensing applications. If you anticipate frequent tubing changes due to product change-over and wish to balance that need against initial cost, the Easy-Load and Easy-Load II pump heads are the best choice.
Number of Rollers
Fewer rollers on a given size rotor deliver higher flow rates but with higher pulsation. More rollers reduce pulsation and improve dispensing accuracy but decrease flow rate and tubing life.
Multichannel Options and Occlusion
Multichannel options include stacking two or more single-channel heads on a single drive, using a cartridge pump head, or using a multichannel pump head.
One potential advantage to stacking pump heads is realized due to the fact that rollers on stacked Easy-Load and Easy-Load II heads are offset. Uniting the flow channels from two stacked heads into a single output line will result in greatly reduced pulsation (a measured reduction of up to 95%).
Fixed occlusion pumps optimize performance repeatability and limit the potential variables leading to error. Adjustable occlusion pumps let you make minor adjustments to the pressure exerted by the rollers on the tubing. Increasing the occlusion will maximize pressure performance and suction lift; decreasing occlusion is one way to increase tubing life. Adjustable occlusion pumps also allow you to vary occlusion for minor adjustments to flow rate. In multichannel applications, adjustable occlusion may be necessary when synchronizing flow rates between stacked pump heads. Adjustable occlusion is a standard feature of our cartridge pump heads.
Cartridge heads are popular for their small overall size and performance versatility. Up to 12 individual cartridges mount on a single pump head and are ideal for applications requiring very low flow rates and/or synchronous multichannel flow.
Newer options for multichannel applications include the dual-channel L/S Easy-Load II pump heads (MFLX77202-50 and -60), and the L/S 4- and 8-channel multichannel heads that deliver synchronous flow from up to 32 channels.
Masterflex offers an extensive variety of tubing formulations to meet virtually any application. We have selected, specified, and tested each of these formulations to ensure you consistent and repeatable performance. For dispensing applications you should consider chemical compatibility first and temperature sensitivity second.
A number of resources are available in our print catalogs, on our Web sites, and through our Application Specialists to assist you in selecting the optimal tubing formulation for your application. Among those resources are chemical compatibility database specific to pump tubing. These charts are derived from actual test data in peristaltic pumps.
We have also assembled a tubing test kit that includes short samples of many of our available formulations. You can, and should, use these samples to conduct simple immersion tests in the fluid you will be pumping. Immerse a short section of tubing in the fluid for a specified period and then inspect the sample for changes in size, color, weight, and strength. These test kits are free upon request.
The friction caused by the rollers moving over the tubing, although minimal, will generate measurable heat. This heat generation can affect the mechanical properties of the tubing and result in slight variations in performance. In general, the Tygon® (PVC-based) formulations show the most pronounced temperature sensitivity. Due to reduced temperature sensitivity the recommended formulations for dispensing applications are silicones, Viton®, PharMed®, and Norprene®.
One of the newest formulations of peristaltic pump tubing, Sta-Pure®, shows several characteristics that make it ideal for dispensing. Sta-Pure has superior shape memory throughout its life in the pump. It will experience very little cross-sectional shape distortion over time and therefore show minimal variation in flow. The excellent shape memory of Sta-Pure is sufficient to negate the need for an initial break-in period.
Size your tubing so that you are operating in/around the middle of the tubing's flow capabilities in terms of volume per unit time. Doing so will give you maximum flexibility to make any necessary process adjustments without approaching either the upper or lower limit of the tubing flow range.
Loading the Tubing in the Pump Head
You will realize best performance, and best pumping life, if you take moderate care when loading tubing into the pump head. Be careful not to impart any twist or torsion to the tubing when loading. Notice that the tubing has a natural curvature, and take advantage of that curvature when laying the tubing across the rollers or onto the occlusion bed.
Tubing Break-In Period
Peristaltic pump tubing shows a distinct increase in flow stability after the first few minutes of pumping. During this break-in period the tubing adapts to a more oval cross-section due to the repeated compression of the rollers. For tubing in the L/S® sizes the minimum break-in period is 15 to 20 minutes, and 20 to 30 minutes for I/P® tubing.
Dimensions and Tolerances
Masterflex drives, pump heads, and pump tubing have all been co-designed, and are continually being monitored and refined, to deliver best performance when used together in complete pump systems. The exact dimensions and manufacturing tolerances of the tubing have direct impacts on maximizing tubing life and dispensing accuracy.
The flow rate for a given size of tubing is derived from the volume pumped per each revolution of the rollers. Volume pumped per revolution is directly proportional to the inside diameter of the tubing. Even slight variations in inside diameter can have significant impact on flow accuracy. Variations in the outside diameter of the tubing can result in the tubing not being properly retained in the pump head and being either over- or under-occluded. These problems can also impact accuracy as well as tubing life. Masterflex pump tubing is manufactured to very precise tolerances and monitored and tested to verify those tolerances. To realize the maximum accuracy and repeatability from your Masterflex pump drive, we strongly recommend that you use only Masterflex pump tubing.
Several Masterflex tubing formulations meet industry-critical regulatory approvals. Relevant classifications include those specified by the United States Pharmacopoeia (USP), European Pharmacopoeia (EP), U.S. Food and Drug Administration (FDA), U.S. Department of Agriculture (USDA) and National Sanitation Foundation (NSF).
Upon request, will provide you with a certificate validating that the tubing is in compliance with a particular regulation. This documentation will ensure that you can demonstrate compliance with your individual protocols.
Masterflex offers a variety of digital dispensing drives in both the L/S and I/P formats. Drives are available in console, modular, and modular wash-down configurations. Our two newest drives; the L/S digital console process drive MFLX07575-00 and the I/P digital console process drive MFLX77420-00; both feature a sealed, 316 stainless steel housing for wash-down environments in either laboratory or process applications. The L/S®Digital Modular Dispensing Pumps offers the widest array of dispensing features in a modular format that lets you operate up to four drives from a single programmable controller.
- Dispense by volumelets you program the volume to be dispensed for either single or multiple cycles
- Copylets you program the number of dispense cycles or repeats
- Dispense intervalan adjustable time delay between cycles, gives you ample time to reposition the tubing or filling accessory or to switch target vessels
- Cumulative volumedisplays the total volume dispensed over multiple cycles (available on the L/S and I/P digital process console drives; 07575-00 and 77420-00)
- Dispense by weightrequires an RS-232 balance-compatible interface (available on the L/S Digi-Staltic modular dispensing pump)
- Anti-drip featurebriefly reverses the rollers at the end of the dispense cycle, further ensuring accuracy (available on the L/S Digi-Staltic modular dispensing pump)
Remote control options enable easy integration of pumps into automated systems and also enhance user comfort in repetitive dispensing applications. Controllable functions include start or stop, reverse, prime, dispense or copy, and speed. Drives are available with analog (e.g., DC voltage, current, or contact closure) and/or digital (e.g., RS-232) interfaces. Control accessories include foot switches and dispensing wands for momentary start/stop and a full-function handheld remote controller for selected drives.
Proper calibration is essential to maximize dispensing accuracy. Carefully follow the directions in the product operating manual and perform no more than two or three successive calibrations. Masterflex digital dispensing drives store one calibration value per tubing size and will hold that value in memory until the pump is recalibrated for that particular tubing size.
Calibration conditions should be identical to the actual dispensing conditions. Backpressure, fluid viscosity, and fluid temperature should not vary, or vary only minimally, from calibration to and throughout dispensing. Remember to break in the tubing for the described period (see above) before calibration.