Peristaltic pump hose is one of the important components of peristaltic pumps, but end users often choose the wrong tubing material, making it unsuitable for the required application. Some users even use ordinary pipes instead of peristaltic pump hoses, with disastrous consequences. With the increasing number of types of peristaltic pump hoses on the market, it is also becoming more difficult to select pump tubes. Peristaltic pumps are growing in popularity due to their pollution-free pumping properties and the low maintenance they require. However, when designing or purchasing a peristaltic pump system, many engineers often overlook an important component - the peristaltic pump tube.
1. Chemical compatibility
The pipe must be chemically compatible with the fluid to be pumped in order to have good pumping performance and safety. With an increasing number of tubing materials on the market—as many as 15 tubing materials are available for some peristaltic pump models—users can always find a suitable tubing material that is chemically compatible with a specific fluid.
Many pump tubing suppliers provide chemical compatibility charts. Engineers are cautioned, however, to use chemical compatibility tables developed specifically for pump tubing rather than those developed for general pipes. Because ordinary pipelines only have general contact with chemical substances, while peristaltic pump tubing is in contact with chemical fluids under pressure, the chemical compatibility level of ordinary pipelines cannot be equal to that of peristaltic pump tubing. Therefore, you should only refer to the chemical compatibility level of the pump tube, rather than the general pipeline and related substances. Otherwise, the pump tube will fail or be damaged and leak, resulting in damage to the pump or dangerous accidents.
When the end user refers to the chemical compatibility table, each component of the solution, not just the main component, should be checked for compatibility with the pipe material to be used. Some acids or solvents, even in trace amounts, can cause enough damage to pump tubing hours or days after they come into contact with it. The end user should verify each chemical in the solution to ensure that it is compatible with the selected pump tubing.
Also keep in mind: The chemical resistance of pump tubing decreases as temperature increases. Although some chemicals have no effect on the pump tube at room temperature, they will cause damage to the pump tube when the temperature rises to a certain level. Specific environmental condition limits, especially temperature limits, must be noted in the chemical compatibility table before they can be used to determine chemical compatibility.
If a chemical is not listed in the chemical compatibility table, or if the operating environmental conditions of a plant are too different from those specified in the table, an immersion test can be used to obtain more reliable information. This method can be used when determining chemical compatibility when no other information is available.
The steps for the immersion test are as follows: Take a small section of pump tubing, weigh it, and measure its diameter and length. The pump tube is then placed in a closed container containing the relevant chemicals and soaked for 48 hours. Take out the tube, wash it, dry it, weigh it and measure its dimensions, and record the change between the two measurements. Pump tubing should also be inspected for signs of softening or brittleness, which may indicate chemical damage to the tubing. After pre-selecting one or several pipe materials, the pumping test can be carried out. Each candidate pump tubing sample should be put into trial operation under actual factory environmental conditions and the test results should be closely observed. The pump tubing is compatible with the fluid if it does not show discoloration, swelling, cracks, loss of fluidity, or other signs of deterioration after a test run.
Remember, the ultimate responsibility for selecting the right tubing, whether by consulting a compatibility chart, performing physical testing, or both, rests with the end user. Careful analysis and testing can ensure correct test results, thereby avoiding damage to the pump and ensuring the safety of people and property.
The chemical compatibility of different pipe materials and solutions varies greatly. But there are also some materials that are extremely resistant to most chemicals. For example, Viton fluoroelastomer pump tubing is resistant to many inorganic chemicals and even some organic chemicals. As another example, polytetrafluoroethylene (PTFE) pump tubing is compatible with almost all chemicals. However, PTFE pump pipe is a rigid pipe and requires a special pump head. In situations where multiple corrosive chemicals need to be pumped, pipes that are resistant to multiple chemicals should be the best choice.
2. Pressure
The advent of high-pressure pump tubing has expanded the scope of peristaltic pump applications to unprecedented applications, including filtration.
The pressure sources within a fluid delivery system can vary. Backpressure is created when fluid is pushed through a filter, pushed through a flow meter or valve, or pumped into a pressurized reaction vessel. Before selecting pipe materials, the user should first make sure that all pressure sources in the system have been clarified and the actual measured value of the total pressure of the system has been obtained. When selecting pump tubing for a peristaltic pump, users should ensure that the pressure in the system does not exceed the recommended working pressure of the pump tubing. If the pressure is too high, the pump tube will bulge and not fit well with the pump head, causing rapid wear and failure. When the system pressure greatly exceeds the bearing capacity of the pump pipe, it may even cause the pump pipe to burst and eject fluid, endangering safety. After selecting a pipe material, be sure to maintain the pressure within the manufacturer's recommended pressure range when using it. If the system exceeds maximum operating pressure, a simple pressure relief valve or pressure switch can be installed to prevent excess pressure from building up. The function of the pressure relief valve is: when the system pressure exceeds the set value, it vents to the atmosphere to reduce the system pressure to a safe level. A more complex pressure switch can also be used, which switches off the equipment via a relay or sounds an alarm when the pressure value exceeds a set value. When the system pressure exceeds the safety line, both of the above methods are beneficial to safety.
3. Temperature
The operating temperature range of the pump tubing is another important factor to consider. Some pipes, such as silicone rubber, have a wide temperature tolerance range and are suitable for both high and low temperature processes; while some pipes, such as Tygon¯ and C-Flex¯, are only suitable for a smaller temperature range. Before selecting pipe materials, the end user should first understand the maximum and minimum temperatures in the system, and then ensure that the selected pump pipe can safely operate within this temperature range. In applications where gradually increasing temperatures are required, the end user should consider the effect of temperature on the chemical resistance and pressure-bearing capabilities of the pump tubing. As the temperature increases, the pressure-bearing capacity of the pump tube will decrease.
4. Size
As each roller in the pump head presses through the pump tube, the peristaltic pump will pump a certain amount of fluid. Therefore, the size of the pump tube is directly related to the pumping flow rate. In other words, it has a great impact on the operation of the fluid delivery system. Pump tubing is an important part to consider when designing a high-quality peristaltic pump. The optimal size or optimal size range of the pump tubing needs to be calculated. The size here mainly refers to the inner diameter and thickness of the pump tube. The inner diameter determines the amount of fluid pumped per revolution of the rotor, while the thickness determines the ability of the pump tube to return to its original shape after each rolling. This ability greatly affects the service life of the pump tube. If the size of the pump tube is too small relative to the size of the pump head, the pump head cannot hold the pump tube firmly, and the pump tube will be pulled out of the pump head; and if the size of the pump tube is too small, the rollers in the pump head cannot press the pump tube, and the pump tube will be pulled out of the pump head. This will cause insufficient pumping flow or complete failure. If the size of the pump tube is too large, the excess tubing will create wrinkles between the roller and the pump housing or between the roller and the bite bed, causing excessive wear and premature failure. End users should follow the manufacturer's recommendations when selecting pump tubing sizes to ensure proper system function. In some applications that require higher accuracy (such as chemical dosing pumps), the role of pump tube size is even more prominent. A slight deviation in the size will lead to a large deviation in flow rate or distribution volume and fail. Although the pump tube sizes provided by some manufacturers are "close" to the recommended sizes and "look the same", there is often still a gap. Therefore, in order to achieve the best performance and working accuracy of the pump system, users should use pump tube sizes that are exactly consistent with the sizes recommended by the manufacturer.
5. Tolerance
Tolerance is the allowable error in the size of the pump tube. The smaller the tolerance, the smaller the performance variation of the pump tubing, and the better the consistency and repeatability. The larger the tolerance, the more unstable the performance of the pump tubing will be. Some pump tubes are manufactured to extremely tight tolerances, and their dimensional deviations are strictly controlled during extrusion molding. Pump tubing manufactured to tight tolerances is slightly more expensive, but the cost is worth the increase in pumping performance.
6. Average life of pump tubes
The conditions faced by peristaltic pumps are relatively harsh, so pipes with better intrinsic quality, especially pipes with better resilience, will have a longer service life. In the long run, the longer the pipe service life, the lower the operating costs. Fewer pump tubing changes mean less maintenance costs and downtime. There is also less chance of leaks and bursts in the pump tubing. In summary, the longer the pump tubing lasts, the lower the total pumping costs will be. Pump tubing manufacturers should provide test data to prove their claimed pump tubing life. Some manufacturers publish this information in their manuals, such as the Cole-Parmer Instruments Masterflex Pump Fact Sheet. Regardless, engineers designing a system should have an understanding of the average life of the tubing in order to help the end user design a system. Preventive maintenance programs so that pump tubing can be replaced before it fails. Pump tubing suppliers with extensive technical knowledge can provide users with useful information for selecting the appropriate pump tubing material for specific applications.
7. Transparency
Whether a transparent pipe should be used depends first on whether the operator needs to observe the condition of the fluid in the pipe at any time, and also whether the fluid is sensitive to light. If the operator needs to observe the fluid, bubbles, particles, pollution, etc. in the tube at any time, transparent tubes such as Tygon polyethylene or silicone rubber should be used; and if the solution is not suitable for exposure, opaque tubes should be used
8. Breathability
For some gas-sensitive fluids, such as fluids susceptible to oxidation, or anaerobic cell culture fluids, users should consider the air permeability factor of the pipeline. Overall, silicone tubes are the most breathable. Therefore, for fluids that are not suitable for contact with gas, pipes with lower air permeability should be used.
9. Regulations and permissions
For the pharmaceutical industry, regulatory compliance is critical. In this industry, every item that comes into contact with the final product must meet specific standards and guidelines. For this reason, many pump tubing materials are developed in strict compliance with regulatory requirements. These regulations include the United States Pharmacopeia (USP), the European Pharmacopoeia (EP), the United States Food and Drug Administration (FDA), the United States Department of Agriculture (USDA), and the National Sanitation Foundation (NSF). Of course, it is not enough to claim that such and such material complies with such and such regulations. The pump pipe manufacturer shall provide the user with a certificate proving that the pipe complies with this regulation upon user request. This enables the user to provide the necessary certificates proving that the pump system complies with the necessary regulatory approvals.
10. Cost
Cost is a factor that needs to be considered when formulating almost every project proposal. As with any other component selection, the user should evaluate the overall cost of ownership of alternative pump tubing. For example, if a certain type of pump tubing costs $2 per foot and needs to be replaced every 500 hours; while another type of pump tubing costs $1 per foot and needs to be replaced every 100 hours; the former is more cost-effective than the latter. Sudden rupture of low-quality pump tubing can result in loss of valuable fluid or damage to the pump, resulting in costly downtime and extensive repairs or even replacement of the entire pump. Therefore, the cheapest pump tubing is not necessarily the most economical option. It may seem impossible to choose the ideal pump tube in the vast variety of pump tubes on the market. However, as long as you carefully study the system requirements, refer to relevant technical indicators, and maintain close communication with pump tubing manufacturers or suppliers with application knowledge and experience, you can select the most suitable pump tubing for the relevant pump system.