A peristaltic pump is a type of positive displacement pump used to pump various liquids. This fluid is contained in a flexible tube mounted inside a circular pump casing (although linear peristaltic pumps have been made). A rotor with a number of "rollers", "shoes", "wipers", or "lobes" attached to the rotor outer rim depresses the flexible tube. When the rotor is changed, the part of the tube under the compression is wedged closed (or "clogged") to force the liquid to be pumped to move through the tube. In addition, as the tube is exposed to its natural state upon passing the cam ("restitution" or "resistance") the liquid stream is induced into the pump. This process is called peristaltic and is used in many biological systems such as the gastrointestinal tract. Usually, there will be two or more rollers, or wipers, covering the tubes, trapping between them a single body of fluid. The body of the liquid is then transported, at ambient pressure, to the pump outlet. Peristaltic pumps can run continuously, or they can be indexed through partial revolutions to produce less fluid amounts.
Video Peristaltic pump
History
The first peristaltic pump was patented in the United States by Rufus Porter and J.D. Bradley in 1855 (US Pat. No. 12753) as well pump, and then by Eugene Allen in 1881 (US Patent number 249285) for blood transfusion. It was developed by heart surgeon Dr. Michael DeBakey for blood transfusion when he became a medical student in 1932 and later used by him for the cardiopulmonary bypass system. The special non-exclusive roller pump (US Patent 5222880) using soft flat pipes was developed in 1992 for the cardiopulmonary bypass system.
Maps Peristaltic pump
Apps
Peristaltic pumps are usually used for pumping clean/sterile or aggressive fluids without exposing them to the contamination of the exposed pump components. Some common applications include pumping IV fluids through infusion devices, apheresis, aggressive chemicals, high density slurry and other materials where the isolation of products from the environment, and the environment of the product, is essential. It is also used in the heart-lung machine to circulate blood during bypass surgery, and in the hemodialysis system, since the pump does not cause significant haemolysis.
Peristaltic pumps are also used in a variety of industrial applications. Their unique design makes them particularly suitable for pumping abrasives and viscous liquids.
Main design parameters
The ideal peristaltic pump should have an infinite diameter of the pump head and the largest possible roller diameter. Just as the ideal peristaltic pump will offer the longest tube life and provide constant and pulsation-free flow rates.
Such ideal peristaltic pumps can not be built in reality. However, peristaltic pumps can be designed to approach these ideal peristaltic pump parameters. One example of possible construction is illustrated. The exceptional design of multiple peristaltic pumps offers constant constant flow rates over several weeks along with long tube life without the risk of tubing rupture.
Chemical compatibility
The pumped liquid only touches the inside of the tubing surface thus negating the worries for other valves, O-rings or seals that may be incompatible with the fluid being pumped. Therefore, only the composition of pipes pumped by the pumped medium is considered for chemical compatibility.
Pipes must be elastomers to maintain a circular cross section after millions of cycles punched in the pump. This requirement eliminates various non-elastomeric polymers that have compatibility with various chemicals, such as PTFE, polyolefin, PVDF, etc. From consideration as material for pump tube. Popular elastomers for pump tubes are nitrile (NBR), Hypalon, Viton, silicon, PVC, EPDM, EPDM polypropylene (as in Santoprene), polyurethane and natural rubber. Of these materials, natural rubber has the best fatigue resistance, and EPDM and Hypalon have the best chemical compatibility. Silicone is popular with water-based liquids, as in the bio-pharmaceutical industry, but has limitations of chemical compatibility in other industries.
Extruded fluoropolymer tubes such as FKM (Viton, Fluorel, etc.) have good compatibility with acid, hydrocarbons and petroleum fuels, but do not have enough fatigue resistance to achieve effective tube life.
There are several new tubing developments that offer wide chemical compatibility using lined tubing and fluoroelastomers.
With a lined pipe, thinner liners are made of chemically resistant materials such as poly-olefins and PTFE that form a barrier for the rest of the tubing wall to avoid touching the pumped liquid. These liners are often non elastomeric materials, so the entire tube wall can not be made with this material for peristaltic pump applications. This tube provides sufficient chemical compatibility and life to be used in chemically challenged applications. There are a few things to keep in mind when using this tube - every pin hole in the liner during manufacturing can make the tubing vulnerable to chemical attack. In the case of rigid plastic liners such as polyolefins, with recurrent flexing at the peristaltic pump, they can develop cracks, so that the fall material is again susceptible to chemical attack. A common problem with all lined tubing is linear delamination with recurrent flexing that signifies the end of the tube. For those who need compatible chemical tubes, these lined tubes offer a good solution.
With fluoroelastomer tubes, the elastomers themselves have chemical resistance. In the case of eg Chem-Sure, made of perfluoroelastomer, which has the widest chemical compatibility of all elastomers. The two fluoroelastomer tubes listed above combine chemical compatibility with very long tube life derived from their strengthening technology, but come with a high initial cost. We must justify the cost with the total value obtained during the lifetime of the long tube, and compare it with other options such as other tubes or even other pumping technologies.
There are many sites online to check the chemical compatibility of the tube material with the fluid being pumped. The tube manufacturers may also have a special suitability chart for tube production methods, coatings, materials and pumped liquids.
While these charts include a list of commonly encountered liquids, they may not have all the fluids. If any of the compatibility liquids are not listed elsewhere, then the general compatibility test is immersion testing. Samples 1 to 2 inches from the tubing are immersed in liquid to be pumped for 24 to 48 hours, and the amount of weight changes from before and after immersion is measured. If the weight changes more than 10% of the initial weight, then the tube is not compatible with the liquid, and should not be used in the application. This test is still a one-way test, in the sense that there is still a far-reaching chance that the tubes passing through this test can still be unsuitable for the application because a combination of boundary compatibility and mechanical flexibility can push the tube over the limit, resulting in premature tube failure.
In general, recent tube development has brought extensive chemical compatibility to peristaltic pump options that many chemical dosing applications can be useful compared to other pumping technologies today.
Occlusion
The minimum gap between the roller and the housing determines the maximum pressure applied to the tubing. The amount of juice applied to the tubing affects pumping performance and tube life - more pressing reduces tube life dramatically, while less pressing can cause the pumped medium to slip back, especially in high pressure pumping, and dramatically reduce pump efficiency. and high speed back slip usually leads to premature failure of the hose. Therefore, the extent of this extortion becomes an important design parameter.
The term "occlusion" is used to measure the amount of pressure. It is either expressed as a percentage of twice the wall thickness, or as the absolute number of squeezed walls.
Let
- y = occlusion
- g = minimum distance between roller and housing
- t = tubing wall thickness
Then
- y = 2t - g (when expressed as absolute amount of blackmail)
- y = (2t - g)/(2t) ÃÆ'â € "100 (if expressed as a percentage of twice the wall thickness)
Occlusions are usually 10 to 20%, with higher occlusion for a softer tube material and lower occlusion for harder tube material.
So for the given pump, the most critical dimension of the tube becomes the wall thickness. The interesting thing here is that the inner diameter of the pipe is not an important design parameter for the suitability of the pipe for the pump. Therefore, usually more than one ID is used with the pump, as long as the wall thickness remains the same.
Inner diameter
For a particular rpm of the pump, the tubes with a larger inner diameter (ID) will provide a higher flow rate than having a smaller inner diameter. Intuitive flow rate is the function of the tube cross section area.
Flow
Flow rate is an important parameter for the pump. The flow rate in the peristaltic pump is determined by many factors, such as:
- Tube ID - higher flow rate with larger ID
- OD pump head - higher flow rate with larger OD
- RPM head pump - higher flow rate with higher RPM
- Inlet Pulsation - pulse reduces hose filling volume
Increasing the number of rollers does not increase the flow rate, but will decrease the flow rate by reducing the effective head circumference (ie pumping fluids). The increased roll tends to reduce the amplitude of the fluid pulsing at the outlet by increasing the pulse flow frequency.
The length of the tube (measured from the initial pinch point near the inlet to the final discharge point near the outlet) does not affect the flow rate. However, longer tubes imply more gripping points between the inlet and outlet, increasing the pressure that the pump can generate.
The flow rate of the peristaltic pump in most cases is not linear. The pulsation effect on the pump inlet changes the rate of charging of the peristaltic tube. With a high inlet pulse the peristaltic tube becomes oval and this results in less flow. Accurate measurements with peristaltic pumps are only possible when the pump has a constant flow rate, or when the inlet pulse is removed with the use of properly designed pulsation dampers.
Pulsate
Pulsation is an important side effect of the peristaltic pump. Pulsation in the peristaltic pump is determined by many factors, such as:
- Flow Rate - Higher flow rate over pulsation
- Line Length - Longer pipeline length
- Higher Pump Speed ​​- RPM is higher over pulsation
- S.G. of fluid - higher fluid density over Pulsation
Variations
Hose Pump
High pressure peristaltic pressure pumps that can usually operate up to 16 bar in sustainable service, use shoes (rollers are only used in low pressure types) and have casing filled with lubricants to prevent outer abrasion of pump tubes and to assist in heat dissipation, and use tubes which is reinforced, often called a "hose". This pump class is often called a "hose pump".
The biggest advantage with hose pumps over roller pumps is high operating pressure up to 16 bar. With maximum roller pressure it can be up to 12 Bar with no problem. If high operating pressure is not required, a tube pump is a better choice than a hose pump if the pumped medium is not abrasive. With the latest advancements made in tubing technology for the compatibility of pressure, life and chemistry, as well as higher flow rate ranges, the excess pump hose has more than the roller pump continues to erode.
Tube Pump
Low pressure peristaltic pumps usually have dried casing and use a roller along with unstrengthened and extruded tubing. This pump class is sometimes called a "tube pump" or "tube pump". This pump uses a roller to press the tube. Except for the  °  ° eccentric pump design as described below, this pump has at least 2 separate 180  ° rolls, and may have as many as 8, or even 12 rollers. An increase in the number of rollers increases the pulse pressure frequency of the pumped liquid at the outlet, thereby decreasing the pulsing amplitude. The disadvantage of increasing the number of rollers proportionally increases the amount of squeezing, or occlusion, of the tubing for a particular cumulative stream through the tube, thereby reducing the life of the tube.
There are two types of roller designs in peristaltic pumps:
- Fixed occlusion - In this type of pump, the roller has a fixed locus while rotating, keeping the occlusion constant while squeezing the tube. This is a simple yet effective design. The only downside to this design is that the occlusion as a percent on the tube varies with the variation in the thickness of the tube wall. Usually the wall thickness of extruded tubes varies considerably so that the% occlusion may vary with wall thickness (see above). Therefore, the tube section with greater wall thickness, but in acceptable tolerance, will have a higher percent occlusion, which increases wear and tear on the tubing, thereby reducing the life of the tube. The current tolerance of tubular wall thickness is generally maintained fairly tightly so that this problem is not of much practical concern. For those who tend to be mechanical, this may be a constant voltage operation.
- Spring rollers - As the name suggests, the rollers in these pumps are installed in the spring. This design is more complicated than fixed occlusion, but helps to overcome the variation in tube wall thickness over a wider range. Regardless of the variation, the roller imparts the same amount of pressure to the tubing as proportional to the spring constant, making it a constant voltage operation. The spring is chosen to overcome not only the pipe's circular strength, but also the pressure of the pumped liquid.
The operating pressure of the pump is determined by the tube and by the motor's ability to overcome the pipe's circular strength and fluid pressure.
microfluidic pump
In microfluidics, it is often desirable to minimize the volume of fluid circulation. Traditional pumps require large volumes of external fluid to the microfluidic circuits. This can cause problems due to dilution of the analyte and already dilute the biological signal molecule. For this reason, inter alia, it is desirable to integrate the micro-pumping structure into microfluidic circuits. Wu et al. was presented in 2008 an actuated pneumatic peristaltic micropump that eliminates the need for a large volume of external fluid circulation.
Benefits
- No contamination. Since the only part of the pump that comes in contact with the pumped liquid is the inside of the tube, it is easy to sterilize and clean the inner surface of the pump.
- Low maintenance needs. Lack of valves, seals, and glands make them relatively cheap to treat.
- They are capable of handling slurry, viscous, shear sensitive, and aggressive.
- The pump design prevents backflow and syphoning without valves.
- The amount of fluid that remains pumped per cycle, so it can be used to measure the amount of liquid pumped roughly.
- Easy to clean
Loss
- Flexible pipes tend to decrease with time and require frequent replacements.
- The flow pulsates, especially at low speeds. Therefore, this pump is less suitable where a smooth consistent flow is required. Alternative types of positive displacement pumps should be considered.
- Effectiveness is limited by liquid viscosity
Tubing
It is important to choose a tube with proper chemical resistance against the pumped liquid. Types of tubing commonly used in peristaltic pumps include:
- Polyvinyl chloride (PVC)
- Silicone Rubber
- Fluoropolymer
- PharMed
General app
- Medicine
- Dialysis machine
- An open heart bypass pump machine
- Medical infusion pump
- Testing and research
- AutoAnalyzer
- Analytical chemistry experiments
- Carbon monoxide monitor
- Media dispenser
- Agriculture
- 'Sapsucker' pumps to extract tree maple sap
- Manufacture and sale of food
- Liquid food fountain (eg cheese sauce for nachos)
- Drinking drinks
- Foodservice cleaning machine fluid pump
- Chemical handling
- Print, paint and pigment
- Pharmaceutical production
- Dosing system for dishwasher and laundry chemicals
- Engineering and manufacturing
- Concrete Pump
- Pulp and paper factory
- Minimum quantity lubrication
- Water and Waste
- Chemical treatment at a water purification plant
- sewage waste
- Aquariums, especially calcium reactors
References
Source of the article : Wikipedia
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