Pumps & Systems, October 2007
Losing productivity due to faulty or malfunctioning equipment is an unnecessary expense that often results in downtime. Avoiding such issues is a key cost saving advantage in food processing. This is where the peristaltic pump comes into its own ...
Losing productivity due to faulty or malfunctioning equipment is an unnecessary expense that often results in downtime. Avoiding such issues is a key cost saving advantage in food processing. This is where the peristaltic pump comes into its own.
Unlike their diaphragm, vane, gear and lobe counterparts, peristaltic pumps have no valves, seals or glands - the cause of most blockages, leaks and contamination issues. As a result, peristaltic pumps are increasing their market share in demanding food and beverage industry applications.
Food products demand pumps that meet today's hygiene standards and are able to handle food substances with care. Peristaltic pumps guarantee these performance standards and create significant cost savings with superior performance, improved finished product quality, greater accuracy and repeatability, reduced downtime and lower maintenance costs.
In a peristaltic tube pump, the elastomer tube element is positioned along a stationary pump housing and is compressed from the outside by a roller. The tube is resistant against CIP chemicals, oils, fats and other aggressive food products.
Peristaltic pumping is the fastest growing pump technology in the world, displacing more complex and higher maintenance positive displacement (PD) pumps as the pump of choice for food processing.
How Peristalsis Works
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| In a peristaltic tube pump, the elastomer tube element is positioned along a stationary pump housing and is compressed from the outside by a roller. The tube is resistant against CIP chemicals, oils, fats and other aggressive food products. |
Peristaltic pumps are inherently valveless and sealless and have no mechanical parts in the product stream. The fluid only comes into contact with the inside of a hose or tube element, which is a low-cost, low-maintenance, and easily serviceable component.
Based on the physiological principle of peristalsis, a term referring to the alternating contraction and relaxation of muscles around a tube (e.g. the throat or intestines in the human body) to induce flow within it, a peristaltic pump's operation is elegantly simple.
A hose or tube element is positioned along a stationary pump housing and is compressed from the outside by a roller (tube pump) or a shoe (hose pump). Fluid is pushed towards the discharge as the roller or shoe moves along the outside of the element while the restitution of the hose or tube element behind the shoe draws more fluid into the pump.
The heart of the pump is a hose or tube, which is available in different elastomers specifically formulated to balance long mechanical pumping life with resistance against CIP chemicals, oils, fats and other aggressive food products. This "wetted end" simplicity of a peristaltic pump stands in stark contrast to the complexity of a lobe or diaphragm pump, where one must properly select materials for the pump housing, diaphragm, ball checks, and seals to prevent pump failure in the event of corrosive attack.
Hygienic
Inaccurate quantities, blockages and equipment failure are not the only problems that result in downtime and wasted money. Contamination also leads to the loss of batches of final product, and requires significant downtime to rectify the problem and clean equipment.
Contamination has become a more prominent issue within certain industries over the last few years. The food industry in particular has had to react to the rise in life-threatening allergies to ingredients like nuts. Manufacturers must be sure that products claiming to be free from certain substances are truly without trace of them. They cannot afford to risk any degree of contamination.
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| Peristaltic hose pumps like this one are specially designed with CIP capabilities. |
Peristaltic pumps are able to address contamination because their glandless, valveless construction has no internal gears, vanes or other obstructions or restrictions. Since the fluid is contained totally within the hose or tube, there is no risk of bacterial growth or even product clogging. There are no dead spots. The pumping action ensures that the tube is fully swept, and the suction and delivery orientation enables the pump to self drain.
Other than the smooth bored hose tube, no pump component is in contact with the pumped media at any time, and the product remains within the tube throughout the entire pumping cycle. This eliminates any risk of dilution or cross contamination. Many of the hose and tube options now commercially available are food-grade, and materials like Bioprene conform with section CFR177.2600, USP Class VI and ISO 10993-1 in the U.S. Food and Drug Administration's Code of Federal Regulations.
Easily Cleaned
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| Many of the hose and tube options now commercially available are food-grade to conform with section CFR177.2600, USP Class VI and ISO 10993-1 in the U.S. Food and Drug Administration's Code of Federal Regulations. |
Clean-in-Place (CIP) and Steam-in-Place (SIP) procedures are now essential elements in the manufacture of many foods because hygiene standards have never been under greater scrutiny.
Some peristaltic pump manufacturers now design pumps specifically for the CIP cleaning cycle. The design of these "true CIP-able" pumps includes a roller or shoe that is automatically retractable during CIP. By retracting the shoe or roller, the pump becomes nothing more than an extension of the piping, as the hose is the only fluid contact area.
These pumps enable in-line cleaning at full velocity, without the intrusion of the bypass piping and valves required by lobe and other positive displacement pumps. Dismantling and further cleaning are not required, resulting in significant operational advantages and cost savings.
Reliable
Peristaltic pumps have no seals, valves, diaphragms, glands, immersed rotors, stators or pistons to leak, clog, corrode and replace. They are virtually maintenance-free. Self priming and dry running capabilities further help to dramatically reduce spares inventory and maintenance.
A food plant's problems with downtime often result from the wrong pump being selected for the job. Making do with an existing pump or selecting the least expensive option may seem like a cost saving exercise at the time, but it is a risky approach that can lead to increased problems and more downtime.
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| Operational and maintenance costs of peristaltic pumps are almost two and a half times less than those of a diaphragm pump, and over three times less than a lobe pump. |
The draw of the peristaltic pump is its ability to pump a range of products, from abrasive vegetable peelings and waste products to delicate foodstuffs to highly corrosive chemicals. By transferring the product through a flexible tube from source to delivery, rather than through the pump head itself, corrosion or abrasive wear of the pumping mechanism is eliminated.
Downtime through routine maintenance is limited in peristaltic pumps since replacing the tube or hose is a simple and quick task that does not require an engineer. Such maintenance can be scheduled so that it doesn't affect productivity. As a result, operational and maintenance costs of peristaltic pumps are almost two and a half times less than those of a diaphragm pump and over three times less than a lobe pump.
Blocked pumps are often cited as one of the main problems in food processing and, as such, are a major cause of production downtime. Choosing a pump that helps avoid such pitfalls is a major step in reducing costs caused by lost productivity.
Low Shear
Perhaps even more important for food processing purposes is the peristaltic pumping action, which is gentle with low shear, non-emulsifying and minimal frothing and aeration characteristics.
The presentation of finished goods is critical for most products, and transfer of the product must be made without degrading consistency or appearance. Where other pumps might risk damage to the product by using impellers, vanes, lobes or valves, the low-shear action and straight-through flow of the peristaltic pump ensures product quality.
Accurate
Quantity measurements and badly monitored volumes are a major cause of incorrect and often un-useable product that results in waste and shortfalls in batch volumes. Specifying a pump that is capable of accurately measuring quantities and ensuring repeat doses is fundamental in many food processing environments.
Given suitably close control of pump speed and a dimensionally accurate hose or tube, very high standards of volumetric accuracy can be achieved and maintained. Flavorings, colorings and additives demand accurate and repeatable metering to ensure quality. Peristaltic pumps give true positive displacement with no siphoning or slip, providing an accuracy of up to ± 0.5 percent. They are some of the market's most accurate dosing and metering pumps.
Pumps in Action
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| This peristaltic pump is a fully automated solution for handling foodstuffs at Riverside Bakery. |
One example of a manufacturer that made a changeover to peristaltic technology is Riverside Bakery (Nottingham, UK), a subsidiary of the Northern Food Group that required a method of pumping pie fillings, casseroles and stews without damaging the structure of the consumable material.
Riverside needed a solution to replace the previous manual handling process, but had not been able to find an automatic solution capable of keeping the meat and vegetables intact during transfer to filling hoppers. After looking at a number of solutions, they were eventually advised to look at a peristaltic pump.
The pump they selected uses an advanced hose technology to generate tremendous suction lift and pump food products dependably over a long period of time. The pump can perform at pressures up to 50-psi with great resistance to fatigue, stress and deterioration. The tubing on the pump is post-cured to minimize leachables or extractables and ensure optimal pump performance.
The pump handles their full range of cooked foods without any problems, and fully meets USP Class VI, ISO 10993 and USDA sanitary testing standards for food safety as the operator is able to clean in-situ, quickly and easily.
Red Mill Snack Foods (Wednesbury, UK), a leading supplier in the bagged snack foods market, has helped increase production and ensure the high quality of their products by installing peristaltic pumps to meter flavorings. The long-term success of the peristaltic pumps at the Red Mill production facility has been accomplished by adding unfailing, repeatable accuracy (± 0.5 percent) and ease of cleaning to reliability and low maintenance.
First brought into service more than a decade ago, the pumps handle some thirty different flavorings used in an extensive range of extruded corn snacks. The low shear pumping action and the ability to totally enclose the pumped media within the tube - in this case, a slurry - ensures optimum levels of hygiene and product integrity. The ability to sustain volumetric accuracy, irrespective of changes in viscosity of the slurry, ensures that consistent dosage of the flavoring is maintained at all times.
Prior to the switch to peristaltic pumps, the duty was carried out by stainless steel lobe pumps. However, corrosion was a problem due to the high salt content of some of the flavorings. This caused excessive downtime and spares consumption, with the additional risk of product contamination by eroded metal particles.
The Way Ahead
In contrast to the traditional preconceptions of pumps, peristaltic pumps have helped reposition the pump as a reliable and vital link in the production process. These pumps can crucially affect lifecycle costs and productivity by reducing maintenance and operational costs and improving reliability and performance.
Such capabilities have helped the peristaltic pump establish a secure place within food production of all kinds - with indications suggesting a high growth rate over the next few years.