Comprehensive Guide to Sanitation Pumps

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Overview: Food processing is mainly divided into three main processes, namely raw material intake, semi-finished product processing, and finished product production. Pumps are involved to varying degrees in each of these stages. The requirements for pump types also vary. For example, chocolate processing requires pumps capable of transporting high-viscosity fluids; wastewater treatment needs pumps that are resistant to wear and corrosion; and pharmaceutical formulation requires pumps with excellent corrosion resistance, and so on. For different product manufacturers, the pump materials required at various stages also vary. Sanitary pumps are mainly used for filling, emptying, batching, and mixing. It is also used to transfer process fluid from equipment such as membrane filters. There are mainly two types of sanitary pumps: centrifugal and positive-displacement. Sanitary pumps are already well-developed abroad; companies that manufacture such pumps include Alfa Laval, Bominox, CSF, SPX, Grundfos, and others. There are also many manufacturers of sanitary pumps in China, with manufacturers of beer production equipment among them producing such pumps as well. Some relevant standards: Pumps used in the food, beverage, and pharmaceutical industries must meet various hygiene standards, which specify the material composition of the pumps as well as the requirements regarding cleanliness. Unlike other industrial applications, pumps used in the food and beverage industry must meet strict hygiene regulations. Standard 3-A is widely implemented in the United States and is also recognized internationally. In Europe, the “Mechanical Supply (Safety) Regulations” specify the safety and hygiene requirements for equipment used in the agricultural food industry. China’s standard for centrifugal sanitary pumps: «QBT 1826-2010 Centrifugal Sanitary Pumps». Common materials used for sanitary pumps include austenitic stainless steel (316L/304), fluoroplastics, ultra-high molecular weight polyethylene, ceramics, glass-lined steel, and so on. For pumps handling highly pure materials such as distilled water, the flow-through components are made of ultra-low carbon austenitic stainless steel. The materials used for sanitary pumps are different from ordinary materials. This is because the materials used for pumps must not only be corrosion-resistant, but also must not release harmful elements/substances, nor absorb media that could cause deterioration. Our country has established specific standards for rubber products. As specified in the \"Hygienic Standards for Rubber Products Used in Food\", standards such as QB2003 are also designated for steel pipes. Its safety evaluation method adopts GB17219-1998 or similar methods. GB17219 mainly uses the immersion method to determine the content of exudates. The standards for materials are not comprehensive. For example, 316L is commonly used in sanitary pumps, but if the 316L steel plates are not manufactured in accordance with sanitary standards, it is possible for trace amounts of harmful elements to seep out. Therefore, as stipulated in GB16798 “Safety and Hygiene of Food Machinery” and GB12073 “Safety and Hygiene of Dairy Equipment”, materials that may rust after welding must not be used routinely. Stainless steel should be non-toxic and non-absorbent. Some manufacturers have also obtained FDA and 3A certifications. There are many designs and types of sanitary pumps, which is determined by the diversity of the media they transport. From clean, potable water to milk and jam. These materials can be acidic or alkaline. Some are highly liquid while others are very difficult to liquidate. The main types of sanitary pumps are: centrifugal pumps, cam pumps, single-screw pumps, and peristaltic pumps. Their design approach is largely the same as that of ordinary pumps. But it’s not exactly the same; here, centrifugal pumps are used as an example to briefly illustrate the key points that need attention. 1. No dead corners in the flow. The point in the food processing workflow where the medium comes into contact with the pump. These media need to be fluid. In ordinary pumps, the mechanical seal chamber is often a dead zone; in such cases, an open or conical seal chamber is required. 2. The surface roughness of the weld must reach 3.2; for general surfaces, it should be 0.8. In other words, the flow channels of the pump body and the impeller need to be polished. It is difficult for ordinary cast parts to meet this requirement. Therefore, centrifugal sanitary pumps generally adopt a stamping and welding structure. Sometimes, the impeller is open or semi-open. 3. Meets CIP requirements. Most production filling lines need to be rinsed once a day. Rinse off any residues that may spoil or harbor bacteria. In many cases, clean water is used for pumping or backwashing for a certain period of time. This is related to what was mentioned earlier about having no blind spots. During a flushing period, all the material in areas where the flow of the medium is slower (such as the material in the sealing chamber) should be discharged. 4. Meets COP requirements. This requirement simply involves disassembling the pump (for example, in a back-entry pump, the bearing housing and rotor components are removed from the pump body). The high-pressure wash water can directly reach the surface to be washed. 5. Meets SIP requirements. In online disinfection, besides using a sterilizing ray, hot water/steam is also commonly used. The temperature for sterilization is generally above 121 degrees. Sanitary pumps that are sterilized by steam need to be able to withstand such high temperatures (including the seals). Pumps that use high-temperature water (water at 121°C or above, which certainly requires certain pressure to remain in a liquid state) must be able to withstand high temperatures as well as significant pressure (WeChat official account: Pump Manager). The production of sanitary pumps requires not only standard stamping pump equipment but also advanced welding and polishing equipment. Centrifugal sanitary pumps can be categorized into two main types based on their installation format: vertical and horizontal. Based on the number of impellers, they can also be divided into single-stage and multi-stage types. Due to their simple structure, low cost, continuous operation, and ease of cleaning, centrifugal sanitary pumps are widely used in aseptic processes. Since the impeller is immersed in the medium, and its high-speed rotation generates high shear forces, this can affect transport media that are sensitive to shear (WeChat official account: Pump Manager). Advantages: Simple structure, durable, and easy to clean on-site ； No overpressure due to the closure of the discharge valve ； Can be connected in series to increase the pressure head ； They can be connected in parallel to increase flow rate. Disadvantage: Generally does not have self-priming capability (except for self-priming types) ； Not suitable for use in applications where the viscosity exceeds 500 cP ； Products sensitive to shearing should not be processed ； Not suitable for handling fluids with high gas content ； The head varies with flow rate and is not constant. Positive displacement sanitary pumps are used in situations where the viscosity is too high for centrifugal pumps to be effective, as well as in cases where flow rate adjustment is required. Positive displacement pumps have self-priming capability and can handle gaseous media. However, all positive displacement pumps require pressure safety devices to prevent damage to the pump and the system in the event that the outlet is closed or blocked. Advantages: Simple and compact structure, reliable operation, long service life, easy to manufacture, convenient for maintenance, and capable of self-priming ； Internal gear pumps have a constant discharge volume and very low vibration ； It can transmit in both directions ； Flow rate changes little with viscosity and pressure ； It can transport high-viscosity media. Disadvantage: It can only transport clean fluids ； Once gears are worn, they are difficult to repair ； Cannot run idle ； High precision requirements for processing ； The gears are subjected to unbalanced radial hydraulic forces; the bearings are severely worn, and the increase in operating pressure is limited ； External gear pumps exhibit large flow fluctuations, which result in high system pressure fluctuations and high noise levels ； Liquid retention will occur. Rotary vane sanitary pumps, cam rotor pumps – Rotary vane pumps have two rotors; these rotors are either double-leaf or triple-leaf in shape. They rotate in opposite directions, and there are small gaps between the rotors as well as between the rotors and the inner walls of the pump casing, preventing direct contact between them. The rotor of a cam pump has vanes that protrude from the hub. Based on the number of vanes per rotor, cam pumps are further divided into single-vane cam pumps and double-vane cam pumps. Advantages: It can run idly for a short period of time; the allowable time depends on the quality of the sealing ； Can self-prime ； Can handle solid suspensions ； It has a relatively good net positive suction head (NPSH) ； It can handle fluids with higher viscosity (compared to centrifugal pumps) ； It can transport in both directions. Disadvantage: Due to the fixed clearance, wear causes the pump’s performance to decline rapidly ； There are two shafts and two sets of corresponding shaft seals ； It has a low suction lift and can only operate under conditions of low speed and low viscosity. Flexible impeller sanitary pumps are a type of rotary pump within the category of positive displacement pumps; they are named so because the blades of the elastic rotor move by bending, and they are also known as flexible rotor pumps or flexible impeller pumps. The earliest designs date back over half a century, when they were primarily used to clean oil and water from the holds of barges as well as to wash the decks. However, due to their excellent performance and the development of elastomer technology, flexible pumps are being increasingly used in various industrial fields. A flexible pump possesses the main characteristics of positive displacement pumps, while also being a special type of such pump. The pulsation-free liquid flow, as well as the characteristic that the flow rate decreases with an increase in outlet pressure and fluid viscosity, are similar to those of centrifugal pumps. In many industrial applications, it is used as a substitute for centrifugal pumps, addressing issues that centrifugal pumps cannot handle (media that cannot be transported or operating conditions that they cannot cope with). The flexible rotor is made of flexible material, and the pump casing has an asymmetric design. As the rotor rotates, it deforms, which changes the volume of the chamber formed by the blades and the pump casing; this is how the medium is transported (WeChat official account: Pump Manager). Advantages: Can self-priming ； The pressure vibration is low when pumping liquids ； Can transport in both directions ； Capable of transporting gaseous media and suspensions ； Easy to clean. Disadvantage: Only suitable for low-pressure conditions ； Not suitable for handling fluids with abrasive wear characteristics. Screw sanitary pumps and screw pumps transport liquids by utilizing the changes in volume of the working chamber created by the meshing between screws (or between screws and bushings). Advantages: Can self-priming ； The emission is stable with minimal vibration ； Can transport in both directions ； Capable of handling gaseous liquids ； Capable of handling suspensions ； Wide range of conveying medium viscosities ； Strong resistance to abrasive wear ； It can handle shear-sensitive fluids well. Disadvantage: Cannot run idle ； Pump performance is sensitive to viscosity changes ； High requirements for processing and assembly. Advantages of peristaltic sanitary pumps: The medium comes into contact only with the hose, resulting in no contamination ； Capable of handling gaseous fluids ； Capable of transporting shear-sensitive and oxidation-corrosion sensitive media ； Strong resistance to abrasive wear ； The diameter of solids contained in the fluid is allowed to reach 40% of the inner diameter of the tubular element ； No sealing or valve fittings required ； High precision ； Can self-priming ； Can run idle ； Capable of bidirectional flow with equal capacity ； Operation without liquid will not cause any damage to any components of the pump ； It can achieve a vacuum level of up to 98% ； Only the hose is the component that needs to be replaced, and the replacement process is extremely simple. Disadvantage: Due to the use of flexible tubes, the pressure it can withstand is limited ； Failure of the delivery pipeline can result in product loss ； The pump speed is low ； Pulsating flow is generated during operation, with significant vibration ； The flow rate range is relatively narrow.