Material selection for food machinery

Food production has its own unique method, which is characterized by: a lot of contact with water, the temperature of the machine is large; it is often operated at high or low temperature, and the machine works in an environment with a large temperature difference; direct contact with food and corrosive media, The material wear of the machine is larger. Therefore, when selecting the materials for food machinery and equipment, especially the materials that are in contact with food machinery and food, in addition to considering the mechanical properties such as strength, stiffness, vibration resistance, etc., which are required by general mechanical design, the following principles should also be paid attention to: 1. It should not contain elements that are harmful to human health or elements that can produce chemical reactions in food. 2. It should have high corrosion resistance. 3. It should be easy to clean and maintain no discoloration for a long time. 4. It should be able to maintain good mechanical properties in high and low temperature. According to the above principles, the use of materials in the food machinery industry is as follows: 1. Stainless steel has the advantages of corrosion resistance, rust resistance, no discoloration, no deterioration and easy removal of attached food, and good high temperature and low temperature mechanical properties, so it is obtained in food machinery. Wide range of applications. Stainless steel is mainly used in pumps, valves, pipes, tanks, pots, heat exchangers, concentration devices, vacuum containers, etc. of food processing machinery. In addition, in addition to food processing machinery, stainless steel is also used for food cleaning machinery, food transportation, storage, storage tanks, and utensils that will affect food hygiene because of rust. 2. Iron and steel materials have unique advantages in wear resistance, fatigue resistance, impact resistance, etc. Therefore, they are still widely used in food machinery, especially flour-making machinery, noodle-making machinery, and puffing machinery in my country. Among the steels used, carbon steel is the most used, mainly 45 and A3 steels. These steels are mainly used for structural parts of food machinery, and the most widely used cast iron material is gray cast iron, which is used in machine bases, rolling and other places requiring vibration resistance and wear resistance. Ductile iron and white cast iron are used in places with higher comprehensive mechanical properties and higher wear resistance requirements, respectively. 3. In the structure of food machinery, in addition to the use of good metal materials, non-metallic materials are also widely used. The non-metallic materials used in food machinery and equipment are mainly plastics. Commonly used plastics are polyethylene, polypropylene, polystyrene, polytetrafluoroethylene plastics and phenolic plastics containing powder and fibrous fillers, laminated plastics, epoxy resins, polyamides, foams of various specifications, polyamides. Carbonate plastics, etc., in addition to various natural and synthetic rubbers. In the selection of plastic and polymer materials for food machinery, the materials that are allowed to be used should be selected according to the requirements of food media in health and quarantine and the relevant regulations of the national health and quarantine agency. In general, any polymer material that is in direct contact with food should ensure that it is absolutely non-toxic and harmless to the human body, should not bring bad smell to food and affect the taste of food, should not melt or swell in the food medium, let alone harm the food. Food produces chemical reactions. Therefore, it is not suitable to use low-molecular-weight polymers containing water or hard monomers in food machinery, because such polymers are often toxic. When some plastics are aged or operated at high temperature, such as high temperature sterilization, soluble monomers can be decomposed and diffused into the food, which can spoil the food.