With the gradual improvement of the global requirements for the safety of food metal detectors and the hygiene and quality of exported foods, in order not to damage the good quality image and company reputation established through years of hard work, preventing metal foreign objects from being mixed into food products becomes quality management Must topic in.
It is not uncommon for the brand effect of the company's products to drop sharply due to the incorporation of metal foreign bodies. If you want to restore it, you must work harder. Once it reaches the stage of litigation, huge litigation and compensation costs are likely to occur; in addition, if metal foreign bodies are mixed in and cause damage to high-end production equipment, not only equipment damage will occur. Repair costs will also cause various wastes in production.
Although there are strict management procedures in the production process, and corresponding protective measures have been taken to prevent the incorporation of metal foreign objects, they cannot be completely ruled out. Metal mixing caused by raw materials, such as residual broken needles in meat, nails, fish hooks, staples mixed in powdered raw materials, etc.; man-made causes, such as buttons, coins, keys, rings, necklaces, etc., Forgotten screwdrivers, nuts, screws, welding slag, inadequate cleaning of metal shavings, etc. caused by on-site repairs in the production site, as well as engineering in the workshop, such as equipment aging and falling rust, old defective pieces, The parts on the conveyor belt, the broken pieces of the stainless steel screen, the slicer and the crusher blades, etc. are the culprits of the metal mixing (the author once provided a metal detector service for a tea factory. During the test, all the finished products were not acceptable. Through the inspection of the metal detector, the safety officer of the tea factory repeatedly claimed that the tea could not contain metal scraps. Later, after unpacking part of the finished product and trying it with a magnet, a large piece of iron scraps similar to tea was discovered. , The tea is inevitably used in a large iron pan during the processing process, the iron pan is rusted over time and caused by metal foreign bodies mixed in).
Traditional integrated metal detector
How to detect these metals mixed into products? The earliest huge magnet placed above the food conveyor belt is the prototype of the metal detector. When the metal foreign matter in the product flows on the conveyor belt, it can be attracted by the strong attraction of the needle detector magnet, but its limitations Sex can only detect metals that are inherently magnetic. Therefore, metal detectors with more perfect performance have been well used with the improvement of detection requirements. Its main detection object is metal. Metals are roughly divided into three types, namely ferromagnetic metals, non-ferrous metals and stainless steel. The difficulty of detection is determined by the permeability and conductivity of the metal itself. If it is ferrous metal itself, it has magnetic properties and good electrical conductivity, so it is easy to be detected; if it is copper, lead, aluminum and other non-ferrous metals, although they are not magnetic, they have good electrical conductivity and are relatively easy to be detected; There are many kinds of stainless steel products, some are magnetic and some are not, and the conductivity is also different.
304 and 316 stainless steel products are most commonly used in the food industry, so their lowest sensitivity is often used as the main detection range of metal detectors. At present, most metal detectors are integrated detection coils. Because of their relatively good stability and sensitivity, they are also widely used.
Three coils of the same size and parallel to each other are fixed on a non-metal frame in a special way in the detection head of the integrated metal detector. A coil in the middle is connected to a high-frequency generator to generate a high-frequency magnetic field; while the other two coils are used as coils to receive high-frequency magnetic fields. Because they are equal in magnitude and opposite in direction, the generated voltages cancel each other out, and the signal voltage output by the coil is 0. The detection coil has high-sensitivity electronic balance. If metal passes through the detection head, it will disturb the balance of the magnetic field, causing a number of small changes in one coil, and the entire balance is broken. This phenomenon is used to detect the presence of metal. The above is a brief description of the detection principle of the integrated metal detector.
There are many factors that affect the detection sensitivity, including the type, shape, and size of the metal, the direction of entering the detection channel, the size of the detection coil and the surrounding environment, and so on. Although the metal detector is a very good detection equipment, there are also detection drawbacks behind its excellent detection performance. For example, it is greatly affected by the product's own factors, such as product temperature, salinity, and product temperature. The packaging form, etc., at the same time, due to the factors of the detector itself and the actual use environment, etc. also have an impact on the detection. The above all greatly restrict the detection sensitivity of the metal detector, and also give users the detection of foreign metal objects. The above caused a lot of trouble.
High-performance X-ray inspection equipment x ray inspection equipment
In order to better implement high standards of hygiene and quality control, X-ray foreign body detectors, which were previously widely used in the field of medical and safety inspections, have also begun to better perform their outstanding detection capabilities in food inspection.
The reason why x ray inspection equipment can be accepted by the food industry is inseparable from the superior performance of the x ray inspection equipment needle detector maintenance itself. When the object passes through the X-ray detection area, the object is irradiated and penetrated by X-rays, and receives residual X-rays of different intensities on the linear sensor. At the same time, the linear sensor converts these signals into data signals and transmits them to the image. The processing unit, and then the image processing unit processes the signal, converts it into a video signal, and sends it to the monitor. The operator can see the condition of the object when it passes the inspection on the monitor. If the tested product is mixed with metal or other relatively dense foreign matter, its ability to block X-ray penetration is also different. The dense object will hinder the X-ray penetration, while the low density object X-rays are relatively easy to penetrate, which means that the intensity of X-rays after penetrating the object is different. When you see the product on the monitor, there are images with different brightness and darkness. At the same time, the X-ray foreign body detector is It can automatically identify foreign objects in the image.
Using the strong penetrating power of X-rays and the principle of imaging, it can not only detect fine metal particles or fine lines that cannot be detected by metal detectors, but also detect non-metallic foreign objects that are not recognized by heavy-duty needle detectors. (Such as glass, stone, hard bone, hard plastic, rubber, etc.), which solves the trouble of mixing other non-metallic foreign objects in the user's product to a large extent, and makes the user's product quality have a new improvement. Not only that, the current X-ray foreign body detection machine also uses the shielding function to detect various foreign bodies in the metal canned product and the defective product detection function to detect the damage or lack of the product. These functional characteristics are all metal detection machines. Unmatched. In addition, in the inspection mode of the X-ray foreign body inspection machine, the world's first genetic algorithm (GeneticAlgorithms) technology is applied to the X-ray image processing, which is more effective and comprehensive for foreign body detection, making food more secure and safer. I believe that in the near future, more high-tech methods will be used in the metal detection industry to cope with the increasingly stringent quality and continuous improvement of laws and regulations.