Issue link: https://www.e-digitaleditions.com/i/1325722
50 / January 2021 powderbulk.com STOPPING METAL CONTAMINATION, IMPROVING PRODUCT PURITY, AND ELIMINATING RECALLS The responsibility for a clean end product is shared by both bulk solids processing plants and their suppliers. Every participant throughout the process must ensure foreign contaminants aren't present in the end products that companies deliver to their customers. This article discusses the best practices used today for achieving the highest product purity and avoiding costly damage from tramp metal. Eric J. Confer, Eriez material stream continues down the process line and the drawn-out contaminants are disposed of when the magnet is cleaned. There are a variety of magnetic sep- arator types, including drum, plate, pulley, tunnel, and tube, some of which are shown in Figure 1, and each comes with its own advantages and disadvantages, depending on the application. As the name suggests, a metal detector detects metal contaminants entering a speci c piece of equipment, such as a pipe, conveyor, or chute, as shown in Figure 2, and then activates a rejection mechanism to remove the intruding particle from the stream. Metal detectors also come in a variety of styles, such as tunnel, gravity, P roduct purity — ensuring your end product is free of any ferrous contamination — is achieved by incorporating magnetic separators and metal detectors into your bulk solids process. In this system, both the separator and detector locate the ferrous mate- rial, but the separator draws the ferrous material out of the process via magnetism, while the detector uses a rejection mechanism to remove the ferrous contami- nation. The magnet in the separator is chosen based on a number of factors, including the magnet's pull force (or highest possible holding power) in relation to the ferrous contaminants needing to be picked up and the material's properties, temperature, and owrate. But incorporating one magnetic separator and one metal detector into your process isn't suf cient enough, as ferrous pieces can slip by the rst magnet, and ensur- ing your material is clean shouldn't be a one-time occurrence in your process. This article discusses the relationship between mag- netic separation and metal detection, the importance of emphasizing product purity and equipment protection from your receiving dock to the shipping department, and why engaging in continuous training to stay updated on material safety regulations and process improvements is essential. Magnetic separation and detection Magnetic separators use magnets and a magnetic eld to separate ferrous material from nonferrous mate- rial. As the material is conveyed past the permanent magnet — a magnet that creates its own continuous magnetic eld, the magnet's force draws the ferrous contaminants out of the material stream. The cleaned Grate-in-housing Liquid B trap Liquid B trap (with different port) Grate Tube Tube Liquid L trap Plate FIGURE 1 These magnets work for a wide range of applications, including dry bulk materials and high-temperature applications.