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An auger is a vertically oriented section of spiral flighting that rotates within a section of pipe. The bottom end of the flighting projects out of the tube slightly and has a wear-resistant cutting head that loosens material to be sampled and directs it up into the bottom of the auger tube. Sample material then travels up the auger tube until it reaches the top. If the full auger increment is to be collected, the material is diverted from the top of the auger tube into a sample collection hopper, which is installed on the side of the auger. If the auger increment is to be split, the material passes from the top of the auger tube and through a fixed splitter, where the reject portion falls back into the material being sampled. The save portion is collected in the auger sample hopper.
Once an auger increment is collected in the auger sample hopper, the auger is maneuvered to a sample receiving hopper. This receiving hopper is either the point at which final sample collection occurs or it acts as the entry point to any subsequent sample processing equipment incorporated into the system. The orientation of the remaining portion of the system varies by application but generally will include secondary (and possibly tertiary) sampling and rejects handling. Sample crushing is also sometimes included depending on the application.
Bulk materials that are frequently handled include coal, coke, crushed ores, metal and non-metal concentrates, salt, potash, wood pellets and other dry bulk materials.
In an ideal situation, bulk materials are mechanically sampled from a moving material flow. Examples of ideal sampling locations include on a moving belt conveyor, free-falling in a vertical chute, or as material is discharged from a conveyor at a transfer point. In actuality, however, this is not always possible and other means of sample collection must be used. The most common example of this situation is where material to be sampled is confined in some type of container for transportation purposes.
Bulk materials are frequently transported via truck, rail, or other container, and often there is no other option for sampling other than to collect samples from the transport container, particularly in as-shipped and as-received situations. These are the types of applications to which auger sampling systems are well suited.
McLanahan offers a wide range of Auger Sampling options from basic, manually operated primary auger sampler station to more fully automated multi-stage systems. The key components that distinguish these types of systems from other sampling systems are the auger itself and the device used to maneuver the auger. Three standard auger sizes are available from McLanahan, 12” (305mm), 20” (510mm) and 24” (610mm), all of which meet the needs of most common applications. Augers can retain the complete auger increment, but they are also available with integral sample splitters. These sample splitters can reduce the total amount of material collected by the auger by predefined ratios, commonly 6:1 or 4:1, but the actual ratio can be customized based on application. Auger maneuvering options include basic vertical auger motion, manually controlled hydraulic crane, partial motion auger gantry, and full motion auger gantry. Augers and auger sampling systems can also be designed as permanent stationary systems or semi-portable units that can be partially disassembled and relocated.
Once primary sample increments are collected by the primary auger sampler, processing those increments is the same as any number of other multi-stage sampling systems for which McLanahan has become well-known. What makes auger systems unique is that they are nearly always customized in some way to meet a client’s application requirements. Tailoring sampling solutions and customizing system layouts and equipment to meet a client’s specific needs is an area in which McLanahan excels.
While a properly designed auger-based sampling system can yield acceptable sampling results, it is generally preferred to collect samples from a moving material flow. Examples of this would be sampling from a falling stream (vertical or trajectory type) or from a moving conveyor belt (cross belt type). This is primarily due to the concept of equiprobability. This concept is a staple of sampling theory and states that all particles in a given consignment should have the same probability of being selected for inclusion in the final sample. This is the case with falling stream and cross belt-based samplers — all material must pass by or through the sampler. It is not necessarily the case with auger sampling, as a sample auger simply does not have access to all particles in a consignment of material. An example of material that an auger would not have access to would be the corners or bottom of a truck bed or railcar.
Sample augers are incorporated into a wide variety of applications but are most frequently used to sample transport containers for bulk materials.
