How Falling Stream Sampling Systems Work
Falling Stream Samplers come in all manner of shapes, sizes, and configurations, but regardless of the machine in question, the basic function of this type of machine is essentially the same. A sample cutter is parked on one side of a moving material flow. When a sample increment is to be collected, the cutter drive assembly (which varies by machine type) will move the cutter through the material flow at a constant speed, collecting a sample increment.
For diverter type cutters (i.e. sample material is directed from the material flow to another area), the sample increment is directed into a sample discharge area of the sampler where it is either collected for offline use or passed into the next piece of equipment installed in the sampling system. Once the cutter clears the material flow, the sampler drive stops the cutter on the opposite side of the material flow. The next increment is collected by moving the cutter back in the direction of the first parked position.
If the sampler in question has a bottom dump type cutter, the sample cutter will pass through the moving material flow at a constant speed, collecting material inside it. Once the cutter reaches the other side of the material flow, the cutter will open to release this material back into the main flow. The cutter will then pass back through the material flow, collect the sample increment, and stop back in its original parked position and empty the sample increment into a discharge chute. Material is then collected for offline use or directed to the next machine in the sampling system. It is also important to note that some bottom dump samplers may have a sample discharge point on both sides of the material flow. In this case, the operation would be as described with the diverter type cutter.
Falling Stream Sampler drive units vary by machine type but are usually one of three types of drives. These are gear-reducer driven rack and pinion, gear-reducer driven chain and sprocket, and hydraulic cylinder.
Regardless of cutter or drive type, the basic, simple operation and reliability remains the same.