Choosing the right dry-solids feeder for an application can be a challenging undertaking. Arming yourself with the necessary information can ease the task and ensure that the proper equipment selection is made.
Initially, system parameters must be carefully defined. This includes identifying the materials to be metered, their bulk densities, and their individual handling characteristics (whether they are free flowing, adhesive, cohesive, pressure sensitive, etc.). The feed-rate range (minimum, nominal, and maximum) must also be clarified. Before the proposed feeder is sized, consideration should be given to future feed-rate requirements. Accuracy requirements must also be established. This dictates whether a volumetric or loss-in-weight feeder is required for the application. As a system component, a feeder’s performance can and will be affected by the other equipment in the system.
Careful consideration should be given to how the material will get to the feeder and to the type of device into which the feeder will discharge. For example, the feeder may be refilled manually, with a pneumatic conveyor, a mechanical conveyor, a live-bottom device (such as a vibratory bin bottom), or a static hopper. Such equipment can cause material fluidization, densification, or degradation, influencing product characteristics and feeder performance. In the discharge phase, the feeder may meter material into a conveyor, blender or mixer, extruder, or pneumatic system. Such devices can generate heat, positive or negative pressures, or moisture, all of which can affect feeder performance and end-product quality. An obviously crucial system parameter is feeder location. Also, equipment width, length, and height may be limited or restricted. And machine selection can be affected by the feeder environment (whether it is indoors, outdoors, temperature controlled, etc.).
Once prospective buyers have gathered all the necessary information, they can properly evaluate potential equipment suppliers. This step should start with a visit to several vendors. If possible, buyers should witness materials tests. All too often, feeders have a lower acquisition cost than other equipment. This factor, coupled with diminishing travel budgets and time constraints, results in vendor evaluations that are not as comprehensive as they should be. Testing product in a production-size piece of equipment (scaled-down tests are sometimes misleading) can prevent complications and production losses during installation. To ensure a proper comparison, test parameters such as equipment size, feed rate, sample duration, and refill frequency (for loss-in-weight feeders) should be the same for all manufacturers. Site visits can also give buyers insight into manufacturers’ capabilities. They can be learning experiences—especially for buyers who are relatively new to the industry and to the process of selecting equipment.
During the evaluation stage, buyers should also address several other concerns: equipment reliability and versatility, warranties, maintenance and service requirements, and factory support—including whether the manufacturer offers parts and service 24/7. These are especially crucial concerns for production lines that operate around the clock, where downtime can cost thousands of dollars per hour.
Paul Matarazzo is senior mechanical engineer/manager in the materials testing facilities at Acrison Inc. (Moonachie, NJ). He also serves as an internal consultant on the selection and application of the company’s range of dry-solids metering, hoppering, and blending equipment. An employee of the company for 31 years, he previously served as a project engineer and an applications engineer. Matarazzo is the coauthor of two international mechanical patents held by Acrison.