THERMO RAMSEY:   Loss-in-Weight Feeder

The Continuous Loss-ln-Weight principle involves weighing the entire feeding system (hopper, feeder, and bulk material) by means of a static type scale system, and controlling the discharge feed rate of the bulk material by means of a variable speed motor.

The Continuous Loss-ln-Weight principle involves weighing the entire feeding system (hopper, feeder, and bulk material) by means of a static type scale system, and controlling the discharge feed rate of the bulk material by means of a variable speed motor. Material is discharged from the system, via screw or vibratory tube or tray, with the measured "loss in weight" per unit time (dv/dt) compared to the desired (set) feed rate. The difference between the actual (measured) rate and the desired (set) rate produce a corrective action by the feed rate controller (Micro-Tech 2104), which automatically adjusts the feeder speed, thus maintaining accurate feed rates with no process lag. When the measured weight in the hopper reaches the hopper low (refill) level, the controller affixes the feed system into volumetric control. The hopper is then quickly recharged (manually or automatically), and the Loss-ln-Weight control action repeats. In a Batch Loss-ln-Weight System, the design is similar to a Continuous Loss-ln-Weight System. However, the accuracy of the final weight at the end of the feed (batch) cycle is typically more critical than the actual feed rate control. The Micro-Tech 2104 Controller accomplishes this by providing a high feed rate signal to the variable speed drive for quick filling and then switching to a low feed rate control signal for precise, fine control at the end of the batch

Benefits:

• Handles hot, floodable and difficult materials.
• Unaffected by dust and material accumulation.
• Well-suited for low feed rate applications.
• Entire system is weighed. No errors from belt tensioning or tracking.
• No transportation lag time exists, which ensures precision second-to-second accuracy.
• Feed accuracy can always be checked during normal operation without the need for sampling.