The decision whether to use LIW or GIW scaling depends to a large degree on the particular set of circumstances, according to Bill Kearns, vice-president of engineering, Fred D. Pfening Co., Columbus, OH. “GIW is by far the most common and generally more economical method,” he said. “For instance, if multiple ingredients are to be weighed into a hopper, the GIW method allows this to be done with one set of load cells and electronic indicators and controls but has the limitation that only one ingredient can be scaled at a time. If it is necessary to weigh up faster, having each ingredient bin on its own scale allows all of them to feed simultaneously using the LIW method. However, the cost is greater with the LIW method since there are multiple sets of load cells and controls. With proper sizing of hoppers and scale equipment, good accuracy can be obtained with either method.”
LIW scaling systems are generally used in high-speed operations that are required to deliver a large number of batches per hour or where LIW feeders can supply a single collecting hopper simultaneously, noted Brian Ivkovich, senior vice-president, Zeppelin Systems USA, Odessa, FL. Also, LIW systems are typically used for continuous mixing systems where ingredients can be continuously metered into the mixer or a pre-blend of ingredients is used. Although it’s a slower process, a GIW system requires less maintenance for the single set of load cells and related electronics, he said.