A Caloris customer was experiencing overweight bulk bags off of their spray dryer operation. Some bags were 10 lbs overweight, but often they reached 30 to even 70 lbs over the desired weight.
Caloris sent a process engineer to troubleshoot the system while minimizing downtime. Our engineer determined that excess air was building up in the bulk bags during the fill operation, leading to the overweight loads.
The process engineer had to investigate several different culprits behind the excess air. Baghouse and silo pressure were eliminated as a cause. He next inspected the inflation fan and automatic block valve. Both were functioning normally, but he did note a new filter was needed as powder from the room was pulling into the fan and building up inside.
The magnet, pneumatics, rotary valves and fill head were also checked and cleared as potential causes.
One problem area was the automated vent valve — it was opening and closing fully, but its timing was off. The valve didn’t remain open at all times during filling. This prevented each bag from having enough time to “breathe” or deaerate. The timing of the system was adjusted and this change had an immediate impact on the amount of excess air in the bulk bag.
Our engineer also adjusted the fill sequence timing. He ran some timer trials to determine the best sequence for the system. Switching from the original fill cycle (initial fill – vibrate – final fill) to a new sequence with three fill and two vibration segments minimized the amount of overage to just 2-3 lbs, which was deemed acceptable.
These new changes still allowed for the fill cycle to complete within 10 minutes per bulk bag — faster than either spray dryer could supply powder to the packaging system.
While at the facility, our engineer interacted with several operators and learned new details about day-to-day system operations. For instance, the operators often changed the program parameters. He noticed how easily they were able to change the fill sequence times during his visit.
In his report to the customer, our engineer noted that these frequent system changes can lead to the original, optimal parameters of the system being lost.
“This ‘parameter creep’ can lead to what is likely today’s situation – many small changes and equipment wear over time have led to unoptimized operation,” he noted. He recommended that the programming be standardized and documented for optimal production results.
Our engineer’s report to the customer included operating recommendations for the plant staff to refer to along with several additional maintenance recommendations to further alleviate excess air content in the bulk bags.