Batching system considerations

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Gain-in-weight versus loss-in-weight batching systems: what are the pros and cons? Jessica Stank offers expert guidance on selecting the appropriate batching system for your needs.

Selecting the right batching system for your needs can make a huge difference in your ROI and efficiency. There are different factors to consider in gain-in-weight versus loss-in-weight configurations for batching systems, including cost, accuracy, speed, and downtime.

Let’s dive into their differences, as well as the pros and cons of each batching system.

What is a gain-in-weight or GIW batching system?

A gain-in-weight batching system utilises multiple feeders to dispense into a single scaling vessel or container. The vessel or container typically uses load cells to measure the weight of the entire batch of dry ingredients as they are dispensed.

The vessel or container is sized and designed based on a total maximum batch capacity for the ingredients assigned to the scale. It is called gain-in weight because it is measuring the weight
of the ingredients as they enter the tared empty vessel, giving you the correct overall total weight for your batch.

For example, on a gain-in weight micro ingredient scale, the individual ingredient bins will each dispense into a scale on load cells. Once the total batch weight is achieved, there is a transfer of those ingredients to the next step in the batching process, whether that is into a mixer or some other piece of equipment.

What is a loss-in-weight or LIW batching system?

A loss-in-weight batching system uses a scale as a part of the ingredient storage hopper. As the ingredient is dispensed into an independent vessel or container, the weight loss is totalised until the desired amount has accumulated.

The storage hopper is sized and designed based on total maximum ingredient capacity required. For example, on a loss-in-weight micro ingredient scale, each individual ingredient bin is mounted on load cells. This measures the exact amount being dispensed on a per-bin basis.

Pros and cons of GIW versus LIW

The pros and cons can be divided into four major categories:

  • Cost
  • Accuracy
  • Speed
  • Downtime

Analysing each category will assist in determining which system is best for your process. Balancing these categories is key to making the right choice.

So, what are the pros and cons of each option?

GIW pros & cons

Pro: Low cost. Because only one feeder runs at a time, electrical hardware used for controls can be shared between ingredient bins. Common components reduce the need for a large inventory of replacement parts. You should always request that the manufacturer use components readily available in your area.

Pro: Accuracy and storage balance. Scales can be designed to higher accuracy standards due to reduced capacity requirements based on the formula’s ingredient usage for a single batch.

This reduces the need for constantly refilling storage bins by increasing capacity to a size that fits the process.

Con: Downtime on hardware failure. Major electrical components – such as VFDs and scale indicators – used in operating the GIW system are shared. Failure of one will influence all the feeding devices.

Con: Speed. Cycle time is determined by the number of feeders assigned to the gain-in-weight scale. The more ingredients assigned to a scale within the formula, the more run time will be required to complete the batch.

LIW pros & cons

Pro: Speed. An LIW system allows for each feeder to have its own feeding devices and controls. This reduces time spent scaling a formula since all ingredients are scaled simultaneously.

Pro: Reduced downtime due to a single component failure. Downtime is minimised or eliminated when ingredients are stored in multiple bins and a failure occurs in the scale or feeding device.

Con: Cost. Additional components – such as load cells and controls hardware – are required to allow feeders to operate independently.

Con: Accuracy. The accuracy of the LIW system is dependent on the storage capacity required by the user. High-capacity storage bins require high-capacity scale components. You will need to carefully review load cell specifications to ensure that they meet the accuracy desired.

So which system is right for you?

There are additional factors that may influence your choice of batching system.

Maybe you have plenty in the budget for the additional cost of a loss-in-weight system but have determined that speed is not a priority.

What if accuracy is more important than speed, yet you like the added benefit of the ingredient bins being on load cells for inventory reconciliation?

Or, what about tight budgets with fast cycle rates, extremely accurate dispenses, and the highest reliability equipment on the market?

Determine what is most important to your application, consult the experts, and get references from the manufacturer for equipment in the same industry as your own.

Jessica Stank is with APEC.

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