By Karen Mills, director of quality assurance, High Liner Foods Inc.
Food inspection systems using state-of-the-art technologies are most successful when they are designed with many support methods and principles. I've written articles on how this is true with metal detection technology, X-Ray inspection machines, and vision inspection systems. This article will explore checkweighing systems, how they add support to food safety methods and principles, and the benefits implementing them can provide food manufacturers.
Checkweighing is not a quality or safety fix-all, but it is a conduit to report on processes within the plant lines. Checkweighers can be an effective tool in conjunction with a well-designed safety and/or quality program. With proper maintenance and periodic testing, the checkweighing system can ensure no off-weight or incomplete packages reach your customer or end users.
Checkweighers can be used in the agricultural sector, packaging manufacturing, pharmaceuticals, as well as the food industry. They are used in cleanrooms, dry-atmosphere environments, wet environments, produce barns, food processing facilities, and drug processing facilities. Checkweighers are chosen by the kind of environment, and the kind of cleaning that will be required and applied.
How Does It Work?
Product passing over the checkweigher platform is controlled by its electronic console. When triggered by the scale eye, the control weighs and classifies each item. From there, it will divert or eject off-weight items from the line.
Some of the first, more-simple checkweighing machines were designed in the late 1950s into the mid-1960s and the technology has continued to progress and improve until present day. Checkweighers today can be built with metal detectors, x-ray machines, open-flap detection, barcode scanners, holographic scanners, temperature sensors, and vision capability.
Most modern checkweighers are generally equipped with communications ports to enable the actual package weights and derived data to be uploaded to a host computer. This data can also be used for managing production information which enables processes to be fine-tuned and production performance monitored on a real-time and on-going basis.
An industrial motion checkweigher can sort products from a fraction of a gram to many, many kilograms. In English units, this is from less than .01-oz, to as much as 500-lbs or more. Specialized checkweighers can weigh commercial aircraft, and even find their center-of-gravity.
There are two different types of checkweighers: static scales or in-automatic, in-motion checkweighers. The key differences lie with how they can be approved (via repeatable and verifiable weights and measures certification proving their degree of accuracy). No matter the type, checkweighers must be accurate to read weights within a fraction of a second. Sourcing the right checkweigher is key to the product and process it is required for.
Facilities need to take into account four main considerations when choosing the type of checkweigher for their use:
- Environment - as per the image, dry, wet. humid, cold
- Accuracy needed
- Run rates needed per product type
- Package type
Checkweighing machines can be designed in many shapes and sizes, hung from ceilings, raised on mezzanines, and can be operated in ovens or in refrigerators. Their conveying medium can be industrial belting, low-static belting, chains (similar to bicycle chains, but much smaller), or interlocked chain belts of any width. They can have chain belts made of special materials, different polymers, and metals.
Checkweighers can also be used to count the packages going through production lines. They can report on the total weight, total number of packages, and can also read the labels with vision inspection systems. They will reject all non-compliant packages and also redirect the packages according to package labelling. As with other inspection systems, any of the above applications can save manufacturers time and money. Further, and perhaps even more critically, checkweighing helps avoid potential product withdrawals, fines, or other critical and costly regulatory actions.
Possible uses for a checkweigher include:
- Checking for under and/or overweight filled packages
- Insuring compliance with net contents laws for prepackaged goods
- Checking for missing components in a package including: labels, instructions, lids, coupons, or products
- Verifying count by weight by checking for a missing carton, bottle, bag, or can in a case
- Checking package mixes against weight limits to keep the solid to liquid ratio within established standards
- Reducing product giveaway by using checkweigher totals to determine filler adjustments
- Classifying products into weight grades
- Insuring product compliance with customer, association, or agency specifications
- Weighing before and after a process to check process performance
- Fulfilling USDA or FDA reporting standards
- Measuring and reporting production line efficiency
A perfectly good checkweigher will still allow off-weight packages to continue along the line if the zone ranges/limits are not set properly. Production and quality personnel need to understand the acceptable weight limits per the relevant regulations. From there, ensure the equipment is programmed to be within the required tolerance limits.
The traditional "minimum weight" system, where weights below a specified (or declared) weight are rejected. Normally, the minimum weight is the weight that is printed on the packaging of the product being inspected. It can also be a weight level exceeding the specified weight to allow for any losses after production, such as evaporation of commodities that have a moisture content.
Larger wholesale companies have mandated that any product shipped to them have accurate weight checks so a customer can be confident they are getting the amount of product for which they paid. These wholesalers charge large fees for inaccurately filled packages.
Keep Your Checkweighers Running Smoothly
To ensure a checkweigher is running to its optimal potential, it should be included in a preventive maintenance (PM) and cleaning program. Some checkweigher manufacturers offer a PM contract to help support and keep the systems running at their best.
There are many environmental factors that can affect a facility's check weighing systems, including:
- Moving air
- Extreme temperatures
- Equipment abuse
- Floor vibrations
- Static electricity
- Moisture and wash-downs
An effective checkweighing system, in conjunction with other inspection system components, or designed with the other systems within it, will work 24/7, performing 100 percent online inspection, resulting in improved product quality yields, lower production costs, and reduced if, not eliminated, weight and measures regulatory non compliances. For all industry players, continued consistent product appearance and quality as well as proven food safety, as well as clear integrity in all aspects, drives customer satisfaction, protected company branding and ultimately market share.
About The Author
Karen Mills is Director of Quality Assurance for High Liner Foods Inc. (Canada) and operates out of High Liner's processing facility in Lunenburg, Nova Scotia. She leads teams that are responsible for internal food safety and compliance, as well as supplier/ vendor import and regulatory compliance. She and her team members work corporately with other High Liner facilities based in the U.S. Karen received her B.Sc. in Animal Science from the Nova Scotia Agricultural College in Truro, Nova Scotia.