Inline Checkweighers FAQs

A:  A checkweigher is made up of a controller and a weigh frame. The weigh frame typically has 3 sections: Infeed, Weighing section, and Outfeed. The package being weighed goes through the following steps:

1. Package moves from the customer’s conveyor onto the checkweigher infeed
   a. Conveyor speed of infeed and weigh table are the same
2. Package is weighed on the weigh cell of the weigh table
3. Package moves onto the outfeed of the checkweigher to be accepted or rejected according to the checkweigher settings
4. Accepted package move onto the customers downstream conveyor
5. Ideal spacing between packages allows for a zeroing operation for maximum accuracy.

The packages are moved along by belt (motor), chain (uses motor to pull items forward), and/or skates (slider). If the measured weight does not meet specification, the product is rejected via air blast, pusher, bopper, diverters, or drop flabs.

A: Both food and non-food packages can be weighed on checkweighers, including: meat, dairy, wet and dry ingredients, baked goods, confectionary products, pharma, personal care packaged items, bullets, bags of construction materials like cement, etc. Types of items that can be weighed on a checkweigher include:

• Rigid (cans, cardboard packages, plastic, glass),
• Soft (plastic, paper, foil) ,
• Wet (dairy, hummus),
• Dry (rice, oatmeal), and
• Raw (chicken, beef, fish, vegetables and fruits).

It is worth noting that loose, continuously flowing product cannot be weighed on a checkweigher.

A:  It depends on the product being weighed and the checkweigher that is installed. Here are two examples: The Thermo Scientific Versa 8120 Checkweigher works with line speeds up to 550 rigid packages per minute. The Thermo Scientific Versa Frame 44HB Heavy Duty Weighframe is designed for rugged industrial environments with line rates up to 100 packages per minute (up to 300 fpm depending on package length).

A:  Proper design of the in-line checkweigher can influence accuracy. These are some of the design factors: 

• Product speed,
• Product weight and size,
• Product transfer onto and off of the checkweigher, and
• Reject method and design.

In addition, conveyors must be level and aligned, belts and chains should be inspected regularly for wear or product buildup, gaps between conveyors should be minimized and infeed and weigh table belts or chains should be running at the same speeds. Other factors include the spacing between products centers to ensure more than one product is not on the weighing table at any one time, and calibrations should be done regularly.

A:  The Thermo Scientific Versa Flex and Versa Flex GP Checkweigher line targets dry packaged applications such as baked goods, snack foods, prepared foods, condiments, pastas/rice/beans, baking ingredients (flour, sugar, etc.), personal care products such as diapers, soaps and creams, as well as pharmaceuticals.

A:  The Thermo Scientific Versa Rx and Versa RxV Pharmaceutical Checkweighers are specifically designed for pharmaceutical applications. These systems are highly accurate—within ±50mg at 3 sigma and speeds up to 550ppm. They have a clean design with a slack belt knife edge infeed transfer for unparalleled accuracy and optimal product handling. They are ideal for a variety of products, including blister packs, cartons, plastic bottles, glass bottles, pouches and small aerosols.

A:  The Thermo Scientific Versa Teorema Can Checkweigher is designed specifically for high-rate can weighing. A feedscrew properly spaces open or closed cans, steel or aluminum cans at speeds up to 700 cans/minute. The equipment includes side-to-side conveyor transfer capability at the in-feed and out-feed as well as photo-eyes to provide controlled feed of cans via a can-stop.

A:  Checkweighers can sometimes come in contact with food products that can leak or spill. The equipment has to get washed down regularly to prevent contamination so it must meet IP65 Washdown requirements. Therefore, checkweigher components require materials that can withstand washdown using chemicals. The metal should be fully constructed of ANSI Type 304 SS (stainless steel), which is an austenite steel. For even harsher situations, ANSI 316 stainless is used; it is more impervious to corrosion than 304 SS. Equipment should meet American National Standard ANSI/IEC 60529-2004 for equipment with electrical components. This standard describes a system for classifying the degrees of protection provided by enclosures of electrical equipment for two conditions:

1. The protection of persons against access to hazardous parts and protection of equipment against the ingress of solid foreign objects and
2. The ingress of water.

Equipment should be designed with minimal flat, horizontal surfaces and slots to reduce food buildup, and use stainless steel conveyor beds. IP65 enclosures provide basic waterproof protection from water, including jet sprays used during washdown.

A:  Checkweighers do not find physical contaminants but they can be combined with food metal detectors and x-ray inspection systems that do find contaminants. Food metal detection systems provide reliable, cost-effective protection from even the smallest metal contaminants found anywhere in a food production process. Food X-ray inspection systems provide protection from metal, glass, stone and other dense foreign objects for most any type of packaged, bulk, or piped product. Food manufacturers can find metallic and non-metallic foreign objects and eliminate “wet” product effects common with metal detectors with the Thermo Scientific NextGuard X-ray Detection Systems. Designed for a wide variety of food applications, NextGuard systems offer enhanced capabilities to inspect packaged products for missing pieces or components, under and over-fills, and other quality problems.