Teltek, based in Örebro, Sweden, develops, designs, programs and installs dynamic scales, primarily in the food and drink industry but also in other sectors like chemicals and hardware (weighing screws as part of the verification process). Virtually all the scales supplied by Teltek are tailored to meet customer requirements. The scale supplied to the fish factory was designed to sort incoming fillets of fish for packing in 400 gram units, at a rate of approximately 55 packs per minute. This is about what two people can manage when working at the conveyor.
Teltek dynamic scales for the right quantity of fish in the pack
HBM's intelligent load cells measure on the go when the production process cannot stop
Teltek makes process monitoring equipment for the food and drink industry and is the only Swedish manufacturer of dynamic scales, making them experts at weighing products as they move. They have just supplied a new in-house scale to a fish factory belonging to frozen food manufacturer Espersen in Lithuania. It will be an important part of the production line, ensuring that every pack of frozen fish contains the labeled quantity of cod, pollock or mackerel fillets – no more and no less. The job of HBM's load cells in the new scale is to guarantee accurate weighing despite the high production speed and the challenging conditions in the fish factory.
"For our customer – a fish producer – it is very important for the weight of the pack to be as close as possible to the labeled weight. If the weight is too high, the producer stands to lose a lot of money. And if packs are under weight, they may be in conflict with directives of the Swedish National Food Administration", explains Tomas Moqvist, MD at Teltek.
Rapid sorting and weighing
Digital load cells are the key
Teltek's approach involved six parallel buffer plates on each side of the scale, with room for a total of twelve fillets that have passed through the two fish sorters. A combination of fish fillets is selected to come as close as possible to the target weight of 400 grams per pack. The central components of the machine are the six digital HBM PW15AHi single point load cells, with a pneumatic motor to advance the belt.
"Obviously, the primary function of the machine is weighing, but a lot of thought went into how the fish is handled and transported – this is a delicate raw material that can easily fall apart. We clearly want to keep waste to a minimum", says Tomas Moqvist, who has learned a lot about raw fish during the project.
Unlike many other scales, in which Teltek uses a combination of analogue load cells and in-house filters, the decision was made to use digital load cells in the new fish scale. As a result, a certain amount of intelligence could be built into the load cells directly, for example signal filtering functions.
Dynamic weighing is a big challenge
Communication and data transmission from the machine is based on the standard serial interface protocol, RS485. The scale is operated from a user friendly touch screen next to the machine. The underlying computer program and the algorithm controlling the choice of fish fillets for each pack were developed in-house by Teltek. The program tests all the various combinations of the 12 fish fillets on the scale, selecting the best match for each pack. The whole process takes about a second, using a lot of computer power.
"Most load cells on the market are intended for static applications. High speed dynamic weighing is a different ball game. HBM is the only manufacturer who is talking about dynamic features in load cells, and also the only one putting so much effort into product development relating to dynamic weighing. It's important for us to work with a manufacturer who is at the cutting edge", explains Tomas Moqvist.
Handling the rough stuff
The wire strain gauges in the load cells are sensitive to moisture, so they need to be designed to withstand the challenging conditions in the fish factory, where the machinery is cleaned with a strong jet of water several times a day. The load cells are therefore made of stainless steel, and installed in a protected box that is kept under pressure to repel moisture.
Aiming for reliability
It's a big problem if the machine stops working. More fish arrive on a daily basis, and they need to be processed. Reliability and ease of maintenance of the components are crucial. "The HBM load cells we use in the fish scale have the highest level of moisture protection, IP68. The original load cells in one of the first fish scales to be delivered worked perfectly and are still going strong after two years of demanding double shifts. We've done some fine tuning in the new machine, and we're aiming for reliability that is at least as good", says Tomas Moqvist in conclusion.
- Makes process monitoring equipment for the food and drink industry
- Experts in dynamic weighing
- Founded in Örebro 1982
- Thousands of checkweighers installed with customers
- First in Sweden to receive type approval for a dynamic scale (1993)
To find out more go to www.teltek.se
- The PW15AHi is a digital single point load cell with maximum protection (IP68)
- Designed for use in checkweighers, filling and packing machines and multihead weighers
- Hermetically sealed
- Made of stainless steel
- Suitable for environments with high pressure cleaning
- Cable protection available
- Digital load cell with RS485, CANOpen and DeviceNet interfaces