28 May 2013
The field crop business is a seasonal one. During high season, exceptionally large quantities have to be processed in a short time and so the new potato sorting plant was designed to process up to 120 tonnes of potatoes per hour. This process starts with the farmer delivering his potatoes to the collection point. The harvested potatoes are poured through a hopper and onto conveyor belts which lead to the ‘stone and clod’ separator, where unwanted material is removed. Next comes a presorting stage where potatoes that are too large or too small are removed and passed on to the feed bunker. After soil is removed from the remaining potatoes, they reach the sorting machine that uses vibrating screeners to separate them into seven categories according to size. Here, they are manually examined in order to remove any bad ones. They are then washed, dried and polished before being transported to various bunkers that each hold 40 tonnes. Depending on the means of transport required, they are next weighed and bagged in nets, or loaded directly onto the truck as loose items. “When the agricultural company approached us to ask for support with a new project, we were attracted by both the capacity of the plant, as well as the complex challenges with regard to the required level of automation”, explained Sebastian Gormanns, founder and CEO of Schaltanlagen Gormanns. “We were given the task of getting the plant running correctly and on time, as well as ensuring a simple operation for everyone. Apart from that we were given a free hand.” The project required 250 drives for conveyor belts, pumps, fans and machines. Gormanns estimated that at least 32 km of cable would have to be laid for the entire plant, with at least 1km of additional of cable for the conventional cross wiring within the switchboards. Faced with this situation, Gormanns decided to use Eaton's SmartWire-DT connection and communication system. Instead of the individual wiring connection of switchgear, sensors and actuators to the central controller, SmartWire-DT enables the components to be connected directly with a single cable. It provides the individual slaves with power and, at the same time, implements the data communication. Thus, all stations in the system can communicate. A Profinet, Profibus-DP or CANopen gateway can be used to connect the system with the higher-level controller to enable data exchange via various fieldbus connections and controllers. “Eaton provided us with a demonstration case so that we were able to thoroughly test the system over a week”, said Gormanns. “We not only tested the technology, but also its openness for the PLC systems and components from other manufacturers. After completing an in-depth analysis I was convinced. I knew that the potato sorting plant would be an ideal project to fully utilise the benefits of SmartWire-DT.” The switchboard consists of a central unit with nine sections as well as a substation with four sections. Profibus is used as the fieldbus system via which the PLC, frequency inverter and touch panels communicate with each other. Motor starter combinations networked with SmartWire-DT handle the switching and protection of all 250 drives. These are connected by section to the PLC with one gateway per section, and consist of motor-protective circuit-breakers, contactors, and electrical connectors from Eaton's standard product range. Schaltanlagen Gormanns chose PKZ motor-protective circuit-breakers that are matched to the DIL contactor series. These switch drives in the sorting plant with operating currents of between 3 and 10 A. The drive concept of the plant also consists of laser sensor controlled conveyor belts, suspended from the roof from where they efficiently fill the bunkers. Each belt learns which belt comes next and automatically switches itself on and off. Some of the motors in the plant are reversing drives whilst others are pole-changing drives. These can also be easily integrated in SmartWire-DT. Eaton's communication system is not only used in the switchboard but also in the periphery. Schaltanlagen Gormanns also connected over 50 command points at the machines via SmartWire-DT. The plant owner requires only one operator for the entire plant, who switches it on, and selects between some programmes, such as for setting the potato size, defining routes or selecting or deselecting the washing operation. The rest of the plant that was successfully put into operation in May last year is fully automated. “I have to admit that I was initially skeptical about whether SmartWire-DT could actually do what it promised”, confesses Gormanns. “But I can now say with conviction that the installation was completed without any problems and that I have seldom seen anything so simple”. The savings that could be made in cabling are enormous: “For us, the wiring requirement has been reduced to one-eighth of what it normally would be. Thanks to SmartWire-DT the cross wiring has been reduced from 1km to 50m, and the cabling required for the control circuit devices on the machines has been reduced by approximately 40%. Troubleshooting has also been reduced as faults can be found quickly due to the high level of data transparency of the connected stations. Instead of the two weeks required for commissioning our previous sorting plant project, we only needed 1.5 days with this project. We were thus able to successfully implement this complex project in only four months. I am looking forward to the next opportunity for us to work with SmartWire-DT”.
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