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Manufacturing feed pellets is a complex process in which a large number of raw material components have to be mixed together. This premixture is then ground, further additives are added, and all the dry components are mixed thoroughly again. To enable this mixture to finally be pressed into pellets, a substance such as molasses must be added to the dry ground mass. The final quality of the pellets is dependent on this liquid being dosed precisely. This is exactly where one manufacturer of feed for horses, cows, chickens and rabbits was repeatedly running into problems.
Challenge: Fluctuating temperatures make dosing molasses more difficult
The temperature of the molasses must be kept within a relatively narrow range. If the temperature goes outside this range, the consistency of the liquid changes and the liquid can no longer be dosed precisely. At the feed producer's plant, however, the molasses is delivered in trucks and transported via a long system of pipes to the main tank, where it is finally mixed with the dry mass. Since the molasses cools while flowing through the pipes and therefore risks becoming too viscous, the manufacturer had already set up a tank with a capacity of around 1 cubic meter as an intermediate buffer for the molasses. This tank is filled via a pump. A heating circuit and a cooling circuit, each operated by a separate pump, keep the temperature of the liquid in the tank within the desired range. These pumps were previously controlled manually. This required staff to control the process continiously and was very time-consuming; it also caused the temperature of the molasses to fluctuate too much. Some batches had to be reprocessed and some even had to be discarded entirely.
Elektro Schütze, based in Stockelsdorf (Ostholstein), has been working for the feed manufacturer for over 10 years now. The company designs and implements automation solutions for a wide range of industries. The systems are installed in collaboration with Elektro Schütze Meisterbetrieb. This provides customers with a one-stop solution for all aspects of automation - from planning to software creation through to commissioning of process systems.
Autonomous pump control with easyE4 industrial control relay and XV100 touch display
Since the automation system that Elektro Schütze put together for the feed manufacturer consists almost entirely of products from Eaton Elektro Schütze also opted for an Eaton solution to control the temperature of the buffer tank. "As the application was going to be a local solution, i.e. not connected to a higher-level controller, we decided to use the easyE4 control relay," says Kai Bretschneider, managing partner of Elektroschütze Automations GmbH. "The easyE4 can do everything a small PLC can, but it's far more cost-effective. It offers all the performance and functionality we need for this application."
The user interface offers manual mode and automatic mode. In automatic mode, pump P1 is controlled by fill level FS1. Pumps P2 and P3 are controlled by temperature sensor TS1. This sensor ensures that the temperature inside the tank stays within defined limits. In manual mode, the operator can set the frequency of the frequency converter and start the pumps individually. Valve V1 can be opened and closed regardless of the operating mode.
The control system for the buffer tank was set up using easySoft (version 7) programming software. This gives users the choice of four programming languages: The circuit diagram can be created using function block diagrams (FBD), ladder diagrams (LD), Eaton's own `easy' programming language EDP or by means of structured text (ST). ST is commonly used in automation and includes additional features for more complex applications. Elektro Schütze created the main program in ST, and the sub-programs as a functional block diagram and ST.
Kai Bretschneider is impressed by how simple the configuration process is: "One of our younger employees took care of the programming and he doesn't have any prior experience with the easyE4. Even so he got the system up and running in a very short time."
Result: No more defective batches
Controlling the temperature and fill level automatically makes it possible to keep the temperature within the desired temperature range much more precisely, meaning the molasses retains the optimum consistency for dosing. There have been no issues with defective batches since. "The combination of the easyE4 and the XV100 touch display provides a fast, cost-effective, complete solution for simpler automation projects," says Kai Bretschneider. "Exact specifications and settings can now be configured via the display and the values can be monitored visually."
Eaton's Solutions Partner for the application
Eaton's Solutions Partner, Elektro Schütze, has more than 20 years' experience in the fields of automation and switchgear cabinet engineering. Its services cover planning, development, switchgear cabinet engineering, software production and process system commissioning in a variety of industries, including food industry, hydraulics, material handling systems, pump control systems, nautical engineering, building services engineering and power management technology.
