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Manufacturing feed pellets is a complex process in which a large number of raw materials have to be mixed together. This premix is then ground, and further additives are added before the dry components are thoroughly mixed again. To enable this mixture to be pressed into pellets, a substance such as molasses must be added to the dry ground mass. The final quality of the pellets depends on the precise dosage of this liquid. This is exactly where a 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 it can no longer be dosed precisely. At the feed manufacturer's plant, the molasses is delivered in lorries and transported via a long pipe system 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 metre 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 process had to be continuously controlled by the staff 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, Germany, has been working for the feed manufacturer for over 10 years. The company designs and implements automation solutions for a wide range of industries. The systems are installed in collaboration with Elektro Schütze. This provides customers with a one-stop solution for all automation aspects – from planning to software creation and the commissioning of process systems.
Autonomous pump control with the easyE4 industrial control relay and the XV100 touch display
Since the automation system that Elektro Schütze put together for the feed manufacturer consists almost exclusively of Eaton products, the company also opted for an Eaton solution for the temperature control 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 Elektro Schütze 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 a manual and an 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 variable frequency drive 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 the easySoft 7 programming software. This gives users the choice of four programming languages: The circuit diagram can be created using the function block diagram (FBD), the ladder diagram (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 using the function block diagram and ST.
Kai Bretschneider was impressed by how simple the configuration process was: "One of our younger employees took care of the programming, and he didn’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
The automatic temperature and fill-level control allows the temperature to be kept much more precisely within the desired range, so that 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 and 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
Our Solutions Partner Elektro Schütze has more than 20 years' experience in the fields of automation and control cabinet engineering. Its services cover planning, development, control cabinet design, the creation of software and process system commissioning for a variety of industries, including the food industry, hydraulics, material handling systems, pump control systems, marine engineering, building services engineering and power management technology.
