The Harmony of Alchemy and Automation

Our aim was to implement a holistic, low-maintenance and reliable automation system that offers us a high level of flexibility for modifications. This has been achieved.
- Martin Schäfer Heimerle + Meule

In Pforzheim, a lot goes on that has to do with gold. Its nickname "Goldstadt" or "Golden City" is based on the fact that Pforzheim has been renowned worldwide as a center for gold, jewelry and clock making since as far back as the 18th century. This was where Germany's oldest gold and silver refinery Heimerle + Meule was founded in 1845. The company's core expertise is in the recovery of highly pure fine metals from residues containing precious metals. The base material used consists of waste or residues coming from production processes such as in the jewelry and clock-making industry, in dental laboratories and in electronics production. The precious metals that are recycled with state-of-the-art and environmentally-friendly technology are fed back into the processes of different sectors that process precious metals. The company further treats the materials as required, such as in the form of alloys, semi-finished products, salts and solutions. Today Heimerle + Meule GmbH is the holding company and is responsible for the operations of the Heimerle + Meule Group, a full-range supplier in the precious metal processing sector with over 700 employees.

At its Pforzheim headquarters, around 120 t of metal waste can be processed every year. Most of the recovered material is silver and gold. Platinum metals are also extracted.

“Our processes are based on the principle of electrolysis,” explains Wolfgang Schäfer, head of productive recycling at Heimerle + Meule. “The aim is to refine the metals to as pure a form as possible, for example, with gold this means a quality of 999 parts per 1,000, for silver 997 parts per 1,000. This makes the material suitable for most applications.” The base material cast into anodes is subjected to an electrolytic process in heated baths over a long period. With silver extraction any unwanted metals can be separated from the anode and dissolved in this way leaving the pure silver remaining. Gold is subjected first of all to an initial separation in a similar way. In the second step, the refining, it is dissolved in the electrolysis bath and separated on the cathode plates.

In order to ensure that only the required materials dissolve and consolidate, and to ensure the high quality of the target material, these processes firstly require the correct adjustment of the chemical processes and concentrations involved and also the control of important variables such as temperature, current and voltage.

“In 2012 an extensive area of our plant was damaged by a fire,” recalls Martin Schäfer, responsible electrical supervisor at Heimerle + Meule. “We saw this as an opportunity to develop a new automation concept for our important extraction processes. We wanted this to be in line with the latest state-of-the-art technology, to offer us reliable protection from operating errors as well as a high level of user-friendliness.” At the same time Schäfer was faced with the challenge of completing the entire reconstruction project in only three months from installation and programming, right through to commissioning.

The Pforzheim specialists called on the support of Eaton for the planning and implementation, since their technology had already been successfully in operation on site for many years. The automation concept is based on six HMI/PLCs of the XV-102 and XV-152 series. These monitor and control the processes of washing, preseparation of silver and palladium, refining of gold, gold preparation in gold salts (potassium gold cyanide) and the separation for recovering platinum and palladium.

For this, the HMI/PLCs communicate via Eaton's innovative SmartWire-DT connection and communication system with switchgear such as the PKZ motor starters, the DIL contactors or the DS7 soft starter, as well as various control circuit devices of the RMQ Titan series. All drives for pumps and stirrer motors up to 4 kW for the baths are equipped with motor starters, and all over 4 kW with soft starters or variable frequency drives (PowerXL DC1). The network can currently connect around 300 SmartWire-DT devices. A key benefit: SmartWire-DT eliminates the need for any complex and errorprone point-to-point control wiring of components with the central controller, provides a high level of data transparency and helps to increase system availability. The technology impressed electrical specialist Schäfer immediately: “Given the complexity of our system, the benefits that SmartWire-DT offers are enormous, particularly with regard to the reduced cabling effort and the diagnostics features possible.”

He can now access all HMI/ PLCs centrally via Ethernet from his PC and see for example if each connected device is operational. The controllers communicate with each other and monitor each other. The data exchange is so active that the IT department has created a separate Ethernet network for the system. At Heimerle + Meule, the many analog signals that were previously regulated by hand, such as fill levels, bath temperatures, as well as current and voltage values applied to the electrodes via rectifiers are collected on the XI/ON modular I/O system. The XI/ON modules are connected directly to the controllers via the CANopen bus. The air exhaust and supply of the plants that was previously regulated by the easy800 control relay could also be integrated easily into the network via easyNet and the CANopen interface of the HMI/ PLCs.

“Thanks to the ‘green ribbon of hope’ as I like to call it, we were able to complete our project within the short time frame available,” a delighted Schäfer states. “With a conventional system we would have needed at least a month just for the wiring. With SmartWire-DT we had all the components installed in just a week. Troubleshooting became unnecessary since there were never any faults.”

For the master electrician, it was also important that he could learn the Codesys-based programming of the HMI/PLC quickly. The Galileo design tool enabled him to create simply and quickly the visualization for the operating levels of the processes as well as a remote desktop client. Using only one application on his computer, The HMI/PLC visualization is programmed simply and conveniently via the Galileo design tool Touch panel PLCs (HMI/PLCs) are in operation for a wide range of processes throughout the entire refinery. These communicate with around 300 components via SmartWire-DT Schäfer is able to keep all essential components in view and make targeted interventions in the event of a fault without having to go to the particular location for troubleshooting, as was previously the case. The project and the high level of process automation enable Heimerle + Meule to minimize the risk of fire and operating errors in the plant.

“Our aim was to implement a holistic, low-maintenance and reliable automation system that offers us a high level of flexibility for modifications. This has been achieved.” Schäfer sums up. “Flexibility is an important factor for us since technical modifications to the plant were regularly required over the course of the project and also today. The automation based on Eaton's technology, such as SmartWire-DT, enables us to implement hardware and software adaptions quickly and effectively. We are currently considering how we can extend the SmartWire-DT network to other processes.”