Modern waste water treatment plants encompass many processes whereby each of them must be optimised in terms of process engineering, energy efficiency and reliability, demanding flexible and outstanding performance capabilities within automation engineering. The Erlangen sewage treatment plant (Bavaria, Germany) was erected in 1957. Today, it supplies 270,000 inhabitants and was only recently subject to comprehensive modernisation to satisfy increasing demands and regulations. The equipment of the manifold valves with actuators and their integration into the new process control and communication system was a crucial issue. Reliability of plant operation played a significant role and was integral part of the decision making process.
For communication within modernised plant sections, the plant operator had decided in favour of PROFIBUS since this fieldbus technology is renown for perfect service reliability within the water/sewage water sector. Furthermore, a large variety of field devices are available supporting PROFIBUS technology. AUMA actuators of modular design on mission at most different valves are integrated. They are equipped with a uniform PROFIBUS interface and RS 485 transmission physics. One PROFIBUS master (S 7) each in altogether seven decentralised plant segments controls up to 90 actuators.
PROFIBUS DP fieldbus technology used throughout the plant is responsible for transmitting process data as well as values of status monitoring contained within the actuators. For future requirements, PROFIBUS DP offers enhancement by additional acyclic communication allowing adaptation of device settings and request of diagnostic and status signals during operation.
PROFINET is the backbone for connecting controls via fibre optic technology.
PROFIBUS DP is the foundation of the new automation solution. Clear plant segmentation as well as high and stable data transmission rates of up to 1.5 Mbit/sec are of considerable benefit for the plant operator. Low space requirements in control cabinets as well as the option of acyclic communication enhancements are of significant use. This results in a high operation reliability with considerable future potential while reducing operating costs. "We are very content with our automation solutions and the outstanding reliability of AUMA actuators", the plant operator confirms.