Safety Systems
Take No Risks: Implementing Safety Systems for the Process Industry
| Author / Editor: Manuel Keldenich* / Dr. Jörg Kempf
Many processes can reach a safety-critical state and thus become a risk. It is not only in the best interest of plant operators to take measures to reduce risks based on the current state of technology, in most cases they are even required to do so. Safety Instrumented Systems (SIS) play a significant role in this. Learn about a flexible and easy to scale stand-alone safety system that addresses specifically to customers who want to be able to reliably implement safety applications for small to medium-sized plants.
There is a universal rule that stands above every process optimization, energy saving, or productivity increase: the safety of people, environment, and plant is always number one. The bandwidth of risk potentials in process plants is wide and corresponding structural, organizational, and functional measures derive from them. They are supposed to reduce the overall risk to an acceptable residual risk level.
Systems from automation technology also have a safety role: SIS monitor potentially dangerous processes. When reaching an impermissible operational range, e.g. excess pressure in a boiler, these SIS autonomously regulate the process or notify the operating personnel. The entire cycle and the implementation of safety-related responsibilities are referred to as functional safety.
For more than 35 years, Siemens has been working in the area of functional safety and developing corresponding solutions. The comprehensive portfolio of safety-related products, systems, and solutions has now been extended with Simatic SIS compact. This standalone safety system consists of a combination of hardware and software components and serves as a dedicated safety system in small to medium-sized plant projects.
Analyzing Events in the Millisecond Range
In terms of hardware, Simatic SIS compact is based on the Controller CPU 410SIS, which is based on the CPU 410 developed for the process industry. It has 4 MB of main memory with very fast cycle times. In order to recognize safety-critical procedures, the system supports the Syslog network protocol for transmitting log messages.
A very precise time stamping mechanism serves to acquire and analyze the chronological sequence of events in the millisecond range. The Process Historian makes it possible to archive the OS data of an OS single workstation.
The hardware is designed for an operating temperature range of 0 °C to +70 °C and protected very well against environmental influences by a conformal coating. So the automation system can be used very flexibly and close to the process. Functional safety is ensured by the implemented safety functions of the software.
The system software package Simatic S7 F-Systems makes sure that safety-related and non-safe functions can run on one and the same CPU. With Simatic S7 F/FH systems as component of Simatic SIS compact, we can reach SIL 3 (Safety Integrity Level) pursuant to IEC 61508:2010.
Safety Systems Predestined for Critical Applications
Simatic SIS compact can be used anywhere where functional safety is key in the process industry. For instance, boilers, burners, or fuel-operated heaters pose a great number of safety-critical challenges in terms of operation, safety in case of impermissible operating ranges, or interlocks for start-up and shut-down processes. The stand-alone solution by Siemens makes it possible to run, monitor, and control such burner applications in the process industry safely and reliably.
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