Marginal Column

To lead, we find new ways..


Dirk Bracht,
Senior Project Engineer,
Power Plant Engineering Bosch Rexroth in Germany

“If safety facilities are checked only once a year, we only know about their status during the past year. But the current safety status of the system is unknown—and that’s an issue that I thought needed solving ,” said Dirk Bracht, describing his -- and Bosch Rexroth’s -- approach to engineering effective safety systems.

As an engineer who originally specialized in power plant engineering with many years’ experience at Bosch Rexroth, Dirk Bracht is quite familiar with numerous technologies and industries… and he always keeping system safety in mind. After a recent on-site service at a power plant site, he had the idea of developing a safety system for power plant hydraulics that constantly checks itself. This system would include integrated software that intelligently and reliably indicate the sources of safety problems directly.

He explored and developed the idea with Rexroth colleague and hydraulic specialist Jürgen Finke along with a process engineer of the power plant operator: There had never been such a system, and who, if not Bosch Rexroth, could develop it?,” Dirk Bracht asked. Their common goal: a platform continuously keeping track of the system’s safety status.

Dirk Bracht and Jürgen Finke combined their application experience and expertise in control technology and hydraulics. The result: An innovative new solution, one which has been patented: the self-testing safety system (STSS). This system monitors itself for proper functioning and reports malfunctions immediately—which has actually helped improve power plant operational efficiency.

Without the STSS an annual emergency shutdown performed by the operators is needed to test the safety system. This procedure is required by regulatory guidelines governing safety systems. The process can be time-consuming and disruptive to operations. Using STSS technology, along with other system improvements, a formal emergency shutdown only needs to be conducted every six years, rather than annually. This saves enormous amounts of money and can increase the lifetime of the complete power plant equipment.

Originally developed for steam bypass systems in power plants, a wide range of potential uses for the STSS platform in other applications is supposable for applications in different branches.

“We have continued to refine the idea to develop a system which will still be effective in the future,” Dirk Bracht said. The newest version of the STSS platform will include a compact control unit that is manufactured by BOSCH, the latest digital hydraulics, customized safety blocks and sophisticated software to identify possible error sources and pass them on.

Safety technology needs to be certified by an independent entity, with a certification procedure performed on independent equipment. This certification is formally known as SIL3 (Safety Integrity Level) acc. to ISO 61508/61511. For SIL3 it is recommended that a certificate be obtained from an organization that has been accredited by a Member State of the European Union (such as TÜV, DEKRA, GL, etc.) accountable to assess whether a product meets certain preordained safety standards.

These certifications facilitate the entire acceptance process of the control system by our customer. As part of the certification procedure, the STSS solution and all engineering steps performed during the creation process are reviewed, approved and certified in accordance with SIL3.

Hence, the STSS is suitable to operate in a SIL3 safety system.

Rexroth associate Yinan Gu, with responsibility for product safety at the Quality Management and Methods department, supported the detailed certification procedure. This included ensuring the creation of the necessary documentation according to relevant standards and responding to and clarifying technical questions from the notified body conducting the certification.

The potential uses, in environments and applications where safety and safe functioning equipment is vital, continues to grow -- whether in the tropics, in the Arctic, in salt water environments, etc. “Technology needs to protect people and preserve the environment. That’s why we should never be satisfied with what is already available,” says Dirk Bracht. “There’s nothing more wonderful for an engineer than to make the world a little safer.”