Smart valve positioners and their use in safety instrumented systems

As part of efforts to reduce life cycle costs of control valves in the process industry, smart electropneumatic positioners play an important role due to their self-adaptive features and their highly developed diagnostic functions. Their use can lead to decisive improvements in availability and reliability. To make full use of this potential, which has often been discussed in theory in the past but hardly been put into practice to date, NA-MUR Recommendation 107 and Guideline VDI 2650 provide information on the scope of diagnostics and the generation of alarm states. Applications in safety instrumented systems are of particular interest as smart positioners are used more and more with on/off valves in place of classic solenoid valves. In the process industry, the use of on/off valves in safety instrumented systems is governed by the IEC 61511 standard. The basic principle behind this stan-dard is the safety management life cycle, which can be effectively supported by the diagnostic functions of positioners.