Importance of “SMART valve positioners” in testing of final control elements in safety instrumented systems application

Abstract

AbstractMany industrial facilities, especially those in the chemical and oil and gas industries, involve inherent risk in operations due to the processing of materials that may be hazardous in nature. It is therefore necessary to precisely identify and analyze these hazards, operability issues, associated risks, and consequences. Safety instrumented systems (SIS) are often used to reduce the risk associated with processes or plants to an acceptable or tolerable level. The reliability of safety function(s) implemented through SIS is dependent on how reliable the sub‐elements of the safety function, that is, sensors, logic solvers, and final elements, are. The final elements of such a SIS usually include the emergency shutdown valves, depressurizing valves, emergency isolation valves, and critical on–off valves. Since these final elements remain continuously open or are sometimes closed during the normal operation of the plant, it becomes a challenge to operate the final elements when there is a demand on the SIS. During an emergency, if these final elements fail to operate, this contributes to the dangerous failure of the plant, which may result in explosion, fire, or catastrophic damage to plant assets, environment, and personnel. Hence, it is essential to test these final elements frequently while in operation, without disturbing the operation of the running plant, to ensure that these final elements are available to perform their intended functions when needed. Smart valve positioners are one of the options among various methods available to test the final elements without disturbing the process. This paper evaluates the application, functionality, diagnostics, and advantages of SMART positioners in the testing of final control elements in a SIS application.