A safety instrumented function (SIF) in a safety instrumented system (SIS) contains a sensor, logic solver and final element. All must function properly in the event of a safety demand to take the process into a safe state in coordination with other SIFs.
The final element consists of several parts including the isolation valve, actuator, pressure pilots, test valves and other components as required by the application. In this quick, 2:17 video, Introduction to Bettis PressureGuard Hydraulic Emergency Shutdown System, Emerson’s Sergio Vaz Lopes describes the elements of this self-contained, hydraulic Emergency Shutdown (ESD) system.
This ESD system provides reliable valve shutdown capability when an external power source is either not available or not dependable. These can be used with rotary hydraulic operators to provide a fail-safe system for use with ball, plug and other quarter-turn valves, as well as non-API 6A linear operated valves.
These PressureGuard ESD systems typically include a self-contained hydraulic module, a hydraulic actuator and application-specific shutdown triggers such as high- and/or low-pressure pilots, solenoid valves, and a temperature sensing fusible plug.
Examples of applications where these ESD systems are a good fit include oil & gas production wellheads, custody transfer points, and other SIFs where automatic valve emergency shutdown is required and external power such as compressed air, natural gas, or electricity is not readily available.
Under normal conditions, the PressureGuard system maintains the valve in its operational position by resisting the spring force with hydraulic fluid pressure. In a safety demand event requiring automatic ESD valve operation, the PressureGuard uses a control component to shift hydraulic fluid from the valve operator to an internal reservoir. Without fluid pressure, the compressed spring in the operator moves the valve to its shutdown position.
Visit the Bettis PressureGuard Hydraulic Emergency Shutdown System page as well as the Actuators section on Emerson.com for more on this and other valve actuator technologies to meet your requirements. You can also connect and interact with other final element experts in the Valves, Actuators & Regulators group in the Emerson Exchange 365 community.