Actuators for Oil & Gas

SIL (Safety Integrity Level) is a measure of reliability of a safety function as defined in IEC 61508 (functional safety of electrical/electronic/programmable safety systems) and IEC 61511 (safety instrumented systems for process industry). For ESD actuated valves: SIL 2 means the probability of failure on demand (PFD) of the complete safety instrumented function (SIF) — which includes the sensor/transmitter, logic solver, and final element (valve + actuator) — must be between 10⁻³ and 10⁻². SIL 3 means PFD between 10⁻⁴ and 10⁻³. The actuated valve assembly (valve body + actuator + solenoid + limit switches) is the final element of the SIF loop. For an actuated valve to be SIL 2 certified, a SIL assessment (FMEDA — failure mode, effects, and diagnostic analysis) must demonstrate that the valve assembly's failure rate is compatible with achieving a SIL 2 PFD budget. For a typical ESD valve: SIL 2 is standard for most process plant fire & gas trips and emergency isolation systems; SIL 3 is required for critical applications such as wellhead wing valve ESD on high-pressure, high-H2S wells, or main flame arrester inlet isolation at LNG terminals. Vajra supplies complete SIL-assessed ESD valve packages with TÜV-reviewed FMEDA reports for SIL 2 and SIL 3 applications.