The standard emphasized that in safety-critical loops, the feedback mechanism—the part that tells the control room if a valve is actually closed—must be ruggedized. The vibrating pipe had loosened a bracket that wasn't "API 553 compliant" for high-vibration zones. To the computer, the valve looked "partially open," causing the system to hunt and vibrate even more.
The standard emphasized that in safety-critical loops, the feedback mechanism—the part that tells the control room if a valve is actually closed—must be ruggedized. The vibrating pipe had loosened a bracket that wasn't "API 553 compliant" for high-vibration zones. To the computer, the valve looked "partially open," causing the system to hunt and vibrate even more.