The Incident:
During an operational push at a regional gas fractionation plant, an automated safety-instrumented system (SIS) continuously tripped a major reciprocating compressor due to high vibration signals. Believing the sensor was faulty and facing significant production pressure, the operations team bypassed the interlock loop to keep the unit running while waiting for a maintenance window.
Hours later, the vibration—which was caused by an actual catastrophic mechanical failure of a compressor piston rod—sheared the casing. The ensuing release of high-pressure gas flash-ignited, destroying the compressor bay and fatally injuring two nearby field operators.
[Mechanical Defect] ===> [Vibration Spikes] ===> [SIS Interlock Bypassed] ===> [Casing Shear / VCE]
(Cultural Failure)
CCPS Element Integration: Conduct of Operations & Safety Culture
- The Normalization of Deviance: The CCPS emphasizes that bypassing a safety interlock should never be treated as a routine task. When production targets systematically outweigh process safety discipline, a dangerous cultural shift occurs where warnings are treated as nuances rather than hard operational boundaries.
- Dynamic Risk Blindness: Bypassing a safeguard fundamentally alters the baseline risk profile of the unit. CCPS guidelines mandate that a temporary bypass must trigger an immediate, dynamic risk assessment to determine if the asset can safely run in a degraded state, including restricting physical personnel access to the high-hazard zone.
- Operational Readiness: If an interlock is bypassed, strict administrative protocols—such as continuous local monitoring or manual remote trip standby—must be established instantly.
Labels: Conduct of Operations, Interlock Bypass, Safety Culture, CCPS