Accidents continue to happen because too many owner/operators still use injuries and fatalities as the predominant metric for safe operation. This focus on direct impact can lead to acceptance of loss of containment events and tolerance for latent weaknesses in process safety management (PSM). Knowledge of gaps in equipment integrity and management systems shouldn’t depend on catastrophic events. Injuries and fatalities should occur so infrequently that impact data are meaningless for trending performance.
Accidents often occur when equipment is improperly designed, installed, operated, tested and maintained. Adequate theory and standards are available to ensure safe operation of process equipment. The problem isn’t bad people and lack of competency — it’s that the systems governing equipment integrity aren’t rigorous enough to ensure the required reliability.
A plant must use a rigorous quality management system to sustain equipment reliability; otherwise, accidents will occur when enough latent conditions in equipment, procedures and personnel training accumulate. It’s essential to take a proactive approach — not just monitoring for behaviors, errors and failures that are known root causes for process safety incidents but also identifying improvement opportunities to counter this accumulation and minimize risk.
This demands a comprehensive risk reduction strategy, one that relies on a wide variety of safeguards to prevent releases of highly hazardous chemicals. Here, we use the Shewhart Cycle — with its Plan, Do, Check and Act phases — to introduce the various activities involved in achieving safe operation using instrumented safety systems (ISS).
W.E. Deming believed that 85% of a worker’s effectiveness is determined by the system he works within, only 15% by his own skill . Planning ensures that work processes yield equipment that operates consistently in a safe manner, fulfills government and jurisdictional requirements, and meets recognized good engineering practices. The output of planning is a management system of policies, practices and procedures that seeks to identify and control releases of highly hazardous chemicals. Recommended work practices and activities are provided for instrumented protective systems in “Guidelines for Safe and Reliable Instrumented Protective Systems”2 by the Center for Chemical Process Safety (CCPS) and for safety instrumented systems (SIS) in ANSI/ISA 84.00.01-20043.
There is no substitute for knowledge4. Only a small amount of knowledge can prevent mistakes leading to process hazards. Unfortunately, many owner/operators are losing process knowledge and history as operators and technical staffs retire or simply leave for better jobs. Errors accumulate unless there’s continuous analysis and improvement of safety practices. Counteracting loss of expertise as well as equipment degradation through age and obsolescence requires significant effort.
Written process safety information (PSI) covering the process hazards, technology and equipment provides the foundation for sustaining internal process knowledge. A written design basis should define the PSI for the safety equipment and should be traceable to the process hazards analysis. For SIS, the design basis is the hardware and software safety requirements specification3. It should be maintained under revision control for the equipment life.
Knowledge evolves over time. Real-world failures identify weaknesses in actual system performance. Hazard evaluation procedures5 used periodically throughout the equipment life pinpoint and evaluate significant events involving abnormal process operation. Analyze qualitatively or quantitatively the event risk to determine the causes and potential frequency of occurrence. Then implement independent protection layers to ensure that failures or errors don’t compromise safe operation. When the residual risk exceeds the owner/operator criteria, establish additional administrative and engineered safeguards to reduce the risk below the criteria.