Chemical Processing-August 2008

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). PlAn 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 [1]. Planning ensures that work processes yield equipment that operates consistently, safely, 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 AIChE’s Center for Chemical Process Safety (CCPS) and for safety instrumented systems (SIS) in ANSI/ISA 84.00.01-2004 [3]. There is no substitute for knowledge [4]. 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 process hazards, technology and equipment provides the basis for sustaining internal process knowledge. A written design basis should define the PSI for safety equipment and should be traceable to process hazards analysis. For SIS, it is the hardware and software safety requirements specification [3]. Maintain it under revision control for the equipment life. Knowledge evolves over time. Real-world failures identify weaknesses in actual system performance. Hazard evaluation procedures [5] 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. Train personnel in process safety information associated with their work. They must also have the necessary skills and knowledge to follow procedures and properly execute tasks, so specify minimum levels for the job. When on-the-job training is needed, the program should address how the skills and knowledge are developed in a timely and safe manner and how progress is measured [2]. Finally, planning must consider security and management of change (MOC). Restrict physical and cyber access to the ISS using administrative procedures and physical means [2]. Independence assessments should consider data communication and human interface failures. Written procedures should address how to initiate, document, review and approve changes to ISS other than replacement in kind. Evaluate any change to the process and its equipment through a MOC process to identify and resolve any impact on the ISS requirements. do This phase implements systems defined in the Plan phase. From a project perspective, detailed engineering is completed, yielding an ISS installation that conforms to the design basis. Detailed engineering includes sufficient information to ensure the ISS is properly specified, constructed, installed, commissioned, operated and main33 chemicalprocessing.com august 2008 http://chemicalprocessing.com

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Chemical Processing- August 2008 Contents From the Editor ChemicalProcessing.com Field Notes In Process Energy Saver Compliance Advisor Protect your Plant What’s on Tap for Water? Keep Operations Safe Polystyrene Plant Gains Extra Output and More Process Puzzler Plant InSites Equipment & Services Adlits Product Spotlight/Classifieds Ad Index End Point

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