Using LOPA to Understand Necessary Safeguards for Steam Boiler Operation

Most chemical process plants, petrochemical facilities, and electrical power utilities rely upon steam boilers to provide motive power, electricity, and process steam for operations.  Safe operation, start-up, and shut-down of these boilers requires many levels of operational/controls safeguards.  The design and selection of safeguards is often guided by the original design of the boiler, equipment manufacturers, internal company standards, and recognized authoritative standards.  In the United States, the National Fire Protection Association (NFPA) has promulgated NFPA 85 The Boiler and Combustion Systems Hazards Code.  This prescriptive code identifies necessary safeguards along with “listing” and “labeling” requirements for some components used as safeguards; however, the Safety Integrity Levels for the multiple safeguard systems have not been quantified.  In this paper we use Layer of Protection Analysis (LOPA) methods along with generally-accepted probabilities and frequencies of failures to provide a quantitative framework for an owner, operator, or manufacturer to use in designing or evaluating the multiple safeguards necessary for safe steam boiler operation.  As part of the analysis, we have provided case studies of boiler failures with a discussion of how additional layers of protection may be either ineffective or missing.