SIS Design Basis Revalidation - Since the time of the original release of ANSI/ISA 84.00.01, a lot of process industry users have made great strides at updating and improving their safety instrumented system (SIS) implementation practices to be in conformance with the standards.  Even so, some control system practitioners and loss prevention specialists are beginning to question the validity of both the design basis documentation that has been developed and the ability of the installed equipment and management systems to meet those targets because of process changes and erroneous initial assumptions.    Because procedures are not always followed and mistakes occur, the regulators and the standards writers have included provisions in their respective guidance documents to periodically go back and review prior hazard analysis studies and design basis documents to ensure that they are still valid.

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Hydrocracker Reaction Safeguarding - Emergency depressuring of Hydrocracking process units in refineries received a large amount of attention after some catastrophic accidents.  Many refiners decided that automatic depressuring of the unit when excess temperature was detected should be a safety instrumented function and replace the traditional manual depressuring.  When attempting to implement the ISA 84.01 safety lifecycle, refiners found that applying this safety instrumented function is quite difficult in terms of risk analysis to determine the required safety integrity level (SIL).  This white paper discusses the selection of a SIL for the depressuring function.  The Hydrocracking process is of great interest in terms of SIL selection because of the advanced methods that are required to provide reasonable results.

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Safeguarding Oxidation Reactions - Reactions which oxidize hydrocarbon feed stocks to create chemical intermediates are extremely common in the process industries.  These processes involve a number of hazards that can be effectively controlled by the use of safety instrumented systems.  This white paper discusses typical oxidation processes, describes hazards that they pose, presents a history of accidents from oxidation reactions, and provides an overview of some typical safety instrumented functions that are employed on oxidation reactions with typical equipment configurations.

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