Inherently Safer Design & Robust Protection Layers for High Consequence Hazards
Akshat Khirwal, Venkatesh Sourirajan
IRESC
Abstract
Reliance on standard protection layers which have been used commonly in the industry, on its own, may not be sufficient in all cases. Although these protection layers are believed to be adequate for existing facilities, a more detailed analysis in terms of adequacy of the safety design features and the protection layers may be required for new facilities. Using the examples of low temperature excursion hazards from LNG and ethylene plants where safety instrumented systems such as low low temperature trips are provided to safeguard piping and equipment against low temperature embrittlement, this paper looks into the need for further refinement of both likelihood and consequences of low temperature hazards, beyond what is traditionally done in SIL Determination workshops. It examines possible gaps in current approaches and assesses the benefits of a more detailed quantitative risk assessment approach for high consequence hazards that lack mechanical or other safety barriers besides a Safety Instrumented Function (SIF).