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A tale of two plants: Using LOPA for SIL assignment
Author(s) -
Schmidt Michael S.,
Kilpatrick Dan
Publication year - 2012
Publication title -
process safety progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.378
H-Index - 40
eISSN - 1547-5913
pISSN - 1066-8527
DOI - 10.1002/prs.11477
Subject(s) - government (linguistics) , engineering , process (computing) , risk analysis (engineering) , chemical safety , operations management , forensic engineering , computer science , business , philosophy , linguistics , operating system
Two plants operated by the same company have “identical” ammonium nitrate (AN) solution pump installations. Yet the teams performing the layer of protection analysis (LOPA) concluded that the safety instrumented functions (SIFs) to protect those pumps needed different safety integrity levels (SILs). Despite the similarity of the installations, the teams discovered legitimate differences that warranted different conclusions about what SIL assignment should be. For those with a specific interest in AN, this article reviews the consequences of AN pump hazards, their initiating causes, and the types of independent layers of protection (IPLs) that can be brought to bear. Of more general interest will be the discussion of the impact of risk tolerance criteria, frequency modifiers, and IPLs on final SIL assignment, and why dictating a fixed SIL assignment to certain types of hazards or installations is inappropriate, especially in the development of industry standards or government regulations. © 2012 American Institute of Chemical Engineers Process Saf Prog, 2012