By Topic

Safety Achieved by the Safe Failure Fraction (SFF) in IEC 61508

Sign In

Cookies must be enabled to login.After enabling cookies , please use refresh or reload or ctrl+f5 on the browser for the login options.

Formats Non-Member Member
$31 $13
Learn how you can qualify for the best price for this item!
Become an IEEE Member or Subscribe to
IEEE Xplore for exclusive pricing!
close button

puzzle piece

IEEE membership options for an individual and IEEE Xplore subscriptions for an organization offer the most affordable access to essential journal articles, conference papers, standards, eBooks, and eLearning courses.

Learn more about:

IEEE membership

IEEE Xplore subscriptions

2 Author(s)
Yoshimura, I. ; Tokyo Univ. of Marine Sci. & Technol., Tokyo ; Sato, Y.

The present paper examines the effect of safe failure fraction (SFF) constraints on hazardous-event rates, and discusses the validity of the SFF constraints in IEC 61508. First, the safe states are categorized into three types of states, and overall systems involving safety-related systems are classified into six types of systems based on the safe-state categorization, and the completeness of trips. Next, state-transition models for the systems where the effect of SFF is the greatest are presented, and the hazardous-event rates are analysed for the systems. Then, it is found that, when the effect of the SFF constraints is positive, it is negligible; and when it is negative, it is not negligible for safety. Thus, we recommend that the application of the SFF constraints to the standard should be put on hold.

Published in:

Reliability, IEEE Transactions on  (Volume:57 ,  Issue: 4 )