Stein Hauge, Mary Ann Lundteigen, Per Hokstad and Solfrid Håbrekke
2009-12-18
97 sider

PDS is a method used to quantify the safety unavailability and loss of production for safety instrumented systems (SIS). The method accounts for all types of failure categories; technical, software, human, etc.

This report presents an updated version of the PDS method. Among new features are:

• A general review and update of the methodology and the formulas, including a more in depth discussion of the assumptions underlying the formulas;
• An update of the model for common cause failures (CCF) in multiple redundant systems;
• A discussion on the use of the method for continuously (high demand mode) operating systems;
• Some new and revised terminology.

IEC 61508 and IEC 61511 have become important standards for specification, design and operation of safety instrumented systems in the process industry. The PDS method is in line with the main principles advocated in these standards, focusing on the quantitative aspects of the standards.