(75a) You Got LI-PL!

Instrumentation and controls (I&C) play a significant role in preventing process safety incidents. I&C are used to implement safety alarms, interlocks, burner management systems, emergency shutdown systems, fire and gas systems, and other critical safeguards to stop hazardous event propagation. Ensuring the reliability of I&C can be challenging due to the large number of devices that need to be tracked and managed to ensure that they do the job they need to do when called upon. To address this challenge, the International Society of Automation (ISA) 84 committee has issued a series of standards and practices over the last 30 years covering how to assess, design, operate, and maintain I&C in process safety applications. ISA 84 standards on instrumented safeguards and safety instrumented systems (SIS) are well-known, and many companies have adopted specific work practices to address their requirements.

An emerging standard, ISA 84.91.03, builds upon guidelines published in the CCPS LOPA, CCPS IPS, CCPS IE/IPL, and CCPS Safe Automation books and covers the lifecycle management of what has been referred to as a basic process control system (BPCS) protection layer. Since the term BPCS is often confused with the control system, the new standard uses the term low integrity protection layer (LI-PL) to cover any instrumented protection layer that is not expected to provide performance equivalent to a SIS but is needed to provide risk reduction. This new standard will significantly impact current industry practices, from identifying LI-PL during the process hazards analysis through monitoring their installed performance. This paper will provide an overview of draft ISA 84.91.03 to raise awareness of the new standard's requirements and discuss its impact on typical process industry practices.