SIL is an acronym for Safety Integrity Level, and is a system used to quantify and qualify the requirements for Safety Instrumented Systems. The International Electro-technical Commission (IEC) introduced the following industry standards to assist operators with quantifying the safety performance requirements for hazardous operations:
IEC 61508 Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems
IEC 61511 Safety Instrumented Systems for the Process Industry Sector
These standards have been widely adopted in the hydrocarbon and oil and gas industries as a means of improving safety and availability of Safety Instrumented Systems.