LOPA and SIS/SIL Defined

Effective risk management always involves some type of hazard assessment process, which is designed to determine if adequate protection layers are in place to bring the risk to an acceptable level. There are many ways to perform this activity with varying degrees of complexity and effectiveness. The assessment methods range from qualitative (subjective) to quantitative (detailed, numerically intensive and time consuming). Layer of Protection Analysis (LOPA) was introduced to bridge the gap between the two extremes.

A safety instrumented system (SIS) is an “instrumented system used to implement one or more safety instrumented functions, composed of any combination of sensor(s), logic solver(s), and final element(s)”. These functions have a common attribute - to reduce risk. Independent Protection Layers (IPLs) are safeguards used to mitigate the process risk. The quantity of risk reduction is specified by an order-of-magnitude level called the safety integrity level (SIL)

Value of LOPA

Facility siting allows you to identify possible risks to personnel, equipment, structures and surrounding areas from fire, explosion and toxic substances. OSHA process safety management regulations require facility siting assessments as part of a comprehensive process hazard analysis.

  • How bad is it?
  • How much protection is needed?
  • What type of protection is needed?

LOPA answers all of the above questions in a risk-based approach which is usually part of a PHA performed by a team. LOPA is used in compliance with IEC 61511/ISA 84 standards. IEC 61511/ISA84 requires the allocation of safety functions to layers of protection and to determine the Safety Integrity Level (SIL). LOPA is one method that can be used for selecting the appropriate SIL of your Safety Instrumented Systems.

Experienced Professionals

ioMosaic has a proven track record of performing LOPAs. Our professionals have performed assessments on a wide range of facilities, such as refineries, chemical plants, pharmaceutical plants, tar sands, crude oil refineries, LNG facilities, and rail and marine transportation terminals. Let ioMosaic help you make risk-based decisions with confidence.

LOPA Tools

ioMosaic uses the state-of-the-art software tool, Process Safety Office® component PHAGlobal® to conduct LOPAs. PHA Global has all the functionality necessary to conduct a LOPA. ioMosaic has conducted a number of LOPAs and understands the importance of reliable, consistent data.