Safety Integrity Level

Safety Integrity Level (SIL) is defined as the relative risk-reduction provided by a Safety Instrumented Function (SIF). In simple terms, SIL is a measurement of performance required for a SIF. In the European Functional Safety standards based on the IEC 61508 standard, four SILs are defined, with SIL 4 being the most dependable and SIL 1 being the least.

A SIL review is a method that enables a team to define this requirement, based on relevant criteria and analyses.


The SIL reviews’ objective is to provide the SIL target for all SIFs within the scope of work.

When necessary the SIL team can also suggest actions to optimize the process, investigate further scenarios, or even reduce the required SIL.


HazOptima provides high quality HAZID reviews based on very effective leaders to head up the HAZOP team.

Our chairmen are highly experienced and completely focused on HSE reviews, having both a Safety and a Process background. This ensures a broad and extensive knowledge of the given industrial context that enables us to guide the team in order to find out the optimized solution.

Our goal is to ensure the proper procedure for the relevant review at the best time.

Our services deal with SIL reviews preparationfacilitatingreportingfollow-up and training.

We are able and experienced in working with any and all industries where HAZOP can be applied.

HazOptima provides high quality HAZOP reviews based on very effective leaders to head up the HAZOP team
Our References

“I will recommend HazOptima.”

Process Specialist
UOP A Honeywell Company

“One of the most detailed HAZOP I have ever attended.”

Process Engineer

“Adaptive, pro-active, HazOptima gives envy to go to HSE reviews. Go on!”

Project Engineer

“People from HazOptima were really efficient during the review. Planning has been respected and even challenged. Discussions with Chairman and rest of the team were constructive and no time was spent on internal meeting. Scribe was very efficient.”

Process Engineer

What is the result of a SIL review?

The SIL review is the written record of the requisite SIL regarding the analyzed Safety Instrumented Functions. The report shall include the full list of SIL targets, with the assumptions and what the analysis is based upon. In addition, the report shall include the list of actions recommended or mandatory to achieve an acceptable level of risk in an optimized way.

HazOptima reports include a clear and exact recording of discussions raised during the review, as well as actions list and dedicated action sheets for easier response and follow-up.

We employ the main software available on the market when carrying out our reviews and more specifically HAZOP Manager developed and produced by Lihou Technical & Software Services.

What is the basic methodology of SIL reviews?

In few words, the SIL methodology is the following one:

  • the SIFs are listed and fully described (design intent, initiating elements, final elements),
  • for each SIF, the related scenario is reviewed based on a former risk analysis (e.g. HAZOP), to define all potential initiating causes, consequences and existing safeguards,
  • the team determines, using four semi-quantitative parameters, the severity and likelihood associated to the scenario,
  • the team defines the required SIL for the SIF under review, based on Risk Graph Analysis.

For more information please contact us.

What do you need to perform SIL reviews?

SIL reviews take place when the HAZOP analyses are completed. They are based on P&IDs (Piping and Instrumentation Diagrams), Cause & Effect Charts or other documents. HazOptima helps you to define the requisite documentation dependent upon your constraints and objectives.

What is the scope of SIL reviews?

Scope of SIL reviews can significantly vary depending on your objectives, project phase and information availability. HazOptima helps you to define the best procedure including scope of work, rules and planning.

How long do SIL reviews take?

Depending on the number of Safety Instrumented Functions in the scope of work, SIL reviews could take from one day to several weeks or months. HazOptima can help you to define your planning at an early stage in the project.

For more information please contact us.


  • IEC EN 61508 (Functional safety of electrical/electronic/programmable electronic safety related systems),
  • IEC 61511 (Safety instrumented systems for the process industry sector),
  • Other references: do not hesitate to contact us.