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Calibrated Risk Graph Method

Last updated: October 29, 2017

What Does Calibrated Risk Graph Method Mean?

The calibrated risk graph method is used to determine the requirements of the safety integrity levels (SILs) in process industry installations.

As per the IEC 61511 technical standard, also known as Functional Safety—Safety Instrumented Systems for the Process Industry Sector, this method is described as a semi-qualitative method. However, other practitioners describe this method as semi-quantitative.

Safeopedia Explains Calibrated Risk Graph Method

This method is one of two popular methods used to determine SIL requirements. The other method is known as layer of protection analysis (LOPA).

The calibrated risk graph method has several advantages including the following:

  • It is both semi-qualitative and semi-quantitative. i.e. No specialist calculations are required.
  • It is normally applied as a team exercise similar to HAZOP, meaning individual bias can be avoided.
  • It does not require a detailed study of relatively minor hazards.
It is important to note that the risk graph must be calibrated on a conservative basis in order to avoid the danger that the results underestimate the unprotected risk and the amount of risk reduction/protection required.

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