Know Your Onions

We’ve been commissioned to develop a set of cards based on the Initiating Events (IE) and Independent Protection Layers (IPL) from the AIChE – American Institute of Chemical Engineers CCPS LOPA Book (Layer of Protection Analysis: Simplified Process Risk Assessment) which has been industry best practice for over 20 years.

The following references have been operationalised & visualised to aid stakeholder understanding and recurrent engagement i.e. not just frontline personnel who interact with hazards & protection measures but also those who are responsible for their implementation, modification & oversight.

  • Initiating Events (Table 5.1)
  • Passive IPLs (Table 6.3)
  • Active IPLs (Table 6.4)
  • Human Action IPLS (Table 6.5)
  • Probability of Ignition (Figure 7.1)

Table 5.1 concludes with the following note:

Individual companies should choose their own values, consistent with the degree of conservatism of the company’s risk tolerance criteria. Failure rates can also be greatly affected by preventive maintenance (PM) routines

The LOPA ‘Onion’ represents a multitude of independent protection measures:

IEC 61511-1 Figure 9 – Typical protection layers and risk reduction means

This is illustrated as a series of prevention & mitigation bowtie barriers as follows:

The original CCPS LOPA Book (published in 2001) is now supplemented by Guidelines for Initiating Events and Independent Protection Layers in Layer of Protection Analysis:

Click to access publication page

For more information on all our cards & initiatives – please contact us.

All materials (physical cards/boxes and digital cards/platforms) can be customised to match your technical & local languages – please visit our Options page for more details.

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