---
title: "The LOPA process steps in IMS"
slug: "the-lopa-process-steps-in-ims"
tags: ["LOPA"]
updated: 2026-10-27T23:12:18Z
published: 2026-10-27T23:12:18Z
canonical: "ims-handbook.cenosco.com/the-lopa-process-steps-in-ims"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://ims-handbook.cenosco.com/llms.txt
> Use this file to discover all available pages before exploring further.

# The LOPA process steps in IMS

![](https://cdn.document360.io/e492a0e0-a4ba-4aca-8fc6-76b95f91fdf3/Images/Documentation/LOPA%20Concept%20(1).png?sv=2026-02-06&spr=https&st=2026-11-07T18%3A01%3A57Z&se=2026-11-07T19%3A01%3A57Z&sr=c&sp=r&sig=Pfi%2BreJBPOzBLjOyt7icy6mki3Felw0jJAnQ0%2Bwy%2BE8%3D)The LOPA process can be implemented as described below in IMS:

**Step 1**: Identify the Hazard Scenario:

Typically, this is part of a [HAZOP](/v414/docs/overview-hazop).

**Step 2**: Identify the Consequence and Consequence Severity of this Hazard Scenario:

With an integrated HAZOP/LOPA study, this will be part of a [HAZOP](/v414/docs/defining-the-consequences-for-each-hazop-deviation). The scenario may be marked for LOPA by the HAZOP team.

**Step 3**: Identify the Initiating Events of the Hazard Scenario and determine their Frequencies of occurrence. The frequencies can be based on industry-accepted and standards-compliant failure rate data or on site/operational experience:

IMS has a large failure rate database. When the Consequence is copied from a [HAZOP](/v414/docs/creating-new-lopas), then its associated Cause is also copied over to the LOPA as the Initiating Event.

**Step 4**:Identify the Independent Protection Layers (IPLs), i.e., the Barriers, and estimate the Probability of Failure on Demand (PFD) of each:

In IMS the Barriers are categorized as Control Barriers (CB) (SIFs fall in this category), Recovery Measures (RMs), and Conditional Modifiers (CM). In IMS, for many Barriers a template can be selected, where the PFDs have already been defined. (When the Consequence is copied from the HAZOP, then its associated Existing Safeguards are copied over as Barriers.)

**Step 5**: Calculate the Residual Risk of the Hazard Scenario by mathematically combining the Tolerability Criteria (TC) of the selected Consequence Severity, Initiating Event Frequency, and Barrier PFDs:

When you click the calculate button ![](https://cdn.document360.io/e492a0e0-a4ba-4aca-8fc6-76b95f91fdf3/Images/Documentation/the-lopa-process-steps-in-ims-image-t0w10sj4.png?sv=2026-02-06&spr=https&st=2026-11-07T18%3A01%3A57Z&se=2026-11-07T19%3A01%3A57Z&sr=c&sp=r&sig=Pfi%2BreJBPOzBLjOyt7icy6mki3Felw0jJAnQ0%2Bwy%2BE8%3D)in IMS:

- IMS first determines Demand Rate (DR) and Residual Risk (Res), using LOPA principles.
- Then the Tolerability Criteria (TC) is used to determine a Risk Reduction Factor (RRF) for each Consequence category (People, Asset, Community, and Economic). RRF= Res/TC.
- A PFD is then be determined: If RRF>1, PFD = 1/RRF else PFD = 1.
- Based on the IEC 61511 criteria, a Safety Integrity Level (SIL) is then derived from the PFD.
- Lastly an Overall RRF and Overall SIL is determined.

**Step 6**: Evaluate the Overall SIL to assess the adequacy of the existing or proposed Barriers against the Hazard Scenario.

**Step 7**: If the Overall SIL for the Consequence is not acceptable, [start a SIF Analysis](/v414/docs/adding-sif-analyses-to-the-lopa) and determine the SIF’s minimum required RRF, i.e., its Target PFD, that achieves an acceptable Overall SIL level.

**Step 8**: Based on the above results, the LOPA team can provide Recommendation(s) that are specific to the LOPA scenario:

The [Recommendations Summary Tab](/v414/docs/recommendations-summary-tab) can be used to record these.