These studies are a key part of modern hazard studies, helping organisations decide when a safety function must perform to a defined integrity level. At OTECSA, we are often asked to help clients decide which scenarios should go to LOPA and which can be managed through other risk assessment methods.
Some clients have clear internal rules within their risk management systems. Others rely on specialist support to make consistent, defensible decisions. The layers of protection analysis process can technically be applied to any hazardous event, but its most common use is to determine whether a safety trip needs to function as a SIL rated system.
What Are LOPA Scenarios and Why Are They Used?
LOPA is a semi quantitative risk assessment method. It assigns numerical values to layers of protection in order to estimate how often a hazardous event might occur. By comparing this frequency with a tolerable risk target, LOPA shows whether there is a gap that must be closed by an instrumented safety function.
This approach allows teams to move beyond purely qualitative judgement and make structured, transparent decisions about risk reduction.
Which scenarios should go to LOPA?
When screening HAZOP results, we typically recommend LOPA scenarios are selected where
- The potential consequences are high severity, for example events that could lead to serious injury or fatality on site or off site.
- There is an instrumented protection system acting as a safeguard, such as a high level trip, high pressure trip or gas detection system.
These criteria help focus effort on the scenarios where LOPA adds the most value.
Using LOPA for SIL decisions
In many cases, LOPA scenarios are used to decide whether a safety trip needs to be SIL rated and, if so, to what level. The analysis shows how much risk reduction is already provided by existing layers and how much must be delivered by the safety instrumented function
This ensures that safety systems are neither over designed nor under designed, supporting both safety and cost effective engineering.
Using LOPA for ALARP
LOPA scenarios can also be used to support ALARP demonstrations. In these cases, there may be no safety trip present, but the question is whether the existing design reduces risk to a broadly acceptable level
If it does not, LOPA can be used alongside cost benefit analysis to test what additional measures may be justified. This structured approach supports defensible decisions that balance safety improvement with proportional use of resources.
Talk to Our Team
If you are unsure which scenarios should go to LOPA, or how to apply LOPA effectively within your hazard studies, our team can help. We support clients with screening HAZOP outputs, facilitating LOPA studies, SIL determination and ALARP demonstrations.
Get in touch with OTECSA Consulting to discuss your process, your risks and the most practical way to apply LOPA for safe, compliant and efficient operations.