PROCESS SAFETY
OUR SERVICES
- Compatibility Study
- Preliminary Hazard Analysis (PHA)
- Hazard and Operability Study (HAZOP)
- Failure Mode and Effect Analysis (FMEA)
- Hazard Analysis and the Critical Control Points (HACCP)
- Fault Tree Analysis (FTA)
- Quantitative Risk Assessment (QRA)
- Risk Management Plan (RMP)
- Inherent Safety
- Consequence Analysis for Events with Flammable and Toxic Chemicals
- Equipment and Process Plants Reliability Studies
- Control of Static Electricity in Chemical Plants
- Training and Information Courses in the Risk Assessment and Management Techniques
- Safety Integrity Level (SIL) Assessment
- Layer of Protection Analysis (LOPA)
Layer of Protection Analysis (LOPA)
“Layer of Protection Analysis (LOPA)” is a technique used for carrying out a simplified quantified risk assessment of a defined hazardous scenario. As originally conceived, the LOPA methodology applied simple and conservative assumptions to make the risk assessment. In this approach, order-of-magnitude factors are used for the initiating event frequency, consequence severity and the likelihood of failure of independent protection layers (IPL) to estimate the risk.
The simple order of magnitude approach is often used as a risk screening tool to determine whether a more detailed analysis should be performed. In some cases, the use of fault tree analysis and event tree analysis, supported by consequence/severity analysis may be more appropriate than using the LOPA methodology.
Hazardous scenarios can be derived by a number of techniques, e.g. Hazard and Operability Studies (HAZOP), Failure Modes and Effects Analysis (FMEA) or preliminary hazard analysis (PHA). These studies will typically provide at least one initiating event, a description of the consequences and may also provide information on the protective measures.
Like many other hazard analysis methods, the primary purpose of LOPA is to determine if there are sufficient layers of protection against a hazardous scenario, to result a tolerable risk. A scenario may require one or many protection layers depending on the process complexity and potential severity of a consequence. Note that for a given scenario, only one layer must work successfully for the consequence to be prevented. However, since no layer is perfectly effective, sufficient protection layers must be provided to render the risk of the accident tolerable.
LOPA provides a consistent basis for judging whether there are sufficient IPL to control the risk of an accident for a given scenario. If the estimated risk of a scenario is not acceptable, additional IPL may be added. Alternatives encompassing inherently safer design can be evaluated as well. LOPA does not suggest which IPL to add or which design to choose, but it assists in judging between alternatives for risk mitigation. LOPA is not a fully quantified risk assessment approach, but is rather a simplified method for assessing the value of protection layers for a well-defined accident scenario.