Process risk analysis is crucial in certain industrial sectors. Facilities like power plants and chemical plants require regular safety system reviews concerning their operational processes. In this context, we encounter HAZOP and LOPA, two of the most common analysis methods for these purposes.
Understanding these methodologies can be pivotal for the safety of organizations dealing with chemical products daily. But what are the differences between HAZOP and LOPA? What does each technique entail? And most importantly, why is it advisable to conduct them periodically in such installations?
WHAT IS HAZOP ANALYSIS?
The Hazard and Operability Study (HAZOP) is dedicated to evaluating the consequences of hypothetical deviations at each stage of the operational process. It can be conducted during the design of a new process, while it’s operational, during periodic reviews, or when implementing modifications.
HAZOP assumes that a significant portion of risks arises from operational intentions or design deviations. Throughout the evaluation, various risk scenarios must be identified, along with their causes, quantification, measurement of exposure levels, and the intensity of their consequences.
WHERE AND HOW IS HAZOP ANALYSIS USED?
This methodology is primarily employed in industries such as the gas, nuclear, petroleum, chemical, and pharmaceutical sectors, where operational risks are evident. The differences between HAZOP and LOPA lie not so much in the scenario but in the methodology’s development, as discussed below.
HAZOP analysis involves a wide range of qualified professionals, including engineers, operators, supervisors, and maintenance specialists. They must have a comprehensive understanding of the methodology and concepts such as nodes (the system segment being analyzed), parameters (variable conditions in each node), potential deviations, their causes, and effects.
WHAT IS THE LOPA METHOD?
When referring to Layer of Protection Analysis (LOPA), we mean the analysis of layers of protection or protection layers.
This technique involves conducting a semi-quantitative analysis to assess the risks of an operational process and determine the necessary safety levels to reduce or eliminate them. Additionally, the evaluation is used as a tool for assigning the Safety Integrity Level (SIL).
HOW IS LOPA ANALYSIS PERFORMED?
One of the main differences between LOPA and HAZOP is how these methodologies are carried out. In the case of layer analysis, it is possible to leverage the previous results of a HAZOP assessment to delve deeper into the identified risk scenarios. Nevertheless, LOPA analysis typically proceeds in the following phases:
- Identification of risk scenarios (likely obtained through a HAZOP analysis).
- Quantification of the frequency for each risk scenario.
- Identification of different protection layers and an assessment of their effectiveness.
- Evaluation of risk levels based on tolerability criteria.
- Exploration of measures to mitigate or eliminate risks.
DIFFERENCES BETWEEN HAZOP AND LOPA
After outlining the methodologies for each type of analysis, it is essential to understand the differences between HAZOP and LOPA to determine which evaluation is advisable in specific contexts and at different times. In broad terms, HAZOP is used to identify and analyze hypothetical risk scenarios, while LOPA delves into their quantification and potential solutions.
A HAZOP analysis helps identify safety issues at each stage of the operational process, whereas a LOPA evaluation (often included within HAZOP) precisely determines the Safety Integrity Level (SIL) required and where to implement Safety Instrumented Functions (SIF) in a Safety Instrumented System (SIS).
ARE HAZOP AND LOPA COMPLEMENTARY?
Beyond the differences between HAZOP and LOPA, it’s worth considering the possibility of combining them in a comprehensive process risk analysis. These differences make them complementary techniques. In fact, it’s common to conduct HAZOP evaluations, followed by a more in-depth LOPA study.
This approach strengthens the safety of facilities in high-risk operational areas. It involves an initial analysis for risk diagnosis at each stage of the operational process (HAZOP), followed by a more thorough LOPA study to determine gaps, risk levels, and the implementation of appropriate Safety Instrumented Functions (SIF).
WHY FREQUENTLY APPLY HAZOP AND LOPA ANALYSIS?
Considering that decades ago, production needs took precedence over safety concerns in these sectors, there is an evident need for constant evaluation in such processes. Nowadays, it is not only a legal requirement but also essential for the operation of any industrial system.
At Positive Engineering, we offer various process risk analysis services for industries of all types. We apply the HAZOP technique, including LOPA evaluation. As experts in the field, we recommend conducting these studies regularly and including them in new designs, modifications, or when there are suspicions of risk.