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Sustainability Analytics and Decision Execution
Published in Ram Ramanan, Introduction to Sustainability Analytics, 2018
A simplified method of risk assessment that falls between a qualitative process hazard analysis and a traditional quantitative risk analysis is layer of protection analysis (LOPA).387 It is a semiquantitative risk screening method that is applied following a qualitative hazard identification tool such as HAZOP. LOPA uses simplifying rules to evaluate initiating event frequency, independent layers of protection, and consequences to provide an order-of-magnitude estimate of risk. It conservatively estimates failure probability, usually to an order of magnitude level of accuracy. The result is by designing an overestimate of the risk. More rigorous quantitative techniques, such as fault tree analysis or quantitative risk analysis, may be required for narrower ranges of risk.
Evaluate and Manage Process Risks
Published in James A. Klein, Bruce K. Vaughen, Process Safety, 2017
James A. Klein, Bruce K. Vaughen
The HEE methodology is therefore intended to identify all the pathways via equipment and operational failures that can lead to potentially hazardous events and to ensure that sufficient protection layers are provided, based on PHRA team evaluation and applicable risk criteria. The result is a comprehensive and very detailed list of possible engineering and administrative control failures, their consequences, and associated safeguards. If desired, the Bow Tie diagrams [33] or similar methods, as discussed in Chapter 3, can be used to visualize significant event scenarios and safeguards. Layer of protection analysis (LOPA) is often used to quantify the effectiveness of safeguards in achieving desired risk criteria (see Section 7.10).
Risk Assessor's Toolbox
Published in Charles Yoe, Principles of Risk Analysis, 2019
Willey (2014) defines layer of protection analysis (LOPA) as a simplified risk assessment methodology used to understand how a process deviation can lead to a hazardous consequence if it is not interrupted by the successful operation of a safeguard called an independent protection layer (IPL). An IPL is a safeguard that can prevent a scenario from progressing to an undesirable consequence. The combined effect of the IPLs associated with a hazard scenario are compared against risk tolerance criteria to determine if additional risk reduction measures are required to reach a tolerable level of risk. A variety of LOPA methods are available.
NSTX-U Personnel Safety System: Safety Instrumented System Development and Design
Published in Fusion Science and Technology, 2021
Joseph R. Petrella, Timothy Stevenson, Mark Cropper, Paul Sichta, Michael D’Agostino, Moheb Thomas, Xin Zhao, Clarence Hines
Layer of Protection Analysis (LOPA) is one method described within IEC61511 for the determination of safety-instrumented function risk-reduction requirements.2 The method includes identifying risks, probabilities, and severities in order to qualitatively determine the magnitude and likelihood of each potential risk (step 1 in Fig. 4). In concert with identifying the potential risk factors, the correlating tolerable risk frequency is determined for three risk outcome severity levels: low, medium, and high (step 2 in Fig. 4). This is typically application specific, and accordingly, PPPL adopted tolerable risk frequencies that were consistent within the National Laboratory accelerator community. The adopted tolerable risk frequencies used as target maximums in the LOPA are illustrated in Table I.
A Novel Method to Apply Reliability-Centered Maintenance on Over-Current Protection Systems
Published in Electric Power Components and Systems, 2020
Mohammad Hossein Nasri, Sayed Yaser Derakhshandeh, Abbas Kargar
The possible future researches can be considered as follows:Application of the proposed method on other protection systems such as differential and distance protection systems.Consideration of all available protection systems in a sample power grid as a comprehensive system to model the effects of each protection system failure on the other ones (Green dash area in Figure 3).Consideration of a safety analyses such as Layer of Protection Analysis to obtain the impact of proposed method on the safety of the system.