Layer of Protection Analysis (LOPA

By: Dyadem  09-12-2011
Keywords: risk analysis, Risk Mitigation

What is Layer of Protection Analysis?

LOPA is a semi-quantitative risk analysis technique. It lies between a HAZOP and a quantitative risk assessment (QRA) in terms of its rigorousness. This technique evaluates risks by orders of magnitude of the selected accident scenarios and builds on the information developed in qualitative hazard evaluation (e.g. PHA).

Layers of Protection

Plants are protected by various layers of protection:

  • Pressure Relief Devices
  • Flare Systems
  • Fire Suppression Systems
  • Safety Instrumented System (SIS) or Emergency Shutdown System
  • Automatic action safety interlock system
  • Basic controls, critical alarms
  • Community emergency response
  • Inherently safe design features
  • Operator intervention
  • Plant emergency response

 

When should you use LOPA?

LOPA is applied when a scenario is too complex or the consequence is too severe for the HAZOP team to make a sound judgment based solely upon the qualitative information.

LOPA helps you to answer the following questions about your facility:

  • What's the likelihood of undesired events / scenarios?
  • What's the risk associated with the scenarios?
  • Are there sufficient risk mitigation measures?

 

Benefits of using LOPA

  • Requires less time and resources than a QRA but is more rigorous than HAZOP.
  • Many process safety systems are over-engineered for safety with additional costs and have unnecessary complexities. LOPA helps focus the resources on the most critical safety systems.
  • Acts as a decision making tool, helps make judgments quicker, resolves conflicts and provides a common base for discussing risks of a scenario.
  • Removes subjectivity while providing clarity and consistency to risk assessment.
  • Improves scenario identification by pairing of the cause and consequence from PHA studies.
  • Helps to compare risks based on a common ground if it is used throughout a plant.
  • Helps decide if the risk is As Low As Reasonably Possible (ALARP) for regulatory reasons.
  • Identifies operations, practices, systems and processes that do not have adequate safeguards.
  • Provides basis for specification of IPLs as per ANSI/ISA S84.01, IEC 61508 and IEC 61511.
  • Helps to decide which safeguards to focus on during operation, maintenance and related training.
  • Support compliance with process safety regulations - including OSHA PSM 1910.119, Seveso II regulations, ANSI/ISA S84.01, IEC 61508 and IEC 61511.

 

LOPA Methodology

LOPA evaluates risk in order of magnitude of selected accident scenarios. There are five basic steps in LOPA:

  1. Identify the scenarios
  2. Select an accident scenario
  3. Identify the initiating event of the scenario and determine the initiating event frequency (events per year)
  4. Identify the Independent Protection Layers (IPL) and estimate the probability of failure on demand of each IPL
  5. Estimate the risk of scenario

Keywords: risk analysis, Risk Mitigation

Contact Dyadem

Email - none provided

Print this page

Other products and services from Dyadem

09-12-2011

Hazard and Operability Analysis (HAZOP

Dyadem offers a proven track record of helping our clients achieve success in risk mitigation and is committed to providing industry professionals with constructive solutions to facilitate their Hazard and Operability Studies. This is followed by a series of onsite meetings where the facilitator guides the team to identify the hazards associated and assists them in analyzing these scenarios further.


09-12-2011

Failure Mode and Effects Criticality Analysis (FMECA

Dyadem offers a proven track record of helping our clients to achieve success in reliability and is committed to providing industry professionals with constructive solutions to meet their reliability assessment and management objectives. The purpose of this analysis is to rank each potential failure mode identified in the FMEA study according to the combined influence of severity classification and its probability of occurrence.


09-12-2011

FMEA Services

Dyadem offers a proven track record of helping our clients to achieve success in reliability and is committed to providing industry professionals with constructive solutions to meet their reliability assessment and management objectives. Failure Mode and Effects Analysis is a comprehensive engineering technique that manufacturers can use to improve the quality, reliability and safety of their products.


09-12-2011

Desktop Products - Dyadem

Flexible and User-Friendly:FTA-Pro can be configured to meet your specific needs and helps you complete fault-tree analyses in three independent calculation engines – verifying your results on a fault-tree at least three times. Fault Tree Analysis is a top-down approach for analyzing pre-event failures with systems in development, beginning with the top event, then determining all the ways it can occur.


09-12-2011

Audits - Dyadem

Process Safety Management systems audits are necessary to track and monitor safety systems and procedures implementation. The PSM system has 14 major elements and many sub-elements that can guide the monitoring of the system. PSM Systems Audits identify opportunities where systems can be strengthened. The progress should be periodically reviewed and improved.


09-12-2011

Our Approach - Dyadem

Dyadem’s Professional Services team works to engage, partner and empower our clients to achieve their risk management goals and objectives ensuring that they attain regulatory compliance and achieve business continuity. Our experience spans industries and geographies, from the desert sands to the oil sands, open pit mines, underground mines and gold mines and from revalidating old facilities to evaluating the safety of new facilities.


09-12-2011

Control Hazards and Operability Analysis (CHAZOP

This methodology is used to identify potential flaws and weaknesses of instrument control and computer systems by reviewing how the system deviates from design intents. It supports the risk analysis requirement in IEC 61508, Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems.