PLSS Degradation Management Theory - Overview

Every plant is subjected to several potential Degradation Mechanisms (DMs), which need to be carefully controlled to avoid unsafe situations and/or high costs. Degradation Management in IMS PLSS is about the management of these DMs for Pipelines. 

In IMS Degradation Mechanisms (DMs) and their associated Barriers are captured within defined Systems. Subsequently, Risk-Based methodologies such as RBA are used to optimize inspections and monitoring strategies.

The Three Phases of Degradation Management

Degradation Management has three main phases: Threat Identification, Barrier Design, and Barrier Maintenance.

The Degradation Management Phases.

In the image above, the three main phases are shown together with their important sub-phases (for the implementation of these phases with IMS PEI – go to the referenced Steps, for PLSS click on the links):

• Threat Identification
  • Collect and capture asset information in IMS. 
  • Define Systems and assign corresponding Equipment to it.
  • Add Degradation Mechanisms (Threats).
• Barrier identification and Design
  • Add Barriers to the Systems and assign applicable Mitigating Equipment to the Barriers.
  • Asses the Barrier effectiveness and requirement for additional Barriers.
  • Design a Barrier verification & maintenance plan: Determine Inspections via Schedules, monitoring via IOWs and maintenance activities via CAIRs to confirm Barrier statuses. This is where Fit for Service, Internal, External and Risk Based Analyses come in.
• Barrier health Verification and Maintenance
  • Execute the verification plan:
    • Carrying out scheduled inspections.
    • Perform Fitness-for-Service (FFS), Internal, External, and/or Risk-Based Assessments.
    • Document all relevant data using the ECH.
  • Review the Barrier Statuses via Indicators.
  • Maintain the Barriers by restoring compromised or failed Barriers:
    • Execute CAIRs and other mitigating work.
    • Record ECHs (and credit the CAIRs) for the work performed.

The Bowtie Model

Threats and Barriers can also be described in terms of the Bowtie Model.

The Bowtie mode.The Bowtie model definitions:

• Threat: What may cause the Top Event (i.e. the Threat is the Degradation Mechanism).
• Barrier: (1) What directly reduces the likelihood of the Threat leading to the Top Event, and (2) What directly reduces the likelihood of the Scenario (worst-case Consequence).
• Top Event: The first event to release the Hazard.
• Hazard: A situation or substance that influences the Consequence of the Top Event.
• Scenario: Description of the worst-case Consequence of the Top Event (the Hazard release).
• Consequence: Actual effect of the Top Event (Hazard release). 

Degradation Management Workflow

Let's have a look at the PLSS Degradation Management Workflow.