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 is about the management of these DMs for Pressure Equipment and Piping. In IMS the Corrosion Loops can be used to capture these DMs as well as their Barriers. Subsequently the Shell Risk-Based Inspection (S-RBI) methodology built into IMS can be used to optimize inspections and proactive-monitoring plans, to ensure the health and maintenance of Barriers against in-service degradation.

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 – go to the referenced Steps):

• Threat Identification
  • Collect and capture asset information. (Step 1)
  • Defining CL Boundaries, Process and Potential DMs (including effective materials, susceptible areas, damage rates and the parameters that affect them. (Step 2)
  • Identify the Degradation Mechanisms. (Step 2) 
• Barrier identification and Design
  • Identify the Barriers. (Step 2)
  • Asses the Barrier effectiveness and requirement for additional Barriers. (Step 2)
  • Design a Barrier verification & maintenance plan: Determine inspection, monitoring and maintenance activities to confirm Barrier statuses. This is where S-RBI Analyses comes in. (Step 3 to Step 12)
• Barrier health Verification and Maintenance
  • Execute the verification plan - inspect, analyze and document. (Step 13)
  • Review the Barrier Statuses. (Step 13)
  • Maintain the Barriers by restoring compromised or failed Barriers. (Step 14)

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 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 Degradation Management Workflow.