Situation Analysis

Choosing monitoring locations based on convenience may not be indicative of what is really happening. Proper equipment and location of monitoring sites is critical for obtaining useful information and is ideally taken into account during the design and fabrication stages. Most corrosion failures occur at the lowest elevation in any system; the majority of failures are at the bottom of pipes/vessels. Some corrosion occurs in risers or in vessels/pipes with minimal flow and/or large temperature changes.

The severity of corrosion attack is influenced by other local factors:

  • Water soluble components in the Gas phase (CO2, H2S)
  • Water soluble solids in the Liquid phase (carbonate, bicarbonate, chlorides, sulphates)
  • Water soluble liquids in the Liquid phase (acids, alkalis, amines, glycols, organic acids)
  • Insoluble solids which form sludges (clay, marine shells, sulphur elements, amine products)
  • Living organisms such as algae and bacteria

Selecting Monitoring Locations

  • Based on historical data (past failures, visual inspections, UT or other NDE information)
  • Based on system assessment to identify potential corrosion mechanisms
  • High temperature locations
  • Certain types of piping/vessel materials
  • System conditions (H2S, CO2, Amines)
  • Low spots in system – water or solid traps
  • Stagnant flow areas based on pipeline topography
    Specific Considerations for Intrusive Monitoring Systems
    • Clearance for retrieval equipment
    • Pigging requirements
    • Inhibitor injection locations
    • Pressure
    • Temperature

    Monitoring Interval Options

    1 month interval active system or monitoring new inhibitor programs
    3 - 4 month interval baseline data or ongoing monitoring of active system
    6 month interval constant process conditions - no significant activity
    Annual interval undesirable, behind in information