Cased Crossing Solutions

MESA provides pipeline integrity assistance with CASED CROSSING ECDA implementation that ranges from ECDA Plan modifications, Pre-Assessment, Indirect Inspections (field testing), Direct Examination and Remediation of the Casing Integrity Components including Preparation to Fill Casings along with completing all Process Documentation, either for your local or national Casing Integrity Program.

Establishing the cased crossing integrity is more than just testing for the casing condition (metallic short, electrolytic couple or clear) and must include determining “the past, present and future corrosion behaviors”.

Introduction

  • 2012 deadline for performing initial integrity assessment of natural gas pipelines HCAs including cased crossings
  • PHMSA document released in 2010 gives guidance to assessing cased crossings by External Corrosion Direct Assessment (ECDA)
  • Operators must implement either this guidance or an operator plan that will pass the rigor of these guidelines supporting audit protocol

Pre-Assessment

  • 17 attributes of a casing have been defined that are either required or should be considered in performing Pre-Assessment.
  • Pre-Assessment will define the feasibility to apply ECDA, the initial regions, and the proper indirect inspection tool to be applied.
  • Regions will group the casings by physical conditions that would have similar past, present and future corrosion behaviors.

Indirect Inspection

  • Indirect inspection will define if a casing has a metallic short, electrolytic couple, or is clear.
  • Direct metallic short is classified by the PHMSA guidelines as a immediate condition.
  • Cased crossings (bare or coated) with metallic short an full of water (electrolytic couple) pose a corrosion threat to the carrier pipe inside the casings due to the shielding effect of the metallic short present.
  • Coated casings with an electrolytic short are the next greatest risk for shielding cathodic protection current and protecting the coating anomaly that may be present in the casing.
  • Indirect inspection results will categorize and rank casings by Immediate, Scheduled or Monitoring for direct examination dig selection in each region.
  • There is a need to perform additional testing that defines the past, present, and future corrosion behaviors.

Direct Examination

  • Excavations required by the ECDA Plan for each region will assess the risk and conditions present within the casing.
  • PHMSA guidelines suggest that Guided Wave Ultrasonic Thickness (GWUT) should be used to “look 100%” into the casing in assessing the physical condition of the pipeline.
  • GWUT will be required that complies with the GWUT “18 point” guideline.

Construction and Maintenance Practices

  • Operators will need to review and potentially modify construction practices, i.e., attempt to eliminate any cased crossing installation for future construction and modify installation/inspection practices in the future to reduce the risks created by a cased crossing installation.
  • Removal of direct metallic shorts and a maintenance program that attempts to reduce risk conditions for corrosion (presence of water/soils) is needed.
  • Filling casings will allow the operator to reassess the corrosion threat risk and re-prioritize of the corrosion risk of filled casings.
  • PHMSA gives specific guidance for monitoring filled and unfilled casings.
  • Minimal casing fill requirements are defined as “documenting the % casing filled” and the guideline documentation is defined.

Operator Dilemma

  • The dilemma for every operator is “what” and “how to” implement these guidelines in the development of a Cased Crossing ECDA Program. MESA has developed a Cased Crossing ECDA Program to assist our clients.