Pipeline Construction: Coatings

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The applicable regulations addressing protective coating are §192.461 for gas pipelines and §195.559 for hazardous liquid pipelines. Additional discussion on coatings can be found at the Stakeholders Communications web site and the PHMSA presentation on Construction and Pipeline Coatings which was given in the April 23, 2009 workshop on new pipeline construction issues. Some specific considerations for coating applications during construction are provided below:

Field Joints

  • The coating cutback can be too small or too large – The coating manufacturer’s instructions on the coating cutback distance must be followed to ensure long-term bonding of the material to the pipe.

  • Proper pipe surface preparation is a must. PHMSA inspection has seen instances where the surface was inadequately cleaned. The pipe should be sand blasted and then preheated as instructed by the coating manufacturer.

  • Care must be taken in the application of coatings in the field. Shielding may be needed to avoid dust or rain water contamination. Following the coating application, v coating thickness must be verified to ensure the manufacturer’s specifications have been met.

Coating Inspection

  • Prior to backfilling, the entire pipeline should be visually inspected by trained and qualified inspectors.

  • Inspection for coating holidays should use properly calibrated equipment. The inspection process must ensure that the proper voltage is used. Equipment calibration and use must be in accordance with the manufacturer’s specifications. Particular attention should be paid to identification of damage by weld bands.

PHMSA inspection has seen the following types of concerns when inspecting new pipeline construction:

Coating - Fusion Bonded Epoxy Issues
  • Coating over mud or rust
  • Application temperature too hot or cold
  • Heat damage to the factory FBE coating
  • Failing to follow manufacturer's instructions
  • Sand blast technique - no correct bevel / no overlap at factory coating
  • Coating in high wind with blowing dirt
  • Water in the pipe during heating – does not allow for uniform heating
  • Coating specifications not available to inspectors
  • Girth weld coating not fully bonded to pipe
Coating - Melt Stick
  • Failing to follow manufacturer's instructions
  • Not adequately heating pipe before application
  • Inadequate surface preparation - abrasion
  • Use on defects larger than 0.5 in2
  • Application over two part epoxy
  • Improper accelerated drying by patting
  • Use on bare metal
Coating - Electronic Defect Detectors (Jeeping)
  • Failing to follow manufacturer's instructions
  • Low voltage setting on holiday detector
  • Inadequate training of inspectors and contractors
  • Jeeping over tape and fiberboard stuck to the pipe
  • Failing to adequately clean the pipe before jeeping
  • Failing to visually inspect pipe for coating defects
  • Using damaged (bent) detector springs
  • High resistance in electrical circuit
  • Jeeping at too fast a speed per the spec or manufacturer
  • Jeeping over coating repairs before they are dry
  • Detector failing to identify defects
  • Detector not calibrated per manufacturer
Coating - Two Part Epoxy Issues
  • Failing to follow manufacturer's instructions
  • Inadequate surface prep - abrasion
  • Application after epoxy starts to set
  • Inadequate mixing of the epoxy
  • Applying above or below recommended temp - or not pre-heating pipe
  • Using unapproved IR temperature sensors