Optical Emissions Spectrometry (OES)

Optical Emmissions

Optical Emissions Spectrometry (OES) helps pipeline owners and operators identify characteristics of unknown pipe with less effort, lower total cost, and shorter turnaround.

Specifically, OES is used to determine chemical composition, including carbon equivalency (CE) values. CE values are used to support welding procedures and provide documentation required for the Positive Material Identification (PMI) process.

OES is the only reliable way to measure carbon outside of the laboratory.

Best used for: field testing to identify chemical composition and performing trace metal analysis

Key features:

  • Applications include pipe body, longitudinal weld seams, and fittings.
  • All measurements meet stated accuracy tolerances.
  • Less expensive and faster than sending a sample to a laboratory for analysis.


  • How does OES work? OES measures the intensity of spectral peaks formed when a spark between the pipeline and an electrode causes electrons in the pipeline to emit light.
  • Is OES non-destructive? OES is considered non-destructive, although the spark does leave a small burn on the pipeline’s surface. Third party validation of the TDW OES method has proven the non-destructive nature of the polished and etched cross section under the optical microscope with a maximum depth of penetration of only 0.03302 millimeters (0.00013 inches).
  • How long has OES technology been in use?  OES has been in use for more than 50 years in a variety of industries.