Obstructions: Any restriction or foreign object that reduces or modifies the cross section of the pipe to the extent that gas flow is affected or in-line inspection pigs can become stuck (ovality, collapse, dents, undersized valves, wrinkles, bends, weld drop through). Also any foreign object in the pipeline. (See pipe collapse)
Off-Line Inspection: Inspection of a pipeline section that is removed from service.
Off-Line Monitoring: Refers to monitoring methods in which a sample is taken for subsequent analysis.
Oldfield & Todd analysis: Equation for determining the oxygen corrosion for carbon steel in seawater.
On-Line Inspection: Inspection of a pipeline section while it is in service.
On-Line Monitoring: Refers to installation of monitoring equipment for continuous measurement of metal loss, corrosion rate, or other parameters in an operating system. Data are obtained without the removing the monitoring device.
Ovality: A condition in which a circular pipe forms into an ellipse, usually as the result of external forces.