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Corrosion Monitoring & Inspection Glossary - C

  • Calibration Dig: Exploratory excavation to validate findings of an in-line inspection tool with the purpose of improving data interpretation.

  • Caliper Pig: A configuration pig designed to record conditions, such as dents, wrinkles, ovality, bend radius and angle, and occasionally indications of significant internal corrosion, by sensing the shape of the internal surface of the pipe (also referred to as geometry pig).

  • Camera Pig: A configuration pig that carries a video or film camera and light sources for photographing the inside surface of a pipeline on an intermittent or continuous basis.

  • Cathodic Protection (CP): A technique to reduce the corrosion of a metal surface by making that surface the cathode of an electrochemical cell or system.

  • Cavitation: The formation and rapid collapse within a liquid of cavities or bubbles that contain vapor or gas or both causing the degradation of a solid body. (This may include loss of material, surface deformation, or changes in properties or appearance).

  • Chainage: Position of a point along the pipeline, typically taken from a fixed reference such as a valve.

  • Characterization: The process of quantifying the size, shape, orientation, and location of an anomaly, defect, or critical defect after it has been detected. There are many degrees to which characterization can be successful. For example, one type of characterization of a mechanical-damage defect may be to determine whether the defect contains a cold worked region (severe) or not (less severe).

  • Characterize: To qualify the type, size, shape, orientation, and location of an anomaly.

  • Check Valve: Valve that prevents reverse flow. Can cause damage to in-line inspection tools if not fully opened.

  • Chemical analysis: Different types of chemical analyses can provide valuable information in corrosion monitoring programs. The measurement of pH, conductivity, dissolved oxygen, metallic and other ion concentrations, water alkalinity, concentration of suspended solids, inhibitor concentrations and scaling indices all fall within this domain.

  • Class Location: A criterion for pipeline design set by the United States Code of Federal Regulations, Title 49, Part 192." Class 1 is rural and Class 4 is heavily populated. A class location is based on the number and type of buildings situated in an area that extends 220 yd (200 m) on either side of the centerline of any continuous 1.0-mile (1.6-km) length of a gas pipeline.

  • Classify: To separate the cause of indications into one of three categories, namely, anomalies, non-relevant conditions, or system components.

  • Cleaning Pig: A utility pig that uses cups, scrapers, or brushes to remove dirt, rust, mill scale, and other debris from the pipeline. Cleaning pigs are utilized to increase the operating efficiency of a pipeline or to facilitate inspection of the pipeline.

  • Coating Disbondment: The loss of adhesion between a coating and the substrate.

  • Coil Sensor: See Induction Coil.

  • Cold working: Distortion of the grains in the vicinity of a gouge. Cold working often occurs immediately under the visible gouge and can significantly reduce the mechanical properties of a pipe steel.

  • Compression: (1) The process of increasing the pressure of gas to maintain its flow in a pipeline system. Compressing gas is analogous to pumping liquids, such as water or oil. (2) The process of reducing the amount of data to be stored in an in-line inspection tool.

  • Condition monitoring: Determination of the health or condition of a machine or system by analysis of signals generated. Measurements may be taken either periodically or continuously, and can cover a very wide range of features including corrosion.

  • Configuration Pig: An instrumented pig that collects data relating to the inner contour of a pipe wall or of the pipeline: geometry pigs, camera pigs, and mapping pigs are types of configuration pigs.

  • Corrosion: The deterioration of a material, usually a metal, that results from a reaction with its environment.

  • Corrosion Pit: Local concentrated-cell corrosion on the external or internal surfaces that results from the generation of a potential (voltage) difference set up by variations in oxygen concentrations within and outside the pit. The oxygen-starved pit acts as the anode and the pipe surface acts as the cathode.

  • Coupon, Weight loss: A removable test strip or disk of metal used in a gaseous or liquid medium to provide an indication of the corrosivity between the medium and that type of metal.

  • Crack Coalescence: Joining of two or more cracks in close proximity to form a longer crack.

  • Crack, Cracking: Very narrow elongated defects caused by mechanical splitting into parts.

  • Crevice corrosion: Localized corrosion of a metal surface at, or immediately adjacent to, an area that is shielded from full exposure to the environment because of close proximity between the metal and the surface of another material.

  • Critical Defect: A defect for which an analysis indicates that immediate attention is required.

  • Cultures: Micro-organism, tissue or organ on a surface specially prepared to cultivate its growth.

  • Cup Pig: A utility pig that is supported and driven by cups made of a resilient material such as neoprene or polyurethane. At least one of the cups forms a piston-like seal inside the pipeline.

Corrosion Inspection and Monitoring