The Difference Between Defects and Discontinuities

Posted by Steve Clymer

Topics: Swanton Welding, Inspection

Every good welder takes pride in his or her work. This innate pride and the desire to meet production quality standards makes welding discontinuities and defects a major concern to any professional welder. Even though both terms sound menacing, they aren’t necessarily synonymous.

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A Welding Discontinuity

Technically, a welding discontinuity is the lack of a mechanical, physical or metallurgical harmony in the weld. This could be manifested in terms of

  • Varied porosity
  • Incomplete fusion or joint penetration
  • Unacceptable profiles
  • Subtle tears and cracks

Welding Defects

All welding defects are developed discontinuities. If a discontinuity renders a weld incompetent or lowers its quality, it would be classified as a defect. Defects make the product risky to use or substandard. It is up to the quality control to decide whether the discontinuity qualifies as a defect or not.

The Differences Between Discontinuities and Defects

Since the line between discontinuities and defects varies from one industry to another, only a generalized explanation can give a good guide to isolating defects from discontinuities.

  • Any weld would be a defect if the welder or the quality control department rejects it and blacklists the product.
  • A defined list of acceptable discontinuities will list the number or type of discontinuities allowed on a product before labelling it a defect.
  • A discontinuity will survive a field test while a defect won’t. A crack on a water pipe would be a defect since the water will leak while an unacceptable profile could pass as a discontinuity as long as the pipe doesn’t leak.

Discontinuities can be ignored since they are always well within the acceptable production error margins. Defects, on the other hand, must be repaired. If the defect is irreparable, the product should get a red reject tag and head to the junk bin.

It’s important to understand the distinction between a weld defect and discontinuity to understand the quality of a weld, and if an imperfection is a safety concern or merely cosmetic. A perfect weld is a precarious achievement that requires meticulous care in the preparation of materials, a work area and careful adherence to welding techniques.

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Topics: Swanton Welding, Inspection