Grooved clamped pipe has a long history of excellent service.  Nevertheless, certain issues exist for any environment where corrosion is a concern.

One of the greatest threats to any grooved pipe system is where the groove is cut into the pipe rather than rolled.  When rolled, the pipe wall is pressed or swaged into the outer wall resulting in that pipe wall material being pressed inward to created a raised bump.  When cut, the same depth of the groove is physically removed from outer pipe wall to leave the pipe thinner in this localized area.  The effect is similar to threaded smaller diameter pipe.

Cutting the groove then introduces an immediate vulnerability to each end of the pipe.  Corrosion no longer needs to penetrate the full pipe wall, but to only reach the base of the groove.  A small leak then initiates a second corrosion front within the outer groove surface and to the clamp as well.

Identifying a cut vs. rolled groove is visually impossible once the pipe is assembled.  For galvanized steel pipe, commonly used for fire protection systems, a cut groove can be determined after a few years by the rust appearing where the groove was cut.  Ultrasonic side angle beam flaw detection will also provide an answer.  Often, piping specifications will not define how the groove is constructed – leaving that decision to the piping contractor.

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