Photo Gallery C4: Cut Grooved Pipe
Grooved clamped pipe has a long history of providing outstanding service. Nevertheless, certain issues exist for any environment where corrosion is a concern.
One of the greatest threats to any grooved piping system is where the groove is cut into the outside of 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 forced inward to created a very noticeable raised bump. Technically, no pipe wall is lost. 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 impact is similar to threaded smaller diameter pipe.
Cutting the groove then introduces an immediate vulnerability to each end of any smaller diameter pipe since corrosion no longer needs to penetrate the full pipe wall, but to only reach the base of the cut groove. A small leak, should it occur, then initiates a second corrosion front within the outer groove surface and to the clamp as well. If cut unevenly, the physical strength and reliability of the fitting is reduced.
Cut grooved pipe has certain benefits, and has been turned to within the dry and pre-action fire industry as one means to eliminate the internal roll groove given that it is responsible for preventing water from draining. Larger diameter schedule 40 pipe can only be cut grooved because of its high wall thickness, but is also far less vulnerable.
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. Although roll grooved pipe is far more common within the building industry, the presence of cut grooved pipe within any heavily corroded piping system only accelerates its failure.
