EXPLANATION OF CRITICAL ROLL GROOVE DIMENSIONS
WARNING
• Pipe dimensions and groove dimensions must be within the tolerances specified in the
tables on the following pages to ensure proper joint performance.
Failure to follow these specifications could cause joint failure, resulting in serious personal
injury and/or property damage.
A
B
D
B
T
C
OD
F
Standard Roll Groove
Exaggerated for clarity
Pipe Outside Diameter –
The average pipe outside diameter must not vary from the specifications
listed in the tables on the following pages . Maximum allowable pipe ovality should not vary by more
than 1% . Greater variations between the major and minor diameters will result in difficult coupling
assembly .
The maximum allowable tolerance from square-cut pipe ends is:
1/32
inch/0 .8 mm for 2 – 3 1/2-inch/60 .3 – 101 .6-mm sizes and
1/16
inch/1 .6 mm for
4-inch/114 .3-mm and larger sizes . This is measured from the true square line .
"S" Max.
Raised internal and external weld beads and seams must be ground flush with the pipe surface
2 inches/50 mm back from the pipe ends . The inside diameter of the pipe end must be cleaned to
remove coarse scale, dirt, and other foreign material that might interfere with or damage grooving
rolls . The front edge of the pipe end shall be uniform with no concave/convex surface features that
will cause improper grooving roll tracking and result in difficulties during coupling assembly .
“A” Dimension –
The “A” dimension, or the distance from the pipe end to the groove, identifies the
gasket seating area . This area must be free from indentations, projections (including weld seams),
and roll marks from the pipe end to the groove to ensure a leak-tight seal . All foreign material, such
as loose paint, scale, oil, grease, chips, rust, and dirt must be removed .
“B” Dimension –
The “B” dimension, or groove width, controls expansion, contraction, and angular
deflection of flexible couplings by the distance it is located from the pipe and its width in relation to
the coupling housings’ “key” width . The bottom of the groove must be free of all foreign material,
such as dirt, chips, rust, and scale that may interfere with proper coupling assembly .
“C” Dimension –
The “C” dimension is the average diameter at the base of the groove . This
dimension must be within the diameter’s tolerance and concentric with the OD for proper coupling
fit . The groove must be of uniform depth for the entire pipe circumference .
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REV_A
TM-RG3212
/ Operating and Maintenance Instructions Manual
