Patent Description:
Circumferential grooves and other features such as shoulders and beads may be formed in pipe elements by various methods, one of particular interest being roll grooving. Roll grooving methods involve engaging an inner roller with an inner surface of a pipe element and an outer roller with an outer surface of the pipe element opposite to the inner roller and incrementally compressing the sidewall of the pipe element between the rollers while rotating at least one of the rollers. Rotation of one roller (often the inner roller) causes relative rotation between the roller set and the pipe element, and features on the inner and outer rollers form corresponding features on the inner and outer surfaces of the pipe element. In one example roll grooving method the rollers remain in a fixed location and the pipe element rotates about its longitudinal axis relative to the rollers. In another example embodiment the pipe element remains stationary and the roller set traverses the pipe element's circumference.

One disadvantage of roll grooving is manifest when forming a circumferential groove in the outer surface of the pipe element near an open end. The circumferential groove is formed when a raised circumferential feature on the outer roller cooperates with a circumferential recess on the inner roller positioned opposite to the raised feature. During groove formation, the open end of the pipe element may become enlarged at the end of the pipe element; the end takes on a "bell" shape, flaring outwardly as an unwanted consequence when the material of the pipe is deformed to form the groove. Pipe end flare is unwanted because it can change the critical outer diameter of the pipe element at the end where it is most important not to exceed a maximum tolerance so that, for example, the pipe element may properly engage mechanical fittings or couplings and form a fluid tight joint. There is clearly a need for grooving rollers and a method of roll grooving which mitigates or eliminates pipe end flare.

Furthermore, pipe elements joined by mechanical couplings often use a flexible seal or gasket to effect a fluid tight seal. The gasket has sealing surfaces that are compressed against the outer surfaces of the pipe elements by the couplings. It is advantageous to improve the surface finish of the pipe elements in the region where they are engaged by the sealing surfaces to provide effective surface contact to ensure a good seal.

<CIT> discloses a groove rolling of piping elements.

<CIT> discloses a machine for roll grooving of a pipe.

<CIT>, on which the preamble of claim <NUM> is based, discloses pipes having wedging circumferential grooves.

<CIT> discloses a method and apparatus for manufacturing a pipe element having shoulder, groove and bead.

The invention encompasses a combination of at least one pipe element and a coupling according to claim <NUM>. Preferred embodiments are subject matter of the dependent claims.

<FIG> shows a roller set <NUM> for roll forming a pipe element (not shown). Roller set <NUM> comprises an inner roller <NUM> engageable with an inner surface of the pipe element, and an outer roller <NUM> engageable with an outer surface of the pipe element. As described below, the sidewall of the pipe element is compressed between the inner and outer rollers <NUM> and <NUM> which cooperate to impart various shapes to the surfaces and sidewall of the pipe element.

In the example embodiment of <FIG>, outer roller <NUM> comprises a roller body <NUM> that is rotatable about a first axis <NUM>. Axis <NUM> is a longitudinal axis, and the roller body <NUM> has a plurality of raised features <NUM>, <NUM> and <NUM> that extend circumferentially around it and project radially from axis <NUM>. The first raised feature <NUM> is located on roller body <NUM> so that it can engage the outer surface of the pipe element near its end and comprises a conical surface <NUM> extending lengthwise along the roller body and projecting radially from axis <NUM>. Conical surface <NUM> has a smaller radius <NUM> positioned adjacent to the second raised feature <NUM> and a larger radius <NUM> positioned distal to the second raised feature. First raised feature <NUM> is used to mitigate, control or prevent flaring of the end of the pipe element being worked between the rollers <NUM> and <NUM> as described in detail below.

<FIG> shows another example embodiment of a roller body <NUM> wherein the first raised feature <NUM> comprises a curved surface <NUM> and a substantially flat surface <NUM> oriented substantially parallel with respect to the axis <NUM>. The curved surface <NUM> projects radially from axis <NUM> and is used to burnish the outer surface of the pipe element near its end as described below.

With reference again to <FIG>, the second raised feature <NUM> is shown as a projection <NUM>. As shown in <FIG>, projection <NUM> extends circumferentially around the roller body <NUM> and is defined by a first surface <NUM> facing the first raised feature <NUM> and oriented substantially perpendicularly to the axis <NUM>, a second surface <NUM> contiguous with the first surface <NUM> and, in this example, oriented substantially parallel to the axis <NUM>, and a third surface <NUM> contiguous with the second surface <NUM> and facing the third raised feature <NUM>. In this example the third surface <NUM> is oriented angularly with respect to the axis <NUM>.

<FIG> shows the example roller body <NUM> wherein the second raised feature <NUM> is shown as a projection <NUM>. Projection <NUM> extends circumferentially around the roller body <NUM> and is defined by a first surface <NUM> facing the first raised feature <NUM> and oriented substantially perpendicularly to the axis <NUM>, a second surface <NUM> contiguous with the first surface <NUM> and, in this example, oriented substantially parallel to the axis <NUM>, and a third surface <NUM> contiguous with the second surface <NUM> and facing the third raised feature <NUM>. In this example the third surface <NUM> is oriented substantially perpendicularly to the axis <NUM>. In the example roller embodiments shown in <FIG> and <FIG> the second raised feature <NUM>, in either form, is used to form a circumferential groove in the pipe element as described below.

As shown in <FIG> and <FIG>, the third raised feature <NUM> comprises a curved surface <NUM> that projects radially from axis <NUM> and has a maximum radius <NUM> which may be substantially equal to the maximum radius <NUM> of the curved surface <NUM> of the first raised feature <NUM> (<FIG>), or the larger radius <NUM> of the conical surface <NUM> (<FIG>). Curved surface <NUM> of the third raised feature <NUM> is used to prevent the pipe element from teetering and thereby losing tracking stability when the first and second raised features <NUM> and <NUM> engage the pipe element as described below.

As shown in <FIG> and <FIG>, it is sometimes advantageous to position the second raised feature <NUM> on a ring <NUM>. Ring <NUM> surrounds the outer roller body <NUM> and is rotatable independently thereof about the axis <NUM>. Bearings <NUM> may be positioned between the ring <NUM> and the outer roller body <NUM> to reduce friction between the ring <NUM> and the roller body <NUM>. By allowing the ring to rotate independently of the roller body, friction between the outer roller <NUM> and the pipe element is reduced. Friction between the roller body and the pipe element occurs when raised features having different radii contact the pipe element. The linear speed of the surface of the raised feature is proportional to its radius from the axis of rotation (in this example axis <NUM>). Thus, for a given angular speed of the outer roller <NUM> and pipe element, the first and third raised features <NUM> and <NUM> will have slower linear surface speeds than the second raised feature <NUM> due to its larger radius. If the second raised feature <NUM> is not permitted to rotate independently of the first and third raised features <NUM> and <NUM>, then there will be slippage between the pipe element and the first and third raised features (or vice versa) which will result in friction and concomitant heat and vibration. This is undesirable, hence the advantage of using ring <NUM> with bearings <NUM>.

While <FIG> illustrates an outer roller <NUM> with a second raised feature <NUM> being a projection <NUM>, and a first raised feature <NUM> comprising a conical surface <NUM>, and <FIG> illustrates an outer roller <NUM> having its second raised feature <NUM> in the form of a projection <NUM> on a ring <NUM> and its first raised feature <NUM> comprising burnishing surface <NUM>, it is understood that all combinations of these various features are feasible. For example, <FIG> illustrates an outer roller <NUM> having a projection <NUM> as its second raised feature <NUM> and a conical surface <NUM> as its first raised feature; <FIG> illustrates an outer roller <NUM> having a projection <NUM> as its second raised feature <NUM> and a burnishing surface <NUM> as its first raised feature <NUM>; <FIG> illustrates an outer roller <NUM> having a projection <NUM> as its second raised feature <NUM> and a burnishing surface <NUM> as its first raised feature <NUM>; <FIG> illustrates an outer roller <NUM> having a projection <NUM> as its second raised feature <NUM> on a ring <NUM>, and a conical surface <NUM> as its first raised feature <NUM>; <FIG> illustrates an outer roller <NUM> having a projection <NUM> as its second raised feature <NUM> on a ring <NUM>, and a conical surface <NUM> as its first raised feature <NUM>; <FIG> illustrates an outer roller <NUM> having a projection <NUM> as its second raised feature <NUM> on a ring <NUM>, and a burnishing surface <NUM> as its first raised feature <NUM>.

<FIG>, <FIG> and <FIG> show an inner roller <NUM>. In this example inner roller <NUM> comprises an inner roller body <NUM> rotatable about a longitudinal axis <NUM>. A flange <NUM> extends circumferentially around the roller body <NUM> and projects transversely to axis <NUM>. A first depression <NUM> in the body <NUM> extends circumferentially there around and is positioned adjacent to (in this example, contiguous with) the flange <NUM>. A second circumferentially extending depression <NUM> is positioned in the roller body <NUM> adjacent to the first depression <NUM>, and a third circumferentially extending depression <NUM> is positioned in the roller body <NUM> adjacent to the second depression. As shown in <FIG> and <FIG>, the first, second and third raised features <NUM>, <NUM> and <NUM> align respectively with the first, second and third depressions <NUM>, <NUM> and <NUM>. Together the raised features <NUM>, <NUM> and <NUM> cooperate with the depressions <NUM>, <NUM> and <NUM> to roll form the pipe element as described below.

The depressions <NUM>, <NUM> and <NUM> shown in <FIG>, <FIG> and <FIG> are in part defined by first, second and third lands <NUM>, <NUM> and <NUM>. First land <NUM> is positioned between the first and second depressions <NUM> and <NUM>, the second land <NUM> is positioned between the second and third depressions <NUM> and <NUM> and the third land <NUM> is positioned on roller body <NUM> adjacent to the third depression <NUM>. First, second and third lands <NUM>, <NUM> and <NUM> advantageously have substantially flat, relatively broad surfaces <NUM> which engage the pipe element during roll forming. Land surfaces <NUM> may be knurled to provide purchase between the inner roller <NUM> and the pipe element to facilitate rotation of the pipe element without significant slippage between it and the inner roller <NUM> when the inner roller is the driven roller as described below. In the example inner roller <NUM> shown in <FIG>, the first land <NUM> has a land surface <NUM> similar to the second and third lands <NUM> and <NUM>. However, in the example inner roller <NUM> of <FIG> and <FIG>, the first land <NUM> comprises a projection <NUM> that extends circumferentially around inner roller body <NUM> and project radially from axis <NUM>. Projection <NUM> has a maximum diameter <NUM> greater than the maximum diameter of the remaining portion of the inner roller <NUM> except for flange <NUM>. Projection <NUM> cooperates with the second raised feature <NUM> to roll form pipe elements having a circumferential groove wherein a side surface of the groove projects beyond the surface of the pipe element as described below. Comparison of <FIG> and <FIG> shows respective contact widths 40a on projection <NUM> and 84a on projection <NUM>. Contact widths 40a and 84a are the linear distance over which the projections <NUM> and <NUM> contact the pipe element during roll forming. It has been determined that the relative size of these two contact widths 40a and 84a controls the height of enlargement of the groove side surface beyond the surface of the pipe as described below.

Another embodiment of inner roller <NUM> is shown in <FIG>. In this embodiment, inner roller <NUM> comprises a body <NUM> having a flange <NUM>, and first and second depressions <NUM> and <NUM> separated from one another by a land <NUM>.

Operation of the roller set <NUM> is illustrated in <FIG>. As shown in <FIG>, inner roller <NUM> is the driven roller (rotated, for example by an electric motor, not shown) and outer roller <NUM> is an idler. The outer roller <NUM> is positioned on an adjustable yoke <NUM> allowing the outer roller to be moved toward and away from the inner roller <NUM>. Yoke <NUM> is advantageously movable by a hydraulic actuator (not shown) but other types of actuators are also feasible. With the outer roller <NUM> moved away from the inner roller <NUM>, an inner surface <NUM> of the pipe element <NUM> is positioned on the inner roller <NUM>. It is advantageous for the longitudinal axis <NUM> of pipe element <NUM> to be angularly oriented initially with respect to the axis of rotation <NUM> of the inner roller <NUM>. Relative orientation angles <NUM> from about <NUM>° to about <NUM>° are effective for keeping the pipe element <NUM> reliably in contact with the roller set, as it is found that the pipe element <NUM>, pinched between the rollers <NUM> and <NUM>, will be drawn toward the flange <NUM> as the rollers rotate if an orientation angle <NUM> between the longitudinal axis <NUM> of the pipe element <NUM> and the inner roller <NUM> is maintained. Formation of the groove retains the pipe element <NUM> in engagement with the roller set <NUM> during roll forming by mechanical engagement. If, however, the angle <NUM> of the axis <NUM> of pipe element <NUM> relative to the axis <NUM> is permitted to reverse before the groove begins to form then the pipe element will spiral out of engagement with the roller set if not forcibly restrained.

As shown in <FIG>, with axis <NUM> of outer roller <NUM> and axis <NUM> of inner roller <NUM> substantially parallel to one another, outer roller <NUM> is moved into contact with the outer surface <NUM> of pipe element <NUM>. As shown in detail in <FIG>, there are three initial points of contact between the roller set <NUM> and the pipe element <NUM> as follows: point <NUM> between the second raised feature <NUM> and the outer surface <NUM>; point <NUM> between the pipe element inner surface <NUM> and the projection <NUM> of inner roller <NUM>; and point <NUM> between pipe element inner surface <NUM> and third land <NUM> of inner roller <NUM>. As shown in <FIG>, the outer roller <NUM> is moved via yoke <NUM> toward the inner roller <NUM> as the roll set <NUM> and pipe element <NUM> rotate to roll form the pipe element. Rotation is effected by driving the inner roller <NUM> about axis <NUM> in this example, which causes the pipe element <NUM> and outer roller <NUM> to rotate about axes <NUM> and <NUM> respectively. As shown in <FIG>, as the pipe element <NUM> deforms due to contact with second raised feature <NUM>, the first raised feature <NUM> begins to engage the pipe element <NUM> at or near its end, for example to prevent the end from flaring (shown) or to burnish a portion of the surface as would occur if the outer roller <NUM> of <FIG> were used. Forced contact between the first raised feature <NUM> and the end of the pipe element <NUM> may cause the pipe element to teeter about the projection <NUM> on inner roller <NUM> and lift off of the contact point <NUM> (between inner surface <NUM> and third land <NUM>). This teetering action may reverse the orientation angle <NUM> between the pipe element's longitudinal axis <NUM> and the axis <NUM> of the inner roller <NUM> (see <FIG>) and cause the pipe element to spiral out of contact with the roller set <NUM>. Relatively short pipe elements (<NUM>-<NUM> feet or less) are particularly prone to this phenomenon. However, contact between the third raised feature <NUM> and the outer surface <NUM> of the pipe element <NUM> counteracts this tendency for the pipe element to teeter and prevents the orientation angle <NUM> from reversing so that the pipe element <NUM> tracks toward the flange <NUM> and stays in contact with the roller set. Contact between the third raised feature <NUM> and the outer surface <NUM> of the pipe element <NUM> may first occur when the groove is about <NUM>% to <NUM>% formed. <FIG> shows the formation of a circumferential groove <NUM>, wherein the first, second and third raised features <NUM>, <NUM> and <NUM> are aligned with the first, second and third depressions <NUM>, <NUM> and <NUM>, the raised features and depressions cooperating with one another to roll form the pipe element <NUM>. The third raised feature <NUM> also forms a tooling mark <NUM> in the outer surface <NUM> of the pipe element <NUM>. Tooling mark <NUM> extends circumferentially around the pipe element and may comprise a relatively shallow depression and/or embossed indicia that identify the model number and/or source of the product. The tooling mark may also provide evidence or guidance for proper installation of the pipe element relative to a coupling.

Timing of contact between the various raised features <NUM>, <NUM>, <NUM> and the outer surface <NUM> of pipe element <NUM> is controlled mainly by the geometry of the outer roller <NUM> including the relative diameters of the first and third raised features <NUM> and <NUM>. The geometry of the outer roller <NUM> for a particular size pipe element <NUM> may be arranged to ensure that, for example, the first raised feature <NUM> contact the pipe element before the third raised feature <NUM>, or the third raised feature contacts the pipe element before the first raised feature, or both the first and third raised features contact the pipe element substantially simultaneously. As shown in a comparison of <FIG> and <FIG>, the geometry of the outer roller <NUM> may also be tailored so that the first raised feature <NUM> contacts the pipe element substantially at an end thereof (<FIG>), or over a region of the pipe element in spaced relation to the end (<FIG>). The geometry of raised feature <NUM> of outer roller <NUM> shown in <FIG> is useful for preventing or mitigating flare of the pipe element <NUM>, and can also be used to roll form a conical taper to the end of a pipe element. The geometry of raised feature <NUM> of outer roller <NUM> shown in <FIG> is useful for burnishing a portion of the outer surface <NUM> of the pipe element <NUM> to provide a smooth surface that facilitates a fluid tight seal with a gasket as described below. It is expected that surface finishes with a roughness (Ra) from about <NUM>µin to about <NUM>µin (as measured according to ASME Y14. <NUM>) will be achievable using roller sets herewith described, and that this range of surface roughness will provide an interface affording a fluid tight seal between the pipe element and the gasket.

<FIG> show example pipe elements roll formed using roller sets <NUM>. As shown in <FIG>, pipe element <NUM> has an end <NUM> and comprises a sidewall <NUM> between outer surface <NUM> and inner surface <NUM>. Circumferential groove <NUM> is positioned in the outer surface <NUM> and comprises a first side surface <NUM> proximate to end <NUM>, a floor surface <NUM> contiguous with the first side surface <NUM>, and a second side surface <NUM> contiguous with the floor surface <NUM> and in spaced relation to the first side surface <NUM>. In this example pipe element the floor surface <NUM> is oriented substantially parallel to axis <NUM> and the second side surface <NUM> is oriented angularly with respect thereto. The first side surface <NUM> projects radially outwardly beyond the outer surface <NUM> of the pipe element <NUM> in its entirety. This configuration of the first side surface <NUM> is achieved by interaction between the projection <NUM> on inner roller <NUM> and the second raised feature <NUM> on the outer roller <NUM> during roll forming. It has been determined that the configuration of the first side surface <NUM> is significantly affected by the relative size of the contact width 84a (see <FIG>) between projection <NUM> of inner roller <NUM> and the inner surface <NUM> of the pipe element <NUM>, and the contact width 40a (see <FIG>) between the projection <NUM> on the outer roller <NUM> and the outer surface <NUM> of the pipe element. Specifically, it is found that making the contact width 84a of projection <NUM> on inner roller <NUM> narrower than the contact width 40a of projection <NUM> on outer roller <NUM> forms side surface <NUM> so that it projects radially outwardly beyond the outer surface <NUM> of the pipe element <NUM> in its entirety as desired. The projecting side surface <NUM> significantly improves the performance of the pipe element with respect to pressure capability and bending stiffness and strength when mechanical couplings are used to join pipe elements having projecting side surfaces <NUM> as shown in <FIG>. Tests have shown a factor of three improvement in maximum pressure to failure and significant improvement is expected in bending capability as well. The effects are manifest for pipe elements having a thin sidewall <NUM>, for example up to about <NUM> inches (<NUM>). Similar improvement in performance is also expected for pipe elements having sidewall thicknesses as great as ½ to ¾ inches. <FIG> also shows pipe element <NUM> having a conically tapered end <NUM> formed using the outer roller <NUM> shown in <FIG>. The advantages to tapering the pipe end <NUM> are that flare is eliminated and the outer diameter of the pipe element is controllable to a much smaller tolerance than the normal manufacturing tolerances. The tapered end serves as a lead in during assembly, and promotes insertion by exerting a prying force to separate the coupling segments.

<FIG> shows a pipe element <NUM> having an end <NUM> and comprising a sidewall <NUM> between outer surface <NUM> and inner surface <NUM>. A circumferential groove <NUM> is positioned in the outer surface <NUM> and comprises a first side surface <NUM> proximate to end <NUM>, a floor surface <NUM> contiguous with the first side surface <NUM>, and a second side surface <NUM> contiguous with the floor surface <NUM> and in spaced relation to the first side surface <NUM>. In this example pipe element the first and second side surfaces <NUM> and <NUM> are oriented substantially perpendicularly to the axis <NUM> and the floor surface <NUM> is oriented substantially parallel thereto. <FIG> also shows pipe element <NUM> having a burnished surface <NUM> positioned between the groove <NUM> and the end <NUM> of the pipe element. In this example pipe element the burnished surface <NUM> is oriented substantially parallel to the axis <NUM> and is positioned in spaced relation away from the end <NUM> of the pipe element <NUM>. The advantage to including a burnished surface region on the pipe element is that it provides a sealing surface, i.e., a smooth surface to accept a seal. This ensures that a fluid tight joint is created when the pipe elements are joined by a mechanical coupling as described below. It is advantageous to control the diameter <NUM> of the burnished surface <NUM>. In one example, the tolerance on the diameter <NUM> may be substantially equal to the tolerance on the diameter <NUM> of the groove floor surface <NUM>. In another example, the tolerance on the diameter <NUM> of the burnished surface <NUM> may be from about <NUM>% to about <NUM>% of the tolerance on the pipe element diameter <NUM>, the actual tolerance varying as a function of the size of the pipe element.

<FIG> and <FIG> illustrate, in combination, pipe elements <NUM> joined end to end via a mechanical coupling <NUM>. Coupling <NUM> comprises a plurality of segments <NUM>, in this example two segments, attached end to end and surrounding a central space <NUM>. Connection members <NUM>, in this example comprising projections <NUM>, are positioned on opposite ends of each segment <NUM>. The connection members effect a connection between the segments and are adjustably tightenable to draw the segments toward one another. In this example adjustable tightening is effected by bolts <NUM> and nuts <NUM> that are received within aligned holes <NUM> in each projection <NUM>.

As shown in <FIG>, each segment <NUM> further comprises at least one key <NUM>. Keys <NUM> project toward the central space <NUM> and each key engages a groove <NUM> in pipe elements <NUM>. <FIG> shows an example combination of coupling <NUM> and pipe elements <NUM> joined in end to end relation wherein the keys <NUM> each comprise a first key surface <NUM> engaged with the first side surface <NUM> of groove <NUM>; a second key surface <NUM>, contiguous with the first key surface and facing the floor surface <NUM> of the groove <NUM>, and a third key surface <NUM>, contiguous with the second key surface and engaged with the second side surface <NUM> of groove <NUM>. In the example combination of <FIG>, the key surfaces <NUM>, <NUM> and <NUM> have the same orientation as the corresponding surfaces <NUM>, <NUM> and <NUM> that they engage. Thus the first key surface <NUM> and the first side surface <NUM> are oriented substantially perpendicularly with respect to the longitudinal axis <NUM> of the pipe elements <NUM>, the second key surface <NUM> and the floor surface <NUM> are substantially parallel to the axis <NUM>, and the third key surface <NUM> and the second side surface <NUM> are oriented angularly with respect to axis <NUM>. <FIG> also shows an example combination embodiment wherein the first side surface <NUM> projects radially outwardly beyond the outer surface <NUM> of the pipe element <NUM> in its entirety, as would be formed by the roller set <NUM> shown in <FIG>. This is a high performance joint for pressure and bending moment loading by virtue of the radially projecting first side surface <NUM> of the groove <NUM>. <FIG> also shows a conically tapered end <NUM> of pipe element <NUM>, wherein flare was eliminated and the pipe element diameter at the end is controlled to a tighter tolerance than provided during manufacture of the pipe element.

Claim 1:
In combination, at least one pipe element (<NUM>) and a coupling (<NUM>); said pipe element comprising;
an outer surface (<NUM>) surrounding a longitudinal axis (<NUM>);
at least one end (<NUM>);
a groove (<NUM>) positioned in said outer surface proximate to said at least one end, said groove extending circumferentially around said pipe element, said groove comprising:
a first side surface (<NUM>) proximate to said at least one end;
a floor surface (<NUM>) contiguous with said first side surface;
a second side surface (<NUM>) contiguous with said floor surface, said second side surface being in spaced relation to said first side surface; and wherein
said first side surface projects radially outwardly beyond a remainder of said outer surface (<NUM>) of said pipe element (<NUM>); and
a tooling mark (<NUM>) positioned in said outer surface and extending circumferentially around said pipe element and said coupling (<NUM>) comprising:
a plurality of segments (<NUM>) attached end to end surrounding a central space (<NUM>), said at least one pipe element being received within said central space; each of said segments having at least one key (<NUM>; <NUM>) projecting toward said central space, said at least one key engaging said groove (<NUM>), said at least one key comprising:
a first key surface (<NUM>; <NUM>) engaged with said first side surface of said groove;
a second key surface (<NUM>; <NUM>) contiguous with said first key surface and facing said floor surface (<NUM>) of said groove; and
a third key surface (<NUM>; <NUM>) contiguous with said second key surface, said third key surface (<NUM>) facing said second side surface of said groove;
characterized in that
the tooling mark (<NUM>) comprises a shallow depression and/or embossed indicia for guidance for proper installation of the pipe element relative to the coupling.