Pipe flange

A pipe flange (10) comprising: a circular flange plate (12) having a central (hub 14) for attaching the flange plate (12) to an end of a pipe (16), the hub (14) having a first annular portion (18) with a first inside diameter adapted to closely receive the outside diameter of the end of the pipe (16) therein. The pipe flange (12) also comprises a second annular portion formed by an annular lip (20) with a second inside diameter substantially equal to or greater than the inside diameter of the end of the pipe wherein, in use, a weld can be applied around the inside circumference of the hub (14) between the annular lip (20) and the end of the pipe.

FIELD OF THE INVENTION

The present invention relates to an improved pipe flange and relates particularly, though not exclusively, to a slip-on flange.

BACKGROUND TO THE INVENTION

Pipe flanges are typically a plate or ring that forms a rim at the end of a pipe for joining the pipe to another pipe or fitting. The flange typically has a series of bolt holes provided about its circumference to permit the pipe to be fastened at the joint. A flange joint refers to the connection of two pipes end to end, where the connecting pieces each have a flange by which the end of the pipes are bolted together. Typically a rubber gasket is provided between the faces of the adjoining flanges of a flange joint. It is important that the faces of the adjoining flanges be as smooth and flat as possible in order to ensure a proper seal at the joint.

A slip-on flange is typically connected to the end of the pipe by fillet welding around the circumference of the pipe where it meets the flange on both the inside and outside circumferences. On the inside circumference it is necessary to grind the weld back to the same inside diameter as the pipe. It may also be necessary to radius the inside edge of the welded region in order to provide a smooth transition from the inside of the pipe to the face of the flange, e.g. for rubber-lined pipes. The grinding and radiusing of the welded region around the inside diameter is labour-intensive and therefore expensive. It is also difficult to control the quality of the finish, so that the finished product may not be sufficiently smooth and/or flat.

Pipe flanges are manufactured in a variety of shapes and sizes according to various international standards. In mineral processing, oil and gas, chemical and water plants, steel pipe for carrying slurry and/or fluids and/or chemicals may be rubber-lined or ceramic-lined. With lined pipes it is important that the lining material also extend over the welded region to prevent any weakness or susceptibility to increased wear or corrosion in this region.

The present invention was developed with a view to providing a pipe flange that is easier to weld to the end of a pipe and that enables a better finish to be achieved. Although the invention is described with particular reference to a slip-on flange it will be apparent that the invention may also be applicable to other types of pipe flange, e.g. a lap joint flange.

References to prior art in this specification are provided for illustrative purposes only and are not to be taken as an admission that such prior art is part of the common general knowledge in Australia or elsewhere.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a pipe flange comprising:

a circular flange plate having a central hub for attaching the flange plate to an end of a pipe, the hub having a first annular portion with a first inside diameter adapted to closely receive the outside diameter of the end of the pipe therein, and a second annular portion formed by an annular step with a second inside diameter greater than the inside diameter of the end of the pipe but less than the outside diameter of the pipe wherein, in use, the end of the pipe abuts against an edge of this annular step and a weld can be applied between an inside face of the annular step and the end of the pipe.

A primary advantage of this arrangement is that, if necessary, the welded region on the inside circumference of the hub can be more easily ground back to the inside diameter of the pipe and the front face of the flange plate is unaffected.

Preferably an annular gap is provided between the annular tip-step and the end of the pipe to accommodate the weld material.

Advantageously the hub is provided with a third annular portion formed by an annular lip having a third inside diameter substantially equal to or greater than the inside diameter of the end of the pipe.

Advantageously the annular gap is at least partly formed by shaping a wall of the annular lip facing the end of the pipe. Preferably the wall of the annular lip facing the end of the pipe is bevelled to form an annular face of increased surface area facing the end of the pipe.

Preferably the annular gap is also formed by spacing the end of the pipe from the annular lip.

In one embodiment the second annular portion extends to a front face of the flange plate. In an alternative embodiment the third annular portion extends to a front face of the flange plate. In one embodiment a surface of the annular lip where it joins the front face of the flange plate is radiused so that it forms a rounded or curved edge.

Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. Likewise the word “preferably” or variations such as “preferred”, will be understood to imply that a stated integer or group of integers is desirable but not essential to the working of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A first embodiment of a pipe flange10in accordance with the invention, as illustrated inFIGS. 1 and 2, comprises a circular flange plate12having a central hub14for attaching the flange plate12to the end of a pipe16. The hub14has a first annular portion18with a first inside diameter adapted to closely receive the outside diameter of the end of the pipe16therein. A third annular portion is formed by an annular lip20, with a third inside diameter substantially equal to the inside diameter of the end of the pipe16. Preferably the third annular portion or annular lip20extends to a front face of the flange plate12. In this embodiment a front edge28of the annular lip20, where it joins the front face of the flange plate12, is radiused so that it forms a rounded or curved edge, as can be seen most clearly inFIGS. 1 (b)and2(b).

In use, a weld can be applied around the inside circumference of the huh14between the annular lip20and the end of the pipe16. In this embodiment the weld is in the form of a butt weld between a perpendicular face22of the annular lip20(seeFIG. 1(b)) and the end of the pipe16. A primary advantage of this configuration of the pipe flange10is that, if necessary, any weld material protruding from between the annular lip20and the perpendicular face22on the inside circumference of the hub14can be more easily ground back to the inside diameter of the pipe16, and the front face of the flange12remains unaffected. Hence when a rubber lining26is applied to the inside of the pipe16, as shown inFIG. 2 (a)the welded region on the inside of the hub14is smooth and can be properly coated to protect the weld joint from wear and/or corrosion. On the other hand the rounded edge28on annular lip20provides a smooth surface at the transition from the inside of the annular lip20(and pipe16) to the front face of the flange plate12(seeFIG. 2 (b)).

Typically a second fillet weld is applied around the outside circumference of the pipe16and the rear edge of hub14in weld region24(seeFIG. 1 (b)). In some circumstances, even though a weld can be applied around the inside circumference of the hub14, between the annular lip20and the end of the pipe, it may not be. In this case, a weld is only applied around the outside circumference of the pipe16and the rear edge of hub14in weld region24.

FIGS. 2(c) and 2(d)illustrate a variation of the first embodiment of the pipe flange10in which an annular gap27is provided between the annular lip20and the end of the pipe16to accommodate the weld material. The annular gap27is formed by spacing the end of the pipe16from the annular lip20by a predefined spacing. To this end, the hub14is provided with a third second annular portion or annular step28having a second inside diameter smaller than the first inside diameter, but larger than the third inside diameter whereby, in use, the end of the pipe16abuts against an edge29of this second annular portion28so as to space the end of the pipe16from the perpendicular face22of annular lip20. One advantage of the second annular portion or step28is that the spacing of annular gap27remains constant, so that weld material can be more readily applied to weld the end of the pipe16to the inside circumference of the hub14of the pipe flange10.

A second embodiment of a pipe flange30in accordance with the invention, as illustrated inFIGS. 3 and 4, comprises a circular flange plate32having a central hub34for attaching the flange plate32to the end of a pipe16. The hub34has a first annular portion38with a first inside diameter adapted to closely receive the outside diameter of the end of the pipe16therein. A third annular portion is formed by an annular lip40, with a third inside diameter substantially equal to the inside diameter of the end of the pipe16. Preferably the third annular portion or annular lip40extends to a front face of the flange plate32. In this embodiment a front edge36of the annular lip40, where it joins the front face of the flange plate32, is also radiused so that it forms a rounded or curved edge, as can be seen most clearly inFIGS. 3 (b)and4(b).

In this embodiment an annular gap42is provided between the annular lip40and the end of the pipe16to accommodate the weld material44(seeFIG. 4 (b)). Advantageously the annular gap42is at least partly formed by shaping a wall46of the annular lip40facing the end of the pipe. Preferably the wall46of the annular lip40facing the end of the pipe is bevelled to form an annular bevelled face46of increased surface area facing the end of the pipe. During welding with a butt weld received in the annular gap42, the weld material44welds to the face46, as well as to the end of the pipe16. Any weld material44protruding above the inside surface of the pipe16can then be readily ground back to the inside diameter of the pipe and the annular lip40to provide a smooth finish.

In this embodiment, the annular gap42is also formed by spacing the end of the pipe16from the annular lip40by a predefined spacing. To this end, the hub34is provided with a second annular portion50having a second inside diameter smaller than the first inside diameter, but larger than the third inside diameter whereby, in use, the end of the pipe16abuts against an edge48of this second annular portion50so as to space the end of the pipe16from the bevelled face46annular lip40. The advantage of the second annular portion50is that the spacing remains constant for each pipe flange30, and therefore the pipe16can be cut a fixed length, as required, to allow for this. This spacing provides an enlarged annular gap42within which a butt weld can be readily applied to weld the end of the pipe16to the inside circumference of the hub34of the pipe flange30.

Typically a second fillet weld is applied to the outside circumference of the pipe16and the hub34in weld region52(seeFIG. 4 (b)).

As with the previous embodiment, when a rubber lining26is applied to the inside of the pipe16, as shown inFIG. 4 (a), the welded region on the inside circumference at the join is smooth and can be properly coated to protect the weld joint from wear and/or corrosion. On the other hand the rounded edge36on annular lip40provides a smooth surface at the transition from the inside of the annular lip40(and pipe16) to the front face of the flange plate32(seeFIG. 4 (b)).

A third embodiment of a pipe flange60in accordance with the invention, as illustrated inFIGS. 5 and 6, is similar in many respects to the second embodiment, described above with reference toFIGS. 3 and 4. Therefore the same reference numerals will be used to identify the like parts in the third embodiment, and these will not be described again in detail. The main difference between this embodiment of the pipe flange60and the previous embodiment is that the front edge62the annular lip40is not radiused, but is simply kept as a right angle edge. The reason the front edge62is kept at a right angle is because in this instance the inside surface of the pipe16and hub34is lined with a ceramic lining64(seeFIG. 6 (a)).

As with the second embodiment, an annular gap42is provided between the annular lip40and the end of the pipe16to accommodate the weld material44(seeFIG. 6 (b)). The annular gap42is partly formed by bevelled face46of the annular lip40facing the end of the pipe16, and partly formed by spacing the end of the pipe16from the annular lip40by a predefined spacing. To this end, the hub34is provided with a second annular portion50, similar to the second embodiment of the pipe flange30.

A fourth embodiment of a pipe flange80in accordance with the invention, as illustrated inFIGS. 7 and 8, is similar in many respects to the first embodiment, described above with reference toFIGS. 1 and 2. Therefore the same reference numerals will be used to identify the like parts in the fourth embodiment, and these will not be described again in detail. The main difference between this embodiment of the pipe flange80and the first embodiment is that the front edge82the annular lip20is not radiused, but is simply kept as a right angle edge. The reason the front edge82is kept at a right angle is because in this instance also the inside surface of the pipe16and hub14is lined with a ceramic lining84(seeFIG. 8 (a)).

As with the first embodiment, a weld in the form of a butt weld is applied between a perpendicular face22of the annular lip20and the end of the pipe16(seeFIGS. 7 (b)and8(b)).

FIGS. 8(c) and 8(d)illustrate a variation of the fourth embodiment of the pipe flange80in which an annular gap86is provided between the annular lip20and the end of the pipe16to accommodate the weld material. The annular gap86is formed by spacing the end of the pipe16from the annular lip20by a predefined spacing. To this end, the hub14is provided with a second annular portion or annular step88having a second inside diameter smaller than the first inside diameter, but larger than the third inside diameter whereby, in use, the end of the pipe16abuts against an edge89of this second annular portion88so as to space the end of the pipe16from the perpendicular face22of annular lip20.

A fifth embodiment of a pipe flange90in accordance with the invention, as illustrated inFIG. 9, is similar in many respects to the fourth embodiment, described above with reference toFIGS. 7 and 8. Therefore the same reference numerals will be used to identify the like parts in the fifth embodiment, and these will not be described again in detail. The main difference between this embodiment of the pipe flange90and the fourth embodiment is that the second annular portion or step88extends all the way to a front face of the pipe flange. The annular step88has an inside diameter which is greater than the inside diameter of the pipe16, but less than the outside diameter of the pipe16. The effect of extending the step88is to expose an end face94of the pipe16so as to form an annular gap between this end face94of the pipe and an inside face92of the annular step88. A fillet weld can be readily applied to the end face94of the pipe16to weld the end of the pipe16to the inside face92of the annular step88—(seeFIG. 10(b)). A second weld is typically also applied around the outside circumference of the pipe16adjacent to the rear edge of the hub14in the weld region marked96inFIG. 9(b)(seeFIG. 10(b)).

Another difference between this embodiment of the pipe flange90and the fourth embodiment is the provision of a raised annulus98on the front face of the pipe flange, as can be seen most clearly inFIG. 9 (b). The raised annulus98is provided to support a gasket (not shown), when the flange plate90is bolted to another flange plate. The provision of the raised annulus98on the front face of the pipe flange90is for illustrative purposes only. The same kind of raised annulus may be provided on the front face of any of the other embodiments of the pipe flange described herein.

A sixth embodiment of a pipe flange100in accordance with the invention, as illustrated inFIG. 10, is similar in many respects to the fifth embodiment, described above with reference toFIG. 9. Therefore the same reference numerals will be used to identify the like parts in the sixth embodiment, and these will not be described again in detail. The main difference between this embodiment of the pipe flange100and the fifth embodiment is that the central hub104of the flange plate102does not have an annular portion that protrudes rearward of the flange plate, as in the previous embodiments. Hence a rear face of the flange plate102is substantially coplanar with a rear face of the hub104. In other respects the pipe flange100of this embodiment is substantially identical to the flange plate90ofFIG. 9. A fillet weld99is preferably applied to the end face94of the pipe16to weld the end of the pipe16to the inside face92of the annular step88, and a second weld99is typically applied around the outside circumference of the pipe16adjacent to the rear edge of the hub104.

The present invention is applicable to slip-on flanges of all sizes, but is typically applicable to flanges for pipes having an inside diameter of 2 inches or larger.

Now that several embodiments of the pipe flange have been described in detail, it will be apparent that the described embodiments provide a number of advantages over the prior art, including the following:(i) There is a significantly reduced amount of work required to fit and weld the flange to the end of the pipe, and to subsequently grind the weld material back to the inside diameter of the pipe.(ii) The quality of the surface on the inside circumference of the pipe and hub at the join can be better controlled to provide a smooth finish for both rubber and ceramic lined pipes.(iii) There is no need to radius the front edge of the weld material where it joins the pipe to the hub, as in the prior art, and the radiused front edge of the annular lip provides a smooth transition to the front face of the flange plate.(iv) The improved surface finish and smooth, flat surfaces provide better integrity of any seal between the front face of the flange plate and an adjoining surface.(v) Improved life expectancy of the pipe at the flange joint reduces maintenance costs and down times.

It will be readily apparent to persons skilled in the relevant arts that various modifications and improvements may be made to the foregoing embodiments, in addition to those already described, without departing from the basic inventive concepts of the present invention. For example, the surface on the annular lip facing the end of the pipe may be of any suitable shape and is not limited to the bevelled surface of the illustrated embodiments. Therefore, it will be appreciated that the scope of the invention is not limited to the specific embodiments described.