Flange, and a method of manufacturing a flange

Abstract

A method of manufacturing at least one flange by first rotating a tubular element and two sheet elements with respect to one another until a radially enlarged portion and adjacent hub section have been formed on the tubular element. The sheet element is impregnated by a thermosetting resin. When the resin has cured, the radially enlarged portion is cut along a cut line, thereby also dividing the tubular element in two parts and generating at least a first flange having a first flange section and a first hub section. Optionally, a second flange having a second flange section and a second hub section, is generated. In a preferred embodiment, the cut line is arranged in the middle of the radially enlarged portion, whereby two similar flanges are generated.

Claims

1. A method of manufacturing at least one flange, comprising the steps of: a) rotating a tubular element and first and second sheet elements with respect to one another such that the first sheet element and the second sheet element are wound alternatingly around the tubular element until a radially enlarged portion and adjacent hub sections have been formed on the tubular element; the sheet element comprising a fibre material impregnated by a thermosetting resin; and b) cutting the radially enlarged portion along a cut line, thereby also dividing the tubular element in two parts and generating at least a first flange having a first flange section and a first hub section.

2. The method of claim 1, wherein step b) additionally comprises simultaneously generating a second flange having a second flange section and a second hub section.

3. The method of claim 1, wherein the thermosetting resin is allowed to cure prior to executing step b).

4. The method of claim 1, wherein the sheet elements are applied onto the tubular element in alternating layers.

5. The method of claim 1, wherein step a) comprises rotation of the tubular element.

6. The method of claim 1, wherein the first sheet element has a width that defines a longitudinal dimension of the radially enlarged portion, and the second sheet element has a width that defines a longitudinal dimension of the radially enlarged portion and the hub sections combined.

7. The method of claim 1, wherein the tubular element is rotated about its longitudinal axis and the cut line is arranged perpendicularly on the longitudinal axis.

8. The method of claim 7, wherein the cut line is arranged in the middle of the radially enlarged portion, whereby step b) generates two similar flanges.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other characteristics of the invention will become clear from the following description of a preferential form of embodiment, given as a non-restrictive example, with reference to the attached drawings, wherein:

(2) FIG. 1 is a perspective view illustrating an embodiment of the method of manufacturing a flange blank;

(3) FIG. 2 is a side view of a flange blank manufactured by the method according to the invention and illustrated in FIG. 1;

(4) FIG. 3 is a side view of an embodiment of two flanges according to the invention, after the blank illustrated in FIG. 2 has been cut;

(5) FIG. 4 is a sectional side view along section line B-B in FIG. 3, illustrating key elements of the invented flange;

(6) FIG. 5a is a schematic and partly cut-away sketch of the tapes used to build the flange blank, and FIG. 5b is similar to FIG. 2, and FIGS. 5a and 5b are arranged so as to illustrate the structure of the flange blank; and

(7) FIG. 6 is similar to FIG. 1, but illustrates an alternative embodiment of the first tape.

DETAILED DESCRIPTION OF A PREFERENTIAL EMBODIMENT

(8) The invention relates to pipes and flanges made of fibre-reinforced, thermosetting synthetic resin. Examples of relevant fibre materials suitable for producing such pipes and flanges are for example glass, carbon, aramid, basalt; or natural fibres such as jute. Relevant literature and prior art use a wide variety of terms, such as fiberglass reinforced plastic, glass reinforced plastic, carbon fibre reinforced plastic, etc. In the following description, the general term fibre-reinforced plastic (FRP) will be used.

(9) FIG. 1 illustrates a part of a method of manufacturing the flange according to the invention. A pipe section 30 is rotated about its longitudinal axis A-A in a direction indicated by the arrow R. The pipe section 30 is supported and rotated by equipment and means which are well known in the art, and therefore need not be illustrated here. The pipe section may for example be a part of an FRP pipe.

(10) A first tape 10 and a second tape 20 are wound onto the pipe section, providing alternating layers of first and second tapes, and progressively building a laminated structure on the pipe section. The tapes 10, 20which for example may be fibre reinforcement tapesare impregnated by a resin (not shown), either before, during or after being wound onto the pipe section. This resin impregnation is well known in the art and therefore not described further. The tapes are wound from storage spools (not shown) on suitable application stations (not shown) adjacent to the pipe section.

(11) Thus, by rotating the pipe section 30 a desired number of turns and using appropriately dimensioned tapes, the circumferential accumulation of the two tapes 10, 20 form a radially enlarged portion 11 and adjacent hub portions 21a,b on the pipe section 30. This is shown in FIG. 1, where the pipe section clearly has been rotated a number of turns in order to build the enlarged portion.

(12) FIG. 2 illustrates the manufactured product when the winding process has been completed. This product in effect constitutes a flange blank 1, from which two flanges may be made by cutting along the line S-S (after the resin has cured). The term flange blank shall in the context of this description mean an element that has been prepared to be made into one or two flanges by a further operation.

(13) The cutting operation separates the flange blank 1 into two hubbed flanges 1a, 1b, shown in FIG. 3. In the illustrated embodiment, the line S-S is a line of symmetry, and the resulting hubbed flanges 1a, 1b are identical. It may, however, be desirable to produce two flanges with different flange thicknesses (e.g. for different pressure classes) from the same flange blank; in which case the line S-S may be moved in the pipe axial direction. It is also within the scope of this invention to make a single flange from the flange blank, e.g. by placing the line S-S at the edge of the radially enlarged portion 11, indicated by T.sub.1 in FIG. 2, cut along that line and discard the right-hand portion.

(14) Each hubbed flange 1a, 1b comprises a flange section 11a, 11b and a hub section 21a, 21b fitted to a pipe member 30a, 30b. The cutting may be performed by any known means, e.g. a saw suitable for cutting cured fibre-reinforced material. In FIG. 3, bolt holes 4 (indicated by dotted lines) extend through both flange sections. The bolt holes may be made in a number of ways, e.g. by drilling (after curing) or by embossing (prior to curing). The bolt holes may be made before or after the flange blank is cut and separated into two hubbed flanges.

(15) The method described above may thus be used to make hubbed flanges with flange sections of any desired axial and radial dimension, with or without holes, such as conventional flanges, van Stone flanges, Puddle flanges, flanges having separate (loose) collars, etc.

(16) While the method of manufacturing the flange blank has been described with reference to a rotating pipe section, it should be understood that the flange blank 1 may also be made by keeping the pipe section stationary, and rotating (winding) the tapes around the non-rotating pipe. A combination (rotating pipe section and counter-rotating tapes) is also envisaged.

(17) It is therefore seen that the element illustrated in FIG. 2 is a blank for making the individual flange sections 11a, 11b shown in FIG. 3. In that cutting process, the first tape 10 and the second tape 20 of the radially enlarged portion 11 are thus split lengthwise (i.e. in the tape longitudinal direction), into respective parts. In the following, these parts will typically be referred to as split tapes, implying that they are split lengthwise

(18) Referring to FIG. 4, a flange section 11a is made up of a split first tape 10a and a split second tape 20a, both wound a number of times around the pipe member 30a. In the illustrated embodiment, the split first tape 10a has half the width of the first tape 10 and the split second tape 20a has half the width of the second tape 20. However, these need not necessarily be halves, if the cut line S-S is placed differently from that shown on FIG. 2 (as discussed above).

(19) In the embodiment illustrated in FIG. 4, the split first tape 10a and the split second tape 20a have been laminated (i.e. wound alternatingly) around the pipe member 30a, as described above with reference to FIG. 1. The respective structures of the two tapes are discussed in more detail below, but FIG. 4 shows that while the split first tape 10a serves to build and define the pipe-axial dimension of the flange section 11a, the split second tape 20a serves to build both the flange section 11a and the hub section 21a and defines the pipe-axial dimension of the hub 21a. The split first tape 10a thus extends from the flange face 5a to a first transition point T.sub.1, where the flange section starts to taper into the hub section. The split second tape 20a also extends from the flange face 5a, but continues past the first transition point T.sub.1 and to a hub section end region E. It should be understood that the slope of the first tapered regions N.sub.1 depends on the tape thicknesses, and the ratio between the thicknesses of the two tapes.

(20) FIG. 4 also indicates an initial reinforcement layer 7 between the outer wall of the pipe member 30a and the split tapes. This reinforcement layer 7, which is optional, may for example be a chop-strand mat reinforced laminate.

(21) The split tapes 10a, 20a are impregnated by a resin (not shown), as described above, in a manner which is well known in the art.

(22) The composition of the tapes used to build the flange will now be discussed in more detail. Reference is made to FIGS. 1, 5a, and 5b.

(23) The first tape 10 (which forms the basis for the split first tape 10a as described above) comprises in the illustrated embodiment of a first ply 12 having longitudinal rovings 121 and a second ply 13 having transverse rovings 131. The first and second plies may be stitched together by a thread (not shown) in a manner which is known in the art, or the plies may in fact be applied as separate tapes, being joined as they are wound around the pipe section 30. Important and desired flange properties that are provided by the first tape 10 are a high flange hoop E-modulus and resistance to torsion. One way of achieving these properties isas indicated by the line density in FIG. 5ato design the first tape 10 with a higher number of rovings oriented in the tape longitudinal direction than in its transverse direction. Another, not illustrated, way of achieving such flange properties is to increase the weight of each of the longitudinal rovings 121. A combination of these two ways is conceivable.

(24) The following non-limiting example illustrates a design where the first ply has fewer but stronger rovings than the second ply, and the resulting ply weight in the longitudinal ply is greater than in the transverse ply: First ply 12, having longitudinal (0) rovings 121 Gauge: 10 rovings/inch Fibre tex: 2400 (i.e. 2.4 g/m) Ply weight: 945 gm.sup.2 Second ply 13, having transverse (90) rovings 131 Gauge: 17 rovings/inch Fibre tex: 300 (i.e. 0.3 g/m) Ply weight: 201 g/m.sup.2

(25) The transverse rovings 131 provide strength in the flange axial direction and provides for improved shear stress distribution. Other angular roving orientations may be used, as applicable.

(26) The first tape 10 is generally narrow (compared to the second tape 20). In the illustrated embodiment where two similar flanges are being made, the first tape has a width that corresponds to twice the axial distance of the two manufactured flange sections. In general, the first tape 10 has a greater weight (g/m.sup.2) than that of the second tape 20, whereby the radially enlarged portion 11 is built up to a greater extent than the hub portions 21a,b. The individual tape weights are chosen according to the desired flange specifications (e.g. flange section width, hub width and taper, flange section diameter).

(27) The second tape 20 (which forms the basis for the split first tape 20a as described above) must be sufficiently wide to cover the axial length of the radially enlarged portion 11 (i.e. the two flange sections 11a,b) and the two hubs 21a,b. It is preferable comparably lighter than the first tape in order to provide the desired flange-to-hub radial thickness ratio.

(28) The second tape 20 is built up of two plies 22, 23 having respective glass rovings 221, 231 oriented at angles with respect to one another. In the illustrated embodiment, the rovings are oriented at of 45 with respect to one another, but the angular orientation may typically be in the range of 30 to 60 relative to the tape direction. The plies 22, 23 of the second tape 20 are stitched together by a thread (not shown) across the width of the tape. Stitching is preferably loose; allowing the second tape to build both hub and flange without creasing.

(29) In FIG. 1, a portion of the first ply 12 of the first tape 10 has been removed to show the second ply 13 underneath, and a portion of the first ply 22 of the second tape 20 has been removed to show the second ply 23 underneath. The sketch in FIG. 5a is built up in a similar manner, in order to illustrate the orientations of the different rovings.

(30) Both FIG. 1 and FIG. 5a illustrate a plurality of threads 232 in the second tape 20, running on both sides of the tape, in a tape-longitudinal direction. These threads 232, which may be manufactured of polyester, provide edge regions of increased longitudinal strength and stiffness, compared to the central region of the second tape. The threads 232 provide a comparably high tensile strength, which allows a use of high tension during the winding procedure. This is a desired property in order to ensure adequate compaction of the laminated flange blank during winding.

(31) The first tape 10 is thus designed in order to build a flange with a high hoop E-modulus, while the threads 232 of the second tape 20 serve as an aid in the process of building the flange.

(32) Referring now to FIG. 6, the first tape 10 as described above may in an alternative embodiment be substituted by a single layer 12 of a plurality of longitudinal rovings 121. The rovings 121 may be stitched together by a thread (not shown) in a manner which is known in the art, in order to stabilize the plurality of threads until they are wound onto the pipe section 30.

(33) While the method of manufacturing described above refer to a laminating process, i.e. winding the first 10 and second 20 tapes alternatingly onto the pipe section 30, it should be understood that the tapes may also be wound onto the pipe section in other ways. For example, it may in certain cases be desirable to wind the first tape a number of turns more than the second tape, in order to build additional flange dimension.

(34) While the method of manufacturing described above and the accompanying drawings show a symmetrical arrangement of the first and second tapes, it should be understood that the second tape 20 may be shifted sideways (i.e. in a pipe-axial direction) with respect to the first tape 10, if it is desired to produce the two hubs with different shapes.

(35) The resins may be any known suitable resin, for example epoxy, vinyl ester, polyester, polyurethane, phenolic.