FIRE-RESISTANT PIPE COUPLING

Abstract

The present invention relates to fire-resistant pipe couplings (100) for connecting together two plain-ended pipes in a fluid-tight manner. The pipe coupling (100) comprises: a tubular casing comprising: an outer tubular casing (102); and an inner tubular casing (104), fitting entirely inside the outer casing (102); a tubular sealing gasket (106) disposed within the inner tubular casing (104); and means (116) for tensioning the casing around the gasket (106). The casing further comprises: at least one layer of fire-resistant material (124) disposed between the inner (104) and outer (102) casings; and at least one layer of thermally-insulating material (128) disposed between the tubular sealing gasket (106) and the inner casing (104), whereby the outer casing (102) and tubular sealing gasket (106) are thermally insulated from one another.

Claims

1. A pipe coupling for coupling together two pipes in a fluid-tight manner, comprising: a tubular casing comprising: an outer tubular casing; and an inner tubular casing, fitting entirely inside the outer casing; a tubular sealing gasket disposed within the inner tubular casing; and means for tensioning the casing around the gasket, wherein: the casing further comprises: at least one layer of fire-resistant material disposed between the inner and outer casings; and at least one layer of thermally-insulating material disposed between the tubular sealing gasket and the inner casing, whereby the outer casing and tubular sealing gasket are thermally insulated from one another.

2. A pipe coupling according to claim 1, comprising at least two layers of thermally-insulating material disposed between the tubular sealing gasket and the inner casing.

3. A pipe coupling according to claim 1, wherein the at least one layer of thermally-insulating material is made from mica.

4. A pipe coupling according to claim 1, wherein the at least one layer of thermally-insulating material is between about 0.3 mm and about 1.0 mm thick.

5. A pipe coupling according to claim 1, comprising at least two layers of fire-resistant material disposed between the inner and outer casings.

6. A pipe coupling according to claim 1, wherein the at least one layer of fire-resistant material is made from inorganic materials.

7. A pipe coupling according to claim 6, wherein the inorganic materials include at least silica.

8. (canceled)

9. A pipe coupling according to claim 6, wherein the at least one layer of fire-resistant material is impregnated with vermiculite.

10. (canceled)

11. A pipe coupling according to claim 1, wherein the at least one layer of fire-insulating material is between about 0.5 mm and about 1.5 mm thick.

12. A pipe coupling according to claim 1, wherein the inner and outer casing each have a pair of annular flanges which project radially inwardly from their respective axial edges, the annular flanges of the inner casing being disposed axially inwardly of the annular flanges of the outer casing.

13. A pipe coupling according to claim 12, wherein the or each layer of fire-resistant material is a prepared strip of flexible material having a width greater than the width of the outer casing, such that the material extends radially inward at each annular flange to form a skirt.

14. A pipe coupling according to claim 13, wherein the skirt is configured to extend at least to the outer surface of the pipes being coupled together.

15. A pipe coupling according to claim 14, wherein the skirt is further configured to extend longitudinally away from the casing along the outer surface of the pipes being coupled together.

16. A pipe coupling according to any of claims 12, wherein the or each layer of thermally-insulating material is a prepared strip of flexible material having a width substantially equal to the width of the inner casing between the annular flanges of the inner casing.

17. A pipe coupling according to claim 1, wherein the at least one layer of thermally-insulating material is configured such that, when the coupling is tightened, the inner casing slides over the layer of thermally-insulating material.

18. A pipe coupling according to claim 1, wherein the at least one layer of fire-resistant material is configured such that, when the coupling is tightened, the outer casing slides over the layer of fire-resistant material.

19. A pipe coupling according to claim 1, wherein the at least one layer of fire-resistant material is a prepared strip of material cut to the outer circumference of the inner casing.

20. A pipe coupling according to claim 19, wherein the prepared strip of fire-resistant material is cut with an overlap being about 1% to about 3% of the length of the strip.

21. A pipe coupling according to claim 1, wherein the at least one layer of thermally-insulating material is a prepared strip of material cut to the outer circumference of the gasket.

22. A pipe coupling according to claim 21, wherein the prepared strip of thermally-insulating material is cut with an overlap being about 1% to about 3% of the length of the strip.

23. (canceled)

24. (canceled)

25. (cancelled)

26. (cancelled)

Description

[0054] The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

[0055] FIG. 1 shows a perspective cut-away of a pipe coupling according to the present invention;

[0056] FIG. 2 shows an end view of the coupling of FIG. 1;

[0057] FIG. 3 shows a longitudinal section through the coupling of FIG. 1; and

[0058] FIG. 4 shows a detailed cross-sectional view of a modified coupling of FIG. 1.

[0059] A pipe coupling 100 which comprises an outer tubular casing 102, an inner tubular casing 104, and a tubular sealing gasket 106. The outer tubular casing 102 is formed of rolled steel, with a longitudinal gap 108. The casing is folded back on itself at its free ends and welded at 110 to form loops 112 along opposite edges of the longitudinal gap 108. Pins 114 are inserted in the loops. Tensioning screws 116 pass through transverse holes in one of the pins 114 into tapped transverse holes in the other of the pins 114, so as to interconnect the two free ends of the outer casing 102.

[0060] Slots 118 are cut in the loops 112 so as to provide clearance for the screws. The axial end margins of the casing 102 are bent inwardly at right angles to form annular flanges 120.

[0061] The inner tubular casing 104 is of rolled steel and has a longitudinal gap. The axial end margins of the inner casing 104 are bent inwardly at right angles to form annular flanges 122. The inner casing 104 fits inside the outer casing 102, the axial length of the inner casing 104 being slightly less than that of the outer casing 102 so that the flanges 122 fit inside the flanges 120.

[0062] The gasket is of an elastomeric material, for example rubber or synthetic rubber.

[0063] The outer casing 102 is formed having an internal diameter larger than the external diameter of the inner casing 104, so as to accommodate a fire-resistant layer of material 124. The fire-resistant layer of material is a prepared strip of material cut to the outer circumference of inner casing+1% for overlap and tolerance. The fire-resistant layer may comprise two or more layers of material. In a preferred example, the fire-resistant layer comprises two layers of material, each layer being about 1.0 mm thick. The outer steel casing 102 and inner steel casing 104 are insulated one from the other by the layer of fire-resistant material 124.

[0064] The shaping of the outer casing 102 and inner casing 104 are smooth and identical so that a low friction surface is offered to the fire-resistant material for easy sliding when closing the coupling.

[0065] This is important because a coupling which has only one casing will not provide low friction surfaces between the steel casing and the rubber gasket or sealing sleeve.

[0066] The longitudinal gaps of the outer casing 102 and the inner casing 104 are aligned and a bridge member 126 is provided to complete the circumferential band. This is in order to control the smooth sliding of the fire-resistant layer 124 when closing the coupling. The bridge member 126 is secured to the inner side of the inner casing 104 by spot welding.

[0067] The bridge member 126 subtends an angle of between about 30 degrees and about 40 degrees at the pipe axis. It is secured to the inner casing 104 on one side of the longitudinal gap only and is arranged to overlap the inner casing by approximately equal amounts on either side of the gap in the tightened position.

[0068] In addition to the fire-resistant layer 124, the coupling 100 comprises a thermally-insulating layer of material 128. The inner casing 102 is formed having an internal diameter larger than the external diameter of the gasket 106, so as to accommodate thermally-insulating layer of material 128. The thermally-insulating layer of material is a prepared strip of material cut to the outer circumference of gasket+1% for overlap and tolerance. The thermally-insulating layer may comprise two or more layers of material. In a preferred example, the thermally-insulating layer comprises two layers of material, each layer being about 0.5 mm thick. The inner steel casing 104 and the gasket 106 are insulated one from the other by the thermally-insulating material 128.

[0069] The coupling further comprises a pair of frusto-conical gripping rings 130. Each ring 130 is provided in a corresponding slot formed in the outer surface of the gasket at each axial end. The outer end of each slot lies at the axial end of the outer surface. The slope of the slot is such that the inner end is nearer the axial middle of the gasket than the outer end.

[0070] Each ring 130 is formed from a pair or arcuate segments, and comprises a set of hard teeth to penetrate through the gasket 106 at the bottom of the slot and bite into the surface of the pipe, thereby providing locking of the coupling to the pipe against axial movement. The teeth are designed to make contact at approximately 5 mm centres around the circumference with a width of approximately 2 mm for each tooth, giving approximately 40% contact around the periphery of the pipe.

[0071] Referring now to FIG. 2, the longitudinal gap 200 in the inner casing 104 can be seen, along with the overlap 202 of the fire-resistant layer 124.

[0072] To prevent the two casings rotating relative to one another, anti-rotation notches 204 are provided in the end flanges 120 and 122 of the outer and inner casings which interengage at a point diametrically opposite the gaps 108 and 200 to lock the two casings together. It is important that the two casings do not rotate relative to one another.

[0073] The sealing gasket 106 comprises a series of ribs 300 to achieve a seal which is effective at high hydrostatic pressures, for example 32 bar or even 64 bar. However, the axial length of the gasket that is exposed to the hydrostatic pressure is small compared with the overall axial length of the coupling.

[0074] The fire-resistant layer 124 is made of inorganic materials, preferably predominantly silica. The material is formed from woven silica fibres, and may be impregnated with vermiculite. In addition, the material may be coated with high-temperature resistant polyurethane to reduce the potential for the woven material fraying, and to restrict the ingress of water into the coupling.

[0075] The fire-resistant material is formed in a rectangular strip which is wrapped around the inner casing. The ends of the strip overlap 202 in the region of the gaps 108 and 200.

[0076] The thermally-insulating layer 128 is made of mica. The material of this example is of a mica paper, and is particularly preferred. The mica paper comprises phlogopite and a bonding material. The mica paper contains about 10% bonding material, the bonding material being a silicon resin. The density of the mica paper in this example is about 2.1 kg/m.sup.3.

[0077] During assembly, the complete integral inner casing, including the thermally-insulating layer and the gasket is placed within the outer casing, between which a fire-resistant layer is inserted to insulate the two. It can therefore be seen that the outer casing 102 is insulated from the inner casing 104 by the fire-resistant layer 124, and that the gasket 106 is thermally-insulated from the inner casing 104 by the thermally-insulating layer 128.

[0078] FIG. 4, shows a modified example of the pipe coupling of FIGS. 1 to 3. The pipe coupling 100 is shown in a pre-tightened arrangement on pipe 400. The gasket 106 comprising the ribs 300, is shown to further comprise the extensions 402 which lie between the end face of the annular flange 122 and the outer surface of the pipe 400 to form end seals. Thus liquid and dirt is prevented from entering the coupling from outside.

[0079] The inner casing 104, in this example, has a width less than the internal width of the outer casing 102 between the flanges 120. The reduction in width of the inner casing 102 as compared to the example of FIGS. 1 to 3 is to accommodate a skirt 404 of the fire-resistant layer 124. The skirt extends between the outer casing 102 and the inner casing 104. The skirt has sufficient length that it at least reaches the outer surface of the pipe 400. In other examples (not shown) the skirt may have a length such that it extends away from the coupling and along a portion of the outer surface of the pipe 400.

[0080] By providing a skirt, the external end faces of the coupling, which include a portion of the gasket and the annular flanges 122, are further protected from the flames.

[0081] The coupling of FIG. 4 is the same as described above in all other respects.