GB1595648A - Flange coupling - Google Patents

Description

(54) FLANGE COUPLING (71) We. HEDINS MEKANISKA VERKSTAD AB, a Swedish Company of Kavelvagen 8, S-890 23 Sjalevad, Sweden, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a flange coupling for connecting a pipe to a sealing-face, comprising a fixed flange component fitted around the end of the pipe, and a loose flange ring bearing on the fixed flange component and serving to press the flange against a sealingface. The invention also includes a method for producing the flange coupling.

Flange couplings are used for attaching fittings apparatus etc. to pipes. The flange coupling is welded to the pipe, and other components are then screwed to the flange coupling.

The conventional design of flange couplings as described above entails making the fixed flange ring with comparatively large dimensions in relation to the pipe. As the flange ring is often made of expensive material, such as stainless steel, the conventional design has economic drawbacks.

According to the present invention there is provided in a flange coupling at an end of a metal pipe: a fixed metal flange, at the end of the pipe, of substantially the same material thickness as the material of the pipe, the flange extending outwardly of the pipe so as to exhibit a forwardly facing seating surface and a rearwardly facing surface, a metal pressing ring fitted around the pipe with very little play therebetween and engaging the rearwardly facing surface of the fixed flange, and a clamping flange ring loosely surrounding the pipe, the clamping flange ring having holes therethrough parallel to the pipe for receiving fastening members for connecting the pipe to another structure, the clamping flange ring when so connected bearing against the pressing ring so that the latter transmits force between the flange ring and the fixed flange.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows the conventional prior art design, and Figure 2 shows a coupling designed in accordance with the invention.

A conventional flange coupling, as illustrated in Figure 1, consists of two main parts, namely a fixed flange 1 and a loose flange 2, in which screws (not shown) are fitted and tightened. The force exerted by the screws is transmitted from the loose flange ring 2 to the fixed flange ring 1, which brings about the seal. The fixed flange ring 1 is welded to a connecting pipe ring 4 on the end of the main pipe 3 and the loose flange 2 is tightened against the fixed flange ring 1. This design of flange coupling is used in the chemical industry, and therefore the flange ring 1, the pipe 3, and the connecting pipe ring 4 are made of materials resistant to chemical attack for example, stainless steel, titanium, nickel etc., while the loose flange ring 2 is made of high-carbon steel. The dimensions of the flange ring 1 and the connecting pipe ring 4, to which the flange ring 1 is attached, are determined by the moment of the force Pa and the lever X. The force Pa is a function of the pressure inside the pipe and the distance X is prescribed by the standard Tryckkarlsnormer 1973 (Pressure Vessel Standards, 1973). The result of this is that both the flange ring 1 and the pipe ring 4 are of considerable size compared to the attached pipe 3.

The coupling of the present invention, illustrated in Figure 2, consists of a fixed flange ring 5 with a pressed pipe ring 6 of chemically resistant material, the same as that of the pipe 7, to which it is attached by welding. Disposed about the fixed flange ring 5 is a fixed "pressing ring" 8 of high-carbon steel and, as in the conventional flange coupling, a loose flange ring 9 in which the screws are fitted is tightened to bring about the seal. However in the present invention, as the screws (not illustrated) are tightened, the force exerted by the screws is transmitted to the pressing ring 8, which in its turn presses on the fixed flange ring 3 and brings about the seal. In view of the presence of the pressing ring 8, the force Pa gives rise to a tensile force only in the ring 6, since the angular displacement of the pressing ring 8 does not result in any bending moment in the pipe ring 6. The latter is therefore made in the same dimensions as the main pipe 7 to which it is attached. In the arrangement of the present invention the flexural stresses, present in the pipe ring 6 in the conventional flange coupling, are entirely taken up by the pressing ring 8, which is dimensioned to absorb the moment Pa X X. The design of the invention results in a 503--70% saving of the expensive resistant material, while retaining the strength of the coating, due to the use of inexpensive high-carbon steel in the pressing ring 8. The arrangement of the present invention also obviates the two welds between the fixed ring and the pipe ring which are necessary in the conventional flange coupling.

The best results with the present invention are achieved if the pressing ring 8 is fitted with little or no play with respect to the pipe ring 6. Therefore, in a particularly suitable embodiment of the invention, this restricted play is obtained by using the pressing ring 8 as the dye in forming the flange ring 6. In the method a flanged ring is laid on top of the pressing ring 8 and then the pipe ring portion is pressed down into the opening of the pressing ring 8 so that the flanged portion and pipe ring pressed out is made to conform with the contours of the ring 8. This procedure results in very little play between the pressing ring 8 and the pipe ring 6, so that the desired effect is achieved. For example the preferred play may be of the order of a millimeter or less.

WHAT WE CLAIM IS:- 1. In a flange coupling at an end of a metal pipe: a fixed metal flange, at the end of the pipe, of substantially the same material thickness as the material of the pipe, the flange extending outwardly of the pipe so as to exhibit a forwardly facing seating surface and a rearwardly facing surface a metal pressing ring fitted around the pipe with very little play therebetween and engaging the rearwardly facing surface of the fixed flange, and a clamping flange ring loosely surrounding the pipe, the clamping flange ring having holes therethrough parallel to the pipe for receiving fasten ing members for connecting the pipe to another structure, the clamping flange ring when so connected bearing against the pressing ring so that the latter transmits force between the flange ring and the fixed flange.

2. A flange coupling according to claim 1 wherein said fixed flange is provided on one end of a cylindrical pipe ring element of essentially the same diameter and wall thickness as the pipe, the pipe ring being axial with the pipe and welded thereto.

3. A flange coupling according to claim 2 wherein the fixed flange is formed on the pipe ring element by using the pressing ring as a die.

4. A flange coupling substantially as hereinbefore described with reference to and as illustrated in flange 2 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. the angular displacement of the pressing ring 8 does not result in any bending moment in the pipe ring 6. The latter is therefore made in the same dimensions as the main pipe 7 to which it is attached. In the arrangement of the present invention the flexural stresses, present in the pipe ring 6 in the conventional flange coupling, are entirely taken up by the pressing ring 8, which is dimensioned to absorb the moment Pa X X. The design of the invention results in a 503--70% saving of the expensive resistant material, while retaining the strength of the coating, due to the use of inexpensive high-carbon steel in the pressing ring 8. The arrangement of the present invention also obviates the two welds between the fixed ring and the pipe ring which are necessary in the conventional flange coupling. The best results with the present invention are achieved if the pressing ring 8 is fitted with little or no play with respect to the pipe ring 6. Therefore, in a particularly suitable embodiment of the invention, this restricted play is obtained by using the pressing ring 8 as the dye in forming the flange ring 6. In the method a flanged ring is laid on top of the pressing ring 8 and then the pipe ring portion is pressed down into the opening of the pressing ring 8 so that the flanged portion and pipe ring pressed out is made to conform with the contours of the ring 8. This procedure results in very little play between the pressing ring 8 and the pipe ring 6, so that the desired effect is achieved. For example the preferred play may be of the order of a millimeter or less. WHAT WE CLAIM IS:-

1. In a flange coupling at an end of a metal pipe: a fixed metal flange, at the end of the pipe, of substantially the same material thickness as the material of the pipe, the flange extending outwardly of the pipe so as to exhibit a forwardly facing seating surface and a rearwardly facing surface a metal pressing ring fitted around the pipe with very little play therebetween and engaging the rearwardly facing surface of the fixed flange, and a clamping flange ring loosely surrounding the pipe, the clamping flange ring having holes therethrough parallel to the pipe for receiving fasten ing members for connecting the pipe to another structure, the clamping flange ring when so connected bearing against the pressing ring so that the latter transmits force between the flange ring and the fixed flange.

2. A flange coupling according to claim 1 wherein said fixed flange is provided on one end of a cylindrical pipe ring element of essentially the same diameter and wall thickness as the pipe, the pipe ring being axial with the pipe and welded thereto.

3. A flange coupling according to claim 2 wherein the fixed flange is formed on the pipe ring element by using the pressing ring as a die.

4. A flange coupling substantially as hereinbefore described with reference to and as illustrated in flange 2 of the accompanying drawings.