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Title:
PIPE END SEALING STRUCTURE
Document Type and Number:
WIPO Patent Application WO/2011/141026
Kind Code:
A1
Abstract:
The invention is directed to a pipe end sealing structure (1) comprising a first pipe element (2) having a cylindrical metal pipe body with a first annular end surface (12) at at least one open pipe end adapted to be a sealing support surface, a sealing (4) having a metal sealing body with a first sealing surface (13) facing towards first annular end surface (12) and being adapted to rest at least partially on the first annular end surface (12), a first flange (3) extending radially outwardly from an outer circumference of the first pipe element (2), urging means (7, 8, 9) adapted for urging the sealing (4) and the first flange (3) in an axial direction towards each other, so that the sealing (4) is urged with its first sealing surface (13) against the first annular end surface (12) of the first pipe element (1), wherein the first annular end surface (12) of the cylindrical metal pipe body is a tapered annular surface (12) and the first sealing surface (13) of the metal sealing body is a conical inner circumferential surface (13) facing towards and resting at least partially on the first tapered annular end surface (12) of the first pipe element (2). The invention is characterized in that the first flange (3) being fixed on the outer circumference of the first pipe element (2) at least against axial movement towards the open pipe end, the urging means (7, 8, 9) are adapted for urging the sealing (4) and the first flange (3) with such an urging force towards each other, that the connection of the sealing (4) and the first pipe element (1) is gas tight between the conical inner circumferential surface (13) and the tapered annular surface (12) for high pressure gases with a high pressure above 250 bar, and the metal pipe body and the metal sealing body have a rigidity sufficient to withstand this high pressure of the high pressure gas and to withstand an urging force of the urging means (7, 8, 9) sufficient to make the connection gas tight..

Inventors:
KEMPF TORBEN HUGO (DK)
Application Number:
PCT/DK2011/000045
Publication Date:
November 17, 2011
Filing Date:
May 12, 2011
Export Citation:
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Assignee:
MAN DIESEL & TURBO DEUTSCHLAND (DK)
KEMPF TORBEN HUGO (DK)
International Classes:
F16L23/028
Foreign References:
US1821862A1931-09-01
EP0010332A11980-04-30
GB178253A1922-04-20
Attorney, Agent or Firm:
PATENT ATTORNEY LUDWIG J. MUNK & LUDWIG H. MUNK (Augsburg, DE)
Download PDF:
Claims:
CLAIMS

1. Pipe end sealing structure (1 ) comprising a first pipe element (2) having a cylindrical metal pipe body with a first annular end surface (12) at at least one open pipe end adapted to be a sealing support surface, a sealing (4) having a metal sealing body with a first sealing surface (13) facing towards first annular end surface (12) and being adapted to rest at least partially on the first annular end surface (12), a first flange (3) extending radially outwardly from an outer circumference of the first pipe element (2), urging means (7, 8, 9) adapted for urging the sealing (4) and the first flange (3) in an axial direction towards each other, so that the sealing (4) is urged with its first sealing surface (13) against the first annular end surface (12) of the first pipe element (1 ), wherein the first annular end surface (12) of the cylindrical metal pipe body is a tapered annular surface (12) and the first sealing surface (13) of the metal sealing body is a conical inner circumferential surface (13) facing towards and resting at least partially on the first tapered annular end surface (12) of the first pipe element (2), characterized in that the first flange (3) being fixed on the outer circumference of the first pipe element (2) at least against axial movement towards the open pipe end, the urging means (7, 8, 9) are adapted for urging the sealing (4) and the first flange (3) with such an urging force towards each other, that the connection of the sealing (4) and the first pipe element (1 ) is gas tight between the conical inner circumferential surface (13) and the tapered annular surface (12) for high pressure gases with a high pressure above 250 bar, and the metal pipe body and the metal sealing body have a rigidity sufficient to withstand this high pressure of the high pressure gas and to withstand an urging force of the urging means (7, 8, 9) sufficient to make the connection gas tight.

2. Pipe end sealing structure according to claim 1 , characterized in that the sealing incorporates a blind end cap portion which has a rigidity sufficient for a gas pressure above 250 bar in order to make a gas tight closure of the first pipe at one of its pipe ends. 3. Pipe end sealing structure according to claim 1 or 2, characterized in that the sealing incorporates connecting means for connecting a secondary equipment piece with the pipe, e.g. a pressure gauge, temperatur gauge, support connection, etc.

4. Pipe end sealing structure (1 ) according to claims 1 or 3, characterized in that it comprises a second pipe element (5) having a cylindrical metal pipe body with a second annular end surface (13) at at least one open pipe end being a tapered annular sealing support surface (13), and a second flange (6) extending radially outwardly from an outer circumference of the second pipe element (5) and being fixed there at least against axial movement towards the second tapered annular end surface (14) of the second pipe element (5), wherein the sealing (4) has a second sealing surface (15) being a conical inner circumferential surface facing and being adapted to rest at least partially on the second annular end surface (14) of the second pipe element (5), and wherein the cylindrical metal pipe body of the second pipe element (5) and the metal sealing body of the sealing (4) have a rigidity sufficient to withstand a high pressure above 250 bar of a high pressure gas and to withstand an urging force of the urging means (7, 8, 9) sufficient to make the connection gas tight, and wherein the urging means (7, 8, 9) are adapted for urging the sealing (4) and the second flange (6) in an axial direction towards each other, so that the sealing (4) is urged with its second sealing surface (15) against the second annular end surface (14) of the second pipe element (5) with such an urging force, that the connection of the sealing (4) and the second pipe element (5) is gas tight between the second annular end surface (13) and the second sealing surface (15) for high pressure gases with a high pressure above 250 bar.

5. Pipe end sealing structure (1) according to claim 4, characterized in that the sealing is formed as a straight pipe connector piece having a metal sealing body with the same axis for the conicity of the first sealing surface (13) and the second sealing surface (15), such that the first pipe element (2) and the second pipe element (5) are straightly connected.

6. Pipe end sealing structure (1) according to claim 4, characterized in that the sealing is formed as a L-shaped or curved pipe connector piece having a metal sealing body with the axis for the conicity of the first sealing surface different from the axis for the conicity of the second sealing surface, such that the first pipe element and the second pipe element are not straightly connected, e.g. in the form of an L or a curve.

7. Pipe end sealing structure according to one of claims 4, 5 or 6, characterized in that it comprises at least one further pipe element having a cylindrical metal pipe body with a further annular end surface at at least one open pipe end being a tapered annular sealing support surface, and a further flange extending radially outwardly from an outer circumference of the further pipe element and being fixed there at least against axial movement towards the further tapered annular end surface of the further pipe element, wherein the sealing has at least one further sealing surface being a conical inner circumferential surface facing and being adapted to rest at least partially on the further annular end surface of the corresponding further pipe element, and wherein the cylindrical metal pipe body of the further pipe element and the metal sealing body of the sealing have a rigidity sufficient to withstand a high pressure above 250 bar of a high pressure gas and to withstand an urging force of the urging means sufficient to make the connection gas tight, and wherein the urging means are adapted for urging the sealing and the further flange in an axial direction towards each other, so that the sealing is urged with its further sealing surface against the further annular end surface of the further pipe element with such an urging force, that the connection of the sealing and the further pipe element is gas tight between the further annular end surface and the further sealing surface for high pressure gases with a high pressure above 250 bar.

8. Pipe end sealing structure according to claim 7, characterized in that it comprises one further pipe element and the sealing is formed as a pipe connector piece having a T- or Y-shaped metal sealing body, such that the first pipe element, the second pipe element and the one further pipe element are connected in the form of a T or a Y.

9. Pipe end sealing structure according to claim 7, characterized in that it comprises two further pipe elements and the sealing is formed as a pipe connector piece having an X-shaped metal sealing body, such that the first pipe element, the second pipe element and the two further pipe elements are connected in the form of an X.

10. Pipe end sealing structure according to claim 7, characterized in that it comprises two or more further pipe elements and the sealing is formed as a distribution manifold having a metal sealing body within which the branching of the distributor is formed.

11. Pipe end sealing structure (1 ) according to one of the preceding claims, characterized in that a tapering angle of the first end surface (12) is somewhat bigger than a conical angle of the first sealing surface (13) and/or a tapering angle of the second end surface (14) is somewhat bigger than a concical angle of the second sealing surface (15), so that a linear, annular contact of the first end surface (12) and the first sealing surface (13) on the one hand and/or the second end surface (14) and the second sealing surface (15) on the other hand is established, as the urging means urge the sealing (4) and the first flange (3) in an axial direction towards each other and/or the sealing (4) and the second flange (6) in an axial direction towards each other.

12. Pipe end sealing structure (1) according to claim 11 , characterized in that the difference between the tapering angle of the first end surface (12) and the conical angle of the first sealing surface (13) and/or the difference between the tapering angle of the second end surface (14) and the conical angle of the second sealing surface (15) is 0,25° to 4°, preferably 1° to 4a, e.g. 2°, and wherein the tapering angle of the first end surface (12) and/or the second end surface (14) is preferably 60° and the conical angle of the first sealing surface (13) and/or the second sealing surface (15) is preferably 58°. 13. Pipe end sealing structure (1 ) according to one of the preceding claims, characterized in that the metal sealing body comprises an outer portion protruding radially over the outer circumferential surface of the first pipe element (2) and/or the outer circumferential surface of the second pipe element (5) and/or the outer circumferential surface of each of the further pipe elements. 14. Pipe end sealing structure (1) according to claim 13, characterized in that the urging means (7, 8, 9) comprise threadedly engaged nuts and first bolts (7) penetrating through holes in the first flange (3) and through holes (8) in the outer portion of the metal sealing body and/or the urging means comprise first bolts penetrating through holes in the first flange and being threadedly engaged within holes in the outer portion of the metal sealing body and/or the urging means comprise first bolts penetrating through holes in the outer portion of the metal sealing body and being threadedly engaged within holes in the first flange.

15. Pipe end sealing structure (1 ) according to claim 13 or 14, characterized in that the urging means (7, 8, 9) comprise threadedly engaged nuts and second bolts (9) penetrating through holes in the second flange (6) and through holes (8) in the outer portion of the metal sealing body and/or the urging means comprise second bolts penetrating through holes in the second flange and being threadedly engaged within holes in the outer portion of the metal sealing body and/or the urging means comprise second bolts penetrating through holes in the outer portion of the metal sealing body and being threadedly engaged within holes in the second flange.

16. Pipe end sealing structure according to claim 13, characterized in that the metal sealing body is formed with the same axis for the conicity of the first sealing surface and the second sealing surface, wherein the urging means comprise first bolts penetrating through holes in the first flange, through holes in the second flange, and preferably through holes in the metal sealing body, which are urged by nuts on both ends, or the urging means comprise first bolts penetrating through holes in the first flange and preferably through holes in the metal sealing body and being threadedly engaged with holes in the second flange, or the urging means comprise first bolts penetrating through holes in the second flange and preferably through holes in the metal sealing body and being threadedly engaged with holes in the first flange. 17. Pipe end sealing structure (1 ) according to one of the preceding claims, characterized in that the first flange (3) and the first pipe element (2) are separate parts and/or the second flange (6) and the second pipe element (5) are separate parts and/or the further flange and the further pipe element are separate parts. 18. Pipe end sealing structure (1) according to claim 17, characterized in that a shear ring (11 ) is drawn over the outer circumference of the first pipe element (2) and/or a shear ring (11 ) is drawn over the outer circumference of the second pipe element (5) and/or a shear ring is drawn over the outer circumference of the further pipe element, wherein the shear ring is hindered on axial movement towards the sealing (4) by a circumferential shoulder on the outer circumference and wherein the shear ring (11 ) is overlapping the shoulder in radial direction.

19. Pipe end sealing structure (1) according to claim 18, characterized in that the first flange (3) and/or the second flange (6) and/or the further flange have a bigger inner diameter than the outer diameter of the respective shoulder and the first flange (3) and/or the second flange (6) and/or the further flange have a smaller inner diameter than the outer diameter of the respective shear ring (11 ), so that a axial movement of the first flange (3) and/or second flange (6) and/or the further flange towards the sealing (4) is hindered.

20. Pipe end sealing structure (1) according to claim 18 or 19, characterized in that the shoulder on the first pipe element (2) and/or the second pipe element (5) and/or the further flange is a portion of a ring groove (16).

Description:
Pipe end sealing structure

The invention is directed to a pipe end sealing structure used at a connection of a high pressure gas pipe element, i.e. a first high pressure gas pipe with a second pipe element, i.e. a second high pressure gas pipe or a blind cap at the end of the high pressure gas pipe.

From the British Patent GB 1 ,148,556, there is known a pipe end sealing structure comprising a first pipe with an open pipe end and a second pipe with an open pipe end facing the open pipe end of the first pipe, wherein the connection of the two pipes at their respective open pipe ends is sealed by a sealing with an annular metal body laid between the two open pipe ends facing each other. In order to connect the two pipes at their open pipe ends and to clamp the sealing between the two open pipe ends, thereby sealing the connection between the two pipes, there are foreseen two loose flanges situated at the outer circumference of each pipe and being hindered in axial movement towards the open pipe end by a shear ring, respectively engaged in a ring groove in the outer circumferential surface of each pipe and protruding radially, thereby engaging an inner shoulder of each loose flange.

British Patent Specification GB 178,253 discloses a similar pipe connection, wherein each pipe end has an end flange and the end flanges being screwed together with abutting radial surfaces by nuts and bolts extending through the end flanges, thereby sealing the crevice between the abutting radial surfaces of the end flanges. Each of the end flanges has an inner conical surface and each of the pipe ends has an annular outer tapered surface. The end flanges are drawn on the pipe ends by further bolts extending through further flanges fixedly mounted to the pipe ends similar to the loose flanges described in the above mentioned British Patent GB 1 ,148,556.

While these sealing structures have been in use for hydraulic pipes with sufficient tightness, further efforts were made to avoid leakages at the sealing. ln a further effort to improve this known sealing structure, a sealing structure known under the name„GS-Hydro" has been developed, wherein the sealing comprises an inner elastomer ring backed by a surrounding outer steel ring, thus sealing against overpressure from inside the tubes. The urging of the two pipe ends towards each other by the two loose flanges held by a circular snap shear ring being approximately half-thicknesswise embedded in a groove in the other circumferential surface of the pipe has been adopted. However such sealing design has not shown to be satisfactory for use in high- pressure gas installations, i.e. for high pressure injection gas installations for large two-stroke engines powered by natural gas, wherein the fuel gas has pressures above 250 bar, mostly above 300 bar and in many cases up to 450 bar. In this environment leakages cannot be avoided with the known pipe end sealing structures. Another sealing structure employing an elastical O-Ring is known from WO 2008/008289 A2.

Further, US Patent US 1 ,821 ,862 and French Patent FR 723.062 disclose a sealing structure, wherein the axial end surfaces of two pipe ends abut each other in the sealed position, pressed against each other by nuts and bolts screwed through flanges protruding radially from the pipes' other circumferential diameter in the vicinity of the pipe ends. The pipe ends have tapered annular surfaces. A further resilient sealing ring is drawn over the tapered surfaces of the pipe ends. To this end, the resilient sealing ring has conical inner circumferential surfaces resting on the tapered annular end surfaces of the pipes. The abutment of the axial end surfaces prevents an overexpansion of the resilient sealing ring. In another embodiment, a further ring element is placed radially around the resilient sealing ring in order to restrict the yielding movement of the resilient sealing ring. In still another embodiment, the resilient sealing ring is placed in a pocket of one of the pipe ends, such that a radial inner surface of the pocket restricts yielding movement of the resilient sealing ring. It is therefore an object of the invention to find a pipe end sealing structure with an improved tightness if employed for the coupling of high pressure gas pipe or pipe system elements with each other. This object is achieved by the features of present claim 1.

According to the invention, there is foreseen a first pipe element with at least one open pipe end, wherein the first pipe element has a cylindrical metal pipe body with a rigidity (and wall thickness) sufficient for high pressure gas with a gas pressure above 250 bar, preferably above 300 bar, wherein a first annular end surface at the open pipe end to be sealed is tapered. Moreover, there is foreseen a sealing with a metal sealing body with a rigidity (and wall thickness) sufficient to withstand a gas pressure above 250 bar, preferably above 300 bar having a first sealing surface in the form of an inner cone facing towards this tapered end surface at the open pipe end and at least partially covering this end surface. That is, the sealing has a first conical inner circumferential sealing surface facing towards and covering at least partially the first tapered annular end surface of the first pipe part at the open pipe end, thereby making the connection between the sealing and the first pipe element gas tight even if a gas pressure inside the pipe is above 250 bar, preferably even if the gas pressure inside the first pipe part is above 300 bar. In order to urge the first pipe element and the sealing in place, there are urging means adapted for urging the sealing and the first flange in an axial direction towards each other, so that the sealing is urged with its first sealing surface against the first annular end surface of the first pipe element. The metal pipe body and the metal sealing body have a rigidity sufficient to withstand a high pressure above 250 bar, preferably above 300 bar of a high pressure gas and to withstand an urging force of the urging means sufficient to make the connection gas tight, and the urging means are adapted for urging the sealing and the first flange with such an urging force towards each other, that the connection is gas tight.

It is clear from the above, that the gas tight connection of the sealing and the first pipe element is between the first tapered annular end surface of the open pipe end and the first conical inner circumferential surface covering the first tapered end surface at the open pipe end. No other additional sealing faces or auxiliary sealings are foreseen. To this end, it is preferable, if the sealing consists of the metal sealing body being in one piece.

In other words, the connection has to be and is tightened against gas leakage of a gas inside the pipe having a high pressure of above 250 bar, preferably 300 bar solely at the mating of the first conical inner surface and the first tapered annular end surface. Therefor, there are urging means adapted for urging the sealing and the first flange with their mating first tapered annular end surface and first conical inner circumferential surface with such an urging force towards each other, that this connection is gas tight. In order to make this connection gas tight, the urging force of the urging means is and has to be applied on the mating of the first conical inner surface and the first tapered annular end surface without a constructional restriction or limitation. Thus, the metal pipe body and the metal sealing body must have a rigidity to not only withstand a high pressure of the gas inside the pipe, but also the applied urging force of the urging means. The rigidity and ductility of metal pairing between the metal body of the sealing and the metal pipe body on the one hand and the surplus of area due to the conical/tapered bearing surfaces with a better load distribution on the other hand makes is possible to clamp or urge the first pipe element via the first flange against the sealing with an high urging force. Moreover, metallic material allows a good finishing of the sealing surface of the sealing and the end surface of the pipe element with very low tolerances. Moreover, the conical shape of the sealing surface leads to a„self-finding" during the mounting of the sealing on the open pipe end. Moreover, due to the ductility of metal parts or steel parts, if the pipe element and the sealing both are made of metal, preferably steel, the urging means can clamp the sealing on the pipe part with a force high enough to make the connection gas tight by elastically deformation in the vicinity of the pairing compensating little failures in evenness of the sealing surface and/or the tapered end surface and high enough, to avoid overpressure from inside the pipe finds its way through the pairing. The metal sealing body can deform elastically in the vicinity of the inner conical sealing surface, whereas on the other hand, the metal sealing body as a whole can be made with a high rigidity, so that it withstands the high pressure of the gas, to which it is excelled. To this end, the metal sealing body is preferably made in one piece.

This makes the invention useful for being employed in high pressure gas environments, e.g. in fuel injection systems for large two-stroke engines, wherein the fuel gas, namely natural gas has to be compressed above a pressure level of 250 bar, in most cases above 300 bar, where often peak pressure values of 450 bar are happening (but pressures higher than 700 bar will normally not occur). It is understood that often a security margin might to be fulfilled for a pipe end sealing structure, for gas pipes normally a 50 % security margin. E.g., a pipe end sealing structure according to the invention with a rigidity of the metal pipe body and the metal sealing body sufficient to withstand a high test pressure of above 250 bar and the urging force of the urging means sufficient to make the connection gas tight at this high test pressure level, might be used for above 170 bar actual working pressure (as 1.5x170 = 255 bar), preferably above 200 bar actual working pressure in the gas pipe to be sealed. The invention might also be useful for gas pipes with a lower actual working pressure of e.g. 50 bar / test perssure of e.g. 75 bar. In this connection, it should be noted that the natural gas used as a fuel here can be any mixture of gaseous and liquid natural gas. The mixture might also be be a liquid gas still having some compressibility or fully evaporated gas thus being gaseous.

By the improved gas tightness achieved by the invention, security issues can be avoided or at least minimized which arise from the employment of high pressure gas piping in an environment, where human personnel is around, i.e. in the machinery room of ships driven by large two-stroke engines, which in turn are driven by a natural gas, so that secondary security measures can be avoided or made less costly. This makes it on the other hand possible to use high pressure natural gas on ships with good cost effectiveness, particularly on LNG (Liquid Natural Gas) tankers, where it is necessary to get rid of a part of the LNG cargo during the travel in order to avoid excess pressure, which can then be used to drive the ship engine instead of being blown into the environment.

In one further development of the invention, the tapering angle of the first end surface at the open end of the first pipe element might be somewhat bigger or somewhat smaller than the corresponding conical angle of the first sealing surface at the sealing facing the first end surface, preferably 1 ° - 2° smaller or bigger. Thereby, a linear contact of the first end surface and the first sealing surface, annularly around the open pipe end, can be achieved, as rotational symmetry of the respectively tapered and conical interfering face parts is foreseen. Due to the linear contact, a high force can be applied on the annular contact between the first end surface and the first sealing surface, so that an elastic or even a plastic deformation of the sealing and/or pipe body at the first annular end surface can be achieved in order to tighten the connection additionally and in order to balance tolerances in the surface quality.

Said tapering angle, in an axial plane of the tube end taper axis, being measured at the tube tip, from a plane being normal to said axis and facing the tube end, to one of the two oblique lines of the taper's intersection with said axial plane, the measuring path not intersecting any material and the measured value being positive and less than 90 °. Said conical angle, in an axial plane of the axis for the conicity of the first sealing surface, being measured, from a plane being normal to said axis and facing the first sealing surface, to one of the two oblique lines of the conicity's intersection with said axial plane, the measuring path not intersecting any material and the measured value being positive and less than 90 °.

It is preferred that the tapering angle is slightly bigger than the corresponding conical angle, i.e. the tapered annular end surface at the pipe end is a bit more pointed than the receiving conical inner circumferential surface, so that the first contact of both is at the small diameter of the tapered annular end surface at the pipe end. The tube end tapering angle and the sealing surface cone angle preferably are in the 60° ± 10° interval, the cone angle of the inner conical sealing surface always being a bit smaller, preferably 1 - 2° smaller. A good value for the tapering angle might be 60°, for the cone angle of the inner conical sealing surface 58°.

While the invention is useful i.e. for gas tight mounting of a blind end cap incorporated in the sealing (preferably being in one piece with the metal sealing body) onto the open pipe end of a pipe or a pipe element, in one preferred further development of the invention, the pipe end sealing structure comprises a second pipe element to be connected over the sealing to the first pipe element. To this end, the second pipe element has a cylindrical metal pipe body with a second annular end surface at at least one open pipe end, which is tapered annularly and adopted to serve as a sealing support surface. Further, the sealing of the pipe end sealing structure has a second sealing surface being a conical inner circumferential surface facing the second tapered annular surface and therefore facing in the opposite axial direction of the first sealing surface. The second sealing surface is adapted to rest at least partially on the second tapered annular surface of the second pipe element. The cylindrical metal pipe body of the second pipe element and the metal sealing body of the sealing have a rigidity sufficient to withstand a high pressure of same pressure level/range as selected for the sealing structure for the corresponding first pipe element and to withstand an urging force of the urging means, whereby the urging force is sufficient to make the connection gas tight. The urging means are adapted for urging the sealing and a second flange in an axial direction towards each other, so that the sealing is urged with its second sealing surface against the second annular end surface of the second pipe element with such an urging force, that the connection is gas tight. Thus, the connection between the only one metal sealing body and the second pipe element corresponds to the connection between the only one metal sealing body and the first pipe element.

The first and the second pipe element might be standard pipes or tubes to be connected gas tightly. However, it is also possible that at least the second pipe element is a connector piece, e.g. in a T-shape or X-shape, at least one open pipe end of which is connected by the pipe end sealing structure of the invention to an open pipe end of the first pipe element. The first and/or the second pipe element might also have an L-shape or another bended or manifolded body shape.

Moreover, the number and the positions of sealing pairings can be varied freely. E.g., the sealing, and therewith the metal sealing body might be formed as a straight connector piece for the first pipe element and the second pipe element. However, the invention is not limited to that. The sealing might also be formed as a curved or L-shaped connector piece.

Moreover, the pipe end sealing structure might comprise at least a further pipe element having a cylindrical metal pipe body with a further annular end surface at at least one open pipe end being a tapered annular sealing support surface, the further pipe element having a further flange extending radially outwardly from an outer circumference of the further pipe element and being fixed there at least against axial movement towards the further tapered annular end surface of the further pipe element, wherein the sealing has at least one further sealing surface being a conical inner circumferential surface facing and being adapted to rest at least partially on the further annular end surface of the corresponding further pipe element.

In order to establish a pipe crossing (wherein the sealing might be formed as an X- shaped connector piece and two further pipe elements with two corresponding further sealing surfaces on the metal sealing body can be foreseen) or a distribution manifold (wherein the sealing might be formed as an Y-shaped connector piece or as a connector piece with more than two outlets and one or more further pipe element with one or more corresponding further sealing surface on the metal sealing body can be foreseen), the cylindrical metal pipe body of each of the further pipe elements and the metal sealing body of the sealing have a rigidity sufficient to withstand a high pressure above 250 bar of a high pressure gas and to withstand an urging force of the urging means sufficient to make the connection gas tight, and wherein the urging means are adapted for urging the sealing and each of the further flanges in an axial direction towards each other, so that the sealing is urged with each of its further sealing surface against the corresponding further annular end surface of the corresponding further pipe element with such an urging force, that the connection of the sealing and each of the further pipe elements is gas tight between the further annular end surface and the further sealing surface for high pressure gases with a high pressure above 250 bar.

On the other hand, the sealing might also be formed as a connector piece for non- interferring pipe crossings, wherein the secondary pipe formed by the the further pipe elements connected by the sealing might or might not be adapted for conducting a high pressure gases with a high pressure above 250 bar.

Moreover, it is understood, that the pipe end sealing structure of the invention is useable to connect to pipe elements having the same diameter or also identical pipe elements. In this case, the tapered end surfaces on the first pipe element and on the second pipe element might have - in the case that the sealing is formed as a straight connector piece - the same radial coordinates, and also the first inner conical sealing surface and the second inner conical sealing surface have the same radial coordinates. It is preferable, when the first inner conical sealing surface is spaced apart from the second inner conical sealing surface by full metal material of the sealing metal body, so that the sealing has a high rigidity even at the innermost point.

It is, however, also possible to connect pipes with different inner diameters by the pipe end sealing structure of the invention, wherein the sealing has to be adapted so that the first inner conical sealing surface has different radial coordinates than the second inner conical sealing surface in order to meet the different radial coordinates of the first tapered end surface at the first pipe element and the second tapered end surface on the second pipe element. Thereby, the invention can be used for a diameter augmentation or reduction of a gas line. If the first pipe element and the second pipe element have different tube diameters, and therefore also the diameters of the sealing are different on the side facing the first pipe element and on the side facing the second pipe element, also the urging force needed for tighten the connection of the the first pipe element with the sealing and the connection of the second pipe element with the sealing might be different. Therefore, the urging means could comprise first urging means for urging the for urging the sealing and the first flange towards each other and second urging means for urging the sealing and the second flange towards each other, which are adapted for different urging forces and are therefore different.

The first flange can be soldered or welded to the first pipe element, the second flange respectively to the second pipe element and/or any further flange to a corresponding further pipe element. However, it is preferable to have loose flanges, which can be fixed or mounted at the respective pipe element subsequently. If the flanges and the pipe elements are separate parts, a shear ring can be drawn over the outer circumferential surface of the respective pipe element, wherein a shoulder protruding radially from the outer circumference or outer circumferential surface can form a stop for this shear ring, thereby hindering the shear ring in axial movement towards the sealing. If the shear ring is protruding over the shoulder in a radial direction, the flanges can have an inner diameter which allows them to be pulled over the respective pipe end and the shoulder there and the shear ring forms a stop to hinder the flanges in an axial movement towards the sealing, respectively.

The shoulder can be formed in a ring groove, wherein the shear ring is received. It is also thinkable, that the shoulder is formed at an edge of a collar welded to an open pipe end, on which the tapered end surface is provided. A shear ring suitable for the invention might be formed from a spring able to have its diameter extended and biased by spring force into the desired diameter of the ring groove or the outer circumferential surface behind the shoulder. The urging means can comprise clamping bolts penetrating the first flange and also the second flange, having a bolt head on one end and a nut on the other end, respectively, to clamp together the first flange and the second flange and thereby the sealing to the first pipe element and also to the second pipe element. Also clamping bolts with nuts on both ends might be used. If the sealing is formed as a straight pipe coupling of the first pipe element and the second pipe element, the bolts or screws or treaded rods might extend from flange to flange via through- holes in the metal sealing body or might surround the metal sealing body. In an alternative further development, the first flange is bolted to the sealing metal body, which therefore has an outer portion protruding radially over the outer circumferential surface of the first pipe element. If there is a second or further pipe element, the second or further flange might be bolted to the sealing in the same manner. It is understood that the metal sealing body should have a radial dimension equal to or even larger than the first flange and/or the second flange or least large enough to receive the bolts. Such direct mutual urging between a flange and the facing side of a sealing body is especially useful when respective first and second flanges from more coaxially connected tubes possibly of different diameter have different hole patterns not allowing direct mutual clamping of the flanges. It is also especially useful when the axes of the connected pipe elements are not coaxial (e.g. at T-connections, L- connections or Y-connections, where the sealing body is formed as an T-piece, L-piece or Y-piece), or when a sealing body is used as a blocking end closure for a single tube. Further, various combinations of hole pattens in the flanges and the sealing might be used. For example, If there is a second or further pipe element in line with the first pipe element, the fist and second flange might be similar or identical and displaced in angle position, e.g. 90° displaced, and the metal sealing body might have a ring pattern, star pattern or polygon pattern of holes, into which the first and second bolts are bolted, e.g. in an order alternating after each or after each second bolt. Moreover, in general, there might be similar or identical flanges. The flanges might have solely through-holes, solely threaded holes or both threaded and through-holes. The ladder might be used in the case of aligned first and second pipe elements, which are clamped to the sealing straightly by bolts penetrating the first flange and also the second flange, so that some bolts can be inserted from the first flange and screwed into the second flange, whereas some other bolts can be inserted from the second flange and screwed into the first flange.

Moreover, at least in the case of aligned first and second pipe elements, which are connected to the sealing straightly, there might be foreseen auxiliary screws for provisorially holding the one connection in position (without tensioning to functional state) while the other connection(s) is/are being (dis-)assembled.

According to another aspect of the invention, the sealing might have another port for other combination to a gas system component. The port might be a pipe element or at least a tubular connector piece. The port might be adapted to be mounted to an end of another tube component. The port might be adapted to be mounted to an end of a flexible ducting means, e.g. a flex hose. The port might be shaped as an adapter for another device. The port might be adapted to be connected to an end of another tube component by a permanent connection like e.g. welding or soldering. The port might be in one piece with the metal sealing body. Otherwise, the port might be in a separate piece, having a tapered annular surface and a flange to mbe mounted at an innerconical surface of the sealing in the same manner as the first pipe element. In the ladder case, the separate piece might be shaped as a plug, blocking a seal opening when inventively mounted, as an alternative to the further development of claim two.

Further advantages and principles of the invention will be discussed together with a preferred embodiment of the invention, which is shown in the attached drawings. It has to be understood, that a difference between the tapering angle and the conical angle of the sealing surface is also advantageous at the second pairing between the second end surface and the second sealing surface. Fig. 1 shows a perspective view of a pipe end sealing structure according to a preferred embodiment of the invention connecting two pipes and sealing this connection gas tight.

Fig. 2 shows a cross-sectional view of an open pipe end of a first pipe comprised in the pipe end sealing structure of Fig. 1.

Fig. 3 shows a cross-sectional view of a sealing comprised in the pipe end sealing structure of Fig. 1.

Fig. 4 shows a cross-sectional view of an open pipe end of a second pipe comprised in a pipe end sealing structure of Fig.1. Fig. 5 shows a cross-sectional partial view of the pipe end sealing structure of Fig. 1 and

Fig. 6 shows a side-view of the sealing used in the pipe end sealing structure of Fig. 1 and 5.

Reference is made now to Fig. 1. Figure 1 shows a first pipe 2 and a second pipe 5 being connected over a sealing 4 and thereby form a pipe end sealing structure generally designated by reference sign 1. Between the two open pipe ends of the pipes 2, 5 is arranged the sealing 4, wherein a first flange 3 is fixed on an outer circumference or outer circumferential surface of first pipe 2 and a second flange 6 is fixed on an outer circumference of the second pipe 5. The first flange 3 and the second flange 6 are bolted to an outer portion of the sealing body 4 surrounding radially a conical inner circumferential surface 13 to be explained later on and protruding over the outer circumference of first pipe 2 and second pipe 5, which here both have the same inner diameter and outer diameter. The first pipe 2 and the second pipe 5 consist of metal, preferably steel and also the sealing 4 consists of metal, preferably steel, i.e. the sealing 4 consists of a metal sealing body, the first pipe 2 has a cylindrical metal pipe body and the second pipe 5 has also a cylindrical metal pipe body. The pipes, 2, 5 have a wall thickness sufficient to withstand a pressure difference of 250 bar, preferably 300 bar, or for some situations of use even 500 bar, and also the metal sealing body has a respective thickness.

The pipe end sealing structure of Figure 1 is especially adapted for gas tight sealing of the connection between the first pipe 2 and the second pipe 5, so that the pipe end sealing structure 1 is useful in high pressure gas piping systems, i.e. fuel injection systems of large two-stroke engines and the like.

The features of the main parts of the pipe end sealing structure shown in Fig. 1 , which make it useful for a gas tight connection of pipes in a high-pressure gas piping environment can be seen especially in Fig. 2 to 4.

Fig. 2 shows a partial view of the first pipe 2 at the open pipe end. At the axial end of pipe 2 (at the open pipe end), there is a first tapered end surface 12 having a tapering angle of approximately 60°. Further there is a groove 16 at a distance corresponding to first flange 3 forming a seat for a shear ring 1 1 (Fig. 5) as an axial stop for first flange 3.

The sealing 4 shown in Fig. 3 has a metal sealing body with the first inner conical sealing surface 13 mentioned above facing towards the first tapered end surface 12 at the first pipe 2 and a second inner conical sealing surface 15 facing in an axial opposite direction as first inner conical sealing surface 13. There is a distance between the first sealing surface 13 and the second sealing surface 15, where the metal body of sealing 4 can have a same inner diameter as the inner pipe diameter of first pipe 2 and second pipe 5. The metal sealing body of sealing 4 protrudes with an outer portion radially beyond the outer circumference of the first pipe 2 and the second pipe 5 and, as can be seen especially in Figs. 3 and 6, a ring of through holes 8 extending axially and in a concentric fashion around the central gas aperture of the sealing 4 and is of full material apart from that. The through holes 8 have threads to let the first and second flange 3, 6, here being opposed, be bolted to the metal sealing body. The second pipe 5 has at its open pipe end to be sealed by sealing 4 a structure fully comparable to the corresponding end of the first pipe 2 at its open pipe end to be sealed, with a tapered end surface 14 suitable for second sealing surface 15 of sealing 4 and a groove 16 to receive a shear ring 11 (Fig. 5) to form an axial stop for second flange 6.

As can be seen in Fig. 5,, taken together with Figs. 2 to 4, the open pipe ends of first pipe 2 and second pipe 5 are received in the central aperture of sealing 4, with the first tapered end surface 12 being pressed against first sealing surface 13 and second tapered end surface 14 being pressed against second sealing surface 15. The tapering angle of the first tapered end surface 12 and second tapered end surface 14 is 60°, while the conical angle of first sealing surface 13 and second sealing surface 15 is a few degrees less, i.e. 58°, so that a linear contact between first tapered end surface 12 and first sealing surface 13 on the one hand and second tapered end surface 14 and second sealing surface 15 on the other hand is established, as first bolts 7 and second bolts 9 are screwed into the threaded holes 8 in the sealing 4 and thereby urging over first flange 3 shear ring 11 and groove 16 the first tapered end surface 12 against the first sealing surface and over second flange 6, shear ring 11 and groove 16 the second tapered end surface against second sealing surface 15.

As can be seen in connection of Figures 1 and 5, the first flange 3 is displaced at 90° against the second flange 6, so that first bolts 7 can be received in four of the threaded holes 8 in the sealing 4, which are the upper most and lower most threaded holes 8, and the second bolts 9 can be received in four of the threaded holes 8, which are at the most transverse position at sealing 4. Various modifications may be made without leaving the scope of the invention.

E.g., there might be a different bolting pattern, than the shown bolting pattern with eight holes in the sealing, where two holes following each other are dedicated to one of the first and second flange and then the next two holes following each other are dedicated to the other of the first and second flange. The first and the second pipe elements might have different tube diameters with respectively selected urging forces of the urging means.

There might be other shapes and functions of the sealing taken as the member between tube ends.

In general, it is preferred, as in the shown embodiment, that there is only the metal sealing body, the first pipe element and, if the sealing is not formed as a blocking end closure, a second pipe element and, in the case of more branching pipe lines, further pipe elements, forming the pipe connection sealed by the inventive pipe end sealing structure. However, in cases, where a pipe element with an "undersize" or "oversize" outer diameter should be connected to the sealing, there might be a separate pipe end adapter piece to use when connecting the pipe to the sealing, still using the pipe's flange as an outset for the urging means. To this end, one may make stacked use of the conicity principle for mounting of a too- small diameter tube in a seal body: The intermediate adapter piece might have for the respective tube end an adapting inner conical surface comparable to the corresponding inner conical surface of the metal sealing body, but of a smaller diameter, and around this coned hole a coned tip adapted for the receiving inner conical surface of the (else oversize) metal sealing body. Moreover, there might be two seals directly used also as opposed flanges mutually clamping and sealing the two tapered ends of a very short tube, thus being able to establish some angled and little off-set positioning of other tubes also connected to respective seal body.

For e.g. repair, inspection or circuit modification purpose, the inventive sealing can be assembled/disassembled several times without losing it's functionality by preserving a pressure resistance to leak, as high as 1500 bar. Taking into account the 50% pressure security margin dealt with in such gas installations, the inventive sealing structure therefore has demonstrated potential for use in gas systems designed with a working pressure up to even 1000 bars.

0921

Reference Signs

Pipe end sealing structure (1 )

first pipe element (2)

first flange (3)

sealing (4)

second pipe element (5)

second flange (6)

urging means (7, 8, 9)

first bolts (7)

through holes (8)

second bolts (9)

shear rings (11 )

first tapered annular sealing support end surface (12)

first conical inner circumferential sealing surface (13)

second tapered annular sealing support end surface (14)

second conical inner circumferential sealing surface (15)

ring grooves (16)