Metal seal, flat face coupling arrangement, fuel system and vehicle

Abstract

A metal seal (1) and a flat face coupling arrangement (20) comprising said metal seal (1). The metal seal (1) comprises an annular seal body portion (2), coaxial with a central axis (A) of the metal seal (1). The annular seal body portion (2) comprises a radially inner circumferential edge (3), a first annular surface (5), and a second annular surface (6). A first retainer flange (7) extends from the radially inner circumferential edge (3) at a first obtuse angle (α) relative to the second annular surface (6), and a second retainer flange (8) extends from the radially inner circumferential edge (3) at a second obtuse angle (β) relative to the second annular surface (6). The metal seal (1) further comprises a first stiffening lip (9) and a second stiffening lip (9), each extending from the radially inner circumferential edge (3) of the annular seal body portion (2) at a third obtuse angle (γ) relative to the second annular surface (6). A fuel system (50) and a vehicle (100) are also described.

Description

[0001] METAL SEAL, FLAT FACE COUPLING ARRANGEMENT, FUEL SYSTEM AND VEHICLE

[0002] TECHNICAL FIELD

[0003] The present disclosure relates in general to a metal seal for a flat face coupling arrangement as well as a flat face coupling arrangement comprising said metal seal. The present disclosure further relates in general to a fuel system configured for storage and / or transportation of hydrogen-containing fuels. Moreover, the present disclosure further relates in general to a vehicle comprising such a fuel system.

[0004] BACKGROUND

[0005] There are several environmental benefits of running a vehicle on methane or methane-based fuels compared to running on diesel fuel, including for example lower CO2 emissions per unit of energy. Methane is at ambient conditions a gas with low density. Thus, in order to carry a sufficient amount of fuel, the fuel may typically be stored onboard the vehicle in either compressed state, as compressed natural gas (CNG), or in liquified state, as liquified natural gas (LNG).

[0006] One of the major challenges with gaseous fuels is to ensure that the fuel is not leaked from the fuel system to the surroundings and thereby lost. Fuel systems for vehicles typically comprises numerous fittings for connecting hoses and pipes, each one serving as a potential point for gas leakage.

[0007] One type of fitting which is commonly used in, for example, CNG fuel systems and LNG fuel systems is a so called double ferrule fitting. These fittings comprises a nut configured to tighten the entire fitting assembly onto a tube, a front ferrule that grips the tube and provide the initial seal, a back ferrule that enhances the grip and ensures a more robust seal by distributing the force evenly along the tube, and a body that contains the connection and onto which the nut is threaded. While double ferrule fittings are designed to provide a reliable and leak-proof connection, improper installation can compromise their performance. For example, over-tightening the fitting can deform the ferrules or the tube, causing the connection to lose its sealing capability. Moreover, under-tightening may lead to the ferrules not properly gripping the tube.

[0008] An alternative to double ferrule fittings could be so called O-ring front facing seals (commonly abbreviated ORFS). These offer a standardized and robust way of assembling fittings with torque, and offer best in class sealing performance. ORFS comprises a nut and a sleeve that are initially slid over an unshaped pipe end. The pipe is thereafter assembled into a machine which flares the pipe end, thereby achieving a flat annular surface configured to face and abut a body comprising a flat end surface. The fitting further comprises an elastomeric O-ring arranged in a captive O-ring groove of the flat end surface of the body, said O-ring configured to ensure a gas-tight fit of the abutting surfaces. The flared pipe is installed by pushing it against the body and assembly the but with a prescribed torque.

[0009] However, elastomeric O-rings can only successfully be used within a certain temperature range (typically from about -50 °C to about 220 °C, depending on the composition). In other words, such O- rings can neither be used at very high nor low temperatures and are therefore not an option for e.g., LNG fuel systems.

[0010] It has previously been proposed to replace the elastomeric O-ring in ORFS with a metal seal to thereby allow using such fittings at temperatures outside of the suitable temperature range of elastomeric O-rings. Such a metal seal comprises an annular seal body, typically having a thickness of about 0.3 mm, configured to be interposed between the flat annular surfaces of the flared pipe and body, respectively. To ensure a gas-tight seal, the thin metal seal may be provided with a thin surface coating of a suitable metal, usually silver, configured to plastically deform and thereby float into and fill any micro-irregularities in the flat surfaces as the flat face coupling is tightened. Thereby, leakage paths caused by possible surface irregularities may be avoided.

[0011] Although such metal seals offers a good solution for reducing the risk for gas leakage in fuel systems where a flat face coupling may be subjected to temperatures outside of the possible temperature range for elastomeric O-rings, there are still obstacles to overcome. For example, to allow easy installation and replacement of a metal seals, it needs to be able to be retained in relation to the body in some way to ensure that it is placed correctly during tightening of the flat face coupling. Moreover, small thickness of the metal seals may lead to a distortion of metal seal prior to and during installation, which in turn may result that a gas-tight seal may still not be achieved. Furthermore, the likelihood of leakage paths between the sealing surfaces being effectively interrupted by the plastic deformation of the thin surface coating on the metal seal, as described above, increases with increasing area of the sealing surface as long as the metal seal is correctly positioned. However, there is a direct correlation between sealing surface area (and thus also the sealing surface of the metal seal) and assembly torque. If the sealing surface is too large, then a high installation torque is needed. Furthermore, increasing the size of the metal seal may also lead to larger fittings, which may in itself present a problem in some fuel systems.

[0012] SUMMARY

[0013] The object of the present invention is to provide an improved metal seal for a flat face coupling arrangement that allows for easy and reliable installation (and replacement) to thereby reduce the risk for leakage of gas between sealing surfaces during use of the flat face coupling arrangement.

[0014] The object is achieved by the subject-matter of the appended independent claim(s).

[0015] In accordance with the present disclosure, a metal seal for a flat face coupling arrangement is provided. The metal seal has a central axis and comprises an annular seal body portion coaxial with the central axis. The annual seal body portion comprises a radially inner circumferential edge, a first annular surface, and a second annular surface. The first and second annular surfaces are configured to extend in parallel and perpendicular to the central axis when the metal seal is used in a flat face coupling arrangement. The metal seal further comprises a first retainer flange extending from the radially inner circumferential edge at a first obtuse angle relative to the second annular surface. The metal seal also comprises a second retainer flange extending from the radially inner circumferential edge at a second obtuse angle relative to the second annular surface, said second retainer flange being arranged diametrically opposite to the first retainer flange with respect to the annular seal body portion. Moreover, the metal seal comprises a first stiffening lip and a second stiffening lip, each extending from the radially inner circumferential edge of the annular seal body portion at a third obtuse angle relative to the second annular surface.

[0016] The herein described metal seal allows for an easy and reliable installation of the metal seal in a flat face coupling arrangement, which in turn considerably reduces the risk for potential gas leakages between abutting surfaces of the flat face coupling arrangement when the flat face coupling arrangement is in use in, for example, a fuel system. Furthermore, the metal seal allows for using standardized components in the flat face coupling arrangement. This may in turn, for example, contribute to reduced manufacturing costs for the flat face coupling arrangement.

[0017] More specifically, the fact that the metal seal comprises a first retainer flange and a second retainer flange, arranged diametrically opposite to the first retainer flange, allows for easy and reliable placement of the metal seal relative to a first coupling member of the flat face coupling arrangement during installation. Furthermore, it allows for an easy removal of the metal seal from the first coupling member in case of replacement. Each of the first and second retainer flanges are configured to utilize an annular surface groove (compare with the O-ring groove of the conventional ORFS) of a first coupling member of the flat face coupling arrangement for the purpose of retaining the metal seal relative to said first coupling member. For said purpose, each of the first and second retainer flanges are arranged to extend with an obtuse angle relative to the annular seal body portion of the metal seal. The fact that they each extend from the radially inner circumferential edge of the annular seal body portion at an obtuse angle allows the respective free ends of the retainer flanges to abut against, and thereby engage with, a radially inner circumferential wall of the annular surface groove of the first coupling member or a surface where said circumferential wall meets a bottom wall of said annular surface groove.

[0018] Moreover, the first and second stiffening lips of the metal seal, arranged with an obtuse angle relative to the annular sealing body, significantly increases the stiffness of the metal seal. An increased stiffness of the metal seal in turn reduces the risk for distortion of the metal seal prior to, and during, installation. This contributes to a reduced risk for possible leakage of gas between the sealing surfaces of a flat face coupling arrangement. The fact that the first and second stiffening lips are extending from the radially inner circumferential edge of annular seal body means that they will extend into the annular surface groove of the first coupling member of the flat face coupling arrangement. Therefore, the presence of the stiffening lips do not require any modification of the first coupling member and will also not introduce any new problems when the metal seal is to be installed relative to the first coupling member to be retained in the desired position.

[0019] Furthermore, the relatively simple configuration of the metal seal allows it to be produced from a metal sheet through, for example, a conventional stamping process. In order words, the production costs for the metal seal may be kept relatively low.

[0020] The first obtuse angle, mentioned above, may according to one alternative be greater than the third obtuse angle. Thereby, the stiffness of the metal seal may be further increased. This is because the stiffness and rigidity of the metal seal increases as the third obtuse angle decreases. Still, the first obtuse angle should be selected to ensure that the metal seal may be appropriately retained in the flat face coupling arrangement and can therefore only be varied within a more limited range for a given slant height of the first retainer flange. Additionally, or alternatively, the first obtuse angle may be substantially equal to the second obtuse angle. This may, among other things, facilitate production of the metal seal, which in turn leads improved consistency in the manufacturing process. This in turn reduces the risk for leakage of gas during use of a flat face coupling arrangement during use.

[0021] The third obtuse angle may for example be from 130° to 155°. Preferably, the third obtuse angle may be from 140° to 155°. The stiffness of the metal seal increases with decreasing third obtuse angle.

[0022] However, if the third obtuse angle is too small, the ability to install the metal seal in relation to a first coupling member of the flat face coupling arrangement may be impaired. Furthermore, a too small obtuse angle may lead to problems during manufacturing, which in turn may negatively affect consistency between metal seals produced in the same way and thereby also the ability to prevent gas leakage during use of a flat face coupling arrangement comprising the metal seal.

[0023] Each of the first retainer flange, the second retainer flange, the first stiffening lip, and the second stiffening lip has a slant height as seen from their respective fixed ends, connected to the radially inner circumferential edge, to their respective free ends. The slant height of each of the first stiffening lip and the second stiffening lip may suitably be less than the slant height of the first retainer flange. This further ensures that the metal seal may be easily installed since the first and second stiffening lips will not be in the way when arranging the metal seal in relation to a first coupling member of the flat face coupling arrangement.

[0024] The slant height of the first retainer flange may be equal to or greater than 0.15*r and equal to or less than 0.25*r, where r corresponds to a radius of the radially inner circumferential edge. Among other things, this has the advantage of contributing to the possibility of using a standardized first coupling member in the flat face coupling arrangement while still allowing a good retainability of the metal seal.

[0025] The first retainer flange is connected to the radially inner circumferential edge along a first arc of said circumferential edge. Furthermore, the second retainer flange is connected to the radially inner circumferential edge along a second arc of said circumferential edge. The first arc may suitably be longer than the second arc. This facilitates installation of the metal seal in relation to a first coupling member of a flat face coupling arrangement while still ensuring that the metal seal may be sufficiently retained. The second arc may have an arc length corresponding to a central angle of between 25° and 75° of the radially inner circumferential edge. Preferably, the second arc may have an arc length corresponding to a central angle of between 30° and 70° of the radially inner circumferential edge. This further contributes to the ability to easily install the metal seal since the second retainer flange is not too large, while still ensuring that the second retainer flange is sufficiently large for the metal seal to be sufficiently retained.

[0026] Alternatively or additionally, the first arc may have an arc length corresponding to a central angle of between 80° and 130° of the radially inner circumferential edge. Preferably, the first arc may have an arc length corresponding to a central angle of between 90° and 120°. This further contributes to the ability to sufficiently retain the metal seal. Moreover, the first retainer flange may also contribute to increased stiffness of the metal seal in view of its relatively large size.

[0027] The present disclosure further relates to a flat face coupling arrangement comprising the metal seal described above, and a first coupling member coaxially arranged with the metal seal. The first coupling member comprises an annular flat sealing surface arranged at a first axial end, and an annular surface groove extending axially into the first coupling member from the first axial end. Said annular surface groove comprises an axially extending radially inner circumferential wall. The metal seal is arranged so that its second annular surface engages with the annular flat sealing surface of the first coupling member, and a first free end of the first retainer flange engages the radially inner circumferential wall of the annular surface groove.

[0028] The flat face coupling arrangement provides the same advantages as described above with regard to the herein described metal seal.

[0029] In the flat face coupling arrangement, the metal seal may be arranged so that each of the first stiffening lip and the second stiffening lip of the metal seal extends into the annular surface groove without engaging the radially inner circumferential wall or a bottom wall of the annular surface groove.

[0030] The present disclosure also relates to a fuel system configured for storage of cryogenic and / or compressed hydrogen-containing fuels and / or transportation of such fuels to a fuel consuming device. The fuel system comprises the flat face coupling arrangement described above. The fuel system may for example be a liquified natural gas fuel system, a compressed natural gas fuel system, or a cryo-compressed hydrogen fuel system.

[0031] Moreover, the present disclosure relates to a vehicle comprising the fuel system described above. The vehicle may be a land-based heavy vehicle, such as a truck or a bus, but is not limited thereto.

[0032] BRIEF DESCRIPTION OF DRAWINGS

[0033] Fig. 1 illustrates a top view of a first exemplifying embodiment of the herein described metal seal for a flat face coupling arrangement,

[0034] Fig. 2 illustrates a cross sectional view, taken along line B-B, of the metal seal shown in Figure 1,

[0035] Fig. 3 illustrates a perspective cross sectional view, taken along line C-C, of the metal seal shown in Figure 1,

[0036] Fig. 4 illustrates a cross sectional view of part of a first coupling member of a flat face coupling arrangement in accordance with the present disclosure with a metal seal according to Figure 1 being arranged to be retained in said first coupling member,

[0037] Fig. 5 illustrates a cross sectional view of a flat face coupling arrangement in accordance with one exemplifying embodiment of the present disclosure,

[0038] Fig. 6 illustrates a top view of a second exemplifying embodiment of the herein described metal seal for a flat face coupling arrangement,

[0039] Fig. 7 schematically illustrates an example of a fuel system in accordance with the present disclosure, and

[0040] Fig. 8 schematically illustrates an example of a vehicle comprising a fuel system. DETAILED DESCRIPTION

[0041] The invention will be described in more detail below with reference to exemplifying embodiments and the accompanying drawings. The invention is however not limited to the exemplifying embodiments discussed and / or shown in the drawings, but may be varied within the scope of the appended claims. Furthermore, the drawings shall not be considered drawn to scale as some features may be exaggerated in order to more clearly illustrate the invention or features thereof.

[0042] The present disclosure relates to a metal seal adapted to be used in a flat face coupling arrangement, and a flat face coupling arrangement comprising such a metal seal. It should be noted that although the herein described metal seal for a flat face coupling arrangement has primarily been developed for use in flat face coupling arrangements adapted for use in fuel systems for methane or methane- based fuels, it may also advantageously be used in fuel systems for hydrogen fuel, such as cryocompressed hydrogen fuel systems. The metal seal may also be used in a flat face coupling arrangement adapted for use in other systems than fuel systems, if desired.

[0043] The metal seal according to the present disclosure has a central axis and comprises an annular seal body portion coaxial with the central axis of the metal seal. The annular seal body portion comprises a radially inner circumferential edge, a first annular surface, and a second annular surface. The first and second annular surfaces are configured to extend in parallel, and perpendicular to the central axis, when the metal seal is used in a flat face coupling arrangement. The first annular surface is configured to abut an annular flat surface of a flared tube to create a gas-tight seal therebetween when the metal seal is arranged in a flat face coupling arrangement (and the flat face coupling arrangement has been fully assembled and tightened). The second annular surface is configured to abut an annular flat sealing surface of a first coupling member when the metal seal is arranged in the flat face coupling arrangement. The second annular surface of the metal seal is configured to create a gas-tight seal against the first coupling member when the flat face coupling arrangement has been fully assembled and tightened. In other words, the annular seal body portion of the metal seal is configured to create a seal, between the flat end surfaces of a first coupling member and a flared pipe, preventing gas from leaking between said flat end surfaces.

[0044] The metal seal further comprises a first retainer flange extending from the radially inner circumferential edge of the annular seal body portion of the metal seal. More specifically, the first retainer flange is connected to the radially inner circumferential edge of the annular seal body portion along a first arc of said radially inner circumferential edge. Furthermore, the first retainer flange is arranged to extend with a first obtuse angle relative to the second annular surface of the annular seal body portion. A free end of the first retainer flange, opposite to the end connected to the annular seal body portion, is thus both axially and radially displaced from the radially inner circumferential edge of the annular seal body portion. Said free end of the first retainer flange is configured to abut a surface of an annular surface groove (similar to an O-ring groove of a conventional ORFS) of a first coupling member of the flat face coupling arrangement to thereby contribute to retaining the metal seal in a desired position.

[0045] The metal seal also comprises a second retainer flange extending from the radially inner circumferential edge of the annular seal body portion of the metal seal. The second retainer flange is arranged diametrically opposite to the first retainer flange with respect to the annular seal body portion. Moreover, the second retainer flange is connected to the radially inner circumferential edge of the annular seal body along a second arc of said radially inner circumferential edge. The second retainer flange is arranged to extend with a second obtuse angle relative to the second annular surface of the annular seal body portion of the metal seal. Said second obtuse angle may or may not be substantially equal to the first obtuse angle mentioned above. When two angles are described to be substantially equal to each other in the present disclosure, it is intended to mean that they differ at most 5° from each other. Similarly to the first retainer flange, the second retainer flange comprises a free end configured to abut a surface of an annular surface groove (similar to an O-ring groove of a conventional ORFS) of a first coupling member of the flat face coupling arrangement to thereby contribute to retaining the metal seal in a desired position.

[0046] The metal seal further comprises a first and a second stiffening lip, each extending from the radially inner circumferential edge of the annular seal body portion at a third obtuse angle relative to the second annular surface. These stiffening lips are configured to increase the stiffness of the metal seal and thereby reduce the risk for distortion of the metal seal during installation thereof. Each of the first and second stiffening lips is interposed between the first and second retainer flanges as seen in the circumferential direction along the radially inner circumferential edge of the annular seal body portion. It should here be noted that the metal seal may comprise more than two stiffening lips, if desired, although this is not typically desired.

[0047] The metal seal may suitably be a monolithic body. In other words, the metal seal may be formed from a single metal sheet, for example a stainless steel sheet, without any joints or seams. Such a metal sheet may suitably have a sheet thickness of about 0.2 - 0.4 mm, although the present disclosure is not limited thereto. The metal seal may for example be formed through stamping out the metal seal, having the above described configuration, from such metal sheet. Alternatively, the metal seal may be produced through laser cutting of the metal sheet followed by forming, e.g. by pressing or bending, the intended angles of the first retainer flange, the second retainer flange, as well as the stiffening lips.

[0048] As previously mentioned, the first retainer flange is arranged to extend at first obtuse angle relative to the second annular surface of the annular seal body portion, the second retainer flange is arranged to extend at a second obtuse angle relative to said second annular surface, and the first and second stiffening lips are each arranged to extend at a third obtuse angle relative to said second annular surface. The first obtuse angle may be substantially equal to the second obtuse angle, as already mentioned above. Moreover, the third obtuse angle may be substantially equal to at least one of the first obtuse angle and the second obtuse angle. It is however possible that at least the first obtuse angle is greater than the third obtuse angle.

[0049] It should be noted that the first retainer flange is configured to retain the metal seal through the free end of the first retainer flange abutting a surface of an annular surface groove of a first coupling member and the second retainer flange is configured to retain the metal seal through the free end of the second retainer flange abutting the surface of the annular surface groove diametrically opposite to first retainer flange. In order for the first and second retainer flanges to abut said surface of the annular surface groove of the first coupling member, the first and second obtuse angles should naturally be selected in dependence of the respective slant height of the first and second retainer flanges, or vice versa. The slant height is the (shortest) distance from the fixed end of the respective retainer flanges (i.e. the ends connected to the radially inner circumferential edge of the annular seal body portion) to their respective free ends.

[0050] The stiffness of the herein described metal seal increases as the third obtuse angle decreases. However, the third obtuse angle should not be so low that it may be difficult to produce the metal seal within acceptable production tolerances, and / or make it more difficult to install and replace the metal seal in the flat face coupling arrangement. Therefore, the third obtuse angle y may for example be from 130° to 155°, suitably from 140° to 155°. Moreover, the third obtuse angle y may be substantially equal to, or less than, the first obtuse angle a, at which the first retainer extends relative to the second annular surface. One advantage of selecting the first and third obtuse angles to be substantially equal is that it may reduce the manufacturing costs and improve production tolerances, at least in case the second obtuse angle is substantially equal to the first and third obtuse angles.

[0051] The first and second stiffening lips are not intended to abut any surface of the annular surface groove of the first coupling member. Therefore, each of the first and second stiffening lips may suitably have a slant height which is less than the slant height of at least the first retainer flange. This may apply irrespectively of whether the third obtuse angle is substantially equal to, or different from, the first obtuse angle. Like in case of the first and second retainer flanges, the slant heigh of each of the first and second stiffening lips corresponds to the (shortest) distance from their respective fixed ends (i.e. their respective ends connected to the radially inner circumferential edge of the annular seal body portion) to their respective free ends.

[0052] At least the first retainer flange may suitably have a slant height which is equal to or greater than 0.15*r and equal to or less than 0.25*r, where r corresponds to the radius of the radially inner circumferential edge of the annular seal body portion.

[0053] As previously mentioned, the first retainer flange is connected to the radially inner circumferential edge along a first arc of said circumferential edge, and the second retainer flange is connected to the radially inner circumferential edge along a second arc of said circumferential edge. Said first arc may suitably be longer than the second arc. In other words, the first retainer flange may suitably have a longer circumferential extension along the radially inner circumferential edge of the annular seal body portion than the corresponding circumferential extension of the second retainer flange. Thereby, the ability to retain the metal seal may be improved while still allowing for an easy and reliable installation of the metal seal relative to a first coupling member of a flat face coupling arrangement. The first arc may for example have an arc length corresponding to a central angle of between 80° and 130° of the radially inner circumferential edge. Preferably, the first arc may for example have an arc length corresponding to a central angle of between 90° and 120°. The second arc may have an arc length corresponding to a central angle of between 25° and 75° of the radially inner circumferential edge. Preferably, the second arc may have an arc length corresponding to a central angle of between 30° and 70° of the radially inner circumferential edge.

[0054] A first exemplifying embodiment of the herein described metal seal will in the following be described with reference to Figures 1 to 3. Figure 1 illustrates a top view of the first exemplifying embodiment of the metal seal 1. Figure 2 illustrates a cross sectional view of the metal seal 1 along line B-B of Figure 1. Figure 3 illustrates a perspective cross sectional view along line C-C of Figure 1. As shown in Figure 1, the metal seal 1 comprises an annular seal body portion 2 coaxial with a central axis A of the metal seal 1. The annular seal body portion 2 may suitably be rotationally symmetrical about the central axis A. The annular seal body portion 2 comprises a radially inner circumferential edge 3, a radially outer circumferential edge 4, a first annular surface 5, and a second annular surface 6 (shown in Figure 2). The first and second annular surfaces 5, 6 are configured to extend in parallel, and perpendicular to the central axis A, at least when the metal seal 1 is used in a flat face coupling arrangement.

[0055] The metal seal 1 further comprises a first retainer flange 7 and a second retainer flange 8. The first and second retainer flanges 7, 8 are configured to retain the metal seal relative to a first coupling member when the metal seal is arranged in the flat face coupling arrangement as will be described in further detail below.

[0056] Each of the first and second retainer flanges 7, 8 extends from the radially inner circumferential edge 3 of the annular body portion 2 and is thus connected to the annular seal body portion 2 at the radially inner circumferential edge 3. The first retainer flange 7 is connected to the annular seal body portion 2 along a first arc 3a of the radially inner circumferential edge 3. The second retainer flange 8 is connected to annular seal body portion 2 along a second arc 3b of the radially inner circumferential edge 3. The second arc 3b is arranged diametrically opposite to the first arc 3a of the radially inner circumferential edge 3. Thus, the second retainer flange 8 is arranged diametrically opposite to the first retainer flange 7 with respect to the annular seal body portion 2. Moreover, as shown Figure 1, the first arc 3a may suitably be longer than the second arc 3b. The first arc 3a may for example have an arc length corresponding to a central angle q of between 80° and 130° of the radially inner circumferential edge 3. The second arc 3b may for example have an arc length corresponding to a central angle of between 25° and 75° of the radially inner circumferential edge 3, preferably between 30° and 70°.

[0057] As shown in Figure 2, the first retainer flange 7 extends from the radially inner circumferential edge 3 at a first obtuse angle a relative to the second annular surface 6. Moreover, the first retainer flange 7 has a slant height H7 as seen from its fixed end, said fixed end being connected to the radially inner circumferential edge 3 as evident from the above, to its free end 7a. The slant height H7 of the first retainer may for example be equal to or greater than 0.15*r, and equal to or less than 0.25*r, where r corresponds to a radius of the radially inner circumferential edge 3 (see Figure 1). Furthermore, the second retainer flange 8 extends from the radially inner circumferential edge 3 at a second obtuse angle p relative to the second annular surface 6 and has a slant height H8, as seen from its fixed end to its free end 8a. The second obtuse angle may be substantially equal to the first obtuse angle a, but the present disclosure is not limited thereto. In case the second obtuse angle p is substantially equal to the first obtuse angle a, the slant heights H7 and H8 of the respective retainer flanges 7, 8 may correspond to each other. In any case, the obtuse angles and slant heights of the respective retainer flanges 7, 8 are selected such that the respective free ends 7a, 8a, of the retainer flanges 7, 8 will abut, and thereby engage with, a radially inner circumferential wall of an annular surface groove of the first coupling member when the metal seal is arranged in the flat face coupling member (as will be described below).

[0058] As shown in Figure 1, the metal seal 1 further comprises a first stiffening lip 9 and a second stiffening lip 10, each extending from the radially inner circumferential edge 3 of the annual seal body portion 2. The purpose of the stiffening lips 9, 10 is to increase the stiffness of the metal seal 1 and thereby reduce the risk for distortion thereof. Each of the first and second stiffening lips 9, 10 are arranged to extend with a third obtuse angle y relative to the second annular surface 6 (cf. Figure 3). Thus, the stiffening lips 9, 10 extend from the annular seal body portion 2 in the same axial direction as the first and second retainer flanges 7, 8. The third obtuse angle y may for example be from 130° to 155°, suitably from 140° to 155°. Moreover, the third obtuse angle y may be substantially equal to, or less than, the first obtuse angle a, at which the first retainer 7 extends relative to the second annular surface 6.

[0059] The first and second stiffening lips 9, 10 may each suitably be connected to the annular seal body portion 2 along a respective arc of the radially inner circumferential edge 3 such as to essentially fill the arc gap between the between the first arc 3a and the second arc 3b, as shown in Figure 1. Each of the first retainer 7 and the second retainer 8 may be separated from the adjacent stiffening lips 9, 10 by slits 12 or the like.

[0060] The first stiffening lip 9 has a slant height H9 (see Figure 4) as seen from its fixed end, connected to the radially inner circumferential edge 3 of the annular seal body portion 2, to its free end 9a. Similarly, the second stiffening lip 10 has a slant height H10 (see Figure 3) from its fixed end to its free end 10a. The slant heights H9 and H10 may suitably correspond to each other. Moreover, each of the slant heights H9, H10 of the first and second stiffening lips 9, 10 may suitably be less than the slant height H7 of the first retainer flange 7. Figure 4 illustrates a cross sectional view of part of a first coupling member 21 of a flat face coupling arrangement according to the present disclosure, with a metal seal 1 as shown in Figure 1 arranged so as to be retained in the first coupling member 21.

[0061] The first coupling member 21 comprises an annular flat sealing surface 31 arranged at a first axial end 30. The first coupling member 21 further comprises an annular surface groove 32 extending axially into the first coupling member 21 from the first axial end 30. The annular surface groove 32 comprises an axially extending radially inner circumferential wall 33, an axially extending radially outer circumferential wall 34, and an annular bottom wall 35.

[0062] The metal seal 1 is arranged with respect to the first coupling member 21 so that the second annular surface 6 of the annular seal body portion 2 engages with the annular flat sealing surface 31 of the first coupling member 21. Moreover, the metal seal 1 is arranged so that the free end 7a (cf. Figures 1 and 2) of the first retainer flange 7 abuts, and thus engages, the radially inner circumferential wall 33 of the annular surface groove 32 at a distance from the bottom wall 35. It should here be noted that, although not visible in the cross sectional view shown in Figure 4, also the free end 8a of the second retainer flange 8 is arranged to abut the radially inner circumferential wall 33 of the annular surface groove 32 at a distance from the bottom wall 35. Thereby, it is ensured that the metal seal 1 is retained in the first coupling member 21 and will remain retained when the flat face coupling arrangement is fully assembled and tightened.

[0063] As an alternative to each of the first and second retainer flanges 7, 8 being arranged so that their respective free ends 7a, 8a abut against the radially inner circumferential wall 33 of the annular surface groove 32 at a distance from the bottom wall 35, it may also be possible to modify the slant heights as well as the obtuse angles by which the respective retainer flanges extend relative to the second annular surface 6 of the annular seal body portion 2 so that one or both of the free ends 7a, 8a, abuts the corner where the radially inner circumferential wall 33 meets the bottom wall 35 of the annular surface groove 32.

[0064] In contrast to the first and second retainer flanges 7, 8, the first stiffening lip 9 is however arranged so as to not abut against any one of the surfaces of the annular surface groove 32 of the first coupling member 21. The same applies to the second stiffening lip 10, although not visible in the cross sectional view shown. The reason therefore is that the first and second stiffening lips 9, 10 are adapted to increase the stiffness of the metal seal 1 and should not impair the ability to install the metal seal 1 in the first coupling member 21. Figure 5 illustrates a cross sectional view of a flat face coupling arrangement 20 in accordance with one exemplifying embodiment of the present disclosure. The flat face coupling arrangement 20 has a longitudinal axis L and comprises a first coupling member 21, a second coupling member 22, a flared pipe 23, and a third coupling member 24. The first coupling member 21 may alternatively be referred to as a body of the flat face coupling arrangement. The second coupling member 22 may alternatively be referred to as a nut. Moreover, the third coupling member 24 may alternatively be referred to as a sleeve. The flat face coupling arrangement further comprises a metal seal 1 as shown in Figure 1. The metal seal 1, the first coupling member 21, the second coupling member 22, the flared pipe 23, and the third coupling member 24 are coaxially arranged in the flat face coupling arrangement. Furthermore, the metal seal 1 is arranged so as to be interposed between flat annular end surfaces of the first coupling member 21 and the flared pipe 23. More specifically, the annular seal body portion 2 of the metal seal 1 is interposed between the flat end surfaces of first coupling member 21 and the flared pipe. The metal seal 1 is thus configured to prevent leakage of gas, flowing axially through the flat face coupling arrangement, in the radial direction between the first coupling member 21 and the flared pipe 23.

[0065] Figure 5 furthermore illustrates how each of the first retaining flange 7 and the second retaining flange 8 extends into the annular surface groove 32 (which may correspond to a so called O-ring groove of a conventional ORFS fitting) of the first coupling member 21 and abuts an internal wall of the annular surface groove 32 to thereby retain the metal seal 1.

[0066] Figure 6 illustrates a top view of a second exemplifying embodiment of the herein described metal seal 1. The metal seal 1 shown in Figure 6 corresponds to the metal seal 1 shown in Figure 1, except that each of the first and second stiffening lips 9, 10 are directly connected to the first retainer flange 7. In other words, the first and second stiffening lips 9, 10 are not separated from the first retainer flange 7 by a respective slit or the like. The first and second stiffening lips 9, 10 are however distinguished from the first retainer flange 7 by each having a shorter slant height H9, H10 than the slant height H7 of the first retainer flange 7. However, the first and second stiffening lips 9, 10 are still separated from the second retainer flange 8 by a respective slit 12.

[0067] Although not visible in Figure 6, each of the first and second retaining lips 9, 10 extends from the annular seal body portion 2 at a third obtuse angle relative to the second annular surface of the annular seal body portion 2 which is substantially equal to the first obtuse angle by which the first retainer flange 7 extends from the annual seal body portion 2. In other words, the first retainer flange 7, the first stiffening lip 9, and the second stiffening lip 10 have substantially the same inclination relative to the annular seal body portion 2.

[0068] Figure 7 schematically illustrates an example of a fuel system 50 in accordance with the present disclosure. The fuel system 50 is configured to storage of cryogenic and / or compressed hydrogencontaining fuels and / or transportation of such fuels to a fuel consuming device 51. The fuel consuming device 51 may for example be a combustion engine. The fuel consuming device 51 is not part of the fuel system 50 as such, and is therefore shown with dashed lines in the figure.

[0069] The fuel system 50 comprises a first storage tank 52 and a second storage tank 53, each configured for storage of cryogenic and / or compressed hydrogen containing fuel. The fuel system further comprises numerous fuel lines 54 through which e.g., gaseous fuel may flow through. The fuel lines 54 may for example comprise tank filling lines allowing fuel to be filled into the second storage tank 53 via the first storage tank 52 (or vice versa), recovery lines, boil-off lines, fuel supply lines for transportation of fuel to the fuel consuming device etc. The fuel system further comprises numerous fittings 55 (in the figure illustrated as boxes) connecting hoses and pipes (forming e.g., the fuel lines 54) with each other and / or connecting such hoses / pipes to the storage tanks 52, 53. One or more of these fittings 55 may correspond to the herein described flat face coupling arrangement 20.

[0070] Figure 8 schematically illustrates an example of a vehicle 100, here illustrated as a truck, as seen in a side view. The vehicle 100 comprises a fuel system 50 in accordance with the present disclosure, such as the fuel system 50 shown in Figure 7. The vehicle 100 further comprises a combustion engine 60. The combustion engine 60 may be driven using gaseous fuel provided by the fuel system 50. The fuel system 50 may be configured for storage of cryogenic and / or compressed hydrogen-containing fuel and transportation of such a fuel to the combustion engine 60.

Claims

CLAIMS1. A metal seal (1) for a flat face coupling arrangement, the metal seal (1) having a central axis (A) and comprising: an annular seal body portion (2), coaxial with the central axis (A), comprising a radially inner circumferential edge (3), a first annular surface (5), and a second annular surface (6), the first and second annular surfaces (5, 6) being configured to extend in parallel and perpendicular to the central axis (A) when the metal seal is used in a flat face coupling arrangement, a first retainer flange (7) extending from the radially inner circumferential edge (3) at a first obtuse angle (a) relative to the second annular surface (6), a second retainer flange (8) extending from the radially inner circumferential edge (3) at a second obtuse angle (P) relative to the second annular surface (6), the second retainer flange (8) being arranged diametrically opposite to the first retainer flange (7) with respect to the annular seal body portion (2), and a first stiffening lip (9) and a second stiffening lip (10), each extending from the radially inner circumferential edge (3) of the annular seal body portion (2) at a third obtuse angle (y) relative to the second annular surface (6).

2. The metal seal (1) according to claim 1, wherein the first obtuse angle (a) is greater than the third obtuse angle (y).

3. The metal seal (1) according to any one of claims 1 or 2, wherein the first obtuse angle (a) is substantially equal to the second obtuse angle (P).

4. The metal seal (1) according to any one of the preceding claims, wherein the third obtuse angle (y) is from 130° to 155°; preferably from 140° to 155°.

5. The metal seal (1) according to any one of the preceding claims, wherein each of the first retainer flange (7), the second retainer flange (8), the first stiffening lip (9), and the second stiffening lip (10) has a slant height (H7, H8, H9, H10) as seen from their respective fixed ends, connected to the radially inner circumferential edge (3), to their respective free ends (7a, 8a, 9a, 10a), and wherein the slant height (H9, H10) of each of the first stiffening lip (9) and the second stiffening lip (10) is less than the slant height (H7) of the first retainer flange (7).

6. The metal seal (1) according to claim 5, wherein the slant height of the first retainer flange (7) is equal to or greater than 0.15*r and equal to or less than 0.25*r, where r corresponds to a radius of the radially inner circumferential edge (3).

7. The metal seal (1) according to any one of the preceding claims, wherein the first retainer flange (7) is connected to the radially inner circumferential edge (3) along a first arc (3a) of said circumferential edge (3), and the second retainer flange (8) is connected to the radially inner circumferential edge (3) along a second arc (3b) of said circumferential edge (3), the first arc (3a) being longer than the second arc (3b).

8. The metal seal (1) according to claim 7, wherein the second arc (3b) has an arc length corresponding to a central angle ( ) of between 25° and 75° of the radially inner circumferential edge (3); preferably between 30° and 70°.

9. The metal seal (1) according to any one of claims 7 or 8, wherein the first arc (3a) has an arc length corresponding to a central angle (q) of between 80° and 130° of the radially inner circumferential edge (3); preferably between 90° and 120°.

10. A flat face coupling arrangement (20) comprising: a metal seal (1) according to any one of the preceding claims and a first coupling member (21) coaxially arranged with the metal seal, the first coupling member (21) comprising an annular flat sealing surface (31) arranged at a first axial end (30), and an annular surface groove (32) extending axially into the first coupling member (21) from the first axial end (30), said annular surface groove (32) comprising an axially extending radially inner circumferential wall (33), wherein the metal seal (1) is arranged so that its second annular surface (6) engages with the annular flat sealing surface (31) of the first coupling member (21) and a free end (7a) of the first retainer flange (7) engages the radially inner circumferential wall (33) of the annular surface groove (32).

11. The flat face coupling arrangement (20) according to claim 10, wherein the metal seal (1) is arranged so that each of the first stiffening lip (9) and the second stiffening lip (10) of the metal seal (1) extends into the annular surface groove (32) without engaging the radially inner circumferential wall (33) or a bottom wall (35) of the annular surface groove (32).

12. A fuel system (50) configured for storage of cryogenic and / or compressed hydrogencontaining fuels and / or transportation of such fuels to a fuel consuming device (51), the fuel system comprising a flat face coupling arrangement (20) according to any one of claims 10 and 11.

13. The fuel system (50) according to claim 12, wherein the fuel system is a liquified natural gas fuel system, a compressed natural gas fuel system, or a cryo-compressed hydrogen fuel system.

14. A vehicle (100) comprising the fuel system according to any one of claims 12 and 13.

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