Field of the Invention

The present invention relates to a valve comprising one or more gaskets, where each gasket is mounted into a groove, track or similar area between a first and a second essentially parallel surfaces. The present invention relates to a method for sealing area between two oppositely, and preferably parallel, positioned surfaces in a valve.

In addition the present invention relates to the use of the valve or the method for providing an effective seal in valves operating under extreme conditions.

Background of the Invention

When different mechanically acting products are constructed of several parts which are assembled into the final product, e.g. by connecting separate parts using flanges, threaded connections etc., it is common practice to create a seal at the interface using one or more gaskets such as O-rings.

An O-ring, also known as a packing, is a mechanical gasket in the shape of a torus. It is a loop of elastomeric material with a substantially circular, oval cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.

Sealing rings may also have a cross section other than circular or oval, e.g. polygonal, square, rectangular, triangular or more complex shapes, such as X-shaped. The O-ring may be used in static applications in which the O-ring is positioned between two or more stationary parts. The O-ring is also applicable in dynamic applications where there is relative motion between the parts and the O-ring. Dynamic examples include rotating pump shafts and hydraulic cylinder pistons. O-rings are one of the most common seals used in machine design because they are inexpensive, easy to make, reliable, and have simple mounting requirements. They can effectively seal areas in which large pressure, e.g. in the MPa range, is applied.

Thus, O-rings are used as seals in all types of valves e.g. butterfly valves, gate valves or ball valves, e.g. trunnion mounted ball valves, floating ball valves or yoked ball valves. For example, when a ball valve is assembled there are several positions which require a seal, such as static connections between two non-moving parts of the housing or between a the housing and a stationary shaft in a trunnion mount used to support the ball valve element from below in a trunnion mount of a ball valve. In addi- tion, dynamic seals, in which an O-ring is mounted between two or more moving parts, are required at several positions in a ball valve, e.g. for sealing between the ro- tatable stem and the valve housing or for creating a seal between the housing and a movable valve seat. The O-ring is usually made of an elastomeric material, typically a polymer material, such as a rubber.

The most common O-ring materials in the valve industry are nitrile butadiene rubber ( BR), hydrogenated nitrile butadiene rubber (FINBR), ethylene propylene diene Monomer (EPDM), Fluorocarbon rubber (FKM), silicone or fluorosilicone rubber although other materials may be used as well.

The main problem with elastomeric seals are very low and very high working temperatures, where the elastomeric material of the seal can change properties, due to very high or very low temperatures, which may influence the sealing ability. For example, high working temperatures may result in softening of the material, and very low temperatures causes the material to stiffen because the O-ring loses its elasticity and it may become brittle. Thus, both high and low temperatures may thus reduce the sealing ability of the O-ring. Table 1 below indicates working temperature intervals for the above-mentioned materials. Heat resistance temperature is regarded the maximum temperature at which the material can operate under static conditions without losing the sealing capability, and cold flexibility is the lowest temperature at which the material can work under static conditions without losing its flexibility and becoming brittle which may cause the seal to losing its sealing capability.

When working under dynamic conditions, the temperature interval is narrower because the mechanical force acting on the material under dynamic conditions may cause defects on the material before the endpoints of the intervals for static conditions are reached. Similarly, when working under high pressure under either dynamic or static conditions, e.g. above 100 bar, the temperature interval is also narrower because the pressure applied results in a mechanical force acting on the material.

As an alternative to O-rings, other types of seals, such as lip seals, may be used for sealing a gap between two parts. The lip-seal contains a sealing material and an energizing material which is usually a steel spring. The steel spring may be cast in in different shapes and the sealing material is e.g. polytetrafluoroethylene (i.e. Teflon™ or PTFE) or modified PTFE, i.e. PTFE modified to improve the temperature range and/or durability. However, lip-seals are expensive, due to their complicated construction and their manufacturing costs, and their use is thus limited because of the increase in costs. In addition, such alternative seals suffer from drawbacks when applied e.g. in valves which transport fluids, in particular gases or liquids, carrying particles. The particles in the fluid may cause abrasion on the surface of the seal, which leads to scratches which may result in a reduced sealing effect.

Thus, it is possible to select a suitable material for O-rings which can provide an effective seal also at temperatures of -40 °C and at high pressures, such as 100-160 bar.

When gas fuel is transported over large distances in pipe lines, especially in pipe lines mounted above the ground, the gas and the pipelines, including any valves mounted therein, are subjected to large temperature variations. During the summer, the temperature in the gas and the pipeline, including any valve mounted herein, may become relatively high, e.g. up to 40-60 °C and in extreme situations even higher in certain geographical areas, whereas the temperature during winter time may become very low, e.g. below -40 °C or in extreme cases even lower, e.g. as low as -60 °C or even lower. Thus, the pipe line, including valves mounted herein will have to be effectively sealed by gaskets which are effective in a very broad temperature range

The same will apply for pipe lines transporting liquids e.g. water or liquid fuel, but the temperatures and the pressure may be different compared to the temperature and pressure in gas pipelines.

However, tests have shown that O-rings made of the above-mentioned materials cannot provide an effective seal under such extreme conditions, i.e. at high pressure, such as up to 250 bar, or preferably up to 200 bar, or in particular up to 160 bar, such as 1.0-200 bar or preferably 1.0-170 bar, and which is also effective at extremely low temperatures e.g. at temperatures as low as -80 °C, while also providing sufficient sealing capability at higher temperatures, such as temperatures up 200 °C.

Object of the Invention

Thus, it is an object of the present invention to provide an effective seal under extreme conditions, i.e. at high pressures, such as up to 250 bar, preferably up to 200 bar, in particular at a pressure of up to 160 bar, such as 1.0-200 bar or preferably 1.0-170 bar, and at extremely low temperatures e.g. at temperatures as low as -40 °C, -60 °C and even lower under static as well as under dynamic conditions, while also providing sufficient sealing capability at higher temperatures, such as temperatures up to 100 °C or even up to 200 °C .

It is also an object of the present invention to provide a seal, which is equally effective at higher temperatures, e.g. at up to 200 °C or up to at least 100 °C under such high pressures. It is also an object of the present invention to provide an effective seal in a large temperature range, e.g. from -80 °C to at least 100 °C, preferably up to 200 °C at a test pressure of 160 bar. The present invention is thus effective in a temperature range of - 80-200 °C, such as -80-100 °C, or -60-200 °C, depending on the material of the O- rings, e.g. when BR, HNBR or FKM are used. The temperature interval in which the O-rings seals effectively is thus broadened considerably in relation to the current temperature range; in particular in the low temperature end of the range for which an effective seal is obtained using O-ring in static conditions.

The object of the invention is also to provide a sealing system, which can be used at different positions in valves, such as ball valves, for providing an effective seal at positions where sealing effect is necessary or desirable, e.g. between the valve stem and the housing, between the valve seat and the housing, between connections of different parts of the housing and/or e.g. at a trunnion mount in a ball valve. In addition to the above-mentioned advantages it is also an object of the present invention to provide an effectively sealing system in valves at low costs.

Description of the Invention

The above-mentioned drawbacks of the prior art and/or the above-mentioned objects of the present invention are obtained by a ball valve for a fluid transporting pipe line comprising one or more gaskets, where each gasket is mounted in a groove, track or similar area between a first and a second essentially parallel surfaces, where each gasket is intended for being pressed against at least a third surface in the groove by means of a force acting against the gasket, where the force is at least applied by fluid in the valve, and wherein the third surface is planar or essentially planar and provided at an angle a or wherein the third surface is non-planar and where a tangent to the surface is provided with an angle a, where the angle a is greater than 0 degrees and less than 90 degrees in relation to the first or second essentially parallel surfaces.

The above-mentioned drawbacks of the prior art and/or the above-mentioned objects of the present invention are also obtained by method for sealing area between two oppositely, and preferably parallel positioned surfaces in a valve comprising the steps of providing a valve comprising a groove track or similar area between a first and a second essentially parallel surfaces for a gasket, such as an O-ring, and which gasket is intended for being pressed against a third end surface in the groove by means of a force acting against the gasket, wherein the groove comprises a third surface between the end surface and one of the essentially parallel surfaces, which third surface is pro- vided at an angle a in relation to the essentially parallel surface and wherein the method comprises applying a force acting on the gasket in direction which is essentially parallel to the first and second parallel surfaces and pressing the gasket against the third surface whereby the gasket becomes wedged between at least one of the first and second parallel surfaces and the third surface, and optionally the end surface.

When producing valves, gaskets are mounted in grooves at relevant positions where it is necessary to provide a seal between two opposed surfaces. Such seals are e.g. positioned between the valve stem and the stem guide in the valve housing or between the valve housing and a trunnion in a trunnion mounted ball valve, between the valve seat and the valve housing and between two discrete parts of the valve housing which are connected e.g. by a threaded connection, a flange connection or similar commonly used connections in valve housings. The grooves, in which the gasket is usually provided between two elements in the valve, comprise two essentially parallel surfaces, i.e. a first and a second surface as well as one or two end surfaces. The grooves are e.g. provided between two opposed surfaces or around the circumference of a valve part, such as the valve stem and the interior surface in the valve stem guide; around the circumference of the trunnion in a trunnion mounted ball valve and the corresponding interior surface of the valve housing; at the rear side of a moveable valve seat and the opposed interior surface of the valve housing, or between two opposed surfaces in a connection in the valve housing.

When valves are working under extreme conditions, e.g. very low surrounding tem- peratures, in particular at temperatures as low as to -40 °C, to -60 °C or even to -80 °C, the gaskets in the valves usually become hard and brittle and will lose their flexibility and thus their sealing effect as already indicated by the examples shown in table 1. Such conditions can e.g. occur during winter time in valves arranged in pipe lines intended for transporting fluids, e.g. gas, water or liquid fuel at a very high pressure, lines, such as pipe lines arranged on the ground or optionally subterranean pipelines.

This effect can effectively be counteracted by providing the third surface in the groove, which extends at an angle a in relation to the first or second surfaces and thus provides a frustoconical surface in the groove.

A force F is provided for acting on the O-ring for pushing it against an end surface of the groove. The pressure applied to the O-ring by the force F in a standard prior art groove results in deformation of the elastic material by which it rests against the first and second parallel surfaces as well as an end surface in the groove, and thus provides a sealing point at both opposing parallel surfaces and the end surface.

The third angled surface arranged in the groove according to the present invention provides a wedge shaped surface, between the first or second surface and an end surface. When the O-ring is pushed against this third surface by the force F acting in par- allel to the first and second surfaces and towards the end surface of the groove, the O- ring will expand in diameter when climbing up on the angled third surface due to its elastic nature. The pressure applied to the O-ring by the force F in the groove according to the present invention results in deformation of the elastic material by which it rests against the first or second parallel surfaces as well as an the third angled surface in the groove, and thus provides only two sealing points at the third angled surface and the opposing first or second surface. Because of the hardness (i.e. the elastomeric properties) of the O-ring a compression of the O-ring will occur in radial direction between the surfaces acting on the O-ring when it climbs the third angled surface due to the force F acting on the O-ring. Thus, the force F for providing an effective seal in a conventional groove is divided into three sealing points where the reaction force RF acts in each sealing point whereas in the present invention the force F is divided between two sealing points. The result is an increased sealing force, RFP, or reaction acting between the gasket and the surface of the groove in each sealing point, which increases the sealing efficiency when applying the same force F to the gasket.

If we in a very basic way compare the reaction forces, we can see that in a simple cal- culation Rpp > RF:

Basic calculation of reaction forces on a gasket in a prior art groove:

F = 3 * R _F Basic calculation of reaction forces on gasket in a groove with angled third surface:

F — 2 * Rpp

_ F

R ^{fp =} 2

Thus, the force acting in the sealing points is clearly larger than in the prior art when the same force F is applied to the gaskets in the groove according to the present invention in relation to the prior art.

When applying a force F in a groove having the third surface of an angle a, the tightening force Fi acting between the O-ring and the internal surfaces of the groove is determined by:

I: F= Fi*sina (0° < a < 90°) When α=90° then it is clear that F= Fi and when F is constant and the angle is decreased, i.e. a→0, then the tightening force Fi increases, Fi→∞.

Thus, an increased tightening force (Fi) can be achieved by increasing the force (F) decreasing the slope of the groove, i.e. smaller angle a. This means that a flat angle (a) requires a lower force (F), but the displacement of a spring providing the force F acting on the gasket will be large. Similarly, a steep angle (a) requires a higher force (F), but the displacement of a spring providing the force F acting on the gasket will be small.

Thus, the same force F (e.g. a spring force or other force providing means) results in an improved sealing efficiency in the groove according to the invention with the angled third surface, because the gasket is pressed against the surfaces with increased force surface pressure/reaction force/sealing capability compared to the prior art groove-gasket reaction.

In addition, the present invention provides a solution resulting in less torque than a conventional lip seal due to the spring force acting on the O-ring. As mentioned above the gasket (in this case the O-ring) is expanding when it climbs the angled third surface. Expanding of the sealing element improves the resistance against shrinkage, which is important in low temperature regimes, because elastomeric materials have an increased ability to shrink (comparing to e.g. steel) and thus an increased tendency to shrink at low temperatures.

The result is an effective sealing between the gasket and the surfaces in the groove in particular under dynamic conditions and the sealing effect is equally effective under static conditions. In addition, the present invention reduces or counteracts any loss in sealing effect caused by the material of the gasket hardening and becoming brittle and thus less flexible when the valve is mounted in environments which are subjected to extremely low temperatures extremely low temperatures e.g. at temperatures as low as to -80 °C and also at temperatures of up to 200 °C or -60°C to 100 °C. Further, due to the flexible or elastic nature of the material used as gaskets, in particular O-ring seals according to the present invention, the O-ring is less subjected to wear arising from abrasion by the particles present in the fluid, in particular the gas or liq- uid, which is transported through valves.

Thus, the seals in the valve according to the present invention exhibit a longer life time, which reduces the maintenance frequency and costs. The gasket will provide an effective seal in the valve even at high pressure conditions, such as at a pressure of up to 250 bar, preferably up to 200 bar, such as up to 160 bar or 1.0-200 bar, in particular at a pressure of e.g. 1.0-170 bar.

The reference conditions for testing sealing efficiency of the gaskets valve is -60 °C and 160 bar.

In one embodiment of the invention, the gaskets provided in the groves are conventional O-rings because they are able to provide an effective seal when applying a certain force and where the O-rings are pressed by the force Fi to climb up the cone shaped third surface. This results in low cost sealing elements which are effective also in extreme environments such as low temperatures and high pressures as discussed above. Thus, when selecting the material for the O-ring it is possible to provide effective sealing in static as well as in dynamic conditions in a wide temperature range as discussed above.

O-rings are usually more or less circular rings of an elastomeric material, e.g. such as those mentioned in table 1 above or as commonly used in production of O-rings. The cross section shape of the O-rings is e.g. circular, oval, square, rectangular, triangular or X-shaped.

In a preferred embodiment of the present invention, the third surface comprises one or more surfaces, which are angled at the angle a in relation to the essentially parallel surface. A single planar surface angled at an angle a results in a frustoconical surface in the groove which results in a linearly increasing force Fi acting on the O-ring. Where the angle a of each of a number of surfaces is increasing at decreasing distances to the third surface, a number of differently angled frustoconical surfaces are provided in the groove, whereby the force Fi acting on the O-ring can be increased linearly and in stepwise manner because of the increasing angle a on the frustoconical sur- faces.

It is preferred that the angle a is 5-50 degrees or preferably 5-45 degrees, because in this interval, the necessary force F to be applied on the gasket for obtaining an effective sealing effect, e.g. at test conditions of -60 °C and a pressure of 160 bar, is rela- tively low, and thus may be provided by less expensive means for creating the necessary force F. The present invention will also work in a groove where the third surface has an angle a which is above 50 degrees, e.g. 50-75 degrees but this will, according to the formula I above, require an increased force F applied to the gasket and thus result in increased production costs.

Alternatively it is possible to provide a non-linearly increasing force Fi and thus an increased sealing effect by constructing the third angled surface so that the angle a is continuously varied in relation to the essentially parallel surfaces, such as by continuously increasing the angle a in relation to the essentially parallel surface at decreasing distances to the third surface or by increasing continuously the angle a and subsequently decreasing the angle a in relation to the essentially parallel surface at decreasing distances to the third surface.

The force F acting on the gasket by the fluid in the valve is preferably further applied by a spring, or via a lip seal, via a graphite gasket and/or via a number of additional O- rings, which, further optionally in combination with a washer, are intended for acting on the gasket.

When a spring is used, the spring force is easily adjusted according to the force F nec- essary for obtaining an effective seal by the gasket when working under extreme conditions, such as e.g. at test conditions of -60 °C and a pressure of e.g. 160 bar, simply by selecting a spring having the required spring force F. A spring provides a constant force F acting on the gasket. In addition, a simple spring is very cheap, which will reduce the overall costs of a valve while also providing the effective seal. A spring can provide the spring force over a relatively long distance in a groove and the spring can be produced in a very large range of dimensions, whereby the need for applying a force on an O-ring in almost any size can be easily provided, simply by selecting and buying a spring in the right size and with the optimal spring force for the particular valve.

Alternatively, the force F can be applied by a lip seal which effectively transfers the pressure in the grove into a linear force F acting on the gasket and presses the gasket against the end surface whereby the gasket slides up on the third angled surface. A lip seal can, in addition to providing the force F acting on the gasket when pressurized, also act as a flow reducer in case there is a leak through the groove. In addition, when the pressure in the groove is relieved, the force acting on the gasket is also relieved and thus may reduce the tension on the gasket in periods of sufficiently low pressure. This may prolong the lifetime of the O-ring because the O-ring material is less likely to lose its elasticity due to fatigue of the material

A similar effect can be obtained by providing a graphite gasket and/or a number of additional O-rings, which intended for providing the force F acting on the gasket. A number of O-rings will apply a spring force due to the elastic nature of the material, optionally in combination with the pressure provided in the groove by the fluid flowing through the valve.

In a preferred embodiment, at least two individual gaskets are acting against oppositely directed angled third surfaces by means of a force acting against each of the gas- kets. The force acting against each of the gaskets may com form e.g. a spring with a washer arranged at each end of the spring. Each washer can act against one of the two gaskets arranged in each end of the groove. In this case, the sealing system is working in two stages: Normal stage and Cold stage. The normal stage is when the sealing element has the ability to seal without adding additional force F from the spring. In this situation, the spring biased washers only help to keep the tightness. If the pressure comes from one end of the groove at normal stage the gasket in that end will move towards the other end and provide a seal in the other end and thus medium from leak. In situations where the temperature will be very low, e.g. below -40 °C or e.g. at a test temperature of -60 °C (cold stage), the pressure applied from the same end, may result in a leak, but this leak will be counteracted by the spring biased washer and the gasket in the opposite end of the groove.

The groove may also be constructed so that two or more gaskets are arranged in the two separate but interconnected grooves and that a force F is acting on each of the gaskets, is applied in opposite direction as discussed below in relation to one embodiment of the invention.

Hereby, the groove is provided with two separate pressure seals, which each provide an effective seal when the pressure in the groove is acting in the opposite directions.

The sealing system can be provided at several positions in a valve according to the present invention. Thus, the groove, track or similar area is preferably provided between a valve seat and the valve housing, where the valve seat is preferably moveably mounted in the valve housing; between a valve stem and a stem guide in the valve housing; between a valve trunnion and the valve housing in a trunnion mount, and/or between connections in the valve housing itself.

This provides the valve with an effective seal in the particular areas where sealing is necessary, also when the valve works under extreme conditions, in particular in positions where the gaskets work under dynamic conditions as well as under static conditions as discussed above.

In a particular preferred embodiment, the valve is a ball valve, such as a trunnion mounted ball valve, which is particularly well suited for mounting in e.g. gas pipe lines and thus may risk operating under extreme conditions of sometimes very low temperatures, where conventional O-ring gaskets may risk failing as discussed above.

Thus, the present invention also relates to use of the valve as described above or a method as described above for providing a seal in a valve, which is working in extreme environments, such as temperatures of -80 to 200 °C or -60 °C to 200 °C or -80 °C to 100 °C and/or at high pressures, such as up to 250 bar, or preferably up to 200 bar, or up to 160 bar, such as 1.0-200 bar or 1.0-180 bar or preferably 150-170 bar. In particular, the valves are used in a pipe line intended for fluid transport, in particular gas, water or liquid fuel.

Description of the Drawing

The present invention will be described with reference to the drawings in which: fig. 1 shows a cross sectional view of a ball valve with a trunnion mount, fig. 2 shows a cross sectional view of a conventional spring biased gasket in a groove,

fig. 3 is a graphical illustration of the distribution of the spring force applied in fig.

2,

fig. 4 shows a cross sectional view of a spring biased gasket in a groove, according to the present invention,

figs. 5a-e show cross sectional views of alternative forms of the groove according to the present invention,

fig. 6 shows a schematic overview of distribution of the force applied to a gasket in the present invention,

fig. 7 is a graphical illustration of the distribution of the spring force applied in fig.

4,

fig. 8 shows a cross sectional view of a spring biased gasket in a groove between a valve housing and a moveable valve seat according (dynamic conditions) in position A in fig. 1,

fig. 9 shows a cross sectional view of a groove with a dual action spring biased energised seal, which can apply to at least one of two gaskets,

fig.10 shows as cross sectional view of a sealing system having two single acting spring biased gaskets,

fig. 11 shows cross sectional view of a spring biased O-ring sealing the gap between the valve housing and a trunnion mount (static) at position C in fig. 1, or sealing the between the stem and the stem guide of the valve housing (dynamic) at position B in fig. 1,

fig. 12 shows a cross sectional view of a variant where a lip seal is used for applying a force to the gasket by means of the pressure applied in the valve, and fig 13 shows a cross sectional view of a variant where a stack of O-rings are used for applying the force to the gasket. Detailed Description of the Invention

The present invention will now be described in relation to a ball valve, in particular to a ball valve having a trunnion mount as shown in fig. 1 although the invention is not necessarily limited to being used in ball valves.

A ball valve may be constructed in a way in which a seal is provided between a movable valve seat and at valve housing, position A on fig. 1. In a conventional valve, e.g. a ball valve, the gasket 5 is provided in a groove which is provided between the valve housing E and the rear side of the back-up ring G on a valve seat by conventional metal working procedures, e.g. milling or turning, resulting in a shoulder in the internal circumference of the valve housing E and on the circumference of the rear surface of the backup ring on the valve G seat whereby the groove comprises two essentially parallel side walls 7,8 and two shoulders forming essentially parallel end walls 9 in the groove (see fig. 2).

Similarly sealing areas are usually provided between the valve stem H and the stem guide I, position B in fig. 1; between a trunnion mount J and the valve housing E, po- sition C in fig. 1 and/or where two individual parts Ei, E ₂ of the valve housing E are connected, such as position D in fig. 1.

A conventional groove for a gasket 5 is shown in fig. 2 which indicates that three reaction forces R _f acting between the groove surfaces 7,8,9 and the O-ring 5 as a result of a force F, such as a spring force F coming from a spring 3 biased washer 4, acting on the O-ring 5. The spring force F acts on the O-ring 5 in addition to the pressure applied in the groove, e.g. by the fluid flowing through the valve and entering the groove from the pipe line side and/or from the bleed area K surrounding the ball valve element L.

Fig. 3 shows a graphical indication of the situation in fig. 2 indicating the distribution of force F between reaction points R _f in the groove and in the O-ring. From figs. 2-3 it is clear that a in a conventional groove the force F acting on the O-ring 5 is divided into three sealing points where the O-ring 5 is in contact with the parallel surfaces 7, 8 and the end surface 9.

As indicated in fig. 4, the present invention provides a differently formed groove for the gasket, in this case an O-ring. The third surface 10 is provided at an angle a, in the area between one of the parallel surfaces 7 (in the following also called side walls) and the end surface 9, i.e. a shoulder in the groove. Thus, the third surface 10 constitutes a frustoconical surface in the groove having an angle a in relation to the side wall 7, which provides a linear increase in the force acting on the O-ring already 5 as discussed above.

It is preferred that the angle a is 5-50 degrees or preferably 5-45 degrees, because in this interval the necessary force F to be applied on the gasket 5 for obtaining an effective sealing effect, e.g. at test conditions of -60 °C and a pressure of 160 bar, is rela- tively low.

The overall length of the frustoconical surface 10 is preferably smaller than the diameter of the O-ring 5 as indicated in fig. 4, but the present invention will also work with a frustoconical surface 10 having a length which is equal to or larger than the diameter of the O-ring (see fig. 5a).

The present invention will also work in a groove where the frustoconical surface 10 has steep angle a which is above 50 degrees, e.g. 50-75 degrees (see fig. 5b) but this will, according to the formula I above, require an increased force F applied to the gas- ket 5 and thus result in increased production costs, e.g. because of the need for a spring 3 having a significantly increased spring force.

The third surface 5 may also be composed of a number n of frustoconical surfaces 10, 10',10", 10 ⁿ each having an increasing angle ai, a ₂ , a _n in relation to side walls 7,8 at decreasing distances to the end surface 9, whereby the reaction force R _fP (in fig 4, and corresponding to the force Fl in fig. 6), acting on the O-ring 5 in the groove can be increased linearly and in stepwise manner because of the increasing angle a on the frustoconical surfaces 10', 10",10 ⁿ (see fig. 5c). Alternatively, it is possible to provide a non-linearly increasing force Fi and thus an increased sealing effect by constructing the third surface 10 so that the angle a is continuously varied in relation to the essentially parallel first and surfaces 7,8, such as by continuously increasing the angle a in relation to the essentially parallel surface at decreasing distances to the end surface 9 (see fig. 5d) or by increasing continuously the angle a and subsequently decreasing the angle a in relation to the essentially parallel surface at decreasing distances to the end surface (see fig. 5e).

Fig. 7 represents a graphical indication of the situation in fig. 4 indicating the distribu- tion of the force F (e.g. a spring force) between only two reaction points R _fP in the groove and in the O-ring 5. As seen in figs 2-3 the same force F applied to the O-ring 5 the groove with the frustoconical surface 10, the force acting between the O-ring and the side wall 8 and the frustoconical surface 10 is larger, (see calculations provided above) when compared to the forces acting on between the O-ring 5 and the side walls 7, 8 and the end wall 9 in a conventional groove (figs. 2-3).

Fig. 8 shows the O-ring 5 in the groove arranged between the inner surface 1 of the valve housing E surrounding the rear surface 2 (in relation to the valve seat) of the backup ring G of a moveable valve seat in the ball valve (position A in fig. 1), where the O-ring 5 will provide an effective sealing effect under dynamic conditions. A similar construction is applicable between two parts of a valve housing El, E2, e.g. at a position D in fig. 1 (where the O-ring 5 will provide a sealing effect under static conditions). The frustoconical surface 10 is arranged between the side wall 8 and a first end wall 9 of the groove provided on rear side 2 of the backup ring G. The other side wall 7 of the groove and a second end wall 11 of the groove is provided by means of a shoulder 11 in the inner surface 1 of the valve housing E. A spring 3 rests against the second end wall 11 and pushes a washer 4 against the O-ring 5, whereby the O-ring is pushed towards the opposite end surface 9 and thus climbs up the frustoconical surface 9 as described above.

Figs. 9 and 10 show variants in which two O-rings are provided in the groove and where both O-rings are energised for providing an increased sealing effect. In fig. 9 the groove is identical to the groove shown in fig. 4 except that a second frus- toconical surface 10" is also provided between the side wall 7 and the second end wall 11 " in the inner surface lof the valve housing E. A second O-ring 5" is provided in addition to the first O-ring 5', and a spring 3 is arranged between two washers 4', 4" which act against an O-ring 5', 5" each. The spring 3 acts in addition to the pressure applied in the groove and provides a double piston effect condition. In this version, the sealing works differently in two stages: Normal stage and Cold stage. The normal stage is when the O-rings 5', 5" have the ability to seal without additional force from the spring 3. Thus, in the Normal stage the spring 3 is only assisting in keeping each of the O-rings 5', 5" tight against their respective side walls 7, 8 and frustoconical surfaces 10, 10". If the pressure applied in the groove comes from the left side of the groove at fig. 9 during Normal stage, the O-ring 5" will be pushed towards the opposite end wall 9, but the sealing effect is maintained because the O- ring 5" is tight against the inner walls 7, 8 of the groove and thus ensures a sealing effect in the groove. In cases where the temperature will be very low (cold stage, i.e. the lower end of the temperature ranges indicated above), and where the pressure in the groove is applied from the left side in fig. 9, the O-ring 5" will be pushed towards the opposite end wall 9, and leak, because the low temperature results in the left O- ring becoming brittle and shrinks. However, the other O-ring 5' at the right side will maintain tightness in the groove because of the additional force coming from the spring, whereby the right O-ring 5' will climb up the frustoconical surface 10'. The same conditions, but in reverse direction, will be present when the pressure in the groove is applied from the opposite side in fig. 9, i.e. from the bleed area K in the ball valve.

In fig. 10, each set of O-rings 5', 5" with spring 3', 3" biased washers 4', 4" are in principle two separate applications similar to the solution shown in fig. 4, where the spring 3', 3" biased washers 4', 4" acting on their respective O-ring 5', 5" are working in opposite directions, and thus provide a solution, a similar effect as the sealing solution shown in fig. 9. The solution shown in fig. 10 in principle comprises two separate, but interconnected grooves, where the inner circumference 1 of the valve housing E is provided with two shoulders, i.e. a first shoulder 11 ' providing the second end wall 11 ' in the first groove and a second shoulder 9' which constitutes the end wall in the second 9" groove. Similarly, the rear surface 2 of the backup ring of the valve seat G is provided with two shoulders i.e. a first shoulder 11 " providing the second end wall 11 " in the second groove and a second shoulder 9' which constitutes another end wall 9' in the first groove. A first frustoconical surface 10' is provided in the first groove between the side wall 7' and the end wall 9' and a second frustoconi- cal surface 10" is provided in the second groove between the side wall 8" and the end wall 9".

When the pressure is applied to the groove from the left side, the left O-ring 5' provides a sealing effect against the side wall 8 and the first frustoconical surface 10' . When the pressure in the groove is applied from the right side the right O-ring 5" provides a sealing effect against the side wall 7 and the second frustoconical surface 10" .

Fig. 11 illustrates the sealing solution according to the present invention when applied for sealing the stem area (position B in fig. 1) between the stem H and the stem guide I under dynamic conditions and/or for sealing the between stem J in the trunnion mount and the valve housing E (position C in fig. 1) under dynamic conditions. The solutions applied in these two positions are essentially identical, except that in position B, the stem H is rotatable in the stem guide I whereas in position C, the stem J is stationary in the trunnion mount. The stem H, J comprises a shoulder 9, which provides an end wall 9 in the groove in the outer circumference 2 thereof. Between this end wall and the side wall 7 a frustoconical surface 10 is provided as described above. The inner circumference 1 of the stem guide I (or the valve housing E respectively) is likewise provided with a shoulder 11 forming the other end wall 11 of the groove. The O-ring and the energising element providing the force F on the O-ring is arranged in the groove as described above, e.g. in relation to fig. 4.

Fig. 12 illustrates an alternative of the present invention, in which the element applying the force F to the O-ring 5, 5', 5" is a lip seal 3a, which acts in cooperation with the pressure applied in the groove, optionally in combination with at washer 4 applied between the lip seal 3a and the O-ring 5, 5', 5" as discussed above. The lipseal 3a can act as a sealing element when tight. Then the pressure applied from the left side in the groove will push the lip seal 3 a towards the end wall 9 which acts in cooperation with the pressure applied in the groove, optionally in combination with a washer 4 applied between the lip seal 3a and the O-ring 5,5',5"as discussed above. In addition, the lip seal 3a can act as a flow reducer, in cases where it leaks especially during a cold stage. When the lip seal 3a becomes a flow reducer it also generates a force F to the O-ring due to the flow which is stopped by the lip seal 3a.

Fig. 13 illustrates yet another alternative in which the element applying the force F to the O-ring 5, 5', 5" is a number of additional O-rings 3b, which acts in cooperation with the pressure applied in the groove, optionally in combination with a washer 4 applied between the O-rings 3b and the O-ring 5, 5', 5" as discussed above. In this situation, the additional O-rings 3b also act as flow reducers, when they leak (i.e. during a cold stage) and thus applies a certain pressure, resulting in a force F to the main sealing element, the O-ring 5. In addition, during a normal temperature stage, when the additional O-rings 3b are tight, the pressure will push the additional O-rings 3b and the optional washer 4 towards the end wall 9 and apply a pressure resulting in an additional force F to the main sealing element, the O-ring 5.

Although the principle of the invention as described above is explained with reference to a ball valve, in particular a ball valve having a trunnion mount, it is clear to the skilled person that the principle in energizing the gasket for providing an effective sealing effect will also be applicable in other types of valves or even in other types of apparatus, e.g. in connections between segments of a pipe line. The only requirement is that there is a possibility for providing the relevant force to the gasket/O-ring, either by applying the necessary spring force or by applying the force by means of the pressure acting in the groove, so that the gasket/O-ring is pressed against the third angled surface, whereby it becomes wedged between the third surface and the first or second parallel surface and optionally also against the end surface.