TECHNICAL FIELD

The present invention relates to a ball valve assembly comprising a valve housing, a valve seat which is arranged in the valve housing and has one or more through openings, and a ball member which is rotatably arranged in the valve housing.

BACKGROUND OF THE INVENTION

Ball valve assemblies comprising a valve seat with a through opening and a rotatable spherical member provided with a groove are previously known. Such ball valve assemblies can be used for controlling the flow of a liquid in an industrial process.

Valve seats for such ball valve assemblies can be made of hard materials such as for example steel, but it has been found that hard materials do not give an entirely satisfactory result for applications where high demands are placed on tightness and that the demand for tightness in some applications is simply higher than what hard materials can handle. Therefore, valve seats of soft materials, such as polymer materials, are used when high demands are placed on tightness. However, it has been found that even such ball valve assemblies having valve seats of soft materials can suffer from leakage after some period of use so that liquid leaks through also when the ball valve assembly is in a fully closed position. It is a purpose of the present invention to provide a ball valve assembly which is designed to reduce the risk of leakage.

DESCRIPTION OF THE INVENTION

The ball valve assembly according to the invention comprises a valve housing, a valve seat which is arranged in the valve housing, and a ball member which is rotatably journalled in the valve housing about an axis of rotation so that it can assume different angular positions. The ball member is arranged to interact with the valve seat so that liquid cannot pass through the ball valve assembly when the ball member is in a first angular position, but can pass through the ball valve assembly when the ball member is rotated to an angular position different from the first angular position. The ball member has a surface which, in the first angular position, covers the valve seat completely and is so disposed that, when rotating the ball member from the first angular position, the surface is completely smooth and continuous over the entire area where it covers the valve seat. The valve seat has one or more through openings through which liquid can flow when the ball member is rotated to an angular position different from the first angular position. At least the portion of the valve seat coming into contact with liquid flowing through the ball valve assembly is made of reinforced polytetrafluoroethylene (PTFE).

In advantageous embodiments, the valve seat can be made entirely of reinforced polytetrafluoroethylene.

In embodiments of the invention, at least the portion of the valve seat coming into contact with liquid flowing through the valve assembly is made of

polytetrafluoroethylene (PTFE) reinforced with 5 - 40 percent by volume of glass, preferably 10 - 25 percent by volume of glass.

In other embodiments, at least the portion of the valve seat coming into contact with liquid flowing through the valve assembly can be made of polytetrafluoroethylene (PTFE) reinforced with 5 - 35 percent by volume of carbon, preferably 5 - 25 percent by volume of carbon, and most preferably 10 - 25 percent by volume of carbon. In that case, the carbon preferably consists of pulverized coal/carbon black.

In still other embodiments, at least the portion of the valve seat coming into contact with liquid flowing through the valve assembly can be made of polytetrafluoroethylene (PTFE) reinforced with 5 - 40 percent by volume of graphite, and preferably 5 - 15 percent by volume of graphite.

Embodiments where at least the portion of the valve seat coming into contact with liquid flowing through the valve assembly is made of polytetrafluoroethylene (PTFE) reinforced with steel are also conceivable. In that case, austenitic steel, and preferably austenitic stainless steel, most preferably austenitic acid-resistant stainless steel can be used. Advantageously, also super austenitic, duplex or super duplex steels, or nickel- based steel alloys (steel alloys containing some amount of nickel) can be used. If austenitic steel is used as reinforcement material, it should preferably constitute 10 - 60 percent by weight of the material in the valve seat.

In embodiments of the invention, the valve seat has a flow-through portion with one or more through openings, said flow-through portion being elongated in a direction that is perpendicular to the axis of rotation of the ball member so that rotation of the ball member gradually allows increased flow through the ball valve assembly as the ball member is rotated further away from its first angular position. In some embodiments, the valve seat can have a flow-through portion which has a single through opening that is elongated in a direction that is perpendicular to the axis of rotation of the ball member. In that case, the through opening can have a width that increases in the direction that is perpendicular to the axis of rotation of the ball member or a width that decreases in the direction that is perpendicular to the axis of rotation of the ball member such that the portion of the through opening having the largest width is uncovered only when the ball member is rotated from the first angular position.

In other embodiments, the valve seat has a flow-through portion with a plurality of through openings distributed in the direction that is perpendicular to the axis of rotation of the ball member. In that case, the flow-through portion of the valve seat can comprise one, two, or more rows of through openings running in parallel with each other.

In still other embodiments, the flow-through portion of the valve seat can have a single through opening at an end of the flow-through portion, wherein the valve seat has a groove, said groove facing the smooth surface of the ball member when the valve seat is mounted in the ball valve assembly. In that case, the groove is elongated in a direction that is perpendicular to the axis of rotation of the ball member and has one end at the through opening so that rotation of the ball member from the first angular position results in that liquid can flow through the through opening and in the groove and then pass by the ball member. The groove can have a width that decreases in a direction away from the through opening.

In advantageous embodiments, a spring member can be disposed in the valve housing and arranged to act on the valve seat so that the valve seat is pressed into abutment against a support surface in the valve housing so that the position of the valve seat in the valve housing is fixed. In that case, a cover member can be detachably attached to the valve housing and positioned so that the cover member holds the spring member in place when the cover member is attached to the valve housing. In that case, the cover member is preferably (but not necessarily) arranged so that it is accessible from the outside of the valve assembly and thereby allows removal of cover member and spring member so that the valve seat can be replaced with another valve seat.

The invention also relates to use of the ball valve assembly according to the invention in an industrial process in connection with controlling a flow of, for example, water, steam, petroleum products or chemical substances from the group consisting of chlorine, chlorine dioxide, hypochloride, sodium hydroxide, sodium sulphate, nitric acid, sulphuric acid, hydrogen peroxide, calcium chloride or hydrochloric acid that is allowed to pass through the ball valve assembly. Such a use can also be understood in terms of a method in which a flow of liquid or steam passes through a conduit in an industrial process where the flow is controlled by means of the ball valve according to the invention. It is appreciated that the flow through the ball valve assembly may consist of a mixture of liquid and steam and that liquid and/or steam passing through the ball valve assembly may be a mixture of different substances, for example a mixture of water and nitric acid, a mixture of water and one or more petroleum products, or a mixture of one or more petroleum products and one or more chemical substances.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows a view of a previously known ball valve assembly in a closed position.

Figure 2 shows a cross-section along A- A in Figure 1.

Figure 3 shows a view corresponding to Figure 1 in an open position.

Figure 4a shows a cross-section along A-A in Figure 3.

Figure 4b shows a magnification of a portion of Figure 4a.

Figure 5 is a perspective view, partially in cross-section, of an embodiment of the ball valve assembly according to the invention.

Figure 6 shows a ball member for ball valve assemblies that is common today.

Figure 7 shows a ball member for use in the ball valve assembly according to the invention.

Figure 8 shows, in cross-section, an embodiment of the ball valve assembly according to the invention in a first position, which is a fully closed position.

Figure 9 shows, in cross-section, the same embodiment as Figure 8, but here when the ball valve assembly is in a position that is not fully closed, but allows some flow through of liquid.

Figures 10a - e show a possible embodiment of a valve seat for the ball valve assembly that is shown in Figure 8 and Figure 9.

Figures 1 la - e show a variant of the valve seat that is shown in Figures 10 a - e.

Figures 12a - e show another variant of the valve seat according to Figures 10 a - e.

Figures 13a - e show a variant of the valve seat in which the valve seat has a single elongated opening. Figure 14 shows, in cross-section, a second embodiment of the ball valve assembly according to the invention in a first position, which is a fully closed position.

Figure 15 shows, in cross-section, the same embodiment as Figure 14, but here when the ball valve assembly is in a position that is not fully closed, but allows some flow- through of liquid.

Figures 16 a - e show a possible design of the valve seat for the ball valve assembly that is shown in Figure 14 and Figure 15.

Figures 17a - e show a variant of the valve seat that is shown in Figures 16 a - e.

Figures 18 a - e show still another possible variant of the valve seat that is shown in Figures 16 a - e.

Figures 19 a - e show a valve seat which is different from the valve seat according to Figures 17 a - e mainly in that it exhibits two grooves instead of only one.

Figure 20 shows, in perspective, how the valve seat can be detached from the ball valve assembly.

DETAILED DESCRIPTION OF THE INVENTION

With reference to Figure 1 and Figure 2, a previously known ball valve assembly comprising a ball member 4 and valve seat 3 with a through opening 14 is shown. In Figures 1 and 2, the ball valve assembly is in a fully closed position in which liquid cannot flow through the ball valve assembly since the ball member 4 blocks the through opening 14 of the valve seat 3. As is evident from Figure 1, the ball member 4 has a groove 13 in its surface. In Figure 3 and Figure 4b, the same ball valve assembly is shown in an open position where the ball member 4 has been rotated about an axis so that the groove 13 assumes a position coinciding with the through opening of the valve seat 3. Liquid can then flow through the ball valve assembly through the through opening 3, since the groove 13 then provides a flow-through passage. Usually, the valve seat 3 is in contact with at least one spring member (not shown in Figures 4a and 4b) which presses the valve seat 3 into abutment against a support surface that may be part of a valve housing. The force from the spring member (or spring members) then presses on the valve seat with a force indicated by the arrows F in Figure 4a. When the ball valve assembly remains partially open for a long time, the valve seat 3 may be pressed against the groove 13 of the ball member 4. When the valve seat 3 consists of a relatively soft material, such as, for example, polytetrafluoroethylene (PTFE), the edges of the groove 13 of the ball member 4 may be pressed into the soft material in the valve seat 3 and partially deform the valve seat 3. A portion of the valve seat 3 sinks into the groove 13.

In the present patent application and in any patents that may be granted on the basis of the present application, the term "ball member" shall be construed and understood as an element comprising a segment of a sphere so that a portion of the ball member has a spherical shape, as is evident, for example, from Figure 7, Figure 8 and Figure 9. When the ball valve assembly is in a fully closed position, as is shown, for example, in Figure 8, the surface of the ball member facing the valve seat is a curved surface with a radius of curvature, and the surface facing the valve seat is, in that case, identical to the surface an entirely spherical body with the same radius of curvature would expose towards the valve seat. It is appreciated that the valve seat has a shape that corresponds to/mirrors the shape of the ball member so that the ball member can interact freely with the valve seat.

An encircled area indicated by the reference numeral S is shown in Figure 4a. This area is shown in magnification in Figure 4b. The indentation/incision made by the edges of the groove 13 in the valve seat is indicated by the reference numeral D. When the valve assembly is subsequently closed, the edge of the ball member can shear off a portion of the material that has sunk into the groove 13. In that case, leakage may occur when the valve assembly is closed. The present invention solves this problem in a way described in the following.

Reference is now made to Figure 5, in which a ball valve assembly according to the present invention is shown in perspective and partially in cross-section. The ball valve assembly 1 according to the invention comprises a valve housing 2, a valve seat 3 which is arranged in the valve housing 2, and a ball member 4. The ball member 4 is rotatably journalled in the valve housing 2 about an axis of rotation (rotation axis) R so that it can assume different angular positions. Suitably, the ball member 4 is in that case attached to a rotatable rod A so that rotation of the rod A causes the ball member to rotate about the axis of rotation R. The ball member 4 is arranged to interact with the valve seat 3 so that liquid cannot pass through the ball valve assembly 1 when the ball member 4 is in a first angular position, but can pass through the ball valve assembly 1 when the ball member 4 is rotated to an angular position different from the first angular position. As is evident from Figure 5, a spring member 9 can be arranged to act on the valve seat 3, and the spring member 9 may, for example, consist of a spring washer. In many practical embodiments, a cover member, such as, for example, a cover plate 11, can be attached to the valve housing 2 in such a position that the spring member 9, and thus also the valve seat 3, are held in place. The cover plate 11 can be attached to the valve housing 2, for example, by having threads on its periphery interacting with threads in the valve housing, but the skilled person appreciates that the cover plate 11 can be attached to the valve housing 2 in many other ways, which do not have to be explained in detail. In principle, the cover plate 11 can be attached to the valve housing permanently, for example by welding, but in preferred embodiments, the cover plate 11 is detachably attached (for example by threading) so that the cover plate 11 can easily be removed in connection with, for example, replacement of the valve seat 3, or repairs, maintenance work, and the like.

Now, with reference to Figure 6, a ball member 4 of a type previously known in the technical field is shown. As explained earlier with reference to Figures 1 - 3 and Figure 4a, this ball member 4 has a groove 13 into which the material in a soft valve seat may sink, which can cause damages to the valve seat. Figure 7 instead shows a ball member 4 that is intended to be used in the ball valve assembly according to the invention. This ball member 4 lacks the kind of groove 13 that the ball member in Figure 6 is provided with. Instead, the ball member 4 according to Figure 7 has a smooth surface 5 without grooves. The portion of the ball member 4 that has a smooth surface 5 without grooves is so large that it can be set to cover the valve seat. Thereby, the ball member 4 can be rotated to an angular position where it exposes a surface 5 facing the valve seat 3 that is completely smooth without grooves. The surface 5 on the ball member 4 is so disposed that, when the ball member 4 is mounted in the ball valve assembly 1 and the ball valve assembly 1 is in a closed position, it completely covers the valve seat 3. Furthermore, the surface 5 is so disposed that, when rotating the ball member 4 from the first angular position, it is completely smooth and continuous over the entire area where it covers the valve seat 3. This is the position that the ball member is to assume when the ball valve assembly 1 is fully closed (the first angular position) so that no liquid will be able to pass through the ball valve assembly 1. In the following, the closed position of the ball valve assembly 1 will be designated as "a first position" (first angular position) or "the first position". In order to allow passage of liquid through the ball valve assembly 1, the valve seat 3 instead has one or more through openings through which liquid can flow when the ball member 4 is rotated to an angular position different from the first angular position, as will be explained in greater detail later on in this description.

Accordingly, the entire portion of the ball member 4 that moves over the valve seat 3 has a surface 5 that is completely smooth and continuous and without grooves over the entire area where this surface 5 covers the valve seat 3 (completely or partially). Thus, even when the surface 5 only partially covers the valve seat 3, there is no groove in the surface 5 into which portions of the material in the valve seat could sink.

At least the portion of the valve seat 3 coming into contact with liquid flowing through the ball valve assembly 1 is made of reinforced polytetrafluoroethylene (PTFE).

Preferably, the valve seat 3 is made entirely of reinforced polytetrafluoroethylene, but embodiments where only a portion (or portions) of the valve seat is (are) made of reinforced PTFE are conceivable.

Since the material in the valve seat 3 is reinforced, the structural stability of the material is improved.

In some embodiments, the portion of the valve seat 3 coming into contact with liquid flowing through the ball valve assembly 1 can be made of polytetrafluoroethylene (PTFE) reinforced with 5 - 40 percent by volume of glass, preferably 10 - 25 percent by volume of glass. It is appreciated that the seat can be made entirely of PTFE reinforced with 5 - 40 percent by volume of glass.

In other embodiments, the portion of the valve seat 3 coming into contact with liquid flowing through the ball valve assembly 1 can be made of polytetrafluoroethylene (PTFE) reinforced with 5 - 35 percent by volume of carbon, preferably 5 - 25 percent by volume of carbon, and most preferably 10 - 25 percent by volume of carbon. It is appreciated that the valve seat can be made entirely of PTFE reinforced with 5 - 35 percent by volume of carbon. As used herein, carbon primarily refers to pulverized coal/carbon black, amongst other things, because pulverized coal/carbon black are well suited when it is desirable to bring about a uniform distribution of the carbon in the PTFE material so that uniform material properties are obtained.

Carbon black is a material which is advantageous when low friction is desired.

Glass is a reinforcement material which is advantageous when very cold media will pass through the ball valve assembly, for example, liquid nitrogen. Valve seats with carbon become very brittle at low temperatures and glass is more suitable as reinforcement material in that case.

Also other reinforcement materials than glass or carbon can be used. In some possible embodiments, the valve seat 3, or at least the portion of it coming into contact with liquid flowing through the ball valve assembly 1, can be made of

polytetrafluoroethylene (PTFE) reinforced with 5 - 40 percent by volume of graphite, and preferably 5 - 15 percent by volume of graphite. At present, the applicant has not tested graphite, but there are theoretical reasons to believe that graphite can provide even lower friction that carbon black.

Another conceivable alternative may be to have at least the portion of the valve seat 3 coming into contact with liquid flowing through the ball valve assembly 1 made of polytetrafluoroethylene (PTFE) reinforced with austenitic steel, preferably

polytetrafluoroethylene (PTFE) reinforced with 10 - 60 percent by weight of austenitic steel. It is appreciated that the valve seat 3 can be made entirely of PTFE reinforced with austenitic steel, and that the steel advantageously can be stainless austenitic steel. As used herein, stainless austenitic steel is understood as steel with an austenitic structure containing chromium (12 - 30 percent) and nickel (7 - 30 percent) and other metals, usually molybdenum (2 - 3 percent). As a rule, the carbon content in these steels is relatively low, usually below 0.05 percent.

The steel in the reinforcement material can advantageously also be duplex steel, that is to say ferritic-austenitic steel containing chromium, nickel, molybdenum, carbon and nitrogen. A duplex steel can, for example, contain 22 - 24.9 percent of chromium, 5 - 8 percent of nickel, 1 - 4 percent of molybdenum, below 0.03 percent of carbon (for example 0.01 - 0.029 percent of carbon) and 0.4 percent of nitrogen.

Super duplex steels can also be used for the reinforcement. As used herein, super duplex steels refer to duplex steels with a chromium content of 25 percent or more, for example 29 percent of chromium.

Furthermore, the steel in the reinforcement may also be a super austenitic steel, and advantageously also high nickel-based steel alloys can be used.

Stainless steel as reinforcement has proved to be more resistant to high surface pressures between valve seat and ball member and to fluid media that are more demanding on soft materials e.g. due to high mass concentrations, but, most

importantly, a valve seat with reinforcement of stainless steel can withstand higher temperatures than a reinforcement with carbon black because it is a more stable reinforcement.

A possible embodiment of the ball valve assembly according to the invention will now be explained with reference to Figure 8, Figure 9 and Figures 10 a - e.

Figure 8 shows in cross-section an embodiment of the ball valve assembly according to the invention in which the ball member 4 is in a first angular position. This position of the ball member 4 is a position where the ball valve assembly is closed and liquid cannot flow through the ball valve assembly 1. As is evident from Figure 8, the valve seat 3 has through-holes 8. These through-holes 3 are located in a flow-through portion 6 of the valve seat 3 and, when the ball valve assembly 1 is open, liquid should be able to flow through the through openings 8 in the flow-through portion 6 of the valve seat 3. However, in the position that the ball member 4 assumes in Figure 8, no liquid can flow through the through-holes 8, since the ball member 4 is in a position where the flow through portion 6 is blocked by the ball member 4.

Figure 9 shows the same embodiment as Figure 8, but here the ball member 4 has been rotated about the axis of rotation/rotation axis R so that at least a portion of the flow through portion 6 is no longer blocked by the ball member 4. Liquid can now flow through the through openings 8 in the flow-through portion 6. A flow of liquid is indicated symbolically by the arrow V in Figure 9. As is understood when viewing Figure 9, only a portion of the flow-through portion 6 is uncovered and, accordingly, the ball valve assembly 1 is not in a fully open position. It is appreciated that by varying the angle by which the ball member 4 is rotated about the axis R, it is possible to uncover a larger or smaller portion of the flow-through portion 6 and thereby control the flow of the liquid passing through the ball valve assembly 1.

A possible embodiment of the valve seat 3 is shown in Figures 10 a - e. Figure 10 a is a view from straight above in which the portion of the valve seat 3 facing the ball member 4 when the valve seat is in its place in the ball valve assembly 1 is seen, whereas Figure 10b shows a cross-section along A - A in Figure 10a and Figure 10c shows the cross- section B - B in Figure 10a. Figure lOd shows the valve seat 3 in perspective and Figure lOe shows, in perspective, how the valve seat 3 looks from below, that is to say, from the side facing away from the ball member 4 when the valve seat 3 is in place in the ball valve assembly 1.

As is evident from Figures 10a - e, the flow-through portion 6 of the valve seat 3 has a plurality of through openings 8 and the through openings are placed in a row so that the flow-through portion 6 is elongated in a direction across the valve seat 3. When the valve seat 3 is in place in the ball valve assembly 1, the flow-through portion 6 is elongated in a direction that is perpendicular to the axis of rotation of the ball member 4 so that rotation of the ball member 4 gradually allows increased flow through the ball valve assembly 1 as the ball member 4 is rotated further away from its first angular position. As the ball member 4 is rotated from its first angular position (which is shown in Figure 8) an increasingly larger portion of the flow-through portion 6 will be uncovered so that liquid can flow through. In this way, the flow through the ball valve assembly 1 can be controlled. Figures 11a - lie show a variant of the valve seat according to Figures 10a - lOe. In this embodiment, the flow-through portion 6 has two parallel rows of through openings 8. Another variant, which is shown in Figure 12 a - Figure 12e, is designed with three parallel rows of through openings 8. It is appreciated that similarly there may be more than three rows of through openings 8. It should also be appreciated that the through openings 8 do not necessarily have to be placed in a row and that they do not have to have the same size, shape, or distance to each other. In Figures 10 a - lOe, Figures 11 a - l ie and Figures 12a - 12e, the through openings are circular, have the same size, and are uniformly distributed so that they are placed at the same distance from each other in each row, but embodiments where the through openings have a different shape, for example oval, triangular, or rectangular, are also conceivable. Embodiments where the through openings 8 are unevenly distributed across the flow-through portion 6 are also conceivable. For example, the through openings 8 can be placed at a greater distance from each other at one end of a row so that a smaller increase of the flow through the flow-through portion 6 is obtained during initial opening of the ball valve device than with a corresponding rotation of the ball member 4 at a later stage. Correspondingly, it is conceivable that the size of the through openings 8 increases or decreases from one end of the flow-through portion 6 to the other. However, in all embodiments, the through openings 8 should be designed and positioned so that as the ball member is rotated further and further away from the first angular position (the closed position), more and more liquid will be able flow through the ball valve assembly 1 , which requires that the total area open for flow-through increases.

Reference is now made to Figures 13a - 13e. These figures show another variant of how the valve seat 3 can be designed. The different views according to Figures 13a - 13 e correspond directly to the views according to Figures 10a - lOe, but the valve seat shown here has a single through opening 7 which is designed as a slit extending across the valve seat 3, the through opening 7 is thus elongated. In the embodiment that is shown in Figures 13a - 13e, the through opening (slit) 7 extends such that it passes the centre of the valve seat 3 (in the same way as the row of through openings 8 in the variant according to Figures 10a - lOe). As is evident from the figures, the elongated through opening/slit 7 has a width W that increases in one direction. In this way, it can be achieved that initial rotation of the ball member 4 from the first angular position by a certain number of degrees causes only a small opening to be uncovered in the flow through portion 6, while further rotation of the ball member 4 by the same number of degrees causes a relatively larger opening to become available for flow-through. It is appreciated that the opposite effect can be achieved by instead giving the opening 7 a decreasing width in the same direction. In such a way, the control characteristics of the valve assembly 1 can be chosen according to different needs. It is appreciated that, in the same way as in the variants according to Figures 10a - lOe, Figures 1 la - 1 le and Figures 12a - 12 e, the flow-through portion 6 is elongated in a direction that is perpendicular to the axis of rotation R of the ball member 4 when the seat valve 3 is in place in the ball valve assembly 1. In the embodiment according to Figures 13a - 13e, the through opening 7 is thus elongated in a direction that is perpendicular to the axis of rotation of the ball member 4. Preferably, but not necessarily, the through opening 7 has a width that increases in the direction that is perpendicular to the axis of rotation R of the ball member 4, but embodiments where the through opening 7 of the valve seat 3 has a width that decreases in the direction that is perpendicular to the axis of rotation R of the ball member 4 such that the portion of the through opening 7 having the largest width is uncovered only when the ball member 4 is rotated from the first angular position are also conceivable.

Such variants of the valve seat 3 according to Figures 13a - 13 e where the width W of the through opening 7 is constant over the entire length of the flow-through portion 6 are also conceivable.

The embodiment according to Figures 13a - 13e is slightly different from the variants that are shown in Figures 10a - lOe, Figures 1 la - 1 le and Figures 12a - 12 e, but functions in a substantially similar way and can therefore be regarded as a variant of the embodiment that is shown in Figure 8 and Figure 9.

Another embodiment will now be explained with reference to Figure 14 and Figure 15.

Figure 14 shows the ball valve assembly 1 according to the invention in a closed position, accordingly, the ball member 4 is in the first angular position and blocks flow- through of liquid. As is evident from Figure 14, the valve seat 3 has a single through opening 7 that leads to a groove 12, which, however, cannot allow liquid to pass through since the ball member 4 blocks the way. In Figure 14, it can also be seen how a spring member 9 (for example a spring washer) is disposed in the valve housing 2 and arranged to act on the valve seat 3. Thereby, the valve seat 3 is pressed into abutment against a support surface 10 in the valve housing 2 so that the position of the valve seat 3 in the valve housing 2 is fixed. A cover member 11 is detachably attached to the valve housing 2 and positioned so that the cover member 11 holds the spring member 9 in place when the cover member 11 is attached to the valve housing 2, and the cover member 11 is preferably disposed so that it is accessible from the outside of the ball valve assembly 1 and thereby allows removal of cover member 11 and spring member 9. Thus, amongst other things, the valve seat 3 can be accessed to replace it with another valve seat 3. This may be the case when a valve seat with different control

characteristics is desired, or when a valve seat that has been damaged for some reason needs to be replaced with a new one.

Figure 15 shows how the ball member 4 has been rotated about its rotation axis R so that liquid can flow through the ball valve assembly 1 by passing the groove 12.

Also in the embodiment according to Figure 14 and Figure 15, it applies that the surface 5 of the ball member is so disposed that, when rotating the ball member 4 from the first angular position, it is completely smooth and continuous over the entire area where it covers the valve seat 3. In this way, the risk of wear on the valve seat 3 is reduced.

Now, with reference to Figures 16a - 16e, a possible design of the ball valve assembly 1 according to Figure 14 and Figure 15 will be explained. Figures 16a - 16e show different views of the valve seat 3 in a way corresponding to the views according to Figures 10 a - e. As is evident from the figures, the valve seat 3 in this embodiment has a through opening 7 at one end of the flow-through portion 6. The through opening 7 is located so that it will be uncovered only when the ball member 4 is rotated away from its closed position. However, the through opening 7 is located only at one end of the flow-through-portion 6 and the remaining part of the flow-through portion 6 is constituted by a groove 12 that is formed in the valve seat 3 on the surface facing the ball member 4 when the valve seat 3 is in place in the ball valve assembly 1. Thus, the groove 12 will be facing the smooth surface 5 of the ball member 4 when the valve seat 3 is mounted in the ball valve assembly 1. The groove 12 is elongated in a direction that is perpendicular to the axis of rotation R of the ball member 4 and has an end at the through opening 7 so that rotation of the ball member 4 from the first angular position results in that liquid can flow through the through opening 7 and in the groove 12 and then pass by the ball member 4.

As is shown in Figures 16 a - 16 e, the groove 12 can have width that decreases in a direction away from the through opening 7.

Figures 17a - 17e show a variant of the valve seat 3 that is shown in Figures 16 a - 16e. In the variant that is shown in Figures 17a - 17e, the groove 12 has a width that is substantially constant along the extension of the groove 12, and the groove 12 is also substantially wider than in the variant according to Figures 16 a - 16e. The through opening 7 is also larger than in the variant according to Figures 16 a - 16e and has also been given a more oval shape. It is appreciated that these differences result in different flow characteristics than is the case with the variant according to Figures 16 a - 16e. A further variant is shown in Figures 18a - 18 e. This variant is similar to the one shown in Figures 17a - 17 e, but the through opening 7 has here been given a circularly round shape, and the groove 12 is not as wide.

Another variant is shown in Figures 19a - 19e. In this variant, the groove 12 is tapering in a direction away from the through opening 7, and the groove 12 is divided into two portions, 12a and 12b. The division is achieved by means of an edge 15 extending along the groove 12.

The different variants according to Figures 16a - 16e, Figures 17a - 17e, Figures 18a - 18e, and Figures 19a - 19e function, in principle, in the same way. When the ball member 4 is rotated away from the first position (angular position), liquid can flow in through the through opening 7 and further on in the groove 12, and thus flow between the valve seat 3 and the ball member 4 until the liquid arrives at a point where the valve seat 3 is not covered at all by the ball member 4, and the liquid can then flow on through the ball valve assembly 1. Before the liquid has reached a point where the ball member 4 no longer covers the valve seat 3, the liquid is constrained to flow in the groove 12 and thus cannot take another path. It is appreciated that the design of the groove then becomes important for the flow characteristics/control characteristics of the ball valve assembly 1.

As is shown in Figure 20, the valve seat 3 can be replaced by detaching the cover plate 11, taking away the spring washer 9, and then lifting out the valve seat 3 so that it can be replaced with another valve seat, for example a valve seat with different control characteristics.

Since the ball member 4 exhibits a smooth surface without grooves, wear on the valve seat can be reduced, which, in its turn, reduces the risk of leakage.

The valve seat that is used in the ball valve assembly according to the invention can advantageously be manufactured by means of additive manufacturing, also known as 3D printing. By using additive manufacturing, complex shapes can be manufactured more easily. Methods for additive manufacturing are disclosed in, for example, US patent No. 9,862,140 and US patent No. 9,944,016.

The ball valve assembly according to the invention can advantageously be used in environments where corrosive chemical substances have to pass through the ball valve assembly, and, in that case, the choice of reinforced polytetrafluoroethylene (PTFE) makes the valve seat better to withstand exposure to such chemical substances. The ball valve assembly according to the invention may be particularly suited for use in paper and pulp industries where corrosive chemical substances are used. PTFE also has a low friction coefficient, which is advantageous.

In some cases, the design according to the invention can advantageously also be applied to a ball valve assembly that does not utilize a valve seat of reinforced PTFE, and, in that case, allow a good control of a flow, even though the tightness will not be as good as with a valve seat of reinforced PTFE. This may be the case when the flow which will pass through the ball valve assembly contains hard particles and the ball valve assembly has to meet high demands on wear resistance. For such applications, a ball valve assembly that has a valve seat made of a material with high wear resistance, but which otherwise is designed in accordance with what has been described above with reference to the accompanying figures, can be used. For such applications where high wear resistance is a requirement, the valve seat can be made of a homogenous steel grade or of metal with high content of cobalt. In this context, "homogenous" means that the component is made entirely of one and the same material. Steel grades which are particularly suitable for such applications may comprise austenitic stainless steel, duplex stainless steel or super austenitic stainless steel. A suitable steel grade can for example consist of SS 14 2328, which is a super duplex material that contains 0.030 % of carbon (C), 0.8 % of silicon (Si), 1.2 % of manganese (Mn), 0.035 % of phosphorus (P), 0.020 % of sulphur (S), 24 % - 26 % of chromium (Cr), 6.0 % - 8.0 % of nickel (Ni), 3.5 % - 5.0 % of molybdenum (Mo) and 0.24 % - 0.32 % of nitrogen (N). Such materials have high wear resistance. When very high demands are placed on wear resistance and/or when the fluid passing through the ball valve assembly has a very high temperature, a metal with a high content of cobalt can be used instead of steel. This may be suitable, for example, when the fluid passing through the ball valve assembly has temperature of 400 °C or higher, or when very high demands are placed on wear resistance. In that case, the metal in the valve seat can consist of a material that contains at least 60 % of cobalt and that additionally contains chromium, nickel and

molybdenum. For example, the material can contain 60 - 70 % of cobalt, 20 - 30 % of chromium and 0.5 - 12.0 % of molybdenum, and a certain amount of nickel. Such materials have very high wear resistance, higher than the steel grades specified above, and they can also withstand high temperatures. The applicant reserves the right to file claims also for such ball valve assemblies where the valve seat is made of a steel grade according to what has been stated above, or of a metal with a high content of cobalt according to what has been stated above.

Such a claim that relates to a ball valve assembly where the valve seat does not necessarily comprise reinforced reinforced polytetrafluoroethylene (PTFE) could relate to a ball valve assembly 1 that comprises: a valve housing 2; a valve seat 3 that is arranged in the valve housing 2; a ball member/ball element 4 that is rotatably journalled in the valve housing 2 about an axis of rotation R such that it can assume different angular positions and is arranged to interact with the valve seat 3 such that liquid cannot pass through the ball valve assembly 1 when the ball member 4 is in a first angular position, but can pass through the ball valve assembly 1 when the ball member 4 is rotated to an angular position different from the first angular position. Also in such a claim, the ball member 4 would have a surface 5 which, in the first angular position, covers the valve seat completely and is so disposed that, when rotating the valve member 4 from the first angular position, the surface 5 is completely smooth and continuous over the entire area where it covers the valve seat 3, the valve seat 3 having one or more through openings through which liquid can flow when the ball member 4 is rotated to an angular position different from the first angular position, However, the valve seat 3 would be made either in a homogenous steel grade, or of metal comprising 60 - 70 % cobalt, 20 - 30 % chromium and 0.5 - 12.0 % molybdenum and a certain amount nickel Ni, or, alternatively, so designed that at least the portion of the valve seat

3 coming into contact with liquid flowing through the ball valve assembly 1 is made of reinforced polytetrafluoroethylene (PTFE). Furthermore, such a claim might additionally specify that the valve seat 3 has a flow-through portion 6 that is elongated in a direction that is perpendicular to the axis of rotation R of the ball member 4 such that rotation of the ball member 4 gradually allows increased flow through the ball valve assembly 1 as the ball member 4 is rotated further away from its first angular position, the flow-through portion 6 having a single through opening 7 and the valve seat 3 having a groove 12 which groove faces the smooth surface 5 of the ball member 4 when the valve seat 3 is mounted in the ball valve assembly 1, the groove 12 being elongated in a direction that is perpendicular to the axis of rotation R of the ball member

4 and having one end at the through-opening 7 such that rotation of the ball member 4 from the first angular position results in that liquid can flow through the through- opening 7 and in the groove 12 and then pass the ball member 4.

The invention also encompasses use of the ball valve assembly according to the invention, wherein the ball valve assembly is used in an industrial process where liquid containing chemical substances from the group consisting of chlorine, chlorine dioxide, hypochloride, sodium hydroxide, sodium sulphate, nitric acid, sulphuric acid, hydrogen peroxide, calcium chloride or hydrochloric acid is allowed to pass through the ball valve assembly. Such industrial processes can be found in, for example, paper and pulp industry, but can also be found in other fields, for example where flows of petroleum products have to be handled.