Double seat valve

A double seat valve comprising a valve housing, a first closing element, a second closing element, a leakage chamber arranged intermediate the first and second closing elements, the second closing element connected to the second displacement rod via spokes, wherein at least one of the spokes comprises: a leading edge that faces the leakage chamber and extends in a radial direction outwards from the second displacement rod; and first and second sides that extend from the leading edge in a direction from the leakage chamber to the drain passage on a respective side of the spoke.

CROSS-REFERENCE TO RELATED APPLICATIONS

The invention is related to European Patent Application No. 13173317.2, filed on Jun. 21, 2013, which is incorporated herein by reference.

TECHNICAL FIELD

The invention relates to a double seat valve that has a first and a second closing element that can be moved into sealing abutment with a respective valve seat. The second closing element is connected to a displacement rod via spokes that extend radially outwards from the second displacement rod to the second closing element, such that interspaces are formed between the spokes for allowing fluid to flow from a leakage chamber and into a drain passage.

BACKGROUND ART

The so called double seat valve is a special type of valve with a valve housing that has first and second valve seats and first and second pipe sections, where the first valve seat may seal against the first pipe section and the second valve seat may seal against the second pipe section. A first closing element, or valve disk, is connected to a first displacement rod for moving the first closing element into sealing abutment with the first valve seat. A second closing element, or valve disk, is connected to a second displacement rod for moving the second closing element into sealing abutment with the second valve seat.

The closing elements and the displacements rods are coaxially arranged and the first displacement rod is typically hollow (tube shaped) such that the second displacement rod can move in an axial direction within the hollow space in the first displacement rod. The valve typically incorporates one or more actuator that effects movement of the displacement rods and thus movement of the closing elements.

The valve seats are coaxially arranged and the closing members face each other. A leakage chamber is arranged between the first and the second closing elements. When the valve is closed the leakage chamber is sealed towards the pipe sections of the valve housing. However, if the sealings are not tight, fluid may enter the leakage chamber from the pipe sections. Such leaked fluid then leaves the leakage chamber via a drain passage that leads fluid from the leakage chamber and to an outlet where the leaked fluid is collected.

For one type of double seat valves the second closing element is ring- or tube-shaped and is connected to the second displacement rod via spokes. The drain passage then extends from the second closing elements ring or tube and out through the valve hosing, such that fluid may pass from the leakage chamber, past the spokes trough interspaces between the spokes and to the drain passage.

The double seat valve has a number of positions for different operation states. For example, in a closed position both valve seats are sealed by the closing elements and no fluid may flow between the two pipe sections.

In an open position both closing elements are lifted from the valve seats such that fluid may flow between the pipe sections.

In a first cleaning position the first closing element is lifted a short distance from its valve seat (the first valve seat) and cleaning fluid that is passed through the first pipe section can then flow also past the first valve seat, into the leakage chamber and thereafter out through the drain passage. This accomplishes cleaning of the first pipe section, the first valve seat and the leakage chamber.

Often the valve has a second cleaning position in which the second closing element is lifted a short distance from its valve seat (the second valve seat). Cleaning fluid that is passed through the second pipe section then flows also past the second valve seat, into the leakage chamber and thereafter out through the drain passage, which effects cleaning of the second pipe section, the second valve seat and the leakage chamber. The cleaning in one or more cleaning positions is done for hygienic reasons and is normally done in an automatic manner at predetermined time intervals and for predetermined periods of time.

Cleaning may be referred to as seat lift of seat push, depending on what direction the closing element is moved when the cleaning is initiated.

Double seat valves of the type described above, including their actuators and the different operation states, are described in the prior art, such as in patent documents U.S. Pat. Nos. 6,047,730, 7,891,376, 8,336,572 and US2010/0051115. They are also commercially available and sold by e.g. Alfa Laval under the product group name “Mixproof Valve”.

It is important that the cleaning is done as efficient as possible and that cleaning fluid in the leakage chamber is effectively led to the drain passage. All parts that has been in contact with any fluid must typically be cleaned, which includes e.g. the leakage chamber, closing elements, displacement rods, spokes, seats, drain passage, relevant gaskets etc.

Most prior art double seat valves are able to clean those parts that must be cleaned. However, there is still a need to improve cleaning, in particular for reducing the cleaning time as well as for reducing the amount of cleaning liquid required for obtaining proper cleaning. Also, during cleaning, there are sometimes problems with pressure build-up in the leakage chamber and/or with backsplash in form of liquid that hits the opposite closing element. It might even be desirable to secure that no positive pressure can occur on a sealing that is arranged on the closing element that is opposite to the closing element that is in a seat lift or a seat push mode.

SUMMARY

It is an object of the invention to at least partly overcome one or more of the above-identified limitations of the prior art. In particular, it is an object to provide a double seat valve that may be more efficiently cleaned while simultaneously reducing or even eliminating pressure build-up in the leakage chamber and/or backsplash to the opposite sealing.

To fulfill these objects a double seat valve is provided, which comprises a valve housing having a first valve seat and a second valve seat, a first closing element and a first displacement rod that is connected to the first closing element for moving the first closing element into sealing abutment with the first valve seat, a second closing element and a second displacement rod that is connected to the second closing element for moving the second closing element into sealing abutment with the second valve seat, and a leakage chamber arranged intermediate the first and second closing elements. The closing elements can be lifted independently of one another from their sealing abutment with the respective valve seat, and the second closing element is connected to the second displacement rod via spokes that extend radially outwards from the second displacement rod to the second closing element, such that interspaces are formed between the spokes for allowing fluid to flow from the leakage chamber and into a drain passage. At least one of the spokes comprises a leading edge that faces the leakage chamber and extends in a radial direction outwards from the second displacement rod, a first side that extends from the leading edge in a direction from the leakage chamber to the drain passage, and a second side that extends from the leading edge in the direction from the leakage chamber to the drain passage.

The leading edge may be compared with a leading edge of an airplane wing. Thus, the leading edge is the part of the spoke that first contacts the fluid, and/or is, as seen in a flow direction, the foremost edge or part of the spoke. The spoke is typically symmetrical and have thus properties that are similar to those of a symmetrical airplane wing.

The spoke with the leading edge provides several advantages. For example, it assists in reducing or even preventing a pressure-build up in the leakage chamber during cleaning. The leading edge may even assist in providing a vacuum, typically in cooperation with other, below described features of the spoke. The leading edge also assists in reflecting fluid in a direction away from the leakage chamber, i.e. in a direction towards the drain passage. As a result the double seat valve and in particular the leakage chamber, the second closing element and the drain passage are more efficiently cleaned while pressure build-up and backsplash may be avoided.

The spoke may comprise, as seen in the direction from the leakage chamber to the drain passage, a first cross-section and a second cross-section, wherein the second cross-section is wider than the first cross-section. These cross-sections are features that further emphasize the structure and the function of the leading edge.

The spoke may comprise a trailing edge. The trailing edge may be compared with a trailing edge of an airplane wing. Thus, the trailing edge is the part of the spoke that last contacts the fluid, and/or is, as seen in a flow direction, the lastmost edge or part of the spoke.

The spoke may comprise, as seen in the direction from the leakage chamber to the drain passage, the first cross-section, the second cross-section and a third cross-section, wherein the second cross-section is wider than the third cross-section. The third cross-section represents a feature that further emphasizes the structure and the function of the trailing edge.

The leading edge may comprise a sharp edge. The trailing edge may also comprise a sharp edge. The sharp edge on the leading edge is advantageous in that it directs the liquid towards the drain passage and reduces or even eliminates backsplash from the spoke. The sharp edge on the trailing edge is advantageous in that it reduces shadow areas where there is no or a reduced flow of cleaning fluid.

The first side and the second side may be continuously curved and may extend from the leading edge to the trailing edge, on a respective side of the spoke. This is advantageous since it reduces drag around the spoke and thus a pressure build-up in the leakage chamber.

The double seat valve may comprise a number of spokes that has trailing edges that meet in a trailing tip. The trailing tip typically shares the same advantages as the sharp edge at the trailing edge, i.e. it reduces shadow areas that are not subjected to or inadequately subjected to cleaning fluid.

In one embodiment the leading edge may extend along the full length of the spoke. In another embodiment the spoke may comprise an abutment member that is located adjacent the leading edge and arranged to abut the first closing element when the closing elements are lifted from the valve seats. The abutment member eliminates the need for the second closing member to abut the first closing member when the closing elements are lifted from the valve seats. This is in turn advantageous since it provides for a more free design of the second closing element.

The abutment member may be located between the leading edge and a peripheral edge of the second closing element, and the spoke may comprise a further leading edge that is located between the abutment member and the peripheral edge of the second closing element.

The second closing element may comprise the drain passage and wherein an inner surface of the second closing element and an inner surface of the drain passage together form either: a continuously curved surface that narrows in the direction from the leakage chamber to the drain passage; or a surface of two or more flat or curved surface segments that narrows in the direction from the leakage chamber to the drain passage. In another embodiment the second closing element may comprise the drain passage and an inner surface of the second closing element and an inner surface of the drain passage may together form a trumpet-shaped surface.

Such surfaces are advantageous in that they may provide a venturi-like effect that secures that there is no pressure build-up in the leakage chamber. The surfaces may even contribute to lowering the pressure in the leakage chamber by providing higher velocity of liquid that leaves the leakage chamber. They also provide for using relatively small dimensions for the drain passage, which it turns reduces the size of the valve housing.

The second closing element may comprise a peripheral edge and an inner surface that extends from the peripheral edge in the direction from the leakage chamber to the drain passage. This means that the second closing member does not have any flat, upper rim that faces the first closing member. This is advantageous since the pressure build-up in the leakage chamber may be reduced during cleaning.

L1may be 2.8 to 3.4 times larger than L2, where L1is the diameter of a peripheral surface of the second closing element and D2is the inner diameter of the drain passage, and L1may be 1.6 to 2 times larger than L3, where L3is the axial distance between the diameters L1and L2.

The features above all, either directly or indirectly, contributing to a double seat valve where pressure build-up and backsplash in the leakage chamber is prevented while efficient cleaning is still obtained. In brief, the shape of the inner surfaces of the second closing element and the drain passage provides for a waterfall effect that allows liquid to flow by as well as a venture-like effect that reduces pressure build-up in the leakage chamber. The leading edge and trailing edge each provides for an airwing-like design that reduces drag from the spoke and thus a pressure build-up in the leakage chamber. The sharp edge on the leading edge reduces backsplash while the sharp edge on the trailing edge and the trailing tip reduces shadow areas, i.e. areas that are difficult to clean. It is actually possible, by using one or more of the described features, to obtain a negative pressure in the leakage chamber during cleaning, which secures liquid exchange and thereby rinsing. Still the cleaning per se is efficiently accomplished.

Still other objectives, features, aspects and advantages of the invention will appear from the following detailed description as well as from the drawings.

DETAILED DESCRIPTION

With reference toFIG. 1a double seat valve2is illustrated. The double seat valve2has a valve housing3with a first pipe section14and a second pipe section15. The pipe sections14,15are joined to each other via an intermediate housing part13. The intermediate housing part13forms a passage between the first pipe section14and the second pipe section15. A first valve seat4is arranged at an end of the intermediate housing part13that is closest to the first pipe section14while a second valve seat5is arranged at an end of the intermediate housing part13that is closest to the second pipe section15.

An actuator16is connected to the valve housing3, on the first pipe section14at a position on the first pipe section14that is opposite the intermediate housing part13. A first displacement rod12extends along a main axis A of the valve2, from the valve housing3, through an upper valve bonnet17and into the first pipe section14. At an end of the first displacement rod12a first closing element11is arranged. The first closing element11has the form of a disk with a central through hole. The first displacement rod12has an axial through hole.

A second displacement rod22extends coaxially with the first displacement rod12, from the actuator16, through the axial hole in the first displacement rod12, through the central hole in the first closing element11and through the intermediate housing part13. At an end of the second displacement rod22a second closing element21is arranged. The second closing element21has the form of a ring or tube and is attached to the second displacement rod22via spokes23that extend radially outwards, from the second displacement rod22to the second closing element21, thereby forming interspaces between the spokes23which allows fluid to flow past the spokes23. In the shown embodiment four spokes23-26(seeFIG. 6) attach the second closing element21to the second displacement rod22and four interspaces27-30are located between the spokes23-26. The spokes23-26may be referred to as traverses or connection pieces. The spokes23-26are located at substantially the same axial distance from the actuator16as the second closing element21.

The main axis A is the axis along which the first displacement rod12second displacement rod22extend. The first and second displacement rods12,22are symmetrical about the main axis A and are movable, or displaceable, in a direction that is parallel to the main axis A.

A drain passage7extends from the second closing element21, through the second pipe section15, through a lower valve bonnet18and to the outside of the valve housing3.

The first closing element11and the second closing element21face each other and a leakage chamber6is located intermediate the first and second closing elements11,21. The boundaries of the leakage chamber6are defined by the surface of the first closing element11that faces the second closing element21, by the surface of the second closing element21that faces the first closing element11and by an inner, circular surface of the intermediate housing part13. Fluid in the leakage chamber6may flow past the spokes23, into the drain passage7and further out from the drain passage7through a drain opening.

The displacement rods12,22, the closing elements11,21, the seats4,5and the drain passage7typically have circular shapes and are symmetrical about the main axis A. The drain passage7has a balance cylinder19at a position of the drain passage7where the drain passage7extends through the lower valve bonnet18.

The double seat valve2is inFIG. 1in its closed position. The closed position is illustrated in larger detail byFIG. 2, where the first closing element11sealingly abuts the first valve seat4and where the second closing element21sealingly abuts the second valve seat5. Each of the closing elements11,21has a respective annular groove for a gasket that assists in obtaining a proper seal against the respective valve seat4,5. The closing elements11,21are held in their respective position by the actuator16. In the closed position no fluid may flow between the first pipe section14and the second pipe section15. If some fluid would leak past the valve seats4,5the leaked fluid would then enter the leakage chamber6and leave the leakage chamber6by flowing past the spokes23and into the drain passage7.

With further reference toFIG. 3the double seat valve2is set in a first cleaning position or performs a so called upper seat lift. In this position the actuator16lifts the first closing element11a short distance from the first valve seat4, such that there is a small passage between the first closing element11and the first valve seat4. The second closing element21abuts the second valve seat5. This allows cleaning fluid that flows in the first pipe section14to enter the leakage chamber6via the passage, which effectively cleans a periphery of the first closing element11including any gaskets on the first closing element11, cleans the first valve seat4and cleans the leakage chamber6as well as the drain passage7. Fluid that accomplishes this cleaning basically follows a first flow path F1.

With further reference toFIG. 4the double seat valve2is set in a second cleaning position or performs a so called seat push. In this position the actuator16pushes second closing element21a short distance from the first valve seat4, such that there is a small passage between the second closing element21and the second valve seat5. The first closing element11abuts the first valve seat4. This allows cleaning fluid that flows in the second pipe section15to enter the leakage chamber6via the passage, which effectively cleans a periphery of the second closing element21including any gaskets on the second closing element21, cleans the second valve seat5and cleans the leakage chamber6as well as the drain passage7. Fluid that accomplishes this cleaning basically follows a second flow path F2.

The double seat valve2may also be set in an open position (not illustrated). In this position the actuator16lifts both the first closing element11and the second closing element21in a direction towards the actuator16, such that fluid may flow between the first pipe section14and the second pipe section15.

How to set the double seat valve2in the above described positions is well known from the prior art and the actuator16may be implemented according to known techniques and methods.

With further reference toFIGS. 5 and 6the spokes23-26are similar and are symmetrically arranged around the second displacement rod22. Using a first spoke23of the spokes23-26as an illustrating example, the spoke23has a leading edge41that faces the leakage chamber6and extends in a radial direction outwards from the second displacement rod22. The radial direction is indicated by direction D2. The spoke23also extends in an axial direction D1, i.e. the spoke23has an axial extension. The axial direction D1may also be seen as being a direction from the leakage chamber6to the drain passage7. A direction from the leakage chamber6to the drain passage7is also indicated by D3.

That the spoke23extends in a radial direction means that it has a radial extension. It must not necessarily extend in a direction that is parallel to a radial direction, since it may be slanted either upwards against the second displacement rod22or slanted in the other direction (downwards against the second displacement rod22).

With further reference toFIG. 10, which shows a cross section of the spoke23, the spoke23has a trailing edge44. A first side42of the spoke23extends from the leading edge41in the direction D3from the leakage chamber6to the drain passage7. A second side43of the spoke23also extends from the leading edge41in the direction from the leakage chamber6to the drain passage7. The sides42,43of the spoke23may also be said to extend from the leading edge41and in the axial direction D1.

The trailing edge44is opposite the leading edge41. The sides42,43extend from the leading edge41to the trailing edge44. The leading edge41has at an uppermost location a sharp edge45and the trailing edge44has at a downmost position a sharp edge46. For the illustrated double seat valve2, “uppermost” and “upper” indicate that an object is located closer to the actuator16than an object that is referred to as “downmost” or as “lower”. “Outmost” and “outer” indicate that an object is located further from the center axis A than on object that is referred to as “innermost” or as “inner”. Uppermost may mean closest to the actuator, downmost may mean most distant from the actuator, innermost may mean closest to the center axis A and outmost may mean most distant from the center axis A.

The first side42has a curved surface42′ and the second side43has a curved surface43′. The first side42and the second side43are continuously curved and extend from the leading edge41to the trailing edge44, on a respective side of the spoke23. The curved surface42′ of the first side42has a curvature that comprises a number of tangents, such as three (3), ten (10) or even more tangents, that are inclined by a respective angle towards the main axis A. Two such tangents are illustrated; tangent t1that is inclined by angle al and tangent t2that is inclined by angle a2. The curved surface43′ of the second side43also has a curvature that comprises a number of tangents, such as three (3), ten (10) or even more tangents, that are inclined by a respective angle towards the main axis A.

In this context, a “tangent” refers to a conventional tangent as defined by and used in common geometry. A “curved surface”, such as the curved surfaces indicated by reference numerals42′ and43′, may refer to a non-straight or non-plane surface.

With further reference toFIG. 11, the spoke23has, as seen in the direction D1, D3from the leakage chamber6to the drain passage7and in said order, a first cross-section55, a second cross-section56and a third cross-section57, where the second cross-section56is wider than both the first cross-section55and the third cross-section57. The cross-sections55,56and57may each be referred to as a respective width or thickness of the spoke23. The cross-sections55,56,57are seen in direction that is parallel with a direction from the second displacement rod22to the second closing element21, i.e. along the spokes23extension from the second displacement rod22to the second closing element21.

As may be seen form the figures, the first side42and the second side43are each continuously curved and extend from the leading edge41to the trailing edge44, on a respective side of the spoke23. The leading edge41may be seen as a part or a section51of the spoke23that first contacts the fluid, and/or is, as seen in a flow direction from the leakage chamber6to the drain passage7, the foremost edge or part of the spoke23. The trailing edge44may be seen as a part or section54of the spoke23that last contacts the fluid, and/or is, as seen in a flow direction from the leakage chamber6to the drain passage7, the lastmost edge or part of the spoke23. Between the leading edge41and the trailing edge44the spoke23has a midsection53that forms the thickest section of the spoke23.

Turning back toFIG. 5the double seat valve2has four spokes23-26. The spokes are symmetrically arranged and are in the illustrated embodiment identical. Each of the spokes23-26has a respective trailing edge46,71,72and the trailing edges46,71,72extend from the second closing element21to the central axis A where they meet in a trailing tip74.

The leading edge41may extend along the full length of the spoke23, from the second closing element21to the second displacement rod22. However and with further reference toFIG. 7, the spoke, here exemplified by spoke24, may comprise an abutment member61that is located adjacent the leading edge62and arranged to abut the first closing element11when the closing elements11,21are lifted from the valve seats4,5, i.e. when the valve2is in the open position. This abutment is implemented for allowing the second closing element21to assist in lifting of the first closing element11. Traditionally, an upper, radially flat and circular rim of the second closing element21was used for assisting in lifting the first closing element11when opening the valve.

The spoke24has a further leading edge63that is located between the abutment member61and a peripheral edge37of the second closing element21. The abutment member61is located between the leading edge62and the peripheral edge37of the second closing element21.

As may be seen on e.g.FIGS. 6 and 7, the peripheral edge37of the second closing element21is, as seen in a radial direction of the second closing element21, an outermost and uppermost edge of the second closing element21. Of all outer surfaces of the second closing element21a peripheral surface10is the most upper one and terminates at an uppermost edge37. An inner surface31of the second closing element21extends from the edge37in the direction D1, D3from the leakage chamber6to the drain passage7. This means that there is no flat surface that extends from the peripheral edge37in a direction that is parallel to a radial direction of the second closing element21. Instead it may be said that the second closing element21has an, upper, peripheral sharp edge. An angle between the peripheral surface10and the inner surface31that extends from the peripheral edge37is smaller than 90°.

Turning back toFIG. 1, it may be said the second closing element21comprises the drain passage7. An inner surface8of the second closing element21and an inner surface9of the drain passage7together form a continuously curved surface8,9that narrows in the direction D1, D3from the leakage chamber6to the drain passage7. It may be said that the inner surfaces8,9together form a trumpet-shaped surface8,9. Alternatively, the inner surfaces8,9may have one or more flat or curved surface segments that narrow in the direction D1, D3from the leakage chamber6to the drain passage7.

The second closing element21and the drain passage7may be given some predetermined measurements. For example, L1may be 2.8 to 3.4 times larger than L2, where L1is the diameter of the peripheral surface10of the second closing element21and L2is an inner diameter of the drain passage7. L1may be 1.6 to 2 times larger than L3, where L3is the axial distance between the diameters L1and L2. With reference toFIG. 12the spoke23a leading edge41and/or trailing edge44that is rounded. This gives the spoke23a cross-sectional shape that is identical with a symmetrical airplane wing.

With reference toFIG. 13the sides42,43of the spoke23may have straight surfaces segments that extend from the leading edge41to the trailing edge44. At least two straight surfaces segments are required.

With reference toFIG. 14the spoke23may be embodied without a trailing edge. In this case the spoke23has a flat surface49that connects the sides42,43. The various embodiments of leading edges, trailing edges and sides shown inFIGS. 10 and 12-14may be combined to form new embodiments of spokes.

The leading edge41may be defined as a part of the spoke23that forms an edge part that has a smaller width or cross-section than a section of the spoke23that is, as seen in the direction D1, D3, located after the leading edge41. The trailing edge44may be defined as a part of the spoke23that forms an edge part that has a smaller width or cross-section than a section of the spoke23that is, as seen in the direction D1, D3, located before the leading edge41.

With reference toFIGS. 8 and 9another embodiment of the spokes is illustrated. Each spoke, such as spoke24, has a leading edge41, a trailing edge44and a midsection53that is located intermediate the leading edge41and the trailing edge44and that is wider than both the leading edge41and the trailing edge44. The leading edge41has a very small, flat edge.

From the description above follows that, although various embodiments of the invention have been described and shown, the invention is not restricted thereto, but may also be embodied in other ways within the scope of the subject-matter defined in the following claims.