GB2054102A - Floating seat butterfly valve - Google Patents

Abstract

A butterfly valve seat assembly comprises a rigid body (10) with two radially inwardly directed annular ribs, and an annular seat (24) of elastomeric material within which is embedded a flexible metal ring (23). The seat (24) spans the body (10) to define an annular space (12). The seat has two end flanges (27) which are adapted to be clamped between the ribs of the body (10) and the opposing flanges of pipes or the like. The cavity (12) can be used for the circulation of a heating or cooling medium. <IMAGE>

Description

SPECIFICATION Floating seat butterfly valve This invention relates to butterfly valves wherein a valve disc is rotatable in an annular valve body to control the flow of fluid through such annular valve body. The invention is particularly applicable to a butterfly valve of the wafer type wherein the annular valve body is relatively thin, e.e. it is of small dimension in the direction of flow through it, the valve body being intended to be positioned between opposing flanges of pipes or other equipment.

Wafer type butterfly valves are well known in the art. The majority of these valves have a resilient seat so that when the disc is rotated in the valve body it contacts the resilient seat around its circumference and thus seals the valve. It is found that the resilient seat often wears or distorts in the region where it is contacted by the disc, so that under pressure leakage past the seax can occur. In many of the presently known types of butterfly valves, there is no compensation for wear and thus once a resilient seat starts to wear it is necessary to replace the seat.

A typical resilient seat in a butterfly valve is made from a modulated elastomeric material such as a synthetic rubber. Other materials which are wear resistant and capable of withstanding the operating conditions may also be suitable. In most butterfly valves, the seat is generally circular so that the valve disc closes when it is perpendicular to the axis of the passageway through the valve. It is also known for the valve seat to be positioned so that the valve disc is not perpendicular to the axis of the passageway when closed. In most valves, however, there is only one position where the disc contacts the seat to seal the valve effectively.

In most butterfly valves the bore through the annular body is machined to the external diameter of the resilient valve seat in order to accurately locate the resilient valve seat and ensure leak tightness when the valve is closed. If the seat does not sit circumferentially true in the body, the disc does not contact the seat evenly or sufficiently around its circumference. If the contact force between the disc and the seat is too high, a considerable force is needed to open and close the valve and this, in turn, increases the wear of the resilient seat material. If, on the other hand, there is too little impingement between the disc and the seat, leakage can occur even when the valve is fully closed.

Another problem that sometimes occurs with this type of butterfly valve is the permanent distortion of the resilient valve seat due to loading.

This is caused by the cold flow of the resilient material of the valve seat, and results from valve disc contact force or from the clamping of the valve seat between the opposing retaining flanges of the pipes or the like. Distortion of this type can cause a leak between the valve seat and the disc which can only be cured by replacing the resilient valve seat. In present types of valves with perpendicular disc sealing positions, the desired sealing only occurs when the disc is turned to a "90 position" perpendicular to the central axis of the valve body. When the disc is positioned a few degrees off this perpendicular position, it becomes "out-of-round" viewed axially.The resilient material cannot compensate for this apparent out-of-roundness and thus uniform contact around the valve disc is lost Another problem that can occur with butterfly valves of this type is when they are used in vacuum conditions. Under these conditions the resilient valve seat can collapse into the passageway when the disc is opened and restrict the flow through the valve.

The present invention contemplates a novel approach to overcome some of the above problems and others by providing a flexibly located, i.e. floating valve seat having a flexible, ring therein which may be partly deformed but returns to its original shape. When fully assembled in the valve, the seat has a circumferential clearance between its external surface and the bore of the annular valve body. Because of this fiexibly mounted seat arrangement the body bore does not require a machine finish. Furthermore, theflexible ring allows the seat to change its shape and thus take into account a slightly out-ofroundness shape or apparent out-of-roundness of the disc.This ability of the seat to change its cross sectional shape allows the valve disc to contact it evenly its circumference and form a seal when the angle between the plane of the disc seat and the plane perpendicular to the passageway axis is less than about 5 viewed axially. The flexible seat adjusts to become an elliptical ring to comply with the projected elliptical shape of the disc perimeter.

The flexible valve seat permits the disc to relocate the sealing position on the seat when for example wear occurs, or adjustment for leakage is necessary. If the disc seals and closes the valve when the disc is not in the axially perpendicular position, and if wear or leakage subsequently occurs at this particular sealing location, then the disc may be rotated closer to the perpendicular of the passageway axis to a new sealing position.

According to one aspect of the present invention there is provided a butterfly valve assembly adapted to be positioned between opposing flanges of, for example, adjacent pipe ends, the assembly comprising a rigid generally annular valve body defining a fluid flow aperture, a generally annular valve seat located within the annular valve body, and a rotatably mounted valve disc adapted to co-operate with the valve seat to control fluid flow through the valve body, the valve body having an internal generally cylindrical surface carrying a pair o-;; axially spaced apart circumferentially extending annular ribs, the valve seat comprising a hollow cylindrical part encircles by the ribs and made of an elastomeric material, such hollow cylindrical part carrying at each end thereof outwardly directed resilient flanges which overlap the annular ribs, whereby in use of the valve the resilient flanges will be clamped against the ribs to form seals therewith, an annular cavity lying between the ribs and being formed between the said internal generally cylindrical surface of the valve body and the hollow cylindrical part of the valve seat, such hollow cylindrical valve seat part being reinforced by metallic bracing means, for example a metal ring embedded in elastomeric, material the arrangement being such that when the disc is in a closing position in contact with the valve seat it can deform the annular valve seat into tthe space provided by the cavity, the bracing means assisting in returning the valve seat to an undeformed condition when the valve disc is moved away from its closed position. The annular cavity surrounding the flexible valve seat may be used for circulting a heating or cooling medium to contain the temperature of the seat assembly within desired limits. In preferred embodiments the valve assembly stem is connected to the valve disc, the valve stem extending through the centre of the rigid annular valve body, the valve stem having a neck portion with a two way seal therein.

The valve stem may be connected to a handle and a quadrant means mounted above the rigid body, the quadrant means having a series of notches that can be engaged by the handle allowing the valve stem to be rotated and locked positively in a number of positions. In another embodiment the quadrant means has at least one stop pin located in any one of a series of holes equispaced about a radial arc in the quadrant to position the disc in a partially closed position and reduce rotary movement of the disc.

According to another aspect of the invention there is provided a butterfly valve assembly adapted for positioning between opposing, spaced-apart flanges in a fluid flow system, said assembly comprising: A. a rigid body having opposing external flat parallel end surfaces adapted to mate with the opposing flanges, said body having opposing internal end surfaces spaced inwards from and having a smaller diameter than said external end surfaces, said body adapted to permit fluid flow therethrough and to accept a valve closure member; B. a valve closure member rotatably mounted within said body and adapted to cooperate with a seat assembly to regulate fluid flow through said rigid body; C. a seat assembly adapted to co-operate with said valve closure member between an open position and a closed position, said seat assembly comprising:: i. a flexible ring disposed in said rigid body for resilient flexible engagement with an annular seat and, ii. an annular seat disposed in said rigid body supporting said flexible ring, said seat assembly and said rigid body defining an annular space therebetween adapted for the passage of a fluid medium therethrough, said seat assembly having an external flange on each end adapted to be clamped between its respective internal end surface and one of the opposing flanges; and, D. an inlet connector and an outlet connector communicating with the annular space and adapted to receive and pass a fluid medium therethrough, whereby rotation of said valve closure member to a closed position forces said seat assembly to deform into the annular space and simultaneously permits fluid to pass from said inlet connector through the annular space to said outlet connector.

In drawings which illustrate embodiments of the invention; Figure 1 is a cross-sectional side view of one embodiment of a valve of the present invention.

Figure 2 is a cross-sectional plan view taken at line 2-2 of Figure 1.

Figure 3 is an end view partially in crosssection of the valve of Figure 1.

Figure 4 shown on the first page of drawings is a top view of the valve in Figure 3 showing the valve handle and quadrant.

Figure 5 shown on the second page of drawings is a partial cross-sectional side view through a portion of the stem and the disc showing a valve of the present invention positioned between two flanges.

Referring now to the drawings, the wafer type butterfly valve has a rigid annular body 10 as seen in Figures 1, 2 and 3. The annular body is preferably made from cast iron, but in some cases it may be brass, bronze, nodular iron, malleable iron, ductile iron or stainless steel to suit certain corrosive conditions. The annular body 10 has two internal annular ribs 11 as seen in Figure 2. These ribs extend around the internal circumference of the body 10 and provide an annular space 12 between them. Opposing external parallel end surfaces 13 of the annular body 10 are precision cast. Opposing internal parallel end surfaces 14 of the ribs 11 are also precision cast and have a smaller diameter than the external end surfaces 13 and are spaced inwards from them.No surfaces with the exception of parts of the stem bore in the annular body need be machined but may exist with the "as cast" finish. A rotary valve stem 1 5 passes through the centre of the annular body 10 and is attached to a closure disc 1 6 by means of a machine screw 1 7 which is sealed by an O-ring 18 using washer 48. The rotary stem 1 5 is supported at the base of the annular body 10 in a self-lubricating bearing 1 9 contained in a boss 20 which forms part of the body 10. The annular space 12 between the ribs at the base of the rotary stem 1 5 is taken up by a flattened section of the body 10. Where the stem 1 5 extends from the annular body 10 another self-lubricated bearing 21 supports it. This bearing 21 is located within a boss 22 similar to the lower boss 20 and forms part of the body 10.

A flexible metal ring 23 having round apertures 23A, 1 80C apart, to allow the stem 1 5 to pass therethrough, is positioned concentrically within an annular seat 24. The metal ring 23 is reinforced in the area of the apertures 23A. The apertures 23A are larger in diameter than the stem 1 5 to allow seat material to be interposed between the ring 23 and the stem 1 5. The ring 23 is preferably made from steel or other suitable high strength metals and has the annular seat 24 made of elastomeric material bonded about its surface.

The annular seat 24 is a resilient material preferably a one-piece molded rubber material having an internal passageway surface 26 which provides a seat for the disc 1 6 when the valve is closed. The internal diameter of the annular seat 24 is smaller than the external diameter of the disc 1 6. A cylindrical aperture in the annular seat 24 for the stem to pass therethrough has two internal radiused molded beads 24A as may be seen in figure 5, formed of resilient material which act as seals for the stem 1 5. These molded beads 24A are compressed and deformed when the stem is in place to conform to the cylindrical surface shape of the stem. The annular seat 24 has two external flanges 27 which extend around the ends of the metal ring 23 forming a seat having a U-shape in half cross-section.The two external flanges 27 overlap the recessed opposing internal parallel surfaces 14 of the ribs 11. The end surfaces of these external flanges 27 are tapered radially inwards towards the fluid flow axis of the valve body and each have two concentric molded radiused beads 28 positioned thereon. When the valve is in service and clamped between two opposing flanges these beads 28 are deformed under flange compression and the resilient material of the head deforms to seal the flange face. On each side of the internal passageway surface 26 of the annular seat 24 there is a radial corner which has a conical end face to prevent the resilient material from distorting and bulging unevenly when the external flanges 27 are clamped between the two opposing flanges and interfere with the operation of the closure disc.An annular clearance 25 remains between the annular seat 24 and the inside diameter of the two ribs 11 thus permitting radial deformation of the annular seat without interfering with the body of the valve.

The valve body 10 has an annular neck portion 30 as shown jn.Figure 1 which surrounds the valve stem 1 5. This neck portion 30 is a continuation of the casting of the main annular body 10 and terminates at a partially round neck flange 31. A seal 32 is incorporated within this quadrant flange 31 to exclude dirt from the valve and to prevent leakage along the valve stem 1 5 either out of the valve if there is a pressure internally or into the valve if there is a vacuum internally. The seal shown is a two way seal to prevent flow from either direction. This seal may be replaced by two single direction seals back-toback to serve the same purpose.

As may be seen in Figures 3 and 4, a long armed handle 33 is retained at one end of the valve stem 1 5 having two flattened surfaces by means of a set screw 34. A circular quadrant 35 having a series of slots 36 in a number of equally spaced positions in a sector less than 900 is mounted on top of the neck flange 31 and held in position by two sets of nuts and bolts 37. A grip lever 38 is provided beneath the handle 33 having a pivot pin 39 attached to the handle upon which the lever pivots and a compression spring 40 maintains the lever in a free extended engaged position. At the end of the grip lever 38 is a locking lug portion 41 which is adapted to locate and wedge in one of the notches 36 of the quadrant 35 when the lever 38 is in the free extended engaged position.

In the embodiment shown in Figure 4, the valve disc 1 6 is in the closed position with the plane of the sealing edge at an angle in a range of approximately 0 to 50 off the 900 perpendicular position. In this closed position, the flexible ring 23 is formed into an elliptical shape by the disc to ensure that the internal passageway surface 26 of the annular seat 24 is impinged upon by the tip of the disc 1 6 evenly around the circumference. The handle 33 at the top of the stem 1 5 is positioned so that with the disc 1 6 in the closed position, namely at an angle in a range of approximately 0 to 50 off the perpendicular position, the handle 33 is approximately 2+0 in the direction of closing from the disc sealing edge plane.The quadrant 35 has ten notches 36 which take up a circular arc of approximately 87+0. Each notch is identified by a pointer 42 on the handle 33 pointing to a position indicator marked on the quadrant 35. The position indicator has ten equally spaced marks 42A positioned around the periphery of the quadrant 35 and which take up a circular arc of approximately 87+0 with the SHUT position at the perpendicular position for the end notch, and the OPEN position at the axial position of the valve disc 1 6 for the other end notch.When the handle 33 is moved from the SHUT position to the OPEN position, it passes through an- angle of approximately 87+0 and thus the disc 1 6 is less than approximately 2+0 from the axial position and presents the minimum resistance to flow through the valve. A stop 43 fromed by bending a portion of the quadrant 35 upright is positioned to ensure that the handle 33 does not go beyond the OPEN position, and a similar stop 44 is positioned to prevent the handle going beyond the SHUT position.

A series of holes 43A are equispaced about a radial arc in the quadrant 35 adjacent the marks 42A. A stop pin 44A is shown positioned in one of the holes 43A such that when the handle 33 is rotated, the pointer 42 comes to rest against the stop pin 44A and is aligned with one of the marks 42A. Thus the stop poin 44A provides a stop to locate the disc 1 6 in a partially open position.

In another embodiment two stop pins 44A may be positioned in two separate holes 43A such that when the handle 33 is rotated, the pointer 42 comes to rest against either one or the other stop pin with less than about 300 of rotary movement.

The nuts and bolts 37 that hold the quadrant 35 to the neck flange 31 pass in one instance through a slot 45 and in another instance through one of two separate holes 46 in the quadrant 35 and through mating holes in the neck flange 31.

Thus, whereas in the initial closed position, the disc 16 is at an angle of approximately 5 off the perpendicular position, when the disc does seal around the circumference of the seat then the quadrant position may be changed by moving the nut and bolt 37 to the other hole 46 by rotating the quadrant 35 on the neck flange 31 so that the seating position moves through an angle of approximately 50 and a new closed position occurs on the seat. In this new position, the disc may be in the perpendicular position; thus the annular seat 24 forms into a circle to conform with the circumference of the disc.

When the valve is initially assembled, its fully closed position occurs with the disc at an angle in the range of approximately 850 to the fluid flow axis. If, for example, the disc is closed at an angle of 850 to the pipeline axis, then for 87+0 disc movement when the valve is fully open the disc will be at an angle of 2+0 to the pipeline axis.

If, for example, the disc is at an angle of 90" to the pipeline axis in the closed position, as could exist with seat wear, for 87+0 disc movement, it will be at an angle of 2+0 to the pipeline axis for the fully OPEN position.

A partial section of a valve assembly is shown in Figure 5 with two flanges 50 clamped together against the opposite external parallel side surfaces 13 of the annular body 10 compressing the external flanges 27 of the resilient annular seat 24. The two concentric molded beads 28 as seen in Figure 2 deform and their surface shape contours t6 the shape of the face of the flange 50 when the valve assembly is clamped together.

Thus the flanges 50 hold the annular seat 24 in position relative to the body by clamping and hence support the rigid ring 23 in a flexibly located relationship by means of the elastomeric seat material; that is to say, allowing it to change shape or position to seal with the disc. The resilient material of the seat is flexed, stretched and compressed to allow this movement.

As may be seen in figure 3 in another embodiment an inlet connector 55 is positioned on the external diameter of the annular body 10 at an angle of 900 from the entry of the valve stem 1 5. This inlet connector 55 provides access to the annular space 12 which extends circumferentially around the annular body 10. A cooling medium or heating medium may be passed through the inlet connector 55 to circulate around the annular space 12. The medium passes the stem 1 5 at the bottom and at the top of the body 10 through the circumferential spaces 25 between the annular seat 24 and the internal surface of the bosses 20 and 22. The medium heats or cools the annular seat 24. An outlet connector 56 positioned at an angle of 900 from the entry of the valve stem 1 5 diametrically opposite the inlet connector 55 permits complete circulation of the medium through the annular body 10. A suitable cooling fluid medium is used to cool the resilient seat when hot fluids are passed through the valve. This allows higher operating temperatures for the valve without deterioration of the annular seat.

Claims (6)

1. A butterfly valve assembly adapted to be positioned between opposing flanges of, for example, adjacent pipe ends, the assembly comprising a rigid generally annular valve body defining a fluid flow aperture, a generally annular valve seat located within the annular valve body, and a rotatably mounted valve disc adapted to cooperate with the valve seat to control fluid flow through the valve body, the valve body having an internal generally cylindrical surface carrying a pair of axially spaced apart circumferentially extending annular ribs, the valve seat comprising a hollow cylindrical part encircled by the ribs and made of an elastomeric material, such hollow cylindrical part carrying at each end thereof outwardly directed resilient flanges which overlap the annular ribs, whereby in use of the valve the resilient flanges will be clamped against the ribs to form seals therewith, an annular cavity lying between the ribs and being formed between the said internal generally cylindrical surface of the valve body and the hollow cylindrical part of the valve seat, such hollow cylindrical valve seat part being reinforced by metallic bracing means, for example a metal ring embedded in elastomeric material, the arrangement being such that when the disc is in a closing position in contact with the valve seat it can deform the annular valve seat into the space provided by the cavity, the bracing means assisting in returning the valve seat to an undeformed condition when the valve disc is moved away from its closed position.

2. A butterfly valve assembly adapted for positioning between opposing, spaced-apart flanges in a fluid flow system, said assembly comprising: A. a rigid body having opposing external flat parallel end surfaces adapted to mate with the opposing flanges, said body having opposing internal end surfaces spaced inwards from and having a smaller diameter than said external end surfaces, said body adapted to permit fluid flow therethrough and to accept a valve closure member; B. a valve closure member rotatably mounted within said body and adapted to co-operate with a seat assembly to regulate fluid flow through said rigid body; C. a seat assembly adapted to co-operate with said valve closure member between an open position and a closed position, said seat assembly comprising:: i. a flexible ring disposed in said rigid body for resilient flexible engagement with an annular seat; and ii. an annular seat disposed in said rigid body supporting said flexible ring, said seat assembly and said rigid body defining an annular space therebetween adapted for the passage of a fluid medium therethrough, said seat assembly having an external flange on each end adapted to be clamped between its respective internal end surface and one of the opposing flanges; and D. an inlet connector and an outlet connector communicating with the annular space and adapted to receive and pass a fluid medium therethrough, whereby rotation of said valve closure member to a closed position forces said seat assembly to deform into the annular space and simultaneously permits fluid to pass from said inlet connector through the annular space to said outlet connector.

3. A valve according to claim 2 wherein said closure member comprises a circular disc mounted to a rotatable valve stem extending through the centre of said rigid body, and wherein said disc seals with the internal surface of said annular seat within a range of approximately 0 to 50 on one side of a plane perpendicular to a fluid flow axis of said rigid valve body.

4. A valve assembly of claim 3 wherein said opposing internal end surfaces are flat and parallel.

5. The valve assembly of claim 4 wherein said flexible ring is steel and wherein said annular seat is an elastomeric material bonded to said flexible ring.

6. A valve assembly substantially as described herein with reference to the accompanying drawings.