Cartridge seated plug valve

A cartridge seated plug valve includes a hollow body with an inlet, an outlet, and a cylindrical valve chamber. A C-shaped rotor with an elastomeric coating is rotatably held in the valve chamber by a valve cover and a base. A valve facing with an elastomeric gasket is held adjacent to the inlet, with a central aperture of the valve facing aligned with the inlet, and the elastomeric gasket held in compression about an inlet seal surface at a perimeter of the inlet, by facing channels in the cover and base. In a closed position, the rotor is oriented with the elastomeric coating of the plug segment sealing the central aperture. The valve is opened by rotating the main stem, changing an orientation of the rotary plug, and moving the plug segment away from the inlet.

FIELD OF THE INVENTION

The invention pertains to the field of hydraulic valves. More particularly, the invention pertains to cartridge seated plug valves.

DESCRIPTION OF RELATED ART

A cartridge plug valve generally includes a hollow valve body with at least one inlet and one outlet each passing through the hollow valve body at opposing sides of a cylindrical valve chamber internal to the hollow valve body. Typically the hollow valve body is constructed of cast iron, but any material that is structurally sound and non-reactive with fluids passing through the cartridge plug valve may be used. A surface of a wall of the cylindrical valve chamber surrounding the inlet forms an inlet seal surface. The cylindrical valve chamber is sealed with a base at a first end of the hollow valve body. The base may be a unitary element of the hollow valve body and part of a single casting, or may be attached to the hollow valve body by welding, bolts, or other types of fasteners, thus closing the first end of the cylindrical valve chamber.

A cartridge includes a C-shaped rotor and a valve cover. The C-shaped rotor includes a plug segment with a first end and a second end. The first end of the plug segment is connected to the trunnion by a first elbow segment, and the second end of the plug segment is connected to the main stem by a second elbow. The main stem passes through a main stem journal of the valve cover, and the base includes a trunnion journal for accepting the trunnion. Thus, when the cartridge is inserted into the cylindrical valve chamber of the hollow valve body, the valve cover seals the cylindrical valve chamber at the second end of the hollow valve body, and the rotor is free to rotate in the trunnion journal and the main stem journal which share a common axis defined by a center of the trunnion journal and a center of the main stem journal, and henceforth referred to herein as the rotor axis.

As shown in a prior patent by the present inventor, Kennedy (U.S. Pat. No. 4,697,786, issued 1987), the rotor axis is offset from a central axis of the cylindrical valve chamber so that the rotor turns eccentrically relative to the cylindrical valve chamber. Thus, when the rotor is in a first position, a seal surface of the plug segment is held in contact with the inlet seal surface. When the rotor is turned to a second orientation, generally at a right angle to the first orientation, the plug segment rotates away from the inlet, and due to the eccentricity of the rotor axis relative to the cylindrical valve chamber axis, also moves radially away from the wall of the cylindrical valve chamber. As a result, the plug segment does not contact the surface of the valve chamber or other valve components when in motion, wear on seal surfaces is minimized, and valve operation requires less effort.

In the prior art, seal integrity at the inlet seal surface has been improved by various constructions. In some constructions, a nickel alloy seat ring is welded into the side of the cylindrical valve chamber surrounding the inlet and forms the inlet seal surface. Additionally, the plug segment of the rotor is coated with an elastomeric layer. Thus, when the plug segment is rotated into the first orientation covering the inlet, the elastomeric coating of the plug segment is compressed against the nickel alloy ring of the inlet seal surface forming a tight seal, and flow of a fluid through the inlet into the cylindrical valve chamber is blocked.

While this construction is effective, manufacturing costs may be significant. Nickel alloy is a durable metal that is easily welded to, or integrated into, a cast iron hollow valve body. However, nickel alloy is relatively expensive compared to other metals, and integration of the nickel alloy seating ring into the hollow valve body may require significant machining after casting. Further, in the event of damage to the nickel alloy seating ring, the entire hollow valve body may require replacement.

Also, the prior art Kennedy patent (U.S. Pat. No. 4,697,786, issued 1987) describes a cartridge plug valve having a removable inlet seal surface. In this construction, a metal plate conforms to the wall of the cylindrical valve chamber surrounding the inlet. The metal plate has a central aperture that is the same size of the inlet and aligned with the inlet. An elastomeric coating is applied to both sides of the metal plate and forms a seal surface on both sides of the plate. A channel in the base of the hollow valve body accepts a first end of the metal plate, and a pin in the valve cover mates with a slot cut into a second end of the metal plate. Thus, when the cartridge and hollow valve body are assembled, the metal plate is held firmly against the wall of the valve chamber at the location of the inlet, and is also prevented from rotating within the valve chamber so that alignment with the inlet is maintained.

A cast iron rotor is cast with an integral nickel alloy ring in the plug segment of the rotor. After machining the plug segment containing the nickel alloy ring to a finished profile, the nickel alloy ring forms a seal surface with the elastomeric coating of the metal plate surrounding the inlet. In the first position of the rotor, the seal surface of the plug segment is held against the central aperture of the metal plate, deforming the elastomeric coating of the metal plate to both the seal surface of the plug segment, and the inlet, thus preventing flow of a fluid from the inlet into the cylindrical valve chamber. When the rotor is moved to a second position, the plug segment rotates away from the metal plate, and also radially away from the metal plate and the wall of the cylindrical valve chamber. Thus, a fluid is permitted to flow from the inlet, through the central aperture of the metal plate, and into the cylindrical valve chamber.

This construction provides an effective inlet seal, and allows the metal plate forming the inlet seal surface to be easily replaced if necessary. However, the nickel alloy ring cast into the plug segment of the cast iron rotor increases construction materials costs and finishing time to shape the final seal surface of the plug segment. Further, in the event of damage or wear to the seal surface of the plug segment, the entire rotor must be replaced.

SUMMARY OF THE INVENTION

A cartridge seated plug valve of a construction described herein includes a hollow valve body with a cylindrical valve chamber passing between a first end and a second end of the hollow valve body. The cylindrical valve chamber includes a cylindrical wall and a cylindrical valve chamber axis. An inlet passes through the hollow valve body into the cylindrical valve chamber at a first location and an outlet passes through the hollow valve body into the cylindrical valve chamber at a second location. A seal surface surrounds the inlet on the cylindrical valve chamber wall.

A base is attached to the hollow valve body sealing the cylindrical valve chamber at the first end of the hollow valve body. The base has an inner side including a trunnion journal for receiving a trunnion. The trunnion journal has a center that is radially offset from the cylindrical valve chamber axis. A first facing channel with a radius of curvature having an origin at the cylindrical valve chamber axis is defined in the inner side of the base.

A valve cover seals the cylindrical valve chamber at the second end of the hollow valve body. The valve cover has an inner side and an outer side, and includes a main stem journal passing from the inner side to the outer side. The main stem journal has a center that is radially offset from the cylindrical valve chamber axis. A second facing channel with a radius of curvature having an origin at the cylindrical valve chamber axis is formed in the inner side of the valve cover. The center of the main stem journal and the center of the trunnion journal define a rotor axis.

A rotor includes a plug segment with a first end and a second end. The first end of the plug segment is connected to a trunnion by a first elbow segment, and the second end of the plug segment is connected to the main stem by a second elbow segment. The plug segment also has a sealing surface. An elastomeric coating is applied to the first elbow, the second elbow, and the plug segment. The rotor is rotatably held by the main stem being accepted by the main stem journal of the valve cover, and the trunnion being accepted by the trunnion journal of the base. The first elbow segment and the second elbow segment hold the plug segment parallel to the rotor axis with the elastomeric coating of the plug segment adjacent to the seal surface of the inlet of the hollow valve body.

A valve facing has a body with a first side and a second side opposite the first side. An elastomeric gasket is bonded to the first side of the body. The body of the valve facing has a radius of curvature that is the same as the radius of curvature of the first facing channel and the radius of curvature of the second facing channel. A first end of the valve facing body is held in the first facing channel, and a second end of the valve facing body is held in the second facing channel. A central aperture passing through the valve facing is coincident with the inlet of the valve body.

When the rotor is in a first orientation with the plug segment adjacent the second side of the body of the valve facing, the eccentric axis of rotation of the rotor forces the elastomeric coating of the plug segment against the second side of the body of the valve facing. The central aperture of the valve facing is thus sealed, blocking flow of a fluid from the inlet into the cylindrical valve chamber. When the rotor is rotated to a second orientation, the plug segment of the rotor moves away from the body of the valve facing. In this orientation, the plug segment of the rotor no longer seals the central aperture of the body of the valve facing, and flow of a fluid from the inlet into the cylindrical valve chamber is permitted.

DETAILED DESCRIPTION OF THE INVENTION

A cartridge seated plug valve of a construction described herein provides a replaceable valve facing that effectively seals an inlet of a hollow valve body, and also eliminates the nickel seating ring common in the prior art in either the hollow valve body or the plug segment of the rotor. Thus, material costs are reduced, and extensive machining of an inlet seal surface and/or a plug segment seal surface is significantly reduced or eliminated. Thus, the cartridge seated plug valve reduces overall production costs, and also simplifies maintenance and reduces maintenance costs.

An embodiment of the cartridge seated plug valve is shown inFIG. 1. The cartridge seated plug valve has a hollow valve body10. A hollow cylinder internal to the hollow valve body10forms a cylindrical valve chamber40that allows fluid flow between an inlet20and an outlet30when the cartridge seated plug valve is opened. A wall50of the cylindrical valve chamber40has a radius of curvature Rwwhose origin defines a valve chamber axis92. The inlet20is provided with an inlet flange21, and the outlet30is provided with an outlet flange31. Thus the hollow valve body10may be assembled in-line with a piping system through, for example, welding or bolting the inlet flange21and outlet flange31to appropriate mating flanges on pipes.

A base60seals the cylindrical valve chamber40at a first end of the hollow valve body10, and may be formed as an integral element of the hollow valve body10in a single casting. Alternatively, the base60may be formed as a separate element and affixed to the hollow valve body10with bolts, welds, or other techniques known in the art. As shown inFIG. 1andFIG. 2A, an inner surface of the base60is provided with a trunnion journal91. InFIG. 1andFIG. 2A, the trunnion journal91is shown as a simple cylindrical cup in the base60that is open to the cylindrical valve chamber40. However, bearings of any suitable type, or other elements that facilitate acceptance of a rotating member, such as a trunnion90, may also be used.

As shown inFIG. 2A, the trunnion journal91has a center that is coincident with a rotor axis93, and the rotor axis93is slightly offset from the valve chamber axis92in a lateral direction relative to the placement of the inlet20in the hollow valve body10. The inner surface of the base60is also provided with a first facing channel140a. The first facing channel140ais arcuate in shape and has a radius of curvature whose origin is coincident with the valve chamber axis92. The first facing channel140afollows a circumferential path at a radial distance Rcfrom the valve chamber axis92, generally from a location at a first side of the inlet20, past the inlet20and to a location at a second side of the inlet20. However, the first facing channel140ainFIG. 2Ais shown as a complete circle for ease of manufacturing. The first facing channel140ais co-axial with an inlet seal surface22formed in the wall50of the cylindrical valve chamber40surrounding the inlet20. The inlet seal surface22has a radius of curvature Rswith an origin at the valve chamber axis92

Referring toFIG. 1andFIG. 2B, a valve cover70, being the first element of a cartridge, seals the cylindrical valve chamber40at a second end of the hollow valve body10, and may be removably attached to the hollow valve body10with screws79, bolts, or other types of fasteners. The valve cover70is provided with a main stem journal101that passes through the valve cover70. InFIG. 1andFIG. 2B, the main stem journal101is shown as a simple cylindrical aperture passing through the valve cover70. However, bearings of any suitable type, or other elements that facilitate acceptance of a rotating member, such as a main stem100, passing through the valve cover70may also be used.

The main stem journal101has a center that is coincident with the rotor axis93, and the rotor axis93is slightly offset from the valve chamber axis92in a lateral direction relative to the placement of the inlet20in the hollow valve body10. An inner surface of the valve cover70is provided with a second facing channel140b. The second facing channel140bis arcuate in shape and has a radius of curvature whose origin is coincident with the valve chamber axis92. The second facing channel140bfollows a circumferential path, at a radial distance Rcfrom the valve chamber axis92, from a location at a first side of the inlet20, past the inlet20and to a location at a second side of the inlet20. The second facing channel140bis also co-axial with the inlet seal surface22formed in the wall50of the cylindrical valve chamber40surrounding the inlet20.

ComparingFIG. 2AandFIG. 2B, it will be apparent that the offset of the rotor axis93on the inner surface of the base60and offset of the rotor axis93on the inner surface of the valve cover70are in opposite directions relative to the valve chamber axis92. Thus, when the base60and valve cover70are in place at opposite ends of the hollow valve body10, the trunnion journal91and main stem journal101will be in alignment on the rotor axis93. Similarly, the second facing channel140bwill also be aligned with at least an arc length of the first facing channel140awhen the valve cover70and base60are assembled with the hollow valve body10.

The valve cover70and/or main stem journal101may also be fitted with seals, packing, or other elements known in the art that prevent fluid from passing through the main stem journal101from the cylindrical valve chamber40. Additionally, a crown with any end play adjustment mechanism known in the art may also be added to the valve cover70to ensure proper compression of the rotor75against the valve cover70as well as proper pressure on packing or other main stem journal101elements. Journal seals, packing, and end play adjustment mechanisms are well known in the art, and are omitted here for clarity, as they do not affect the novelty or utility of the cartridge seated plug valve described herein.

As shown inFIG. 1, a rotor75, the second element of the cartridge, includes a plug segment80that is aligned parallel to the valve chamber axis92. A first end of the plug segment80is connected to the trunnion90by a first elbow segment81. A second end of the plug segment80is connected to the main stem100by a second elbow segment82. Thus, the rotor75, including the first elbow segment81, the plug segment80, and the second elbow segment82, forms a C-shape. The first elbow segment81and second elbow segment82are dimensioned to hold a plug seal surface85of the plug segment80in close proximity to the inlet seal surface22surrounding the inlet20when the rotor75is in a first position with the plug segment80aligned with the inlet20. As shown inFIG. 5, at the first position the plug seal surface has a radius of curvature Rpwith an origin in alignment with the valve chamber axis92.

The plug segment80of the rotor75is also provided with an elastomeric coating110that covers at least the plug seal surface85of the plug segment80of the rotor75. In one embodiment, the elastomeric coating covers the entire plug segment80, the first elbow81, and the second elbow82. The elastomeric coating110may be bonded to the plug segment80by any technique known in the art, and is preferably bonded with a rubber tearing bond. For the purposes of this description, a rubber tearing bond is defined as a destructive bond between an elastomeric material and a second material, wherein the elastomeric material will mechanically fail before the bond fails when forces are applied to the elastomeric material that would otherwise cause the elastomeric material to separate from the second material. The elastomeric coating110is preferably ethylene propylene diene monomer (EPDM) rubber. However, any elastomeric material capable of elastic deformation may be used.

FIG. 3shows a valve facing120. The valve facing120is metal plate with a first end E1and a second end E2, and in preferred embodiments is constructed of stainless steel. However, any other structural material that provides structural rigidity and are non-reactive to fluids passing through the cartridge seated plug valve may also be used, such as carbon fiber, structural plastic, or other metals, for example. The valve facing120has a first120aside to which an elastomeric gasket130is applied. The elastomeric gasket130surrounds a central aperture125of the valve facing120. The elastomeric gasket130may cover the entire first side120aof the valve facing120, or may be limited to an area that will mate with the inlet seal surface22when the valve facing120is positioned in the cylindrical valve chamber40at the position of the inlet20.

The elastomeric gasket130is preferably made of ethylene propylene diene monomer (EPDM) rubber. However, any elastomeric material capable of elastic deformation may be used. The elastomeric gasket130may be bonded to the first side120aof the valve facing120by any technique known in the art, and is preferably bonded with a rubber tearing bond.FIG. 4shows a cross section of the valve facing ofFIG. 3.

Referring again toFIG. 1, the cartridge seated plug valve is assembled by first placing the valve facing120into the cylindrical valve chamber40, with the first end E1of the valve facing120being accepted by the first facing channel140a. The valve facing120is also positioned at the location of the inlet seal surface22, with the elastomeric gasket130being held in compression against the inlet seal surface22. The central aperture125of the valve facing120coincides with the inlet20of the hollow valve body10.

The main stem100of the rotor75is assembled through the main stem journal101of the valve cover70, and other elements such as journal seals, packing, and end play adjustment mechanisms are also assembled to complete the cartridge.

The rotor75is then inserted into the cylindrical valve chamber40and oriented, as shown inFIG. 1andFIG. 5, so that the trunnion90is received by the trunnion journal91. When the cartridge is fully inserted into the cylindrical valve chamber40, and the valve cover70is bolted to the hollow valve body10, the second end E2of the valve facing120is received by the second facing channel140b, and the elastomeric gasket130of the valve facing120tightly against the inlet seal surface22of the inlet20. The first facing channel140aand the second facing channel140b, both being co-axial with, and adjacent to, the inlet seal surface22at each end of the cylindrical valve chamber40, ensures a tight seal between the valve facing120and the inlet seal surface22.

When the cartridge seated plug valve is in a closed state, the elastomeric coating110of the plug seal surface85of the plug segment80of the rotor75is held tightly against the second side120bof the valve facing120, covering the central aperture125of the valve facing120, so that flow of a fluid from the inlet through the valve facing120is blocked.

The cartridge seated plug valve is opened by rotating the main stem100, generally one-quarter turn relative to the inlet20, so that the plug segment80rotates away from the position of the inlet20. Because the rotor axis93is offset relative to the valve chamber axis92, and the distance between the plug seal surface85and the rotor axis93is fixed by the lengths of the first elbow segment81and the second elbow segment82, as the plug segment80rotates away from the inlet20, the plug segment80also moves radially away from the wall50of the cylindrical valve chamber40. Thus, frictional forces between the wall50of the cylindrical valve chamber40are minimized when the plug segment80of the rotor75is moved to a second position away from the inlet20.

When the rotor75is returned to the first position, the plug segment80moves radially toward the wall50of the cylindrical valve chamber40and the inlet seal surface22, and compresses the elastomeric coating110of the plug seal surface85against the second side120bof the valve facing120, covering the central aperture125of the valve facing120to create a fluid-tight seal.

The cartridge seated plug valve described herein provides a number of advantages over the prior art. Nickel alloy may be significantly more expensive than, for example, stainless steel. Thus, by removing nickel allow seating rings, a significant reduction in manufacturing costs may be achieved. Similarly, whereas incorporation of nickel alloy seating rings into either a hollow valve body10or a plug segment80of a rotor75may require significant machining of seal surfaces after casting to ensure a tight seal during valve operation, the valve facing120and elastomeric gasket130described herein are easily formed, require lower tolerances at inlet seal surfaces22, and may be rapidly replaced in the field. In addition, the elastomeric coating110of the rotor75may be replaced as necessary by reworking rotors75with damaged or worn elastomeric coatings110.