Abstract:
A lined ball valve includes a preformed polymeric liner having a flow passage therethrough. The flow passage has a valve stem opening transverse to the flow direction. A ball element with a flow opening therethrough is rotatably mounted in the flow passage. A valve stem is connected to the ball element. A body of fiber-reinforced polymer is molded around the preformed liner. A method for manufacturing a lined valve includes the steps of: (a) injection molding a polymeric preformed liner; (b) supporting the preformed polymeric liner inside a body mold; and (c) compression molding a fiber reinforced resin valve body around the preformed liner.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     The present application claims benefit from U.S. provisional pat. application Ser. No. 60/517,595, filed Nov. 5, 2003, the disclosure of which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD OF THE INVENTION  
       [0002]     The present invention relates to valves and in particular to a valve with a fiber-reinforced polymer (“FRP”) valve body with a polymeric lining for corrosion protection.  
       BACKGROUND  
       [0003]     Teflon® and other fluoropolymer linings are used extensively in industry to provide corrosion protection to components of piping and storage systems where corrosive chemicals are handled. These lined components typically include piping, tanks, pumps, metering devices, shutoff valves and control valves. The function of the lining material is to provide a corrosion barrier to protect the structural elements of the component, such as the pump casing, valve body or the pipe wall. The structural element is usually metallic, with carbon steel or ductile iron being the most popular. In the case of pipes and tanks, the fluoropolymer lining may be supported by a filament-wound FRP composite outer shell that is wound around the liner and cured. Filament winding of lined pipes and tanks is feasible because of their uniform cylindrical shape.  
         [0004]     Valves, on the other hand, typically have complex internal and external geometries and do not easily lend themselves to filament winding. For this reason, lined valves with integral liners have until now been manufactured by injecting a molten fluoropolymer lining into a metal-bodied valve body. The valve body acts as the mold for the process. This method requires that the body material, since it is in contact with the melted polymer, be able to withstand the heat and pressure of the injection process. Most metals, including common ductile iron and carbon steel, can be used. The metal body can be used as a mold because the metal body can withstand the molding temperature of 650° F. and high pressure developed in the transfer molding process. U.S. Pat. Nos. 3,334,650; 4,696,323; 4,535,803; 5,979,491; 5,634,486; and 3,073,336 disclose prior art valves with corrosion resistant linings.  
         [0005]     It has long been demonstrated that advanced polymer composite materials provide corrosion resistance, strength and low cost. The utility of a polymer composite bodied valve could be measurably enhanced if the composite valve body could be fitted with a polymeric liner. With the liner in place, the valve could be used in a wide range of chemical services/applications where normally the flowing fluid would attack the polymer body. Additionally, since the polymer body would be isolated from contact with a high temperature flowing chemical medium, the valve could be used at significantly higher flowing fluid temperatures than valves with composite bodies without the lining. The polymer body provides external corrosion protection from the operating environment that is far superior to the paint used externally on lined valves with metal bodies. A further important advantage is that the weight of a lined composite valve will be far less than the comparable lined valve with a metal body. This reduces the need for costly supporting structures in the piping system. Additionally, a composite valve body has fewer joints, eliminating potential points for leakage.  
       SUMMARY OF THE INVENTION  
       [0006]     A lined ball valve includes a preformed polymeric liner having a flow passage therethrough. The flow passage has a valve stem opening transverse to the flow direction. A ball element with a flow opening therethrough is rotatably mounted in the flow passage. A valve stem is connected to the ball element. A body of fiber-reinforced polymer is molded around the preformed liner.  
         [0007]     The polymeric liner may be preformed from a material chosen from the group of fluoropolymers, PVC and CPVC. The body may be formed from thermoset resin and fiberglass and may be compression molded at a temperature of less than about 300 degrees F.  
         [0008]     The valve may include a retainer adapted to retain the preformed liner in the body, wherein the retainer is removably disposed in the valve body and contacts the liner.  
         [0009]     The retainer may comprise a tubular member with external threads that threadedly engage internal threads disposed in the valve body. The valve may further include a circumferential shelf disposed in the valve stem opening wherein the shelf is adapted to retain the valve stem.  
         [0010]     A method for manufacturing a lined valve includes the steps of: (a) injection molding a polymeric preformed liner; (b) supporting the preformed polymeric liner inside a body mold; and (c) compression molding a fiber reinforced resin valve body around the preformed liner. The method of manufacture may further include after step (a), a step of etching the exterior surface of the preformed liner to increase adhesion of the fiber reinforced body to the liner. The step of etching may be mechanical and/or chemical. The manufacturing process may also include the step of molding mechanical locking ridges on the exterior of the polymeric preformed liner.  
         [0011]     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0012]      FIG. 1  is a cross-section of a FRP valve with polymeric liner, in accordance with the present invention;  
         [0013]      FIG. 2  is an exploded cross-section of the FRP valve of  FIG. 1 ;  
         [0014]      FIG. 3  is a cross-section of the polymeric liner of the FRP valve of  FIG. 1 ;  
         [0015]      FIG. 4  is a simplified perspective of a FRP valve of the present invention;  
         [0016]      FIGS. 5A and 5B  are an enlarged cross-section of the valve stem sealing elements of the FRP valve of the present invention; and  
         [0017]      FIG. 6  is a simplified partial cross-section of a compression molding press with the polymeric liner of the FRP valve of  FIG. 1  disposed therein. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]     Reference is now made to drawings wherein like reference characters denote like or similar parts throughout the Figures.  
         [0019]     Referring now to  FIG. 1 , the FRP body  10  of the valve  100  is fully lined with a corrosion resistant liner  20  of polymeric material such as Teflon® or other less costly polymeric material such as PVC or CPVC. It will be understood by those skilled in the art that any polymeric material capable of injection molding may be used in the present invention. The body  10  of valve  100  is molded in one piece from a composite resin. This one piece body eliminates lateral or longitudinal seams used in assembling some prior art valves, thereby eliminating additional sources of leaks.  
         [0020]     As can be seen in  FIGS. 1 and 2 , valve  100  is illustrated in a first embodiment as a conventional ball valve. Various types of valves are available to be used across a wide range of applications, such as chemical processing, water control, petroleum refining, and fluid transport. Ball valves are a very popular choice for many of these applications because ball valves are reliable and simple to use. A ball valve  100  in its simplest form comprises a housing or body  10  having flow passage  110  in each end of the body that can be placed in line with, and attached to, a pipe using flanged connections or other means of conventional connections known by one skilled in the art.  
         [0021]     A ball element  70 , having a cylindrical flow opening  72  through the ball is disposed in the valve body  10 . The ball element  70  can be rotated inside the body  10  so that fluid flows when the opening  72  in the ball element  70  is in line with the passage  110  in the valve body and with a pipe containing fluid or gas. Fluid or gas does not flow through valve  100  when the opening  72  through the ball is transverse to the axis of passage  110  in the valve body and the pipe (i.e., when the pipe “sees” only the solid sides of the ball). In this manner, ball valve  100  can be turned from completely closed to wide open simply by turning the ball one-quarter turn.  
         [0022]     Flow passage  110  will generally be enlarged slightly at the location of ball element  70  so that ball element  70  can form a seal around the periphery of the flow passage. Seats  80  may be provided in the flow passage  110  and in contact with ball element  70 , to prevent fluid leakage when the valve  100  is closed. The depicted embodiment of the valve includes seats  80  on both sides of the ball element  70 . This type of valve may be referred to as bi-directional and will seal against fluid flow in either direction. It will be understood by those skilled in the art that the present invention may encompass a unidirection valve having a seat and sealing element disposed only one side of a ball element.  
         [0023]     Ball element  70  may be formed from stainless steel or other alloy and encapsulated with a corrosion resistant coating. Alternatively, one skilled in the art will appreciate the ball  70  may be formed of polymeric corrosion resistant material of a predetermined strength based on the intended pressure service for the valve  100 . The seals and seats may be formed of any appropriate material, including MN-7 polymer, Teflon, or PTFE or metal, all of which may be encapsulated with corrosion resistant material.  
         [0024]     The ball element  70  is rotated and driven by valve stem  30 . Valve stem  30  contacts ball element  70  and extends through valve stem opening  23  to the outside of the valve body  10 . A packing material or other sealing material  50  may be provided between the valve stem  30  and the valve body  10  to prevent fluid from leaking out of the valve  100 . A recess  76  in the ball element may receive an end of the valve stem  30  to provide the connection between the valve stem and ball element. Other alternative means of connection between the ball element and valve stem are well known in the art. The valve stem  30  may be operated manually with a wrench or pre-attached handle or by an actuator, which may be mechanical, electromechanical, pneumatic, or any other suitable form. Manual and/or computer generated signals may provide instructions to the actuator.  
         [0025]     Referring now to  FIGS. 2 and 6 , therein is illustrated an exploded cross-sectional view of valve  100  and a simplified partial cross-section of a compression molding press  1000 . In order to manufacture valve  100 , a method must be used to install the liner without using the valve body  10  as a mold, since the polymer valve body  10  cannot survive the combination of high heat of the molten fluoropolymer and pressure during an injection molding process. This dilemma is resolved by reversing the traditional sequence of operations so that a thermoset resin is molded around a preformed fluoropolymer liner  20 . The resin is molded to form body  10  utilizing standard compression-molding technology with a press  1000  using punch  1010 . During molding of body  10 , the liner  20  is supported in a valve body mold  200  using a modification of a normal core pin arrangement of an unlined valve. The polymeric liner  20  may be placed over the waterway core pin  210  of the mold and the preformed liner  20  is oriented to engage the core pin  220  that forms the stem bore  26 . The temperature of this molding process, generally less than 300 F., is easily withstood by the preformed liner  20 . The preformed liner  20  can be easily and economically produced using a standard injection molding process and can be adapted to provide linings of many different polymeric materials of various costs and service capabilities.  
         [0026]     The outer surface  21  of the preformed lining in contact with the resin body material must be prepared with either an etching process or with mechanical locking ridges so that the resin at body  10  will adhere to it. Properly prepared, the liner  20  will not pull away or separate from the FRP body  10  in service.  
         [0027]     During manufacture of the valve  100 , as heretofore discussed, FRP composite body  10  is formed around the preformed liner  20 . An example of one such preformed liner  20  is illustrated in  FIG. 3 , while  FIG. 4  illustrates a simplified version of composite body  10  disposed around liner  20 .  
         [0028]     Returning to  FIGS. 1 and 2 , during assembly of the valve  100 , after the body  10  has been formed around the liner  20 , a first sealing element, comprising an O-ring seal  90  and a seat  80 , is inserted from the proximal end  112  of valve  100 . It will be understood by those skilled in the art that O-ring seal  90  and seat  80  may be separate elements and one or both may be present. However, it will be understood that a single composite element comprised of an O-ring and seat may be present as a composite sealing element. As used in this specification the component “sealing element” may include any device to prevent the passage of gas and/or fluid.  
         [0029]     Ball element  70  is inserted after the first sealing element and then a second sealing element may be inserted. As noted above in the present embodiment the sealing element may include one or both or a composite of an O-ring  90  and seat  80 . The ball element  70  and ball sealing elements are secured in position by a tubular shaped retainer  60  having an external threaded portion  62  with external threads that threadedly engage internal threads  14  disposed on an inner surface of valve body  10  in the proximal portion of flow passage  110 . As can be seen in  FIG. 1 , proximal O-ring  90 , instead of contacting seat  80  (as shown in  FIG. 2 ) may alternatively be disposed in a recess  64  of retainer  60 .  
         [0030]     Referring to  FIG. 5A , the stem area of the ball valve presents a challenge inasmuch as the stem  30  must penetrate the body  10  but must also be prevented from blowing out of the body in the event that an operator inadvertently removes the packing gland bolts (not shown) with the valve still under pressure. In the current invention, this feature can be provided by introducing a circumferential shelf  24  in the valve stem opening  23  of liner  20 . Alternatively, as illustrated in  FIG. 5B , a rigid ring  40  may be disposed around the neck  26  of preformed liner  20  prior to compression molding of the body  10  around liner  20  and ring  40 .  
         [0031]     It will be understood by those skilled in the art that check valves, diaphragm valves, plug valves and butterfly valves may be manufactured using the processes disclosed in the present invention.  
         [0032]     A preferred embodiment of the invention has been illustrated in the accompanying drawings and described herein. It will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous modifications without departing from the principles of the present invention, which is intended to be limited only by the scope of the appended claims, as interpreted according to the principles of patent law.