Method of assembling a ball valve

Abstract

A ball valve includes a valve element and a single piece packing that seals the valve element within a valve cavity. The single piece packing is installed over the valve element at room temperature or may be molded thereon. The valve element may include a flow control element such as a ball and upper and lower trunnions. The various dimensions of the valve element and packing are selected to facilitate room temperature assembly and to substantially reduce the volume of packing material, thereby improving the performance of the valve over wider temperature ranges and pressure ratings.

1 - 34 . (canceled) 
     
     
         35 . A method for assembling a valve comprising the steps of:
 forming a single piece packing;   assembling said single piece packing onto a valve element prior to assembling the valve element into a valve body, wherein the valve element comprises a ball, an upper trunnion and a lower trunnion, said ball having an outer diameter D 1  and at least one of said upper trunnion or said lower trunnion having an outer diameter D 3 , wherein said valve element comprises a ratio D 3 /D 1  of 0.7 to 0.9;   installing said single piece packing and the valve element into a valve cavity of the valve body such that said single piece packing seals against the valve body and the valve element with a lower end of said single piece packing sealing directly against said lower trunnion.   
     
     
         36 . The method of  claim 35  wherein said single piece packing is formed from a material selected from the group consisting of perfluoroalkoxy (PFA), ultra-high molecular weight polyethylene, polytetrafluoroethylene (PTFE), variants of PTFE, polyetheretherketone (PEEK), filled PFA, and fluorinated ethylene propylene. 
     
     
         37 . The method of  claim 35  comprising providing an axial gap between an end surface of said lower trunnion and the valve body upon installation of said single piece packing and said valve element in the valve cavity. 
     
     
         38 . The method of  claim 35  wherein said ball is spherical and said upper trunnion and said lower trunnion are cylindrical. 
     
     
         39 . The method of  claim 38  wherein said single piece packing comprises an interior surface that conforms to said ball and said upper trunnion and said lower trunnion. 
     
     
         40 . The method of  claim 35  further comprising roughening the valve cavity prior to installing the packing and valve element in the valve cavity. 
     
     
         41 . The method of  claim 35  further comprising assembling a plurality of load applying members in the valve body and compressing the load applying members to effect a load on said single piece packing. 
     
     
         42 . The method of  claim 35  wherein said lower trunnion extends past a lowermost end of said single piece packing. 
     
     
         43 . The method of  claim 35  comprising the step of press fit assembling said single piece packing onto the valve element prior to assembling the valve element into the valve body. 
     
     
         44 . The method of  claim 43  wherein said press fit assembling is performed within a room temperature range without changing elasticity of said single piece packing material. 
     
     
         45 . The method of  claim 35  wherein said single piece packing is over-molded in place on said valve element.