Abstract:
A shearing type of gate valve having a sleeve of hard wear resistant material in the opening through the gate and coacting with insert rings of hard, wear resistant material in the seat rings for shearing a wire line or tubular member extending through the valve and the gate, the sleeve and insert ring being assembled with the gate and the seat rings in a manner to provide sufficient compression preload thereon so that they are not subjected to tension loads which avoids chipping, breaking or other damage to the sleeve and the insert rings. Preferably the sleeve and insert rings are of tungsten carbide.

Description:
BACKGROUND 
     The present invention relates to a gate valve capable of shearing a wire line or small pipe extending through its bore. Gate valves have been used for shearing through wire lines and small tubular members but difficulties have been encountered after a shearing has taken place with prior shearing gate valves. Often the problem is that the valve which has accomplished the shearing no longer has a satisfactory seal. An additional problem is that prior shearing gate valves have also damaged the shearing edges during their initial shearing operation and had to be repaired prior to being placed in service thereafter. 
     U.S. Pat. Nos. 4,519,575 and 4,612,983 disclose typical prior art gate valves adapted for shearing a wire line extending through the valve passages and the gate. U.S. Pat. No. 4,519,575 discloses a gate valve for shearing a wire line on closing and the gate valve includes a special actuator which adds closing force during the last or shearing portion of the stroke. U.S. Pat. No. 4,612,983 discloses a gate valve having a pair of gates in which the lower gate closes and shears the wire line and then the upper gate closes and seals against the upper valve seat. 
     U.S. Pat. No. 4,281,819 discloses a balanced stem gate valve in which the sealing surfaces are hard, friction resistant sealing surfaces and suggests valve seats of metal or non-metal seat material concentrically disposed interiorly of seat retainers and sealed with sealing rings. Back-up seat rings are provided and are of a hard material such as tungsten carbide. 
     U.S. Pat. Nos. 4,081,027 and 4,341,264 disclose ram type blowout preventers having shearing type of rams in which the leading edge of the shearing blade of each ram is provided with a hardened shearing surface. In U.S. Pat. No. 4,081,027 it is suggested that the rams are hardfaced with a layer of nickel-based alloys, cobalt-based alloy and tungsten-based alloys to allow the shearing of a drill pipe. U.S. Pat. No. 4,341,264 suggest the use of a hardened material insert on the leading edges of the shear blades so that it is replaceable and the ram blade can be repaired after any damage during shearing. 
     U.S. Pat. No. 4,425,699 discloses the method of connecting a mechanical seal ring of hard metal or ceramic to a supporting ring made of aluminum or stainless steel which includes the pressing of the two rings against each other with such force that the supporting ring yields to provide a permanent engagement between the rings. 
     U.S. Pat. No. 4,337,920 discloses a valve or choke for use in high temperature and extremely abrasive service which includes the use of a sleeve of abrasion resistant material, such as cemented tungsten carbide, silicon carbide, titanium diboride, ceramic material or other material. The sleeve is supported by springs to prevent its damage from vibrations and to insulate it from the effects of differential expansion. 
     SUMMARY 
     The present invention relates to a shear type of gate valve in which both the gate and the seat rings include inserts of hard material to assist in the shearing of wire lines or tubular members extending through the valve when it is to be closed. The hard material, such as tungsten carbide, is formed into rings of suitable size and shape which are positioned in their respective recesses in the gate and the seat rings. The recess for each of the rings and the size of the ring are preselected so that the rings, once positioned in their recesses, are maintained in compression at all times. The preferred rings are made of tungsten carbide. 
     An object of the present invention is to provide an improved shearing type of gate valve in which the gate has a seal which is not damaged by the shearing action of the gate. 
     Another object is to provide an improved shearing type of gate valve in which the valve may be retained in service after multiple shearing closures of the gate. 
     A further object is to provide an improved shearing type of gate valve in which a brittle hard material is used without having the brittle material damaged by the shearing action of the valve. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and advantages of the present invention are hereinafter set forth and explained with reference to the drawings wherein: 
     FIG. 1 is sectional view of the improved shearing type of gate valve of the present invention shown in its open position. 
     FIG. 2 is a similar sectional view of the valve illustrated in FIG. 1 in closed position after shearing a wire line extending therethrough. 
     FIG. 3 is a quarter sectional view of the improved seat ring illustrating the insert ring of hard material positioned in a recess in the seat ring. 
     FIG. 4 is an elevation view of the improved gate of the present invention with the hardened ring positioned therein. 
     FIG. 5 is a sectional view taken along line 5--5 in FIG. 4 to show the position of the ring extending through the gate in surrounding relationship to the gate opening. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Valve 10, shown in FIGS. 1 and 2, discloses the improved shearing type of gate valve of the present invention. Valve 10 includes body 12 having an inlet 14, an outlet 16 with valve chamber 18 between the inner ends of inlet 14 and outlet 16 and bonnet 20 which is secured to body 12 around the opening of chamber 18 into body 12. Bonnet 20 supports actuator 22 which is shown as a simply pneumatic actuator having piston chamber 24 with piston 26 slidable therein and spring 28 urging piston 26 upward as shown. Connecting rod 30 extends from piston 26 through bonnet 20 into engagement with gate 32 for moving gate 32 within chamber 18 to open or close flow therethrough between inlet 14 and outlet 16. 
     Gate 32 is positioned between seat rings 34 and 36 which are positioned in recesses 38 and 40 of body 12, respectively, which surround the inner ends of inlet 14 and outlet 16 in chamber 18. Opening 42 which extends through gate 32 is lined with hardened sleeve 44 which coacts with hardened insert rings 46 and 48 positioned in seat rings 34 and 36 in the shearing action of the gate 32 during its closing movement when there is a wire line 50 or a tubular member (not shown) extending through valve 10. The shearing of wire line 50 is shown in FIG. 2. Wire line 50 has been sheared in two places by the action of sleeve 44 on the seat ring insert rings 46 and 48. 
     Seat rings 34 and 36 are identical and seat ring 34 is illustrated in FIG. 3 to explain the details of structure of rings 34 and 36. Ring 34 is annular in shape having bore 52, inner recess 54 on one end, projection 56 on the opposite end with seal ring groove 58 in its face for receiving a suitable seal ring; and external groove 60 in outer surface 64. Projection 56 is sized to fit tightly within recess 38 of body 12. Inner recess 54 is sized to have an inner diameter D which is smaller than the diameter of insert ring 46 prior to assembly. When assembled, insert ring 46 fits within inner recess 54 and abuts shoulder 62 of inner recess 54. Insert ring 48 is identical to insert ring 46. 
     The external diameter of insert ring 46 and the internal diameter D of recess 54 are selected to have an interference fit. The amount of interference is selected to provide a preselected amount of compression on insert ring 46 after it has been assembled within recess 54. The amount of such compression is to be sufficient to maintain insert ring 46 in compression during all operations including shearing of wire line 50 or a tubular members (not shown) which may be extending through valve 10 when it is to be closed. The reason for placing insert ring 46 in compression is that it is made of a brittle material, such as tungsten carbide or other suitable hard material, which has little strength in tension. By preloading insert ring 46 with sufficient compression to ensure that it is never placed in tension, insert ring 46 is never exposed to conditions which would result in its failure, such as a chipping of its shearing edges. It is suggested that assembly of insert ring 46 with seat ring 34 be accomplished with seat ring 34 heated sufficiently to allow insertion of insert ring 46 without undue loading of either component during assembly. After seat ring 34 has cooled with insert ring 46 positioned in its recess 54, seat ring 34 will shrink sufficiently to provide the desired compression preload of insert ring 46. The compressive preload on insert rings 46 and 48 is sufficient to ensure that there is no relative movement of the insert rings and seat rings 34 and 36 during operation of the gate valve. Groove 60 is provided to allow the seat ring to be removed from the body by prying with a screw driver or similar tool. 
     As shown in FIGS. 4 and 5, gate 32 is a generally flat elongated plate and includes means 66 for suitable connection to connecting rod 30 and opening 42 in which sleeve 44 of hardened material is positioned. Sleeve 44 is made of the same or similar material to the material of insert ring 46. The inner diameter of opening 42 is sized with respect to the external diameter of sleeve 44 so that on insertion of sleeve 44 therein (by a shrink fit), it is preloaded with sufficient compression preloading to ensure that it will not be loaded in tension during its use. This is done, preferably in the same manner as the assembly of insert ring 46 within seat ring 34. Gate 32 is heated sufficiently to allow sleeve 44 to be readily inserted into opening 42. The diameter of opening 42 is sufficiently smaller after cooling than the outer diameter of sleeve 44 to provide the desired preselected compression preload on sleeve 44. This will ensure that during all operations of gate 32, sleeve 44 will be under compression and will perform its sealing and shearing functions without destruction, chipping or other damage thereto. The compressive preload on sleeve 44 is sufficient to ensure that there is no relative movement between sleeve 44 and gate 32 during operation of gate valve 10. 
     Testing of a 2 9/16 inch, 15,000 psi model of the improved design shearing gate valve has resulted as follows: 
     
         ______________________________________Size     Type              Times Cut______________________________________.082&#34;    Solid Wire        2.092&#34;    Solid Wire        3.108&#34;    Solid Wire        7.188&#34;    Stranded Wire     8.219&#34;    Stranded Logging Cable                      3.250&#34;    Stranded Logging Cable                      2.469&#34;    Stranded Logging Cable                      3.188&#34;    Stranded, Bundle of 12                      11.00&#34;    .095&#34; Wall Tubing 11.25&#34;    .109&#34; Wall Tubing 21.75&#34;    .109&#34; Wall Tubing 1.469&#34;    Stranded Logging Cable                      1    Inside 1.0&#34; × .095&#34; Tubing.469&#34;    Stranded Logging Cable                      2    Inside 1.25&#34; × .095&#34; Tubing______________________________________ 
    
     The valve was tested to full rated working pressure of 15,000 psi after each shearing with no detectable leakage. 
     From the above it can be seen that the improved design of the shearing gate valve of the present invention provides a gate valve which can shear a wire line or other tubular member extending therethrough without damage to the hardened inserts 46 and 48 and the hardened sleeve 44 or in any way interfering with the sealing of the gate and the seat rings. This allows the valve 10 to be used without repair or replacement through many cycles of closing and shearing whereas shearing gate valves of the prior art could only be expected to accomplish a single shearing and even following such single shearing may have been damaged sufficiently to provide an imperfect seal.