Abstract:
A valve seat ( 10 ) for use in a valve incorporating a valve gate is disclosed, the valve seat comprising a valve seat body ( 12 ) and a biasing device ( 14 ) such as a spring ( 14 ), the biasing device being integral with the valve seat body. The biasing device and valve seat body may be welded together or may be formed in a single metal workpiece by a machining, casting or forging process. The valve gate and valve seat cooperate to form a metal-to-metal seal within the valve. At least a portion ( 15 ) of the valve seat is typically welded to at least a portion of the valve. A pipeline including at least one valve is also disclosed, as is a method of fitting a valve seat to a valve.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a valve, especially a valve suitable for pipelines, and more particularly pipeline used for the transportation of oil and gas. The present invention covers the valve itself, and a method for fitting the valve into a pipeline. 
       BACKGROUND OF THE INVENTION 
       [0002]    Valves are useful components in the control of fluid flow, and allow the fluids to be redirected, the flow-rate to be changed or the fluid blocked entirely from flowing. 
         [0003]    In oil and gas pipeline applications, a common type of valve used is the so called gate valve. These generally comprise a fluid inlet, a fluid outlet, and a moveable member or gate deployed there between. The gate can be selectively moved between the fluid inlets and fluid outlets to progressively decrease and then block fluid communication of the two. Often, the gate may be provided with an aperture, and it is the movement of the aperture which is key to the control of fluid flow, as it may be moved directly between the fluid inlet and fluid outlet to provide a fully open position, and progressively out of line with the fluid inlet and fluid outlet to steadily decrease fluid flow, to eventually being moved completely out of line with the two to fully block the fluid flow by providing a barrier between the fluid inlet and fluid outlet. 
         [0004]    Valves and pipelines of the type under consideration will be formed from several components joined to one another by suitable means, for example being bolted or welded together. These joins provide a possibility of leakages being found within an operational system. 
         [0005]    A valve will typically comprise a valve body, a moveable gate often connected to a control means via rod, and a pair of valve seats. The valve seats are generally annular and are placed within enlarged diameter portions of the through-bore of the valve body, one valve seat being provided on the fluid inlet and the other valve seat located on the fluid outlet side of the gate, and the through-bore of the valve body leading away from each valve seat leads to a flange that connects to a corresponding pipe for fluid transport. 
         [0006]    In oil and gas pipeline applications, the fluids will generally be at elevated pressures and/or temperatures. When the gate is in a fully closed position, the fluid inlet pipe will continue to supply fluid and therefore apply a pressure to the valve gate. Since the valve gate and valve seat have to be separate components to allow for the relative movement of the two, an imperfect seal may be at the junction of the two allowing for undesirable leakage. This leakage may flow up between valve seat and valve gate, and then between valve seat and pipe and/or valve seat and valve body, and out of the valve itself. This is obviously undesirable given the potentially hazardous nature of the fluid being transported. 
         [0007]    Several prior art solutions exist to mitigate this problem. The first is simple use of elastomeric seals at these junctions. Elastomeric seals may be compressed between components where leakages are likely to occur, and their tendency to bias against both components increases seal efficiency. They are not without their drawback too however, as they tend to perish and require replacement, and also limit working fluid temperature and pressures within the pipeline systems. Typically, non-metallic such as elastomeric seals will limit the working temperature to about 350° Celsius. 
         [0008]    Another is the use of a biasing means, usually a metallic seal ring located between the valve body and a rear face of the valve seat, to bias the valve seat against the valve gate. However, non-metallic radial seals are still required to seal the valve at the junction between the valve seat and the valve body to mitigate leakage. However, this brings the disadvantages associated with the use of non-metallic seals described above. 
       SUMMARY OF THE INVENTION 
       [0009]    According to a first aspect of the present invention there is provided a valve seat comprising a valve seat body and a biasing device, the biasing device being integral with the valve seat body. By integral it will be understood that there is a join between said biasing device and valve seat body, said join being achieved by such attachment methods as welding, or indeed being integrally cast or machined as a single piece. The welding technique may be spot, frictional, arc, laser, electron beam, resistance, flash, or any other technique deemed suitable for the process. 
         [0010]    Preferably the biasing device and valve seat body are welded together, but may alternatively be formed from a single metal workpiece put through a forming process such as machining, casting or forging. 
         [0011]    Preferably said biasing device comprises a spring, more preferably an annular spring. 
         [0012]    Preferably said biasing device comprises an annular sigmoidal spring. 
         [0013]    Preferably said annular sigmoidal spring is provided with at least one substantially circular chamfer between two perpendicularly connected sections thereof. 
         [0014]    Preferably all perpendicularly connected sections of the sigmoidal spring are connected via substantially circular chamfers. 
         [0015]    Preferably a chamfer is provided between an external side wall and an end face of the valve seat, more preferably two chamfers are provided at both end faces and the external side wall of said valve seat. 
         [0016]    Preferably the valve seat comprises a metal. More preferably a metal selected from the group consisting of the group of stainless steel and INCONEL (Trade Mark). 
         [0017]    Preferably the valve seat body further includes a radially projecting abutment. This radially projecting abutment would be cooperable with a shoulder provided within a suitable valve and limit compression of the biasing device. 
         [0018]    Preferably the abutment is annular, disposed around the valve seat. 
         [0019]    Preferably the abutment is formed from a separate ring and groove arrangement. More preferably the ring is separate from the valve seat body and is formed from two semi-circles. 
         [0020]    According to a second aspect of the present invention there is provided a valve including a valve body and at least one valve seat according to a first aspect of the present invention. 
         [0021]    Preferably the valve further includes a valve gate, selectively movable from a closed position, where fluid communication through the valve is blocked, to an open position, where fluid communication through the valve is allowed. 
         [0022]    Preferably the valve gate and valve seat cooperate to form a metal-to-metal seal within the valve. This metal-to-metal seal would advantageously be formed in both the open and closed positions, and would provide effective sealing without the need for further sealing means such as elastomeric seals. 
         [0023]    Preferably the valve includes a biasing device shoulder cooperable with the biasing device of the at least one valve seat. Preferably the biasing device shoulder is annular, and cooperates with the annular biasing device. 
         [0024]    Preferably the valve includes an abutment shoulder cooperable with the radially projecting abutment of the at least one valve seat. Preferably the abutment shoulder is annular, and cooperates with an annular radially projecting abutment. 
         [0025]    Preferably the abutment shoulder and the radially projecting abutment cooperate to limit compression of the biasing device against the biasing device shoulder. In use, the biasing device would abut the biasing device shoulder first, upon compression of the biasing device through application of a fluid pressure resulting from the valve being in a closed position, a point would be reached where the radially projecting abutment abutted the abutment shoulder, mitigating further compression of the biasing device. 
         [0026]    Preferably the valve seat is welded to the valve body. 
         [0027]    According to a third aspect of the present invention there is provided a pipeline including at least one valve according to the second aspect of the present invention. 
         [0028]    According to a fourth aspect of the present invention there is provided a method of fitting a valve seat to a valve, said valve seat comprising a valve seat body, a biasing device integral with the valve seat body, a removable abutment and abutment housing; the valve including an abutment shoulder and a biasing device shoulder, the method comprising the steps of partially placing the valve seat within the valve, placing the removable abutment within the abutment housing, and fully placing the valve seat within the valve such that the biasing device abuts the biasing device shoulder. It is preferable that the abutment would be a short distance from full abutment with the abutment shoulder, that short distance defining a compression limit for the biasing device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    Reference will now be made, by way of example only, to the accompanying drawings, in which: 
           [0030]      FIG. 1  is a side sectional view of a valve seat according to a first aspect of the present invention; 
           [0031]      FIG. 2  is side sectional detail view of the biasing device of the valve seat of  FIG. 1 ; 
           [0032]      FIG. 3  is a plan view of a valve according to a second aspect of the present invention; 
           [0033]      FIG. 4  is a side elevation of the valve of  FIG. 3 ; 
           [0034]      FIG. 5  is an end elevation of the valve of  FIG. 3 ; 
           [0035]      FIG. 6  is sectional side elevation of the valve of  FIG. 3 ; 
           [0036]      FIG. 7  is a detail view of portion BB highlighted in  FIG. 6 ; 
           [0037]      FIG. 8  is an end elevation of a stop-ring of the valve of  FIG. 3 ; and 
           [0038]      FIG. 9  is a part section side elevation of the stop-ring of  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0039]    A valve seat  10  formed of metal such as stainless steel or ICONEL (Trade Mark) according to the first aspect of the present invention is shown in cross-section in  FIG. 1 . It comprises a valve seat body  12  and a biasing device  14 . The two parts are formed integrally, in this case manufactured by forming the parts separately, before welding the valve seat body  12  permanently to the biasing device  14 . Alternatively, the valve seat body  12  and the biasing device  14  can be manufactured from one piece of metal. 
         [0040]    The valve seat body  12 , and by extension the valve seat  10  itself, is generally cylindrical, and includes an outer sidewall  16  and a front end face  18 . The sidewall  16  and end face  18  are connected via a chamfered shoulder  20 . Disposed approximately half-way along the sidewall  16  is a circumferential groove  22 , which extends around the exterior surface of the valve seat  10 , and disposed in a plane perpendicular to the dominant central axis  10   a  of the valve seat  10 . 
         [0041]    The biasing device  14  comprises a generally annular sigmoidal spring, further detail of which can be viewed in  FIG. 2 . The biasing device  14  is formed from a first annular portion  24 , connected through a first web section  26  to a second annular portion  28 , which in turn connects through a second web section  30  to a third annular portion  32 . 
         [0042]    Being integrally formed with the valve seat body  12 , the first annular portion  24  and valve seat body  12  are contiguous. The first web section  26  and second web section  30  attach to the second annular portion  28 , respectively, at inner and outer radial extremes, thus forming a sigmoid cross-section. The various sections are contiguous and the connecting surfaces of respective sections and webs are circularly chamfered on the inner surfaces thereof. This chamfering mitigates stress concentration points which could lead to an undesirable permanent plastic deformation of the biasing device. On the outer surface second of the join between web section  30  to third annular portion  32  is a further chamfer  33 . 
         [0043]    Turning to  FIGS. 3 to 5 , various external views of a valve  100  according to a second aspect of the present invention are shown. In  FIG. 3 , inner portions of two valve seats  10  can be viewed. 
         [0044]    The valve  100  comprises a valve body  102  formed of metal such as stainless steel or ICONEL (Trade Mark). The valve body  102  is substantially a conical frustum, with the smaller face (and bottom  104  of the valve body  102 ) of which being rounded, and connected to the valve sidewall  106  via a circular chamfer. The opposite, larger face defines a top connection flange  108 , with a top aperture  110  defined therein. The valve sidewall  106  connects to the top connection flange  108  via a square chamfer. 
         [0045]    Extending radially outward from the valve sidewall  106 , on opposite sides thereof, are two pipe inlets  112 . The pipe inlets  112  each connect to pipe connection flanges  114 . The connection planes of the pipe connection flanges  114  are perpendicular to the connection plane of the top connection flange  108 . Each pipe connection flange  114  defines a pipe inlet aperture  116  at its centre. 
         [0046]      FIG. 6  is a sectional side elevation of the valve  100  showing interior detail. The valve body  102  has three bores defined therein: a top bore  118  which extends from the top aperture  108  down into the valve body  102  towards the bottom  104  but terminating before intersection therewith. Perpendicular to said top bore  118  are two pipe inlet bores  120 , which extend from respective pipe inlet apertures  116  towards the opposite pipe inlet aperture. The two pipe inlet bores  120  intercept the top bore  118 , with a direct path being formed between the two pipe inlet bores  120 . The top bore  118  extends somewhat below the intersection of the two pipe inlet bores  120 , and thus a generally cruciform chamber is formed, albeit that only three of the four prongs of the cruciform chamber communicate externally of the valve  102 , via top bore  118  and pipe inlet bores  120 . 
         [0047]    At the junction of each of the pipe inlet bores  120  and the top bore  118 , two greater diameter shoulders are formed: a stop-ring shoulder  122  and a biasing device shoulder  124 . From the direction of the top bore  118  through to the pipe inlet bore  120 , the stop-ring shoulder  122  is first and has the greater diameter of the two, followed by the biasing device shoulder  124 , with the lesser diameter of the two. Thus, two “steps” are formed, decreasing in diameter to the diameter of the pipe inlet through-bore  120 . A chamfer  119  is provided between top bore  118  and the stop-ring shoulder  122 . 
         [0048]    A valve seat  10  according to the first aspect of the present invention is deployed at the junction between the top bore  118  and each of the pipe inlet bores  120 . 
         [0049]    The inner diameter of the biasing device shoulder  124  is only slightly greater than the outer diameter of the biasing device  14  itself, thus a tight, but sliding fit is created, with the third annular portion  32  abutting the terminating portion of the biasing device shoulder  124  once the biasing device  14  is located in its in use position as will be described in more detail subsequently 
         [0050]    A stop-ring  126  is also provided. The stop-ring  126  is annular with an L-shaped profile, having a greater thickness section  126   a  and a smaller thickness section  126   b . The external diameter of both of these sections is identical, but the inner diameter of the greater thickness section  126   a  is less than that of the smaller thickness section  126   b . A stop-ring lip  126   c  is therefore defined. Further detail of the stop-ring  126  is shown in  FIGS. 8 &amp; 9 . The stop-ring  126  is formed in two halves, being two substantially identical semi-circles. 
         [0051]    During location of the valve seat  10 , it is inserted into the valve  100  via the top aperture  108  and is placed partially within the junction between the pipe inlet bore  120  and the top bore  118 . Chamfer  33  aids in this placement. One half of the stop-ring  126  is then placed around the valve seat with the stop-ring lip  126   c  being placed within the circumferential groove  22 . The other half stop-ring  126  is similarly located within the other half of the circumferential groove  22 . The valve seat  10  is then pushed toward and into the pipe inlet bore  120 . 
         [0052]    As shown in  FIG. 7 , the stop-ring lip  126   c  is deployed within the circumferential groove  22 , with the smaller thickness section  126   b  being deployed towards the biasing device  14  end of the valve seat  10 . The stop-ring  126  is deployed within the stop-ring shoulder  122 , although the end face of the smaller thickness section  126  stands proud of the terminating portion of the stop-ring shoulder  122  by a short distance. Therefore, there is a small gap between the end face of the smaller thickness section  126  and the terminating portion of the stop-ring shoulder  122 . This gap will be typically in the range of about 0.1 to 0.3 mm, depending on various factors including manufacturing tolerances. 
         [0053]    The valve seat  10  is then permanently secured in place by welding corner  15  on the through-bore of the valve seat  10  to corner  150  of the through-bore of the pipe inlet bore  120 . In use, a suitable valve actuator (not shown) would be attached to the top of the valve  100  via the top connection flange  108 . A valve gate (not shown) typically formed from a metal such as stainless steel or ICONEL (Trade Mark) would extend down through the top bore  118 , and be located between the two pipe inlet bores  120  and valve seats  10 . A tight, but sliding fit, between valve gate and valve seats  10  is preferred, such that the biasing device  14  is in some compression. 
         [0054]    The valve gate is selectively movable and may be provided with a valve gate aperture (not shown) to allow for control of the extent of fluid communication between the two pipe inlet bores  120 . Alternatively, the valve gate may be a largely solid member with the end thereof passing between two pipe inlet bores  120  and valve seats  10  to control the extent of fluid communication. 
         [0055]    In an open position, the valve gate would be at a position where the gate aperture would be deployed directly between the two pipe inlet bores  120  and valve seats  10 , allowing fluid communication between the two. For illustration purposes from the perspective of  FIGS. 6 and 7 , it will be assumed that the fluid is flowing from left to right. Thus a net pressure exists in that direction. In any event, the end front face  18  of each valve seat  10  is compressed against the respective face of the gate valve around the aperture therein by the biasing force provided by the biasing device  14 , and thus a metal-to-metal seal is provided. 
         [0056]    As the actuator closes the valve by moving the gate aperture out of position, the effective cross-sectional area available for fluid flow decreases before becoming zero, when the valve is fully closed. Since there is still an upstream pressure acting upon the fluid, the fluid entering the valve  100  from the left hand pipe inlet bore  120  through the left hand valve seat  10 , will exert a force upon the valve gate as a result of the fluid pressure. In this embodiment, the various components are metal, so there is a limited but appreciable resilience in the various components. Thus, the valve gate pushes against the right hand valve seat  10  (see  FIG. 7 ) via the end face  18 . 
         [0057]    Again, being a metal with a limited but appreciable resilience and because of the resilience of the biasing device  14 , the third annular portion  32  of the biasing device  14  will be forced further against the terminating portion of the biasing device shoulder  124 , and the biasing device  14  will further compress. 
         [0058]    As the biasing device  14  is being compressed, the smaller thickness section  126   b  of the stop-ring  126  moves towards the stop-ring shoulder  122 , eventually being in abutment with it. At this point, the fluid pressure is acting against both the reaction force of the biasing device  14  acting against the biasing device shoulder  124  and the reaction force of the stop-ring  126  acting against the stop-ring shoulder  122 . Since the stop-ring  126  is of greater thickness and its design does not, in contrast to the biasing device  14 , lend itself to adding further resilience to itself over that found in the material itself, the stop-ring  126  acts as a limiter to the compression of the biasing device  14 . In other words, further compression of the biasing device  14  is retarded by the stop-ring  126  abutting the stop-ring shoulder  122 . 
         [0059]    Since valve seat body  12  and biasing device  14  are integral, and a complete seal is provided by the welding between the corner  15  of the biasing device  14  and the corner  150  around the inner circumference of the biasing device shoulder  124 , fluid is mitigated from travelling outside the through-bore of the two pipe inlet bores  120  more so than prior art solutions. Further, elastomeric seals are not required at any point in communication with through-bore fluid within the valve  100 , eliminating the disadvantages associated with their use. 
         [0060]    Modifications and improvements can be made to the embodiments herein before described without departing from the scope of the invention. 
         [0061]    For example, instead of a two-piece stop-ring, the stop-ring may be formed in one piece, perhaps with a gap provided at a point on the circumference to aid manipulation and fitting. Further, the stop-ring and groove arrangement may be replaced with an integral lip extending radially from the valve seat body  12 . 
         [0062]    The biasing device need not be sigmoidal, but may be a simpler or more complex arrangement, for example a Z-shaped arrangement. 
         [0063]    Stainless steel or ICONEL (Trade Mark) material may be replaced with a lower grade ferrous (or indeed non-ferrous) material in applications that do not require high-grade, corrosion resistant metals. 
         [0064]    As well as the common linear actuator using a rising stem indicator arrangement that would typically attach to the valve  100  via a non-metallic seal, the present invention may also be mated to a rotary actuator driving a non-rising stem. In this way a metal to metal seal can replace the non-metallic stem seal associated with the more normal rising stem arrangement. In this way the potential upper temperature ceiling at which the valve  100  can operate may be further increased. With no non-metallic seals, the next threshold in terms of a temperature barrier becomes the metal tempering range. With a suitable margin in place between the operating temperature and the tempering range of the metals, this will increase the maximum operating temperature normally associated with API gate valve from around 350° F. to around 750° F.