CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from South African patent application number 2019/07706 filed on 21 November 2019.

FIELD OF THE INVENTION

The invention disclosed herein relates to gate valves. It may find particular application, although by no means exclusively, with gate valves for use in water supply systems.

BACKGROUND TO THE INVENTION

Gate valves are widely used for all types of fluid-distribution applications and are suitable for both above-ground and underground installations. Gate valves are designed for fully open or fully closed service and as such are suitable for use as isolating valves, i.e. to completely shut off the flow of the relevant fluid, rather than as control or regulating valves. A gate valve offers various advantages. For example, a gate valve is a multi-turn valve and, since the valve has to turn multiple times to go from open to closed position, the slow operation also may reduce water hammer effects to name one advantage.

The gate of the valve is actuated through the rotation of the valve stem (in the case of a non-rising spindle valve) or nut (in the case of a rising spindle valve), either in a “clockwise to close” (CTC) or a “clockwise to open” (CTO) configuration. When operating the valve stem as aforesaid, the gate moves upwards or downwards on the threaded part of the stem to thereby open or close the valve, as the case may be. In the case of a rising spindle valve, the gate is raised by moving the shaft upwards through the valve bonnet.

Gate valves are often used when minimum pressure loss and a free bore is needed. When fully open, a typical gate valve has little to no obstruction in the flow path resulting in a very low pressure loss, and provides minimal flow resistance. This also allows the use of a so-called pipe cleaning pig to clean pipelines.

An example of a known gate valve known as a wedge gate valve (10) is shown in Figure 1 . The gate valve (10) includes a gate body (12) an inlet (14) and an outlet (16) with a flow path (18) extending between the inlet and the outlet. The gate valve (10) further includes a gate (20) formed from a rigid material, in this case steel, that has a frustoconical or wedge-shaped side-profile. A seat cavity (22) is formed in the valve body (12) and is formed and shaped so that, with the gate (20) in a closed condition, a bottom end (24) of the gate locates and seats within the seat cavity (22) to form a fluid-tight seal. The angular, wedge-shaped design of the gate (20) and the complementary shaped seat cavity (22) cooperate to form a tight seal when the gate is in the closed configuration.

However, and as more clearly shown in Figure 2, one of the disadvantages of this design is that debris and sand (26) tend to accumulate in the seat cavity (22), with the flow through the valve not quite being able to flush the debris completely from the valve once the valve is opened. Eventually, the accumulation of debris (26) in the seat cavity (22) may become sufficiently abundant so that the rigid wedge gate (20) loses its ability to fully seat into the body seal rings, preventing it from forming a proper seal.

The Application considers there to be scope for improvement.

The preceding discussion of the background to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was part of the common general knowledge in the art as at the priority date of the application.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the invention there is provided a gate valve comprising: a valve body having an inlet and an outlet with a central bore extending between the inlet and the outlet defining a flow path; and a rigid wedge gate operable to move along an axis transverse the flow path between an open condition in which the gate is at least partially retracted from the flow path, and a closed condition in which the gate obstructs the flow path, wherein an inner surface of the central bore is provided with a seat cavity in which an insert is set having a mechanical biasing force acting thereon such that, with the gate in the closed condition, the gate seats against a face of the insert; and such that, with the gate in the open condition, the biasing force urges the insert into a position in which the insert substantially fills the seat cavity and is substantially flush with the inner surface so as to form a substantially smooth central bore.

With the gate in the closed condition, the insert may be at least partially urged into the seat cavity against the biasing force due to a force exerted thereon by the gate. The insert may comprise a resilient material, wherein the resilient material is resiliently deformable such that, with the gate in the closed condition and seated against the face of the resilient material, the resilient material may be at least partially compressed and the insert urged into the seat cavity due to a force exerted thereon by the gate, and wherein the biasing force may be at least in part provided by the compressed resilient material.

The resilient material may reassume its original form when the gate is operated from the closed to the open condition so that the insert may substantially fill the seat cavity.

The resilient material may be a rubber material.

The insert may include a layer of a rigid material that forms the face of the insert.

The resilient material of the insert may be manufactured separately and the insert shaped and formed to fit in the seat cavity.

The insert may be arcuate in shape and may have a substantially half-ring shape in plan view.

The resilient material of the insert may be a castable material set in situ in the seat cavity and allowed to set therein.

The gate valve may include one or more compression spring arranged to at least in part provide the biasing force.

In accordance with a second aspect of the invention there is provided a method for retrofitting a gate valve, the gate valve including a valve body having an inlet and an outlet with a central bore extending between the inlet and the outlet defining a flow path, the central bore being provided with a seat cavity within which a rigid wedge gate of the valve seats when in a closed condition, the method comprising: opening the valve body and removing the rigid wedge gate thereby exposing the seat cavity; setting an insert in the seat cavity with the insert a mechanical biasing force acting thereon that urges the insert into a position in which the insert substantially fills the seat cavity; replacing the rigid wedge gate; and closing the valve body, whereby an inner surface of the central bore is provided with a seat cavity in which the insert is set such that, with the gate in the closed condition, the gate seats against a face of the insert; and such that, with the gate in an opened condition the insert substantially fills the seat cavity.

The insert may be set in the seat cavity such that, with the gate in the open condition, the biasing force may urge the insert into a position in which the insert may substantially fill the seat cavity and may be substantially flush with the inner surface so as to form a substantially smooth central bore.

The insert may be set in the seat cavity such that, with the gate in the closed condition, the insert may be at least partially urged into the seat cavity against the biasing force due to a force exerted thereon by the gate.

The insert may comprise a preformed resilient material that is shaped and formed to fit in the seat cavity, and the step of setting the insert in the seat cavity may include setting the preformed insert in the seat cavity.

The step of setting the insert in the seat cavity may include filling the seat cavity with a castable material that when set forms a resilient material, and allowing the castable material to set.

The insert may further include a layer of a rigid material that forms the face of the insert.

In accordance with a third aspect of the invention there is provided a kit for retrofitting a gate valve, the kit including: a gate valve with a valve body having an inlet and an outlet with a central bore extending between the inlet and the outlet defining a flow path, the central bore being provided with a seat cavity within which a rigid wedge gate of the valve seats when in a closed condition; and an insert shaped and formed to be set in the seat cavity and so as to have a mechanical biasing force acting thereon such that with the gate in the closed condition, the gate seats against a face of the insert; and such that, with the gate in an open condition, the biasing force urges the insert into a position in which the insert substantially fills the seat cavity.

The insert may be shaped and formed to be set in the seat cavity such that, with the gate in the open condition, the biasing force may urge the insert into a position in which the insert substantially fills the seat cavity and is substantially flush with an inner surface of the central bore so as to form a substantially smooth central bore.

The insert may comprise a preformed resilient material, the resilient material being resiliently deformable such that, with the gate in the closed condition and seated against the face of the insert, the resilient material may be at least partially compressed and the insert urged into the seat cavity due to a force exerted thereon by the gate, and the biasing force may be at least in part provided by the compressed resilient material.

In accordance with a fourth aspect of the invention there is provided an insert shaped and formed to be set in a seat cavity of a rigid wedge gate valve, the valve having with a valve body with an inlet and an outlet and a central bore extending between the inlet and the outlet defining a flow path, the seat cavity being provided in the central bore within which a rigid wedge gate of the valve seats when in a closed condition, wherein the preformed insert is shaped and configured to, when set in the seat cavity, have a mechanical biasing force acting thereon such that with the gate in the closed condition, the gate seats against a face of the insert; and such that, with the gate in an open condition, the biasing force urges the insert into a position in which the insert substantially fills the seat cavity.

The insert may be a preformed insert comprising a resilient material shaped and formed to be set in the seat cavity.

The insert may be shaped and configured to, when set in the seat cavity, enable the face of the insert to be substantially flush with an inner surface of a central bore of the gate valve so as to form a substantially smooth central bore when the gate is in an open configuration.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Figure 1 is prior art showing a section view of a known rigid wedge gate valve;

Figure 2 is the gate valve of Figure 1 showing debris accumulated in a seat cavity thereof;

Figure 3 is a section view of a rigid wedge gate valve with a gate of the valve in an open condition;

Figure 4 is a cut-away three-dimensional view of the valve of Figure 3; Figure 5 is a section view of a rigid wedge gate valve in accordance with the invention with the gate of the valve in a closed condition;

Figure 6 is a cut-away three-dimensional view of the valve of Figure 5;

Figures 7A - 7G are various views of a preformed resilient insert; Figure 8 is a flow diagram illustrating steps in a method for retrofitting a gate valve;

Figure 9 is a section view of a rigid wedge gate valve with a composite insert; Figure 10 is an enlarged view of the insert of the gate valve of Figure 9; Figure 11 is a section view of a rigid wedge gate valve with a rigid insert; and Figure 12 is an enlarged view of the insert of the gate valve of Figure 11 .

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

A rigid wedge gate valve is disclosed that has a valve body with an inlet and an outlet. The valve body is typically constructed from a metals or metal-alloys such steel, cast iron, Hastelloy, Inconel, Monel or Titanium. A central bore extends between the inlet and the outlet defining a flow path and typically, however not exclusively, has a substantially round cross-section. The inlet and outlet is typically also provided with a flange to allow the valve to be secured to pipes in a fluid- tight manner.

The gate valve has a rigid wedge gate that may be mechanically connected to a stem of the valve, with the stem operable to configure the gate between an open and a closed condition. The stem may itself, in turn, be actuated by means of a lever, handwheel, chainwheel, bevel gear, cylinder or electric motor. Exemplary rigid materials from which the wedge gate may be formed include metals or metal alloys (such as steel) or hard polymers (such as nylon).

The valve body is provided with a gate seat cavity opposite the stem in which the wedge gate seats when in the closed condition to form a seal. The wedge gate has non-parallel seat faces and, in section view, the gate tapers at least slightly from an upper end (i.e. the end near the stem) to a lower end (i.e. the end which seats in the seat cavity). The lower end of the wedge gate may have a frustoconical shape in section view.

The wedge valve is operable by means of the stem to move along an axis transverse the flow path (i.e. the axis of the stem) between an open condition in which the gate is at least partially retracted from the flow path, and a closed condition in which the gate seats in the seat cavity to obstruct the flow path.

The seat cavity is provided with an insert, set therein, that may be a resilient material, such as rubber. However, the insert may furthermore be a composite material. For example, it may partly comprise of a resilient material, and partly of a rigid material such as a metal. The resilient material may be a castable material, such as a castable urethane foam that may be poured in situ to fill the seat cavity and allowed to set therein, possibly requiring slight trimming or machining to obtain the required form and shape. Alternatively, a preformed insert may be used and press-fitted or set into the seat cavity. The preformed insert may be shaped and formed such that when set in the seat cavity, a face or outer edge (i.e. the face or edge exposed in the flow path) follows the contour of the flow path. For example, if the flow path has a round cross-section, the insert may be shaped and formed so that its face or outer edge substantially follows the contour of the flow path, thereby effectively filling up the cavity seat.

When inserted or set in the seat cavity, therefore, the insert converts the valve from having a seat cavity to having a smooth central bore (without a seat cavity). Of course, the same applies in the instance where the resilient material of the insert has been poured in the seat cavity and trimmed or machined to leave the central bore with a smooth inner surface (i.e. the seat cavity filled).

When the central bore is referred to as “smooth” when the insert is set in the seat cavity, it should be interpreted to mean that it fills the seat cavity. Depending on tolerances, the effects of temperature, and the presence of other structures in the valve (such as seat rings) the central bore may have certain protrusions. However, the indent otherwise formed in the valve body by the seat cavity will be substantially filled with the insert.

The insert has a mechanical biasing force acting thereon. This biasing force may be provided by the properties of the material from which the insert is manufactured. For example, if the insert is manufactured from a resilient material such as rubber, the biasing force may be provided by the resilience of the material itself. If the resilient material is compressed, it will exert a force that urges the insert back into its uncompressed, resting or original shape. Thereby, with the gate in the closed condition, the gate seats against the face of the insert and compresses resilient part of the insert. However, when the gate again opens, the resilience of the resilient part exerts its biasing force to urge the face of the insert back into its resting or original position in which it substantially fills the seat cavity.

In other embodiments, the biasing force may be provided by compression springs (optionally in addition to a resilient material). For example, the compression springs may be located in the seat cavity with the insert set intermediate the springs and the gate. Thereby, with the gate in the closed condition, the gate seats against the face of the insert and compresses the springs. However, when the gate again opens, the force for the compressed springs urges the face of the insert back into its resting or original position in which it substantially fills the seat cavity.

As aforementioned, when the wedge gate is in the closed condition, the gate seats against the face of the insert. Due to the biasing force (e.g. the resilience of the material), if sufficient force is applied to the stem, the tip of the gate will force the insert into the cavity in which it is set. This may produce a tighter seal. What is more, should any residue or debris lie atop the insert, i.e. intermediate the insert and the gate when the gate is closed thereon, the biasing force will return the face of the insert to its original position, filling the seat cavity, and pushing the debris into the flow path, allowing it to be flushed away.

In embodiments in which the face of the insert is a resilient material, the resilience of the resilient material will at least partly assume the form of the debris and form a seal (notwithstanding the presence of the debris) when the gate is closed thereon. When the wedge gate is operated from the closed to the open condition, the resilience of the resilient material will cause it to reassume its original form, i.e. to be substantially flush with the inner surface of the central bore such that the central bore has a substantially smooth surface. Any debris that may have been caught between the gate and the resilient material may be pushed into the flow path when the resilient material reassumes its original form, allowing the debris to be flushed out.

Different applications for a particular gate valve may require an insert of a particular material. For example, instances where the gate valve is to be used in a water pipeline, the temperatures that the valve would endure would be low enough to allow the insert to be (at least partially) a resilient material, such as rubber.

For other uses, for example in petroleum pipelines, the temperature and the reactivity of the fluid may require the insert to be rigid (e.g. steel) and for the biasing force to be provided by compression springs.

Other uses may require a composite insert, i.e. having a resilient and a rigid material therein and optionally having the biasing force at least partially provided by one of more compression springs. Figures 3 to 6 show an exemplary embodiment of a solid wedge gate valve (100) in accordance with the invention.

The valve (100) has a carbon steel valve body (112) with an inlet (114) and an outlet (116) on opposite sides of a central bore (118) extending through the valve. A flow path (120) for a fluid is generally defined along the central bore (118) between the inlet (114) and outlet (116). However, the valve allows bidirectional flow and the inlet (114) and outlet (116) are therefore interchangeable.

The inlet (114) and outlet (116) are each provided with a flange (115, 117) shaped and configured to allow the valve (100) to be interconnected to corresponding flanges on pipes (119) with bolts (120) as shown in Figure 4.

A bonnet (121) sits atop the valve body (112) in which a valve stem (122) is rotatably secured. A lower section of the valve stem (122) is threaded (123) and a rigid wedge gate (124) is threaded onto the threaded section (123) of the valve stem (123). As more clearly shown in Figure 4, the gate has a generally circular profile when viewed from either the inlet (114) or outlet (116). However, in cross-section as shown in Figure 3, the gate is seen to have angular, non-parallel faces (126) which characterises a wedge gate valve. The wedge gate (124) tapers from where it is mounted on the stem (124) towards its free end (127).

The valve further includes a hand wheel (130) that is operable to rotate the valve stem (122), which translates into movement of the wedge gate (124) along an axis (128) corresponding to a central axis of the stem (122) on the threaded section (123) of the stem (122).

Figures 3 and 4 show the gate valve (100) in an open configuration, i.e. in which the wedge gate (124) is retracted from the flow path (120) into the bonnet (121).

The valve body (112) includes a cavity (132) sunken into a periphery of the central bore (118) that is positioned axially in line with the valve stem (122). A resilient insert (140), manufactured from a rubber material in the present embodiment, is set into the cavity (132) such that an exposed face (146) of the insert completely fills the cavity (132) and follows the contour of the central bore (118). With the resilient insert (140) filling the cavity (132), the central bore (118) is rendered substantially smooth or uninterrupted, i.e. without a cavity (except for the bonnet (121) into which the gate (124) is retracted when in the open condition). From the section view of Figure 3 the resilient insert (140) may appear to be substantially flat. Flowever, from the partial cut-away view shown in Figure 4 it is clearer that the resilient insert is in fact generally arcuate in shape, to fit the arcuate cavity (140) into which it is set.

Figures 5 and 6 show the gate valve (100) in a closed configuration. In this configuration, handwheel (130) and in turn the stem (122) have been turned to lower the gate (124) to obstruct the flow path (120). In this closed configuration, the free end (127) of the gate presses or seats against the exposed face (146) of the insert (140). Due to the resilience of the insert (140), and depending on how tight the valve gate (124) is closed, resilient material may compress so that the free end (127) of the gate (124) extends somewhat into the cavity (140). This may serve to provide a superior fluid-tight seal.

Any debris that may have been caught between the free end (127) of the gate (124) and the exposed face (146) of the insert (140) will have a much less (if any) effect on the sealing capability of the valve, since the shape of the resilient insert (140) will conform to the contours of the debris.

When the valve is again opened, i.e. operated to be in the open configuration as shown in Figures 3 and 4, any such debris material may be pushed into the flow path when the resilient material reassumes its original form, allowing the debris to be flushed out.

Figures 7A to 7G show various views of an example resilient insert (700), which has been shaped and formed to fit in a seat cavity of a particular model of rigid wedge gate valve. It will be appreciated that the shape and form of the insert may need to be adapted to be fit for purpose for different models of rigid wedge gate valves.

The embodiment of the insert (700) shown in Figures 7A to 7G is a separately manufactured insert of a rubber material. The insert (700) is generally arcuate in shape with a half-ring shape in plan view as shown in Figure 7A and 7D.

Vast quantities of conventional rigid wedge gate valves exist in the field, requiring periodic servicing to clean out debris from their seat cavities particularly once they start to lose their ability to form a proper seal. The invention therefore also provides for a method of retrofitting conventional wedge gate valves to convert them into a smooth bore gate valve in accordance with this invention.

A method (800) of retrofitting a conventional wedge gate valve (10) is explained with reference to the steps shown in Figure 8, and to the parts of a conventional valve (10) shown in Figures 1 and 2. The operator may remove (801) the bonnet (21) to open the valve body (12) and remove (802) the valve gate (20) thereby exposing the seat cavity (22). A resilient material is then set (803) in the seat cavity (22).

At this stage of retrofitting, the gate valve has been converted into a smooth bore wedge gate valve (100) in accordance with this invention, only requiring assembly. The remainder of the method is therefore explained with reference to the rigid wedge gate valve (100) shown in Figures 3 to 6.

The rigid wedge gate (124) is then replaced (804) and the bonnet (121) replaced and secured (804) thereby closing (805) the valve body (112).

Figure 9 and 10 show an embodiment of a rigid wedge gate valve in which the insert is a composite material. Like reference numerals used in Figure 9 and 10 correspond to like features of the gate valve shown in Figures 3 to 6.

In this embodiment, as more clearly shown in the enlarged view of Figure 10, the insert (940) is a composite insert that includes a resilient material part (942) set at the bottom of the seat cavity (132). The resilient material part may, for example, be a rubber material. The insert further includes a rigid part (944), for example a steel plate.

The mechanical biasing force in this embodiment is also provided by the resilience of the resilient material (942) and the face of the insert (940) is formed by the rigid part (944).

Figure 11 and 12 show a further embodiment of a rigid wedge gate valve in which the insert is a rigid material and in which the mechanical biasing force is provided by compression springs. Like reference numerals used in Figure 11 and 12 correspond to like features of the gate valve shown in Figures 3 to 6.

In this embodiment, as more clearly shown in the enlarged view of Figure 12, the insert (1140) is a rigid material (1142), for example steel. The mechanical biasing force is provided by compression springs (1142) set provided intermediate the rigid material (1144) and the bottom of the seat cavity (132).

The invention therefore provides for a rigid wedge gate valve that does not suffer from the defect of known wedge gate valves having deep seat cavities in which debris may accumulate. The insert provides for a tolerance of any debris that may be temporarily trapped between the gate and the insert, and allows the debris to be pushed into the flow when the gate is open to flush out any such debris. Throughout the specification and claims unless the context requires otherwise the word ‘comprise’ or variations such as ‘comprises’ or ‘comprising’ will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.