WO2019202525A1

WO2019202525A1 - Knife gate valve arrangement

Info

Publication number: WO2019202525A1
Application number: PCT/IB2019/053166
Authority: WO
Inventors: Johannes Gerhardus GREYLING
Original assignee: Sanspar Engineering Sales (Pty) Ltd
Priority date: 2018-04-17
Filing date: 2019-04-17
Publication date: 2019-10-24

Abstract

This invention relates to a knife gate valve arrangement. The knife gate valve arrangement comprises a valve body having an inlet and an outlet, and a flow passage extending between the inlet and the outlet. A valve seat is located in the passage, and a sliding gate valve member is located in the flow passage. The sliding gate valve member is slidingly displaceable relative to the valve seat between an open position, in which the gate valve member is at least partially removed from the passage, and a closed position, in which the gate valve member closes of the passage. The knife gate valve arrangement is characterised in that an actuator is provided on each side of the valve body, with the actuators engaging the gate valve member on both sides of the gate valve member when displacing the gate valve member between the open and closed positions when actuated.

Description

KNIFE GATE VALVE ARRANGEMENT

TECHNICAL FIELD

[0001] This invention relates to the field of mechanical valves, in general, and more specifically to a knife gate valve arrangement.

BACKGROUND ART

[0002] The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

[0003] Valves are well-known in the art and have been used since ancient times to regulate the movement of fluids in conduits. Valves are found in virtually every industrial process, including water and sewage processing, mining, power generation, processing of oil, gas and petroleum, food manufacturing, chemical and plastic manufacturing and many other fields. In processes involving the movement of abrasive or corrosive fluids, such as slurries, valves are required which removes the valve member or gate entirely from the path of the fluid flow to prevent abrasion of the valve member or gate. One such example is a knife gate valve. [0004] Knife gate valves were originally designed for the paper and pulp industries, as the design offered improved lifespan in slurry applications compared to gate, diaphragm and ball valves. Most problems related with knife gate valves are due to seat failure - a slurry by its nature is typically highly abrasive and in some process plants, slurry contains solid particles that can be as large as 25mm in diameter. Slurry is generally pumped in a pipeline at velocity, e.g. 3.5m/s, to avoid settling of particles in the pipeline. The combination suspended solids and slurry pumped at velocity generally means that pipeline equipment, such as valves, are constantly exposed to wear. As valves are used to control flow of a slurry, increases of slurry velocity during the closing stroke of the valve as the area available for flow decreases, increases the velocity of the slurry thus causing excessive wear during the opening and closing of valves.

[0005] Conventional thinking in addressing this problem was to use materials with higher wear resistance in the parts that is exposed to wear, but these materials are typically expensive, as well as difficult and costly to machine. The use of a so-called deflector cone has also been used by many manufacturers to deflect the slurry away from the seating area of a valve. These defector cones have a conical shape and is generally installed on the upstream side of the valve. Although somewhat effective in some instances, these defector cones often cause turbulence and localized wear in a different part of the valve or downstream pipeline.

[0006] Another conventional approach to addressing the problem of knife gate wear, is to incorporate a valve body design that offers a full-bore design, wherein the internal diameter of the valve is the same as the inside diameter of the mating pipe. In this manner, no part of the valve interferes with the slurry's flow path and no valve parts collide with the slurry particles, which reduces wear. Such conventional knife gates use two rubber sleeves compressed together, with the gate having a sharp edge, i.e. like a‘knife’ which slides between the two rubber sleeves from top to bottom until the flow path is fully obstructed and flow is prevented.

[0007] This sleeved type knife gate design is commonplace for most slurry applications; however, the design still has shortcomings. The sleeved type design normally consists of a single unitary valve body casting or two mirror castings bolted together, with two sleeves compressed together with compression flanges (some designs rely on the adjacent pipe flanges to compress the sleeves). A conventional valve will also typically have a stem or yoke and an actuator for displacing the knife gate, e.g. a hand wheel, a pneumatic or hydraulic cylinder, an electromechanical actuator, etc.

[0008] One shortcoming with such conventional knife gate valves is seat failure, where the valve seat cannot stand up to the solid and large particles that is forced into the seat during the closing stroke of the valve. Often a‘bedrock’ is formed in slurry pipelines due to a combination of particle size and lower velocities. The gate then has to‘cut’ through this bedrock or accretion layer or particles which may cause damage the rubber seats. This also leads to the valve not being able to close fully, which may cause unscheduled operational downtime.

[0009] Many examples of conventional knife gate valves‘purge’ during the closing stroke at the leading edge of the gate where the gate separates the sleeves - there is typically a small opening in front of the gate edge. Particles often become lodged between the two sleeves, thus resulting in an opening that causes a leak. Consequential damage is caused by the slurry further eroding the seats and gate, and often also the body, as extreme velocities occur in these instances when the fluid flowing through the small opening.

[0010] A further shortcoming is that slurry build-up occurs in the body cavity over time and then causes valve failure. Every time the valve opens, a thin layer of slurry remains in the valve body cavity. Over a period of time, the slurry builds-up to a stage where the body cavity is completely blocked. Some conventional designs counter this from happening by automated flushing systems, however this is expensive and often impractical.

[0011] A further shortcoming with conventional knife gate designs is that the overall valve is very long. The valve body, yoke and actuator also have inherent shortcomings. By the nature of the design, the valve length will be at least three times the valve bore‘size of the valve’. This means that valves need to be installed horizontally or placed in the pipeline in a position where system design is compromised to accommodate the practicality of the valve’s dimensions. [0012] In addition, valves that are installed horizontally should ideally be installed with properly designed supports, which can be costly to manufacture and install. As a result of this, valves are often installed without proper supports. When valves are installed in a horizontal position, excess stress and forces are placed on the yoke, the stem and the actuator bearings and seals. If the actuator fails, then the valve cannot stroke often leading to the destruction of the seat, gate and body. Neither the actuator nor the yoke is designed to take load. The actuator seals often fail due to excessive load and as a result the seals pass air through leaving the valve in a vulnerable or compromised position exposed to erosion due to exposure to the flow path of the slurry.

[0013] The current invention was conceived with these shortcomings in mind and proposes possible solutions, at least in part, in amelioration of some of the known shortcomings in the art.

SUMMARY OF THE INVENTION

[0014] According to a first aspect of the invention there is provided a knife gate valve arrangement comprising:

a valve body having an inlet and an outlet, and a flow passage extending between the inlet and the outlet;

a valve seat located in the passage; and

a sliding gate valve member located in the flow passage, and being slidingly displaceable relative to the valve seat between an open position, in which the gate valve member is at least partially removed from the passage, and a closed position, in which the gate valve member closes of the passage;

characterised in that an actuator is provided on each side of the valve body, with the actuators engaging the gate valve member on both sides of the gate valve member when displacing the gate valve member between the open and closed positions when actuated.

[0015] There is provided for the actuators to be supported by actuator support brackets that extend from the valve body. [0016] There is provided for securing extensions to extend sideways from the gate valve member, and for ends of the actuators to be secured to the securing extensions. The sliding gate valve member may be located on an elongate gate carrier, with opposing ends of the gate carrier defining the securing extensions. Alternatively, the securing extensions may be integrally formed with the gate valve member.

[0017] There is provided for the actuators to be piston and cylinder actuators.

[0018] There is provided for the valve to include a gate guide arrangement for use in guiding the displacement of the gate carrier, and hence the sliding gate valve member, relative to the valve body.

[0019] A further feature of the invention provides for the valve arrangement to include a flushing circuit for operative injection of flushing fluid into the flow passage to minimise accumulation of particles proximate the sliding gate valve member when actuated between the open and closed positions

[0020] A further feature of the invention provides for the valve to be configured such that a direction of travel of the sliding gate valve member when actuated into the open position is substantially along the direction of gravity.

[0021] A still further feature provides for the valve arrangement to include a sealing gland arranged about the sliding gate valve member at an interface between the valve body and the atmosphere to minimise fluid escaping from the valve arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS

The description will be made with reference to the accompanying drawings in which:

Figure 1 is a front perspective-view diagrammatic representation of one embodiment of a knife gate valve arrangement in accordance with an aspect of the invention, showing the valve member in the open position; Figure 2 is a front perspective-view diagrammatic representation of the knife gate valve arrangement of Figure 1 , showing the valve member in the closed position;

Figure 3 is a top perspective-view diagrammatic representation of the knife gate valve arrangement of Figure 1 , showing the valve member in the open position;

Figure 4 is a top perspective-view diagrammatic representation of the knife gate valve arrangement of Figure 3, showing the valve member in the closed position;

Figure 5 is a bottom perspective-view diagrammatic representation of the knife gate valve arrangement of Figure 1 , showing the valve member in the closed position;

Figure 6 is a top perspective-view diagrammatic representation of the knife gate valve arrangement of Figure 5, showing the valve member in the open position;

Figure 7 is a sectional perspective-view diagrammatic representation of the knife gate valve arrangement of Figure 1 , showing the valve member in the closed position;

Figure 8 is a sectional perspective-view diagrammatic representation of the knife gate valve arrangement of Figure 7, showing the valve member in the open position;

Figure 9 is a perspective-view diagrammatic representation of one example of a gland of the knife gate valve arrangement of Figure 1 ;

Figure 10 is a closer view of a side aspect of the gland of the gland of Figure 9;

Figure 11 is a front perspective-view diagrammatic representation of a second embodiment of a knife gate valve arrangement in accordance with the invention, showing the valve member in the open position; and

Figure 12 is a front perspective-view diagrammatic representation of a third embodiment of a knife gate valve arrangement in accordance with the invention, showing the valve member in the open position. DETAILED DESCRIPTION OF EMBODIMENTS

[0022] Further features of the present invention are more fully described in the following description of several non- limiting embodiments thereof. This description is included solely for the purposes of exemplifying the present invention to the skilled addressee. It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above. In the figures, incorporated to illustrate features of the example embodiment or embodiments, like reference numerals are used to identify like parts throughout.

[0023] With reference now to the accompanying figures, there is shown one possible embodiment of a knife gate valve arrangement 10. In the exemplified embodiment, the valve arrangement 10 generally comprises a knife gate valve member 12, a valve body 14 and actuators 26.

[0024] The valve body 14 defines a pipeline coupling 16 whereby the body 14 is operatively arrangeable in line with a pipeline (not shown), as is known in the art. The body 14 also defines at least two actuator supports 18 which are configured to generally support actuators 26 on opposite sides of the valve body 14, as shown.

[0025] The body 14 includes a sliding gate slot 20, inside which an annular seat 40 comprising two opposing annular halves is located. In use, the gate valve member 12 will slide inside the sliding gate slot 20, and more particular between the two halves of the seat 40, between a closed position (in which the valve member 12 obstructs fluid flow through the pipeline coupling 16) and an open position (in which the pipeline coupling 16 is unobstructed to fluid flow).

[0026] The body 14 further also includes a flushing circuit 24 for operative injection of flushing fluid about at least a portion of the sliding gate slot 20, described in more detail below, in order to minimise accumulation of particles proximate the sliding valve member 12 when actuated between the open and closed positions. [0027] The valve arrangement 10 also generally includes at least two actuators 26 that are each supported by an actuator support 18 and are configured to selectively actuate the valve member 12 in unison between the open and closed positions. The actuators 16 are linked to the sliding gate 12 by way of a gate guide arrangement 34. In this embodiment, the gate guide arrangement 34 comprises two legs 34.1 including channels 35 inside which actuator rods 26.1 travels up and down during use. An end of each actuator rod 26.1 is secured to opposing securing extensions 60.1 of a gate carrier 60, and the gate carrier 60 in turn carries a bottom end of the gate 12. If the two securing extensions 60.1 of the gate carrier 60 is therefore displaced simultaneously, it will translate into even and stable displacement of the gate valve member 12 relative to the valve body 14. A screen 36 extends between the two legs in order to cover the cavity in which the gate 12 is displaced, and a visual indicator 38 extends through a complementary slot provided in the screen in order to provide an observer with a visible indication of the position of the gate valve member 12, in particular when the screen is not of a see-through nature.

[0028] Importantly, the valve 10 is generally configured such that a direction of travel of the sliding gate valve member 12 when actuated into the open position is substantially along the direction of gravity. Similarly, the valve 10 is configured such that a direction of travel of the sliding gate valve member 12 when actuated into the closed position is substantially against the direction of gravity. The skilled addressee will appreciate that the direction of gravity is also operatively downwards.

[0029] In particular, and in light of the problems experienced with accretion of particles due to gravity when pumping slurry in a pipeline, the valve arrangement 10 is generally installed such that the sliding gate valve member 12 opens downwards, as shown in the accompanying figures. In this manner, closing the sliding gate valve member 12 occurs from a bottom part of the pipeline (or more specifically, the flow passage 30 of the valve body 14 as described below), so that particles settling-out of a slurry due to the influence of gravity is displaced or pushed out of the way from the bottom of the pipeline as the sliding gate valve member 12 closes, rather than the valve member 12 closing onto such particles, as per the conventional designs.

[0030] The sliding gate valve member 12 is typically actuated into or out of the valve body 14 transverse to the flow of fluid within the pipeline to change between the closed or open positions. Typically, the sliding gate valve member 12 comprises a plate-like structure, as shown, configured to obstruct the flow of fluid through the pipeline when actuated into the closed position. The sliding gate valve member 12 have two sides or ends, one located towards each side of the valve body. When referring to“sides” in this context, a“side” does not refer to the two opposing faces of the gate valve member (i.e. the faces that are perpendicular to the flow through the valve), but rather to the two operationally vertical side edges of the gate valve member that define part of the periphery of the gate valve member.

[0031] The valve body 14 may comprise a unitary structure, or it may be formed from the combination of different parts, depending on requirements, and as known in the art of valve manufacture.

[0032] In the present example, the valve body 14 includes a flange 28 with fastener apertures for coupling with a corresponding pipeline flange, typically via nut and bolt fasteners, or the like.

[0033] The valve seat 40 takes the form of two adjacent, annular rubber or plastic sleeves, as is well known in the art. The valve body 14 also includes a further valve gland 42 arranged about the sliding gate valve member 12 at an interface between the valve body 14 and the atmosphere, where the sliding gate valve member 12 enters the valve body 14, to minimise fluid escaping from the pipeline. The gland 42 is typically held in place via suitable retaining plates (not shown), or the like, as is known in the art.

[0034] In the example shown in Figures 9 and 10, the gland 42 consists of two mirrored halves (to facilitate easy replacement without requiring removal of the sliding gate valve member 12). The halves of the gland 42 combine to form a U- shaped groove 56 operatively surrounding the valve member 12 with outside dimensions configured so that the sliding gate valve member 12 fits snugly between the halves. The gland is typically manufactured from ultra-high molecular weight general polyethylene (UHMWPE).

[0035] The gland 42 also typically includes packing apertures 54 on either side, as shown, that corresponds to similar apertures in the body 14. Such packing apertures 54 are generally used to pack the gland 42 or groove 56 with, for example, packing fibres, such as polytetrafluoroethylene (PTFE) or Teflon™ fibre, which, when compressed, forms a seal around the valve member 12. Each halve of the gland 42 also includes a separator 52 to ensure that, when more packing fibre is forced into the groove 56, that sufficient pressure is created on a side of the valve member. Without this separator 52, the packing fibres will naturally compact against the larger surface of the valve member, thus leaving a potential leak path on the side thereof. The gland 42 is generally re- packable (via the apertures on the side of the valve body) in line under full line pressure and does not require the line to be drained or depressurised, allowing maintenance while the valve arrangement 10 is in service.

[0036] In general, separator 52 is 1 mm short of the face of the groove, as shown. This is so that the packing fibres from both grooves 56 is able to meet and marry-up before they make contact with the valve member. Enough pressure is generally generated by the packing fibres and the separators 52 to ensure each groove 56 forms a fluid-tight seal against the valve member 12.

[0037] The flushing circuit 24 generally comprises at least one external flushing fluid injection aperture 44 defined in the body 14, as well as a flushing cavity 46 defined by the body 14 proximate the sliding gate slot 20. In this manner, flushing fluid is injectable at a higher pressure than fluid pressure within the pipeline in order to pressurise the flushing cavity 46 to minimise accumulation of particles within the channel 32 when the sliding gate valve member 12 is actuated between the open and closed positions.

[0038] In the first exemplified embodiment, the actuator supports 18 comprise two upper supports 48 and two lower supports 49 (defined by upper ends of legs 34.1 of the gate guide arrangement 34. An actuator 26 is supportable between this upper support 48 at one end and the upper part 49 of the legs 34.1 at another. The actuators 26 are typically selected from a group consisting of a pneumatic actuator, a hydraulic actuator, and an electromechanical actuator, as is well-known in the art.

[0039] Referring now to Figure 1 1 , a second embodiment of the invention is illustrated. This embodiment is conceptually the same as the first embodiment, but in this embodiment the width of the valve 10 is somewhat reduced, while the height is somewhat increased. This is achieved by moving the actuators 26 slightly upwards and inwards, with the actuator cylinders now effectively located on top of the upper supports 48 of the actuator supports 18. The remaining features of the design stays as is.

[0040] A third embodiment of the invention is shown in Figure 12. In this embodiment the actuators 26 are in a similar position to that of the embodiment of Figure 1 1 . Flowever, in this case the lower supports 49, as well as the gate guide arrangement 34, is different. The lower supports 49 extend sideways from the valve body 14 towards an operatively upper end of the valve body. The actuators 26 rest on top of the lower supports 49, and no upper supports are present. The gate guide arrangement 34 also takes a different, more compact form, and comprises two sideways extensions 34.2 extending from an operatively lower part of the valve body 14. Each of these extensions 34.2 includes an elongate bore 34.3 for slidingly receiving and guiding the rod 26.1 of the actuator 26. This configuration negates the need for the downwardly extending legs 34.1 of the gate guide used in the prior embodiments. It should also be noted that in this embodiment the gate carrier 60 is integrally formed with the gate 12 (e.g. cut from a steel sheet), and there is no separate gate carrier 60, but the gate carrier is rather integrated with the gate. The securing extensions 60.1 of this integrated gate carrier extends directly from the gate body, and the same functionality is retained, but with fewer components. It will be appreciated that the same approach could also be adopted for the first two embodiments, and that the gate carrier of the first two embodiments can also be used for the third embodiment. The salient aspect is that the two actuators engage the gate on two opposing sides thereof in order to create a balanced distribution of forces.

[0041] Applicant believes it particularly advantageous that the present invention provides for valve arrangement 10 wherein the valve member closes from bottom upwards, thus not forcing solid particles into the seal assembly, sleeves or seating areas of the valve member, thereby causing damage that can lead to valve failure. The arrangement instead allows the valve member 12 to‘cut’ through any particle accretions or so-called‘bedrock’ to close towards the top, thereby eliminating crushing of solids into the seat area.

[0042] It should be noted that this configuration is not a simple engineering variant of existing designs, and has not been arrived at by way of routine steps. On the contrary, the inventor realised that:

- with conventional designs, solids get stuck between the two parts of the valve seat, which is not desirable;

- it would be beneficial to operate the valve in an upside down configuration (already an inventive idea);

- this has never been suggested, and is generally also not possible due to space constraints, and more particularly due to conventional gate valves being too tall to fit in standard plant locations in an inverse configuration;

- if the actuator is simply moved to the side to reduce the height of the valve, the force distribution onto the sliding gate valve member becomes unbalanced, and in addition customized support brackets will be required;

- the inventor realised that one possible solution is to reduce the height of the valve, but this is not that simple, in particular in light of the fact that gate valve actuators have been designed in the same manner for a very long time;

- which problem the inventor then solved by using two actuators located towards the side of the valve body, in combination with the use of a gate carrier (or securing extensions extending sideways from the sliding gate) to ensure that forces are equally distributed from the actuators to the sliding gate.

[0043] The inventor accordingly believes it a further advantage that the arrangement 10, particularly the arrangement of the opposite actuators 26, provides a more compact design of at least 50% of traditional valve design height and can be installed in smaller spaces. The valve arrangement 10 can be installed in horizontal and vertical positions without excessive stress/wear on the valve body and actuator components and seals. The valve arrangement with the integrated actuator support structure also eliminates the need for costly valve supports. With the actuators 26 mounted on opposite sides of the valve body 14 and connected to the top of the valve body 14 with the actuator supports 18 forming a stabiliser plate, excessive vibration is also minimised, resulting in less wear on valve parts, such as actuator seals and bearings further preventing premature valve failure.

[0044] Importantly, the valve arrangement 10 includes the flushing circuit 24 which allows for self-cleaning operation. During opening or closing of the sliding gate valve member 12, the flushing cavity 46 can be pressurised with external water with a higher pressure than the pipeline in-line pressure, leading to a net inflow of water, thus preventing solid particles from a slurry getting lodged in undesired areas.

[0045] In addition, the inventor believes it particularly advantageous that the gland 42 is repackable with packing fibres without requiring removal of the gland 42, which greatly facilitates maintenance of the valve arrangement 10 whilst minimising operational downtime.

[0046] Optional embodiments of the present invention may also be said to broadly consist in the parts, elements and features referred to or indicated herein, individually or collectively, in any or all combinations of two or more of the parts, elements or features, and wherein specific integers are mentioned herein which have known equivalents in the art to which the invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth. In the example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail, as such will be readily understood by the skilled addressee.

Claims

1 . A knife gate valve arrangement comprising:

a valve seat located in the passage; and

characterised in that an actuator is provided towards each side of the valve body, with the actuators engaging the gate valve member on both sides of the gate valve member when displacing the gate valve member between the open and closed positions when actuated.

2. The knife gate valve arrangement of claim 1 in which the actuators are supported by actuator support brackets that extend from the valve body.

3. The knife gate valve arrangement of claim 1 in which securing extensions extend sideways from the gate valve member, and in which ends of the actuators are secured to the securing extensions.

4. The knife gate valve arrangement of claim 3 in which the sliding gate valve member is located on an elongate gate carrier, and in which opposing ends of the gate carrier define the securing extensions.

5. The knife gate valve arrangement of claim 3 in which the securing extensions are integrally formed with the gate valve member.

6. The knife gate valve arrangement of claim 3 in which the actuators are piston and cylinder assemblies.

7. The knife gate valve arrangement of claim 3 in which the valve arrangement includes a gate guide arrangement for use in guiding the displacement of the gate carrier, and hence the sliding gate valve member, relative to the valve body.

8. The knife gate valve arrangement of claim 1 including a flushing circuit for operative injection of flushing fluid into the flow passage to minimise accumulation of particles proximate the sliding gate valve member when actuated between the open and closed positions.

9. The knife gate valve arrangement of claim 1 in which the valve is configured such that a direction of travel of the sliding gate valve member when actuated towards the open position is substantially along the direction of gravity.

10. The knife gate valve arrangement of claim 1 including a sealing gland arranged about the sliding gate valve member at an interface between the valve body and the atmosphere to minimise fluid escaping from the valve arrangement.