GB2641061A

GB2641061A - Valve

Info

Publication number: GB2641061A
Application number: GB2406813.2A
Authority: GB
Inventors: Woodward Peter
Original assignee: Individual
Current assignee: Individual
Priority date: 2024-05-14
Filing date: 2024-05-14
Publication date: 2025-11-19
Also published as: WO2025237935A1; GB202406813D0

Abstract

Gate valve 10 for a Hyperloop (RTM) or low-pressure or vacuum tunnel transportation system comprising a valve body, a valve element 22 moveable within the body, one or more static seals 40 and one or more moveable seals 50. There may be static and moveable seals on each opposing face of the valve element. The valve body may have a front plate 12 and a back plate 14, with static and moveable seals on each plate. The moveable seal may be inflatable. The moveable seal may be concentric with and outside or peripheral to the static seal. There may be a seal guard concentric with the static seal to protect it from damage during use of the valve. The moveable seal may have an internal cavity 58 which expands upon entry of a fluid like liquid or air. The moveable seal may be circular, annular, continuous, or comprise a hollow compartment. The moveable seal may comprise a hollow nose portion 52 which engages the valve element when the seal is inflated. The internal cavity may have concave sidewalls 54. The valve element may be a gate in the form of a disc having a half-crescent or semicircular recess or cutout, and one or more chamfered edges.

Description

Intellectual Property Office Application No 61324068132 RTM Date:14 November 2024 The following terms are registered trade marks and should be read as such wherever they occur in this document: Hyperloop Intellectual Property Office is an operating name of the Patent Office www.gov.uk /ipo

VALVE

The present invention relates to a valve for use in hyperloop vacuum transportation system and hyperloop systems comprising such a valve.

Background of the Invention

Hyperloop is a high-speed transportation system for both passengers and freight comprising trains/pods within a low-pressure/vacuum tunnel.

Hyperloop systems typically comprise: i) trains/pods, which are used to contain passengers and freight to be transported from one location to another, ii) lowpressure/vacuum tunnels, through which the trains travel and iii) terminals at which passengers and freight can be loaded or unloaded from the trains. Conveying the trains through low-pressure/vacuum tunnels reduces the air resistance on the trains to greatly improve the speed and energy efficiency of the transportation system.

Hyperloop transportation promises numerous benefits, including reduced travel times, improved efficiency and sustainability compared to other modes of transportation, and decreased environmental impact, as it is able to make use of energy from renewable sources.

However, it will be appreciated that a significant challenge is creating and maintaining a vacuum within the tunnels (which may have a significant diameter of several metres). A particular challenge is pressure control at the terminals, where sections of the tunnels must be isolatable by valves to enable sections of the tunnel at the terminal to be repressurised, in order to allow for the loading and unloading of passengers and freight, without causing a loss of vacuum throughout the entire tunnel network. Isolating sections of the tunnel may also be required for critical tunnel safety isolation with valves installed every 2 kilometres for passengers' security, such that in an emergency situation passengers are able to leave the train and evacuate the tunnel under safe atmospheric conditions, while keeping the rest of the tunnel network under vacuum. Such tunnel isolation is also necessary to carry out maintenance or repair of the system. Smaller ongoing vacuum leakage system losses could cumulate significantly with an associated cost of continual topping up of this leakage by large vacuum pumps.

Whilst valves for other applications (e.g. water and gas) are well known (for example WO 2009/095669 and WO 2019/141991), vacuum transportation systems pose several unique challenges. Firstly, due to the size of the tunnels within the transportation system, the forces that the valves need to be able to withstand are significantly higher. Although the pressure differential may only be up to 1 bar (i.e. the difference between a perfect vacuum and atmospheric pressure), as the force to which the valves will be subjected is a product of the pressure differential and the surface area against which the pressure is applied, the forces that the valves need to withstand (with minimal body and disc flex combined with special seat seals design), is significantly greater than for other applications. In addition, in many valve applications, the supply of fluid to the valve can be cut off to allow for maintenance or repair of the valve (e.g. to replace valve seals). However, it will be appreciated that due to the size of hyperloop transportation networks and the amount of energy required to bring the entire network down to vacuum, repressurising the entire network, or even several kilometres of tunnel, to carry out maintenance on the valves is not viable. In addition, compared to valves for liquids (such as pressurised water and gas), valves for vacuum applications must have much higher-performing seals, even to the extent of sealing components' surface finish and base material permeation, as vacuum/air is more penetrative than other fluids. Here, issues of valve body and obturator/disc rigidity and seat seal technology combine to defeat vacuum seat leakage, with far greater concern and challenges than for other applications.

Historically a 1-meter diameter vacuum valve for critical isolation would have been considered large, so this new horizon for large-scale vacuum valves presents new challenges.

There therefore exists the need for valves for use in hyperloop transportation systems and particularly improved valves which are able to achieve vacuum isolation between pressurised and depressurised sections of the tunnel network.

Summary of the Invention

In a first aspect, the invention provides a valve suitable for use in a hyperloop network, said valve comprising a valve body and a valve element movable within the valve body.

In a second aspect of the invention, there is also provided a hyperloop transportation system (also referred to as a vacuum transport system) comprising a valve (e.g. a gate valve), such as a valve as described herein.

The valve of the invention is typically a gate valve and preferably, a knife gate valve. Knife gate valves typically have a full clear bore and/or (bi-directional) vacuum sealing. Typically, in the valves of the invention, sealing takes place against the face(s) of the gate/knife, rather than on the edges of the gate/knife.

The valves of the invention may comprise one or more (of the) types of seals and/or other components as described below, many of which have advantageous features that can be used in combination that may result in a unique, high-performance valve.

For example, the invention also provides a hyperloop valve, as defined above, comprising one or more static seals and/or one or more movable seals (as defined herein).

In another aspect of the invention, there is provided a valve comprising a valve body and a valve element mounted in the valve body, so as to be movable between an open position, and a closed position. Thus a valve opening is formed in the valve body and/or closed by the valve element. The valve element can comprise two opposed faces spaced from the transverse plane of the valve element, wherein the valve body may be provided with one or more statics seals and/or one or more movable seals, such as on each side of the valve element, suitably to sealingly engage with (a portion of) the valve element, when closed, suitably to seal the valve element (against the valve body).

As noted above, one aspect of the invention relates to a gate valve for use in a vacuum transportation system. The gate valve can have one or more seals. Preferably, the valve has at least one or more seal retaining element(s), such as ring(s). The seals and the retaining elements may be substantially circular or annular. The retaining elements may be secured to the valve body by securing means, such as nuts and/or bolts. Each seal may be provided with one or more retaining elements (e.g. rings).

The valve may comprise a valve body having a front plate and a back plate, wherein each plate comprises at least one seal. Preferably each plate comprises at least one or more static seals and/or one or more movable seals. In a preferred embodiment, each plate is provided with two static seals, which van be concentrically mounted, and one movable seal, suitably peripheral to the static seal(s).

The valve of the present invention is suitable for use in a vacuum/hyperloop transportation system. Such a system will usually comprise a tunnel (such as a tube, pipeline, pipe or passage) that can accommodate a train (which includes a pod, carriage, coach or compartment). The train suitably has a magnetic propulsion system and/or can move by magnetic levitation. However, it may also comprise an air levitation or cushion system to reduce friction. The train/pod will not usually run on rails and when the train/pod is in motion there will be no physical contact between the train and the tunnel through which it is travelling. The train/pod will suitably be a high-speed or high-velocity vehicle. It may comprise human passengers, and thus seats therefor, and/or may transport freight.

The hyperloop system may run at a vacuum, or a reduced or low pressure. Preferably, this is less than one atmosphere, suitably at or above 1 millibar, such as below 10 or 100 millibars.

The system may comprise one or more terminals (such as stops or stations). This may allow humans/passengers to embark and/or disembark. In order to preserve the vacuum in the tunnel, one can provide one or more valves of the present invention, in the tunnel. This may effectively provide or create an airlock chamber, or isolate a terminal airlock chamber, where passengers need to board and alight the train. Thus, the human-accessible parts should be at or substantially near atmospheric pressure (at least when humans are present).

The valves of the invention thus may have a dual function. Firstly, they may preserve the low pressure in the tunnel. Secondly, they also may provide a substantially (near) atmospheric (i.e. around 1 Atm/bar) environment for access, such as entry and/or exit of passengers, for example to access the train. Near atmospheric (1 Atm) sections also need to be provided within the tunnel, such as for access or maintenance.

Suitably, a valve will be provided at either end of a station or airlock chamber isolation. They may also be provided at specified points or regular intervals in the tunnel, either for security maintenance or other safety reasons.

The valve body typically is generally rectangular/cuboidal in shape and comprises a front panel and a back panel with sides that are secured together to define an enclosed interior volume, in which the valve element, seals and other components are located. Each front panel and back panel is typically provided with an aperture (e.g. a circular aperture having the same diameter as the tunnel bore) which, in use, serves as the valve opening through which not only fluid, but in the application of vacuum transportation the trains/pods, can pass. The apertures and resulting valve opening are typically circular in shape.

It will be appreciated that the term "fluid" encompasses both liquids and gases. However, for the purpose of vacuum transportation systems, the relevant fluid passing through the valve is air.

When assembled, the apertures in each of the front plate and back plate can be co-axially aligned to form a passageway through the valve. In this way, the valve body may define a valve opening defined by a passageway, through which air and transport pods can pass (in an axial direction with respect to the opening). The valve opening is generally circular in shape. It may have a diameter 3m or greater, preferably 4m or greater and optionally up to 6m or 7m.

Each end of the valve body is typically connected or connectable to a tunnel which may form part of a vacuum transportation network.

The valve body generally comprises a movable valve element, which is movable in a direction perpendicular to the longitudinal direction of the opening (the longitudinal direction being the direction through which air and transport pods pass through the valve).

This may allow the valve to open and/or close. The valve element is therefore suitably movable from an open position to or from a closed position, and vice versa. When the valve is installed in a vertical position, the valve element is suitably, in use, movable vertically (thus either up and/or down). The motion may be upwards towards an open position and/or downwards towards a closed position. Alternatively, the valve may be installed in a horizontal position, where the valve element may be moved left or right (when viewed along the axis of the opening) to open or close the valve (or vice versa).

The valve is generally described throughout as if it were installed in a vertical position, with the valve element moving vertically to open or close the valve. However, it will be appreciated that the valve can be installed horizontally, and may function in the same way.

Therefore, although vertical installation is discussed for illustrative purposes, the application covers both vertically and horizontally mounted valves (and movable valve elements).

The valve element has two opposing faces and, typically, has a substantially constant depth/thickness (in the longitudinal direction). However, the valve element may also be provided with a raised annular section, such as on one or both of its faces. The raised annular section is suitably positioned at a location on which can engage with the seal(s), such as when the valve is in the closed position. This therefore increases the seal between the seals and the valve element, so that wearing of the seals during motion of the valve element may be reduced, compared to if the entirety of the valve element was of the increased thickness. To avoid any sharp edges, which could cause damage to the seals, the edges of the raised annular section are smoothed or graduated, usually from the raised section to the lower section of the valve element.

The valve element may also have one or more chamfered edges. Typically, at least the two sides of the valve element (which in use are disposed between the seals) are chamfered. This allows the valve element to move safely between the seals, with minimum effort and/or minimal damage.

to The valve element typically takes the form of, or comprises, a gate. The gate is generally rectangular in shape but may comprise a concave or crescent-shaped bottom or underside. It may therefore have a substantially circular (preferably semi-circular) recess or cleft or hollow. Thus, the gate will not be circular (as might be expected) but counter-intuitively has a semi-circular or concave recess or profile. This is to mirror or match the (generally circular) opening or bore, so that the bottom of the valve element is aligned with the valve opening when the valve is fully opened and thus trains/pods can travel through the tunnel and valve unimpeded.

The recess may create a pair of legs of the valve element, suitably either side of the semicircular/concave recess. This means that the legs of the gate element are located in and stay within the valve body (and specifically between the seals) and may thus straddle either side of the circular bore or opening. This may reduce vibration and fatigue of associated components and can assist in accurate positioning or centralisation and anti-cant to maximise sealing.

The pair of legs may thus remain within the valve body or are retained within the valve body. They effectively straddle the seal or the valve (circular) opening. Thus, while in the open position, or while opening, and thus not in the closed position, the pair of legs will straddle or be positioned either side of the central (circular) opening. This means that when in the open position, the legs will still be retained and remain within the valve body and will be positioned adjacent the annular seals.

In a preferred embodiment, the valve element takes the form of a rectangular gate in which there is a concave cut-out from its bottom edge. For example, the shape of the bottom of the valve element may correspond generally with the shape of the top of the circular passageway (as shown in Figure 7). This shape may allow for the valve opening to be entirely unobstructed, such as when the valve is open, such that the valve disc may be supported at each side along its entire height at any position (i.e. when the valve is fully opened, partially opened, or closed).

An added importance of this shape of the valve element is that it may create a crescent aperture during closing of the bottom half of the valve bore. This may reduce the valve opening progressively from the outer seal sides towards a final central point of final closure. This concave valve element geometry can cause the lower half seal compression to progress in alignment with the seal line direction, and suitably not at a more stressful right angle to the seal. The same advantage applies in the valve opening direction.

As discussed above, the front and back panels of the valve can define an interior channel, through which the valve element can be inserted (fully or partially) or removed.

The top of the valve element (when the valve is vertically installed and movement of the disc is vertical) is typically provided with one or more valve stem(s) that are able to effect raising and/or lowering or movement of the valve element, within the valve passage, suitably in order to cause opening and/or closing of the valve (by obscuring the valve opening). For larger valves, two parallel valve stems with synchronised actuation (with corresponding features as described herein) may be necessary. The valve can be installed horizontally, wherein movement of the valve element would be horizontal.

In order to preserve the low pressure (such as in the tunnel) or atmospheric pressure (such as at a station), the valve will comprise one or more seals. Typically, each of the rear side of the valve body front panel and the forward side of the back panel (i.e. the sides of the two panels that face each other when assembled) are fitted with the one or more seals, as described herein. The location of the seals therefore allows them to engage with the faces of the valve element, suitably as it moves between the open and closed positions (i.e. up and down in a vertically installed valve), usually through the channel between the front and back valve block panels. In this way, fluid (e.g. air) may be prevented from passing through the valve opening (and therefore the valve itself) when the valve is closed.

Suitably, the invention relates to a valve comprising one or more static seals and one or more movable seals. Preferably, each seal is circular or annular in shape. The seals may all be concentric, usually around the valve opening. Suitably, there are two static seals on each side of the bidirectional valve. Preferably, there is also one movable seal on each side of the valve. In preferred embodiments, there is one movable seal and two static seals on each side of the valve element. In that arrangement, suitably the movable seal is concentric and/or larger in diameter and/or outside the static seal(s).

The or each seal may be secured or retained within the valve body by one or more seal retaining elements(s), such as retaining ring(s). The retaining ring(s) may be formed from stainless steel. These may enable easy seal replacement.

As described above, at least one of the seals may be a movable seal. The movable seal may be displaceable from the valve body in a direction outwardly towards the valve element so as to seal against the sealing surface of the valve body in a substantially gas-tight manner. The displacement may be caused as the result of application of the pressurized fluid to the seal or through mechanical movement of the seal.

Although the movable seal may be mechanically movable to engage and disengage with the valve element to form a seal, the or each movable seal preferably is inflatable, in that it may expand and/or contract to engage, or disengage, with the valve element. It may therefore be expandable and/or contractable, for example on entry and/or exit of a fluid (such as a gas, such as air, or a liquid, for example water and/or hydraulic fluid) into part of the seal. The seal may therefore be capable of receiving and/or containing a fluid, for example under pressure. The movable seal may therefore comprise an entry and/or exit port for entry and/or egress of a fluid. The entry and exit port may take the form of the same port with fluid entering and exiting the valve via the same port. As discussed in further detail below, the movable seal may comprise an expandable chamber, such chamber being expandable (at least in a direction towards the valve element) with the pressure of a fluid, to therefore create a seal.

The seal may be of substantially annular or substantially ring form, but could be rectangular or square in shape, such as depending on the shape of the valve opening.

As described above, the front/back panels of the valve body may each comprise a recess or cavity, in which movable seals are located. The recess or cavity is typically circular/annular in shape and extends around the opening in a concentric manner. The movable seal may be fixed into the recess whilst allowing for displacement from a retracted position to an extended position. In the retracted position, the nose of the movable seal is typically sufficiently withdrawn to be out of the path of the movement of the disk and generally does not extend out of the recess or cavity. By contrast, in the expanded position, the nose protrudes out of the recess or cavity and engages to seal tight with a face of the valve element.

The seal may be viewed as having a forward nose portion and a rearward expandable 5 chamber.

The nose portion, which is arranged to seal against the valve element, may be formed of a substantially solid section resilient material. The nose portion preferably has a rearward surface that is arranged to be acted on by a pressurised fluid, such as to displace the nose portion towards the valve element to provide a leak-tight seal against the face of the valve element. This rearward surface may be a partitioning wall in the valve between the nose portion and the expandable chamber.

The nose portion may comprise a rounded, curved or ribbed cross-sectional geometry or profile, with the one or more (spaced apart) ribs or peaks optionally extending around the seal nose.

The nose portion may be of solid or substantially non-hollow construction. However, preferably, for the reasons described below, the nose portion is hollow. The seal nose may be non-movable. The nose portion may be formed of a resilient material, such as silicone or rubber. The nose portion may have a resilience which allows it to at least in part conform to the profile of the valve element when the seal is actuated against the valve element.

As described herein, the hollow nature of the nose portion may allow it to deform upon contact with the valve element in order to better seal against the valve element and prevent air from leaking between the side of the nose and its retaining rings and the back of the seal.

The seal may comprise an expandable chamber, which, when provided with pressurised fluid, urges the nose of the seal, into sealing engagement with a face of the valve element.

Although the nose may be hollow, this is separate and not in fluid communication with the expandable chamber within the main body of the seal. The extent of expansion is constrained by the recess/cavity in which the movable seal is located and also the maximum volume or length of the expandable chamber As noted above, the hollow of the nose is typically separate from the expandable chamber. The moveable seal expandable chamber partitioning wall with the seal nose may therefore have a cross-section designed to maintain rigidity and drive the nose forward, whilst bracing the seal shoulders against folding inwards, which is further reinforced by the pressurised expandable chamber.

The seal may therefore be provided with a conduit which is connected or connectable to a source of pressurised fluid and is in communication with the expandable chamber of the seal (via the port). The port may take the form of an opening, or be in fluid communication with, an opening in a rearward wall of the seal. The rearward wall of the seal opposes the nose portion of the seal.

The expandable chamber may further be defined by side walls of the seal which join the rearward wall and nose portion. The side walls may have a shape that enables them to expand to a position where the rearward wall and nose portion are distanced apart from either other further than when the side walls are in a contracted position. In a preferred embodiment, the walls are concave in shape. This shape has been particularly advantageous to allow the expansion chamber a limited stretch with elastic recoil to assist contracting (and for the nose portion to be withdrawn) when the application of pressurised fluid is removed from the seal.

The cavity or recess may be provided with shoulders. These may be integrally formed or provided in the form of a retaining ring. The shoulders cause the cavity to have a narrower aperture at its opening, compared to at the depth of the cavity. The purpose of this is to retain the movable seal within the cavity, but to allow the nose portion (which is dimensioned to be smaller than the narrowest part of the cavity) to protrude out of the cavity and to engage with the valve element, when in an extended/expanded state.

Upon expansion/inflation of the seal, the leading front edges of the seal (surrounding the nose) engage with the shoulders to seal off the nose side clearance, thus preventing any vacuum leak path crossing the seal chamber.

The fluid pressurisation system may comprise a hydraulic or a pneumatic (e.g. compressed air) system for actuating the movable seal. A pressurised fluid line or conduit may be provided through the valve body to connect the source of pressurised fluid to the expansion chamber.

In addition, or as an alternative, to the movable seal described above, the valve may be provided with one or more (preferably two or more) additional static seals. As for the movable seal, the static seal(s) is/are located in a cavity/recess in the front/rear valve body panels.

The static seal(s) may comprise or take the form of 0-rings. These may comprise rubber or a similar deformable and/or flexible material.

The static seals are typically concentric with the movable seal and/or may be located radially inwardly or radially outwardly of the movable seal.

Preferably, there are two or more, for example three or more, concentric static seals (in 1c) addition to the movable seal). In a particular embodiment, the valve comprises two static seals on each side of the valve element and therefore four in total across the valve (in its longitudinal direction).

It will be appreciated that by using two (or more) seals in series to each other, the pressure differential that the valve as a whole is able to withstand is increased. For example, for a seal that is able to withstand a pressure differential of 1 bar, using two seals in parallel means that each seal is only subject to a pressure differential of 0.5 bar. If a total of four seals are provided across the depth of the valve, the pressure differential per seal is reduced to 0.25 bar. As a result of this effect, valves which are able to withstand much greater pressure differentials than the tolerance of the individual seals alone can be produced. This is particularly advantageous in the hyperloop vacuum systems described herein, wherein the diameter of the valve opening may be greater than 2m and is typically also greater than 4m.

In vacuum conditions, the valve element is horizontally displaced in a direction towards the lower pressure/vacuum side of the valve. This creates a stronger seal on the vacuum side of the valve, but consequently a weaker seal on the higher pressure side of the valve (as the pressure differential pushes the valve element towards the lower pressure side). The use of multiple static seals serves to reduce this issue, as a result of the back pressure build-up between the seals. At a 1 bar differential pressure, a single seal requires a certain level of compression to withstand this. If a level of 0.5 bar of compression is applied, then 3c) at a pressure higher of higher than 0.5 bar, the seal will leak. However, if a second seal is used, the interspace leaked pressure past the first seal (i.e. the pressure above which the first seal is not able to hold, e.g. 0.5 bar) will build up in the interspace between the two seals. The second seal will also hold tight until a leaked pressure past the first seal exceeds 0.5 bar. As a result, the two seals have each held 2 x 0.5 bar (i.e. 1 bar in total). The use of four seals across the whole valve (i.e. 0.25 bar per seal) means that satisfactory sealing can be obtained with less seal compression required than for a single seal.

Therefore, this reduction in seal compression corresponds to the decompression allowance reserved to maintain seal tightness on the upstream seal face irrespective of decompression under horizontal force disc displacement and also absorbs seal decompression.

The valve may also be provided with a seal guard. The guard may be circular, or annular, or generally ring-shaped. It may also be concentric with the valve opening and optionally the seals in the valve. The seal guard may be located radially outwardly of both the static and movable seals or radially inwardly of the movable seal and outwardly of the static seals. The seal guard may be formed from a tough, but flexible material, with a low surface friction, such as a plastic (for example, polytetralfluoroethylene).

The seal guard has a dual function. Firstly, to protect the static seals from deposits and secondly, to provide an axial guide for the valve element and limit sideways movement under differential pressure. The seal guard may protrude from the front or back plate of the valve body at least as far as to precisely control the degree of pre-determined static seal protrusion for effective sealing compression, plus anti-cant valve element to ensure uniform seal compression and leak tightness.

The valve element may also be provided with roller guides on its edges. The roller guides may be aluminium bronze roller guides and there may be one or two or more mounted on each side. These may engage with guide ribs (which may be formed from stainless steel) in both body side walls, to ensure that the valve element is laterally centred.

The stem typically extends out of the top of the valve body (when vertically mounted) for connection to a motor, which can effect rotation of the stem and movement of the valve element. The valve body is therefore typically provided with an aperture through which the stem exists the valve body. The top of the valve body may be provided with a stem housing which surrounds the aperture through which the stem passes. The housing may comprise a channel and/or gland seal bush through which the stem passes. The channel may be provided with one or more stem seals (e.g. 0-rings) to seal the lower part of the housing, which is in fluid communication with the valve body via the aperture through which the stem passes, against the top of the housing, which is at atmospheric pressure. These stem seals therefore prevent loss of vacuum through the top of the valve where the stem exists the valve body.

Surrounding the aperture through which the stem passes on the underside of the top of the valve body (i.e. inside of the valve body), there may be provided one or more (e.g. two) compressible ring(s). The compressible rings may be formed from or comprise rubber.

The compressible rings are typically vertically stacked and concentric with each other and surround the stem. The top of the valve element may be provided with a ring-engaging surface. The ring-engaging surface is typically flat and/or annular in shape, and may be dimensioned to push against the compressible rings, such as when the valve element is in a raised position.

The ring engaging-surface may engage with the rings directly, or indirectly, e.g. via a washer, such as located between the ring engaging-surface of the top of the valve element and the compressible rings. As the ring-engaging surface compresses the rubber rings, these are flattened to reduce their internal diameter slightly and form a vacuum-tight seal with the stem therethrough and the aperture through which the stem passes. In this arrangement, the external stem housing can be disassembled for maintenance purposes (e.g. to replace the stem seals) without causing a loss of vacuum within the valve and no interruption to service.

Within the valve body, the valve stem may be provided within an expandable casing. An upper end of the expandable casing is typically sealingly attached to the underside of the top of the valve body. The lower end is usually sealingly attached to the top of the valve element. This can create a sealed environment around the stem to prevent the grease/lubricant on the stem from being sucked dry under vacuum conditions. The expandable casing may be generally cylindrical in shape with concertinaed walls, which may allow the length of the casing to increase or decrease as the valve element moves up and down the valve stem.

As noted above, a significant challenge for vacuum transportation system valves is the valve size and large surface area forces which create distortion under pressure (positive pressure or vacuum). As a result, minor movements in the valve components can disrupt tight sealing and result in leaks in the vacuum.

To improve the seal quality, the surface finish of the sealing components (e.g. the seals and the valve element) should have high-grade surface finishes. For example, the valve element may be formed from stainless steel, suitably with a highly mechanically polished surface finish (and usually not a grainy one where the micro-roughness will allow the vacuum to easily leak). The seals must have equally smooth moulded finishes, suitably without defects or particle deposits which present leak paths to the vacuum.

Preferred characteristics of one aspect of the invention are equally applicable to another aspect mutatis mutandis.

A particular embodiment of the invention is described in further detail below with reference to the accompanying Figures 1 to 8.

Brief Description of the Drawings

Figure 1 shows a front view of a valve according to one embodiment of the invention in a partially open state, with the lower end of the disc visible in the valve opening.

Figure 2 is a cross-sectional side view of the valve shown in Figure 1. Figure 3 is an expanded view of region A shown in Figure 2.

Figure 4 is an expanded view of one of static seals shown in Figure 3.

Figure 5 is an expanded view of one of the movable seals shown in Figure 3.

Figure 6 is an expanded view of region B shown in Figure 2. Figure 7 shows the profile of the valve disc.

Figure 8 shows the results of FEA modelling showing the strength and rigidity of the valve shown in Figure 1 when in use.

Detailed Description of the Invention

As shown in Figures 1 and 2, the valve (10) comprises a valve body having a passage (18) therethrough which defines a valve opening (20). The valve opening (20) is opened and closed by a disc valve element (22) to control the flow of air passing through the valve (10).

The valve (10) comprises a front panel (12) and a rear panel (14) which are spaced apart from each other and enclose a region where the disc (22) is located when the valve is open (i.e. when the disc (22) is in a raised position and does not obscure the valve opening (20) at all).

The lower section of the valve body (10) is provided with a cylindrical passageway (18) through the length of the valve (the length being defined as the dimension of the valve in the direction through which fluid travels through the valve). For use in vacuum transportation applications, it will be appreciated that the cylindrical opening must correspond to the size of the tunnels in vacuum transportation systems, which must be large enough to accommodate pods for transporting passengers and cargo from one location to another. The valve opening is circular in shape and may have a diameter of 2.2m for reduced-scale demo hyperloop tunnels or greater (up to 5 to 6m or greater) for "real-life applications". The developed valve design technology is purposely scalable.

The valve disc (22) is arranged to be moved vertically to close, partially obscure or fully obscure the valve opening. When fully closed, the disc (22) obscures the entirety of the opening (20). Movement of the valve disc (22) is effected by movement of a connected valve stem (24) in the form of a threaded rod that extends from the top of the disc, up through a threaded nut at the top of the disc (22). The disc rises by stem rotation in the threated nut, causing the disc to rise up within the stem. Rotation of the top of the valve stem (e.g. via a handle, a key or a motorised actuator (28)) thereby causes raising and lowering of the disc (22) within the valve body (10) and thus opening and closing of the valve opening (20).

The top end of the valve stem at the point at which it exits the valve body is shown in cross-section in Figure 6.

A triple 0-ring stem seal (72) is incorporated in a housing (70) mounted on top of and on the outside of the valve body (12). The housing (70) has a hole and a threaded gland seal bush (74) through the valve stem (24) passes into the 0-ring stem seal (72) to prevent stem leakage and a loss of vacuum, i.e. atmospheric air being sucked into the valve body (12). The stem (24) extends outside through the other end of the housing (70) where it can be connected to an actuator or motor to drive rotation of the stem (24) and thereby movement of the disc (22).

The 0-rings (72) may require replacement which entails dismantling the housing (70). This could result in a loss of sealing of the valve at its top. To overcome this interruption and the need to isolate a section of the hyperloop tunnel during this maintenance, the valve comprises a stem "back seal" (76) on the inside of the valve body (12) below the hole in the top of the valve body through which the stem (24) passes. The back seal (76) takes the form of two vertically stacked circular concentric rubber rings. In normal operation, this second back seal (76) does not seal against the stem (24) and the stem runs freely inside the two rubber rings. When replacement of the triple 0-rings (72) located above the top of the valve body (12) is required, the disc (22) is moved to a fully open position where a steel ring (78) on the top of the disc (22) comes to bear on a movable steel washer (80) at the bottom of the back seal (76). This pushes the washer (80) upwards to compress the two rubber stem rings (76) on the underside of the top of the valve body (12), which action of compressing the rubber rings (76) deforms them to strangle the stem (24) tight preventing any leaking through the hole in the valve body (12) through which the stem (24) passes. At the same time, this compresses the top rubber ring tight around the hole in the valve body (12) through which the stem (24) passes. The back seal (76) is therefore activated by full disc (22) opening where the internal rubber rings (76) are compressed to seal the stem (24) and stem hole from the underside/inside. This then allows for the removal of the externally mounted housing (74) and components, such as the triple 0-rings (72) for maintenance, leaving only the stem (24) protruding but sealed on the underside of the top of the valve body (12). Consequently, this permits 0-ring maintenance or replacement with the valve fully open and the valve body construction vacuum-tight with no interruption to the Hyperloop service.

The same 0-ring replacement could be achieved by closing the valve and engaging both types of disc seal (static and movable) for maximum security, but the hyperloop system would then suffer a service interruption, and hence the advantage of the stem back seal feature described above.

A bellows-shaped casing (not shown) is fixed vacuum-tight to the inside top of the valve body surrounding the back seal mechanism, which effectively encapsulates the stem, where the other end of this concertinaed bellows is attached vacuum-tight to the top of the disc (22). The bellow-shaped casing expands and contracts as the valve opens and closes and the disc (22) moves up and down. The purpose of the casing is to fully encapsulate the stem (24) so that the stem grease lubrication does not get sucked dry by the vacuum.

Valve stem replacement can be carried out when the valve is isolated from vacuum but with the valve in-situ, with only dismantling of external top works comprising an actuator, gearbox and 0-ring gland yoke assembly.

The valve disc (22) is formed from 304 stainless steel with a polished surface for effective vacuum sealing and has a thickness of 240mm. The disc (22) is constructed from two outer plates, which are internally rib-reinforced for strength and then closed all around their outside edges.

The valve disc (22) has front and rear (or upstream and downstream in use) faces. The valve disc is generally rectangular in shape with a concave cut-out at its bottom. The bottom profile of the valve disc can be seen in Figure 1, in which the valve is partially opened and the full profile of the valve disc can be seen in Figure 7.

The concave cut-out in the bottom of the disc is shaped to correspond with the top of the passageway, such that when the valve is fully opened, the bottom edge of the valve disc (22) is aligned with the top of the passageway (18) leaving the opening (20) completely unobstructed. Wth the disc in the fully open position, this has clearance of the static seals (40) and associated retaining rings enabling access for easy quick seal replacement from inside the valve, with no other heavy valve dismantling and consequent long downtimes.

One of the advantages of this shape is that the disc (22) is held within the valve body along its entire height on both sides. This provides stability to the disc to reduce vibration. If the disc had a rounded bottom (as is common in knife valves), the bottom end of the disc would not be supported by the valve body when the valve is partially open, which could cause damage to the static seals (40) as the disc (22) is lowered and the valve is closed. In the arrangement of the present invention, the edges of the disc remain sandwiched between the static seals (40) and seal guards (44) regardless of the extent to which the valve is opened. Additionally, both the left and right edges of the disc are chamfered to ensure safe entry of the disc in between the seals to minimise fouling of and damage to the seals.

Within the lower part of the valve body and in between the front and the back panels (12, 14) walls, there are provided several seal arrangements to form a vacuum seal between upstream and downstream sides of the valve. The seal arrangement is provided towards the edge of and around the entire circumference of the passageway (18) that defines the opening (20). Whilst the disc (22) prevents fluid from passing through the main centre of the valve opening (20), the seals prevent fluid from leaking through the valve around the edges of the disc (22) when the valve is closed.

The arrangement of the seals surrounding the passageway (18) in the lower part of the valve body can be seen in Figure 3.

As can be seen, two separate sealing arrangements are provided: static seals (40) and a retractable/movable seal (50).

Both the static (40) and movable (50) seals act as radial seals meaning that the pressure differential acts in a direction substantially radially to the direction of fluid flow and the longitudinal axis of the valve opening. The two types of seal are provided in the valve; both types on each side of the disc (22). For simplicity, the seal arrangements are described in relation to one side of the disc (22), but it will be appreciated, as can be seen from the figures, that a corresponding seal arrangement is also provided on the opposite side of the disc.

As shown in Figure 3, the valve comprises two concentric static seals (40) on each side of the disc (22). The two seals are integrally formed from a single ring of NBR (nitrite butadiene rubber) with two concentric protrusions along the entire length/circumference of the ring. The use of NBR seals is particularly advantageous due to their resistance to oil-based contaminants, abrasion and tear resistance, tensile strength, compression set resistance and temperature range (-30°C to 100°C). The static seals (40) are held in place within the valve body by means of retaining rings (42).

The static seals (40) can be integrally formed in a static seal ring, which is a single rubber (NBR) moulding having a flat slab back with two radially spaced rubber seals on its front.

The two seals are sufficiently spaced from each other to allow the fitting of a retaining ring between the two seals and on the outer edge of each seal (i.e. three retaining rings in total). This design secures the double seal ring (comprising the two static seals (40)) in position but also allows its future dismantling of retaining ring screws for removal and easy replacement with new seals. The retaining rings (42) themselves are in segments so that they are light and easy to man-handle. The retaining rings (42) also press the seal ring against the valve body to prevent any leaks around the back of the seal.

The structure of the static seals (40) can be seen in more detail in Figure 4. As can be seen, when the valve is closed, the seals (40) sealing engage with the face of the disc (22). The pressure differential between the upstream and downstream sides of the valve will also increase the strength of the seal, as if the disc is able to move in a sideways manner to any degree, the vacuum will suck the disc onto the seals on the side of lower pressure to increase the efficiency of the sealing arrangement.

In operation, the valve (10) is closed by lowering the disc (22), with the upstream and downstream pressures equalised. Once the valve has been fully closed, pressurisation or depressurisation will take place on one side of the valve to create a pressure differential of up to 1 bar. Thus, the compression due to horizontal movement of the disc towards the lower pressure side of the valve (within permitted tolerances), will be applied only in a static closed valve condition. Similarly, the pressure differential across the valve is equalised (e.g. via depressurising the higher pressure side down to vacuum levels) before the disc (22) is raised and the valve is opened. This increases the life of the seals, as opening and closing the valve with a full differential pressure results in higher seal friction and the presence of increased high-velocity erosive flow through the reduced cross-sectional bottom seal area.

When the disc reaches (22) the fully closed position and a pressure differential is subsequently caused, an intermediate air pressure will be trapped between the two adjacent static seals (20). The radially outer seal will experience a pressure drop from the upstream pressure to the mid-pressure and the radially inner seal will experience a pressure drop from the mid-pressure down to the pressure downstream of that seal.

Thus, when the valve is required to seal against a vacuum (i.e. a pressure differential of 1 bar), each seal is only subjected to a proportion of the pressure differential to reduce the force being applied to each seal (noting that the force is equal to a product of the pressure differential and the surface area). This means that less seal compression is required to achieve sealing or conversely, seal tightness can still be maintained with a degree of seal decompression of the upstream seal face when differential pressure acting on the disc causes its downstream axial movement.

In a vacuum transportation system, a pair of valves may be located inline with the vacuum transportation tunnel either side of a terminal. Alternatively, a single valve may be provided at an end-of-line air-lock chamber. The purpose of this is to allow the region of the tunnel that serves as the terminal or air-lock chamber to be repressurised before passengers or cargo are loaded or unloaded, without causing a repressurisation of other parts of the network.

In use, once a pod has been driven into the terminal section of the tunnel, the valves at either end of the terminal/air-lock chamber can be closed (by lowering the discs into their fully closed positions). Once the valves are closed, air can be introduced to the terminal or air-lock chamber section of the tunnel, which is now isolated from the rest of the network by the valve(s), in order to bring this section of the tunnel up to atmospheric pressure before the pod is opened. When the valves are in the closed position, air pressure is applied to the upstream faces of the valve disc (i.e. the faces facing in the direction of the pressurised, terminal section of the tunnel). If the pressure differential between the atmospheric pressure in the terminal section of the tunnel and the vacuum in the rest of the network reaches the limit of the first seal, leakage will go past the first seal and if there were no second seal, the leakage would go straight through the valve and cause an undesired depressurisation of the entire network (at least until the section of the next closed valve in the network). However, the second seal resists leakage past it and so the leakage past the first seal will start to pressurise the inter-seal space between the two seals.

The use of more than one static seal on each sealing face of the valve disc also enables the second static seal of each face to function as a back-up seal if the first seal should fail due to wear and tear, mechanical damage or deposit build-up on the valve.

The movable seals (50) may be used in combination with the static seals (40) in instances where additional security of the valve is required.

As noted above, the valve comprises a pair of movable seals (50); one each side of the disc (22), but for simplicity the structure of a single seal is provided below.

The movable seal (50) is typically provided outwardly (i.e. towards the periphery of the disc) compared to the static seals (40).

The structure of the movable seal is shown in more detail in Figure 5. The movable seal (50) comprises a rounded nose (52) which is arranged to be brought into contact with the face of the disc (22).

The nose (52) is an extrusion having a hollow, sealed air cavity (separated from the expansion chamber (58)). The sides of the nose (52) are able to deform when under compression, as a result of pressure from expansion of the expansion chamber (58) pushing the nose (52) forward towards and against the disc (22).

In this arrangement, overinflation of the seal (and possible seal rupture) is avoided as the seal is corseted within the valve body and retaining ring (64). Additionally, the nose (52) is supported and blocked by the closed valve disc (22) to seal on inflation.

A rearward part of the seal comprises two opposing concave side walls (54), which together with the base wall (56) and front wall onto which the nose is mounted (52) define an expansion chamber (58). As the width of the nose (52) is smaller than the dimensions of the front wall, a shoulder (60) is provided on the front face of the seal. The chamber (58) has a single opening, typically in the base wall (56) which is connected to a supply of pressurised fluid via a conduit (62). In use, a degree of flexure of the side walls (54) is permitted, in the direction of displacement of the seal nose (52). The side walls (54) adopt a compact position when pressurised fluid is not applied.

The curved/concave shape of the side walls (54) means that when the pressurised fluid is injected into the expansion chamber (58), the walls can straighten to initially elongate and cause forward motion of the seal shoulder (60) and the seal nose (52). The shape of the side walls (54) also allows for an elastic recoil to pull back the nose (52) to below the surface of the retaining ring (64), without the risk of the nose being left protruding and exposed to the guillotine action of disc closure. This is particularly important in the vacuum environment in which the seal operates as the pressure differential caused by the vacuum is likely to exert a force to pull the nose (52) to an extended position where it is in the line of the disc opening.

The movable seal is constrained in a space defined by a recess in the valve body and a retaining ring (64). The retaining ring (64) is provided with shoulders to cause a transition from a wider channel, in which the main body of the seal is located, to a narrow open-ended channel, in which the nose (52) is located can protrude. This configuration ensures retention of the seal (50) with the valve body, but allows the end of the nose (52) to protrude when inflated/extended through the narrow channel so that it can engage with the face of the disc (22).

The arrangement of the movable seal within the valve body results in a possible vacuum passage down one side of the seal nose which can then pass across the rear part of the movable seal and back out the other side of the nose (effectively a vacuum leak around the back of the seal, even if the seal nose has sealed tight on the disc).

To prevent this back seal leakage from occurring, the seal front shoulder (60) is designed such that upon seal inflation, the shoulders (60) move forward, as the side walls (54) extend, such that the seal front shoulder (60) but against the retaining ring (64) and thereby plug the nose (52) sides leak path.

In addition, during expansion of the seal, the expansion chamber (58) expands within the valve body to form an additional obstruction to leakage around the back of the seal.

Furthermore, as the nose is hollow, the sides of the nose expand sideways when the nose is pushed forwards against the disc. In other words, the additional forward pressure caused by expansion of the expansion chamber increasing the seal-to-disc contact pressure will deform the seal nose side wall outwards to plug tight the disc nose gap on both sides.

The movable seal (50) has a hollow seal nose (52), which is displaced forwardly towards the disc (22) face sealing surface when a pressurised fluid is supplied to the expansion chamber (58) applied. The hollow seal nose (52) is extruded and has a central cavity with air entrapment, isolated from the main expansion chamber (58). As a result, no extrusion or rupture risks of the seal nose can arise, which could compromise its sealing ability. Furthermore, there are no seal wall erosion and seal wall thinning issues since the substantially thick section and resilience of the seal nose (52) absorbs any long-term irregularities and in the retracted state, the seal nose (52) retracts below flush to the retaining ring (64) with no protrusion in the path of the disc. This prevents damage to the nose (52) during raising and lowering of the disc (22) within the valve (10).

When the expansion chamber (58) is provided with pressurised fluid, this does not cause substantial stretching of the walls (54) (as is the case when a balloon is inflated). Instead, the constraining function of the space in which the seal is located and retained prevents any such over-inflation and stretching of the walls (54, 56).

As discussed above, inflation of the expansion chamber (58) creates the force that drives the nose (52) forward to seal against the disc (22). When forward travel of the nose (52) is restricted by the disc (22), the additional pressure causes the sides of the nose (52) to convex outwardly and thereby plug seal the nose gaps. This coincides with the seal shoulders (60) sealing off the internal valve body wall at this point, preventing a searching vacuum passage across the back of the seal.

Actuation of the seal (50) when the disc (22) is partially open position (i.e. non-fully closed) is prevented by the fluid pressurisation system only capable of applying the pressurised fluid to the seal when the disc is in the fully closed position. As discussed above, this prevents damage to the nose (52) of the valve during movement of the disc (22). This control system arrangement may include a sensor and interlocks to determine whether the valve disc (22) is in the fully closed position before any pressurised fluid is applied to the expansion chamber (58) of the movable seal.

The cross-sectional shape and geometry of the movable seal (50) are such to facilitate seal flexure and movement to make good compressive contact with the sealing face of to the disc (22) to effect a seal-tight closure. The seal (50) itself does not expand when actuated. Instead, the fluid pressure within the expansion chamber (58) causes movement of the concertina flexible walls (54) to them to straighten from a contracted condition, to cause the solid section seal nose (52) to move forward into contact with the disc face with sufficient force to make a compression leak-tight seal.

In use, when the pressurised fluid is applied, fluid within the expansion chamber (58) causes the seal to be deployed, i.e. moved forward to engage with the face of the disc. In order to retract the seal, the application of pressurised fluid into the chamber is removed and the seal is then able to relax/retract into the recess in the valve body. This is brought about by the concertina/expansible side walls (54) described above. These have an 'internal memory' to cause the seal to revert to its retracted contracted form, further assisted by a degree of elasticity wall stretch on inflation which recoils on removing the inflation pressure. The retracted seal returns to its original non-protrusion position flush or near flush within its cavity and behind the front of the retaining ring (64).

The seal (50) may be formed by an extrusion process, or a moulding process, with a heat-sealed joint to connect the ends to complete the circular or another shape of the seal. The seal ends jointing technique follows established market technology for a high integrity secure joint. The seal may be formed of silicon or other type of rubber.

A range of pressurised fluids may be used in the expansion chamber (58). The admission of air or hydraulic fluid from a controlled external source (not shown) to the expansion chamber (58) is achieved by routing fluid to an inlet (66) which protrudes from the outside of the valve body (10), but is in fluid communication with the conduit (62) and expansion chamber (58). Typically, a single inlet (66) is required for each of the movable seals (50), on either side of the disc. A common source of pressurised fluid can be used and divided for each side with independent isolation valves and gauges.

The valve is also provided with a seal guard (44) formed from PTFE (polytetrafluoroethylene). This protects the static seals (40) against undue wear or damage from particles and ensures centralisation of the disc, to prevent fouling of the seals. This seal guard also prevents excessive horizontal force (due to horizontal displacement of the disc due to the pressure differential across it) and thus over-compression of the seals on the lower pressure side of the valve.

The valve element may be additionally provided with roller guides (two on each side) to engage with stainless steel guide ribs on both sides of the valve body to ensure lateral disc centralisation, whereas the disc element axial guiding is provided by the PTFE seal guard and seal guide, which controls precisely the degree of allowable lateral movement allowed under differential pressure, to ensure correct static seal compression and anti-cant disc for uniform seal compression leak tightness.

The valve (10) therefore incorporates two entirely different seal arrangements, wherein each seal type is independently engaged. This arrangement has been tested and proven satisfactory with each seal type, achieving effective vacuum sealing performance and body shell test satisfactory vacuum sealed performance. The valve (having a valve opening diameter of 2.2m) was able to maintain a pressure of 10mbar (or any increases were sufficiently low, e.g. less than 5mbar), using either the static seals on their own or a combination of the static and movable seals, for a period of at least 6 hours. An example of the test data obtained is provided in the table below.

Start Pressure Final Pressure Test Time Pressure Rise (mbar) (mbar) (hours) (mbar) 13 14.1 2.5 1.1 7.3 11 20 3.7 10.9 11.9 7 1.0 22.4 22.5 7 0.1 Each individual seal type design has a different functionality, wear characteristics, life cycle, operational performance and consequent failure mode effect. Thus using a combination of the two seal types provides protection against dissimilar failure modes, plus heightened security when combining operation of both seal types in tandem operation. This may be particularly desirable for example, during terminal airlock chamber passenger disembarkation or a tunnel fault requiring a segregation of a section of the network to maintain pipeline vacuum isolation, whilst creating a safe atmospheric zone for tunnel evacuation.

The static seals (40) are simple in their function and only require the valve disc (22) opening and closing to function automatically, with no reliance on external equipment or seal activation. Therefore, the static seals (40) provide a high degree of reliability and are not vulnerable to unexpected failure, but instead only slow seal deterioration over longer time periods, which may be detected as minor leakages, absorbed within tunnel vacuum pumps general system monitoring and planned maintenance.

By contrast, the movable seals have no contact with the disc during opening/closing and therefore no friction wear and a longer life cycle. However, the seal life is not the only consideration as unlike the static seals, the movable seals require auxiliary equipment for seal operation. Combining the two different types of seal each independently tested to satisfy vacuum tight seal functionality, but having contrasting operational methodology and different failure modes, is considered to introduce a novel approach to this critical vacuum isolation challenge, which legislates for most eventualities and highest degree of safety.

The present invention therefore offers a dual seal high integrity valve shut-off, operated either independently or combined for ultimate security shut-off to suit operational safeguarding requirements, while preserving longer-term life cycle seal option alongside long-term planned maintenance.

As noted above, movement of the disc is operated under balanced pipeline pressure conditions, to avoid a differential pressure build up, while the disc is in motion. Therefore, the disc displacement towards and away from the seals and increased seal friction on the downstream face are avoided. This is also reduced as a result of the seal guard (44). These considerations therefore improve the lifespan and performance of the static seals (40).

Nevertheless, as the static seals (40) are under constant compression contact with the valve disc (22), an element of long-term friction wear of the seals can be expected with eventual planned maintenance replacement. This can be carried out with relative ease from inside the valve with no valve dismantling or removal and no heavy or special equipment.

The static seals (40) and movable seals (50) can be replaced in-line by man-entry into a section of the tunnel either side of the valve under atmospheric pressure. No dismantling of the valve itself is required and this minimises the interruption caused by the minimal maintenance. The retaining rings which hold the seals in place are installed in segments for ease of man-handling without lifting equipment (noting that a single, non-segmented retaining ring for use in vacuum transportation systems or other large pipelines valves would weigh many tonnes).

The design of the valve therefore allows seal replacement within the tunnel without removal or major dismantling of the valve, thereby allowing seal replacement by man entry from inside the valve and removal of the retaining ring(s) which are of manageable size and weight segments. Once the retaining ring is removed, the seal can be renewed and retaining rings refitted and screws torque tightened.

As noted above, although the valve is described as being mounted in a vertical position, it could equally be installed in a horizontal position. When horizontally positioned, it will be appreciated that the valve may also be provided with a track at its bottom, on which the bottom side of the disc would be supported and slide as the valve opens and closes.

The present invention provides an isolating valve which is leak-tight and bi-directional and ensures that seal performance is upheld irrespective of design geometry construction variances. Figure 8 shows FEA (finite element analysis) modelling for the valve of the present invention. The modelling demonstrates that the final constructional strength far exceeds that required for vessel strength of the media pressure acting on the body shell surface areas, or internal horizontal forces acting on valve-closed disc resultant from applying maximum different pressure to disc surface area. The maximum stress across the body rib edge is 195MPa, but is only about 8MPa at the sealing area. The maximum stress in the middle of the moveable element is 30MPa but at the sealing area only about 9MPa. Most notably, the body maximum displacement is 3.4mm and body sealing area about 0.04mm. The maximum displacement in the middle of the moveable is 0.5mm and at the edge of the sealing area is only 0.1mm. The construction of the valve therefore ensures rigidity with minimal distortion in the valve body and disc sealing area that is within the small tolerance of resilient (or metal) seal capability to adjust and retain sufficient sealing compression to hold the vacuum seal seat tightness.

The combination of mating seal components surface finish for vacuum sealing and the valve construction rigidity to maintain overall sealing performance, is of paramount importance to achieve vacuum sealing at a large scale.

Claims

CLAIMS1. A gate valve suitable for a hyperloop transportation system, the valve comprising a valve body, and a valve element movable within the valve body, and one or more static seal(s) and one or more movable seal(s).

2. A valve according to claim 1 wherein the valve element comprises two opposed faces, spaced from the transverse plane of the valve element, wherein the valve body is provided with one or more static seals and one or more movable seals on each side of the valve element to sealingly engage with a portion of the valve element, when closed to seal the valve element against the valve body.

3. A valve according to claim 1 or claim 2 wherein the valve additionally comprises one or more static valves on each side of the valve element.

4. A valve according to any one of claims 1 to 3 wherein the valve body comprises a front plate and back plate, wherein each plate comprises at least one seal static seal and at least one movable seal.

5. A valve according to claim 4 wherein each of the front and back plates of the valve body comprise two static seals, which are optionally annular in shape and concentrically mounted.

6. A valve according to any one of claims 1 to 5 wherein the movable seal is aninflatable seal.

8. A valve according to any one of claims 1 to 6 wherein the movable seal is concentric with and outside or peripheral to at least one of the static seals.

8. A valve according to any one of claims 1 to 7 further comprising a seal guard concentric with at least one of the static seals to protect the one or more static seals from damage during use of the valve.

9. A valve according to any of claims 1 to 8 wherein the movable seal is expandable and/or contractable by virtue of entry and/or exit of a fluid into the seal.

10. A valve according to claim 9 wherein the seal is inflatable and is capable of receiving and/or containing a fluid under pressure.

11. A valve according to claim 9 or claim 10 wherein the movable valve has an internal cavity, for a fluid to enter and/or exit, and can expand to create a seal on entry of a liquid or air.

12. A valve according to any of claims 8 to 11 wherein the movable seal is circular, or annular, continuous and/or comprises a hollow compartment.

13. A valve according to any one of claims 8 to 12 wherein the movable seal comprises a hollow nose portion, which engages with the valve element when the seal is inflated.

14. A valve according to any one of claims 8 to 13 wherein the internal cavity is defined by side walls of the seal which join the rearward wall and nose portion and are shaped to enables them to expand to a position where the rearward wall and nose portion are distanced apart from either other further than when the side walls are in a contracted position.

15. A valve according to claim 14 wherein the side walls are concave in shape.

16. A valve according to any one of claims 1 to 15 wherein the valve element is a gate having has a half-crescent shape or substantially (semi-) circular cutout or recess.

17. A valve according to any one of claims 1 to 16 wherein the valve element is a gate having a shape that substantially aligns with the top of the valve opening (when the valve is in the open position).

18 A valve according to any one of claims 1 to 17 wherein the valve element comprises a raised annular section on one or both of its faces, which engages with one or more of the seals when the valve is closed.

19. A valve according to any one of claims 1 to 18 wherein the valve element is a gate having one or more chamfered edges.

20. A valve according to any one of claims 1 to 19 comprising a stem that extends to the exterior of the valve body and is connected or connectable to a motor, which can effect rotation of the stem and movement of the valve element.

21. A valve according to claim 20 wherein the stem is encompassed within a stem housing at a position external to the valve body, the stem housing comprising a channel through which the stem passes.

22. A valve according to claim 21 wherein the channel in the stem housing comprises one or more stem seals (e.g. 0-rings).

23. A valve according to any one of claims 20 to 22 comprising one or more compressible rings surrounding the stem within the valve body and against an interior wall of the valve body.

24. A valve according to claim 23 wherein the valve element is provided with a ring-engaging surface, which pushes against the compression rings when the valve element is in a raised position.

25. A hyperloop (vacuum) transport system comprising one or more valves according to any one of claims 1 to 24.