AU2018101369B4 - Vent valve, vent vale insert and method of operation of a vent valve - Google Patents

Abstract

A vent valve assembly 10 mounts to and above a vent valve body 12 housing a float 14. The float is coupled to an actuator 16. The vent valve body 12 has a lower coupling 26 for connection to a pipeline or other installation to supply fluid to the vent valve body via a vent valve body inlet opening 28. The float moving to this upper end of its travel, via the actuator, in turn causes a first valve sealing member 48 of the vent valve assembly to lift, which closes the first valve member seal 50 (e.g. a seal at the end of the first valve member 'needle valve') against the first valve seat 29 to seal the first valve seat orifice 54. The first valve seat 29 is provided in a housing 32 of a valve device 30. A second valve sealing member 34 is provided externally at an end of the housing. The second valve sealing member 34 has a second valve seal 36 arranged to seat/unseat with a respective second valve seat 38. The second valve provided by the second valve member seating/unseating on the second valve seat is urged upwards by movement of the housing of the valve device 30 to close off the second valve seat when the float rises sufficiently. The vent valve is fully closed with both first and second valves seated. The first valve and the second valve seal can move up or down as a total unit, but the first valve member can move relative to the first valve seal to 'break' (open) the first valve before the second valve opens.

Description

VENT VALVE, VENT VALE INSERT AND METHOD OF OPERATION OF A VENT VALVE

FIELD OF THE INVENTION [0001] The present invention relates to a valve for venting gas, such as from pipes, pipelines, industrial process equipment or vessels, such as for removing gas from water conveying pipelines.

[0002] Application for one or more forms of the valve of the present invention is found in venting gas from pipes/pipelines and other equipment conveying/containing water extracted from below ground.

[0003] A non-limiting example of the vent valve of the present invention is found in high point vent valves for venting methane and/or other gases from water gathering pipelines of coal seam gas operations.

BACKGROUND TO THE INVENTION [0004] Gas vent valves are used to remove and/or prevent build-up of excess or unwanted gas from pipelines conveying liquid, such as pipelines conveying water or predominantly water.

[0005] For example, a gas vent valve is used to vent unwanted gas from water gathering lines of coal seam gas pipelines/installations. Such vent valves are often called ‘air vent valves’ but may vent gas(es) other than air or a mixture of air and other gas(es), such as venting methane from ground water obtained during coal seam gas production.

[0006] Coal seam gas (CSG) derives from naturally occurring gas trapped in underground coal seams by water and ground pressure. The coal seam gas is

2018101369 18 Sep 2018 present in open fractures between the coal (called cleats) and the inside of the pores within the coal (the matrix).

[0007] Coal seams store both coal seam gas and water. The water is under pressure from the weight of overlying rock. The water keeps the underlying coal seam gas in place, and the coal seam gas is released when the water pressure is sufficiently reduced.

[0008] Drilling a well into the coal seam during coal seam gas production reduces the pressure and the water is then pumped out of the seam. The gas can then flow to the surface via the well and is then piped to production facilities where it is dried, compressed and piped to customers for use, storage or transport.

[0009] The water removed during coal seam gas production can vary between fresh water containing very few other elements, to saline or high turbidity water. Such water is either stored in pools or treated to remove contaminants and/or unwanted elements before use.

[0010] Pipelines are utilised to manage production, treatment and distribution of water derived from coal seam gas production processes.

[0011] Water gathering lines provide a low pressure water gathering system installed from each well head to collection/aggregation dams at each treatment facility. Transfer pipelines connect dams within and between treatment facilities to manage variations in coal seam gas water production. Distribution pipelines provide a network to convey treated and/or untreated water to end users/storage/further treatment.

[0012] For example, the water (treated or untreated, depending on prevailing regulations/legislation at the site) may be injected into the ground to mitigate loss of water pressure during the coal seam gas extraction process. Alternatively, the

2018101369 18 Sep 2018 water may be used, within regulations, for agricultural irrigation, return of water to waterways, or watering of civic parks and grassed areas.

[0013] Vent valves are used in coal seam gas dewatering processes, such as in water gathering and other lines to remove excess or unwanted gas from ground water extracted during the coal seam gas production process. Such gas can include methane and/or other gas(es), such as air.

[0014] Where the pipeline transitions from an incline to a decline, gas conveyed along with water in the pipeline, or coming out of solution from water conveyed in the pipeline as pressure drops, the gas can collect at the high point. High point vent valves provide gas venting at high points along the extent of a dewatering pipeline.

[0015] If sufficient gas collects at the high point, a compressed gas ‘bubble’ can form, potentially blocking the entire internal bore of the pipe. Zero water flow may occur due to this gas bubble blockage at the high point. This results in enormous strain being put on pumps still trying to pump the water along the pipeline. This risks premature wear or even failure of the pumps.

[0016] Given that water is incompressible and the gas is compressible, the compressed gas can act as a spring, storing energy. If the pumps cease pumping, the stored ‘spring’ energy in the compressed gas can be unleashed, risking catastrophic failure of the pipeline and associated equipment.

[0017] Standard high point vent valves often do not cope with continuous large amounts of gas/gas pressure build up at the high point, resulting in the high point vent valve continuously venting to try to reduce the gas pressure. Due to supply of gas within the pipeline being much greater than the capacity of the vent valve to vent the gas, the high point vent valve can continuously vent without actually reducing the gas pressure to the point where the vent valve can shut.

2018101369 18 Sep 2018 [0018] Simply enlarging the diameter of the vent valve orifice does not overcome this problem entirely. Enlarging the single vent valve orifice means that the vent valve seal has to also be large in order to seat on the valve seat about the vent valve orifice when the valve is closed. This increases the surface area of the vent valve seal. The high internal pressure within the valve resulting from the high gas pressure can hold the vent valve shut against external atmospheric pressure. The seal can remain closed through pressure differential across it (pressure inside the valve being greater than external, atmospheric pressure), and given the float is connected directly to the seal via a rod and linkage, the float is forced to “hang up” inside the main body i.e. the float does not drop, the seal being held closed by the pressure differential also holds the float in the upper most position as if the float was actually buoyed by water and positioned in the closed attitude. The vent valve would therefore not open at all.

[0019] In industry, vent valves are expected to release gas/gas pressure within a minimum opening operating pressure and up to a maximum working pressure.

[0020] Also, vent valves are required to seal at low pressures, and this is difficult to achieve with a large orifice as the seal footprint is necessarily larger and there is less force per unit area applied to the seal.

[0021] Achieving low pressure sealing capability (e.g. 20 kPa) plus the ability to reliably vent at high pressures is a very difficult combination.

[0022] In the coal seam gas industry, it is essential that no atmospheric air enters the pipeline if suction (negative pressure) conditions are inadvertently experienced. This requires any CSG High Point Vent (HPV) to include reliable non-vacuum breaking - to preclude the ingress of air otherwise an explosive mixture risk is created within the pipe.

2018101369 18 Sep 2018 [0023] Historically, vacuum breaking has been achieved by a mechanical flap augmentation or non-return valve to the vent valve and these have proven to be unreliable.

[0024] Existing Gas release valves on water gathering lines in the CSG (Coal Seam Gas) Industry:

• do not necessarily provide full venting function up to nameplate (maximum reliable) pressure, • do not have sufficient venting capacity • require extensive maintenance. The water media contains significant suspended solids (coal fines and inter-burden) and this results in strainers having to be fitted before the valve and therefore expensive maintenance programs to regularly clean out the strainers, • can exhibit a reluctance to vent “early” enough to provide an effective gas release • must include one way venting only i.e.: do not vacuum break. Existing valves achieve vacuum breaking via a mechanical add-on device or by augmentation such as a non-return valve. These are inherently unreliable and can fail, thus introducing atmosphere (oxygen) back into the pipeline and so creating an explosive mix (with methane still present in the pipeline) and severe safety concern [0025] Valves in the field may approach nameplate pressure, but stop functioning earlier in the rise in the pressure curve simply as a result of pressure differential. In other words, higher pressures simply hold the float and seal

2018101369 18 Sep 2018 system up in their closed attitude because of the difference in pressure across the seal and external pressure (atmosphere).

[0026] Mechanical strainers have also been used to filter contaminants that can infiltrate and compromise/degrade seals, thus rendering the valve either inoperative or leaking, the latter often being a regulatory body reportable offence, but these strainers require regular cleaning which results in high maintenance costs.

[0027] Failure to carry out an effective maintenance program invites the risk of a leaking vent valve (or one that does not work at all) and because of the salinity of the water (approx 7000 total dissolved solids (TDS)), if the leak is sufficient, e.g. 20 litres or more, environmental reports may need to be drafted and submitted to the regulatory body for environmental impact, severity assessment and possible penalties.

[0028] It is with one or more of the aforementioned problems in mind that the present invention has been conceived.

[0029] It has been found desirable to provide a vent valve that ameliorates or addresses one or more of the aforementioned problems.

[0030] Whilst one or more embodiments of the present invention are described herein in relation to venting of gas in dewatering systems for coal seam gas production, it will be appreciated that the present invention is applicable to other applications where gas is to be vented from a pipeline, process or vessel.

SUMMARY OF THE INVENTION [0031] With the aforementioned in mind, an aspect of the present invention provides a vent valve assembly for use in venting excess gas or gas pressure, the vent valve assembly including a first valve and a second valve providing two

2018101369 18 Sep 2018 stage pressure release valving to vent gas pressure from a vent valve body housing a float arrangement, the vent valve assembly actuated by the float arrangement in response to sufficient gas pressure within vent valve body and associated reduced level of liquid within the vent valve body.

[0032] Preferably the vent valve assembly includes a valve device having a first valve seat and respective first valve sealing member, and a second valve sealing member or second valve seat, wherein the first valve seat, the first valve sealing member and the respective second valve seat or second valve sealing member are arranged within the valve assembly to move relative to the corresponding second valve sealing member or second valve seat.

[0033] The vent valve assembly may be mounted substantially external to the vent valve body. This helps to prevent contaminants entering the vent valve assembly.

[0034] The vent valve assembly, being external to the vent valve body, advantageously creates separation from any fluid (and any solids entrained in the fluid) within the body. Known vent valves for releasing gas/gas pressure, particularly in pipelines, have the valve mechanism within the body, which makes them prone to premature wear, blockage or failure from liquid containing contaminants, such as organic/coal fines entrained in water from a coal seam gas operation.

[0035] Preferably the valve device is actuated by an actuator provided within the vent valve body and connected to a float of the float arrangement.

[0036] The first valve sealing member may allow the second valve sealing member to operate.

[0037] The first valve may have a first valve orifice providing a smaller overall orifice area than the second valve orifice of the second valve.

2018101369 18 Sep 2018 [0038] Preferably the second valve sealing member may be connected to or form part of a housing for part of the at least one first valve sealing member.

[0039] The first valve sealing member may have a sliding captive fit within the housing of the valve device.

[0040] Preferably the first valve has a seal and/or the second valve has a seal material of nitrile silicon.

[0041] Another aspect of the present invention provides a vent valve device having a first valve sealing member, a first valve seat and at least one of a second valve sealing member and second valve seat, the vent valve device arranged to be received into a body for a vent valve assembly.

[0042] Therefore, according to one or more forms of the present invention, the vent valve device may be provided as a replaceable insert, such as in the style of a replaceable cartridge, to replace worn components of a vent valve assembly.

[0043] A further aspect of the present invention provides a method of venting gas pressure, the method including operating a two stage vent valve assembly having a first valve having at least one first valve orifice, and a second valve having at least one second valve orifice, the at least one second valve orifice providing a larger orifice surface area than the at least one first valve orifice, the method including opening of the first valve to initially release excess gas/gas pressure which opening enables opening of the second valve to provide increased rate or volume of gas pressure release.

[0044] Preferably the method includes opening of the first valve moves a first valve sealing member which causes movement of a second valve sealing member.

2018101369 18 Sep 2018 [0045] An actuator connected to a float within a vent valve body containing the gas pressure to be released may actuate the first valve sealing member.

[0046] Opening of the first valve preferably vents at least some of the gas pressure via the valve assembly, which venting preferably reduces gas pressure differential across the second valve prior to the second valve opening.

[0047] Movement of the first valve sealing member opening the first valve may cause a housing of the valve device to move, sufficient movement of the housing of the valve device opening the second valve.

[0048] The second valve sealing member may be provided at an end of the valve device, and the first valve sealing member may extend from an opposite end of the valve device. Preferably the first valve sealing member may be a sliding captive fit within the housing of the valve device.

[0049] The actuator may include at least one a lever/rod operatively connected to, or operating on, the at least one valve member of the vent valve assembly.

[0050] The valve device may be connectable, directly or indirectly, to the body. The valve device may be substantially or completely external to the body.

[0051] At least one form of the present invention may provide a vent valve incorporating the vent valve assembly and the body housing the float arrangement.

[0052] Alternatively, the vent valve assembly may be provided as a component for mounting to an in situ body, such as being a retrofit component for an existing vent valve body and float assembly.

2018101369 18 Sep 2018 [0053] Preferably the vent valve assembly is provided to vent gas from a pipeline or vessel. For example, the vent valve may provide a controlled flowpath for gas to be vented from a pipeline to atmosphere or be captured to be reclaimed. The vent valve assembly may include a connection or fitting to a gas capture or reclamation system to prevent the released gas simply venting to atmosphere and/or for reuse or storage of the gas vented gas. Preferably the vent valve is arranged and configured to vent gas from a dewatering pipeline of a coal seam gas related operation.

[0054] According to one or more particular embodiments of the present invention, the vent valve assembly may be attached to an upper portion of the body. For example, the seal module may be attached by a threaded connection to an upper cover (aka ‘top cap’) of the body or to a conduit extending from the top cover.

[0055] Preferably the at least one valve seat includes an orifice for passage of the gas. More preferably the valve assembly includes a multiple valve seat system. Preferably each said valve seat includes at least one orifice for passage of the gas. The multiple valve seat system may be provided as part of the vent valve device.

[0056] The multiple valve seat system may include two valve seats providing a first valve seat with an associated at least one first valve seat orifice, and a second valve seat with an associated at least one second valve seat orifice.

[0057] The first valve sealing member may be provided to control flow through the at least one first valve seat orifice.

[0058] The second valve sealing member may be provided to control flow through the at least one second valve seat orifice.

2018101369 18 Sep 2018 [0059] The first valve sealing member may operate to allow the second valve sealing member to operate. For example, unseating of the first valve sealing member from the respective first valve seat may allow the second valve sealing member to unseat from the respective second valve seat.

[0060] Preferably, unseating of the at least one first valve sealing member from the first valve seat allows gas/gas pressure to flow through the at least one first valve seat orifice, which decreases pressure on the first valve side upstream of the least one second valve sealing member, which consequently decreases pressure differential across the at least one second valve seat. That is, decreased pressure against the at least one second valve sealing device reduces the pressure differential across that second valve mechanism (second sealing device and second valve seat arrangement) that has ambient/atmospheric pressure external thereto. Because of this reduction in pressure differential across the second valve, movement of the at least one first valve can open the second valve to allow higher volume gas venting than would happen with a single large vent valve orifice and no smaller initial stage first valve. This ‘two stage’ process improves opening control of the at least one second valve sealing member, and allows high volume gas/gas pressure venting and reduces the risk of sudden, uncontrolled or limited low volume pressure release from the vent valve assembly.

[0061] Preferably the at least one first valve seat orifice provides a smaller overall orifice area than the at least one secondary valve seat orifice. This two stage (smaller then larger) orifice area allows improved controlled pressure release and rate of gas release.

[0062] Preferably the at least one second valve seat is downstream of the at least one first valve seat relative to gas flow from the body through the valve assembly (e.g. from the pipeline through the valve assembly to atmosphere).

2018101369 18 Sep 2018 [0063] The valve assembly is actuated to release gas/gas pressure by the float falling depending on water level falling sufficiently within the main body. The falling float acts on the actuator to cause the vent valve device to open and release gas/gas pressure. As water level rises within the body, the float rises with the water level, causes the actuator to act on a valve member to close or partially close the vent valve device depending on the level of water within the body.

[0064] The multiple valve seat arrangement preferably opens (and preferably closes) progressively to improve control of gas/gas pressure release, and preferably, to modulate and provide soft anti-hammer closure when closing.

[0065] Preferably, the first valve sealing member seats on the respective first valve seat, and the second valve sealing member seats on the respective second valve seat, when the vent valve device is closed. When the valve assembly is fully open and venting gas/gas pressure, each said first and second valve sealing member is unseated from its respective valve seat.

[0066] In use, preferably the first valve sealing member unseats from the respective first valve seat before the second valve member unseats from the respective second valve seat. Thereby providing the two stage consecutive valve opening arrangement.

[0067] According to one or more embodiments of the present invention, the at first valve sealing member, the respective first valve seat and the second valve sealing member may, in use, all move relative to the at least one second valve seat.

[0068] For example, the first valve sealing member may have a sealing surface which contacts the first valve seat and blocks the at least one first valve seat orifice. And the first valve seat may be attached to the at least one second valve sealing member.

2018101369 18 Sep 2018 [0069] Gas pressure passing the unseated first valve sealing member and through the at least one first valve seat orifice may allow the respective second valve member to operate by gravity and/or higher external atmospheric pressure. It will be appreciated that opening the first valve helps to reduce pressure across the second valve, making opening of the second valve easier and more controlled.

[0070] Alternatively, or in addition, movement of the at least one first valve sealing member may cause the at least one second valve sealing member to unseat from the respective at least one second valve seat. For example, the at least one first valve sealing member may have or be connected to a portion that impacts part of the at least one second valve sealing member.

[0071] The at least one second valve sealing member may be connected to or form part of a housing for part of the at least one first valve sealing member. For example, at least a portion of the at least one first valve sealing member may extend into the housing associated with at least one second valve sealing member.

[0072] The at least one first valve sealing member may have a sliding captive fit within the housing. For example, a portion of the at least one first sealing member may extend through an aperture of the housing. A first portion of the at least one first sealing member external to the housing may connect to the actuator associated with the float arrangement. A second portion of the at least one first sealing member within the housing may have at least one projection which prevents that portion of the at least one first sealing member exiting the aperture of the housing.

[0073] The actuator of one or more embodiments of the present invention may include at least one lever arm member, preferably attached directly or indirectly to the float.

2018101369 18 Sep 2018 [0074] The at least one lever arm may connect by a pivot or articulation joint to at least one elongate member, such as one or more rods, which in turn may connect to the float. Advantageously, mechanical advantage is gained when the float rises, causing the rod(s) to move the end(s) of the lever(s), the lever(s) then causing the valve assembly to close when the float rises sufficiently. The at least one lever may be connected to the float (such as by an articulation or pivot joint) i.e. not utilising the rod(s). However, having the additional mechanical advantage by having the rod(s) connected between the float and the end(s) of the lever(s) permits increased upward force on the first valve member.

[0075] Preferably, as the float sufficiently rises due to liquid (e.g. water) within the body, a said lever arm member may contact a valve stem of the at least one first valve sealing member to operate the at least one first valve sealing member to maintain the first valve closed (the presence of sufficient liquid to lift the float indicating that little or no gas/gas pressure is present above the float.

BRIEF DESCRIPTION OF THE DRAWINGS [0076] One or more embodiments of the present invention will hereinafter be described with reference to the accompanying drawings, in which:

[0077] Figure 1 shows a sectional view of a vent valve assembly mounted above and external to a float housing according to an embodiment of the present invention.

[0078] Figures 2a to 2c show various views relating to a vent valve assembly according to an embodiment of the present invention. Figure 2a shows an external side view of the vent valve assembly. Figures 2b and 2c show horizontal sectional views F-F and G-G, as indicated on Figure 2a.

[0079] Figure 3 shows a vertical sectional view (E-E) through the vent valve assembly of Figure 2a, as indicated on Figure 2a.

2018101369 18 Sep 2018 [0080] Figure 4 shows an exploded cross sectional view of a valve assembly incorporating an embodiment of the present invention.

[0081] Figure 5 shows an exploded isometric (perspective) view of a valve assembly incorporating an embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT [0082] As shown in Figure 1, a vent valve assembly 10 according to an embodiment of the present invention is mounted substantially external to and above a vent valve body 12 housing a float 14.

[0083] The float is coupled to an actuator 16. The actuator, in the arrangement shown in Figure 1, includes two arms 18a, 18b articulated with respect to one another by an articulation joint 20. An end of one of the two arms is pivotably connected 22 at a cover 24 of the vent valve body. The opposite end of the actuator is pivotably mounted at a pivot joint 19 to a mount 21 on the top of the float 14.

[0084] The vent valve body 12 has a lower coupling 26 for connection to a pipeline or other installation to supply fluid to the vent valve body via a vent valve body inlet opening 28.

[0085] Operation of the vent valve will now be described in relation to gas relief from a dewatering system of a coal seam gas installation. For example, coal seam gas production often utilises a low pressure dewatering system for removal of ground water, as previously described. Such ground water can contain gas, such as methane, which needs to be vented from the dewatering system in quantities far more than a conventional pumping process.

2018101369 18 Sep 2018 [0086] When there is negligible gas captured within the vent valve body, the water level is high and the float is buoyed in its upper-most position (i.e. toward the cover 24) with respect to the vent valve body.

[0087] The float moving to this upper end of its travel, via the actuator, in turn causes the first valve sealing member 48 of the vent valve assembly to lift, which closes the first valve member seal 50 (e.g. a seal at the end of the first valve member ‘needle valve’) against the first valve seat 29 to seal the first valve seat orifice 54.

[0088] As shown with reference to Figures 3, 4 and 5, the first valve seat 29 is provided in a housing 32 of a valve device 30. A second valve sealing member 34 is provided externally at an end of the housing. The second valve sealing member 34 has a second valve seal 36 arranged to seat/unseat with a respective second valve seat 38.

[0089] It will be appreciated that the second valve seat may be provided on the housing for the first valve, and the second valve sealing member may be provided on the upper housing 42 i.e. the second valve sealing member and the second valve seat, providing the high volume gas relief/seal function, may be vice versa.

[0090] The housing 32 for the valve device 30 having the first valve can optionally have one or more ports 39 below the first valve for the transfer of gas/gas pressure through a side wall of the housing to one or more passages/clearances between the sleeve 31 and the housing 32 to provide at least one gas/gas pressure relief pathway 41 around the first valve to reach the second valve. The second valve opening relieves this gas/gas pressure through the second valve seat orifice(s), and also helps to ensure that the housing drops when the first valve opens.

2018101369 18 Sep 2018 [0091] The second valve provided by the second valve member seating/unseating on the second valve seat is urged upwards by movement of the housing of the valve device 30 to close off the second valve seat when the float rises sufficiently. In this attitude the vent valve is fully closed with both first and second valves seated.

[0092] The first valve seal end of the first valve member is preferably held captive within the housing (for example, only by disassembly valve device can the first valve member’s first valve seal be withdrawn from the housing).

[0093] The first valve (first valve seal and first valve seat) and the second valve seal can move up or down as a total unit, but the first valve member can move relative to the first valve seal to ‘break’ (open) the first valve before the second valve opens.

[0094] In operation, the first valve 30 opens first, this releases some pressure in the main body housing the float (which has lowered due to the presence of gas/lack of water in the body housing) thus reducing the overall pressure differential on the larger second (primary) orifice seal and promoting its opening and consequential high volume venting. Both valves (first and second) are automatic in operation once the float drops, meaning that they will open as required and vent gas from a pressurised pipe/vessel.

[0095] It will be appreciated that the head 48a of the first valve sealing member can have ports for gas/gas pressure to flow to the first valve seal 50 and/or faced sides to reduce contact with the cylindrical interior side wall of the housing 32. This latter feature not only reduces friction to help the first sealing member to drop to open the first valve, but also allows passage of gas/gas pressure from under the first valve sealing member to flow around the seal end of the first valve sealing member and to pass through the first valve seat aperture(s).

2018101369 18 Sep 2018 [0096] As shown in figure 3, gas/gas pressure flow through the first valve is shown in short/close dotted lines, whilst higher volume/flow rate through the open second valve is shown in longer dotted lines. It will be appreciated that both flows (initial flow from the first valve opening, and higher flow volume/rate through the second valve opening) both pass through the orifice(s) of the second valve, but the initial flow from the first valve opening does so without the second valve sealing member lifting from its seat.

[0097] Automatic (auto-venting) valves assemblies having a largest orifice as large as say 10mm diameter are not known because it is impractical and/or difficult to get them to open up as a result of high internal pressure compared to atmosphere. The pressure within the pipe/vessel can be significantly higher than atmosphere and helping to hold the known valve shut.

[0098] Advantageously, the two stage process/valving of aspects of the present invention allows the smaller first valve to open first, giving the larger second (primary) valve a smaller pressure differential across that second valve to help it to open.

[0099] The second vent valve seal may preferably be provided by a 45 degree mitre seal. Preferably the seal material is nitrile silicon. In use, the second valve seal pushes up against the second valve seat to at least partially block the second valve orifice (preferably being a 10mm orifice).

[00100] The smaller first seal and the larger second seal are preferably part of a valve device, with the first seal contained within a housing. The first small sealing device is allowed to float or ‘modulate’ a few mm within that housing and break its seal from the first valve seat, while the entire housing can drop a few mm (e.g. approx 3mm) thus opening the main or primary (large) second orifice to open as well - all actuated by the level of the float, which incorporates a lever action to increase mechanical advantage and force on the seals to enhance low pressure closing - i.e.: no leaks

2018101369 18 Sep 2018 [00101] As gas collects in the upper portion of the vent valve body, the level of water decreases in the vent valve body, the float drops which in turn pulls down on the first valve member, allowing gas collected in the vent valve body housing the float to escape through an air transfer passage and out the top outlet.

[00102] This action creates a reduction in pressure within the main body housing and, depending on prevailing pressure conditions and the amount of gas in the main body, the float can then drop further which opens the second valve (the primary or larger valve) orifice for higher capacity venting. Once the gas has been liberated, the water line inside the main body rises, the float is buoyed and the vent valve is closed.

[00103] It will be appreciated that the vent valve may cycle, opening and closing either the first valve (the smaller of the two vent valve orifices) on its own or both the first and second (item 5) vent valves, depending on the amount of gas that needs to be released. The presence of the first (small orifice) seal in conjunction with the second seal (primary of large orifice) results in soft closure and negligible risk of water hammer.

[00104] Therefore, at higher gas pressures, the first vent valve orifice is easily opened, lowering the vent valve body internal pressure enough to allow the second vent valve (primary or larger seal/valve) to open if the volume or pressure of gas mandates that higher volume/release rate opening.

[00105] At high pressures (approx >1600 kPa) other known valves will remain closed and do not function as a result of pressure differential across their (typically) larger single orifice.

[00106] It will be appreciated that one or more embodiments of the present invention can have a second valve (primary or larger of the two valves) orifice at 10mm diameter (78.6mm² or multiple orifices/ports equivalent thereto) larger than

2018101369 18 Sep 2018 any other know vent valve. This provides embodiments of the present invention with increased capacity venting compared with known vent valves.

[00107] The first valve orifice at preferably 2.2mm diameter (3.8mm²) gives a total dual (first and second) orifice cross section of 82.40 mm².

[00108] As shown in the cross section of the embodiment in Figure 3, the vent valve assembly 10 can have a first (lower) body 40 and a second (upper) body 42.

[00109] A sleeve 31 is situated within the lower body 40. The sleeve has a shoulder 33 to stop downward travel of the first valve sealing member when the first valve opens.

[00110] Preferably one or more passages 35 is/are provided between the sleeve and the lower body 40 for gas/gas pressure to travel from the float body, around the first valve, to wait at the second valve seal until the second valve opens. Higher volume gas pressure relief can then be provided by operation of the second seal and its associated relatively larger orifice area compared with the lower volume, smaller orifice area provided by initial pressure relief from the first valve.

[00111] Gas/gas pressure can pass from the float body, through one or more apertures 37 through the plate 46 at the base of the valve assembly, to reach the one or more passages.

[00112] A valve device 44 is housed within the first body. The valve device has the first vent valve (first valve seal and first valve seat) and has at the upper end of the valve device the second valve seal 36.

2018101369 18 Sep 2018 [00113] A retainer 46, such as an aperture plate, having an aperture for the first valve member to extend therethrough, is provided at the base of the first (the lower) body 40.

[00114] As shown in Figure 4, the first valve sealing member 48 can have a flange 45 which abuts against a shoulder 43 of the housing 32 when the first valve sealing member drops to open the first valve. Impact of the flange 45 with the shoulder 43 helps to lower the housing and thereby help to cause the second valve to open and allow higher volume/flow rate of gas/gas pressure for relief through the second valve compared to the volume/flow rate capacity of the first valve. The initial pressure relief provided by the first valve opening in this two stage valve assembly helps to reduce the high pressure within the float body and thereby also assist the second valve to open.

[00115] A check valve 56 prevents intake of atmospheric air or other gas back in through the vent valve assembly 10. This check valve preferably includes a ball 58 in an outlet chamber 60 which seats against a tapered check valve seat 62. A removable screw-in plug 64 with a vent channel 66 therethrough retains the ball within the outlet chamber.

[00116] Under test, at least one embodiment of the present invention has proven to operate (vent gas from pressurised water pipelines) all the way to nameplate pressure (2500 kPa). Other units on the market are rated at similar or even higher pressures but close prematurely and fail to provide full function through to their nameplate pressure rating. This means no gas is being vented and pumping inefficiencies result. Flow may even stop in extreme cases when gas pockets are not liberated and pumps simply “Dead Head”. One or more embodiments of the present invention can continue to operate to a nominated (nameplate) pressure providing full system protection, including elimination of high pressure surges and optimal pumping efficiency

2018101369 18 Sep 2018 [00117] The vent valve assembly of the present invention is completely or at least substantially external to the main body of the valve (bearing in mind that a screw thread portion may be screwed into the top cover of the valve float body).. This means the primary media (water with suspended solids) cannot come in contact with or compromise the seals within the vent valve assembly. There is therefore no requirement to fit a mechanical strainer (filter) to prevent these contaminants entering the valve body. Maintenance that involves flushing the strainer and valve regularly is then eliminated. Given that known High Point Vent (HPV) valves are installed by the thousands in rural and remote locations worldwide, the cost of maintenance is enormous. It is not out of the ordinary to service a given valve/strainer combination on a weekly basis. Therefore, an improved vent valve that can manage to operate effectively without regular cleaning while still capable of operating full function to nameplate pressures has significant economic and practical advantage.

[00118] Preferably, one or more embodiments of the present invention can operate effectively up to 12 degrees off-vertical in any rotational orientation. Often artificial high points are created by “Trench Humping” and this can affect the sealing capability of other valves as floats and mechanisms demand to be installed in close to perfect vertical attitude.

[00119] Embodiments of the present invention incorporate a robust, reliable and effective non-vacuum breaking feature that is an integral part of the vent valve assembly and is not an additional device needed to augment other valves.

[00120] With no requirement of an optional additional cost component, the present invention can be configured on-site to vent to atmosphere as is the current practice, or to be plumbed to capture and return vented gas to the main gas gathering pipeline [00121] One or more embodiments of the present invention operates effectively without a strainer and vents gas only, there is no fluid discharge (mist) and the

2018101369 18 Sep 2018 seals remain dry and contaminant free. This results in extremely reliable operation and reduced need for costly and time consuming maintenance.

[00122] It will be appreciated that one or more forms of the present invention has a smaller first valve orifice that can readily open under action of the float initiating movement of the first valve member, lowering the pressure inside the main vent valve (float chamber) body, thus allowing the float to cause to open the larger second valve orifice, i.e. a 2 stage process, for effective venting at higher pressures.

[00123] A ball check valve acts as a non-return feature. This non- return arrangement has been expressly designed for reliability, is not an “add-on” to a base product and is completely external to the main body. Some non-return features are placed at the valve inlet, but this simply traps contaminants within the main valve body and can result in jamming of the float and seal system [00124] Benefits and advantages of one or more embodiments of the present invention include at least one of the following:

• Can operate effectively without a strainer • Can vent large quantities of gas at high pressure (e.g. at 2500 kPa) • Has dual orifices for venting at all pressures 20 kPa to 2500 kPa • Has modulating seals to provide soft closure (anti-slam) • Provision for vented gas to be plumbed back into gas the line (vent to atmosphere is not environmentally responsible) • Can operate up to 12 degrees off-vertical

2018101369 18 Sep 2018 [00125] A vent valve assembly embodying the present invention has also been developed to a Class 600 (10.2Mpa) version that can still provide full pressure relief functionality up to 2500 kPa, but can withstand an over-pressure system situation up to 10.2 MPa.

Claims (5)

1. THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

   1. A vent valve assembly for use in venting excess gas or gas pressure, the vent valve assembly including a first valve and a second valve providing two stage pressure release valving to vent gas pressure from a vent valve body housing a float arrangement, the vent valve assembly actuated by the float arrangement in response to sufficient gas pressure within the vent valve body and associated reduced level of liquid within the vent valve body, wherein the first valve opens under action of the float arrangement to vent an initial pressure from inside the vent valve body to atmosphere through an orifice of the first valve providing pressure release passing through the second valve without the second valve opening thereby initially reducing pressure in the valve body and enabling a first valve sealing member of the first valve to cause the second valve to open an orifice larger than the first valve orifice and further gas pressure is able to vent through orifices of the open first and second valves, and wherein the first valve sealing member has a sliding captive fit.
2. 2. The vent valve assembly of claim 1, wherein the first valve sealing member moves relative to a first valve seal of the first valve to open the first valve before the second valve opens, and the first valve and a valve seal or valve seat of the second valve move with each other when the second valve opens.
3. 3. The vent valve assembly of claim 1 or 2, being mountable substantially external to the vent valve body.
4. 4. The vent valve assembly of any one of claims 1 to 3, further including a check-valve provided to prevent return gas flow from atmosphere into the second valve and/or into the first valve of the vent valve assembly.
5. 5. The vent valve assembly of any one of claims 1 to 4, wherein the vent valve assembly is a replaceable insert or cartridge.