Improvements in or relating to pressure relief valves

Abstract

A pressure relief valve having an inlet port and an outlet port is disclosed for retaining pressure from an outlet until a set pressure is achieved at the inlet. The valve is disposed between the inlet and outlet ports and has a valve member movable between an open position that allows fluid flow between the ports and a closed position that prevents fluid flow. Inlet pressure acts on the valve member to increase its closing force. A movable sensing spindle is provided in fluid communication with the inlet pressure and a reference pressure, the sensing spindle having a first position and a second position. As the pressure difference between the inlet pressure and the reference pressure increases toward the set pressure, the sensing spindle moves, eventually acting on the valve member to move it away from its sealing position, thus providing an opening for fluid to flow from the inlet to the outlet.

Description

[Technical Field]

[0001] The present invention relates to a valve.

[0002] In particular, but not exclusively, the present invention relates to pressure relief valves. [Background technology]

[0003] Pressure relief valves (PRVs) are used to vent pressure from a process when the inlet pressure exceeds a desired limit. This may be for example, but not limited to, safety or to keep the process within specific operating limits.

[0004] A typical pressure relief valve uses a biased valve member to hold pressure at an inlet. When the pressure at the inlet exceeds the force holding the valve member closed, the valve member opens, releases, and relieves a port or allows the excess pressure to escape, typically through an outlet. Biasing the valve member can be conventionally achieved by a spring acting downward on the valve member, or by other means, such as a pilot actuation, mass loading, or gas loading (the backside of a piston acting on the valve member).

[0005] All of these existing systems have drawbacks. Conventional relief valves have a high valve seating force that decreases as pressure increases until the pressure overcomes the seating spring force. This means that the valve is constantly under high stress when it is stored or otherwise installed without pressure. This necessitates that the valve seat / seal system must be designed to withstand the full spring preload force. This is achieved through a large seating surface on the metal-to-metal seal, resulting in reduced seal performance as the set pressure is approached, leading to low-pressure simmers, warnings, and leaks. Alternatively, soft seals may be utilized in less demanding use cases with hard stops to maintain the high spring force and prevent excessive compression of the soft seal. However, soft seal inserts are generally not recommended in some situations, such as high-temperature steam applications. For conventional pressure relief valves with hard stops and soft seats, there is a maximum achievable compression on the soft seal (due to the hard stop). Polymeric sealing materials can undergo compression set (shape change), especially when exposed to higher temperatures, thereby reducing the seating force transmitted through the polymeric part. This can result in a decrease or fluctuation in the true opening or set pressure over time, which is undesirable because the set pressure must be controlled within tight parameters. Pressure relief valves that fail the set pressure test must be reset or removed from service for repair or replacement.

[0006] Traditional PRVs also have additional drawbacks, as larger sizes are more costly and larger nozzle diameters and pressures result in greater forces, springs, and other hardware. They have poor seat tightness and simmer pressure (the pressure at which the valve begins to leak / closes, typically about 90% of the set pressure). They also perform poorly in applications with variable or high backpressure due to a lack of pressure balancing. This negatively impacts their performance, and they can lose accuracy due to the outlet pressure, which directly affects the pressure at which the valve operates. To operate in variable backpressure environments, bellows or other balancing methods are required; these are mechanically sensitive and can have relatively low backpressure tolerances compared to pilot-operated release valves, and adding balance bellows is expensive. Alternatively, a piston seal between the process fluid volume and the atmosphere (environment) can be used to balance the spindle, eliminating this effect. The disadvantages of piston seals compared to bellows are that the guide seals and spindle seals are usually elastomers or plastics, therefore temperature and chemical compatibility with the service fluid must be considered, and they still require the same high spring force for high pressure applications, resulting in high seating loads.

[0007] Furthermore, in direct acting PRVs that use soft (or sometimes called "elastic") seating elements without hard stops, constant forces acting on the soft seating elements can shorten the life of the valve due to compressive setting of the soft material, resulting in either premature leakage or variable opening or set pressures.

[0008] Conventional valves also require large, high force springs for many use cases. For high flow capacity or high pressure use cases, large springs must be used because in conventional pressure relief valves, the pressure sensing area is equal to the nozzle diameter, thus determining the maximum possible flow rate.

[0009] The decrease in seating force as pressure increases results in low simmers (otherwise called warnings or leaks) below the set pressure, which is detrimental to the efficiency of many process systems.

[0010] Conventional PRVs can be affected by high or variable discharge pressures because this can significantly change the valve set point, making the conventional valve unusable for a particular use case, or requiring the conventional valve to have additional balancing features, which can entail additional cost and complexity.

[0011] Balanced piston PRV valves may be suitable in some use cases, but the piston seal must be the same diameter as the valve seat and of high integrity to seal the process fluid from the environment. High-leakage / emissions-compliant valve stem packings, such as high-temperature graphite or braided Teflon, especially at larger diameters, tend to have high friction and are too expensive to provide sufficiently accurate set points for criticality safety systems.

[0012] A balance bellows PRV provides an essentially frictionless seal, isolating the valve from the effects of backpressure. However, for a bellows PRV to provide the desired balancing effect, the bellows must be large enough in diameter to match the nozzle pressure area. To allow a relatively short, large-diameter, pressure-resistant bellows to displace a significant distance, the bellows must be made of multiple, very thin, fragile layers. The design tradeoffs presented by these bellows typically limit the backpressure they can handle. Generally, backpressure must be limited to 20% or 30% of the valve set pressure.

[0013] Pilot-operated pressure relief valves (PORVs or POPRVs) have limited high-temperature applications due to their sliding soft seals. They also cannot be used in sanitary clean-in-place (CIP) applications due to the complex and small-diameter piping and pilot valves. Due to the small flow path in the pilot valve and piping, PORVs may not be well suited for process media that are highly viscous or contain high levels of particulates. At smaller sizes, PORVs typically cost more than conventional valves, and they often use non-standard porting (e.g., API 526). PORVs are often perceived as complex and specialized compared to conventional valves. Their multi-stage operation can sometimes result in slower response than direct-acting valves. They require a separate pilot control valve, small-diameter piping, and a sensing valve, driving up cost and assembly complexity.

[0014] References herein to patents, other external documents, or other sources of information are generally for the purpose of providing a context for discussing features of the present invention. Unless otherwise expressly stated, the reference to such external documents shall not be construed as an admission that such documents or such sources are prior art or form part of the common general knowledge in the art in any jurisdiction.

[0015] It is an object of the present invention to provide an improved pressure relief valve, or to overcome the above-mentioned drawbacks, or to address the above-mentioned needs, or at least to provide the public with a useful choice. Summary of the Invention

[0016] In a first aspect, the present invention provides a pressure relief valve that acts on an inlet fluid under pressure to prevent and allow the inlet fluid to flow from an inlet to an outlet, comprising: a valve body having an inlet leading to an interior of the valve body and an outlet leading from the interior; a valve member operably disposed within the valve body, the valve member having a first pressure surface on a first side in fluid communication with the inlet fluid, a second pressure surface on a second side opposite the first surface in fluid communication with the inlet fluid, and a first sealing surface on the first side for sealing the inlet from the outlet; a first biasing force biasing the valve member to a first valve position whereby the valve member seals the inlet from the outlet; and a sense spindle in fluid communication with the inlet, the sense spindle having a third pressure surface in fluid communication with the inlet fluid and a second biasing force biasing the sense spindle to the first spindle position against inlet fluid pressure acting on the third pressure surface, the second biasing force being non-additive to the first biasing force; In use, inlet fluid acting on the second pressure surface adds to the first biasing force in sealing the first sealing surface to the inlet; When the inlet pressure exceeds the set pressure, the sensing spindle is moved to or towards a second spindle position which breaks the seal between the first sealing surface and the inlet, allowing the inlet fluid to exit to the outlet, where it resides in a pressure relief valve.

[0017] Preferably, when at a pressure below the set pressure, the inlet fluid acting on the second pressure surface generates a force greater than the first biasing force in sealing the first sealing surface to the inlet.

[0018] In a first aspect, the present invention provides a pressure relief valve that acts on an inlet fluid under pressure to prevent and allow the inlet fluid to flow from an inlet to an outlet, comprising: a valve body having an inlet leading to an interior of the valve body and an outlet leading from the interior; a valve bonnet removably engaged with the valve body between the first port and the second port to further define a duct therebetween; a valve member having an endless skirt within the duct, the endless skirt having an outer periphery, the valve body at least partially defining an annular chamber around the outer periphery, the endless skirt having an inner periphery defining an interior chamber, the valve member having a closed position that prevents fluid flow and an open position that allows fluid flow; an endless skirt in sliding and sealing engagement with the valve bonnet at a first sealing diameter or periphery between the open and closed positions; an outer base of the valve member that seals against the valve disc at a second sealing diameter or periphery when in the closed position; a first pressure region defined between the first sealing diameter or circumference and the second sealing diameter or circumference, the first pressure region providing a bias toward the closed position upon receiving a fluid under pressure into the interior chamber; a first sealing diameter or circumference that, when in an open position, defines an opening between the valve disc and the valve member to permit fluid flow from the first port through the opening to the second port; a sensing spindle in sliding and sealing engagement with the valve bonnet at a third sealing diameter or circumference (D3), the third sealing diameter or circumference (D3) defining a second pressure region, the second pressure region providing a bias toward an open position upon receiving fluid under pressure; In use, inlet fluid acting on the second pressure surface reduces the first biasing force in sealing the first sealing surface to the inlet, and when the inlet pressure exceeds a set pressure, the sensing spindle is moved to or towards a second spindle position which breaks the seal at the first sealing diameter and allows the inlet fluid to exit to the outlet, in a pressure relief valve.

[0019] Preferably, the valve member is biased closed by a first bias.

[0020] Preferably, the first pressure region provides a bias from a fluid under pressure in addition to the first bias; Preferably, the third sealing diameter is smaller than the second sealing diameter.

[0021] Preferably, there is a second bias acting on the sensing spindle against the inlet fluid acting on the second pressure surface.

[0022] In another aspect, the present invention provides a pressure relief valve having an inlet port and an outlet port, comprising: a valve member disposed between the inlet and outlet ports and movable between an open position permitting fluid flow between the ports and a closed position preventing fluid flow; a valve member in fluid communication with the inlet port and the outlet port; a movable sensing spindle in fluid communication with the inlet pressure and the reference pressure; the sensing spindle comprises or includes a movable sensing spindle having a first position and a second position that acts on the valve member to move the valve member away from its sealing position; A pressure relief valve resides in which the valve member in any position away from its sealing position provides a fluid connection between the inlet and the outlet.

[0023] In another aspect, the present invention provides a pressure relief valve that acts on an inlet fluid under pressure to prevent and allow the inlet fluid to flow from the inlet to an outlet, comprising: a valve body having an inlet leading to an interior of the valve body and an outlet leading from the interior; a valve member operably disposed within the valve body, the valve member having a first pressure surface on a first side in fluid communication with the inlet fluid and a second pressure surface on a second side opposite the first surface and in fluid communication with the inlet fluid, a difference between the first pressure surface and the second pressure surface defining a first pressure region across which the inlet and outlet pressures act, and a first sealing surface on the first side sealing the inlet from the outlet; a first biasing force biasing the valve member to a first valve position whereby the valve member seals the inlet from the outlet; and a sense spindle in fluid communication with the inlet, the sense spindle having a second pressure region in fluid communication with the inlet fluid, the sense spindle having a second biasing force biasing the sense spindle to the first spindle position against inlet fluid pressure acting on the second pressure region, the second biasing force being non-additive to the first biasing force; In use, a pressure differential between the inlet fluid and the outlet fluid acting on the first pressure region adds to a first biasing force in sealing the first sealing surface against the inlet; When the inlet pressure exceeds a set pressure, the sensing spindle is in a pressure relief valve where the inlet pressure acts on a second pressure area to move to or towards a second spindle position, thereby acting on the valve member to create a separation between the valve member and the sealing surface and allowing flow between the inlet and outlet.

[0024] Preferably, when the sensing spindle acts on the valve member, the sensing spindle moves the valve member into or towards the second valve position.

[0025] In another aspect, the present invention provides a pressure relief valve that acts on an inlet fluid under pressure to prevent and allow the inlet fluid to flow from the inlet to an outlet, comprising: a valve body having an inlet leading to an interior of the valve body and an outlet leading from the interior; a valve member operably disposed within the valve body, the valve member having a first pressure region across which the inlet pressure and the outlet pressure act, and a first sealing surface on a first side for sealing the inlet from the outlet; a first biasing force biasing the valve member to a first valve position whereby the valve member seals the inlet from the outlet; and a sense spindle in fluid communication with the inlet, the sense spindle having a second pressure region in fluid communication with the inlet fluid, the sense spindle having a second biasing force biasing the sense spindle to the first spindle position against inlet fluid pressure acting on the second pressure region, the second biasing force being non-additive to the first biasing force; In use, a pressure differential between the inlet fluid and the outlet fluid acting on the first pressure region adds to a first biasing force in sealing the first sealing surface against the inlet; When the inlet pressure exceeds a set pressure, the sensing spindle is in a pressure relief valve where the inlet pressure acts on a second pressure area to move to or towards a second spindle position, thereby acting on the valve member to create a separation between the valve member and the sealing surface and allowing flow between the inlet and outlet.

[0026] Preferably, the valve member has a first pressure surface on a first side thereof in fluid communication with the inlet fluid, and a second pressure surface on a second side thereof opposite the first surface and also in fluid communication with the inlet fluid, the difference between the first and second pressure surfaces defining a first pressure region.

[0027] In yet another aspect, the present invention provides a pressure relief valve that acts on an inlet fluid under pressure to prevent and allow the inlet fluid to flow from the inlet to an outlet, comprising: a valve body having an inlet leading to an interior of the valve body and an outlet leading from the interior; a valve member operably disposed within the valve body, the valve member having a first pressure region across which the inlet pressure and the outlet pressure act, and a first sealing surface on a first side of the valve member that seals against the inlet sealing surface, sealing the inlet from the outlet; a first biasing force biasing the valve member to a first valve position, thereby sealing the inlet from the outlet; and a sense spindle in fluid communication with the inlet, the sense spindle having a second pressure region in fluid communication with the inlet fluid, the sense spindle having a second biasing force biasing the sense spindle to the first spindle position against inlet fluid pressure acting on the second pressure region, the second biasing force being non-additive to the first biasing force; In use, a pressure differential between the inlet and outlet fluids acting on the first pressure region adds to a first biasing force to seal the inlet from the outlet; In use, when the inlet pressure exceeds a set pressure, the sensing spindle is moved to or towards a second spindle position through the action of the inlet pressure on the second pressure region, thereby acting on the valve member to create a separation between the first sealing surface and the inlet sealing surface, allowing fluid flow between the inlet and outlet, in a pressure relief valve.

[0028] Preferably, there is a first pressure surface on a first side of the valve member in fluid communication with the inlet fluid, and a second pressure surface opposite the first pressure surface on a second side of the valve member also in fluid communication with the inlet fluid, the net difference between the first pressure surface and the second pressure surface defining a first pressure region across which the inlet pressure and outlet pressure act.

[0029] Preferably, a pressure differential between the inlet and outlet fluids acting on the first pressure region creates a net pressure in addition to the first biasing force acting to seal the valve member.

[0030] Preferably, there is a third pressure surface on the sensing spindle which defines the second pressure area.

[0031] Preferably, the separation of the first sealing surface and the inlet sealing surface reduces the net force provided by the first pressure region, and the first sealing surface and the inlet sealing surface are further separated by a sensing spindle to allow flow between the inlet and the outlet.

[0032] Preferably, the first bias and / or the second bias are adjustable.

[0033] Preferably, the first bias is a spring or other resilient or similar bias capable of providing an initial force to hold the first sealing surface against the inlet sealing surface.

[0034] Preferably, the sensing spindle is substantially housed within the valve member.

[0035] Preferably, the area of ​​the second pressure surface is greater than the area of ​​the first pressure surface to increase the force holding the valve member in a sealed condition.

[0036] Preferably, the ratio of the area of ​​the first pressure surface to the second pressure surface is adjustable through the inlet to vary the biasing force that closes the valve member.

[0037] Preferably, there is an annular chamber around the valve member in fluid communication with the outlet.

[0038] Preferably, the second pressure area or pressure surface of the spindle is used to overcome the combined closing force of the first bias and the resultant force of the first pressure area and the inlet and outlet pressures acting thereon to move the valve member from the first valve position and unseal the valve member.

[0039] Preferably, the valve member is an annular member and the first sealing surface is adjacent the inlet.

[0040] Preferably, the first sealing surface is an annular surface.

[0041] Preferably, the inlet sealing surface is annular to mate with the first sealing surface.

[0042] Preferably, there is at least one fluid channel between the first pressure surface and the second pressure surface.

[0043] Preferably, the fluid channel is within the periphery of the first sealing surface such that there is no fluid communication to the outlet when the first sealing surface is sealed to the inlet sealing surface.

[0044] Preferably, the first biasing force is provided by a coil spring disposed about the outer surface of the valve member.

[0045] Preferably, the second biasing force is provided by a coil spring.

[0046] Preferably, there is a stop for holding the sensing spindle in the first spindle position against the second biasing force.

[0047] Preferably, the second bias is adjustable in force to partially allow adjustment of the set pressure.

[0048] Preferably, when the inlet fluid pressure increases but remains below a set pressure, the first pressure region increases the force holding the valve member in a sealing condition.

[0049] Preferably, at least one fluid channel is at the axis of the valve member and the sensing spindle passes through it towards the inlet.

[0050] Preferably, the sensing spindle and the valve member translate along the longitudinal axis from their first respective positions to their second respective positions.

[0051] Preferably, the annular member defining the valve member, the first sealing surface, and the inlet sealing surface are concentric with the longitudinal axis.

[0052] Preferably, there is an additional fluid channel between the first pressure region and the second pressure region.

[0053] Preferably, a cross section of the sensing spindle upstream from the valve member is capable of acting as a catch to engage and open the valve member as the sensing spindle moves from its first position to or towards its second position.

[0054] Preferably, the cross section is of a larger diameter than the fluid channel through which the sensing spindle passes so that the sensing spindle can engage and move the valve member.

[0055] Preferably, the stopper also acts to define an annular chamber and is sealed to its inner periphery.

[0056] Preferably, the sensing spindle and valve member are in separate sliding seal with the stopper.

[0057] Preferably, the sense spindle has a stop portion that engages the stop to hold the sense spindle in the first spindle position against the second biasing force.

[0058] Preferably, a guide skirt is on the valve member and extends to or into the inlet and is in sliding engagement with the inlet to guide the valve member as it seals and unseals.

[0059] Preferably, the guide skirt is in sliding sealing engagement with the inlet.

[0060] Preferably, the fluid channel is unsealed on a first movement of the valve member towards the second valve position, and the valve skirt or its second fluid channel is unsealed on a second further movement of the valve member towards the second valve position.

[0061] Preferably, the valve member is balanced with respect to both inlet and outlet pressure.

[0062] In another aspect, the present invention provides a method of operating a pressure relief valve that acts on an inlet fluid under pressure to prevent and allow the inlet fluid to flow from an inlet to an outlet, comprising: biasing a valve member to seal an opening from the inlet to the outlet, the valve member having a first pressure region against which inlet fluid pressure can act to increase the sealing force of the valve member against the valve seat in addition to biasing the valve member to seal the inlet from the outlet; biasing the sense spindle against an inlet fluid pressure from the inlet acting on a second pressure region of the sense spindle, the sense spindle bias not being in addition to the valve member bias, the sense spindle bias providing a set pressure at which the sense spindle will not move; Below a set pressure, the sensing spindle does not contact the valve member, the valve member bias and inlet pressure on the first pressure region hold the valve element in a sealed condition, and the sensing spindle bias holds the sensing piston against a hard stop; As the set pressure is approached, the valve member is forced more firmly against the valve seat by the action of the first pressure region, Just below the set pressure, the sensing spindle moves toward and contacts the now stationary valve member, independent of the valve member, but the inlet pressure is not sufficient to overcome the valve member bias and the first pressure field force against the valve member; Upon reaching a set pressure, the inlet fluid pressure on the second pressure region, which is greater than the first pressure region, is now high enough to overcome both the valve member bias and the sensing spindle bias, and the sensing spindle then moves the valve member, unsealing the opening and allowing fluid flow between the inlet and outlet; The method consists in providing a pressure relief valve having a low initial sealing pressure which increases with inlet fluid pressure to prevent inlet fluid from flowing to the outlet until a set pressure is reached, at which point an opening is unsealed to allow fluid flow from the inlet to the outlet.

[0063] In another aspect, the present invention provides a method of operating a pressure relief valve that acts on an inlet fluid under pressure to prevent and allow the inlet fluid to flow from an inlet to an outlet, comprising: biasing a valve member to seal an opening from the inlet to the outlet, the valve member having a first pressure region against which inlet fluid pressure can act to increase the sealing force of the valve member against the valve seat in addition to biasing the valve member to seal the inlet from the outlet; biasing the sense spindle against an inlet fluid pressure from the inlet acting on a second pressure region of the sense spindle, the sense spindle bias not being in addition to the valve member bias, the sense spindle bias providing a set pressure at which the sense spindle will not move; Below a set pressure, the sensing spindle does not contact the valve member, the valve member bias and inlet pressure on the first pressure region hold the valve element in a sealed condition, and the sensing spindle bias holds the sensing spindle against a hard stop; Upon reaching a set pressure, the inlet fluid pressure on the second pressure region, which is greater than the first pressure region, is now high enough to overcome both the valve member bias and the sensing spindle bias, and the sensing spindle then moves the valve member, unsealing the opening and allowing fluid flow between the inlet and outlet; The method consists in providing a pressure relief valve having a low initial sealing pressure which increases with inlet fluid pressure to prevent inlet fluid from flowing to the outlet until a set pressure is reached, at which point an opening is unsealed to allow fluid flow from the inlet to the outlet.

[0064] Preferably, just below the set pressure, the sensing spindle moves towards and contacts the now stationary valve member independently of the valve member, but the inlet pressure is not sufficient to overcome the valve member bias and the first pressure field force against the valve member.

[0065] Preferably, there is a first pressure surface on a first side of the valve member in fluid communication with the inlet fluid, and a second pressure surface opposite the first pressure surface on a second side of the valve member also in fluid communication with the inlet fluid, the net difference between the first pressure surface and the second pressure surface defining a first pressure region across which the inlet pressure and outlet pressure act.

[0066] Preferably, a pressure differential between the inlet and outlet fluids acting on the first pressure region creates a net pressure in addition to the first biasing force acting to seal the valve member.

[0067] Preferably, there is a third pressure surface on the sensing spindle which defines the second pressure area.

[0068] Preferably, the separation of the first sealing surface and the inlet sealing surface reduces the net force provided by the first pressure region, and the first sealing surface and the inlet sealing surface are further separated by a sensing spindle to allow flow between the inlet and the outlet.

[0069] Preferably, the first bias and / or the second bias are adjustable.

[0070] Preferably, the first bias is a spring or other resilient or similar bias capable of providing an initial force to hold the first sealing surface against the inlet sealing surface.

[0071] Preferably, the sensing spindle is substantially housed within the valve member.

[0072] Preferably, the area of ​​the second pressure surface is greater than the area of ​​the first pressure surface to increase the force holding the valve member in a sealed condition.

[0073] Preferably, the ratio of the area of ​​the first pressure surface to the second pressure surface is adjustable through the inlet to vary the biasing force that closes the valve member.

[0074] Preferably, there is an annular chamber around the valve member in fluid communication with the outlet.

[0075] Preferably, the second pressure area or pressure surface of the spindle is used to overcome the combined closing force of the first bias and the resultant force of the first pressure area and the inlet and outlet pressures acting thereon to move the valve member from the first valve position and unseal the valve member.

[0076] Preferably, the valve member is an annular member and the first sealing surface is adjacent the inlet.

[0077] Preferably, the first sealing surface is an annular surface.

[0078] Preferably, the inlet sealing surface is annular to mate with the first sealing surface.

[0079] Preferably, there is at least one fluid channel between the first pressure surface and the second pressure surface.

[0080] Preferably, the fluid channel is within the periphery of the first sealing surface such that there is no fluid communication to the outlet when the first sealing surface is sealed to the inlet sealing surface.

[0081] Preferably, the first biasing force is provided by a coil spring disposed about the outer surface of the valve member.

[0082] Preferably, the second biasing force is provided by a coil spring.

[0083] Preferably, there is a stop for holding the sensing spindle in the first spindle position against the second biasing force.

[0084] Preferably, the second bias is adjustable in force to partially allow adjustment of the set pressure.

[0085] Preferably, when the inlet fluid pressure increases but remains below a set pressure, the first pressure region increases the force holding the valve member in a sealing condition.

[0086] Preferably, at least one fluid channel is at the axis of the valve member and the sensing spindle passes through it towards the inlet.

[0087] Preferably, the sensing spindle and the valve member translate along the longitudinal axis from their first respective positions to their second respective positions.

[0088] Preferably, the annular member defining the valve member, the first sealing surface, and the inlet sealing surface are concentric with the longitudinal axis.

[0089] Alternatively, the annular member defining the valve member, the first sealing surface, and the inlet sealing surface seal on a flat surface and are therefore not concentric with the longitudinal axis.

[0090] Preferably, there is an additional fluid channel between the first pressure region and the second pressure region.

[0091] Preferably, a cross section of the sensing spindle upstream from the valve member is capable of acting as a catch to engage and open the valve member as the sensing spindle moves from its first position to or towards its second position.

[0092] Preferably, the cross section is of a larger diameter than the fluid channel through which the sensing spindle passes so that the sensing spindle can engage and move the valve member.

[0093] Preferably, the stopper also acts to define an annular chamber and is sealed to its inner periphery.

[0094] Preferably, the sensing spindle and valve member are in separate sliding seal with the stopper.

[0095] Preferably, the sense spindle has a stop portion that engages the stop to hold the sense spindle in the first spindle position against the second biasing force.

[0096] Preferably, a guide skirt is on the valve member and extends to or into the inlet and is in sliding engagement with the inlet to guide the valve member as it seals and unseals.

[0097] Preferably, the guide skirt is in sliding sealing engagement with the inlet.

[0098] Preferably, the fluid channel is unsealed on a first movement of the valve member towards the second valve position, and the valve skirt or its second fluid channel is unsealed on a second further movement of the valve member towards the second valve position.

[0099] Preferably, the valve member is balanced with respect to both inlet and outlet pressure.

[0100] In another aspect, the present invention provides a method of operating a pressure relief valve that acts on an inlet fluid under pressure to prevent and allow the inlet fluid to flow from an inlet to an outlet, comprising: providing a valve disc having an inlet leading to an interior of the valve disc and an outlet leading from the interior; providing a valve bonnet removably engaged with the valve body between the first port and the second port to further define a duct therebetween; providing a valve member in the duct having an endless skirt, the endless skirt having an outer periphery, the valve body at least partially defining an annular chamber around the outer periphery, the endless skirt having an inner periphery defining an interior chamber, the valve member having a closed position that prevents fluid flow and an open position that allows fluid flow; an endless skirt in sliding and sealing engagement with the valve bonnet at a first sealing diameter or periphery between the open and closed positions; providing an outer base of the valve member that seals against the valve disc at a second sealing diameter or perimeter when in the closed position; a first pressure region defined between the first sealing diameter or circumference and the second sealing diameter or circumference, the first pressure region providing a bias toward the closed position upon receiving a fluid under pressure into the interior chamber; When in the open position, an opening is defined between the valve disc and the valve member, allowing fluid flow from the first port through the opening to the second port. providing a sensing spindle in sliding and sealing engagement with the valve bonnet at a third sealing diameter or circumference (D3), the third sealing diameter or circumference (D3) defining a second pressure region, the second pressure region providing a bias towards an open position upon receiving fluid under pressure; In use, inlet fluid acting on the second pressure surface reduces the first biasing force in sealing the first sealing surface to the inlet, and when the inlet pressure exceeds a set pressure, the sensing spindle is moved to or towards a second spindle position which breaks the seal at the first sealing diameter and allows the inlet fluid to exit to the outlet, in a pressure relief valve.

[0101] In another aspect, the present invention provides a method of operating a pressure relief valve having an inlet port and an outlet port, comprising: providing a valve member disposed between the inlet and outlet ports and movable between an open position permitting fluid flow between the ports and a closed position preventing fluid flow; a valve member in fluid communication with the inlet port and the outlet port; and a movable sensing spindle in fluid communication with the inlet pressure and a reference pressure; enabling a sensing spindle to move between a first position and a second position, towards which the sensing spindle acts on the valve member to move the valve member away from its sealing position; The method resides in a manner in which the valve member, in any position away from its sealing position, provides a fluid connection between the inlet and the outlet.

[0102] In another aspect, the invention consists in a pressure relief valve as herein described with reference to any one or more of the accompanying drawings.

[0103] In another aspect, the invention resides in a method of operating a pressure relief valve, as herein described with reference to any one or more of the accompanying drawings.

[0104] As used herein, the term "and / or" means "and" or "or," or both.

[0105] As used herein, "(s)" following a noun refers to the plural and / or singular form of the noun.

[0106] As used herein, the term "comprises" means "consisting at least in part of." When interpreting references herein that include that term, the features preceding that term in each reference must all be present, although other features may also be present. Related terms such as "comprise" and "comprised" should be interpreted similarly.

[0107] Reference to a numerical range disclosed herein (e.g., 1 to 10) is also intended to encompass reference to all rational numbers within that range (e.g., 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10) and to any range of rational numbers within that range (e.g., 2 to 8, 1.5 to 5.5, and 3.1 to 4.7).

[0108] The entire disclosures of all applications, patents and publications, cited above and below, if any, are hereby incorporated by reference.

[0109] The present invention can also be broadly said to consist of the parts, elements and features, and any and all combinations of any two or more of the parts, elements or features, individually or collectively referred to or shown in the specification of this patent application, and where a particular integer having a known equivalent in the art to which the invention pertains is described herein, such known equivalent is deemed to be incorporated herein as if individually set forth.

[0110] Other aspects of the present invention will become apparent from the following detailed description, given by way of example only and with reference to the accompanying drawings. [Brief explanation of the drawings]

[0111] A preferred form of the present invention will now be described with reference to the accompanying drawings. [Figure 1] 1 shows a side isometric view of a pressure relief valve according to the present invention. [Figure 2] 2 shows a front isometric view of the pressure relief valve of FIG. 1, showing a portion of the interior through the valve outlet. [Figure 3] 2 illustrates a bottom isometric view of the pressure relief valve of FIG. 1, showing a portion of the interior through the valve inlet. [Figure 4] 2 shows a side vertical cross section of the valve of FIG. 1. [Figure 5] 5 shows an enlarged view of the upper region of the cross section of FIG. 4. [Figure 6] 5 shows an enlarged view of the lower region of the cross section of FIG. 4. [Figure 7] 2 is an exploded view of the sachet of FIG. 1. FIG. 3 is an exploded isometric view of the valve of FIG. [Figure 8] 8 shows an enlarged view of the upper region of the exploded view of FIG. 7. [Figure 9] 8 shows an enlarged view of the lower region of the exploded view of FIG. 7. [Figure 10] 1 shows a schematic diagram of the internal components and operation of a valve according to the present invention. [Figure 11] 1 is a graph of pressure versus sensed piston displacement of the present invention compared to two prior art pressure relief valves. [Figure 12] 1 is a graph of pressure versus valve seating force for the present invention compared to two prior art pressure relief valves. [Figure 13] 1 shows the inside of the lower valve with the valve disc removed before the set release pressure is reached. [Figure 14] The diagram of FIG. 13 shows the valve beginning to open by reaching the set pressure. [Figure 15] The diagram in Figure 13 shows the valve fully or nearly fully open, releasing pressure once the set release pressure is reached. [Figure 16] 1 shows a cross-sectional schematic view of a pressure relief valve. [Figure 17] 1 shows a further cross section with a bellows seal. [Figure 18] 3 shows a further variant of the invention in vertical section along the main axis. [Figure 19]10 shows a vertical cross section of a further variation of the invention, utilising a flat sealing interface between the valve member and the valve body and a contained first bias for the valve member, with the valve in a closed position. [Figure 20] 19 is a view similar to FIG. 19 showing the forces resulting from inlet fluid pressure acting on the sensing spindle and valve member when the valve is still closed. [Figure 21] 19 shows a view similar to FIG. 19 with the sensing spindle moving upward and contacting the valve member. [Figure 22] 22 shows a view similar to FIG. 21 with the feed spindle engaging the valve member and the inlet pressure rising to the point where the valve member opens and fluid pressure is released from the inlet to the outlet. DETAILED DESCRIPTION OF THE INVENTION

[0112] A preferred embodiment will now be described with reference to Figures 1 to 18.

[0113] A first variant of the pressure relief valve 1 is shown in Figures 1-9, and its operating principle is illustrated in Figures 10-15. The valve 1, shown schematically in Figure 1, has a valve body 4, an inlet 2 to an interior 5 of the valve body 4, and an outlet 3 from the interior 5. Connected to the valve body 4 is a bonnet 39. The bonnet 39 can be attached to the valve body 4 in any number of ways, and in the variant shown here, a bonnet fastener 40 in the form of a threaded bolt passes through the bonnet 39 and into a threaded portion in the valve body 4, holding the two together. The interior of the valve bonnet 39 houses the second bias 17 for the sensing spindle 15, which will be described in more detail below.

[0114] On top of the bonnet 39 is a bonnet cap 41, shown in FIGS. 4, 5, 7, and 8. The bonnet cap 41 can be attached in any desired manner, from press-fit, bayonet, threaded, or otherwise. Optionally, although not ideal, the bonnet cap 41 is not present, which may allow corrosion and contamination of components that would otherwise be covered. For adjustable bias 17, the bonnet cap covers a second bias adjuster 42, the form of which depends on the selected bias. In the illustrated variation, bias 17 is a coil spring that acts in compression against the sensing spindle 15. The adjuster 42 in this case is a threaded rod that engages a nut or similar threaded component in the bonnet 39 or bonnet cap 41. Optionally, there may be a lock nut (not shown) to prevent the adjuster from being changed by vibration or otherwise. The adjuster 42 advances or retracts the bias 17, thus increasing or decreasing the force that the spring 17 applies to the sense spindle 15, and therefore adjusting the set point (described further below). Other methods of adjusting the spring bias can also be used, such as a rotating crown with different step heights. The bias may take any one of several other forms that can be applied to generate increased or decreased force on the sense spindle, such as, but not limited to, a passive compression or tension spring, a gas or air driven spring, or an electromechanical system.

[0115] An enlarged view of the valve body interior 5 is shown in Figure 6, and exploded views are shown in Figures 7 and 9. Interior 5 houses valve member 7, sensing spindle 15, and first bias 13. Valve member 7 is annular or circular about longitudinal axis 31, as shown, and sensing spindle 15 also lies on that axis 31, both of which slide independently along that axis. Valve member 7 and sensing spindle 15 are radially symmetric, so that when pressure is applied they are essentially laterally balanced and remain parallel in their movement.

[0116] The valve member 7 is biased by a first bias 13 to its first valve position 14, shown in FIG. 6. This creates an initial seal 21 (shown in FIG. 16) of the inlet 2 from a (preferably annular) chamber 28, which opens to the outlet 3. The first sealing surface 12 of the valve member 7, shown in FIG. 10, seals 21 against the inlet sealing surface 25. In this example, the first sealing surface 12 is present. In the variation shown in FIGS. 13-15, there is an inlet insert 43 that retains the inlet sealing surface 25. In this variation, the inlet insert 43 is threaded and sealed to the valve body 4, although any suitable retention and sealing method can be used, such as, but not limited to, an interference fit, adhesive, etc.

[0117] The valve member 7 has one or more fluid channels 30 from the first pressure surface 8 on the first side 9 to the second pressure surface 11 on the second side 11, as shown in Figures 10 and 16. These allow the inlet pressure to act on both the first and second sides of the valve member 7, and together with the inlet and outlet fluid pressures form a net first pressure region that acts to increase the force on the seal 21 as the inlet pressure increases.

[0118] The first pressure area 23 is determined by the net area of ​​the sensing spindle 15 facing the fluid pressure in the inlet 2, as shown in Figures 10, 13, and 19, and is defined by a diameter or circumference D3. The second pressure area 22 is the net difference between the area of ​​the first pressure surface 8 on the first side 9, as defined by a diameter or circumference D2 in Figures 10 and 19, and the area of ​​the second pressure surface 10 on the second side 11 of the valve member 7, as defined by a diameter or circumference D1 in Figures 10 and 19, where the diameter or circumference D1 is greater than the diameter or circumference D2. Because the second pressure surface 10 is greater than the first pressure surface 8, a net closing force 47 exists on the valve member 7 when the valve member is closed, and this net closing force in Figure 13 pushes the valve member 7 downward in the direction of the arrow shown.

[0119] The valve member 7 is in sliding sealing engagement within the valve 1 such that the only path to the outlet 3, even from the second side 11, as the valve member moves from the first valve position 14 (e.g., as shown in Figures 10 and 13) to or towards the second valve position 24 (e.g., as shown in Figure 14), is through the opening that the valve member 7 forms between the first sealing surface 12 and the inlet sealing surface 25. In the variation shown in Figure 6, there is a stopper 29 which thus acts to form a sliding seal with the valve member 7 and which holds or guides the first bias 13 between itself and the valve member 7. The stopper 29 in this variation is held in place by a relief in the valve body 4 and the upper valve bonnet 39.

[0120] The stopper 29 also acts as a stopper for the second bias 17 acting on the sensing spindle 15 via the second bias 17 acting through a stopper portion 34 that is engaged between the stopper 29 and the second bias 17 and moves with the second bias 17 and the sensing spindle 15, as seen in Figure 6. The sensing spindle 15 provides a second pressure area 23 for the pressure of the inlet fluid.

[0121] As can be seen from the above explanation, the first biasing force 13 and the second biasing force 17 are independent and do not interact with each other.

[0122] The sensing spindle 15 is biased by a second bias 17 to be held in its first spindle position 18 and is guided to remain parallel to the axis 31 by passing through the center of a stopper 29, as shown in Figure 6. Through one of the fluid openings 30 in the variants of Figures 1 to 17, the fluid of the sensing spindle 15 passes, as shown at least in Figures 6 and 10.

[0123] The sensing spindle 15, as described above, can engage with the valve member 7 to move the valve member 7 and open it. The sensing spindle 15 has a shoulder 48 (which in this embodiment is behind the second pressure area 23). In this embodiment, it is the shoulder 48 that engages with the valve member 7 to move it open.

[0124] The sensing spindle 15 can move from its first spindle position 18 (shown in FIG. 6 ) to or towards a second spindle position 20 (shown in FIG. 15 ). In a preferred variation, the sensing spindle 15 engages the valve member 7 partway through this movement. This is achieved by having a cross section 32 that is wider than the central fluid channel 30 of the valve member 7 through which it passes, as can be seen in FIGS. 6 and 15 . The sensing spindle can engage the valve member in any other way that contacts and moves the valve member 7 as a result of the sensing spindle moving towards the second spindle position 20, thus moving the valve member 7 towards the second valve position 24 and its fully open state.

[0125] Movement of the sensing spindle and valve member does not move the stopper 29 .

[0126] When pressure relief valve 1 is not in use, on a shelf in storage, or connected but not subjected to a net higher inlet pressure, only first bias 13 is in operation, resulting in a very low sealing force. This conserves sealing material because the seal or sealing interface (e.g., valve first sealing face 12 of a valve with inlet sealing face 25) is not under a very low static load. The seal load only increases proportionally to the net difference between the inlet and outlet fluid pressures.

[0127] The valve member 7 or sensing spindle 15 must preferably be guided in its movement and may be guided in its movement on the valve bonnet 39, nozzle, or sensing spindle, respectively, on their inner or outer surfaces. The shape of the guide features may be such that the flow capacity of the valve is throttled or otherwise increased through the valve position.

[0128] As an example of this, the valve member 7 may have an extension in the form of a skirt (not shown) that extends from the lower outer periphery of the first pressure face 8 (see FIG. 10 ) down into the inlet 2 and engages the inner periphery of the inlet / seal throughout its range of movement from the first valve position 14 to the second valve position 24. The skirt, if present, can provide lateral stability to and guide the valve member 7. An opening through the skirt still allows fluid flow from the inlet to the outlet when moved from the first valve position 14. Such a skirt can assist with throttle release velocity on initial opening.

[0129] Fluid channels 30 may also exist diagonally through the valve member 7 from the second pressure surface 10 to the first pressure surface 8, angled toward the outlet to allow for an initial release of inlet fluid pressure from behind the valve member upon initial displacement from the first valve position 14, such as when the valve member is in a simmer state, i.e., simply releasing fluid pressure. In one form, these fluid passages may seal against the inlet sealing surface 25. These fluid passages may be the first path for releasing inlet fluid pressure during the initial movement of the valve member from the first valve position to move deeper toward the second valve position 24.

[0130] Figure 17 shows a variation of the valve 1 which uses a bellows or rolling seal 44 between the valve member 7 and the valve disc.

[0131] For example, in a preferred variation of the present invention shown in FIG. 19, the stopper 29, sensing spindle 15, valve member 7, spring 13, and inlet insert 43 can all be removed as a subassembly or cartridge by removing the valve bonnet 39. This allows for serviceability, allowing a new bonnet subassembly to be installed within the valve body 4, leaving the valve body 4 in place. Thus, maintenance of a failed valve or valve can be easily accomplished by removing the existing subassembly and inserting a new one. The existing subassembly can then be repaired as needed. The removable cartridge or subassembly incorporates all replaceable and serviceable components. The cartridge or subassembly incorporates all soft seals and moving components that can be removed as a unit, dramatically improving serviceability compared to the prior art.

[0132] A further variation incorporating the same operations and features of the present invention is shown in Figures 19-22. In this variation, the first bias 13 is protected from the fluid as it passes from the inlet when the valve member 7 opens by the overlap of the stopper 29 and the valve member 7 which largely or completely encloses the bias 13. The opening of the valve member 7 may be a very sudden and violent pressure event and release, which protects them from corrosion, corrosive properties, or particles therein. This is beneficial as the valve member and spring 13 are no longer exposed to high velocity turbulent flow, meeting the requirements set forth in ASME VIII.

[0133] This further variation has a flat face sealing surface. The flat, e.g., polished, surface of the nozzle or inlet insert 43 and the sealing surface 25 between the nozzle or inlet insert 43 and the valve member 7 provide sufficient sealing surface area to allow tolerances (especially concentricity requirements) to be relaxed. An additional advantage of this variation is that the pressure field, and therefore the performance of the valve, is not dependent on where the face seal contacts on the inlet insert 43; misalignment due to tolerances does not affect pressure actuation. Even if the diameter or perimeter of the face seal, the piston permanent seal, and the sensing spindle seal are misaligned relative to one another, this does not affect the performance of the pressure actuation system and the valve. It is the dimensional / geometric tolerances of their diameters or perimeters that have a direct effect, i.e., the pressure field as defined above.

[0134] The pressure relief valve 1 of the present invention can be described by a pressure area defined by a perimeter or diameter (or other dimension if a non-circular configuration is used). In this manner, the pressure relief valve operates to prevent fluid flow from an inlet (or first port) 2 to an outlet (or second port) 3 until the pressure differential between the inlet 2 and outlet 3 reaches a set point. As shown in Figures 4, 10, 13, and 19, among others, the inlet 2 of the valve disc leads to the interior of the valve disc, and the outlet 3 exits from the interior. For example, there is a valve bonnet 39 that is removably engaged to the valve disc using fasteners 40 in Figure 4, although a threaded interface may also be used, as in Figure 18. The valve disc and bonnet 40 define a duct or chamber 28, which in the illustrated embodiment is annular or toroidal (i.e., donut-shaped) therebetween. The valve member 7 has an endless valve skirt 49 (as shown in Figure 10) or wall within the duct or chamber 28. The endless skirt 49 has an outer periphery, which is circular in the illustrated example but can be any shape, and the valve disc 4 at least partially defines the annular chamber 28. The endless skirt 49 has an inner periphery that defines an internal chamber 50. The valve member 7 has a closed position that prevents fluid flow and an open position that allows fluid flow, and the valve member is biased closed by a first bias 13. In the open and closed positions, and between the open and closed positions, the endless skirt 49 is in sliding and sealing engagement with the valve bonnet at a first sealing diameter or periphery D1 (shown in FIG. 10 as the inner diameter or periphery of the chamber 50; in other examples, the sealing can be on the outer diameter or periphery of the valve skirt 49). This defines the second pressure surface 10. When in the closed position, the valve member 7 has a sealing surface 25 that seals against the valve disc 4 at a second sealing diameter or periphery D2, as shown in FIG. 10. This area within the perimeter of the sealing diameter (if circular) or perimeter defines first pressure surface 8. First sealing diameter (or perimeter) or second pressure surface 10 is larger than second sealing diameter (or perimeter) or first pressure surface 8, the net difference defining first pressure area 22.The first pressure region 22, upon receiving fluid under pressure into the internal chamber, preferably provides a bias toward the closed position in addition to the first bias 13. When the valve member 7 is in the open position, an opening is defined between the valve body 4 and the valve member 7 to allow fluid flow from the first port through the opening to the second port, with fluid 51 escaping through the opening 27, as shown, for example, in FIG. 15 . The central or feed spindle 15 is in sliding and sealing engagement with the valve bonnet 39, or a portion thereof, at a third sealing diameter or circumference (D3) that is smaller than the second sealing diameter or circumference (D2). The third sealing diameter or circumference (D3) defines a second pressure region 23, which, upon receiving fluid 51 under pressure, provides a bias toward the open position. Thus, in use, the valve 1 has inlet fluid 51 acting against the second pressure surface 23, acting against the second bias 17. When the inlet pressure exceeds the set pressure, the sensing spindle 15 is moved to or towards the second spindle position, acting against or reducing the first biasing force 47 and breaking the seal at the first sealing diameter or circumference 25, allowing the inlet fluid to exit to the outlet.

[0135] The way in which the pressure relief valve operates will now be described with reference to Figures 13 to 15.

[0136] First pressure region 22 receives fluid under pressure from at least inlet 2, or is subject to a higher net pressure when inlet 2 is compared to outlet 3. The higher net inlet and outlet pressures act to increase the sealing or net closing force 47 of valve member 7 against inlet sealing surface 25, as described with respect to first pressure region 22. Thus, as the net pressure differential (between inlet and outlet) increases, the force sealing valve member 7 against inlet sealing surface 25 closes while the inlet pressure is below a set pressure. The position of valve 1 when the pressure differential between the inlet and outlet is below a set pressure is shown in Figure 13.

[0137] The initial sealing force of the valve member (called a metered valve in the graphs of Figures 11 and 12) as a percentage of the maximum sealing force (reached when the set pressure is reached) is shown as the top blue line (1) in the graph of Figure 12. The starting point (y-intercept) and slope (1) of the line can be varied as needed depending on the strength of the first bias 13 and first pressure field 22.

[0138] The set pressure is the pressure at which the valve opens, allowing pressure to be released from the inlet to the outlet, and is determined by the second pressure area 23 of the sensing spindle 15 and the second bias 17. Increasing the force provided by the second bias 17 (e.g., by switching to a spring with a higher spring constant or by winding more force when using the regulator 42) or decreasing the second pressure area 23 increases the set pressure.

[0139] As the inlet pressure increases, the force 47 sealing the valve 7 increases, and the force acting on the sensing spindle 15 also increases as a force equal to the pressure multiplied by the area. The movement of the sensing spindle 15 (called the sensing piston in FIG. 11) as the pressure (in bar) increases is shown in FIG. 11. In the region (1) before the set pressure (here 98 bar), the sensing spindle does not move and is in the position shown in FIG. 13. At or near the set pressure (approximately 98 bar in the illustrated graph) (2), the sensing spindle moves from its first spindle position 18, passes through an intermediate position (3) (shown in FIG. 14), and then proceeds to its second spindle position 20 (shown in FIG. 15) (4).

[0140] This movement of the sensing spindle 15 from its initial first spindle position 18 to the intermediate position is shown in Figure 14, where it can be seen that the stop portion 34 has been lifted away from the stop 29 and the sensing spindle 15 has moved upwards to contact the valve member 7. This can be seen in Figure 11, where the position of the valve member 7 has moved to the solid black line representing the 0 point (-0.2 indicates the first spindle position 18 and 0.0 indicates the intermediate position when the sensing spindle 15 contacts the valve member 7).

[0141] As the inlet pressure continues to increase, the force that the sensing spindle 15 exerts on the valve member 7 increases. However, the feed spindle cannot move any further until it overcomes the first bias 13 acting on the valve member 7. Thus, the graph in Figure 11 shows that the sensing spindle does not move at point (3) even as the inlet pressure continues to increase.

[0142] The pressure acting on the feed spindle 15 then reaches a set pressure (approximately 98 bar) that is able to overcome the combined applied forces of the first bias 13 and the second bias 17. At this point, the sensing spindle 17 and the valve member 7 are able to move as a unit towards their respective spindle second position 20 and valve second position 24 as shown in Figure 14, the valve 1 is unseated and opens (moving along graph portion (4) in Figures 12 and 11), and pressure is released from the inlet 2 to the outlet 3.

[0143] When the inlet pressure drops below the set pressure, the movement reverses and valve 1 closes.

[0144] In the variation shown in FIG. 18, the inlet 2 enters from the side and the outlet 3 is at the bottom. Inlet fluid pressure is prevented from moving through the valve to the outlet 3 by an annular valve member 7 having a first sealing surface 12 that forms a seal 21 on an inlet sealing surface 25 that is part of a central, stationary valve mandrel 46. The seal may be formed by a soft seal, a hard seal, or a combination. In the illustrated example, a soft inlet seal 25 is shown, and the valve member first sealing surface 12 is a hard sealing surface. The soft inlet seal 25 is biased to seal by the inlet pressure, and its sealing pressure increases proportionally with the inlet pressure.

[0145] The first pressure region 22 on the valve 7 is again acted upon by the net pressure differential between the inlet and outlet fluids to drive the valve 7 into a sealing position in the first valve position 14, with the sealing force 47 again increasing with increasing inlet to outlet pressure differential. The valve member 7 is connected to a central valve spindle 45 by at least one radial vane (not shown). The valve spindle 45 is biased to seal in the first valve position 14 by a first bias 13, as shown in FIG. 18. The valve member 7 has an outer diameter or periphery seal 36 that is slidably sealed to the inner diameter or periphery of the valve body 4. If desired, an actuator can act on the valve spindle 45 to manually open the valve.

[0146] An annular chamber 100 between the sense spindle 15 and the valve body has a net differential pressure area between its upper and lower seals. The sense spindle 15 is in sliding engagement with the valve body and can carry the valve spindle 45 and valve 7. The annular chamber 100 receives increasing inlet pressure via the fluid channel 30, which acts on the net differential pressure area within the annular chamber 100, acting against the second bias 17. At a set pressure, the inlet fluid within the annular chamber 100 overcomes the second bias 17, and the sense spindle moves from the first spindle position 18, as shown, in a direction toward the outlet 3 to a second spindle position (not shown). Moving from the first spindle position 18 contacts and opens the valve member 7, allowing fluid within the inlet 2 to flow to the outlet 3 and relieve pressure.

[0147] As the pressure increases, the following occurs: Low pressure below the set pressure The sense spindle 15 is not in contact with the valve member 7 and the first bias 13 and inlet pressure hold the valve member 7 closed. The second bias 17 holds the sense piston against its hard stop.

[0148] Not close to set point, medium pressure No change pressure is high enough to move anything, but the valve member 7 is held more firmly in the valve seat by the action of the first pressure field formation and the increasing closing force 47 .

[0149] Nearly set pressure The sensing spindle 15 moves (independently) towards and contacts the (stationary) valve member 7 , but the inlet pressure is not sufficient to overcome the first bias 13 and pressure 47 on the valve member 7 .

[0150] Set pressure reached The sensing spindle pressure area (second pressure area) is larger than the valve member pressure area (first pressure area) and is high enough to overcome both the first bias 13 and the second bias 17 (spring), causing the sensing spindle 15 to contact the valve member 7, lifting it and opening the valve 1.

[0151] Thus, the present invention has the pressure sensing task performed by a sensing spindle 15, which is a separately movable element from the element (valve member 7), the position of which defines whether the valve is open or closed. The sensing piston (sensing stem / spindle 15) moves independently of the flow control element (valve 7).

[0152] The diameter or circumference of the sensing piston 7 (second pressure area 23) is independent of the piston sealing diameter or circumference (first pressure area 22), which means that a much smaller pressure sensing area can be used to control the equivalent flow area, significantly reducing the spring force (and therefore valve size and material cost) requirements for a given flow capacity requirement.

[0153] The substantially cylindrical piston has one cylindrical sealing surface that engages the valve bonnet and one annular sealing surface that engages a valve seat, which may be part of the body or part of the nozzle assembly.

[0154] The sensing stem 15 is assembled through the bonnet and through the valve piston 7. In the "closed" position, the sensing piston is in a lowered position and is not in contact with or pressing against the valve piston 7, at least when viewed in the orientation of FIG. 13. The valve piston 7 is held in the closed position by the seating spring 13 and also by the pressure generated by the inlet pressure acting on the second pressure area 22 (generated by the difference between the diameter or circumference between the cylindrical sealing faces of the piston and the effective sealing diameter or circumference between the valve seat and seal).

[0155] As the set pressure is approached, the valve piston 7 is forced into the valve seat with a strong (high pressure) sealing force 47 which is proportional to the inlet pressure, ensuring a tight seal between the parts and preventing flow / leakage.

[0156] When the set pressure is achieved, the sensing stem 15 moves (upwards in Figure 14, downwards in Figure 18) and contacts the valve piston 7, pushing it upwards (Figure 14) or downwards (Figure 18), compressing the valve piston seating spring and opening the valve.

[0157] Moving the valve piston connects the inlet and outlet chambers, opening the valve and "bleeding" the inlet to the outlet.

[0158] The effective sealing diameter or circumference of the piston (on both the face seal and the cylindrical sliding seal) is substantially the same, which means that the pressure in the discharge chamber of the valve has little effect on the performance and / or behavior of the valve.

[0159] The new pressure relief valve design operates similarly to a conventional direct acting valve in that the pressure field is acted upon by inlet pressure against a force reference spring, with one key difference being that the pressure sensing work is performed by a sensing spindle 15 which is a movable element separate from the valve element 7, the position of which defines whether the valve is open or closed (valve piston).

[0160] The sensing piston (sensing stem) 15 moves independently of the flow control element 7 (piston).

[0161] The sensing piston diameter or circumference is independent of the piston sealing diameter or circumference, which means that a much smaller pressure sensing area can be used to control an equivalent flow area, significantly reducing the spring force (and therefore valve size and material cost) requirements for a given flow capacity requirement.

[0162] The two seals on the valve piston (the permanent seal [sometimes called the piston seal] and the face seal) are closely matched in diameter or circumference, providing a small residual pressure area that acts to hold the valve closed as the inlet pressure increases relative to the outlet pressure.

[0163] The piston has its own seating spring / bias that provides the initial seating force to create a seal between the piston and the nozzle. As pressure increases, most of the valve piston seating force comes from the pressure rather than from a spring or other biasing force.

[0164] The increase in pressure acts to hold the piston against its valve seat (nozzle) until the sensing piston begins to act on the piston, lifting it and opening the valve.

[0165] The layout is geometrically very similar to conventional valves, and therefore compatibility and interchangeability with typical conventional pressure relief valves is high. Conventional pressure relief valves can be converted to use the present invention.

[0166] The conceptual design of the pressure sensitive overpressure relief valve is described in its closed state and in its open state. Important aspects of the design to note are: -The "metered valve" element is balanced with respect to both inlet and discharge pressures The sensing path is completely contained within the valve, eliminating the need for external sensing hardware (such as prior art pilot valves) -Valve construction is suitable for in-line service with trim assembled to one side of the valve -The valve body is easily adapted to solenoid actuators or any other type of actuator without significant trim changes and uses a simple adapter to switch actuation methods

[0167] A new style of pressure relief valve that is similar in size to existing types of valves but offers advantages over both. Compare with conventional PRV Improved seat tightness and simmer performance over traditional pressure relief valves without the added cost and complexity of a PO PRV (pilot operated pressure relief valve) Balanced discharge pressure without the use of fragile and expensive multi-layer metal bellows Cost advantages due to lower force and spring requirements compared to conventional PRVs with large pressures Reduces seating force, significantly reducing the load on the soft valve seat and preventing set pressure fluctuations

[0168] Pilot-operated PRV Achieve similar performance within a much more "familiar" and simpler system that is much more similar to a conventional PRV Significant cost benefits for all but the largest PO PRVs · Because there is no sensing tube, the valve has the ability to be used with viscous or dirty fluids or in applications requiring CIP, opening up a much wider set of use cases

[0169] The present invention is inherently well balanced, substantially reducing the need for actuator force; the reference force spring or actuator does not act on the sealing element until the valve is actuated, meaning that the sealing element is isolated from high seating loads when not required; and has the advantage that a perfectly balanced valve can be achieved simply and inexpensively by adding or removing specific seals from the metered valve itself, without the need for special components.

[0170] Valves in accordance with the present invention can utilize much smaller, lower cost, lower force, and therefore safer springs. The flow capacity (seat diameter or circumference), pressure, and spring force are no longer scaled the same, resulting in the ability to significantly reduce the required spring force while maintaining the same flow capacity.

[0171] The present invention includes seals to achieve the same balancing performance as other types of balanced direct-acting valves, but the sealed bellows stem seal (shown in Figure 17) can be a much smaller diameter or circumference than an equivalent conventional bellows seal and is therefore less expensive, and the use of a sliding piston seal does not present a fugitive emission risk. Rolling diaphragm piston seals are also an attractive sealing option in this layout due to their very low friction.

[0172] The minimum seating force is defined by the preload of the seating spring 13 (which also prevents the valve element from rattling / moving and being damaged during shipping or handling). As inlet pressure increases, the piston is forced against its seat with increasing force 47, thus maintaining high seal integrity. Only when the sensing stem 15 is displaced by inlet pressure against its force reference spring 17 to the extent that the sensing piston contacts the valve piston does the force balance on the piston open or close the valve.

[0173] No additional piping, valves or assemblies are required and the valve of the present invention can simply be placed in place of an existing valve and the set pressure adjusted (if not already adjusted).

[0174] The foregoing description of the invention includes preferred forms thereof. Modifications can be made thereto without departing from the scope of the invention.

Claims

1. 1. A pressure relief valve that operates by acting on an inlet fluid under pressure to prevent and allow said inlet fluid to flow from an inlet to an outlet, comprising: a valve body having the inlet leading to an interior of the valve body and the outlet leading from the interior; b) a valve member operably disposed within the valve body, the valve member having a first pressure surface on a first side in fluid communication with the inlet fluid, a second pressure surface on a second side opposite the first surface in fluid communication with the inlet fluid, and a first sealing surface on the first side for sealing the inlet from the outlet; c. a first biasing force biasing the valve member to a first valve position whereby the valve member seals the inlet from the outlet; d. a sense spindle in fluid communication with the inlet, the sense spindle having a third pressure surface in fluid communication with the inlet fluid, the second biasing force being non-additive to the first biasing force, urging the sense spindle to a first spindle position against the inlet fluid pressure acting on the third pressure surface; e. in use, inlet fluid acting on the second pressure surface adds to the first biasing force in sealing the first sealing surface against the inlet; f. A pressure relief valve where when the inlet pressure exceeds a set pressure, the sensing spindle moves to or towards a second spindle position which breaks the seal between the first sealing surface and the inlet, allowing the inlet fluid to exit to the outlet.

2. 2. The valve of claim 1, wherein the inlet fluid acting on the second pressure surface when at a pressure below a set pressure creates a force greater than the first biasing force in sealing the first sealing surface to the inlet.

3. 1. A pressure relief valve that operates to act on an inlet fluid under pressure to prevent and allow said inlet fluid to flow from an inlet to an outlet, comprising: a valve body having the inlet leading to an interior of the valve body and the outlet leading from the interior; a valve bonnet removably engaged with the valve body between the first port and the second port to further define a duct therebetween; a valve member having an endless skirt within the duct, the endless skirt having an outer periphery, the valve disc at least partially defining an annular chamber around the outer periphery, the endless skirt having an inner periphery defining an interior chamber, the valve member having a closed position preventing fluid flow and an open position allowing fluid flow; an endless skirt in sliding and sealing engagement with the valve bonnet at a first sealing diameter or perimeter between the open position and the closed position; an outer base of the valve member, the outer base sealing against the valve disc at a second sealing diameter or periphery when in the closed position; the first sealing diameter or circumference is greater than the second sealing diameter or circumference, a first pressure region is defined between the first sealing diameter or circumference and the second sealing diameter or circumference, the first pressure region providing a bias toward the closed position upon receiving a fluid under pressure into the internal chamber; the first sealing diameter or circumference, when in the open position, defining an opening between the valve disc and the valve member to permit fluid flow from the first port through the opening to the second port; a sensing spindle in sliding and sealing engagement with said valve bonnet at a third sealing diameter or circumference (D3), said third sealing diameter or circumference (D3) defining a second pressure region, said second pressure region providing a bias towards said open position upon receiving fluid under pressure; In use, inlet fluid acting on the second pressure surface reduces the first biasing force in sealing the first sealing surface to the inlet, and when the inlet pressure exceeds a set pressure, the sensing spindle is moved to or towards a second spindle position that breaks the seal at the first sealing diameter and allows the inlet fluid to exit to the outlet, a pressure relief valve.

4. 4. The valve of claim 3, wherein the valve member is biased closed by a first bias, the first pressure area provides a bias from fluid under pressure in addition to the first bias, the third sealing diameter is smaller than the second sealing diameter, and there is a second bias acting on the sensing spindle against the inlet fluid acting on the second pressure surface.

5. 1. A pressure relief valve that operates by acting on an inlet fluid under pressure to prevent and allow said inlet fluid to flow from an inlet to an outlet, comprising: a valve body having the inlet leading to an interior of the valve body and the outlet leading from the interior; a valve member operably disposed within the valve body, the valve member having a first pressure surface on a first side in fluid communication with the inlet fluid, and a second pressure surface on a second side opposite the first surface in fluid communication with the inlet fluid, the difference between the first pressure surface and the second pressure surface defining a first pressure region across which the inlet and outlet pressures act, and a first sealing surface on the first side sealing the inlet from the outlet; c. a first biasing force biasing the valve member to a first valve position whereby the valve member seals the inlet from the outlet; d. A sense spindle in fluid communication with the inlet, the sense spindle having a second pressure region in fluid communication with the inlet fluid, the second biasing force being non-additive to the first biasing force, urging the sense spindle to a first spindle position against the inlet fluid pressure acting on the second pressure region; e. in use, a pressure differential between the inlet fluid and the outlet fluid acting on the first pressure region adds to a first biasing force in sealing the first sealing surface against the inlet; f. A pressure relief valve wherein when the inlet pressure exceeds a set pressure, the sensing spindle is moved to or towards a second spindle position via action of the inlet pressure on a second pressure region, thereby acting on the valve member to create a separation between the valve member and a sealing surface and allowing flow between the inlet and outlet.

6. 6. A pressure relief valve as claimed in any one of claims 1 to 5, wherein the sensing spindle acts on the valve member, the sensing spindle moving the valve member towards a second valve position.

7. 1. A pressure relief valve that operates to act on an inlet fluid under pressure to prevent and allow said inlet fluid to flow from an inlet to an outlet, comprising: a valve body having the inlet leading to an interior of the valve body and the outlet leading from the interior; a valve member operably disposed within the valve body, the valve member having a first pressure region between which the inlet pressure and the outlet pressure act and a first sealing surface on the first side for sealing the inlet from the outlet; c. a first biasing force biasing the valve member to a first valve position whereby the valve member seals the inlet from the outlet; d. A sense spindle in fluid communication with the inlet, the sense spindle having a second pressure region in fluid communication with the inlet fluid, the second biasing force being non-additive to the first biasing force, urging the sense spindle to a first spindle position against the inlet fluid pressure acting on the second pressure region; e. in use, a pressure differential between the inlet fluid and the outlet fluid acting on the first pressure region adds to a first biasing force in sealing the first sealing surface against the inlet; f. A pressure relief valve wherein when the inlet pressure exceeds a set pressure, the sensing spindle is moved to or towards a second spindle position via action of the inlet pressure on a second pressure region, thereby acting on the valve member to create a separation between the valve member and a sealing surface and allowing flow between the inlet and outlet.

8. 8. A pressure relief valve as claimed in any one of claims 1 to 7, wherein the valve member has a first pressure surface on a first side in fluid communication with the inlet fluid and a second pressure surface on a second side opposite the first surface and in fluid communication with the inlet fluid, the difference between the first pressure surface and the second pressure surface defining the first pressure region.

9. 1. A pressure relief valve that operates by acting on an inlet fluid under pressure to prevent and allow said inlet fluid to flow from an inlet to an outlet, comprising: a valve body having the inlet leading to an interior of the valve body and the outlet leading from the interior; b) a valve member operably disposed within the valve body, the valve member having a first pressure region between which the inlet pressure and the outlet pressure act, and a first sealing surface on a first side thereof for sealing against an inlet sealing surface to seal the inlet from the outlet; c. a first biasing force biasing the valve member to a first valve position, whereby the first biasing force can seal the inlet from the outlet; d. A sense spindle in fluid communication with the inlet, the sense spindle having a second pressure region in fluid communication with the inlet fluid, the second biasing force being non-additive to the first biasing force, urging the sense spindle to a first spindle position against the inlet fluid pressure acting on the second pressure region; e. in use, a pressure differential between the inlet and outlet fluids acting on the first pressure region adds to a first biasing force to seal the inlet from the outlet; f. A pressure relief valve wherein, in use, when the inlet pressure exceeds a set pressure, the sensing spindle is moved to or towards a second spindle position through action of the inlet pressure on the second pressure region, thereby acting on the valve member to create a separation between the first sealing surface and the inlet sealing surface to allow fluid flow between the inlet and outlet.

10. 10. A pressure relief valve as claimed in any one of claims 1 to 9, wherein there is a first pressure face on a first side of the valve member in fluid communication with the inlet fluid, and a second pressure face on a second side of the valve member opposite the first pressure face in fluid communication with the inlet fluid, the net difference between the first pressure face and the second pressure face defining the first pressure region across which the inlet pressure and outlet pressure act.

11. 11. A pressure relief valve as claimed in any one of claims 1 to 10, wherein a pressure differential between the inlet fluid and the outlet fluid acting on the first pressure region creates a net pressure in addition to the first biasing force acting to seal the valve member.

12. 12. A pressure relief valve as claimed in any preceding claim, wherein a third pressure surface defining the second pressure area is present on the sensing spindle.

13. 13. A pressure relief valve as claimed in any one of claims 1 to 12, wherein separation of the first sealing surface and the inlet sealing surface reduces the net force provided by the first pressure area, and wherein the first sealing surface and the inlet sealing surface are further separated by the sensing spindle to allow flow between the inlet and the outlet.

14. 14. A pressure relief valve according to any one of claims 1 to 13, wherein the first bias and / or the second bias are adjustable.

15. 15. A pressure relief valve as claimed in any one of claims 1 to 14, wherein the first bias is a spring or other resilient or similar bias capable of providing an initial force to hold the first sealing surface against the inlet sealing surface.

16. A pressure relief valve as claimed in any preceding claim, wherein the sensing spindle is substantially contained within the valve member.

17. 17. A pressure relief valve as claimed in any preceding claim, wherein the area of ​​the second pressure surface is greater than the area of ​​the first pressure surface to increase the force holding the valve member in a sealed condition.

18. 18. A pressure relief valve as claimed in any one of claims 1 to 17, wherein the ratio of the area of ​​the first pressure surface to the second pressure surface can be adjusted through the inlet to vary the biasing force that closes the valve member.

19. 19. A pressure relief valve according to any preceding claim, wherein there is an annular chamber around the valve member in fluid communication with the outlet.

20. 20. A pressure relief valve as claimed in any one of claims 1 to 19, wherein the second pressure area or pressure face of the spindle is used to overcome the combined closing force of the first biasing force and the resultant force of the first pressure area and the inlet and outlet pressures acting thereon to move the valve member from the first valve position and unseal the valve member.

21. 21. A pressure relief valve according to any preceding claim, wherein the valve member is an annular member and the first sealing surface is adjacent the inlet.

22. 22. A pressure relief valve according to any preceding claim, wherein the first sealing surface is an annular surface.

23. 23. A pressure relief valve according to any preceding claim, wherein the inlet sealing surface is annular to mate with the first sealing surface.

24. 24. A pressure relief valve according to any one of claims 1 to 23, wherein there is at least one fluid channel between the first pressure surface and the second pressure surface.

25. 25. A pressure relief valve as claimed in any one of claims 1 to 24, wherein the fluid channel is within the periphery of the first sealing surface such that there is no fluid communication to the outlet when the first sealing surface is sealed against the inlet sealing surface.

26. 26. A pressure relief valve according to any preceding claim, wherein the first biasing force is provided by a coil spring disposed about an outer surface of the valve member.

27. 27. A pressure relief valve according to any one of claims 1 to 26, wherein the second biasing force is provided by a coil spring.

28. 28. A pressure relief valve as claimed in any one of claims 1 to 27, wherein there is a stop to hold the sensing spindle in the first spindle position against the second biasing force.

29. 29. A pressure relief valve as claimed in any one of claims 1 to 28, wherein the second bias is adjustable in force to partially allow adjustment of the set pressure.

30. 30. A pressure relief valve as claimed in any one of claims 1 to 29, wherein the first pressure region increases the force holding the valve member in a sealing condition when the inlet fluid pressure increases but remains below a set pressure.

31. 31. A pressure relief valve according to any preceding claim, wherein the at least one fluid channel is at the axis of the valve member, and the sensing spindle passes through the channel towards the inlet.

32. 32. A pressure relief valve as claimed in any preceding claim, wherein the sensing spindle and valve member translate from their first respective positions to their second respective positions along the longitudinal axis.

33. 33. A pressure relief valve according to any one of claims 1 to 32, wherein the annular member, the first sealing surface, and the inlet sealing surface defining the valve member are concentric with the longitudinal axis.

34. 34. A pressure relief valve according to any one of claims 1 to 33, wherein there is an additional fluid channel between the first pressure region and the second pressure region.

35. 35. A pressure relief valve as claimed in any one of claims 1 to 34, wherein a cross section of the sensing spindle upstream from the valve member is capable of acting as a catch to engage and open the valve member when the sensing spindle moves from its first position to or towards its second position.

36. 36. A pressure relief valve as claimed in claim 1, wherein the cross section has a diameter or circumference greater than the fluid channel through which the sensing spindle passes so that the sensing spindle can engage and move the valve member.

37. 37. A pressure relief valve as claimed in any preceding claim, wherein the stopper also acts to define the annular chamber and is sealed to its inner periphery.

38. 38. A pressure relief valve as claimed in any preceding claim, wherein the sensing spindle and the valve member are in separate sliding seal with the stopper.

39. 39. A pressure relief valve as claimed in any one of claims 1 to 38, wherein the sensing spindle has a stop portion that engages the stop to hold the sensing spindle in the first spindle position against the second biasing force.

40. 40. A pressure relief valve as claimed in any preceding claim, wherein a guide skirt is provided on the valve member extending to or into the inlet for sliding engagement with the inlet to guide the valve member as it seals and unseals.

41. 41. A pressure relief valve according to any preceding claim, wherein the guide skirt is in sliding sealing engagement with the inlet.

42. 42. A pressure relief valve as claimed in any one of claims 1 to 41, wherein the fluid channel is unsealed on a first movement of the valve member towards the second valve position, and the valve skirt or its second fluid channel is unsealed on a second further movement of the valve member towards the second valve position.

43. 43. A pressure relief valve according to any preceding claim, wherein the valve member is balanced with respect to both inlet and outlet pressure.

44. 1. A method of operating a pressure relief valve that acts on an inlet fluid under pressure to prevent and allow said inlet fluid to flow from an inlet to an outlet, comprising: biasing a valve member to seal an opening from the inlet to the outlet, the valve member having a first pressure region against which the inlet fluid pressure can act to increase the sealing force of the valve member against a valve seat in addition to biasing the valve member to seal the inlet from the outlet; b. biasing a sense spindle against an inlet fluid pressure from the inlet acting on a second pressure region of the sense spindle, the biasing of the sense spindle not adding to the biasing of the valve member, the biasing of the sense spindle providing a set pressure at which the sense spindle will not move; c. below a set pressure, the sense spindle does not contact the valve member, the valve member bias and inlet pressure on the first pressure region hold the valve element sealed, and the sense spindle bias holds the sense piston against a hard stop; d. As the set pressure is approached, the valve member is forced more firmly against the valve seat by the action of the first pressure field; e. Just below the set pressure, the sensing spindle moves toward and contacts the now stationary valve member, independent of the valve member, but the inlet pressure is not sufficient to overcome the valve member bias and the first pressure field force against the valve member; f. Once the set pressure is reached, the inlet fluid pressure on the second pressure zone, which is greater than the first pressure zone, is now high enough to overcome both the valve member bias and the sensing spindle bias, which then moves the valve member to unseal the opening and allow fluid flow between the inlet and outlet; g. A method wherein a pressure relief valve is provided having a low initial sealing pressure that increases with inlet fluid pressure to prevent inlet fluid from flowing to the outlet until a set pressure is reached, at which point the opening is unsealed to allow fluid flow from the inlet to the outlet.

45. 1. A method of operating a pressure relief valve that acts on an inlet fluid under pressure to prevent and allow said inlet fluid to flow from an inlet to an outlet, comprising: biasing a valve member to seal an opening from the inlet to the outlet, the valve member having a first pressure region against which the inlet fluid pressure can act to increase the sealing force of the valve member against a valve seat in addition to biasing the valve member to seal the inlet from the outlet; b. biasing a sense spindle against an inlet fluid pressure from the inlet acting on a second pressure region of the sense spindle, the biasing of the sense spindle not adding to the biasing of the valve member, the biasing of the sense spindle providing a set pressure at which the sense spindle will not move; c. below a set pressure, the sensing spindle does not contact the valve member, the valve member bias and inlet pressure on the first pressure region hold the valve element sealed, and the sensing spindle bias holds the sensing spindle against a hard stop; d. upon reaching the set pressure, the inlet fluid pressure on the second pressure zone, which is greater than the first pressure zone, is now high enough to overcome both the valve member bias and the sensing spindle bias, the sensing spindle then moving the valve member to unseal the opening and allow fluid flow between the inlet and outlet; e. A method wherein a pressure relief valve is provided having a low initial sealing pressure that increases with inlet fluid pressure to prevent inlet fluid from flowing to the outlet until a set pressure is reached, at which point an opening is unsealed to allow fluid flow from the inlet to the outlet.

46. 46. ​​The method of claim 44 or 45, wherein just below the set pressure, the sensing spindle moves towards and contacts the now stationary valve member independently of the valve member, but the inlet pressure is not sufficient to overcome the valve member bias and the first pressure field force on the valve member.

47. 47. The method of any one of claims 42 to 46, wherein there is a first pressure surface on a first side of the valve member in fluid communication with the inlet fluid, and a second pressure surface on a second side of the valve member opposite the first pressure surface and in fluid communication with the inlet fluid, the net difference between the first pressure surface and the second pressure surface defining the first pressure region across which the inlet and outlet pressures act.

48. 48. The method of any one of claims 42 to 47, wherein a pressure differential between the inlet fluid and the outlet fluid acting on the first pressure region creates a net pressure in addition to the first biasing force acting to seal the valve member.

49. 49. A method according to any one of claims 42 to 48, wherein a third pressure surface is present on the sensing spindle defining the second pressure area.

50. 50. The method of any one of claims 42 to 49, wherein the separation of the first sealing surface and the inlet sealing surface reduces the net force provided by the first pressure area, and wherein the first sealing surface and the inlet sealing surface are further separated by the sensing spindle to allow flow between the inlet and the outlet.

51. 51. The method of any one of claims 42 to 50, wherein the first bias and / or the second bias are adjustable.

52. 52. The method of any one of claims 42 to 51, wherein the first bias is a spring or other resilient or similar bias capable of providing an initial force to hold the first sealing surface against the inlet sealing surface.

53. 53. A method according to any one of claims 42 to 52, wherein the sensing spindle is substantially contained within the valve member.

54. 54. A method according to any one of claims 42 to 53, wherein the area of ​​the second pressure surface is greater than the area of ​​the first pressure surface to increase the force holding the valve member in a sealed condition.

55. 55. The method of any one of claims 42 to 54, wherein the ratio of the area of ​​the first pressure surface to the second pressure surface can be adjusted through the inlet to vary the biasing force that closes the valve member.

56. 56. The method of any one of claims 42 to 55, wherein there is an annular chamber surrounding the valve member in fluid communication with the outlet.

57. 57. A method according to any one of claims 42 to 56, wherein the second pressure area or pressure surface of the spindle is used to overcome the closing force of the first bias in combination with the resultant force of the first pressure area and the inlet and outlet pressures acting thereon to move the valve member from the first valve position and unseal the valve member.

58. 58. The method of any one of claims 42 to 57, wherein the valve member is an annular member and the first sealing surface is adjacent the inlet.

59. 59. The method of any one of claims 42 to 58, wherein the first sealing surface is an annular surface.

60. 60. The method of any one of claims 42 to 59, wherein the inlet sealing surface is annular to mate with the first sealing surface.

61. 61. The method of any one of claims 42 to 60, wherein there is at least one fluid channel between the first pressure surface and the second pressure surface.

62. 62. The method of any one of claims 42 to 61, wherein the fluid channel is within the periphery of the first sealing surface such that there is no fluid communication to the outlet when the first sealing surface is sealed to the inlet sealing surface.

63. 63. The method of any one of claims 42 to 62, wherein the first biasing force is provided by a coil spring disposed about an outer surface of the valve member.

64. 64. The method of any one of claims 42 to 63, wherein the second biasing force is provided by a coil spring.

65. 65. A method according to any one of claims 42 to 64, wherein a stop is present to hold the sensing spindle in the first spindle position against the second biasing force.

66. 66. The method of any one of claims 42 to 65, wherein the second bias is adjustable in force to partially allow adjustment of the set pressure.

67. 67. A method according to any one of claims 42 to 66, wherein the first pressure region increases the force holding the valve member in a sealing condition when the inlet fluid pressure increases but remains below a set pressure.

68. 68. A method according to any one of claims 42 to 67, wherein the at least one fluid channel is at the axis of the valve member and the sensing spindle passes through the channel towards the inlet.

69. 69. A method according to any one of claims 42 to 68, wherein the sensing spindle and the valve member are translated from their first respective positions to their second respective positions along a longitudinal axis.

70. 70. The method of any one of claims 42 to 69, wherein the annular member, the first sealing surface, and the inlet sealing surface defining the valve member are concentric with the longitudinal axis.

71. 71. The method of any one of claims 42 to 70, wherein an additional fluid channel is present between the first pressure region and the second pressure region.

72. 72. A method according to any one of claims 42 to 71, wherein a cross section of the sensing spindle upstream from the valve member is capable of acting as a catch to engage and open the valve member as the sensing spindle moves from its first position to or towards its second position.

73. 73. A method according to any one of claims 42 to 72, wherein the cross section is of a larger diameter or circumference than the fluid channel through which the sensing spindle passes to enable the sensing spindle to engage and move the valve member.

74. 74. A method according to any one of claims 42 to 73, wherein the stopper also acts to define the annular chamber and is sealed to the inner periphery of the annular chamber.

75. 75. A method according to any one of claims 42 to 74, wherein the sensing spindle and the valve member are in separate sliding seal with the stopper.

76. 76. A method according to any one of claims 42 to 75, wherein the sensing spindle has a stop portion that engages with the stop to hold the sensing spindle in the first spindle position against the second biasing force.

77. 77. A method according to any one of claims 42 to 76, wherein a guide skirt is provided on the valve member, extending to or into the inlet and slidingly engaging the inlet to guide the valve member as it seals and unseals.

78. 78. A method according to any one of claims 42 to 77, wherein the guide skirt is in sliding sealing engagement with the inlet.

79. 79. The method of any one of claims 42 to 78, wherein the fluid channel is unsealed on a first movement of the valve member toward the second valve position, and the valve skirt or its second fluid channel is unsealed on a second further movement of the valve member toward the second valve position.

80. 80. A method according to any one of claims 42 to 79, wherein the valve member is balanced with respect to both inlet and outlet pressure.

81. A pressure relief valve having an inlet port and an outlet port, a valve member disposed between the inlet port and the outlet port, the valve member being movable between an open position permitting fluid flow between the ports and a closed position preventing fluid flow; a valve member in fluid communication with the inlet port and the outlet port; a movable sensing spindle in fluid communication with the inlet pressure and the reference pressure; the sensing spindle comprises or includes a movable sensing spindle having a first position and a second position that acts on the valve member to move the valve member away from its sealing position; A pressure relief valve in which a valve member in any position away from its sealing position provides a fluid connection between an inlet and an outlet.

82. 10. A pressure relief valve substantially as herein described with reference to any one or more of the accompanying drawings.

83. 10. A method of operating a pressure relief valve substantially as described herein with reference to any one or more of the accompanying drawings.

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