High reliability pressure relief valve

A pressure relief valve is disclosed with a first stage valve that is in series with a second stage valve, with an enclosed cavity between the first stage valve and the second stage valve. The first stage valve relieves pressure from an enclosure into the enclosed cavity between the stages, when the pressure is above a cracking pressure of the first stage valve. The second stage relieves pressure from the enclosed cavity when the pressure is above the cracking pressure of the second stage valve.

BACKGROUND

1. Technical Field

This disclosure relates to pressure relief valves.

2. Background Art

In the subsea industry pressure relief valves with relatively low cracking pressures are often used as a safety device to prevent the buildup of inside pressure within a subsea electronics housing. Subsea housings are hydrostatic pressure vessels designed for external pressure and are typically not capable of withstanding even modest relative internal pressure without failure.

Significant Internal pressures can develop as the result of hydraulic leaks, battery off-gassing and or slow sea water leaks that cannot relieve internal pressure quickly enough during recovery to the surface.

Unfortunately pressure relief valves have a reputation for poor reliability in the subsea environment. Corrosion and fouling of the moving parts by suspended particulate matter can sometimes lead to failure by preventing the valve from reseating sufficiently to establish a reliable seal. While the use of redundant corrosion resistant materials and seals improve reliability of subsea pressure relief valves these enhancements do not address the fundamental problem of the mechanical parts within the valve; each being single point of failure.

BRIEF SUMMARY

The embodiments of the pressure relief valves disclosed relate to pressure relief valves for relieving pressure inside a chamber, including a chamber used in the deep sea or other high pressure environments with improved reliability over existing pressure relief valve designs. In an example embodiment, the relief valve includes a first stage with a first valve having a first cracking pressure value, and a second stage with a second valve, having a second cracking pressure value. An enclosed cavity is between the first stage and the second stage, so that the first valve relieves pressure above the first cracking pressure value from an enclosed housing into the enclosed cavity, and the second stage valve relieves pressure above the second cracking pressure value from the enclosed cavity into an outside environment.

The first valve may include a first body and a first poppet, and the second valve may include a second body and a second poppet. The first body may have an opening configured to receive the second body, with the second body occupying at least a portion of the opening. At least one seal may be placed between the first body and the second body. The enclosed cavity may be formed with a sealed space between the first body and second body.

The first valve may also include a first threaded stem connected to the first poppet and a first spring configured to keep the first valve in a closed position until the first spring is compressed. A first adjustment nut may be used to adjust the load on the first spring, with the first adjustment nut positioned on the first threaded stem to set the first cracking pressure value.

The first adjustment nut may be set so that the first cracking pressure value is higher than the second cracking pressure value. Alternatively, the first cracking pressure value may be approximately the same as the second cracking pressure value. In another embodiment, the first adjustment nut may be set so that the first cracking pressure value is lower than the second cracking pressure value.

The first adjustment nut may be set so the first cracking pressure is approximately within a first range. The second valve may include a second spring configured to keep the second valve in a closed position until the second spring is compressed, and a second adjustment nut to adjust the load on the second spring. The second adjustment nut may be set so the second cracking pressure is approximately within a second range.

A cap may be placed next to the second valve to prevent particles from entering the second valve. The cap may be attached to the second body in a manner so that the cap will be removed if a high rate of fluid passes through the second valve.

A high flow indicator may be attached to the second stage. The high flow indicator may be configured to indicate when a high flow of fluid has passed through the second valve.

The first valve may include a first threaded valve stem including a first thread lock device. The first adjustment nut may be placed on the first threaded valve stem so that it is in contact with the first thread lock device to prevent the first adjustment nut from moving due to vibration.

In another example embodiment, an enclosed housing may have an exterior and an interior, where the enclosed housing is configured to protect the interior from pressurized fluids on the exterior of the enclosed housing. The enclosed housing may also include a pressure relief port that allows fluid to pass from the interior of the enclosed housing to the exterior of the enclosed housing. The enclosed housing may include a pressure relief valve having a total cracking pressure value. The pressure relief valve may be fixed in the pressure relief port that is configured to allow fluid to pass in one direction from the interior of the enclosed housing to the exterior of the enclosed housing when fluid pressure on the interior of the enclosed housing is greater than the sum of fluid pressure on the exterior of the housing and the total cracking pressure value. The pressure relief valve may include a first stage valve, and a second stage valve, and an enclosed cavity between the first stage valve and the second stage valve.

The first stage valve may have a first cracking pressure value, and the second stage valve may have a second cracking pressure value that is lower than the first cracking pressure value. The first stage valve may be configured to allow fluid to pass in one direction from the interior of the housing into the enclosed cavity. The second stage valve may be configured to allow fluid to pass in one direction from the enclosed cavity to the exterior of the housing.

The enclosed housing may be configured to withstand fluid pressure, with a maximum fluid pressure up to the design operating pressure.

An example method of producing a high reliability pressure relief valve may include the steps of: assembling a first stage with a first pressure relief valve for relieving fluid pressure from an enclosed housing above a first cracking pressure value; assembling a second stage with a second pressure relief valve to relieve pressure above a second cracking pressure value; and assembling the first stage with the second stage in series, with an enclosed cavity between the first stage and the second stage, where the first stage relieves pressure above the first cracking pressure value from the enclosed housing into the enclosed cavity, and where the second stage relieves pressure above the second cracking pressure value from the enclosed cavity into an outside environment outside the enclosed housing.

The first cracking pressure value may be a higher pressure than the second cracking pressure value.

The example method may include the steps of: adjusting the first stage to set the first cracking pressure value; and adjusting the second stage to set the second cracking pressure value.

As will be made clear, the disclosed embodiments of the pressure relief valve provide important advantages in providing a highly reliable pressure relief system for enclosed housings in a high pressure environment.

DETAILED DESCRIPTION

In one embodiment of the invention, a pressure relief valve addresses the problem of failure of moving parts by housing two serially redundant pressure relief valves in a single corrosion resistant housing. An example pressure relief valve100is shown inFIG. 1, with a first housing12, and a second housing22, and a cap27. The cap27prevents dust and particles from interfering with the operation of the pressure relief valve100. The cap27in the example embodiment has an opening that allows fluid exiting the second valve20to pass through the cap27.

In one embodiment a high flow indicator may be placed on the outside of the pressure relief valve, so that an inspection from the outside of the pressure relief valve will indicate that a high rate of flow has passed through the valve at some point. In some cases components such as electronics fail and produce a high volume of gas, or a large amount of heat that can increase the pressure inside a housing. Once the gas has exited through the relief valve, there may not be any indication that the component has failed as the relief valve will return to the closed position. For example, one cell in a multi-cell battery may fail, or one component may fail, with the system still operating. An indicator may be placed on the exterior of the pressure relief valve to indicate if high flow has occurred.

The cap27, for example, may serve as an indicator of a problem or failure. When normal amounts of pressure are relieved through the pressure relief valve100, the example cap27will not be moved or affected. In the event that there is a large amount of pressure that is relieved through the pressure relief valve100, for example if an electronic component inside a housing with the pressure relief valve100had a failure that caused a sudden large amount of pressure inside the housing, then pressure will be released quickly and the cap27may be moved, or even removed by the action of the valve opening further than in normal operation, or by the action of the fluid passing quickly through the cap27. In this way, inspection of the outside of the housing, by looking to see if the cap27has been moved or removed, may indicate whether there has been a failure of components inside the housing.

FIG. 2is a cut away view through the center of the example pressure relief valve100ofFIG. 1, showing a portion of the valve contained in the first housing12. In this example embodiment, the first housing12includes a first stage valve10, and an opening17with a threaded joint19. The first stage valve10in this embodiment includes a spring loaded valve with a first poppet11that includes a first valve seal16. The example first poppet11is connected to a first threaded stem18, and first adjustment nut13, attached to the first threaded stem18. The first threaded nut13, in this embodiment is used to adjust the load on a first spring14. The example first stage valve10will have a cracking pressure that depends on the load on the first spring14.

To maintain a consistent cracking pressure, the first adjustable nut13needs to stay in the position where it is placed after it is adjusted. A first thread lock device15is shown. By way of example, the first thread lock device15may be a nylon plug that is placed within a hole in the first threaded stem18. The nylon plug will contact the threads of the first adjustment nut13and cause a resistance to movement of the first adjustment nut13. In this way the adjustment to the first cracking pressure is likely to remain in the same place, even if the pressure relief valve is used in an environment with high levels of vibration or shock.

FIG. 2also shows in dotted lines a portion of an example housing40with a pressure relief port41. The example embodiment inFIG. 2shows the first body12of the pressure relief valve inserted into the pressure relief port41of the enclosed housing40. The enclosed housing has an exterior42and an interior43. Two seals104and105are shown which seal the pressure relief port41from the outside environment. Referring toFIG. 2, the first valve10may include a first poppet11with a first poppet seating surface31that may have a first flat portion32The first valve10may include a first body12with a first body seating surface33having a second flat portion34. The first flat portion32and the second flat portion34may be opposing. The first valve10may include a first valve seal16between the first poppet seating surface31and the first body seating surface33.

FIG. 3shows an example second stage20of the pressure relief valve ofFIG. 1. The example second stage valve20includes a second poppet21, connected to a second threaded stem28. In this example embodiment, the second stage20is similar to the first stage10shown inFIG. 2, with the same operation of a second adjustment nut23, and a second spring24. A second valve seal26is also part of the example valve shown inFIG. 3, and prevents exterior fluid from entering the valve. The example second stage valve20also includes a second thread lock device25, which may be a nylon plug and operate in the same manner as the first thread lock device15. Referring toFIG. 3, the second poppet21may include a second poppet seating surface35that may have a third flat portion36. The second body22may include a second body seating surface37having a fourth flat portion38. The third flat portion36and the fourth flat portion38may be opposing. The second valve20may include a second valve seal26between the second poppet seating surface35and the second body seating surface37.

The second body22of the example second stage valve20is designed to be inserted into the opening17of the first body12shown inFIG. 2. To ensure a proper seal to the exterior environment, multiple redundant seals,107and108are used in this example. The example second body22also includes threads29to connect with the threaded joint19of the first body12.

FIG. 4shows an example arrangement with the first body12ofFIG. 2assembled with the second body22ofFIG. 3to form a valve with two separate valve assemblies; a first stage valve10and a second stage valve20. In the example embodiment, these assemblies are screwed together at the threaded joint19. This joint is sealed by at least two and in this case three redundant o-rings107and108which seal the interior cavity between the first and second stage valves as well as protect the threaded joint from the high pressure environment, such as sea water. In this example, each valve consists of a body12and22, a poppet11and21(with locking feature15and25), a spring14and24and an adjustable nut13and23. All parts in the foregoing example which are exposed to sea water may be Titanium, coated to reduce galvanic corrosion.

With the first stage10and second stage20combined in the example ofFIG. 4, an enclosed cavity30is formed between the first valve and the second valve. This allows fluid with a differential pressure above the cracking pressure of the first valve10to pass through the first valve10into the enclosed cavity30. When fluid, moves through the first valve10into the cavity30, this will increase the pressure of fluid inside the enclosed cavity30, and then cause the pressure inside the enclosed cavity30to exceed the cracking pressure of the second valve20. Fluid will then flow through the second valve20and into the high pressure environment, or the environment outside the valve100.

FIG. 5shows an example enclosed housing40with a pressure relief port41. A pressure relief valve100is shown with a first valve10, a second valve20and an enclosed cavity30between the first valve10and the second valve20. The pressure relief valve is also shown with a high flow indicator cap27, that indicates when a high flow has occurred through the pressure relief valve100. In this example the high flow indicator cap27moves or comes off when a high flow of fluid passes through the valve. The enclosed housing40has an exterior42and an interior43. Equipment such as electronic sensors and batteries may be place inside the enclosed housing40. The enclosed housing40may be placed in a high pressure environment, such as a deep sea environment. As the enclosed housing40is placed into the high pressure environment, outside pressure220acts on the exterior of the housing. Inside pressure210is likely to be lower than the outside pressure220in this environment. The inside pressure may increase, however, due to an imperfect seal, or operation of the equipment inside the enclosed housing40. When the enclosed housing is removed from the high pressure environment, the inside pressure210may exceed the outside pressure220. A high inside pressure, relative to the outside pressure220may cause failure of the enclosed housing40, or may present a safety hazard when the enclosed housing is opened to service the electronics or replace batteries. Each housing or device will have a range of acceptable pressures for both outside the housing or device, and inside the housing or device, which will be the design operating pressure.

To prevent the safety hazard or failure of the enclosed housing40, a pressure relief valve100can be used to relieve inside pressure210well before the failure of the enclosed housing40is likely to occur. Example housings are designed to withstand outside pressures220in a high pressure environment, up to the design operating pressure of the housing.

In an example embodiment, the pressure relief valve100has a design operating pressure of 8780 PSI outside pressure (or 6000 meter depth in the ocean) and may relieve any inside pressure differential greater than 15 PSI. The cracking pressure (which may be 15 PSI max) is the sum of the first and second stage cracking pressures. The cracking pressure of each valve may be factory set by adjusting the respective adjustment nuts13and23. Both of these nuts may be locked to their respective poppets by a nylon upset nylon rod15and25. This feature protects the factory setting from the effects of shock and vibration. The poppets may be tapered as illustrated in the example drawings, so as to provide an increasing cross-section for gas flow as they continue to open. The tapered poppets decrease the pressure drop across the valves and improve flow rate capability.

An example high reliability pressure relief valve may be installed onto a subsea housing into a modified SAE J1926 port with a through hole into the interior cavity of the subsea housing. This connection may be redundantly sealed by o-rings104and105. In service, if the inside pressure differential between210and30builds up and exceeds the cracking pressure of the first stage valve10the force developed from the pressure differential across the poppet exceeds the preset spring force which normally holds the poppet closed and sealed via seal16. This causes the first stage poppet11to open and gas to pass through into the inter-valve cavity30, pressurizing it as well. If the inside pressure210continues to increase or the outside pressure220decreases due to changing depth, and the pressure differential across the second stage valve20is exceeded in the same manner as the first stage it will open (seal26) and begin venting interior gas out into the exterior environment220. The combined cracking pressure of the system is the sum of the cracking pressures of the two individual valves as they are functionally arrange in series.

As inside pressure210is relieved, the pressure differential across the second stage20will fall below its cracking pressure allowing the second stage spring24to close the valve. As long as the inside pressure210is not still increasing, the first stage valve pressure differential will then drop to a point where it will also close.

A failure of either valve to seat properly will not result in a housing failure (leaking) as both must be open to allow water to pass into the inner housing chamber.

FIG. 6shows an example method of producing a high reliability pressure relief valve60. A first stage valve may be assembled61, and independently a second stage valve may be assembled63. The first stage valve may be adjusted62and the second stage valve may be adjusted64. As shown in the flow diagram ofFIG. 6, the first stage and second stage may be assembled independently and at separate times. The first stage and second stage can then be assembled together65.

The first stage valve may have a cracking pressure that is higher than, the same as, or lower than the cracking pressure of the second stage.

In the embodiments shown and discussed, particular configurations are shown by way of example, and other configurations and devices may be used within the disclosed novel inventive concepts. For example, the shape and configuration of the first body12and the second body22are shown by way of example. In alternative embodiments, the first body and the second body may be formed together rather than as two separate parts. Similarly, the type and configuration of the valve mechanisms may be any valve mechanism that allows a set cracking pressure and is capable of allowing fluid to flow in one direction, and withstand outside pressure. The drawings also show multiple redundant seals by way of example and not limitation. The invention may be practiced with any number of redundant seals sufficient to prevent fluid from passing from the exterior of the housing42into the interior of the housing43.

In the example embodiments, springs are discussed and illustrated as coil springs, such as metal corrosion resistant material springs. Other springs may be used to provide force to keep the valve closed below the desired cracking pressure. A spring is any elastic object used to store mechanical energy.

The valve and housing discussed above may be used in a high pressure environment, such as in a deep sea environment. The fluid inside the housing may be air, or alternatively, it may be other fluids. The fluid outside the housing may be water, for example seawater, or it may be air or other fluids.

The example configuration shown inFIGS. 2-4shows an adjustment nut for adjusting the cracking pressure of the valves. In other embodiments other means may be used to set a cracking pressure, which may be adjustable, or alternatively may be set without adjustment. Further, one or both of the valves may have an adjustment available for the cracking pressure.

The examples discussed above have described relieving pressure from inside a housing as an example application of the pressure relief valve. This is not by way of limitation as the pressure relief valve100may be used in any environment where fluids are to be controlled and allowed to flow in only one direction based on pressure differentials. The valve disclosed may allow fluid into a normally high pressure system when the pressure drops below a set value, such as in a water or gas supply system, and may be used for other applications other than those where pressure is relieved. In this manner an outside, external or exterior environment is describing the environment where fluid flows after the fluid passes through the second stage of the valve, and an inside, internal, or interior environment is describing the environment from which fluid will flow into the valve when the pressure differential allows the valve to open.

While the principles of the invention have been made clear in illustrative embodiments, there will be immediately obvious to those skilled in the art many modifications of structure, arrangement, proportions, and methods, the elements, materials, and components used in the practice of the invention, and otherwise, which are particularly adapted to specific environments and operative requirements without departing from those principles. The appended claims are intended to cover and embrace any and all such modifications, within the limits only of the true spirit and scope of the invention.