Patent Application
20160097181
The present invention relates to explosion mitigation for access openings, and more particularly to a vault panel configured to release pressure during an explosion event.
Vaults generally are enclosures that may be located fully or partially below grade in or near a road, a walkway, or in a basement of a residential or commercial building. Such vaults may house electrical or other equipment that occasionally smoke or may catch fire and could cause an explosion within the vault. There are many examples of combustible gases to be found in subsurface structures that contain electrical equipment. Cable insulations are typically hydrocarbon based materials such as cross-linked polyethylene (XLPE), ethylene propylene rubber (EPR), polyethylene (PE) and polyvinyl chloride (PVC) that are flammable if they are vaporized and exist within their respective flammable limits. Transformers, voltage regulators and oil-filled switches that are often installed in vaults utilize dielectric fluids that are combustible when vaporized as a result of a damaging fault. Insulating oils employed in paper insulated lead covered (PILC) cables and in self-contained fluid-filled (SCFF) cables are combustible and can add chemical energy to an explosion event if they ignite during a failure.
Aging cables, splices, and joints that may have been overloaded in the past can emit combustible gases as insulation materials overheat and degrade. If these gases are emitted in sufficient quantities such that they reach their flammable limits, then gas explosions can occur in the presence of an ignition source. Other likely sources of combustible gases can be traced to salt or other chemicals that are applied to streets during winter months; gases present due to the public disposal of combustible materials in the streets; decaying organic material that finds its way into underground structures; and gases from leaks in pipelines.
Somewhat limited access to a vault may be by a removable vault panel. For example, one wall of the vault—generally the top wall—may have an opening for receiving a vault panel. The vault panel can be a removable panel over the access opening providing ingress/egress for the underground area. The panel may, among other things, prevent a person from falling in and can restrict entry of unauthorized persons. Such panels may be seated on a frame installed over the access opening and may be flush with an at-grade surface such as a road, walkway, or basement floor. The frame may provide an interface for the panel to seat over the opening within the vault wall. Generally, the panel is secured to the frame or surrounding structure so that the panel may be removed for access while the frame remains fixed in place.
The vault panels often weigh more than 100 pounds, partly because the weight keeps them in place when traffic passes over them, and partly because they are often made out of concrete, sometimes with steel or cast iron frames. This makes them inexpensive and strong, but heavy. Despite their substantial weight, explosions in the area underneath the panel may unseat the panel due to the sudden pressure build up from the explosion. In many cases, the explosion events may move the panel so that the access opening is left fully or partially uncovered. And, in some explosion events, the panel may become a projectile, flying up to 20 feet or more in the air. To address these potentially undesirable effects, vault panels are sometimes bolted or fastened to the frame. This configuration, however, may not fully or quickly relieve the pressure from an explosion event, thereby potentially causing structural damage to the underground area or to surrounding surface structure, such as the road or building.
In most cases where vaults are installed, the vault panels include a smaller opening within the panel that receives a manhole cover. The manhole cover may be the primary access point for the inside of the vault, with the vault panel forming a secondary access method for larger, heavier infrastructure that needs to be placed within the vault. These manhole covers are generally standard and well known; however, some manhole cover assemblies have been developed to release explosive pressure in a controlled fashion. These assemblies behave similar to a relief valve by allowing the manhole cover to rise in response to explosive pressure and to then reseat once the pressure has subsided. In this way, the manhole cover may be prevented from becoming a projectile, or from leaving the frame or access opening uncovered, in response to an explosive event.
The present invention provides a vault panel assembly that enables controlled pressure release vault panel configured to function as a relief valve in an explosion event. The vault panel can be unseated from a vault panel receiving surface in the vault wall to allow fluid such as air or explosive gas, to vent from the vault while the vault panel is prevented from becoming completely removed from the vault. The vault panel assembly may be a secondary pressure relief feature that includes a manhole cover with a frame positioned within the vault panel assembly to act as a primary pressure relief feature. Both the manhole cover and vault panel thereby allowing pressure to release from the underground area through one or both of the access opening and a vault opening.
In one embodiment, for example, the controlled pressure relief vault panel may include a vault panel inner surface, an outer surface opposing said inner surface, and a vault panel peripheral edge. At least one projection may extend from the vault panel with one end fixed to the vault panel inner surface and another end with a stop defining a length of the projection. At least a portion of the stop may extend into the vault such that, in response to increased pressure, the vault panel has a range of movement outwardly from the vault to allow the escape of fluids through the vault opening. The range of movement for the panel may be defined by characteristics of the stop. The vault panel assembly may also include an access opening to the vault which may define a cover frame, and a manhole cover also adapted to move from a seated position to an unseated position with respect to said cover frame.
In one embodiment, the stop may include at least one retainer leg and a spring associated with the projection. In an active position, the retainer leg may extend radially past the peripheral edge of the vault panel so that, in response to increased pressure inside the vault, the vault panel has a range of vertical movement outwardly from the vault to allow the escape of fluids though the vault opening with the retained leg defining a limit of the range of motion.
In a further embodiment, the spring may be a coil spring a radially surrounding a portion of the projection and positioned on the projection between the retaining leg and a bushing at or near the second or distal end of the projection.
In another embodiment, the stop may include a leaf spring with two ends. the ends of the leaf spring may extend radially past the peripheral edge of the vault panel and inside the vault such that, in response to an increase in pressure within the vault, the vault panel has a range of vertical movement outwardly from the vault to allow the escape of fluids through the vault opening with the leaf spring defining a limit of the range of movement.
In any of the foregoing embodiments, the manhole cover may move from its seated position to its unseated position to vent fluid from the vault in response to a first threshold level of pressure inside the vault. The vault panel may then form a secondary pressure release, such that it moves from a seated to an unseated position in response to a second, higher, threshold level of pressure inside the vault.
These and other objects, advantages, and features of the invention will be more fully understood and appreciated by reference to the description of the current embodiment and the drawings.
Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited to the details of operation or to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention may be implemented in various other embodiments and of being practiced or being carried out in alternative ways not expressly disclosed herein. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. Further, enumeration may be used in the description of various embodiments. Unless otherwise expressly stated, the use of enumeration should not be construed as limiting the invention to any specific order or number of components. Nor should the use of enumeration be construed as excluding from the scope of the invention any additional steps or components that might be combined with or into the enumerated steps or components.
Referring to
Referring again to
As described in more detail below, the vault panel 102 may include an access cover assembly 10, such as a controlled pressure release cover 10. The cover assembly 10 may be secured to the vault panel 102, for example, by embedding a base flange 35 of a frame 14 in the vault panel 102. The cover assembly 10 covers an access opening 15 defined within the vault panel 102. Together, the cover assembly 10 and the vault panel assembly 100 may each function as pressure relief valves in the event of excessive pressure build up in the vault 111 such as may occur during an explosion. The cover assembly 10 and the vault panel assembly 100 may provide staged relief by providing a first pressure relief response at a lower threshold of pressure increase within the vault 111 and a second pressure relief response at a higher threshold of pressure increase within the vault 111. In this way, the vault panel 102 may act as a secondary or auxiliary vent for the vault 111 during an explosion event that requires such additional venting of fluid. The lower threshold pressure increase is indicated by arrows 150 such as those in
The inner surface 104 of the vault panel 102 may be fit with retention elements 120 to limit the vertical movement of the vault panel 102 with respect to the vault wall 110 and to facilitate the return of the vault panel 102 to a seated position when the pressure inside the vault 111 approaches equalization with ambient pressures. The retention elements 120 may include a projection 122 with one end 124 embedded in the vault panel 102, or attached to the inner surface 104 of the vault panel 102. A second end 126 of the projection 122 may extend from the inner surface 104 of the vault panel 102. The second end 126 of the projection 122 may define a distal end of the projection 122. In one embodiment, a leg assembly 130 may be affixed to, or otherwise associated with, the distal end of the projection 122. The leg assembly 130 may include one or more retainer legs 132. For example, the leg assembly 130 of
Further, a spring may be associated with the projection 122 and retainer legs 132. As shown in
As shown in
Variations of the vault panel assembly may also be effective for allowing the seating and unseating of the vault panel with pressure changes inside the vault. Reference numerals in
Once again, the vault panel 202 may include an access cover assembly such as the assembly 10 described below. The cover assembly 10 may be secured to the vault panel 202, for example, by the same means described herein with respect to the vault panel assembly 100. As with vault panel assembly 100, the cover assembly 10 and the vault panel assembly 200 may provide staged relief by providing a first pressure relief response at a lower threshold of pressure increase within the vault 211 and a second pressure relief response at a higher threshold of pressure increase within the vault 211. Additionally, or alternatively, one or both of the cover 12 and the vault panel 202 may open in a single action with an increase in pressure inside the vault that would trigger the movement of both the cover 12 and the vault panel 202 at the same time.
The inner surface 204 of the vault panel 202 may be fit with retention elements 220 to limit the vertical movement of the vault panel 202 with respect to the vault wall 210 and to facilitate the return of the vault panel 202 to a seated position when the pressure inside the vault 211 approaches equalization with ambient pressures. In the embodiment shown in
As shown in
The retention elements 120, 220 shown in the FIGs include these elements arranged at or near diametrically opposite areas of the panel 102, 202. Alternatively, these elements may be spaced in different locations, and the panel assembly 100, 200 may include any number of such elements to aid retaining and reseating the panel 102, 202.
As noted, the vault panel assembly 100 may optionally include an access cover assembly (or “manhole cover assembly”) generally designated 10 positioned within the vault panel 102. In one embodiment, the cover assembly 10 generally includes an access cover 12 and frame 14 adapted to support the cover 12. The frame 14 defines an access opening within the vault panel 102. In one embodiment, the cover is a “standard” manhole cover that fits in the frame 14 to cover the access opening. In another embodiment, the cover 12 is configured to behave as a relief valve in an explosion event, opening so that fluid, such as air, explosive gas, or another gas, may vent through the cover assembly 10. The cover 12 is configured to limit its movement with respect to the frame 14 in response to increased pressure on the cover 12 and to then return to a seated position once the pressure has subsided. Referring for example to the embodiment shown in
The legs 22 and 24 may be configurable from the restraint mode to a removal mode, in which one or more of the legs 22, 24 are adapted to pivot, release, or a combination thereof, in order to clear the frame 14 and enable removal of the cover 12 from the frame 14. Further, in the removal mode, one or more legs 22, 24 may also slide partially through an opening 58 in the cover 12, allowing the one or more legs to be used as a handle for removing the cover 12 from the frame 14.
With reference to
In the illustrated embodiment, the cover 12 is generally has a round shape to match the generally annular shape of the frame 14 and peripheral wall 16. Alternatively, the cover 12 may have a different shape to cover a variety of differently sized access openings and to interfit with a variety of differently sized frames 14. The cover 12 includes a peripheral edge 52, an upper surface 54 and an underside 56. The underside 56 may include a seating surface 53 adjacent to the peripheral edge 52 that interfaces with a supporting surface of the frame 14, such as the cover receiving support 42, in a seated position.
The cover assembly 10 includes a pair of legs 22, 24. Optionally, the legs 22, 24 may be configurable between two modes: a removal mode and a restraint mode. As shown in the illustrated embodiment of
Each of the legs 22, 24 includes a foot 74, 75 respectively. The feet may be integrally cast as part of each leg during manufacture. The feet 74, 75 may extend radially outwardly toward the peripheral edge 52 of the cover 12, and each may include a frame-stop surface 77, 78 that may be configured to contact the frame 14 in order to limit displacement of the cover 12 with respect to the frame 14. The feet 74, 75 may project radially outwardly beyond the peripheral edge 52 of the cover 12 in order to be aligned underneath the frame 14. The feet 74, 75 are thus aligned vertically underneath the frame 14, at least when the cover 12 is in the restraint mode. For example, the feet 74, 75 may contact the underside of the frame supporting surface 42 limiting movement of the cover 12 in an explosion event. In one embodiment at least one of the legs 22 may include an angled guide surface 72; however, the angled guide surface of the leg 22 may be provided with a generally curved, convex shape. This shape may aid in holding the cover 12 tightly against the frame 14, particularly in the area of the second leg 24, as the cover 12 moves through an angular range of motion.
The leg 22 can be fixedly anchored to the cover 12 in the restraint mode while being slidably coupled to the cover 12 in the removal mode. This leg thus determines whether or not the cover 12 is in the restraint mode or the removal mode. The longer leg, or control leg 22 may include a projection 23, or lug, having a hole 25 capable of being fastened with an anchor bolt 27 to the cover 12 so that the control leg 22 is fixedly anchored to the cover 12. This fastens the leg 22 to the cover 12 and prevents the unwanted movement of the leg 22. However, it should be understood that the control leg 22 need not be fixedly anchored to the cover 12 in order to limit movement of the cover 12 with respect to the frame 14 in response to increased pressure. If the anchor bolt 27 or a fastener for the control leg 22 is misplaced, damaged or defective, the cover 12 and the control leg 22 may remain inherently capable of limiting movement of the cover 12. In other words, without the control leg 22 fixedly anchored to the cover 12, the cover 12 may be in the removal mode but still configured for limited movement during an explosion event. For instance, if the anchor bolt 27 is not present, the projection 23 may interface with the cover 12 to enable the cover 12 to behave as a relief valve.
The leg 22 may be inserted through a control leg anchor opening 58 defined in the cover 12 from the upper surface 54 to the underside 56. When the control leg is not secured to the cover 12 (i.e., in the removal mode) the control leg 22 may slide within this opening 58 so that the control leg 22 can be slid up and away from the frame 14, thereby enabling removal of the cover 12 from the frame 14. The leg 22 can move vertically, such that the upper end of the leg including the lug 23 extends out of the upper surface 54 of the cover 12, as well as pivotally, wherein the foot 74 moves radially inwardly so that it is no longer aligned vertically underneath the frame 14. For example, by using the projection 23 as a handle to pull the cover 12 from the frame 14, the second leg 24 may rotate about the frame 14 to a position in which the cover 12 may be free from the frame 14 so that it can be removed. The control leg 22 may include a pin 21 that prevents the control leg 22 from sliding completely through the opening 58 in the removal mode. This pin 21 may be installed during manufacture after the control leg 22 is inserted through the opening 58.
As shown in
The angular displacement of the cover 12 can be advantageous in that it limits the direction in which exiting fluids can flow. Instead of allowing fluids to escape through a 360 degree range, the angular displacement of the cover reduces the circumferential range that exiting fluids can flow. In addition, it is possible to orient the cover 12 during installation to direct any gases or flames that may exit the cover assembly 10 during an explosion event. For example, in an arrangement wherein a cover assembly 10 is installed on a sidewalk near a building, the cover 12 may be keyed, for example, by cooperating structure on the frame and cover, such that the longer leg 22 must face the building, such that when the cover 12 is displaced angularly upon the pressure under the cover reaching a threshold, escaping gases, fluids and flames will be directed toward the building rather than toward the open sidewalk.
In operation, the cover 12 may be configured between two modes: a restraint mode and a removal mode. In the restraint mode, the cover 12 may behave as a relief valve, displacing angularly in response to a pressure on the underside 56 exceeding a threshold and enabling fluid to vent through the access opening 15. The cover 12 may return to a seated position on the frame 14 after the pressure has subsided. In this way, if an explosion event occurs, damage to the cover assembly 10 and surrounding structure, such as the road or the underground area, may be prevented or mitigated. The pressure threshold resulting in displacement of the cover 12 may vary from application to application, generally depending on the weight of the cover 12, and to the extent there are other fluid paths from the underground area.
To place the cover 12 in the restraint mode, the second leg 24 may be placed within the access opening 15 and interfitted with the frame 14 such that the foot 75 extends underneath a portion of the frame 14. Next, the control leg 22 may slide within the control leg anchor opening 58 until the projection 23 of the control leg 22 contacts the upper surface 54 of the cover 12. An anchor bolt 27 may fasten the control leg 22 to the cover 12 so that the control leg 22 is stationary. It should be appreciated that fastening systems other than an anchor bolt 27 may be used to anchor the control leg 22 to the cover 12, and that the present invention is not limited to using an anchor bolt 27. Further, in one embodiment, the anchor bolt 27 or other fastener may be configured to be tamper resistant so that the cover 12 may be considered an unauthorized access deterrent. As an example, in embodiments in which the anchor bolt 27 is a bolt, the bolt may be a penta-head bolt or another bolt type capable of deterring unauthorized access.
With the cover in the restraint mode, the cover 12 may have a limited range of movement with respect to the frame 14 such that it may behave as a relief valve. The cover 12, however, may not be removed completely from the frame 14 without being reconfigured into the removal mode. For example, the feet 74, 75 may be aligned underneath the frame 14 and thus interfere with a portion of the frame 14 preventing vertical movement of the cover 12 beyond a certain point with respect to the frame 14. A portion of the peripheral wall 16 of frame 14, such as a flange, may be circular, and the feet 74, 75 may be arranged such that a circle circumscribed about the feet 74, 75 has a diameter larger than an inner diameter of the peripheral wall 16. A circle circumscribed about the angled-guide surfaces 71, 72, however, may have a diameter less than that of the peripheral wall 16.
Removal of the cover 12 may be enabled by configuring the cover into the removal mode. In this mode, any fastener holding the control leg 22 in place may be loosened or removed so that the control leg 22 may clear the frame 14. The cover may be pivoted open until the second leg 24 is capable of clearing the frame 14. With the legs 22, 24 in this configuration, the cover 12 may be removed from the frame 14 in order to access the manhole, vault, utility box, or other underground area.
In operation, the vault panel assembly 100 may be configured between two modes: an installation/removal mode and a restraint mode. In the installation/removal mode, the vault panel assembly 100 may be installed and/or removed, as desired, from the vault 111 by positioning the retention elements 120 such that its components will not interfere with the placement of the vault panel 102 on the vault opening 112 and on the vault panel receiving surface 114. Once the panel assembly 100 is seated on the vault panel receiving surface 114, the legs 132 of the retention elements 120 may be rotated such that the assembly 100 is in a restraint mode. Access to the retention elements 120 may be gained by reaching through the access opening 15 of the cover assembly 10, or by other means. The vault panel 200 is positioned into a restraint mode by attaching the retention elements 220 of the springs 234 to the vault panel after the vault panel 202 is seated in place, for example, but reaching through the access opening 15 of the cover assembly 10 to attach the leaf springs 234 with portions of the springs extending underneath the vault.
In restraint mode, the vault panel assemblies 100, 200 may function as a relief valve by moving vertically out of, or becoming unseated from, the vault panel receiving surface 114, 214 to allow the escape of fluid from the vault 111, 211 through the vault opening 112, 212. In this mode, the retention elements 120, 220 are positioned so that the retention legs 132 or ends 232 of the spring 234 extend radially into the vault 111, 211 past the peripheral edge 108, 208 of the panel 102, 202. Similarly, the cover assembly 10 may be positioned in the restraint mode described herein above for the cover assembly 10.
In response to a lower threshold pressure increase 150, 250 within the vault 111, 211, the cover 12 may function as a vent allowing the escape of fluid from the vault 111, 211 through the access opening 15 to the ambient air outside the vault. If a higher threshold pressure increase 160, 260 is initially met, both the cover 12 and the panel 102, 202 may function as vents allowing the escape of fluid from the vault 111, 211 through both the access opening 15 and the vault opening 112, 212. Alternatively, provided the lower threshold pressure increase 150, 250 has occurred and the cover assembly 10 is venting fluid from the vault 111, 211 and, subsequently, the higher threshold pressure increase 160, 260 is met, the vault panel 201, 202 may become unseated from the vault panel receiving surface 114, 214 and function as an additional, or auxiliary vent.
During the escape of fluid from inside the vault 111, 211 both the cover 12 and the vault panel 102, 202 are retained on the frame 14 and the vault, respectively. Once the pressure inside the vault 111, 211 approaches equalization with the ambient pressure both the cover 12 and the vault panel 102, 202 may be reseated on the frame 14 and vault panel receiving surface 114, 214, respectively.
Directional terms, such as “vertical,” “horizontal,” “top,” “bottom,” “upper,” “lower,” “inner,” “inwardly,” “outer” and “outwardly,” are used to assist in describing the invention based on the orientation of the embodiments shown in the illustrations. The use of directional terms should not be interpreted to limit the invention to any specific orientation(s).
The above description is that of current embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. This disclosure is presented for illustrative purposes and should not be interpreted as an exhaustive description of all embodiments of the invention or to limit the scope of the claims to the specific elements illustrated or described in connection with these embodiments. For example, and without limitation, any individual element(s) of the described invention may be replaced by alternative elements that provide substantially similar functionality or otherwise provide adequate operation. This includes, for example, presently known alternative elements, such as those that might be currently known to one skilled in the art, and alternative elements that may be developed in the future, such as those that one skilled in the art might, upon development, recognize as an alternative. Further, the disclosed embodiments include a plurality of features that are described in concert and that might cooperatively provide a collection of benefits. The present invention is not limited to only those embodiments that include all of these features or that provide all of the stated benefits, except to the extent otherwise expressly set forth in the issued claims. Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular.
