Removable Tank Portal Cover

This application claims the benefit of: U.S. Provisional Application No. 63/652,191, filed on May 28, 2024.

This invention pertains generally to tank portal covers, such as thief hatches. More specifically, the invention is directed to technology to temporarily seal a tank portal to prevent inadvertent escape of tank contents (e.g., liquid or gaseous hydrocarbons) during repair or maintenance of the hatch while simultaneously regulating tank pressure during the procedure.

In the oil and gas industry, tanks are routinely used to transport or store hydrocarbon fluids for later access. Access to the contents of the tank is typically through a portal in the tank that is sealed with a removable cover. A thief hatch comprises a cover that includes one or more pressure activated valves that serve to regulate the tank pressure. If the internal pressure of the tank becomes too high, a valve may activate to release some of the contents of the tank. If the internal pressure of the tank becomes too low, a valve may activate to allow ingress of atmospheric fluids into the tank. If the internal pressure of the tank is within an acceptable range, the cover seals the tank portal to reduce inadvertent release of the tank contents.

Tank portal covers often fail and need to be repaired, especially those with pressure-regulating valves. When servicing a thief hatch, the cover is often removed leaving the portal open and allowing tank contents, such as hydrocarbon gas, to escape from the tank. This has environmental, financial, and health consequences.

Accordingly, there is a need for technology that temporarily seals a tank portal while the regular cover is removed for repair/maintenance. Ideally, this temporary cover is readily removable and serves the purposes of the original cover during the repair/maintenance process.

In an aspect of the invention, a hatch cover includes a valve assembly comprising an exhaust valve subassembly and a suction valve subassembly. The exhaust valve subassembly includes a spring (or springs), a plate, and a spring loader. The suction valve assembly also includes a spring (or springs), a plate, and a spring loader. In an aspect of the invention, the exhaust-valve plate and the suction-valve plate nest together providing a surface interface that forms a seal. One or both plates also have surface interface with the housing of the cover to form a seal. The surface interfaces (plate-to-plate and plate-to-housing) form a tank seal. In a preferred embodiment: The suction plate is or has a disc with a first surface around the edge of the disc, the exhaust plate is or has a ring with a second surface around the inner edge of the ring and a third surface around the outer edge of the ring, and the housing forms or has a ring that has a fourth surface around the inner edge of the ring. The first and second surfaces may interface to provide a seal between the suction and exhaust plates. The third and fourth surfaces may interface to provide a seal between the exhaust plate and housing.

In use, the exhaust plate is interposed between the tank interior and the tank exterior and is pushed toward the tank by the exhaust-valve spring. The exhaust-valve spring loader is anchored to the tank (e.g., through the engagement of hatch cover with the hatch base), and the spring is positioned between the plate and the spring loader so as to provide a pushing force between the plate and spring loader. The spring/spring loader combination pushes the plate toward the interior of the tank. The force on the exhaust-valve plate by the exhaust-valve spring acts to seal the tank but will open if the tank pressure exceeds a certain point. This point may be set by the choice of spring(s) and by the compressional bias provided to the spring. In an aspect of the invention, the valve assembly provides a threaded joint between the spring loader and cover housing so that all exhaust springs may be biased together by a single spring loader. In a preferred embodiment, multiple exhaust springs are uniformly disposed over the surface of the exhaust plate to force the interfaces between the exhaust plate and housing and the exhaust plate and suction plate. The springs may be compressed by moving a spring-loader plate toward the exhaust plate through a threaded sliding joint between the spring-loader plate and the cover housing.

In use, the suction plate is interposed between the tank interior and the tank exterior and is pulled away from the tank by the suction-valve spring. The suction-valve spring loader is anchored to the tank (e.g., through the engagement of hatch cover with the hatch base), and the spring is positioned relative to the plate and spring loader so as to provide a pulling force between the plate and spring loader. The spring/spring loader combination pulls the plate away from the interior of the tank. The force on the suction-valve plate by the suction-valve spring acts to seal the tank but will open if the tank pressure drops below a certain point. This point may be set by the choice of spring(s) and by the compressional bias provided to the spring. In a preferred embodiment, multiple suction-valve springs are uniformly disposed over the surface of the suction-valve plate to force the interface between the suction-valve plate and exhaust-valve plate. The spring loader is anchored to the housing and the springs are disposed on a guide rod. The guide rod is positioned through a channel in the spring loader, and is connected at one end to the suction-valve plate and has a spring-retaining head at the other end. The springs are positioned between the spring-retaining head and the spring loader. The spring-retaining head is threaded into the guide rod. Thus, the springs may be individually compressed by threading the spring-retaining heads into the guide rods.

In an aspect of the invention, a hatch cover includes a lock assembly comprising a radially projecting bolt (or bolts) configured to engage the hatch base, a cam assembly configured to move the bolt in the radial direction, and a load spring (or springs) configured to provide a biasing force pushing the bolts radially out. In an aspect of the invention, the bolt is connected to the cam assembly via a sliding joint. In one embodiment, the bolt includes a T-shaped feature to engage a T-shaped slot on a cam chassis. This cam chassis (a track ring) is ring shaped and the slot forms a track running circumferentially around the ring. A bolt engaged with the track may slide circumferentially along the track, within the constraints of the track. The track varies in radial depth, such that at a first position along the track an engaged bolt will radially project out from the cover housing and at a second position along the track an engaged bolt will radially retract into the cover housing. In a preferred embodiment, a component forming a portion of the cover housing (a channel ring) includes a radial channel for each bolt and is slidably engaged with a track ring such that the track ring may rotate circumferentially relative to the channel ring such that rotating the track ring relative to the channel ring causes the bolts to move radially. A spring (or springs) connect the track ring to the housing to provide a circumferential bias on the track ring forcing the bolts toward the radially-projected position. In use, this biasing force enables the bolts to engage the hatch base to hold the cover in place.

In the summary above, and in the description below, reference is made to particular features of the invention in the context of exemplary embodiments of the invention. The features are described in the context of the exemplary embodiments to facilitate understanding. But the invention is not limited to the exemplary embodiments. And the features are not limited to the embodiments by which they are described. The invention provides a number of inventive features which can be combined in many ways, and the invention can be embodied in a wide variety of contexts. Unless expressly set forth as an essential feature of the invention, a feature of a particular embodiment should not be read into the claims unless expressly recited in a claim.

Except as explicitly defined otherwise, the words and phrases used herein, including terms used in the claims, carry the same meaning they carry to one of ordinary skill in the art as ordinarily used in the art.

Because one of ordinary skill in the art may best understand the structure of the invention by the function of various structural features of the invention, certain structural features may be explained or claimed with reference to the function of a feature. Unless used in the context of describing or claiming a particular inventive function (e.g., a process), reference to the function of a structural feature refers to the capability of the structural feature, not to an instance of use of the invention.

Except for claims that include language introducing a function with “means for” or “step for,” the claims are not recited in so-called means-plus-function or step-plus-function format governed by 35 U.S.C. § 112(f). Claims that include the “means for [function]” language but also recite the structure for performing the function are not means-plus-function claims governed by § 112(f). Claims that include the “step for [function]” language but also recite an act for performing the function are not step-plus-function claims governed by § 112(f).

Except as otherwise stated herein or as is otherwise clear from context, the inventive methods comprising or consisting of more than one step may be carried out without concern for the order of the steps.

The terms “comprising,” “comprises,” “including,” “includes,” “having,” “haves,” and their grammatical equivalents are used herein to mean that other components or steps are optionally present. For example, an article comprising A, B, and C includes an article having only A, B, and C as well as articles having A, B, C, and other components. And a method comprising the steps A, B, and C includes methods having only the steps A, B, and C as well as methods having the steps A, B, C, and other steps.

Terms of degree, such as “substantially,” “about,” and “roughly” are used herein to denote features that satisfy their technological purpose equivalently to a feature that is “exact.” For example, a component A is “substantially” perpendicular to a second component B if A and B are at an angle such as to equivalently satisfy the technological purpose of A being perpendicular to B.

Except as otherwise stated herein, or as is otherwise clear from context, the term “or” is used herein in its inclusive sense. For example, “A or B” means “A or B, or both A and B.”

are perspective views illustrating an exemplary tankwith an exemplary thieves hatchcomprising a hatch baseand a hatch cover.depicts the tank with the coverremoved from the baseenabling access to the interior of the tankthrough a hatch portal.depicts the tankwith the coversecured in the base, closing the portaland thereby preventing (or limiting) unwanted ingress into the tank or egress from the tank through the portal.

illustrate the exemplary coversecured within the baseso as to seal the portal. (The tank has been omitted from the drawings for sake of clarity.)is a perspective view,is a side sectional view of section A-A of. The coverincludes an exhaust valve comprising an exhaust-valve platewith a spring housing bottomcontaining one end of an exhaust-valve springconnected to a top supportwith a spring housing topcontaining the other end of the exhaust-valve spring. The coveralso includes a suction valve comprising a suction-valve plateconnected to a suction-valve guide rod/guide-rod capand biased with a suction-valve spring. The exhaust and suction valve are positioned in a valve housingwhich in turn is secured in a ring basevia a valve ledgein the ring base. The ring baseis secured in the hatch baseusing one or more retaining springs. Mating surfaces (e.g., valve housingto ring base, ring baseto hatch base) are sealed as appropriate with, e.g., nitrile gaskets.

The exhaust and suction valves work to regulate the internal tank pressure: when the internal tank pressure exceeds the pressure outside the tank by a predetermined amount, the exhaust-valve springcompresses, opening a path for tank contents to vent; when the pressure outside the tank exceeds the internal tank pressure by a predetermined amount, the suction-valve springcompresses, opening a path into the tank allowing, e.g., atmosphere into the tank. Thus, the exhaust and suction valves work in concert to keep the internal tank pressure within a predetermined range of the pressure outside the tank. In operation, the exhaust-valve springand the suction-valve springare tuned (e.g., to a specific spring constant) to the predetermined pressure range for the particular tank/environment.

The retaining springsthat secure the coverin the closed position in the hatch baseenable quick insertion and removal of the coverto close and open the tank hatch. The retaining springsare tuned (e.g., spring constant, number of springs) to provide a retaining force sufficient to hold the cover in place when internal tank pressure exceeds to the pressure outside the tank by greater than the amount the required to open the exhaust valve.

is an exploded perspective view illustrating the exemplary components of the exemplary hatch cover.

are various views illustrating an exemplary hatch coveraccording to an aspect of the invention.are 3D perspective views illustrating the coverin high-pressure and low-pressure states respectively.are sectional views of the coverin a low-pressure state.is a side view of the cover.is a top view of the cover. The exemplary hatch coverincludes an internal-locking mechanismconfigured to selectively lock the coverin a hatch base and a valve assemblyconfigured to manage exhaust and intake of fluids to regulate the pressure in a tank.

The internal lockincludes a loading bracketand a plurality of bolts. The bracketincludes a channel ringconfigured with radial channelsto hold the bolts, and a track ringconfigured with tracksto engage and guide the bolts. The channel ringand track ringare circumferentially nested together, with the track ringinside the circumference of the channel ringThe inside edge of the channel ringengages a outside groove on the track ringsuch that the track ringand channel ringmay rotate relative to each other but may not translate relative to each other (they are substantially static translationally). The boltsare selectively positionable within the bracketto radially protrude to engage the hatch base (as illustrated in) or to radially retract to release from the hatch base (as illustrated in) for insertion or removal of the cover. The boltsengage a curved trackwithin the bracketsuch that: (1) rotation of the bracketin a first direction will cause the boltsto radially retract and (2) rotation in the second direction will cause the boltsto radially protrude. The boltsare biased by a plurality of springsto protrude. The bracketmay include one or more locating featuresto allow an operator to rotate the bracket to engage/disengage the boltswith the hatch base. (The rotation direction and extents are indicated by curved dashed arrowsin.)

The valve assemblyincludes: (1) an exhaust valve comprising a number of exhaust-valve springspositioned about exhaust-valve guide rodsand between an exhaust-valve plateand an exhaust-valve-spring loader(in this embodiment, a compression plate); and (2) a suction valve comprising a number of suction-valve springspositioned about suction-valve guide rodsand between a suction-valve guide-rod headand a suction-valve-spring loader(in this instance, a compression plate). The exhaust-valve springsare configured to push the exhaust-valve platetoward the tank when the coveris installed in a tank hatch, providing a force of F. The suction-valve springsare configured to pull the suction-valve plateaway from the tank when the coveris installed in a tank hatch, providing a force of F.

In operation, the coveris oriented such that the bottom surfaceof the exhaust-valve plateand the bottom surfaceof the suction-valve plateface the fluid in the tank (thus, the bottom surface of each is the valve plate's “tank-side surface” and the opposite surface of the plate is the “atmospheric-side surface”). The tank-side surface of the exhaust-valve platewill experience a force toward the atmospheric-side surface due to tank-fluid pressure. The atmospheric-side surface of the exhaust-valve platewill experience a force toward the tank-side surface due to atmospheric pressure and compressive loading of the exhaust-valve springs. The tank-side surface of the suction-valve platewill experience a force toward the atmospheric-side surface due to tank-fluid pressure. The atmospheric-side surface of the suction-valve platewill experience: (1) a force toward the tank-side surface due to atmospheric pressure and (2) a force away from the atmospheric-side surface due to compressive loading of the suction-valve springs(pulling the suction-valve plateout toward the atmospheric side).

As described in more detail below, the exhaust-valve assembly and the suction valve assembly are nested such that edge surfaces of the suction-valve plateseat with edge surfaces of the exhaust-valve plate. Edge surfaces of the exhaust-valve plateseat with surfaces of a bottom cover housing. When the force on the exhaust platedue to the tank-fluid pressure exceeds the force due to the combination of atmospheric pressure and the loading of the exhaust-springs, the exhaust-platewill move away from the tank, unseating from its sealing surfaces and allowing tank fluid to exhaust into atmosphere until the tank-fluid pressure drops below the level needed to compress the exhaust-valve springs. When the force on the suction platedue to atmospheric pressure exceeds the force due to the combination of tank-fluid pressure and the loading of the suction-springs, the suction-platewill move into the tank, unseating from its sealing surfaces and allowing atmospheric fluid to enter the tank until the tank-fluid pressure rises above the level needed to overcome the combination of atmospheric pressure and exhaust-valve springs.

In summary: (1) the exhaust valve opens when the force provided by tank fluid (F) is greater than the combined force provided by the atmosphere (F) and the exhaust-valve springs(F)—if F>F+F, then open the exhaust valve and (2) the suction valve opens when the force provided by the atmosphere (F) is greater than the combined force provided by the tank fluid (F) and suction-valve springs(F)—if F<F−F, then open the suction valve. In this way, tank pressure is automatically regulated.

The valve assemblycan be tuned for a particular application by changing the compressive loading on the exhaust-valve springsor suction-valve springs. In the exemplary hatch cover, the exhaust valve springscan be selectively loaded by changing the position of the exhaust-valve-spring loaderrelative to the exhaust-valve plate: (1) narrowing the distance between the exhaust-valve-spring-compression plateand the exhaust-valve plateincreases the compressive loading force of the exhaust valve springs (F), thus increasing the tank-fluid pressure at which the exhaust valve opens, (2) increasing the distance between the exhaust-valve-spring-compression plateand the exhaust-valve platedecreases the loading force of the exhaust-valve springs (F), thus decreasing the tank-fluid pressure at which the exhaust valve opens.

In the exemplary valve assembly, the exhaust-valve-spring compression plateis placed in threaded engagement with a valve-assembly retaining ringsuch that: (1) rotation of the exhaust-valve-spring compression platerelative to the valve-assembly retaining ringin a first direction moves the spring loadertoward the exhaust plateand thereby increases the loading force of the exhaust-valve springs (F), and (2) rotation of the exhaust-valve-spring compression platerelative to the valve-assembly retaining ringin a second direction moves the spring loaderaway from exhaust plateand thereby decreases the loading force of the exhaust-valve springs (FES). (The rotation direction and extents are indicated by a curved dashed arrowin. Counterclockwise rotation increases Fand clockwise rotation decreases F.) The rotation may be calibrated such that a given rotational position corresponds to a known F(or pressure equivalent). Thus, a scalemay be provided to enable the operator to configure the Fas appropriate. As illustrated in, the valve-assembly retaining ringmay include a spring-pressure indicatorthat corresponds to the scale. Rotating the retaining ringto place the indicatorat the desired location on the scalemoves the exhaust-valve-spring compression platerelative to the exhaust-valve plateto place it in a position that corresponds to the Fpressure indicated on the scale. In, the indicatoris positioned at 24 oz/inwhich moves the exhaust-valve-spring compression platedown toward the exhaust-valve plateto load the exhaust-valve springsto provide an Fes pressure of 24 oz/in. (The internal threadsof the retaining ringare visible in. The exhaust-valve-spring compression platehas corresponding outer threads.) In, the indicatoris positioned at 6.3 oz/inwhich moves the exhaust-valve-spring compression plateback away from the exhaust-valve plateto load the exhaust-valve springsto provide an Fpressure of 6.3 oz/in.

In the exemplary valve assembly, the force Fprovided by the suction-valve springsis controlled by positioning the suction-valve guide-rod headsrelative to the guide rods. Each suction-valve springis positioned between a guide-rod headand the suction-valve-spring loadersuch that the compressive load on the springmay be set by adjusting the position of the guide-rod headrelative to the suction-valve-spring loader. In this embodiment, the guide-rod headsare threaded into the guide rods. Threading the headsfurther into the guide rodswill increase the amount by which atmospheric pressure must exceed tank pressure before the suction valve opens.

illustrate further details of the exemplary hatch-cover locking assembly.is a 3D perspective of an exemplary bolt-loading bracket ringwith multiple hatch-base-engagement boltspositioned in radial channelsdispersed circumferentially about the channel ringLocating featuresand spring-retaining postsextend longitudinally up from the track ringis a top view.is a side view.is a top sectional view of section C-Cof.is a side sectional view of section C-Cof. In, the bolts(with angled hatching) are illustrated in a fully retracted position. The figure is overlayed with a second set of bolts′ (with cross-hatching and broken lines) illustrating the fully extended position. As the track ringis rotated circumferentially (as illustrated inwith the dashed curved arrows) the tracktravels along the boltbetween a fully retracted position at a first end of the trackto a fully extended position at a second end of the trackThe boltmay be configured with a T-shaped featureengaging a T-shaped slot forming the track. The trackis curved such that the first endis farther from the perimeter of the ringthan is the second end

is a top sectional view of section C-Cof, illustrating the engagement of the boltswith the tracksfor the exemplary hatch cover.is a side sectional view of section D-D of. Multiple lateral bolt-loading springsare disposed roughly tangentially near the circumference of the cover. A first end of each bolt-loading springconnects to a spring-retaining postof the bolt-loading carrier ringand a second end of each bolt-loading springconnects to a spring-retaining postof a top cover housing. The bolt-load springsbias the bolt-loading ringtoward the position to cause the boltsto protrude to engage a hatch base.

is a 3D perspective illustrating the engagement between the top cover housing, bolt-loading ring, and bolt-loading springs.is a side view.is a top view.is sectional view of section E-E of. The top cover housingincludes: (1) slotsthrough which the locating featuresof the track ringmay protrude and (2) reference featuresthat may be engaged by the operator to help rotate the track ringrelative to the housingand channel ringto move the boltradially in or out. For example, the operator may place a finger on a reference featureand a thumb on a locating featureand squeeze them together to rotate the track ringto cause the boltsto retract, allowing the coverto be removed from the hatch. In this embodiment, four bolt-loading springsare distributed at roughly 90-degree intervals near the circumference of the housingand track ring

illustrate further details of the exemplary valve assembly.is a 3D perspective illustrating the valve assembly.is a top view of the assembly.is a sectional view of section F-F of. In this embodiment, the valve assembly includes: (1) six sets of exhaust-valve rodsand springsuniformly distributed about the ring-shaped exhaust-valve plateand (2) three sets of suction-valve rodand springuniformly distributed about the disc shaped suction-valve plate. The suction-valve plateseats within the exhaust-valve plate, sealing at surface-interface. The exhaust-valve plateseats within the bottom cover housing, sealing at the surface-interface.

are sectional views analogous to the view of, but showing the state of the surface-interfaces in certain pressure conditions. In, a tank-pressure forceon the exhaust-valve plateexceeds the combined force of the atmosphere and exhaust-valve springs. This causes the exhaust-valve plateto move up out of its seat with the bottom cover housingand suction-valve plate. The surface-interfacesandare broken and tank fluid may exhaust through the opening. In, an atmospheric-pressure forceon the suction-valve plateexceeds the combined force of the tank-fluid pressure and suction-valve springs. This causes the suction-valve plateto move down out of its seat with the exhaust-valve plate. The surface-interfaceis broken and atmospheric fluid may enter the tank through the opening.

While the foregoing description is directed to the preferred embodiments of the invention, other and further embodiments of the invention will be apparent to those skilled in the art and may be made without departing from the basic scope of the invention. And features described with reference to one embodiment may be combined with other embodiments, even if not explicitly stated above, without departing from the scope of the invention. The scope of the invention is defined by the claims which follow.