CA2487572C - Storage tank overflow containment apparatus - Google Patents
Storage tank overflow containment apparatus Download PDFInfo
- Publication number
- CA2487572C CA2487572C CA002487572A CA2487572A CA2487572C CA 2487572 C CA2487572 C CA 2487572C CA 002487572 A CA002487572 A CA 002487572A CA 2487572 A CA2487572 A CA 2487572A CA 2487572 C CA2487572 C CA 2487572C
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- CA
- Canada
- Prior art keywords
- canister
- tank
- liquid
- float
- overflow
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D90/00—Component parts, details or accessories for large containers
- B65D90/22—Safety features
- B65D90/26—Overfill prevention
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D90/00—Component parts, details or accessories for large containers
- B65D90/22—Safety features
- B65D90/32—Arrangements for preventing, or minimising the effect of, excessive or insufficient pressure
- B65D90/34—Venting means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K24/00—Devices, e.g. valves, for venting or aerating enclosures
- F16K24/04—Devices, e.g. valves, for venting or aerating enclosures for venting only
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K24/00—Devices, e.g. valves, for venting or aerating enclosures
- F16K24/04—Devices, e.g. valves, for venting or aerating enclosures for venting only
- F16K24/042—Devices, e.g. valves, for venting or aerating enclosures for venting only actuated by a float
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K31/00—Actuating devices; Operating means; Releasing devices
- F16K31/12—Actuating devices; Operating means; Releasing devices actuated by fluid
- F16K31/18—Actuating devices; Operating means; Releasing devices actuated by fluid actuated by a float
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- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Loading And Unloading Of Fuel Tanks Or Ships (AREA)
- Filling Or Discharging Of Gas Storage Vessels (AREA)
Abstract
The present invention is a spill containment apparatus that may be mounted to the vent pipe of a liquid storage tank. The apparatus comprises a canister forming a reservoir for receiving liquid overflowing through the tank vent. If the overflow volume does not exceed the reservoir capacity, the liquid in the reservoir drains back into the tank when the tank is drawn down. If the overflow volume exceeds the reservoir capacity, the excess liquid is diverted through a canister outlet to a collection receptacle. In either event, the overflowing liquid never contacts or contaminates the exterior surfaces of the tank roof and walls, or the fill or natural soil in the vicinity of the tank. A canister vent that allows passage of vapours from the tank to the atmosphere during non- overflow conditions. If an overflow floods the canister, a check valve closes off the canister vent, thus preventing spillage through the canister vent.
Description
STORAGE TANK OVERFLOW CONTAINMENT APPARATUS
FIELD OF THE INVENTION
The present invention relates in general to storage tanks for liquids such as crude oil, and in particular relates to apparatus for containing overflow of liquid through vents of such tanks.
BACKGROUND OF THE INVENTION
Liquid storage tanks are used in many industrial applications. In the field of oil exploration and production, cylindrical field tanks, typically with shallow conical roofs, are commonly used as central collectors for crude oil flowing from one or more producing wells. The tanks are usually set on a layer of sand or gravel fill over an impermeable membrane. These tanks require venting to prevent pressure or vacuum build-up as the tanks are being filled or emptied, or due to fluctuations in ambient temperature and atmospheric pressure. This venting is typically provided in the form of a vent pipe extending through the tank roof, usually near the tank wall.
Overflow through storage tank roof vents can be a significant problem, particularly for oil storage tanks. Occasionally, such storage tanks are inadvertently overfilled, due to causes such as human error. A more common problem, however, is the phenomenon of "foam-over" that occurs when warm crude oil undergoes a drop in temperature, particularly when the ambient humidity is high. Crude oil in field storage tanks is typically kept heated by circulating a warm fluid through heating tubes immersed in the oil. For various practical reasons, it is common practice to transfer oil between field tanks, using tanker trucks that load oil from one tank and pump it into a tank at a different location. The oil cools down during transport, with its drop in temperature depending on how long the oil is in transit, and also depending on the ambient outside temperature (which is a particularly significant factor during in very cold winter conditions regularly experienced in Canada and other northern countries). When the tanker reaches its destination and pumps the cooler oil into a tank containing warm oil, large volumes of foam develop and can rise many feet above the liquid surface in the tank. This oil foam commonly builds up to the extent that it spews out of the tank roof vents, even when the liquid surface is well below the tank roof.
Foaming can occur even when no oil is being pumped into the tank. A
significant drop in temperature, particularly when accompanied by high relative humidity, can be sufficient to cause a substantial "head" of foam to develop above the surface of oil stored in an oil storage tank.
When a storage tank overflows through a roof vent, whether due to overfilling, foam-over, or some other cause, the liquid or foam (as the case may be) typically spills onto the tank roofs, down the tank walls, and onto the ground surface, and may even splash over the wall-to-roof junction and outwardly away from the tank. After such an overflow, considerable clean-up and/or remediation work is usually required.
First, the roof and wall surfaces need to be cleaned. Second, even if the gravel fill and impermeable membrane are in good condition, and thus effective to prevent the spillage
FIELD OF THE INVENTION
The present invention relates in general to storage tanks for liquids such as crude oil, and in particular relates to apparatus for containing overflow of liquid through vents of such tanks.
BACKGROUND OF THE INVENTION
Liquid storage tanks are used in many industrial applications. In the field of oil exploration and production, cylindrical field tanks, typically with shallow conical roofs, are commonly used as central collectors for crude oil flowing from one or more producing wells. The tanks are usually set on a layer of sand or gravel fill over an impermeable membrane. These tanks require venting to prevent pressure or vacuum build-up as the tanks are being filled or emptied, or due to fluctuations in ambient temperature and atmospheric pressure. This venting is typically provided in the form of a vent pipe extending through the tank roof, usually near the tank wall.
Overflow through storage tank roof vents can be a significant problem, particularly for oil storage tanks. Occasionally, such storage tanks are inadvertently overfilled, due to causes such as human error. A more common problem, however, is the phenomenon of "foam-over" that occurs when warm crude oil undergoes a drop in temperature, particularly when the ambient humidity is high. Crude oil in field storage tanks is typically kept heated by circulating a warm fluid through heating tubes immersed in the oil. For various practical reasons, it is common practice to transfer oil between field tanks, using tanker trucks that load oil from one tank and pump it into a tank at a different location. The oil cools down during transport, with its drop in temperature depending on how long the oil is in transit, and also depending on the ambient outside temperature (which is a particularly significant factor during in very cold winter conditions regularly experienced in Canada and other northern countries). When the tanker reaches its destination and pumps the cooler oil into a tank containing warm oil, large volumes of foam develop and can rise many feet above the liquid surface in the tank. This oil foam commonly builds up to the extent that it spews out of the tank roof vents, even when the liquid surface is well below the tank roof.
Foaming can occur even when no oil is being pumped into the tank. A
significant drop in temperature, particularly when accompanied by high relative humidity, can be sufficient to cause a substantial "head" of foam to develop above the surface of oil stored in an oil storage tank.
When a storage tank overflows through a roof vent, whether due to overfilling, foam-over, or some other cause, the liquid or foam (as the case may be) typically spills onto the tank roofs, down the tank walls, and onto the ground surface, and may even splash over the wall-to-roof junction and outwardly away from the tank. After such an overflow, considerable clean-up and/or remediation work is usually required.
First, the roof and wall surfaces need to be cleaned. Second, even if the gravel fill and impermeable membrane are in good condition, and thus effective to prevent the spillage
2 from contaminating the subsoil in the vicinity, the affected portion of the fill usually needs to be removed and replaced.
These clean-up operations are time-consuming and expensive, in terms of both labour and equipment requirements. Field tanks are often 30 to 40 feet or more in height, S so cleaning the roof and upper wall areas entails the use of man-lifts or other access equipment. Such equipment generally is not readily available at the tank site, and therefore needs to be transported to the site, adding significantly to the total cost and inconvenience of the clean-up. It is also costly to remove and replace contaminated fill material around the tanks, not to mention off site treatment and/or disposal of the fill.
The prior art discloses devices and apparatus directed to the general problem of containing overflow from liquid storage tanks. U.S. Patent No. 5,042,519 (Kerlin) discloses a fuel tank vent having a vent valve. A cylindrical housing is attached to the vent of a storage tank and contains a check ball and a float ball. The check ball and float ball are in contact with each other, and the check ball is movable to open and seal a vent aperture at the top of the housing. During normal operation, vapour from the tank can pass around the float ball and the check ball and out the vent aperture. If the tank is upset or overfilled, the fuel causes the float ball to move toward the vent aperture causing the check ball to do the same. If the overflow reaches a sufficient level, the check ball seals off the vent aperture, thus preventing spillage of the fuel.
U.S. Patent No. 5,346,093 (De Benedittis et al.) discloses an apparatus for containing overflow through the roof vent of a volatile fuel storage tank due to temperature-induced expansion of the fuel in the tank, such as in the particular case
These clean-up operations are time-consuming and expensive, in terms of both labour and equipment requirements. Field tanks are often 30 to 40 feet or more in height, S so cleaning the roof and upper wall areas entails the use of man-lifts or other access equipment. Such equipment generally is not readily available at the tank site, and therefore needs to be transported to the site, adding significantly to the total cost and inconvenience of the clean-up. It is also costly to remove and replace contaminated fill material around the tanks, not to mention off site treatment and/or disposal of the fill.
The prior art discloses devices and apparatus directed to the general problem of containing overflow from liquid storage tanks. U.S. Patent No. 5,042,519 (Kerlin) discloses a fuel tank vent having a vent valve. A cylindrical housing is attached to the vent of a storage tank and contains a check ball and a float ball. The check ball and float ball are in contact with each other, and the check ball is movable to open and seal a vent aperture at the top of the housing. During normal operation, vapour from the tank can pass around the float ball and the check ball and out the vent aperture. If the tank is upset or overfilled, the fuel causes the float ball to move toward the vent aperture causing the check ball to do the same. If the overflow reaches a sufficient level, the check ball seals off the vent aperture, thus preventing spillage of the fuel.
U.S. Patent No. 5,346,093 (De Benedittis et al.) discloses an apparatus for containing overflow through the roof vent of a volatile fuel storage tank due to temperature-induced expansion of the fuel in the tank, such as in the particular case
3 where the tank is overfilled in the sense that there is insufficient or no space at all above the fuel to accommodate expansion. To address this problem, the De Benedittis apparatus surrounds the tank vent with a collar that forms an overflow chamber with an internal weir. The overflow chamber will retain any expansion-induced overflow that does not rise above the weir. If the overflow liquid rises above the weir, it flows into a drainage channel into a dike formed around the base of the tank. The overflow chamber has a cover member with a downwardly curved splash plate disposed beneath it, with a vent space between the cover member and splash plate to allow for venting from both the tank and the overflow chamber. The splash plate is configured such that any fuel that happens to spurt rapidly upward through the vent will be deflected downward into the overflow chamber, rather than spilling out through the vent space of the apparatus.
Although these prior art apparatus and devices provide benefits in certain situations, they do not fully address the problems discussed previously. The Kerlin apparatus is directed primarily to preventing liquid from exiting a tank in various circumstances, and does not address the problem of removing excess liquid in the event of overfilling. The De Benedittis apparatus provides for removal of liquid overflowing through the tank vent. However, since it is directed only to containment of comparatively small overflow amounts due to fuel expansion, it does not provide means for preventing overflow and spillage from a tank that is being inadvertently and perhaps steadily overfilled beyond its volumetric capacity. If a tank fitted with the De Benedittis apparatus were exposed to overfill conditions of that sort, and if the flow into the overflow chamber were to exceed the flow capacity of the drainage channel, the overflow chamber would become flooded and liquid would escape through the vent space between
Although these prior art apparatus and devices provide benefits in certain situations, they do not fully address the problems discussed previously. The Kerlin apparatus is directed primarily to preventing liquid from exiting a tank in various circumstances, and does not address the problem of removing excess liquid in the event of overfilling. The De Benedittis apparatus provides for removal of liquid overflowing through the tank vent. However, since it is directed only to containment of comparatively small overflow amounts due to fuel expansion, it does not provide means for preventing overflow and spillage from a tank that is being inadvertently and perhaps steadily overfilled beyond its volumetric capacity. If a tank fitted with the De Benedittis apparatus were exposed to overfill conditions of that sort, and if the flow into the overflow chamber were to exceed the flow capacity of the drainage channel, the overflow chamber would become flooded and liquid would escape through the vent space between
4 the cover member and the splash plate, leading to clean-up and remediation problems of the type previously described.
For the foregoing reasons, there is a need for improved means for minimizing or preventing spillage due to overflow of liquid through tank vents, so as to reduce or S eliminate the clean-up efforts and expenses that typically result from such overflow, particularly for tanks containing crude oil or other potentially hazardous or dangerous liquids. The present invention is directed to these needs.
BRIEF DESCRIPTION OF THE INVENTION
In general terms, the present invention is a spill containment apparatus that may be mounted to the vent pipe of a liquid storage tank. The apparatus comprises a canister which has an overflow outlet, a canister vent opening, and a check valve assembly associated with the canister vent opening. The apparatus also has a tank vent opening adaptable for substantially liquid-tight mounting over the tank vent pipe. The overflow outlet may be disposed at a distance above the base of the canister, so as to form a reservoir in the lower section of the canister, for receiving and containing liquid overflowing from the tank through the tank vent. If the volume of overflowed liquid does not exceed the reservoir capacity, the liquid in the reservoir drains back into the tank when the tank is drawn down or emptied. If the volume of overflowed liquid exceeds the reservoir capacity, the apparatus diverts the excess liquid through a conduit to an overflow collection receptacle, typically located at grade level near the base of the tank.
S
In either event, the overflowing liquid never contacts or contaminates the exterior surfaces of the tank roof and walls, or the fill or natural soil in the vicinity of the tank.
The provision for a reservoir within the canister, as described above, is not essential to the invention. In preferred embodiments, the overflow outlet is located as S close to the base of the canister as possible in order to minimize the overall height of the apparatus, thus facilitating access to the canister vent. It is commonly desired to add chemicals such as defoaming agents into oil storage tanks, and this is commonly done by pouring the chemicals into the tank vent, which is usually accessible to a worker standing on a ladder running up the sidewall of the tank. When the apparatus of the present invention is fitted to the tank vent, chemicals can poured in through the canister vent, but it is preferable to keep the height to the top of the canister vent low enough that it can be conveniently reached from the ladder, without having to climb onto the tank roof.
The apparatus provides the foregoing benefits without impeding the function of the tank vent during normal operating conditions. The canister vent allows vapours to pass from the tank through the canister to atmosphere during non-overflow conditions. If overflow liquid in the canister rises above a certain level, a check valve closes off the canister vent, thus preventing spillage through the canister vent, and ensuring that the overflow passes out of the canister through the outlet only.
Accordingly, in one embodiment the invention is an overflow containment apparatus for use with a liquid storage tank having a tank vent, said apparatus comprising:
(a) a canister having a top section, a base section, and sidewall means interconnecting the top section and base section, wherein:
a.l the top section has a canister vent opening;
a.2 the base section has a tank vent opening; and a.3 the canister has an overflow outlet;
(b) canister mounting means, for mounting the canister to the tank, with the tank vent in substantially liquid-tight engagement with the tank vent opening;
(c) a check valve assembly comprising:
c.l float retainer means disposed inside the canister below the canister vent opening, said float retainer means having openings through which liquid can flow; and c.2 a float retained and vertically movable within the float retainer means in response to fluctuations in liquid level within the canister, said float being adapted to form a substantially liquid-tight seal against the canister vent opening when urged upwardly thereagainst;
wherein the float retainer means is configured such that the float will be substantially centrally aligned with the canister vent opening when raised theretoward;
such that:
(d) liquid entering the canister through the storage tank vent, and rising above the bottom of the overflow outlet, will flow out of the canister through the overflow outlet; and (e) liquid rising above the overflow outlet and approaching the top section of S the canister will raise the float and urge it into substantially liquid-tight engagement against the canister vent opening.
The canister may be of any suitable geometric configuration. For instance, the canister may be of rectilinear, box-like construction, with a plurality of substantially planar sidewalk. Alternatively, the canister may be of substantially cylindrical configuration, with curvilinear sidewalk.
In the preferred embodiment of the invention, the overflow outlet comprises an open pipe or other suitable conduit extending laterally through the canister sidewall means. Preferably the cross-sectional area of the overflow outlet is larger than that of the roof vent, in order to prevent back pressure that might impeded flow out of the canister.
Oil storage tanks commonly have a second roof vent (typically near the roof peak), in addition to a first roof vent (typically near the tank wall) to which the present invention is most conveniently and preferably mounted. If flow out of the canister fitted to the first roof vent is impeded due to pressure build-up, oil foam can readily rise and spew out the peak vent. This potential problem could of course be addressed by fitting the second or upper roof vent with the apparatus of the present invention. However, if the overflow outlet is sufficiently larger than the (first) roof vent to which it is mounted, oil foam will not rise high enough to reach the second roof vent, so a single canister in accordance with the present invention will usually be sufficient to prevent foam over onto the tank roof and walls. For example, it has been found through field observation that an overflow outlet with a diameter of about 10 inches (250 mm) will generally be sufficient to prevent undesirable pressure build-up in canisters mounted to tank roof vents having a diameter of about 8.5 inches (215 mm).
Also in the preferred embodiment, the overflow outlet is disposed at a selected distance above the canister base, such that the portion of the canister between the canister base and the bottom of the overflow outlet defines a reservoir, and such that liquid entering the canister from the storage tank through the tank vent will firstly accumulate in the reservoir section of the canister, and will flow out through the overflow outlet when the liquid level rises above the bottom of the overflow outlet (i.e., above the invert elevation of the outlet).
The float must be light enough to float upon the liquid stored in the tank, and preferably is made from a material having a specific gravity substantially less than that of the liquid, so that a substantial portion of the float will project above the liquid surface upon which it floats. In applications where foam-over is a concern, such as in an oil storage tank, the float must be light enough to float on the foam so that it will seal against the canister vent opening so as to substantially prevent passage of foam thereinto. For example, the float may be a hollow float with a thin plastic skin, such that the effective density of the float substantially less than the effective density of oil foam.
In the preferred embodiment of the invention, the canister vent opening is circular and the float is substantially spherical. The diameter of the float is sufficiently greater than the diameter of the canister vent opening such that the float will readily seal against the canister vent opening when pushed up against it by buoyancy forces from overflow liquid in the canister, but will not be susceptible to becoming jammed or stuck in the canister vent opening when the overflow liquid recedes.
The float retainer means preferably will be a cage-like enclosure suspended beneath the top section of the canister. Alternatively, the float retainer means may be a largely solid-walled enclosure with openings or perforations to permit inflow of liquid from the canister. The float retainer means is preferably of generally cylindrical configuration and disposed substantially concentrically with the canister vent opening, such that the float will tend to be centered on the canister vent opening when raised theretoward. Where a spherical float is used, the lower portion of the float retainer is preferably rounded to conveniently accommodate the shape of the float.
The apparatus may also include a secondary vent pipe extending upward from the canister vent opening. In alternative embodiments, the secondary vent pipe may extend below the top section of the canister, in which case the bottom of the secondary vent pipe will effectively serve as the canister vent opening against which the float will seal when the liquid level rises high enough within the canister.
The canister mounting means may include a threaded fitting, whereby a threaded connection can be made between the canister and the tank vent pipe.
Alternatively, the connection between the canister and the tank vent pipe may be made with a slip-on or press-fit type of fitting, using suitable gaskets or other appropriate sealing materials to provide a substantially liquid-tight connection.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described with reference to the accompanying figures, in which numerical references denote like parts, and in which:
FIGURE 1 is a cross-sectional side view of an overflow containment apparatus in accordance with one embodiment of the present invention, shown with the canister of the invention partially filled with overflow liquid from a storage tank vent, and with the liquid being discharged from the canister through the canister outlet.
FIGURE 2 is a cross-sectional side view of the apparatus of Figure l, with the canister flooded above the level of the canister outlet, and with the float engaging the canister vent opening.
FIGURE 3 is a partial elevation of a liquid storage tank with the overflow containment apparatus of the present invention mounted to the tank vent pipe, with a conduit fitted to the canister outlet for conveying liquid from the canister to a collection receptacle.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Refernng to Figures 1 and 2, the spill containment apparatus of the present invention (generally indicated by reference numeral 10) comprises a canister 20 having a top section 22, a base section 24, and sidewall means 26 interconnecting the top section 22 and the base section 24. The top section 22 has a canister vent opening 30, which in the preferred embodiment will be circular. Also in the preferred embodiment, the apparatus 10 includes a secondary vent pipe 32 associated with the canister vent opening 30.
As conceptually illustrated in Figures 2 and 3, the base section 24 has a tank vent opening 40 with associated for mounting the canister 20 to the vent pipe of a liquid storage tank in substantially liquid-tight fashion. The canister mounting means 42 may include a threaded, welded, or friction-fit connection means, or any other known type of connection for making liquid-tight, non-pressurized connections.
An overflow outlet 50 is provided in association with the sidewall means 26, for discharging liquids that accumulate in the canister 20. A conduit 52 may be connected to the overflow outlet 50 to convey liquids from inside the canister 20 to a collection receptacle (not shown).
A check valve assembly 60 is disposed inside the canister 20 beneath the top section 22 and generally centered under the canister vent opening 40. The check valve assembly 60 comprises float retainer means 62 which retainingly encloses a float 64. The float retainer means 62 is may be of any suitable construction that allows for free flow of fluids into and out of the space inside the float retainer means 62. In the preferred embodiment, the float retainer means 62 is provided in the form of a cage-like structure.
Alternatively, the float retainer means 62 may be fashioned with a screen-type material, or it may be in the form of a largely solid-walled enclosure having multiple openings to allow passage of fluids.
The float 64 is configured and adapted such that it will form a substantially liquid-tight seal with the canister vent opening 40 when urged against the canister vent opening 40. Accordingly, in the preferred embodiment, where the canister vent opening 40 is circular, the float 64 is spherical, with a diameter greater than the diameter of the circular canister vent opening 40. The float 64 has a specific gravity less than that of the liquid stored in the tank to which the canister 20 is mounted. The diameter and specific gravity of the float 64 are preferably selected such that as buoyancy forces from liquid accumulating inside the canister 20 cause the float 64 to rise inside the float retainer means 62, the float 64 will seal against the canister vent opening 40 before the liquid level reaches the canister vent opening 40, as illustrated in Figure 2.
The overflow outlet 50 may be located at or near the base of the sidewall means 26, in which case liquid overflowing from the storage tank into the canister 20 will tend to flow directly out of the canister 20 through the overflow outlet 50.
However, in alternative embodiments, as illustrated in Figures 2 and 3, the overflow outlet 50 is positioned in the sidewall means 26 at a distance above the base section 24 such that there will be a lower sidewall section 28 below the overflow outlet 50. In this configuration, the portion of the canister 20 below the lower sidewall section 28 defines a reservoir 29 in which a certain volume of overflow liquid can accumulate before liquid begins flowing out through the overflow outlet 50.
The operation and functioning of the overflow containment apparatus 10 may be readily understood by reference to Figures 1 and 2 along with Figure 3, which illustrates a liquid storage tank 70 with sidewall 72, roof 74, and vent pipe 76 disposed in roof 74.
The canister 20 is secured to vent pipe 76 by means of canister mounting means 42 in substantially liquid-tight fashion so that any liquid overflowing from storage tank 70 through vent pipe 76 will flow into canister 20. Overflow conduit 52 is connected to overflow outlet 50 and leads to an overflow collection receptacle.
During normal operating conditions, when the liquid level in the storage tank is below the vent pipe 76, float 64 sits at the bottom of float retainer means 62 and away from canister vent opening 40. Vapours from storage tank 70 can exit storage tank 70 through vent pipe 76 into canister 20, and then into float retainer means 62 and out to atmosphere through canister vent opening 40, as indicated by vapour flow arrows V.
During tank overflow conditions, liquid from storage tank 70 rises into canister 20 through vent pipe 76. As long as the overflow liquid is at or below level L-1 (i.e., where overflow outlet 50 meets lower sidewall section 28), the overflow is retained in the reservoir section 29 of canister 20. As the contents of storage tank 70 are drawn down, the overflow liquid accumulated in the reservoir 29 will flow back into storage tank 70 by gravity. If the overflow liquid rises above level L-1, it will begin to flow out overflow outlet 50 through conduit 52 to an overflow collection receptacle.
As the liquid rises further within canister 20, it begins to flow into the float retainer means 62 and exerts buoyancy forces on the float 64. If the liquid level in the canister 20 continues to rise, it will urge the float 64 (guided by the float retainer means 62) into substantially liquid-tight sealing engagement with canister vent opening 40, as shown in Figure 3. Overflow liquid will continue to flow out of canister 20 through overflow outlet 50, and thence to the collection receptacle, but float 64 prevents any outflow of liquid through canister vent opening 40.
In the foregoing fashion, the present invention prevents liquids overflowing through storage tank vents from spilling onto the tank roof and walls, and onto surrounding grade surfaces. The invention provides these significant operational benefits without impeding the venting of vapours from the tank during normal operating conditions.
It will be readily appreciated by those skilled in the art that various modifications of the present invention may be devised without departing from the essential concept of 1 S the invention, and all such modifications are intended to be included in the scope of the claims appended hereto.
In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following that word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one such element.
For the foregoing reasons, there is a need for improved means for minimizing or preventing spillage due to overflow of liquid through tank vents, so as to reduce or S eliminate the clean-up efforts and expenses that typically result from such overflow, particularly for tanks containing crude oil or other potentially hazardous or dangerous liquids. The present invention is directed to these needs.
BRIEF DESCRIPTION OF THE INVENTION
In general terms, the present invention is a spill containment apparatus that may be mounted to the vent pipe of a liquid storage tank. The apparatus comprises a canister which has an overflow outlet, a canister vent opening, and a check valve assembly associated with the canister vent opening. The apparatus also has a tank vent opening adaptable for substantially liquid-tight mounting over the tank vent pipe. The overflow outlet may be disposed at a distance above the base of the canister, so as to form a reservoir in the lower section of the canister, for receiving and containing liquid overflowing from the tank through the tank vent. If the volume of overflowed liquid does not exceed the reservoir capacity, the liquid in the reservoir drains back into the tank when the tank is drawn down or emptied. If the volume of overflowed liquid exceeds the reservoir capacity, the apparatus diverts the excess liquid through a conduit to an overflow collection receptacle, typically located at grade level near the base of the tank.
S
In either event, the overflowing liquid never contacts or contaminates the exterior surfaces of the tank roof and walls, or the fill or natural soil in the vicinity of the tank.
The provision for a reservoir within the canister, as described above, is not essential to the invention. In preferred embodiments, the overflow outlet is located as S close to the base of the canister as possible in order to minimize the overall height of the apparatus, thus facilitating access to the canister vent. It is commonly desired to add chemicals such as defoaming agents into oil storage tanks, and this is commonly done by pouring the chemicals into the tank vent, which is usually accessible to a worker standing on a ladder running up the sidewall of the tank. When the apparatus of the present invention is fitted to the tank vent, chemicals can poured in through the canister vent, but it is preferable to keep the height to the top of the canister vent low enough that it can be conveniently reached from the ladder, without having to climb onto the tank roof.
The apparatus provides the foregoing benefits without impeding the function of the tank vent during normal operating conditions. The canister vent allows vapours to pass from the tank through the canister to atmosphere during non-overflow conditions. If overflow liquid in the canister rises above a certain level, a check valve closes off the canister vent, thus preventing spillage through the canister vent, and ensuring that the overflow passes out of the canister through the outlet only.
Accordingly, in one embodiment the invention is an overflow containment apparatus for use with a liquid storage tank having a tank vent, said apparatus comprising:
(a) a canister having a top section, a base section, and sidewall means interconnecting the top section and base section, wherein:
a.l the top section has a canister vent opening;
a.2 the base section has a tank vent opening; and a.3 the canister has an overflow outlet;
(b) canister mounting means, for mounting the canister to the tank, with the tank vent in substantially liquid-tight engagement with the tank vent opening;
(c) a check valve assembly comprising:
c.l float retainer means disposed inside the canister below the canister vent opening, said float retainer means having openings through which liquid can flow; and c.2 a float retained and vertically movable within the float retainer means in response to fluctuations in liquid level within the canister, said float being adapted to form a substantially liquid-tight seal against the canister vent opening when urged upwardly thereagainst;
wherein the float retainer means is configured such that the float will be substantially centrally aligned with the canister vent opening when raised theretoward;
such that:
(d) liquid entering the canister through the storage tank vent, and rising above the bottom of the overflow outlet, will flow out of the canister through the overflow outlet; and (e) liquid rising above the overflow outlet and approaching the top section of S the canister will raise the float and urge it into substantially liquid-tight engagement against the canister vent opening.
The canister may be of any suitable geometric configuration. For instance, the canister may be of rectilinear, box-like construction, with a plurality of substantially planar sidewalk. Alternatively, the canister may be of substantially cylindrical configuration, with curvilinear sidewalk.
In the preferred embodiment of the invention, the overflow outlet comprises an open pipe or other suitable conduit extending laterally through the canister sidewall means. Preferably the cross-sectional area of the overflow outlet is larger than that of the roof vent, in order to prevent back pressure that might impeded flow out of the canister.
Oil storage tanks commonly have a second roof vent (typically near the roof peak), in addition to a first roof vent (typically near the tank wall) to which the present invention is most conveniently and preferably mounted. If flow out of the canister fitted to the first roof vent is impeded due to pressure build-up, oil foam can readily rise and spew out the peak vent. This potential problem could of course be addressed by fitting the second or upper roof vent with the apparatus of the present invention. However, if the overflow outlet is sufficiently larger than the (first) roof vent to which it is mounted, oil foam will not rise high enough to reach the second roof vent, so a single canister in accordance with the present invention will usually be sufficient to prevent foam over onto the tank roof and walls. For example, it has been found through field observation that an overflow outlet with a diameter of about 10 inches (250 mm) will generally be sufficient to prevent undesirable pressure build-up in canisters mounted to tank roof vents having a diameter of about 8.5 inches (215 mm).
Also in the preferred embodiment, the overflow outlet is disposed at a selected distance above the canister base, such that the portion of the canister between the canister base and the bottom of the overflow outlet defines a reservoir, and such that liquid entering the canister from the storage tank through the tank vent will firstly accumulate in the reservoir section of the canister, and will flow out through the overflow outlet when the liquid level rises above the bottom of the overflow outlet (i.e., above the invert elevation of the outlet).
The float must be light enough to float upon the liquid stored in the tank, and preferably is made from a material having a specific gravity substantially less than that of the liquid, so that a substantial portion of the float will project above the liquid surface upon which it floats. In applications where foam-over is a concern, such as in an oil storage tank, the float must be light enough to float on the foam so that it will seal against the canister vent opening so as to substantially prevent passage of foam thereinto. For example, the float may be a hollow float with a thin plastic skin, such that the effective density of the float substantially less than the effective density of oil foam.
In the preferred embodiment of the invention, the canister vent opening is circular and the float is substantially spherical. The diameter of the float is sufficiently greater than the diameter of the canister vent opening such that the float will readily seal against the canister vent opening when pushed up against it by buoyancy forces from overflow liquid in the canister, but will not be susceptible to becoming jammed or stuck in the canister vent opening when the overflow liquid recedes.
The float retainer means preferably will be a cage-like enclosure suspended beneath the top section of the canister. Alternatively, the float retainer means may be a largely solid-walled enclosure with openings or perforations to permit inflow of liquid from the canister. The float retainer means is preferably of generally cylindrical configuration and disposed substantially concentrically with the canister vent opening, such that the float will tend to be centered on the canister vent opening when raised theretoward. Where a spherical float is used, the lower portion of the float retainer is preferably rounded to conveniently accommodate the shape of the float.
The apparatus may also include a secondary vent pipe extending upward from the canister vent opening. In alternative embodiments, the secondary vent pipe may extend below the top section of the canister, in which case the bottom of the secondary vent pipe will effectively serve as the canister vent opening against which the float will seal when the liquid level rises high enough within the canister.
The canister mounting means may include a threaded fitting, whereby a threaded connection can be made between the canister and the tank vent pipe.
Alternatively, the connection between the canister and the tank vent pipe may be made with a slip-on or press-fit type of fitting, using suitable gaskets or other appropriate sealing materials to provide a substantially liquid-tight connection.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described with reference to the accompanying figures, in which numerical references denote like parts, and in which:
FIGURE 1 is a cross-sectional side view of an overflow containment apparatus in accordance with one embodiment of the present invention, shown with the canister of the invention partially filled with overflow liquid from a storage tank vent, and with the liquid being discharged from the canister through the canister outlet.
FIGURE 2 is a cross-sectional side view of the apparatus of Figure l, with the canister flooded above the level of the canister outlet, and with the float engaging the canister vent opening.
FIGURE 3 is a partial elevation of a liquid storage tank with the overflow containment apparatus of the present invention mounted to the tank vent pipe, with a conduit fitted to the canister outlet for conveying liquid from the canister to a collection receptacle.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Refernng to Figures 1 and 2, the spill containment apparatus of the present invention (generally indicated by reference numeral 10) comprises a canister 20 having a top section 22, a base section 24, and sidewall means 26 interconnecting the top section 22 and the base section 24. The top section 22 has a canister vent opening 30, which in the preferred embodiment will be circular. Also in the preferred embodiment, the apparatus 10 includes a secondary vent pipe 32 associated with the canister vent opening 30.
As conceptually illustrated in Figures 2 and 3, the base section 24 has a tank vent opening 40 with associated for mounting the canister 20 to the vent pipe of a liquid storage tank in substantially liquid-tight fashion. The canister mounting means 42 may include a threaded, welded, or friction-fit connection means, or any other known type of connection for making liquid-tight, non-pressurized connections.
An overflow outlet 50 is provided in association with the sidewall means 26, for discharging liquids that accumulate in the canister 20. A conduit 52 may be connected to the overflow outlet 50 to convey liquids from inside the canister 20 to a collection receptacle (not shown).
A check valve assembly 60 is disposed inside the canister 20 beneath the top section 22 and generally centered under the canister vent opening 40. The check valve assembly 60 comprises float retainer means 62 which retainingly encloses a float 64. The float retainer means 62 is may be of any suitable construction that allows for free flow of fluids into and out of the space inside the float retainer means 62. In the preferred embodiment, the float retainer means 62 is provided in the form of a cage-like structure.
Alternatively, the float retainer means 62 may be fashioned with a screen-type material, or it may be in the form of a largely solid-walled enclosure having multiple openings to allow passage of fluids.
The float 64 is configured and adapted such that it will form a substantially liquid-tight seal with the canister vent opening 40 when urged against the canister vent opening 40. Accordingly, in the preferred embodiment, where the canister vent opening 40 is circular, the float 64 is spherical, with a diameter greater than the diameter of the circular canister vent opening 40. The float 64 has a specific gravity less than that of the liquid stored in the tank to which the canister 20 is mounted. The diameter and specific gravity of the float 64 are preferably selected such that as buoyancy forces from liquid accumulating inside the canister 20 cause the float 64 to rise inside the float retainer means 62, the float 64 will seal against the canister vent opening 40 before the liquid level reaches the canister vent opening 40, as illustrated in Figure 2.
The overflow outlet 50 may be located at or near the base of the sidewall means 26, in which case liquid overflowing from the storage tank into the canister 20 will tend to flow directly out of the canister 20 through the overflow outlet 50.
However, in alternative embodiments, as illustrated in Figures 2 and 3, the overflow outlet 50 is positioned in the sidewall means 26 at a distance above the base section 24 such that there will be a lower sidewall section 28 below the overflow outlet 50. In this configuration, the portion of the canister 20 below the lower sidewall section 28 defines a reservoir 29 in which a certain volume of overflow liquid can accumulate before liquid begins flowing out through the overflow outlet 50.
The operation and functioning of the overflow containment apparatus 10 may be readily understood by reference to Figures 1 and 2 along with Figure 3, which illustrates a liquid storage tank 70 with sidewall 72, roof 74, and vent pipe 76 disposed in roof 74.
The canister 20 is secured to vent pipe 76 by means of canister mounting means 42 in substantially liquid-tight fashion so that any liquid overflowing from storage tank 70 through vent pipe 76 will flow into canister 20. Overflow conduit 52 is connected to overflow outlet 50 and leads to an overflow collection receptacle.
During normal operating conditions, when the liquid level in the storage tank is below the vent pipe 76, float 64 sits at the bottom of float retainer means 62 and away from canister vent opening 40. Vapours from storage tank 70 can exit storage tank 70 through vent pipe 76 into canister 20, and then into float retainer means 62 and out to atmosphere through canister vent opening 40, as indicated by vapour flow arrows V.
During tank overflow conditions, liquid from storage tank 70 rises into canister 20 through vent pipe 76. As long as the overflow liquid is at or below level L-1 (i.e., where overflow outlet 50 meets lower sidewall section 28), the overflow is retained in the reservoir section 29 of canister 20. As the contents of storage tank 70 are drawn down, the overflow liquid accumulated in the reservoir 29 will flow back into storage tank 70 by gravity. If the overflow liquid rises above level L-1, it will begin to flow out overflow outlet 50 through conduit 52 to an overflow collection receptacle.
As the liquid rises further within canister 20, it begins to flow into the float retainer means 62 and exerts buoyancy forces on the float 64. If the liquid level in the canister 20 continues to rise, it will urge the float 64 (guided by the float retainer means 62) into substantially liquid-tight sealing engagement with canister vent opening 40, as shown in Figure 3. Overflow liquid will continue to flow out of canister 20 through overflow outlet 50, and thence to the collection receptacle, but float 64 prevents any outflow of liquid through canister vent opening 40.
In the foregoing fashion, the present invention prevents liquids overflowing through storage tank vents from spilling onto the tank roof and walls, and onto surrounding grade surfaces. The invention provides these significant operational benefits without impeding the venting of vapours from the tank during normal operating conditions.
It will be readily appreciated by those skilled in the art that various modifications of the present invention may be devised without departing from the essential concept of 1 S the invention, and all such modifications are intended to be included in the scope of the claims appended hereto.
In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following that word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one such element.
Claims (15)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An overflow containment apparatus for use with a liquid storage tank having a tank vent, said apparatus comprising:
(a) a canister having a top section, a base section, and sidewall means interconnecting the top section and base section, wherein:
a.1 the top section has a canister vent opening;
a.2 the base section has a tank vent opening; and a.3 the canister has an overflow outlet;
(b) canister mounting means, for mounting the canister to the tank, with the tank vent in substantially liquid-tight engagement with the tank vent opening;
(c) a check valve assembly comprising:
c.1 float retainer means disposed inside the canister below the canister vent opening, said float retainer means having openings through which liquid can flow; and c.2 a float retained and vertically movable within the float retainer means in response to fluctuations in liquid level within the canister, said float being adapted to form a substantially liquid-tight seal against the canister vent opening when urged upwardly thereagainst;
wherein the float retainer means is configured such that the float will be substantially centrally aligned with the canister vent opening when raised theretoward;
such that:
(d) liquid entering the canister through the storage tank vent, and rising above the bottom of the overflow outlet, will flow out of the canister through the overflow outlet; and (e) liquid rising above the overflow outlet and approaching the top section of the canister will raise the float and urge it into substantially liquid-tight engagement against the canister vent opening.
(a) a canister having a top section, a base section, and sidewall means interconnecting the top section and base section, wherein:
a.1 the top section has a canister vent opening;
a.2 the base section has a tank vent opening; and a.3 the canister has an overflow outlet;
(b) canister mounting means, for mounting the canister to the tank, with the tank vent in substantially liquid-tight engagement with the tank vent opening;
(c) a check valve assembly comprising:
c.1 float retainer means disposed inside the canister below the canister vent opening, said float retainer means having openings through which liquid can flow; and c.2 a float retained and vertically movable within the float retainer means in response to fluctuations in liquid level within the canister, said float being adapted to form a substantially liquid-tight seal against the canister vent opening when urged upwardly thereagainst;
wherein the float retainer means is configured such that the float will be substantially centrally aligned with the canister vent opening when raised theretoward;
such that:
(d) liquid entering the canister through the storage tank vent, and rising above the bottom of the overflow outlet, will flow out of the canister through the overflow outlet; and (e) liquid rising above the overflow outlet and approaching the top section of the canister will raise the float and urge it into substantially liquid-tight engagement against the canister vent opening.
2. The apparatus of Claim 1 wherein the sidewall means comprises a plurality of substantially planar walls.
3. The apparatus of Claim 1 wherein the side wall means comprises a curvilinear wall.
4. The apparatus of Claim 1 wherein the overflow outlet comprises a conduit extending through the sidewall means.
S. The apparatus of Claim 1 wherein the overflow outlet is connected to a conduit for conveying liquids from the outlet to an overflow collection receptacle.
6. The apparatus of Claim 1 wherein the overflow outlet is disposed at a selected distance above the canister base, such that the portion of the canister between the canister base and the level of the bottom of the overflow outlet defines a reservoir, and such that liquid entering the canister from the storage tank through the tank vent will firstly accumulate in the reservoir section of the canister, and will flow out of the canister through the overflow outlet when the liquid level rises above the bottom of the overflow outlet.
7. The apparatus of Claim 1 wherein the float retainer means comprises a cage-like enclosure mounted to and extending downward from the top section of the canister.
8. The apparatus of Claim 1 wherein the float is substantially spherical.
9. The apparatus of Claim 1 wherein the cage is substantially cylindrical.
10. The apparatus of Claim 1 wherein the canister mounting means comprises a threaded connection.
11. The apparatus of Claim 1 wherein the canister mounting means comprises a fitting adapted for press-fit engagement over the tank vent.
12. The apparatus of Claim 1, further comprising a conduit extending from the overflow outlet to overflow collection means.
13 . The apparatus of Claim 12 wherein the conduit is a pipe.
14. The apparatus of Claim 1, wherein the cross-sectional area of the overflow outlet is greater than the cross-sectional area of the tank vent.
15. The apparatus of Claim 1 wherein the float is hollow.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002487572A CA2487572C (en) | 2004-02-19 | 2004-11-16 | Storage tank overflow containment apparatus |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2,455,578 | 2004-02-19 | ||
| CA2455578 | 2004-02-19 | ||
| CA002487572A CA2487572C (en) | 2004-02-19 | 2004-11-16 | Storage tank overflow containment apparatus |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2487572A1 CA2487572A1 (en) | 2005-08-19 |
| CA2487572C true CA2487572C (en) | 2007-08-14 |
Family
ID=34888076
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002487572A Expired - Fee Related CA2487572C (en) | 2004-02-19 | 2004-11-16 | Storage tank overflow containment apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2487572C (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN202030233U (en) * | 2011-04-26 | 2011-11-09 | 曾德邻 | Meandering airway and anti-overflow structure |
| FR2998043A1 (en) * | 2012-11-12 | 2014-05-16 | Sietar & Vti | Atmospheric storage device i.e. BDL balloon, for storing and bailing hot water used in e.g. food industry, has stainless steel float for supporting stainless steel hose, and internal outlet associated with anti-overpressure overflow valve |
| CN114701769B (en) * | 2022-03-14 | 2024-01-30 | 华能曲阜热电有限公司 | Anti-overflow device of high-temperature hot water tank |
-
2004
- 2004-11-16 CA CA002487572A patent/CA2487572C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2487572A1 (en) | 2005-08-19 |
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Effective date: 20121116 |