CA2070939A1 - Storage tank with secondary containment - Google Patents
Storage tank with secondary containmentInfo
- Publication number
- CA2070939A1 CA2070939A1 CA 2070939 CA2070939A CA2070939A1 CA 2070939 A1 CA2070939 A1 CA 2070939A1 CA 2070939 CA2070939 CA 2070939 CA 2070939 A CA2070939 A CA 2070939A CA 2070939 A1 CA2070939 A1 CA 2070939A1
- Authority
- CA
- Canada
- Prior art keywords
- tank
- storage tank
- side wall
- cover
- explosion
- 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.)
- Abandoned
Links
- 238000004880 explosion Methods 0.000 claims abstract description 34
- 239000007789 gas Substances 0.000 claims abstract description 14
- 238000002485 combustion reaction Methods 0.000 claims abstract description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000001301 oxygen Substances 0.000 claims abstract description 7
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 7
- 239000000463 material Substances 0.000 claims description 15
- 239000003517 fume Substances 0.000 claims description 5
- 230000000717 retained effect Effects 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 239000007788 liquid Substances 0.000 description 6
- 239000000356 contaminant Substances 0.000 description 4
- 238000010276 construction Methods 0.000 description 3
- 238000007689 inspection Methods 0.000 description 3
- 230000002093 peripheral effect Effects 0.000 description 3
- 239000002689 soil Substances 0.000 description 3
- 238000011109 contamination Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000013022 venting Methods 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000004941 influx Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 230000007480 spreading Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
-
- 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
- B65D90/24—Spillage-retaining means, e.g. recovery ponds
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Filling Or Discharging Of Gas Storage Vessels (AREA)
Abstract
STORAGE TANK WITH SECONDARY CONTAINMENT
ABSTRACT OF THE DISCLOSURE
A storage tank with secondary containment includes a cylindrical inner tank which is mounted within a rectangular secondary containment with a horizontal flat base and vertical upstanding walls. A portion of the inner tank projects above the side walls to allow access for filling etc..
The area between the top edge of the vertical side wall and the adjacent portion of the tank is covered by a respective one of a plurality of cover panels each of which includes a top edge which is wedged under a flange on the tank and extends therefrom downwardly and outwardly to a vertical flange bolted to the vertical side wall. The cover panel thus acts to shed rainwater and the like. The cover panels are provided with explosion vents each in the form of a duct extending upwardly from the cover panel so as to direct flames and explosion gases away from the top part of the inner tank. Each duct is covered by a flap member which can open under the pressure from the gases but closes under its weight to prevent the reentry of oxygen thus extinguishing combustion within the volume between the tank and the secondary containment.
ABSTRACT OF THE DISCLOSURE
A storage tank with secondary containment includes a cylindrical inner tank which is mounted within a rectangular secondary containment with a horizontal flat base and vertical upstanding walls. A portion of the inner tank projects above the side walls to allow access for filling etc..
The area between the top edge of the vertical side wall and the adjacent portion of the tank is covered by a respective one of a plurality of cover panels each of which includes a top edge which is wedged under a flange on the tank and extends therefrom downwardly and outwardly to a vertical flange bolted to the vertical side wall. The cover panel thus acts to shed rainwater and the like. The cover panels are provided with explosion vents each in the form of a duct extending upwardly from the cover panel so as to direct flames and explosion gases away from the top part of the inner tank. Each duct is covered by a flap member which can open under the pressure from the gases but closes under its weight to prevent the reentry of oxygen thus extinguishing combustion within the volume between the tank and the secondary containment.
Description
2~7~?9')9 STORAGE TANK WITH SECONDARY CONTAINMENT
FIELD OF THE INVENTION
This invention relates to a storage tank with secondary containment surrounding an inner tank element to provide collection of any liquids leaking from the inner tank element.
In recent years the seriousness of contamination which can occur in soil and in subsoil water has become realized and therefore steps have been taken to implement regulations requiring storage tanks to be protected by secondary containment to prevent such leakage into the soil.
Tanks for storing liquids are widely used for the storage of chemicals and particularly fuels. There is therefore at the present time a significant demand for storage tanks providing secondary containment in view of these increased environmental concerns and in view of more stringent regulations to prevent the leakage of such materials and contamination in the surrounding area. One example of a secondary containment tank includes a cylindrical inner tank element with the longitudinal axis of the inner tank mounted horizontally. Around the inner tank is provided a secondary containment element in the form of a horizontal rectangular base with up~tanding vertical side walls along each side of the base so as to form a hollow container within which the inner ~r1~s~
tank element sits. The side walls terminate at a position below the top of inner tank element so that the top is exposed and available for access for filling, venting and the like.
In some cases the surrounding wall of the secondary containment is simply open at the top so as to form simply a dike effect. Such an arrangement of course is open to collect water from rainfall and snow and other contaminants such as dust, garbage and the like. However the open top allows fumes from any leaking liquid to escape so there is little danger of explosion in the fumes. It is necessary however of course to clear out the collecting water and other materials on a regular basis and to provide techniques to prevent ice damage by any freezing of the water contained in the space between the tank and the outer side walls.
Other examples of a design of this type provide ~imply a horizontal cover panel extending from the side wall of the secondary containment to the adjacent edge of the tank.
~his cover ~ystem is relatively crude and ineffective and little thought has been given to its proper design and function.
In some arrangements the inner tank element and the secondary containment element are both mounted upon a horizontal skid arrangemen~ which allows the unit as a whole to be transported and stored as a single integral unit.
2~ 9 SUMMARY OF THE INVENTION
It is one object of the present invention, therefore, to provide an improved arrangement of storage tanks with secondary containment which includes a cover arrangement to prevent entry of water or other contaminants into the volume between the inner tank element and the secondary containment element.
According to a first aspect of the invention there is provided a storage tank comprising an inner tank element having a tank wall defining a closed hollow interior, an outer secondary confinement element including a base and surrounding upstanding side wall means within which the tank element is received such that any material leaking from the tank element can be trapped and retained in the secondary confinement element, a part of the tank element being exposed at a top of the secondary confinement element for filling and other access to the tank element, cover means extending from the upstanding side wall means to the tank element for preventing entry of rain and other materials therebetween such that a volume between the tank element and the secondary confinement element is subqtantially closed, and explosion vent means for releasing explosion gases from the volume, in the event of combustion of fumes or materials within the volume, to atmosphere surrounding the secondary confinement element, said 2~
explosion vent means including closure means arranged to be automatically closed after release of said explosion gases to inhibit entry of oxygen into the volume for extinguishing said combustion.
According to a second aspect of the invention there is provided a storage tank comprising an inner tank element having a tank wall defining a closed hollow interior, an outer secondary confinement element including a base and surrounding upstanding side wall means within which the tank element is received such that any material leaking from the tank element can be trapped and retained in the secondary confinement element, a part of the tank element being exposed at a top of the secondary confinement element for filling and other access to the tank element, and cover means extending from the upstanding side wall means to the tank element for preventing entry of rain and other materials therebetween, said cover means being inclined outwardly and downwardly from an inner edge in engagement with the tank element to an outer edge atached to said side wall means of said secondary confinement element so as to shed rain outwardly and downwardly to prevent entry into Yaid volume.
One or more embodiments of the invention will now be described in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
-2~'7~
Figure 1 is an isometric view of a storage tank with secondary containment according to the present invention.
Figure 2 is a top plan view of the storage tank of Figure 1.
Figure 3 is a cross sectional view along the lines 3-3 of Figure 2.
Figure 4 is a cross sectional view along the lines 4-4 of Figure 2.
Figure 5 is an isometric view showing in more detail one of the explosion vents of the container of Figure 1.
Figure 6 is a cross sectional view along the lines 6-6 of Figure 1.
In the drawings like characters of reference indicate corresponding parts in the different figures.
DETAILED DESCRIPTION
The storage tank is generally indicated at 10 and includes a cylindrical inner tank element 11 and an outer secondary containment element 12.
The inner tank element 11 comprises a cylindrical tank of circular cross section with a cylindrical peripheral wall 13 and end walls 14 and 15 lying at right angles to the axis of the cylindrical wall 13. The cylindrical tank is generally of conventional construction and is therefore not shown in detail but includes a conventional vent tube 16, a venting system 17 and a fill box 18 all of which are of conventional construction and therefore not described in detail. The lowerpart of the peripheral wall 13 is mounted upon suitable cradles 19 which support the cylindrical peripheral wall relative to a horizontal support surface so that the axis of the tank is maintained horizontal, the wall of the tank is supported and the tank is prevented from rolling from side to side. The tank further includes a discharge duct arrangement generally indicated at 20 which connects with a lower part of the end wall 15 of the tank and projects therefrom axially to a discharge end coupling 21 for discharge of the material.
The secondary containment element comprises a base 22 in the form of a rectangular flat horizontal sheet of metal. At the edges of the sheet of metal forming the base are welded side walls 23, 24, 25 and 26 which are arranged to stand vertically upwardly from the respective edge of the base with the side walls being welded each to the next mutually at right angles to form a hollow rectangular container into which the tank can be received. The hollow rectangular container is thus fully liquid proof to act as a dike or containment to prevent any liquid escaping from the tank from entering the soil around the tank or from spreading away from the tank. The secondary containment is only perforated by the discharge duct z ~t~ 9 arrangement 20 which is carefully welded to the end walls 24 of the secondary container 12 to prevent leakage at that point.
The height of the secondary container is such that the side walls terminate in an upper edge 27 with the upper edges lying in a common horizontal plane at a height approximately equal to the height of the axis of the inner tank element. The dimension of the base is arranged however so that the walls of the secondary container 12 are spaced away from the respective side wall or end wall of the tank by a distance such that the volume within the secondary container is at least 10% greater than the volume within the inner tank. Should any catastrophic leakage occur, therefore, the secondary container can receive all of the liquid within the inner tank with a ten percent over capacity for safety.
In order to render the whole unit transportable and storable as an integral unit, the base plate 22 is mounted upon a skid arrangement 28 formed by two parallel side I beams 29 and 30 which extend beyond the length of the base both forwardly and rearwardly beyond the end wall 26 and 24. The I
beams are interconnected by two or more transverse tubular members 31 and 32 arranged at the ends of the I beams 29 and 30. At each end of each of the I beams is provided an outstanding flange 34 to enable the skid to be grasped and transported.
~ ~7 ~J~ ~
Beyond the end wall 24, the I beams 29 and 30 project a greater distance than beyond the opposed end wall 26 in order to provide a platform section 35 which is covered by a grid material 36 to allow an operator to stand on the platform section. The platform section receives a pumping section 37 and if required an inspection step arrangement 38 both of which are of conventional construction and thus shown only schematically. These elements are omitted from Figure 1 for convenience of illustration.
The side walls 23 and 25 are supported in their vertical orientation by angle beams 39 and 40 which extend from an inside surface of the respective side wall downwardly and inwardly toward the base simply to act as stiffening members.
The exposed area at the top of the side walls of the secondary container between those top edges and the adjacent wall of the tank are covered by cover panels 41, 42, 43, and 44 each of which is arranged between a respective one of the side walls 23, 24, 25 and 26 and a respective wall of the tank element. One of the cover panels is shown in more detail in Figure 6 which is a cover panel 42 extending between the end wall 24 of the secondary container and the end wall 15 of the tank. The cover panel thus comprises an angled section 47 which extends outwardly and downwardly from a position in contact with the end wall 15 outwardly and downwardly to a g position at the top edge 27 of the side wall 24. At the outer edge of the inclined portion 47 is provided a downturned flange 48 which extends vertically downwardly on the outside surface of the side wall 24 and is attached thereto by a plurality of bolts 49. An upper edge 50 of the inclined portion 47 is received under a flange 51 welded onto the outside surface of the end wall 15. The flange is cantered outwardly and downwardly from the end wall 15 at the same angle as the inclined portion 47. In order to hold the edge 50 in place under the flange 51 is provided a plurality of wedge members 52 at spaced positions along the length of the flange 51. Each of the wedge members is of a short length for example a few inches and is triangular in shape so as to define an upper surface 53 generally parallel to the underside of the flange 51 but inclined slightly and angled thereto so as to act as a inwardly tapering receptacle into which the edge 50 can be inserted.
Each cover panel therefore is attached to the respective side wall and to the respective side of the tank by the arrangement thus described above and each panel terminates at a diagonal line extending outwardly from a corner of the inner tank element toward a respective corner of the outer containment element. These junctions between the cover panels are covered by corner members 54 which engage over the junctions between the flanges 51, over the seams between the 9~9 respective cover panels both over the inclined portion 47 thereof and including a downturned portion extending over the downturned flange 48 thereof.
The cover members thus provide effective shedding action for rain, snow and other contaminants to maintain the volume under the tank element fully clean. The cover members can however be readily removed simply by removing the bolt 49 and extracting the upper edge 50 from its receptacle. This may be necessary for inspection of the inner tank element to detect for example corrosion.
Each of the cover panels 41, 43 and 44 include an explosion vent 60 of the arrangement generally shown in Figure 5. The explosion vent 60 comprises a duct 61 which is welded at its lower end to the upper surface of the inclined portion 47 of the cover panel and extends substantially vertically upwardly therefrom with a slight outward inclination away from the upper part of the inner tank element. The duct 61 includes end walls 62 which taper inwardly toward an open mouth 63 of the duct spaced upwardly from the cover panel. The duct further includes side walls 64 which is generally rectangular in shape so as to maintain a constant width along the duct.
The height of the duct is arranged so that the open mouth 63 is below the top of the inner tank element but is spaced above the cover panel. The open mouth 63 is covered by a flap member 65 with a flat upper plate 66 and a pair of depending sides 67.
The sides 67 lie just outside and parallel to the side wall 62 of the duct and are connected thereto by hinge pins 68 which define a common hinge axis at a rear of the duct and at a rear of the flat plate 66.
The side plates 67 act as a counterweight tending to pull the flap member downwardly into horizontal position across the horizontal upper mouth 63. This acts as a closure for the horizontal upper mouth and prevents the entry of water and the like. The horizontal plate 66 can however pivot readily upwardly upon force upwardly from inside the volume between the inner tank element and the outer containment element to a maximum position shown in Figure 5 in which the flap member acts as an extension of the duct. From that position however it will be apparent that the flap member will simply fall under gravity back to the closed position once any force from inside the volume is expended.
In the normal position, therefore, the flap members 65 simply sit in the closed position on top of the explosion vents. Upon the occurance of an explosion within the volume between the inner tank element and the secondary containment element caused for example by explosion of fumes leaking from the tank element, the explosion occurs within the volume and the gases are released from the interior volume through the explosion vents. The number and size of the vents are selected so that the vents can take the necessary flow without damage to the cover panels, to the secondary containment walls or to the tank itself.
Once the gases from the explosion have vented, there tends to be a vacuum generated within the volume which would normally cause air to be drawn rapidly back into the volume to continue the explosion or fire resulting from the explo~ion. The flap Members however fall to the closed position to prevent the rapid influx of air and oxygen thus extinguishing immediately the fire or ignition due to the absence of oxygen within the volume. It is not necessary that the flap members act as an effective seal but that simply that they inhibit the rapid inflow of oxygen. Thus by the time oxygen is drawn gradually back into the volume, it is been found by experimentation that the further combustion or explosion is prevented.
In the embodiments shown the cover panel 42 does not include an explosion vent 60 but instead includes an in~pection hatch 70 of a conventional nature allowing inspection of the di~charge duct arrangement 20.
The cover panels thus provide an effective cover to prevent entry of material into the volume between the tank element and the secondary containment element in a manner which allows them to be readily applied and removed and in a manner which effectively sheds water or other contaminants from the surface. In addition the cover panels are protected against damage by the presence of the explosion vents. The shape of the explosion vent including the duct and the flap member is arranged to direct the flames and explosion gases upwardly and away from the top of the inner tank element. It has been found by experimentation that the flames and explosion gases can leap to a high distance away from the tank so that it is essential that the flames are directed away from the upper part of the tank to prevent the flames seriously heating the tank which could cause boiling of the contents and ignition or combustion of the whole of the contents at the inner tank.
Although shown in an arrangement including a horizontal cylindrical tank and a transportation skid, other arrangements of inner tank element and outer secondary containment elements can be provided which include the inclined cover panels and the explosion vent arrangements as set forth above.
Since various modifications can be made in my invention as hereinabove described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.
FIELD OF THE INVENTION
This invention relates to a storage tank with secondary containment surrounding an inner tank element to provide collection of any liquids leaking from the inner tank element.
In recent years the seriousness of contamination which can occur in soil and in subsoil water has become realized and therefore steps have been taken to implement regulations requiring storage tanks to be protected by secondary containment to prevent such leakage into the soil.
Tanks for storing liquids are widely used for the storage of chemicals and particularly fuels. There is therefore at the present time a significant demand for storage tanks providing secondary containment in view of these increased environmental concerns and in view of more stringent regulations to prevent the leakage of such materials and contamination in the surrounding area. One example of a secondary containment tank includes a cylindrical inner tank element with the longitudinal axis of the inner tank mounted horizontally. Around the inner tank is provided a secondary containment element in the form of a horizontal rectangular base with up~tanding vertical side walls along each side of the base so as to form a hollow container within which the inner ~r1~s~
tank element sits. The side walls terminate at a position below the top of inner tank element so that the top is exposed and available for access for filling, venting and the like.
In some cases the surrounding wall of the secondary containment is simply open at the top so as to form simply a dike effect. Such an arrangement of course is open to collect water from rainfall and snow and other contaminants such as dust, garbage and the like. However the open top allows fumes from any leaking liquid to escape so there is little danger of explosion in the fumes. It is necessary however of course to clear out the collecting water and other materials on a regular basis and to provide techniques to prevent ice damage by any freezing of the water contained in the space between the tank and the outer side walls.
Other examples of a design of this type provide ~imply a horizontal cover panel extending from the side wall of the secondary containment to the adjacent edge of the tank.
~his cover ~ystem is relatively crude and ineffective and little thought has been given to its proper design and function.
In some arrangements the inner tank element and the secondary containment element are both mounted upon a horizontal skid arrangemen~ which allows the unit as a whole to be transported and stored as a single integral unit.
2~ 9 SUMMARY OF THE INVENTION
It is one object of the present invention, therefore, to provide an improved arrangement of storage tanks with secondary containment which includes a cover arrangement to prevent entry of water or other contaminants into the volume between the inner tank element and the secondary containment element.
According to a first aspect of the invention there is provided a storage tank comprising an inner tank element having a tank wall defining a closed hollow interior, an outer secondary confinement element including a base and surrounding upstanding side wall means within which the tank element is received such that any material leaking from the tank element can be trapped and retained in the secondary confinement element, a part of the tank element being exposed at a top of the secondary confinement element for filling and other access to the tank element, cover means extending from the upstanding side wall means to the tank element for preventing entry of rain and other materials therebetween such that a volume between the tank element and the secondary confinement element is subqtantially closed, and explosion vent means for releasing explosion gases from the volume, in the event of combustion of fumes or materials within the volume, to atmosphere surrounding the secondary confinement element, said 2~
explosion vent means including closure means arranged to be automatically closed after release of said explosion gases to inhibit entry of oxygen into the volume for extinguishing said combustion.
According to a second aspect of the invention there is provided a storage tank comprising an inner tank element having a tank wall defining a closed hollow interior, an outer secondary confinement element including a base and surrounding upstanding side wall means within which the tank element is received such that any material leaking from the tank element can be trapped and retained in the secondary confinement element, a part of the tank element being exposed at a top of the secondary confinement element for filling and other access to the tank element, and cover means extending from the upstanding side wall means to the tank element for preventing entry of rain and other materials therebetween, said cover means being inclined outwardly and downwardly from an inner edge in engagement with the tank element to an outer edge atached to said side wall means of said secondary confinement element so as to shed rain outwardly and downwardly to prevent entry into Yaid volume.
One or more embodiments of the invention will now be described in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
-2~'7~
Figure 1 is an isometric view of a storage tank with secondary containment according to the present invention.
Figure 2 is a top plan view of the storage tank of Figure 1.
Figure 3 is a cross sectional view along the lines 3-3 of Figure 2.
Figure 4 is a cross sectional view along the lines 4-4 of Figure 2.
Figure 5 is an isometric view showing in more detail one of the explosion vents of the container of Figure 1.
Figure 6 is a cross sectional view along the lines 6-6 of Figure 1.
In the drawings like characters of reference indicate corresponding parts in the different figures.
DETAILED DESCRIPTION
The storage tank is generally indicated at 10 and includes a cylindrical inner tank element 11 and an outer secondary containment element 12.
The inner tank element 11 comprises a cylindrical tank of circular cross section with a cylindrical peripheral wall 13 and end walls 14 and 15 lying at right angles to the axis of the cylindrical wall 13. The cylindrical tank is generally of conventional construction and is therefore not shown in detail but includes a conventional vent tube 16, a venting system 17 and a fill box 18 all of which are of conventional construction and therefore not described in detail. The lowerpart of the peripheral wall 13 is mounted upon suitable cradles 19 which support the cylindrical peripheral wall relative to a horizontal support surface so that the axis of the tank is maintained horizontal, the wall of the tank is supported and the tank is prevented from rolling from side to side. The tank further includes a discharge duct arrangement generally indicated at 20 which connects with a lower part of the end wall 15 of the tank and projects therefrom axially to a discharge end coupling 21 for discharge of the material.
The secondary containment element comprises a base 22 in the form of a rectangular flat horizontal sheet of metal. At the edges of the sheet of metal forming the base are welded side walls 23, 24, 25 and 26 which are arranged to stand vertically upwardly from the respective edge of the base with the side walls being welded each to the next mutually at right angles to form a hollow rectangular container into which the tank can be received. The hollow rectangular container is thus fully liquid proof to act as a dike or containment to prevent any liquid escaping from the tank from entering the soil around the tank or from spreading away from the tank. The secondary containment is only perforated by the discharge duct z ~t~ 9 arrangement 20 which is carefully welded to the end walls 24 of the secondary container 12 to prevent leakage at that point.
The height of the secondary container is such that the side walls terminate in an upper edge 27 with the upper edges lying in a common horizontal plane at a height approximately equal to the height of the axis of the inner tank element. The dimension of the base is arranged however so that the walls of the secondary container 12 are spaced away from the respective side wall or end wall of the tank by a distance such that the volume within the secondary container is at least 10% greater than the volume within the inner tank. Should any catastrophic leakage occur, therefore, the secondary container can receive all of the liquid within the inner tank with a ten percent over capacity for safety.
In order to render the whole unit transportable and storable as an integral unit, the base plate 22 is mounted upon a skid arrangement 28 formed by two parallel side I beams 29 and 30 which extend beyond the length of the base both forwardly and rearwardly beyond the end wall 26 and 24. The I
beams are interconnected by two or more transverse tubular members 31 and 32 arranged at the ends of the I beams 29 and 30. At each end of each of the I beams is provided an outstanding flange 34 to enable the skid to be grasped and transported.
~ ~7 ~J~ ~
Beyond the end wall 24, the I beams 29 and 30 project a greater distance than beyond the opposed end wall 26 in order to provide a platform section 35 which is covered by a grid material 36 to allow an operator to stand on the platform section. The platform section receives a pumping section 37 and if required an inspection step arrangement 38 both of which are of conventional construction and thus shown only schematically. These elements are omitted from Figure 1 for convenience of illustration.
The side walls 23 and 25 are supported in their vertical orientation by angle beams 39 and 40 which extend from an inside surface of the respective side wall downwardly and inwardly toward the base simply to act as stiffening members.
The exposed area at the top of the side walls of the secondary container between those top edges and the adjacent wall of the tank are covered by cover panels 41, 42, 43, and 44 each of which is arranged between a respective one of the side walls 23, 24, 25 and 26 and a respective wall of the tank element. One of the cover panels is shown in more detail in Figure 6 which is a cover panel 42 extending between the end wall 24 of the secondary container and the end wall 15 of the tank. The cover panel thus comprises an angled section 47 which extends outwardly and downwardly from a position in contact with the end wall 15 outwardly and downwardly to a g position at the top edge 27 of the side wall 24. At the outer edge of the inclined portion 47 is provided a downturned flange 48 which extends vertically downwardly on the outside surface of the side wall 24 and is attached thereto by a plurality of bolts 49. An upper edge 50 of the inclined portion 47 is received under a flange 51 welded onto the outside surface of the end wall 15. The flange is cantered outwardly and downwardly from the end wall 15 at the same angle as the inclined portion 47. In order to hold the edge 50 in place under the flange 51 is provided a plurality of wedge members 52 at spaced positions along the length of the flange 51. Each of the wedge members is of a short length for example a few inches and is triangular in shape so as to define an upper surface 53 generally parallel to the underside of the flange 51 but inclined slightly and angled thereto so as to act as a inwardly tapering receptacle into which the edge 50 can be inserted.
Each cover panel therefore is attached to the respective side wall and to the respective side of the tank by the arrangement thus described above and each panel terminates at a diagonal line extending outwardly from a corner of the inner tank element toward a respective corner of the outer containment element. These junctions between the cover panels are covered by corner members 54 which engage over the junctions between the flanges 51, over the seams between the 9~9 respective cover panels both over the inclined portion 47 thereof and including a downturned portion extending over the downturned flange 48 thereof.
The cover members thus provide effective shedding action for rain, snow and other contaminants to maintain the volume under the tank element fully clean. The cover members can however be readily removed simply by removing the bolt 49 and extracting the upper edge 50 from its receptacle. This may be necessary for inspection of the inner tank element to detect for example corrosion.
Each of the cover panels 41, 43 and 44 include an explosion vent 60 of the arrangement generally shown in Figure 5. The explosion vent 60 comprises a duct 61 which is welded at its lower end to the upper surface of the inclined portion 47 of the cover panel and extends substantially vertically upwardly therefrom with a slight outward inclination away from the upper part of the inner tank element. The duct 61 includes end walls 62 which taper inwardly toward an open mouth 63 of the duct spaced upwardly from the cover panel. The duct further includes side walls 64 which is generally rectangular in shape so as to maintain a constant width along the duct.
The height of the duct is arranged so that the open mouth 63 is below the top of the inner tank element but is spaced above the cover panel. The open mouth 63 is covered by a flap member 65 with a flat upper plate 66 and a pair of depending sides 67.
The sides 67 lie just outside and parallel to the side wall 62 of the duct and are connected thereto by hinge pins 68 which define a common hinge axis at a rear of the duct and at a rear of the flat plate 66.
The side plates 67 act as a counterweight tending to pull the flap member downwardly into horizontal position across the horizontal upper mouth 63. This acts as a closure for the horizontal upper mouth and prevents the entry of water and the like. The horizontal plate 66 can however pivot readily upwardly upon force upwardly from inside the volume between the inner tank element and the outer containment element to a maximum position shown in Figure 5 in which the flap member acts as an extension of the duct. From that position however it will be apparent that the flap member will simply fall under gravity back to the closed position once any force from inside the volume is expended.
In the normal position, therefore, the flap members 65 simply sit in the closed position on top of the explosion vents. Upon the occurance of an explosion within the volume between the inner tank element and the secondary containment element caused for example by explosion of fumes leaking from the tank element, the explosion occurs within the volume and the gases are released from the interior volume through the explosion vents. The number and size of the vents are selected so that the vents can take the necessary flow without damage to the cover panels, to the secondary containment walls or to the tank itself.
Once the gases from the explosion have vented, there tends to be a vacuum generated within the volume which would normally cause air to be drawn rapidly back into the volume to continue the explosion or fire resulting from the explo~ion. The flap Members however fall to the closed position to prevent the rapid influx of air and oxygen thus extinguishing immediately the fire or ignition due to the absence of oxygen within the volume. It is not necessary that the flap members act as an effective seal but that simply that they inhibit the rapid inflow of oxygen. Thus by the time oxygen is drawn gradually back into the volume, it is been found by experimentation that the further combustion or explosion is prevented.
In the embodiments shown the cover panel 42 does not include an explosion vent 60 but instead includes an in~pection hatch 70 of a conventional nature allowing inspection of the di~charge duct arrangement 20.
The cover panels thus provide an effective cover to prevent entry of material into the volume between the tank element and the secondary containment element in a manner which allows them to be readily applied and removed and in a manner which effectively sheds water or other contaminants from the surface. In addition the cover panels are protected against damage by the presence of the explosion vents. The shape of the explosion vent including the duct and the flap member is arranged to direct the flames and explosion gases upwardly and away from the top of the inner tank element. It has been found by experimentation that the flames and explosion gases can leap to a high distance away from the tank so that it is essential that the flames are directed away from the upper part of the tank to prevent the flames seriously heating the tank which could cause boiling of the contents and ignition or combustion of the whole of the contents at the inner tank.
Although shown in an arrangement including a horizontal cylindrical tank and a transportation skid, other arrangements of inner tank element and outer secondary containment elements can be provided which include the inclined cover panels and the explosion vent arrangements as set forth above.
Since various modifications can be made in my invention as hereinabove described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.
Claims (21)
1. A storage tank comprising an inner tank element having a tank wall defining a closed hollow interior, an outer secondary confinement element including a base and surrounding upstanding side wall means within which the tank element is received such that any material leaking from the tank element can be trapped and retained in the secondary confinement element, a part of the tank element being exposed at a top of the secondary confinement element for filling and other access to the tank element, cover means extending from the upstanding side wall means to the tank element for preventing entry of rain and other materials therebetween such that a volume between the tank element and the secondary confinement element is substantially closed, and explosion vent means for releasing explosion gases from the volume, in the event of combustion of fumes or materials within the volume, to atmosphere surrounding the secondary confinement element, said explosion vent means including closure means arranged to be automatically closed after release of said explosion gases to inhibit entry of oxygen into the volume for extinguishing said combustion.
2. The storage tank according to Claim 1 wherein the closure means comprises flap means normally closing said vent means, said flap means being movable under pressure from said explosion gases for opening said vent means and automatically closable when pressure from said explosion gases is released.
3. The storage tank according to Claim 1 wherein the vent means is arranged to direct flames and explosion gases from the combustion in a direction away from the inner tank.
4. The storage tank according to Claim 2 wherein the flap means comprises a hinged flap member pivotal about a hinge axis at one side of a vent opening and including means allowing movement of the flap member to an open position in which the weight of the flap member tends to move the flap member to a closed position.
5. The storage tank according to Claim 3 wherein the explosion vent means includes a duct member mounted on said cover means at an opening therein and extending upwardly therefrom to an open mouth spaced upwardly of the cover means.
6. The storage tank according to Claim 5 wherein the closure means comprises a hinged flap member mounted on the duct member of the open mouth and pivotal about a hinge axis at one side of the open mouth and including means allowing movement of the flap member to an open position, under pressure from the explosion gases, in which position the weight of the flap member tends to move the flap member to a closed position.
7. The storage tank according to Claim 1 wherein the explosion vent means comprises a plurality of vent openings arranged at spaced positions around the inner tank.
8. The storage tank according to Claim 1 wherein said cover means is inclined outwardly and downwardly from an inner edge in engagement with the tank element to an outer edge atached to said side wall means of said secondary confinement element so as to shed rain outwardly and downwardly to prevent entry into said volume.
9. The storage tank according to Claim 8 wherein the cover means comprises a plurality of removable cover panels .
10. The storage tank according to Claim 9 wherein the tank element includes a flange member attached thereto and extending outwardly and downwardly therefrom and wherein the inner edge of the cover means is separate from the tank element and is engaged under the flange member.
11. The storage tank according to Claim 10 including wedge means mounted on the tank element underneath the flange member and arranged to define a slot therebetween for receiving the inner edge of the cover means.
12. The storage tank according to Claim 8 wherein the cover means includes a vertical flange at the outer edge thereof extending vertically downwardly on an outer side of the side wall means and attached to the side wall means.
13. The storage tank according to any one of Claims 1 to 12 wherein the tank element comprises a cylindrical tank with an axis of the cylindrical tank arranged horizontal and including vertical end walls of the cylindrical tank and wherein the secondary confinement element includes a rectangular base with four upstanding side walls arranged mutually at right angles each side wall being spaced from an adjacent portion of the tank element, an upper edge of each of the side walls lying at a height below an upper most part of the inner tank.
14. The storage tank according to any one of Claims 1 to 12 wherein the tank element comprises a cylindrical tank with an axis of the cylindrical tank arranged horizontal and including vertical end walls of the cylindrical tank and wherein the secondary confinement element includes a rectangular base with four upstanding side walls arranged mutually at right angles each side wall being spaced from an adjacent portion of the tank element, an upper edge of each of the side walls lying at a height below an upper most part of the inner tank, the secondary confinement element is mounted on a horizontal planar skid member for support thereof during standing and during transportation.
15. A storage tank comprising an inner tank element having a tank wall defining a closed hollow interior, an outer secondary confinement element including a base and surrounding upstanding side wall means within which the tank element is received such that any material leaking from the tank element can be trapped and retained in the secondary confinement element, a part of the tank element being exposed at a top of the secondary confinement element for filling and other access to the tank element, and cover means extending from the upstanding side wall means to the tank element for preventing entry of rain and other materials therebetween, said cover means being inclined outwardly and downwardly from an inner edge in engagement with the tank element to an outer edge atached to said side wall means of said secondary confinement element so as to shed rain outwardly and downwardly to prevent entry into said volume.
16. The storage tank according to Claim 15 wherein the cover means comprises a plurality of removable cover panels.
17. The storage tank according to Claim 16 wherein the tank element includes a flange member attached thereto and extending outwardly and downwardly therefrom and wherein the inner edge of the cover means is separate from the tank element and is engaged under the flange member.
18. The storage tank according to Claim 17 including wedge means mounted on the tank element underneath the flange member and arranged to define a slot therebetween for receiving the inner edge of the cover means.
19. The storage tank according to any one of Claims 15 to 18 wherein the cover means includes a vertical flange at the outer edge thereof extending vertically downwardly on an outer side of the side wall means and attached to the side wall means.
20. The storage tank according to any one of Claims 15 to 18 wherein the tank element comprises a cylindrical tank with an axis of the cylindrical tank arranged horizontal and including vertical end walls of the cylindrical tank and wherein the secondary confinement element includes a rectangular base with four upstanding side walls arranged mutually at right angles each side wall being spaced from an adjacent portion of the tank element, an upper edge of each of the side walls lying at a height below an upper most part of the inner tank.
21. The storage tank according to any one of Claims 15 to 18 wherein the tank element comprises a cylindrical tank with an axis of the cylindrical tank arranged horizontal and including vertical end walls of the cylindrical tank and wherein the secondary confinement element includes a rectangular base with four upstanding side walls arranged mutually at right angles each side wall being spaced from an adjacent portion of the tank element, an upper edge of each of the side walls lying at a height below an upper most part of the inner tank, wherein the secondary confinement element is mounted on a horizontal planar skid member for support thereof during standing and during transportation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2070939 CA2070939A1 (en) | 1992-06-10 | 1992-06-10 | Storage tank with secondary containment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2070939 CA2070939A1 (en) | 1992-06-10 | 1992-06-10 | Storage tank with secondary containment |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2070939A1 true CA2070939A1 (en) | 1993-12-11 |
Family
ID=4150001
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2070939 Abandoned CA2070939A1 (en) | 1992-06-10 | 1992-06-10 | Storage tank with secondary containment |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2070939A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5555999A (en) * | 1995-06-28 | 1996-09-17 | Wilcox; Stephen H. | Secondary containment for aboveground flammable and combustible liquid storage tanks |
| WO2014183189A1 (en) * | 2013-05-16 | 2014-11-20 | Gregory Whittaker | Expandable holding tank |
| CN107950463A (en) * | 2017-12-13 | 2018-04-24 | 贵州省黑冲生态农业发展有限公司 | The long-distance transport fish box of fishery cultivating |
-
1992
- 1992-06-10 CA CA 2070939 patent/CA2070939A1/en not_active Abandoned
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5555999A (en) * | 1995-06-28 | 1996-09-17 | Wilcox; Stephen H. | Secondary containment for aboveground flammable and combustible liquid storage tanks |
| WO1997001499A1 (en) * | 1995-06-28 | 1997-01-16 | Spectra Environmental Ltd. | Secondary containment for above-ground flammable and combustible liquid storage tanks |
| WO2014183189A1 (en) * | 2013-05-16 | 2014-11-20 | Gregory Whittaker | Expandable holding tank |
| US20160130077A1 (en) * | 2013-05-16 | 2016-05-12 | Gregory Whittaker | Expandable holding tank |
| US9969547B2 (en) * | 2013-05-16 | 2018-05-15 | Gregory A. WHITTAKER | Expandable holding tank |
| CN107950463A (en) * | 2017-12-13 | 2018-04-24 | 贵州省黑冲生态农业发展有限公司 | The long-distance transport fish box of fishery cultivating |
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Legal Events
| Date | Code | Title | Description |
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| FZDE | Dead |