US20030042256A1

US20030042256A1 - Floating cover

Info

Publication number: US20030042256A1
Application number: US09/945,783
Authority: US
Inventors: Burton Johnson; William Wagner
Original assignee: Petrex Inc
Current assignee: Petrex Inc
Priority date: 2001-09-05
Filing date: 2001-09-05
Publication date: 2003-03-06

Abstract

A floating cover having a plurality of floating panels is provided. The floating panels are assembled to form the floating cover disposed in a storage tank. The floating panels are provided with extruded channels formed on each peripheral outside of a honeycomb. A trough or hollow inside is formed within the extruded channels. An inspection port is formed on the extruded channels to provide a user with an inspection for leakage without disassembling the floating cover and without taking out the floating cover from the storage tank. The inspection port provides the inspection of presence of moisture and condensate trapped in the inside of each of the floating panels and also provides the replacement of damaged or degraded one among the floating panels.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a floating cover for a liquid storage tank, and more particularly, to a liquid surface contact internal floating cover constructed with a plurality of floating panels and process of monitoring potential leaks within each of the floating panels.

2. Description of the Background Art

Floating covers have previously been used inside cylindrical liquid storage tanks to ride vertically along the cylindrical wall of the tanks between the roof and bottom as the volume of fluid held by the tank varies. Typically, the floating cover floats over the liquid and moves up and down depending on the amount of the liquid held by the tank. In conventional practice, a floating cover may be constructed with a plurality of buoyant panels, such as honeycomb type pans, that are assembled and fastened together. Moreover, periodic inspection and maintenance of the cover is desirable in order to obtain the full life of the cover.

Current design practice for floating panels uses a honeycomb panel that is manufactured by bonding an aluminum channel frame to the honeycomb panel with polysulfide adhesive or, depending upon the product to be stored within the tank, various other epoxy adhesives. During the fabrication process, all cells including those around the edge of the panel are sealed closed and consequently each is isolated from its neighbor. If this fabrication deteriorates over time and some of the edge cells become open to invasion by vapor or the product held by the tank, there is currently no way of detecting the invasion except by looking for the invading product as it drips back out of the panel after the tank has been taken out of service, emptied and an inspector visually examines the underside of each panel. Otherwise, the trapped liquid will slowly drip out of the panel and present a safety hazard to the maintenance people working within the interior of the tank.

By way of explanation, the owners and managers of tanks must periodically inspect the interior of the tank and make repairs. This entails a removal of the contents of the tank, a purging of gaseous phase vapor from the interior of the tank, an introduction of ambient atmospheric air into the interior of the tank and continuous or at least intermittent monitoring of the atmosphere within the interior of the tank. The owner of the tank needs assurance that before personnel enter the interior of the empty tank, and that while work (particularly using arc or open flame torches) is performed within the interior of the tank, that the tank has been completely emptied and cleaned, and is safe for both the personnel and the type of work being performed. This assurance requires that there be no remaining pockets of the hazardous contents of the tank within the floating roof.

Some manufacturers have chosen to use honey comb with perforated core, which would allow for the monitoring of vapors from any single leak found anywhere within a panel. This benefit has been attained at the cost of opening the panel up to complete flooding, and thus complete loss of its buoyancy, from a single leak. Also, there would be the loss of the repair features which are a part of this invention.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved floating roof.

It is another object to provide a floating roof and process for detecting the presence of vapor, moisture, or condensate which indicates leakage and the onset of deterioration of the integrity of the roof.

It is yet another object to provide a floating roof assembled from multiple panels and a process for inspecting individual panels for the onset of deterioration.

It is still another object to provide a floating cover able to remove and replace individual floating panels of the floating cover without interfering with the integrity of adjacent floating panels.

It is still yet another object to provide a floating cover that permits inspection of leakage of each of the floating panels forming the floating cover without disassembly of the entirety of the floating cover.

It is still yet another object to provide a full liquid surface contact internal floating cover constructed with individual floating panels that may be checked for leakage from the top side of the floating cover while the tank is in service.

It is a further object to provide a full liquid surface contact internal floating cover that accommodates visual inspection of the interior perimeter of the floatation panels.

It is a still yet further object to provide a full liquid surface contact internal floating cover assembled from a plurality of floatation panels, with adjacent panels allowing unrestricted removal of individual floatation panels.

It is also an object to provide a full liquid surface contact internal floating cover constructed from a plurality of floatation panels that may be leak tested at the point of manufacture as well as in the field after assembly of the floating cover.

It is also object to provide a floating cover that allows individual panels within the floating cover to be inspected from above the floating cover.

These and other objects may be achieved by providing a storage tank with a floating cover including individual panels constructed with an aluminum honeycomb internal structure containing multiple seated cells that is sandwiched between upper and lower sheet metal cladding and that is coupled to a frame that is fitted around the periphery of the central honeycomb structure. An extruded channel is formed on each exterior side of the panel. Upper and lower flanges of the frame fit over the respective upper and lower planar surfaces of the honeycomb structure, and the junctions between the flanges and the periphery of the honeycomb structure is closed with a sealant. A lateral separation between the peripheral end wall of the honeycomb structure and the web, or sidewall, of the frame creates a trough along the inside surface of the lower flange, adjacent to, but beneath the lower sheet metal cladding of the honeycomb structure. If the sealant should deteriorate, the inside surface of the lower flange and the overlying undersurface of the lower sheet metal cladding that is otherwise plugged by the sealant, channels the product held by the storage tank seeking to leak into the panel to first occupy the trough. A plurality of inspection ports that are formed, allow visual inspection of the interior of each panel for such leakage. A detection monitor may be inserted into the interior of the each panel through the inspection port to detect the presence of product vapor, moisture, or condensate within the panel. A plug may be inserted into the respective inspection port in order to prevent any foreign material from being introduced into the interior of the panel through the inspection panel. A metal tape may be placed ever the inspection port to sealed off the panel.

Since this construction facilitates repair of the panels found to be defective, repair may be easily accomplished by one of three techniques without removal from the roof of a panel found to be defective. If the panel provides a very slight indication that vapor that has escaped from the product held by the tank is present in the interior of the panel, the trough may be filled with water in order to seal off any further escape of vapor from the interior of the tank. Later, the water may be removed when freezing atmospheric conditions occur. This is only a temporary remedy, however, and is not a repair of the panel. Secondly, a hole may be drilled into the bottom of the extrusion, the liquid phase fluid drained from the panel and the panel flushed with water, and the hole may be plugged with a rivet. The interior of the trough may be air dried and a liquid type polysulfide cement may be pored into the trough to a level of approximately ⅜ of an inch deep. Thirdly, the entire panel may be disassembled and removed from the floating cover, and replaced with a new panel.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of this invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: [0020]
FIG. 1 is a plan view of a floating panel constructed according to the principles of the present invention; [0021]
FIG. 2A is a cross-sectional view taken along [0022] line 2A-2A' of FIG. 1;
FIG. 2B is a cross-sectional view taken along line [0023] 2B-2B' of FIG. 1;
FIG. 3 is a partial perspective view showing an inspection port through which the presence of moisture and condensate soaked through a damaged sealant and trough can be inspected; [0024]
FIGS. 4A, 4B, [0025] 4C and 4D show second embodiments of an upper frame, a lower frame, and a floating panel, respectively, constructed according to the principles of the present invention; and
FIG. 5 is a partial cross-sectional view showing two floating panels assembled by a pair of clamping bars.[0026]

DETAILED DESCRIPTION OF THE INVENTION

Turning now to the drawings, FIG. 1 shows a [0027] floating panel 100 assembled to form a floating cover floating on a fluid contained in a tank and moving up and down in dependence upon the amount of the fluid of the tank. Floating panel 100 is provided with a honeycomb insert 110 and extruded channels 200 formed on peripheral portions of honeycomb insert 110. An inspection port 300 is formed on respective extruded channels 200. Two or three inspection ports 300 may be formed on extruded channels 200 depending on the length and the shape of extruded channels 200. With the existence of inspection port 300, a floating cover using honeycomb panels for floatation may be inspected at the convenience of tank owners and users whenever they desire to test floating panels within the storage tank for the presence of vapor, moisture, or condensate indicating a leak in floating panel 100. The tank does not need to be taken out of service and the floating cover does not need to be removed from the storage tank.
[0028] Extruded channel 200, as shown in FIGS. 2A and 2B, includes a lower frame 210, an upper frame 220, and honeycomb insert 110 inserted between upper frame 220 and lower frames 210. Lower frame 210 defines a side wall 212, a lower extension 211 extending horizontally from a lower end of side wall 212, a lower detent 215 formed on a upper end of side wall 212, an upright extension 213A extending from lower detent 215, and a groove 214 formed between lower detent 215 and upright extension 213A.
[0029] Upper frame 220 defines an upper extension 223A, a protrusion 224 formed on upper extension 211, and an upright extension 223A extended from protrusion 224 and disposed adjacent to upright extension 213A of lower frame to be coupled to upright extension 213A of lower frame 210 by a plurality of couplers 258 while protrusion 214 of upper frame 220 is inserted into groove 214 of lower frame 210. Upper extension 213A of upper frame 220 is spaced-apart from lower extension 211 of lower frame 210 by side wall 212 or a predetermined height to receive a peripheral outer portion of honeycomb 110. Lower frame 210 and upper frame 220 are integrally made of a single body in a monolithic structure.
Since the fluid level L of the product contained in the tank is higher than [0030] lower extension 211 of lower frame 210, floating panel 100 may be permeated with the fluid through a gap formed between honeycomb 200 and lower and upper frames 210, 220 and through a crevice of lower frame 210 and upper frame 220.
[0031] Honeycomb panel 110 is manufactured by bonding an aluminum sheet or “skin” upper plate 140A and an aluminum sheet or “skin” lower plate 140B to the honeycomb structure 130 with, depending on the product, various polysulfide or epoxy adhesives. In a fabricating process, every cell about the edge of the panel is sealed off and therefore isolated from its neighbor. If some of cells are later opened to invasion by the product, there is no way of detecting the presence of the product within the panel except by observation of the product dripping out of the panels after the tank has been taken out of service. The trapped liquid will then slowly drip out from the panel and present a severe safety hazard to maintenance people working within the tank; this makes it very inconvenient for the owners and users to inspect and fix the panel.
Referring now correctively to FIGS. 1, 2A, [0032] 2B and 3, honeycomb core 130 is disposed between upper plate 140A and lower plate 140B to form honeycomb panel 110 which is disposed between lower extension 211 of lower frame 210 and upper extension 221 of upper frame 220, and is coupled to lower extension 211 and upper extension 221 by through fasteners 251. Various types of couplers may be used for coupling honeycomb panel 110 and lower and upper frame 210, 220. A sealant 150, such as a rubber material, is disposed between lower extension 211 and lower plate 140B and between upper extension 221 and upper plate 140A in order to seal closed floating panel 100 and make the panel secure against leakage between honeycomb panel 110 and lower and upper frames 210, 220.
A trough or [0033] space 400 is formed between side wall 212 of lower frame 210 and the peripheral outer portion of honeycomb insert 110 and between lower extension 211 and upper extension 221. Trough 400 is surrounded by the peripheral outer portion of honeycomb insert 110, upper and lower plates 140A, 140B of honeycomb insert 110, a side surface 260 of side wall 212 of lower frame 210, a bottom surface, or floor, 270 of lower extension 211 of lower frame 210, upper extension 221 of upper frame 220, and inspection port 300. The floor 270 of trough 400 is lower than the interior surface of lower plate 140B by a distance D as shown in FIG. 4D. Consequently, upon deterioration of sealant 150, condensate or liquid phase leakage of the product into panel 100 via a leakage through the channel formed between the underside of lower plate 140B and the upper side of the lower flange, or extension 211 of frame 210, will accumulate first along floor 270, which runs beneath one or more inspection ports 300. Inspection port 300 is formed on upper extension 221 of upper frame 220 and permits direct visual examination of floor 270 within trough 400, which is hollow inside of floating panel 100. Trough 400 communicates with an outside of floating panel 100 through inspection port 300. A plug 310 which is used to seal the inspection ports, is removably inserted into corresponding inspection ports 300 as shown in FIG. 2A while an adhesive metal tape 320, used as a sealant is detachably attached around inspection port 300 as shown in FIG. 2B.
As shown by FIG. 3, [0034] trough 400 is visible from the outside of floating panel 100 through inspection port 300. Since each bottom of floating panels 100 of the floating cover is lower than the fluid level L of the product within the tank, vapor, moisture or condensate may be present in trough 400, having entered through damaged sealant 150 and the crevice of floating panels 100, and initially accumulated along floor 270. An inspection port 300 formed on each of floating panels 100 allows maintenance workers to inspect each of floating panels 100 for leakage from above, without disassembly of any of floating panels 100 from the floating cover. Any one of the peripheral outer portion of honeycomb insert 110, side surface 260 of side wall 212 of lower frame 210, bottom surface 270 of lower extension 211 of lower frame 210 can be seen through one of the individual inspection ports 300.
[0035] Individual inspection port 300 is formed on a predetermined position on upper extension 221 of upper frame 220 in order to provide a passageway through which an inspection tool, such as a monitor, may be inserted into trough 400 of floating panel 100 through inspection port 300. Each individual inspection port 300 may be formed on a central portion or a corner portion of extruded channels 200 of floating panel 100 depending on a user's selection or the inspection tool. Also, inspection port 300 is disposed to allow for visual inspection of the hollow inside of trough 400. A plurality of inspection ports may be formed on extruded channel 200 in order to provide the user with the full inspection of the entire hollow inside of trough 400 of floating panel 100.
Since a lower portion of floating [0036] panel 100 is lower than liquid level L, both the liquid product and vapor from the product tend to seep into floating panel 100 through a damaged seal or a crack formed on panel 500. Moreover, if the seam of any of floating panels 100 of the floating cover is broken, or if the seal of sealant 150 is loosened or degrades to the point where liquid can pass through, the liquid will then be trapped within the panel and will settle in along floor 270 of trough 400 and at the edge of sealant 150. Therefore, whenever vapor, moisture, and condensate are present inside trough 400 within the floating panel, the presence of the vapor, moisture and condensate can be detected through inspection port 300. Inspection port 300 allows rapid detection of the trapped liquid in the trough, and the leaking area of floating panels 100 may be corrected by one of the following processes.
If there is a very slight indication that liquid, such as gasoline is present, [0037] trough 400 can be filled with water to seal off any further escape of vapor. Later the water should be removed if freezing conditions could be occur. This process, however, is only a temporary fix and not repair. A second process is to drill hole into bottom extrusion, drain the trapped product from the panel, flush the panel with water, plug hole with a rivet and air-dry the trough, and then pour a liquid type polysulfide cement or epoxy into the trough to a predetermined level, such as ⅜″ deep. As a final process, only the damaged or degraded floating panel is removed from the floating cover or roof and replaced with a new floating panel.
With [0038] inspection port 300 formed on floating panel 100, it is possible for the owners or users to inspect the interior of each panel for the presence of vapor, moisture, and condensate trapped in trough 400 of floating panel 100 from above without removing the entire floating cover or roof from the storage tank.
FIGS. 4A, 4B, [0039] 4C, and 4D show a second embodiment of lower frame 210 and upper frame 220. Serrated surfaces 228 for adhesive 251 and sealant 150 are formed on each inside surface of lower and upper extensions 211, 221. An upper rib 225 and upper detent 226 are formed on a distal end of upright extension 223B of upper frame 220 opposite to protrusion 224 of upper frame 220. The distal end of upright extension 213B is inserted into an upper groove 224 while protrusion 224 of upper frame 220 is inserted into lower groove 214 of lower frame 210, and upper detent 224 holds a distal end of upright extension 213B of lower frame 210 when lower frame 210 is mated with upper frame 220.
FIG. 4C shows the second embodiment of assembled floating [0040] panel 100. After adhesive 150 is applied to serrated surfaces 218 and 228 of respective lower and upper extensions 211, 221 of upper and lower frame 210, 220, sealant 150 is disposed between lower plate 140B and serrated surface 218 of lower extension 211 and between upper plate 140A and serrated surface 228 of upper extension 221. Lower frame 210 and upper frame 220 provided with serrated surfaces 218, 228, respectively, are integrally assembled into a single body in a monolithic structure.
FIG. 5 shows the assembly of adjacent floating [0041] panels 100 to form the floating cover. A first clamping bar 510 is provided with a pair of first clamping grooves 511 that are parallel to each other and receiving upper ribs 225 of upper frames 220 of adjacent floating panels 100. A pair of second clamping grooves 521 are formed on a second clamping bar 520 that are parallel to each other and receive lower ribs 217 of lower frames 210 of adjacent floating panels. A stud 550 is inserted into holes formed on first clamping bar 510 and second clamping bar 520, and is coupled to a threaded portion of second clamping bar 520.
Since floating [0042] panels 100 and clamping bars 510, 520 are separately manufactured in a factory or in different factories located in different locations and are assembled into floating cover 100 inside the storage tank, each floating panel 100 may be individually inspected in the factory and also individually inspected before and after floating panels 100 are assembled. Each inspection of floating panels 100 both at the factory and at the site of the storage tank, that is, both before and after the assembly of the floating cover, is available for the user and manufacturer.
As mentioned above, the floating cover or roof is provided with a plurality of floating panels each having an upper exterior surface provided with one or more inspection ports. With these inspection ports, damaged or degraded floating panels may be inspected and replaced without disassembly of the floating cover and without removal of any individual panel from the floating cover or roof of the storage tank. Moreover, the entire floating cover does not need to be replaced because any damaged or degraded floating panel may be replaced with a new floating unit after a convenient inspection for the presence of vapor, moisture or condensate trapped in the trough inside each floating panel. [0043]
Although the preferred embodiment of the present invention has been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents. [0044]

Claims

What is claimed is:

1. A panel alignable with a plurality of adjoining panels to form a floating cover for a storage tank, said panel comprising:

honeycomb insert bearing a plurality of discrete cells sealed at opposite ends by different planar members that are spaced-apart by said cells;

a frame bounding a peripheral wall formed between planar members by said cells, said frame having opposite flanges engaging corresponding different ones of said planar members and an end wall spaced-aprat form said peripheral wall joining said flanges together, a lower one of said flanges underlying and extending beneath and beyond an adjacent one of said planar members to form a though positioned between said end wall and said peripheral wall; and

an inspection port provided on upper one of said flanges in visual alignment with said trough.

2. The panel of claim 1, further comprising a sealant interposed between an underside of said adjacent one of said planar members and said lower one of said flanges.

3. The panel of claim 1, further comprising:

a sealant interposed on both surfaces of honeycomb core of said adjacent one of said planar members and said lower one of said flanges;

said adjacent one of said planar members and said lower one of said flanges channeling any product held by the storage tank beneath said panel, into said panel via said trough upon deterioration of said sealant.

4. A floating cover in a storage tank, comprising:

a plurality of discrete panels assembled in an ordered array to form said floating cover, each of said panels having an internal honeycomb structure, each of said panels having a frame coupled to a peripheral side of said honeycomb structure and having a side wall spaced-apart from said peripheral side of said honeycomb structure, each of said panels having a hollow interior formed between said peripheral side of said honeycomb structure and said side wall of said frame; and

an inspection port formed on said frame providing direct communication into said hollow interior from a top side of said panels, while enabling visual inspection of said hollow interior from said top side of each of said floating panels.

5. The floating cover of claim 4, further comprising a sealant disposed between said frame and said honeycomb structure.

6. The floating cover of claim 5, further comprised of:

a lower extension disposed beneath said honeycomb structure; and

said frame comprising a floor extending from beneath said lower extension, beyond said peripheral side, and terminating said hollow interior, with said sealant disposed between said lower extension and said floor;

said lower extension and said floor channeling any product held by the storage tank into said panel via said floor upon deterioration of said sealant.

7. The floating cover of claim 6, further comprised of said inspection port being visually aligned with said floor via said hollow interior.

8. The floating cover of claim 4, with said frame comprising:

a lower frame providing said side wall, a lower extension extending from a lower end of said said wall, and an upright extension extended from an upper end of said side wall;

an upper frame having an upper extension parallel to said lower extension and spaced-apart from said lower extension by a length of said side wall, said upper frame providing an upright extension extending from said upper extension and mating with said upright extension of said lower frame;

said honeycomb structure positioned between and coupled to said lower extension and said upper extension; and

a trough defined by said lower extension, said upper extension, said side wall, and a peripheral side of said honeycomb structure disposed between said lower extension and said upper extension, having said hollow inside.

9. The floating cover of claim 8, further comprising:

said lower frame having a lower detent formed on said upper end of said side wall of said lower frame, having a groove formed between said lower detent and said upright extension of said lower frame; and

a first protrusion formed between said upper extension and said upright extension of said upper frame, located in said first groove when said lower frame, said upper frame, and said honeycomb structure are assembled to form said floating member.

10. The floating cover of claim 8, with said upper frame comprising:

an upper detent formed on a distal end of said upright extension of said upper frame; and

a groove formed between said upper detent and said upright extension of said upper frame, receiving a distal end of said upright extension of said lower frame when said lower frame and said upper frame are assembled to form said floating member.

11. The floating cover of claim 8, further comprising:

an upper rib formed on said upper frame and coupled adjacent to upper rib formed on adjacent upper frame of adjacent floating member; and

a lower rib formed on said lower frame and coupled adjacent to lower rib formed on adjacent lower frame of adjacent floating member.

12. The floating cover of claim 11, further comprising:

an upper clamping bar having a pair of coupling grooves receiving said upper ribs of two adjacent floating members;

a lower clamping bar having a pair of coupling grooves receiving said lower ribs of said two adjacent floating members; and

a fastener coupling said upper clamping bar to said lower clamping bar when said upper ribs and said lower ribs are inserted into respective coupling grooves of said upper clamping bar and said lower clamping bar.

13. The floating cover of claim 8, further comprising:

a serrated surface formed on said lower extension and said upper extension; and

a sealant disposed between said serrated surface of said lower extension and said honeycomb structure and between said serrated surface of said upper extension and said honeycomb structure.

14. The floating cover of claim 13, further comprising an adhesive applied between said sealant said serrated surface of said upper extension and said honeycomb structure.

15. A floating cover in a storage tank, comprising:

a plurality of discrete panels assembled to form said floating cover, each of said panels having an internal honeycomb structure, a lower frame, and an upper frame coupled to said lower frame, said honeycomb structure being disposed between and coupled to said lower frame and said upper frame;

said lower frame extending beyond a peripheral side of said honeycomb structure and forming a trough spaced below and apart from said honeycomb structure, said trough being defined by said lower frame and said peripheral side of said honeycomb structure; and

an inspection port formed on said upper frame providing direct communication into said trough while accommodating visual inspection of said trough from above each of said panels.

16. The floating cover of claim 15, further comprising a sealant disposed between one of said lower and upper frames and said honeycomb structure.

17. The floating cover of claim 15, further comprising

a sealant interposed between an underside of said honeycomb structure and said lower frame; and

said underside of said honeycomb structure and said lower frame channeling any product held by the storage tank into an interior of one of said panels upon deterioration of said sealant of said one of said panels.

18. The floating cover of claim 15, any product held by the tank and introduced into an interior of one of said panels is visible from a top side of said one of said panels through said inspection port of said one of said panels.

19. The floating cover of claim 15, with said frame comprising:

said lower frame having said side wall, a lower extension extended from a lower end of said wall, an upright extension extended from an upper end of said side wall; and

said upper frame having an upper extension being parallel to said lower extension and spaced-apart from said lower extension by a length of said side wall, having an upright extension extended from said honey structure is inserted between and coupled to said lower extension and said upper extension.

20. The floating cover of claim 19, further comprising:

a first protrusion formed between said upper extension and said upright extension of said upper frame, inserted into said first groove when said lower frame, said upper frame, and said honeycomb structure are assembled to form said floating member.

21. The floating cover of claim 19, with said upper frame comprising:

22. The floating cover of claim 19, further comprising:

an upper rib formed on said upper frame;

a lower rib formed on said lower frame;

a stud coupling said upper clamping bar to said lower clamping bar when said upper ribs and said lower ribs are inserted into respective coupling grooves of said upper clamping bar and said lower clamping bar.

23. The floating cover of claim 19, further comprising:

a serrated surface formed on said lower extension and said upper extension; and