Patent Application
20120325821
As recently as the 1950's, double walled spherical tanks 100, illustrated in
As the industry demand for liquid volumes increased, however, the cryogenic liquid storage industry moved away from using the doubled walled spherical tanks 100 and began to use welded shell flat bottom cryogenic liquid storage tanks 200 illustrated in
Traditional welded shell flat bottom cryogenic liquid storage tanks 200 continue to be designed and manufactured using the same philosophy since the late 1950's. As illustrated in
The inner tank 202 is a pressurized stainless steel welded tank that holds the cryogenic liquid. The inner tank 202 comprises a stainless steel floor plate 210, rolled stainless steel wall staves 212, and a stainless steel roof dome 214. The stainless steel floor plate 210, rolled stainless steel wall staves 212, and stainless steel roof dome 214 are all site-welded using stainless steel electrodes and then weld-tested at the installation site.
The outer tank 204 includes a carbon steel floor plate 216, rolled carbon steel wall staves 218, and a carbon steel roof dome 220 that are all shop fabricated but are not shop finished due to the required extensive field welding.
The traditional welded shell flat bottom cryogenic liquid storage tank 200 is supported first by a plurality of concrete columns or piles 222 that may be entrenched in grade 224. The piles 222 support an elevated concrete foundation 226. The elevated concrete foundation 226 may be approximately three feet to four feet thick, for example. The elevated concrete foundation 226 supports the carbon steel floor plate 216. The carbon steel floor plate 216 then supports a first leveling course of concrete 228. The first leveling course of concrete 228 may be three inches to four inches thick, for example. Cellular glass blocks 230 then rest on the first leveling course of concrete 228. The cellular glass blocks 230 may be stacked four feet thick, for example. The function of the cellular glass blocks 230 is to provide the required insulation so that the temperature of the surface of the elevated concrete slab 226 remains close to ambient temperature. A second leveling course of concrete 232 then rests on the cellular glass blocks 230. The second leveling course of concrete 232 may be three inches to four inches thick, for example. Finally, the stainless steel floor plate 210 rests on top of the second leveling course of concrete 232.
As illustrated in
A carbon steel anchor strap 242 is used to anchor the outer tank 204 to the elevated concrete foundation 226. The carbon steel anchor strap 242 may be entrenched in the elevated concrete foundation 226, for example. A stainless steel anchor strap 244 is used to anchor the inner tank 202 to the elevated concrete foundation 226. The stainless steel anchor strap 244 also may be entrenched in the elevated concrete foundation 226, for example.
The carbon steel floor plate 216 of the outer tank 204 is typically laid out on top of the elevated concrete foundation 226 and welded in place at pre-determined, shop-cut, and prepared seams. The welds are vacuum tested prior to proceeding with the pour of the first leveling course of concrete 228.
As illustrated in
Typical applied loads on a traditional welded shell flat bottom cryogenic liquid storage tank 200 include wind loads, seismic loads, weather loads due to snow or ice, for example, dead loads, internal pressure loads such as purge pressure, perlite vertical and horizontal loads and perlite compaction loads. In these typical conditions, the traditional welded shell flat bottom cryogenic liquid storage tank 200 is subject to cyclic compaction loads of the perlite 208 when the perlite insulation 208 itself is subjected to loads when the inner tank 202 expands and contracts due to the change in the level of the cryogenic liquid in the inner tank 202.
The inner tank 202 is designed for wind loads, seismic loads, external purge pressure, perlite vertical and horizontal loads and perlite compaction loads and additional loads due to liquid heads and internal pressure.
Previous and current manufacturing methods and use of traditional welded shell flat bottom cryogenic liquid storage tank 200 are problematic for several reasons. First, field construction of a traditional welded shell flat bottom cryogenic liquid storage tank 200 is a very tedious and lengthy process. For example, for an average sized traditional welded shell flat bottom cryogenic liquid storage tank 200 having a diameter of approximately fifty feet and a height of approximately fifty feet, field construction may exceed six months or more. The number of steps required to shop-fabricate, transport, field assemble, and test all field assembled components of the traditional welded shell flat bottom cryogenic liquid storage tank 200 are numerous, time consuming, and very expensive.
Second, since the traditional welded shell flat bottom cryogenic liquid storage tank 200 takes so long to construct, the daily revenue earning of an operating plant is lost until the traditional welded shell flat bottom cryogenic liquid storage tank 200 has been completed and ready for service, thus, seriously hindering the larger plant design critical path.
Finally, since the outer shell 204 of the traditional welded shell flat bottom cryogenic liquid storage tank 200 is field primed and field painted due to the fact that extensive field welding is necessary to assemble the outer tank 204, the field finish placed on the outer shell 204 cannot be as hard wearing as, for example, a shop baked powder coated finish applied under controlled conditions in a shop setting. The longevity of the field finish is much lower than that of a shop finished outer shell 204, and frequent maintenance and recoating is necessary during plant operation, leading to further time and capital costs.
Bolted carbon steel shell tanks sold by, for example, Columbian TecTank, Tank Connection, and Allstate Tanks have been manufactured and used traditionally for both dry and liquid storage in the agriculture, cement, and oil industries for over fifty years. The bolted shell tanks are used for dry storage of materials such as grains, cement, limestone, clinkers, etc. and for liquids such as sour crude, water, and waste sludge. The typical applied loads on a bolted shell tank for dry storage and liquid storage, consist of wind loads, seismic loads, weather loads due to snow or ice, for example, dead loads, internal pressure loads such as purge pressure, perlite vertical and horizontal loads, and liquid heads (if used for a liquid storage tank).
The described embodiments satisfy the long-felt, but unresolved, need in the art by disclosing, in a first embodiment, a cryogenic storage tank, including a concrete foundation comprising a raised portion, a plurality of cellular glass blocks positioned directly on top of the raised portion of the concrete foundation, a leveling course of concrete poured on top of the uppermost layer of the plurality of cellular glass blocks, a mounting apparatus affixed to the concrete foundation, a welded inner tank comprising an inner tank floor plate, a plurality of inner tank wall staves, and an inner tank roof dome, wherein the welded inner tank is positioned on top of the leveling course of concrete, and a bolted outer shell comprising a plurality of bolted outer shell wall staves and an outer shell roof dome, wherein the bolted outer shell is positioned on top of the mounting apparatus, surrounding the welded inner tank, and spaced apart from the welded inner tank such that the plurality of inner tank wall staves are positioned adjacent to the plurality of bolted outer shell wall staves and the inner tank roof dome is positioned adjacent to the outer shell roof dome, wherein the bolted outer housing is affixed to the mounting apparatus at locations around the periphery of the bolted outer shell.
In an alternative second embodiment, the mounting apparatus of the cryogenic storage tank of the first embodiment is a carbon steel compression ring.
In an alternative third embodiment, the bolted outer shell of the cryogenic storage tank in any one of the first to the second embodiments is a carbon steel bolted outer shell.
In an alternative fourth embodiment, the welded inner tank of the cryogenic storage tank in any one of the first to the third embodiments is a welded stainless steel inner tank.
In an alternative fifth embodiment, the concrete foundation of the cryogenic storage tank in any one of the first to the fourth embodiments is an elevated concrete foundation.
In an alternative sixth embodiment, the carbon steel compression ring of the cryogenic storage tank in any one of the second to the fifth embodiments is embedded in the elevated concrete foundation.
In an alternative seventh embodiment, the carbon steel compression ring of the cryogenic storage tank in any one of the second to the sixth embodiments comprises a welded form bar.
In an alternative eighth embodiment, the carbon steel compression ring of the cryogenic storage tank in any one of the second to the sixth embodiments comprises a welded angle.
In an alternative ninth embodiment, the mounting apparatus of the cryogenic storage tank in any one of the first to the eighth embodiments comprises an anchor bolt template, at least one layer of epoxy grout, and a carbon steel compression ring.
In an alternative tenth embodiment, a method for construction of a cryogenic storage tank is disclosed, comprising the steps of: pouring and curing a concrete foundation including a raised portion by using a mounting apparatus embedded in the concrete foundation as a form for the raised portion, installing a plurality of cellular glass blocks on the raised portion of the poured and cured concrete foundation, pouring and curing a leveling course of concrete on top of the installed plurality of cellular glass blocks, installing a floor plate on top of the leveling course of concrete, installing a plurality of bolted wall staves to the concrete foundation by securing the lowest level of bolted wall staves to the embedded mounting apparatus, welding a plurality of wall staves to the floor plate, welding a first roof dome to the highest level of the plurality of welded wall staves to form a welded inner tank, and installing a second roof dome to the highest level of the plurality of bolted wall staves to form a bolted outer tank.
In an alternative eleventh embodiment, the concrete foundation, made in accordance of the method for construction of a cryogenic storage tank in the tenth embodiment, is an elevated concrete foundation.
In an alternative twelfth embodiment, the bolted wall staves, the second roof dome, and the mounting apparatus, made in accordance of the method for construction of a cryogenic storage tank in any one of the tenth to the eleventh embodiments are composed of carbon steel, and the floor plate, welded wall staves, and first roof dome are composed of stainless steel.
In an alternative thirteenth embodiment, the method for construction of the cryogenic storage tank in any one of the tenth to the twelfth embodiments includes hydropneumatically testing the welded inner tank.
In an alternative fourteenth embodiment, the method for construction of the cryogenic storage tank in any one of the tenth to the thirteenth embodiments includes vacuum testing the bolted outer shell.
In an alternative fifteenth embodiment, the method for construction of a cryogenic storage tank in any one of the tenth to the fourteenth embodiments includes installing perlite insulation in a void space between the welded inner tank and the bolted outer shell.
In an alternative sixteenth embodiment, the method for construction of a cryogenic storage tank in any one of the tenth to the fifteenth embodiments includes installing stainless steel anchor straps to the concrete foundation and the welded inner tank.
In an alternative seventeenth embodiment, the method for construction of a cryogenic storage tank in any one of the tenth to the sixteenth embodiments includes installing a stainless steel box, a liquid withdrawal pipe, and Rockwool insulation in the plurality of cellular glass blocks.
In an alternative eighteenth embodiment, a cryogenic storage tank is disclosed, comprising: a welded inner tank, an outer shell surrounding the welded inner tank, a concrete foundation comprising a raised portion, a plurality of cellular glass blocks positioned directly on top of the raised portion of the concrete foundation, a leveling course of concrete poured on top of the uppermost layer of the plurality of cellular glass blocks, and a mounting apparatus affixed to the concrete foundation, wherein the welded inner tank is positioned on top of the leveling course of concrete and the outer shell is affixed to the mounting apparatus at locations around the periphery of the outer shell.
In an alternative nineteenth embodiment, the welded inner tank of the cryogenic storage tank of the eighteenth embodiment is a stainless steel inner tank, the outer shell is a carbon steel bolted outer shell, the concrete foundation is an elevated concrete foundation, and the mounting apparatus is a carbon steel compression ring.
The disclosed methods and apparatuses reduce time and cost in the design and construction of at least one of the exemplary cryogenic storage tanks disclosed by replacing the carbon steel bottom plate of the outer tank with mounting apparatus that may act as a template for the outer shell anchor bolts, a compression plate for the outer shell of the tank, and a form plate for the pouring of the concrete foundation with a raised portion, thereby saving time by combining two concrete pours into one pour and effectively reducing the curing time necessary for two separate concrete pours. Traditionally, twenty-eight (28) days of curing time is required for each pour of concrete.
The disclosed methods and apparatuses also disclose use of an outer shell or tank, which may be a bolted shell that is shop finished and oven baked under controlled shop conditions instead of the welded shell flat bottom cryogenic liquid storage tank.
The foregoing summary, as well as the following detailed description of exemplary embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating embodiments, there is shown in the drawings exemplary constructions; however, the invention is not limited to the specific methods and instrumentalities disclosed. In the drawings:
Embodiments of the invention include a new design and manufacturing method for a cryogenic liquid storage tank that will drastically reduce field construction time and capital costs. In some instances, the field construction time may be reduced from six months to approximately three months, for example, thereby saving substantial time and capital costs. The cost savings in time of construction through the elimination of work, labor requirements, elimination of weld testing for the outer tank shell, and the ease of installation of bolted stave panels are estimated to be approximately 50% of the traditional welded shell flat bottom cryogenic liquid storage tanks 200.
The void space 706 is generally filled with perlite insulation 708. The void space 706 may also be filled with other types of insulation material. The carbon steel bolted outer tank 704 may be an API-12B fluted shell, for example, or a Rolled Tapered Panel bolted shell, for example.
Use of the carbon steel bolted outer tank 704 eliminates the requirement to field weld, field test, and field coat the outer tank, thus, saving months of field time because the carbon steel bolted outer tank 704 can be constructed comparatively quickly and pre-painted prior to shipping. First, welding is a time-consuming process that requires extensive testing after completion. Bolted panels require much less time to construct and test, thus, providing a solution to the long-felt, but unsolved need, in this industry to reduce construction time and costs in the construction of cryogenic storage tanks. Second, bolted panels are shop finished under controlled shop conditions, whereas the traditional field welded panels need to be field-primed and finished and cannot compare to shop finish bolted panels in terms of durability and quality.
The welded stainless steel inner tank 702 is a pressurized tank that holds, for example, the cryogenic liquid. The welded stainless steel inner tank 702 comprises a stainless steel floor plate 710, rolled stainless steel wall staves 712, and a stainless steel roof dome 714. The stainless steel floor plate 710, rolled stainless steel wall staves 712, and stainless steel roof dome 714 are all site welded using stainless steel electrodes and then weld-tested at the installation site.
The carbon steel bolted outer tank 704 comprises bolted outer tank wall staves 716, a mounting apparatus 718, welded form bars 720, and a carbon steel roof dome 722. The mounting apparatus 718 may be a carbon steel compression ring 718, for example. For simplicity, the mounting apparatus 718 shall be referred to hereinafter as a carbon steel compression ring 718 for convenience purposes only. The carbon steel floor plate 216 from the traditional welded shell flat bottom cryogenic liquid storage tank 200 is eliminated and replaced with the carbon steel compression ring 718 and welded form bars 720 that serve as both a form for the poured concrete (i.e., the concrete poured to create the elevated concrete foundation 728) as well as a template for the anchor bolts 730 of the carbon steel bolted outer tank 704. The carbon steel compression ring 718 may be embedded in the elevated concrete foundation 728 and could serve as the compression plate for the carbon steel bolted outer tank 704. The carbon steel compression ring 718 may be in the shape of a ring, for example, but it may also be form in the shape of an octagon, a heptagon, a hexagon, or some other similar shape. Further, the carbon steel compression ring 718 may not be a continuous shape, but a series of arcs, for example, making up a non-continuous shape, or a plurality of small plates positioned separate and apart from each other but in a circular pattern.
Like the traditional welded shell flat bottom cryogenic liquid storage tank 200, the exemplary cryogenic liquid storage tank 700 is supported first by a plurality of concrete columns or piles 724 that may be entrenched in grade 726. The piles 724 support an elevated concrete foundation 728. The elevated concrete foundation 728 may be approximately three feet to four feet thick, for example, and may be reinforced. The embedded carbon steel compression ring 718 and the welded form bar 720 are embedded into the elevated concrete foundation 728 along with carbon steel anchor bolts 730, the reinforcing bars 746 and the stainless steel anchor straps 732 for the welded stainless steel inner tank 702, illustrated in
A leveling course of concrete 736 then rests on the cellular glass blocks 734. The leveling course of concrete 736 may be may be three inches to four inches thick, for example. The purpose of the leveling course of concrete 736 is to provide a hard wearing surface for the stainless steel floor plate 710 to be laid out and welded and as yet another line of defense from cryogenic leaks damaging the elevated concrete foundation 728. Finally, the stainless steel floor plate 710 rests on top of the leveling course of concrete 736.
Use of the embedded carbon steel compression ring 718 in this way combines the two concrete pours (i.e., the concrete pours for the elevated concrete foundation 226 and the first leveling course of concrete 228) saving at least another twenty-eight (28) days of schedule field time (i.e., because the each concrete pour takes approximately twenty-eight (28) days to cure). Omission of the carbon steel floor plate 216 from the traditional welded shell flat bottom cryogenic liquid storage tank 200 with the embedded carbon steel compression ring 718 also eliminates the need for a separate first leveling course of concrete 228 for the cellular glass blocks 734 as one may be poured along with the elevated concrete foundation 728 pour (i.e., the raised portion 752).
As illustrated in
Carbon steel anchor brackets 750, illustrated in
Alternatively, and as illustrated in
Alternatively, as illustrated in
The pre-assembled carbon steel roof dome 722 is welded to the top course of the bolted carbon steel outer tank wall staves 716 and weld-tested in step 1314. The welded stainless steel inner tank 702 is hydropneumatically tested to simulate actual operating pressures in step 1316. The carbon steel bolted outer tank 704 is vacuum tested to simulate actual operating pressures in step 1318.
The liquid withdrawal pipe 738 is connected to the distribution system (not shown), the piping welds are pressure tested, and the entire exemplary cryogenic liquid storage tank 700 is cleaned in step 1320. Finally, perlite insulation 708 is installed in the void space 706 between the welded stainless steel inner tank 702 and carbon steel bolted outer tank 704 in step 1322. The exemplary cryogenic liquid storage tank 700 construction is then complete and it is ready for service.
Alternatively, in step 1310, the rolled stainless steel wall staves 712 may be jacked up and welded to each other until the bottom course of the rolled stainless steel wall staves 712 bear on the stainless steel floor plate 710, where they may be then welded at the vertical joint.
Alternatively, and depending on the space availability of the site, the stainless steel roof dome 714 or the carbon steel roof dome 722 may be assembled on-site.
Alternatively, in step 1308, the base course of bolted carbon steel outer tank wall staves 716 may be assembled first and the higher courses assembled on top of the base course of bolted carbon steel outer tank wall staves 716 subsequently. In yet another alternative, the topmost course of bolted carbon steel outer tank wall staves 716 may be assembled first on top of the embedded carbon steel compression ring 718 and jacked up progressively as lower courses are assembled at man height and jacked up such that the base course of bolted carbon steel outer tank wall staves 716 are assembled last.
A comparison of the construction sequences between the traditional welded shell flat bottom cryogenic liquid storage tank 200 and the exemplary cryogenic liquid storage tank 700 in
Additionally all preparation, priming and painting onsite of the outer tank 204 is completely eliminated because the shell staves of the carbon steel bolted outer tank 704 are shop primed, painted, and cured before delivery to the site. The combined benefits of these actions will eliminate the need for an entire welded seam floor plate and the required vacuum testing of the welds, thus saving weeks of field schedule.
While aspects of the present invention has been described in connection with the preferred embodiments of the various figures, it is to be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiment for performing the same function of the present invention without deviating therefrom. For example, in yet another embodiment, the outer tank may not be constructed as a carbon steel bolted outer tank 704, but may be constructed more like the traditional welded shell outer tank 204. In this embodiment, the welded outer tank comprises rolled welded wall staves and a welded roof dome, but does not comprise a carbon steel floor plate 216. An embedded carbon steel compression ring 718 may be used in conjunction with the elevated concrete foundation 728, raised portion 752, form bar 720, and carbon steel anchor bolts 730 to affix the welded outer tank to the raised portion 752 of the elevated concrete foundation 728. While this embodiment will not have the same cost and time savings of the other embodiments described above, elimination of the carbon steel floor plate 216 and the pour of the first leveling course of concrete 228 will provide some cost and time savings. Additionally, and as noted above, while some emphasis has been placed on using particular materials for the various parts of the cryogenic storage tank, repeated emphasis should not prevent one of ordinary skill in the art to understand that the other materials listed here may also be used for construction of these various parts. Therefore, the claimed invention should not be limited to any single embodiment, but rather should be construed in breadth and scope in accordance with the appended claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US10/27658 | 3/17/2010 | WO | 00 | 9/4/2012 |
