Patent Application
20170107733
The invention relates to heat insulation technology, in particular a method for thermally insulating tanks for storage of oil and oil products including tanks stored in severe climatic conditions (such as relatively low temperatures).
The task of storing oil in tanks is important and relevant to many of industries including oil production, energy, mechanical engineering, and the like. Often, oil and oil products are stored in metal tanks for relatively long periods of time. Thus, the task of oil storage in tanks includes many subtasks that are based on properties of oil. One such subtask is heat insulation of tanks. Because oil may freeze at temperatures between −60 degrees Celsius (−60° C.) and 30° C., and because it may begin to boil at temperatures as low as 28° C., depending on its contents, requirements for controlling the temperature inside the tank are relatively strict. Moreover, the task of heat insulation is significantly complicated in oil producing sites with harsh and often extreme natural conditions.
To resolve the task of tank heat insulation, the range of materials and structures varies significantly depending on natural conditions and other factors. Traditionally, polyurethane, mineral wool plates, cellular glass, and the like are used as heat-insulating materials. Cellular glass is the most suitable material in extreme weather conditions. This is because heat-insulating and mechanical characteristics of cellular glass do not change over a relatively large range of temperatures and humidity. Another important factor is that cellular glass is a noncombustible material. The high risk of fire associated with oil and oil product tanks is taken into account during selection of materials and heat-insulating methods.
Various solutions are known in the art for insulation of such tanks.
U.S. Pat. No. 4,073,976 (published on 14 Feb. 1978, IPC F17C13/00) discloses a tank (for storage of the liquefied gas) where foam glass blocks are used as a load-bearing insulation at a bottom of the tank. The blocks are covered by a layer of vermiculite particles that provide for higher resistance to a pressure load.
U.S. Pat. No. 4,062,468 (published on 13 Dec. 1977, IPC B65D90/06) discloses an insulation system for big tanks that store fuel. The aim of the disclosure is to increase the cost effectiveness of insulation and its resistance to natural effects. The insulation includes panels of foam glass insulating material fixed on the tank wall and supported by metal rails. A layer of resinous material reinforced by fiber cloth is positioned on an exterior of the insulation.
U.S. Pat. Pub. No. 2012/0325821 (published on 27 Dec. 2012, IPC F17013/00) discloses a cryogenic tank that includes a welded internal tank and an outer shell that surrounds the welded internal tank. The tank also includes concrete foundation that includes a raised part. The tank also includes multiple cellular glass blocks installed on the raised part of the concrete foundation and a leveling concrete layer that coats the top layer of the foam glass blocks. The tank also includes a fastening device fixed in the concrete foundation. The welded internal tank is installed on the leveling concrete layer and an external shell is fixed on the fastening device along the perimeter of the external shell. The annular space between the internal tank and the external shell is filled with perlite.
R.F. patent No. 117467 (published on 27 Jun. 2012, IPC E04B1/76) discloses a heat-insulated coating that includes \foam glass blocks made in shape of a compressed prism. Liquid ceramic heat insulation is used to fasten foam glass blocks to the foundation of the protected structure and to each other.
U.S. Pat. No. 8,381,939 (published on 26 Feb. 2013, IPC E03B11/00) discloses an insulated storage facility that includes modular panels and structures that are stiff enough to store hot and cold liquids. The insulated storage facility is includes multiple insulating panels installed on an insulated supporter to form a cylindrical wall. Insulating panels have a relatively hard structure and support an internal pad. The cylindrical wall of insulating panels is supported by a thin external case. This insulated storage facility also includes a lid supported by insulating panels and that covers the contents of the storage facility.
However, known technical solutions do not provide structural elements that compensate for deformations of the wall of the protected structure during its operation. If deformations of the tank wall appear, the risk of destruction of the heat-insulated layer is high. Moreover, solutions do not provide the quick access to the surface of the tank for its technical maintenance and repair.
U.S. Pat. No. 8,615,946 (published on 31 Dec. 2013, IPC E04B7/00) discloses an insulated wall system that may be used as heat insulation of industrial structures. Heat insulation includes heat-insulating blocks made of any insulating material known in this field, including but not limited by polystyrene, polyurethane, polyisocyanurate, their mixtures, or the like. The insulated wall system includes many metal gratings installed parallel to and separated from each other. The system also includes multiple external panels, each of which is attached to metal gratings formed on the external coating. The system also includes multiple heat-insulating blocks each of which is installed between the metal grating and the external panel. The system also includes a plank between the heat-insulating blocks and the external panel, the plank having a step that fixes the heat-insulating block and decreases mutual side movements of the heat-insulating block and the plank. The system also includes a fastener that fastens the external panel, the plank and the heat-insulating block together with the metal grating. An adhesive layer may be used between the block and the metal grating to make the assembly of the insulated wall simpler. The adhesive material may include, for example, contact adhesives, reactive adhesives (for instance, epoxy resin, acrylate etc.), pressure sensitive adhesives, hot-melt adhesives, or the like.
The drawback of this technical solution is that the structure is extra hard, which may lead to destruction of the hard heat-insulating material where the tank wall has been deformed during operation.
The technical solution that is the closest to the present solution is a heat-insulated tank known disclosed by RF patent No. 2079620 (published on 20 May 2007, IPC E04H7/04). The tank includes elements tightly fixed on the tank body as horizontal bandages with a coat, and heat-insulating panels installed on them. The bandages are made as angles, fixed on the tank body using preassembled supports. The bandages are along a height of the body at distances between 2 meters (m) and 4 m above each other. The heat-insulating panels are formed as semi-hard mineral or slaggy blocks.
However, this technical solution does not provide adequate strength and safety of the tank heat insulation under loads caused by filling or discharge of the raw material or by environmental factors.
The object of the invention is to provide a method for insulating tanks, taking into account the cyclic load on the tank framework (for example, loads due to filling and emptying the tank with oil and oil products), in difficult climatic conditions with temperatures that reach negative 60 degrees Celsius (60° C.) while preserving the safety of the heat insulation and achieving the temperature requirements of the stored fluid.
The result of the method is increased strength of the heat insulation of the tank under loads applied to its framework (stated differently, the result is an increased resistance to deformation). The loads may be caused by loading and discharging of raw material as well as climatic factors. The method also preserves temperature of the stored product ensures security of the heat insulation. In addition, the application of the proposed method protects soil (such as preventing thawing of permafrost) from heat of the product that is stored in the reservoir, and allows the insulation of the tank to be dismantled and reinstalled for maintenance and repair.
The method includes preparing foundation elements of the tank with bottom heat insulation, mounting of the tank on a prepared foundation, installing tank walls and insulation and a roof and roof heat insulation. Heat insulation for the tank walls and roof is carried out by fixing a supporting relieving skirt on the tank walls and roof such that they form tiers. The tiers are then filled from the bottom up with heat insulating material such as cellular glass blocks.
The glass blocks include a row in a lower tier between a lower supporting skirt and the tank bottom annular plate. The cellular glass blocks in this location are removable, enabling a user to remove the blocks to gain access to a corner weld joint “wall-bottom”. Other tiers of the side wall and the roof are filled with cellular glass blocks which are attached to the surface of the tank and to each other using an adhesive material. The blocks are placed in several rows with various adjacent rows offset from each other. A cruciform, or cross, shaped recess is formed in the block on the tank mounting side to receive the adhesive material. The removable blocks of the lower layer or tier are made with shock-absorbing pads placed on the block's end sides so that they snugly fit with each other. The shock-absorbing pads allow the lower blocks to be removed. A metal plate is fixed on the outer surface of the blocks to protect the blocks from mechanical damage. Vertical expansion joints are made in the blocks other than the lower tier blocks by installing blocks such that a gap remains between adjacent blocks. At least one horizontal expansion joint is also formed in the blocks. The vertical expansion joints are located in each layer, except for the lower tier. Expansion joints are formed on the tank roof in each tier and oriented radially relative to the tank roof. The expansion joints are filled with butyl-rubber sealant. A top coat of metal sheets is placed on the outer surface of the cellular blocks, except for the lower layer, to protect the blocks from mechanical stress.
Supporting relieving skirts are fixed on the wall and the tank roof at a distance of between 1.5 meters (1.5 m) and 2 m of each other.
The supporting relieving skirts are mounted on the tank wall and roof using fasteners made of the same material as the tank. The fasteners include a plate that is welded perpendicular to the plane of a plate support platform of the tank, for example, via welding. The supporting relieving skirt is made in the form of beams or corners.
Supporting relieving skirt fasteners are welded to the tank surface at distances of 1.5 m or less on the perimeter of the side wall and around the circumference of the roof.
Top coat metal sheets are attached to the supporting relieving skirts using self-tapping screws with sealing rubber gaskets.
The foam glass blocks for insulation of the tank walls and roof have the following characteristics: a thermal conductivity of no more than 0.05 watts per square meter of surface area for a temperature gradient of one kelvin for every meter thickness (0.05 W/mK), a vapor permeability of 0 mg/mhPa, being in the NG flammability group, a crushing strength of at least 0.7 Megapascals (MPa), and a density of between 115 kilograms per cubic meter (kg/m3) and 180 kg/m3.
The foam glass blocks in each row of each tier are displaced relative to adjacent rows by a distance of half of their length.
Shock absorbing pads of the foam glass blocks of the lower layer are made using a cellular rubber substance having a thickness of between 20 mm and 25 mm. The cellular rubber substance may include for example, cellular rubber available under the brands K-Flex, Armaflex, and may be fixed on the perimeter of the block.
The metal plate coupled to the outer surface of the blocks protects the blocks from mechanical stress. The plate includes galvanized steel having a thickness of 0.7 mm with a tolerance of 0.08 mm. The outer surface of the plate has a corrosion-resistant coating.
The adhesive material is filled in the cross-shaped recess in the foam glass block and protrudes by between 8 mm and 12 mm above the surface of the block for subsequent bonding to the tank surface.
A polyurethane sealant, such as a grade 3M, is used as the adhesive material for mounting the foam glass blocks to the tank surface and to each other.
The tank has a volume from between 200 meters cubed (200 m3) and 20,000 m3.
The size of the gap for forming the vertical and horizontal expansion joints is 20 mm plus or minus 3 mm.
At least three supporting relieving skirts are fixed on the tank wall.
Vertical expansion joints are positioned at intervals of between 4.5 m and 5.5 m about the tank perimeter, and the horizontal joint is placed between a second and a third supporting relieving skirts.
The sheets of galvanized steel having a thickness of 0.7 mm with a permissible deviation of 0.08 mm and having an anticorrosive coating are used as the tank walls and roof top coat to protect the blocks from mechanical impacts.
The tank wall top coat includes profiled galvanized steel sheets and the tank roof top coat includes smooth galvanized steel sheets. The sheets are fastened using self-tapping screws at a distance therebetween of 300 mm plus or minus 5 mm, and the overlap of the top coat sheets are connected using aluminum pop-rivets at a distance therebetween of 300 mm plus or minus 5 mm.
The top coat sheets are bonded to the foam glass blocks using the adhesive.
The cross-shaped notch has a cross-sectional shape in the form of a semicircle having a diameter of 20 mm, with permissible tolerance of 2 mm.
The preparation of the foundation having the heat insulation elements for the tank bottom includes installing reinforced concrete pilework, laying a leveling blanket on the concrete pilework, coating the leveling blanket with bituminous mastic, laying the foam glass blocks on the leveling blanket, filling the joints between the blocks with bituminous mastic, and laying a waterproofing layer upon the foam glass blocks.
Foam glass blocks with following characteristics are used in the foundation: a thermal conductivity of no more than 0.05 watts per square meter of surface area for a temperature gradient of one kelvin for every meter thickness (0.05 W/mK), a vapor permeability of 0 mg/mhPa, being in the NG flammability group, a crushing strength of at least 0.9 Megapascals (MPa), a density of between 130 kilograms per cubic meter (kg/m3) and 180 kg/m3, a length and width of about 450 mm by 600 mm and thickness of between 40 mm and 180 mm.
The leveling blanket includes a layer of cement screed or medium-grain sand having a thickness of at least 50 cm.
The waterproofing layer includes bituminous concrete, for example, of grades I-III and having a thickness of 1 between 1 mm and 3 mm.
The joints between the blocks of the foundation are filled with bitumen mastic having a width of 3 mm plus or minus 1 mm.
A canopy that juts out of the roof includes a coated layer of the roof formed at the connection of the roof with the wall top coat.
The heat insulation is installed on tank structural elements such as pipe branches and manholes.
Collars of steel sheet having a thickness of 5 mm are installed on the pipe branches and manholes on the tank wall and roof.
A cover sheet is mounted to the collars of the tank pipe branches and manholes using self-tapping screws.
Weatherproof anticorrosive coatings that are based on epoxy and polyurethane are used as an anticorrosive coating.
The features of the disclosure are illustrated by the following drawings.
The drawings include the following elements along with their corresponding reference numbers:
The claimed method is carried out as follows.
The foundation (base) is prepared, which includes the installation of a cylindrical tank, including the installation of a bottom 1 of the tank, a wall 2 of the tank, and a roof 3 of the tank. Then, supporting structures are mounted on the tank wall and roof for aiding in installation of, and supporting, heat insulating material. The supporting structures include supporting relieving skirts 5 that form tiers 6 (with brief reference to
The supporting relieving skirts 5 are mounted using fasteners made of the same material as the tank (steel), and include a plate 18 welded to a plate support platform 19 and oriented perpendicular to the plane of the plate support platform 19 (with brief reference to
Then, the foam glass blocks (including, for example, cellular glass) 7 are set on the base of the supporting relieving skirt 5 by tiers starting from the bottom. A lower tier—between the lower supporting relieving skirt 8 and the annular plate of the tank bottom 9 (around the corner weld joint)—one row of foam glass blocks 10 are installed and made removable. This provides the ability for quick extraction of the blocks 10 for easy access to a corner weld joint “wall-bottom” 9.
Removable blocks 10 of the lower layer are made with a shock-absorbing sealing gasket 11 (with brief reference to
A metal plate 12 in the form of a smooth galvanized steel sheet, being 0.7 mm thick with a tolerance of 0.08 mm, is made to have an anticorrosive coating on the outside. The plate 12 is coupled to the outer (front) surface of the removable blocks 10 using bituminous mastic and protects the blocks against mechanical impacts. For protection against mechanical impacts, installation of a metal plate with anticorrosive coating may also be positioned on the inner surface of the block. The size of the removable blocks is determined based on the location of lower supporting skirt.
Other wall tiers and the roof of the tank are filled with additional foam glass blocks, which are attached to the tank surface and to each other using an adhesive material 13. The adhesive material may include, for example, a Polyurethane sealant of grade 3M. The joints between adjacent blocks and between blocks and the tank structural elements are filled with polyurethane sealant applied around the blocks perimeter. The layer of polyurethane sealant may have a width of 3 mm plus or minus 1 mm that provides a balance between strength and flexibility of construction. The blocks are placed in several rows with offset blocks in adjacent rows, as shown in
The cuboid foam glass blocks are formed with a cruciform recess on a side that contacts the tank. The cruciform recess is formed to have two grooves (cavities) intersecting at right angles in the center of the side of the block that is in contact with the tank surface. The grooves have a cross-sectional shape in the form of a semicircle having a diameter of 20 mm with a tolerance of 2 mm, and pass along the entire surface of the block to the ribs. To mount the blocks to the tank surface, the cruciform recess is completely filled with polyurethane sealant, and the adhesive material protrudes beyond the block by between 8 mm and 12 mm to provide an improved coupling of the block with the tank surface.
The walls and roof insulating blocks 7 are foam glass blocks having dimensions of 450 mm by 300 mm and a thickness of between 25 mm and 125 mm. The insulating blocks 7 have the following characteristics: a thermal conductivity of no more than 0.05 watts per square meter of surface area for a temperature gradient of one kelvin for every meter thickness (0.05 W/mK), a vapor permeability of 0 mg/mhPa, being in the NG flammability group, a crushing strength of at least 0.7 Megapascals (MPa), and a density of between 115 kilograms per cubic meter (kg/m3) and 180 kg/m3.
Installation of the heat insulation is performed scaffolding. When the heat insulation is mounted along a tank section perimeter, the scaffolding is moved by the tank generatrix, and heat insulation is mounted on the entire height of an adjacent section.
When mounting blocks on the tank surface, the expansion joints are formed by installing blocks and/or their partial blocks with a gap therebetween, which is filled, for example, with butyl rubber sealant of grade 3M. In this case, at least one horizontal expansion joint 14 is formed on the tank wall. At least 10 vertical joints 15 are formed being in each section (with brief reference to
Vertical expansion joints 15 are positioned, for example, at 5 m intervals along the tank perimeter, and the horizontal joint 14 is placed, for example, between the second and the third supporting relieving skirts (such as in the middle of the two skirts). To ensure the continuity of the wall vertical expansion joints with the roof expansion joints of the tank, foam glass blocks are cut while in place.
Thus, the location of expansion joints, the material they filled with, and the size of the joints compensate for deformation of the tank under external mechanical stress, preserving the integrity of the heat insulation.
The metal sheet coating layers 16, 17 are mounted on the outer surface of the foam glass blocks 7 of the tank wall and roof and protect the blocks 7 from mechanical damage and environmental influences. The metal sheet coating layers 16, 17 include sheets of galvanized steel having a thickness of 0.7 mm with a permissible deviation of 0.08 mm, and are made to have anticorrosive coating on the outside. Profiled sheets having a thickness between 10 mm and 35 mm, and a width of not less than 1,000 mm, are used for the top coat 16 of the tank wall heat insulation. Smooth sheets having a minimum width of 1,000 mm are used for the top coat 17 of the roof heat insulation.
The metal sheets are glued to the foam glass blocks, for example, using a polyurethane sealant, and are fastened to the supporting relieving skirts 5 using galvanized self-tapping screws 20 with sealing gaskets. The screws 20 with sealing gaskets are installed in holes that are jointly drilled in the sheet and the supporting relieving skirt 5 (with brief reference to
The ledge—or canopy 27—on the roof 3 is located at the junction of the roof 2 top coat and the wall top coat to prevent contamination of the tank wall 2 from mud flows (with brief reference to
Collars 28 made of sheet steel and having a thickness of 5 mm are welded on the pipe branches and manholes 4 on the tank wall and roof (with reference to
Weatherproof anticorrosive coatings that include epoxy and/or polyurethane are used as a top coat anticorrosive coating for the pipe branches and manholes 4 on the wall and roof.
Installation of the tank bottom heat insulation 1 includes the installation of concrete ring (pilework) 22. A leveling layer 23, intended for leveling the surface for laying the foam glass blocks, is then placed on the concrete ring 22. The leveling layer 23 includes, for example, cement screed or medium-grain sand with a minimum thickness of 50 cm (with brief reference to
When mounting the heat insulation layer, the cutting of the foam glass blocks in place is allowed. The joints between the blocks are filled with bitumen mastic (an adhesive for the bottom), the mastic layer having a width of 3 mm plus or minus 1 mm. The waterproofing layer 26 has a thickness between 1 mm and 3 mm, and is designed to protect the tank bottom 1 from surface corrosion and provides the uniform distribution of the load on the heat insulation. The waterproofing layer 26 provides elimination of local stress concentrations in the heat insulation during installation and operation of the tank and is applied on the heat insulating layer. Grades I-III bituminous concrete, for example, is used for the waterproofing layer 26.
The application of the proposed method ensures the preservation of the integrity of the heat insulation in the longitudinal and transverse directions of the tank walls; provides insulation of the tank walls, roof and bottom from the effects of low ambient temperatures; and also prevents cooling of the stored fluid in the tank and thawing of soil. The construction performance of the heat insulation provides the possibility of dismantling and re-assembling for tank maintenance and repair, including the quick access to corner weld joint of the tank walls.
This application claims the benefit and priority of PCT Pat. App. No. PCT/RU2014/000213, titled METHOD FOR THERMALLY INSULATING RESERVOIRS and filed on Mar. 28, 2014, also published as WO/2015/147678.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/RU2014/000213 | Mar 2014 | US |
| Child | 15226884 | US |
