The structural elements of the tanks, in accordance with the terminology that the manufacturers have developed, are subdivided into basic and component structures.
The main structural elements of the tank include those structures, without which it is impossible to build a reservoir of the specified design in compliance with a set of requirements for reliable and safe operation of the tank:
- fixed or floating cover
- stairs, platforms, fences
- hatches and nipples
The completing structures include elements that ensure the implementation of additional requirements for the technological design of the reservoir in terms of fire safety and ease of use:
- constructions for maintenance of foam generators
- fire extinguishing and irrigation pipe brackets
- The UDU-10 level gauge bracket
- Stripping sweep
- Bottom cleaning hatch
- other constructions according to the order of the customer
«Samara tank factory» has the necessary technological equipment for the production of tanks by the method of roll-up or sheet assembly. Polystyrene assembly is used for tanks with a lower wall thickness of the wall of more than 18 mm, as well as, at the request of the Customer, for tanks of all sizes, for the production of high-capacity tanks and in the absence of space on the construction site.
For the walls of a sheet assembly, rolling is used in widths from 1.8 m to 3 m and up to 12 m in length. The edges of the sheets are machined (milled) or plasma cut by machines with software control. Rolling of sheets is carried out on 3 and 4 roll bending machines.
The walls of tanks with a volume of up to 20,000 m3 with a thickness of the lower belt up to 18 mm are recommended to be manufactured by the method of roll-up.
The panels of the walls are rectangular in shape, with a deflection of the factory vertical joints and rectilinear initial and final edges, longitudinal joints in the zone of these edges have undercovered areas with prepared cutting for welding of the gear joint.
The toothed mounting junction of the wall is formed by trimming the technological stock allowance along the length, which is usually 150…300 мм.
To ensure the quality formation of rolls of walls of reservoirs with a volume exceeding 5000 m3 technological extensions at the initial and final edges are used.
Bottom of tanks
The bottoms of the tanks can be flat (for tanks up to 1000 m3) иor conical with a slope from the center or to the center — it allows to compensate for possible unevenness of the base sediments .The flat bottoms consist of sheets of one thickness, the conical bottoms have a central part and thickened ring selvages.
The production of flat bottoms and the central part of the conical bottoms with a metal thickness of up to 7 mm is carried out by the method of roll-up, and at a thickness of 8 mm and higher, — Method of sheet assembly. To improve the geometric shape of the bottoms (reducing the flapping that occurs when rolling the sheet and increasing from welding deformations), the recommended minimum thickness of the bottoms is 5 mm, including 1 mm of the allowance for corrosion.
Stationary roofs of tanks from 100 m3 to 100 m3 can be made in the form of smooth conical shells with a cone angle of 15° up to°.
With a shell shell thickness of up to 7 mm, the roof is manufactured in the factory in the form of a rolled sheet. With a shell thickness of more than 7 mm, the roof panel is assembled and welded with double-sided butt welds at the installation (with the edge of the panel).
Stationary roofs in the form of smooth spherical shells can be effectively used for tanks with a volume from 1000 m3 to 5000 m3 with a shell thickness of 6 mm to 10 mm and the absence of load-bearing frame elements.
Spherical shells consist of welded at the plant petals of double curvature, collected on a special conductor of rolled parts.
Conical frame roofs
Conical frame roofs are used for tanks with a volume from 1000 m3 to 5000 m3.
Roofs consist of factory-made sector skeletons, ring frame elements, a central panel and roll-up floorboards. Installation of frames is performed as the roll of the wall is deployed in a manner similar to the installation of traditional shield roofs.
After joining the skeletons with each other, the ring elements are laid on them by the floor panels previously deployed next to the bottom of the tank. The panels are welded together by radial seams and soldered along the perimeter to the wicked corner of the wall. Fastening of panels to elements of a skeleton is not supposed.
The design of frame roofs is carried out in an explosion-proof design in such a way that if the pressure inside the tank is exceeded, for example, during an explosion or as a result of heating from the fire of a neighboring tank, the welded weld of the flooring is torn to the wall without destroying the reservoir itself and without detaching the wall from the bottom.
Explosion-proof roof acts as a safety valve, which at a critical moment will relieve internal pressure and keep the tank and the product stored in it.
Spherical frame roofs
Spherical frame roofs are used for tanks with a volume of more than 5000 m3.
Roofs consist of rolled radial beams, basic and intermediate, ring frame elements, a central shield and sheets of flooring, freely supported by the elements of the frame. On the perimeter of the wall there is a ring of stiffness, perceiving the spacer forces of the dome and ensuring fixation and unchangeability of the wall shape during installat.
Requirements for explosion protection of spherical roofs are similar to the requirements for conical carcass roofs.
Floating roofs are used in tanks without a fixed roof in areas with a normative snow load of up to 1.5 kPa. Floating roofs can be single-deck and two-deck types.
Single-deck floating roofs consist of a sheet membrane, rolled or sheeted, and annular boxes located along the perimeter.
To ensure the drainage of storm water from the roof surface, it has a slope to the center where a flexible or articulated shower set with a sampling device and a check valve is installed. A non-return valve allows stormwater to be taken out of the reservoir and, on the other hand, prevents the product from entering the roof surface. The roof slope is achieved by the loading of its central part.
Single-deck floating roofs are recommended for tanks with a diameter of not more than 50 m and in construction areas where the wind speed does not exceed 100 km / h. With large diameters and greater wind speed, there are significant dynamic loads on the roof membrane, which can lead to damage to the roof membrane.
Two-deck floating roofs are made in two versions of the design:
- traditional roof with outer radial compartments and annular compartments of the central part, the formation of which is performed on the installation
- unified roof with radial prefabricated boxes, the use of which reduces the amount of assembly assembly and welding by more than 40% compared to the traditional version.
The advantage of double-deck floating roofs in comparison with uniform ones are:
- The increased rigidity of the roof, ensuring the perception of maximum wind, snow and seismic loads
- Increased buoyancy of the roof due to the arrangement of geometric compartments over the whole area of the tank
- Elimination of product entry to the roof top deck, if the drain is not sealed (there is no check valve on the drainage device),
- Presence of emergency outlets on the roof surface, excluding overloading and flooding of the roof with storm water in case of failure of the main discharge
- Reducing the heating of the upper layers of the product by solar radiation and thereby reducing the loss from evaporation.
Pontoons are used for tanks with fixed roofs and are designed to reduce the loss of oil and oil products from evaporation.
When filling the customer order form pontoons following may be mentioned: odnodechny (contact type) or aluminum on the floats.
A single-deck pontoon can be rolled or paneled.
The rolled pontoon consists of a single-piece factory-made fabric and radial and annular compartments formed at the installation, providing the necessary buoyancy reserve.
Shield pontoons consist of rectangular boxed boxes of factory manufacturing, connected with each other when installing cards of sheet flooring. The use of panel pontoons is recommended for tanks with a volume of 5000 m3.
Stairs and platforms
Staircases can be of two types: mine or circular (screw).
Mine ladders are a structural and technological element that acts as a staircase for lifting to the roof of the tank, and also serves as a frame for winding wall panels (for the tank up to 3000 m3, the bottom and roof panels can be folded together with the wall).
In terms of the shortcomings of the mine stairs, the following can be noted:
- Shaft ladders require the installation of a separate foundation.
- Stairs are attached to the tank wall by several rows of radial struts, which cause undesirable stress concentrations in the wall, especially when subjected to seismic loads.
Ring stairs meet the design standards of tanks according to Russian and foreign standards and do not have these drawbacks of using mine stairs.
To ensure safety and ease of maintenance on a fixed roof equipment is recommended circular location of sites along the perimeter of the roof. For tanks without a pontoon with a volume of more than 1000 m3 sites of 3⁄4 perimeter are allowed.
The running surface of the platforms can be made of expanded metal, stamped or perforated elements, galvanized gratings.
The fencing of the pads is usually made of a corner profile, at the request of the customer, the railings of the fence can be made of pipes.
Hatches in the tank wall
Hatchways in the wall are made with round diameters of 600 and 800 mm, or with oval dimensions of 600x900 mm. All hatches must have brackets to open the lid.
Branch pipes in the wall
Pipes in the wall for receiving-distribution and the like are performed in three types:
- «Standard» — with one flange (type «S»)
- «Double» — With two flanges (type «D»)
- «Smooth» — With one flange and a pipe cut off from the inside, flush with the wall (type «F»)
The stripping pipe is used, as a rule, in tanks that do not have a sump of stripping.
Hatches and fittings in the roof
In the roof of the tank are installed light hatches with a diameter of 500 and 600 mm with brackets for opening the cover, and mounting hatches 800 mm and 1000 mm in diameter without brackets for opening the lid.
The branch pipes in the roof are subdivided according to the structural design for installation and ventilation. The difference between the ventilation pipes and the installation pipes is that their pipe is cut flush with the roofing.
Bottom cleaning hatch
The bottom cleaning hatch is designed to facilitate routine maintenance of the cleaning and removal of various deposits and contaminants from the reservoir. The bottom hatch is flush with the bottom of the tank on a special foundation to collect the debris to be removed.
The design of the bottom hatch is made in accordance with the standard API 650.
For wide application in domestic practice, hatches of two sizes are recommended: 600х600 and 600х900 mm.
A round sump of stripping is installed on the bottom of the tank in a special pit and is designed to remove water from the reservoir.
In tanks with a flat or conical bottom, which is inclined from the center, the sump is located next to the wall (at a distance of at least 600 mm from the wall or from the annular margin).
In tanks with a conical bottom, which has a slope towards the center, the sump is installed in the center of the bottom.
The dimensions of the sump depend on the diameter of the drainage pipes.
The chute stripper is installed on the bottom of the tank in the pit under the tank wall and is designed to remove bottom water, various deposits and contaminants.
Fire safety constructions
The presence and type of fire safety structures, which include foam extinguishing, cooling and lightning protection devices, are defined in the technological part of the reservoir design. When ordering a reservoir for the project, the type and number of foam generators, the presence of an annular irrigation pipeline, the height and number of lightning receptacles, and the number of earthing fasteners must be indicated.