Horizontal tanks

Horizontal tanks are used for the technological infrastructure of storage plants, petroleum-storage depots, oil production and refining enterprises and other industrial facilities. They are used not only for storing various kinds of liquids, but also for measuring the volume and distribution of the stored petroleum products. Depending on the type of internal coating, they can store light and heavy petroleum products, various fuel and lubricant materials, oil, chemical solutions, as well as food products and water. They can also perform a function of fire tanks.

Design, manufacture and installation of horizontal tanks are regulated by the following regulatory documents:

• GOST 17032-2010 "Horizontal steel tanks for petroleum products. Specifications"
• GOST R 52630-2012 "Vessels and welded steel apparatus"

Operating conditions of horizontal tanks

In accordance with GOST 17032-2010, the working fluid is stored under positive pressure at 0.001 MPa - 0.07 MPa. Density should not exceed 1300 kg/m³. The temperature should lie between -65°C and + 90°C. According to GOST 12.1.007 “Noxious substances. Classification and general safety requirements" the working environment refers to the 1, 2, 3 and 4 explosives hazard class. Also it is possible to store industrial water and non-aggressive substances.

Horizontal tanks for oil products are installed at a facility with a seismicity of not more than 7 points. In accordance with GOST 15150-69 "Machines, devices and other technical devices. Performance for different climatic regions. Categories, operating conditions, storage and transportation with regard to the impact of climatic factors of the external environment " they refer to climatic conditions of N and NF.

Horizontal tanks setup

The Saratov Reservoir Plant produces horizontal tanks of 3 m³, 5 m³, 10 m³, 25 m³, 50 m³, 75 m³ and 100 m³. At the Customer's request, it is possible to produce other capacities.

In terms of spatial arrangement there are the aboveground and the underground storage tanks. Ground-level installation is also possible, when the shell is placed underground while the fitting pipes, neck and manway plates are above ground level.

Structurally, horizontal tanks can be single-walled and double-walled, one-, two- and multisphere (with shields) for simultaneous storage of various types of liquids.

They are produced with different types of heads: flat - for tanks up to 8 m³, conical - for capacities above 8 m³. For working under high pressure, an elliptical and spherical shape is used.

Our practice of design and manufacturing shows that at an excess pressure below 0.04 MPa it is better to use membrane heads in the tanks with a capacity from 3 to 10 m³ and a diameter of up to 2.8 m. The conical shape is more preferable for storing oil products from 25 to 75 m³ with a diameter of up to 3.25 m and with an excess pressure of up to 0.05 MPa. Tanks of large capacity with cylindrical shell and a diameter of 3.25 m are suitable for various fluids under excess pressure of up to 0.07 MPa.

Standard equipment includes manway plates and necks. At the Customer's request, additional equipment can be installed for long, reliable and safe operation – holders, sockets, drains, observation platforms and ladders, heating devices (for limy products), liquid level measuring devices, alarm devices and other attachments.

Aboveground and the underground storage tanks: design, corrosion protection, thermal insulation, installation

The main constructive elements are:

• horizontal cylindrical tank shell
• two heads
• support diaphragms or intermediate stiffener rings for strengthening the structure
• tank racks
• lifting gears for transportation

Summary table of technical characteristics of horizontal tanks

Thermal insulation

Limy oil products storage predetermines the need for a thermal insulation of the shell. For preheating or cooling off the stored liquid, it is necessary to maintain the certain temperature. This function is performed by the heat exchange jacket or a steam-water or electric heating system. The heat-exchanging jacket with a thickness of up to 120 mm is capable of maintaining the temperature regime due to the heat transfer medium circulating in it.

Anticorrosive protection

To protect metal structures from the negative effects of stored fluids, the tank shell is treated with anti-corrosion coatings. Anticorrosive protection is performed by staining shells with several layers of polyurethane compositions (primer, enamel) on the outside and inside.

As a protection of underground horizontal storage tanks, reinforced corrosion protection is used, since the outer surface is exposed to negative effects of groundwater.

Horizontal tanks erection

Horizontal aboveground storage tanks are mounted on two or more tank supporting structures depending on the capacity. Supports are attached to the concrete inserts of the foundation to avoid contact of the shell with the ground.

Underground installation of tanks is carried out in the excavated ditch on the pudded earth. Depth should be below the frost line.

Operation of steel horizontal tanks

To ensure access inside of the tank for an inspection, maintenance or repair, there should be necks in the structure. For the operation conventional, the tanks are equipped with auxiliary metal structures for maintenance sites, ladders and fencing systems.

In case of underground installation, the neck is located above the ground for an easy access to the equipment and is protected by a maintenance shaft.

Attachable technological equipment of aboveground storage and underground storage tanks

The Saratov Reservoir Plant SARRZ carries out manufacturing and delivery of associated technological equipment:

• drain connections and inlet-distribution nozzles
• manways
• pumping units
• devices for loading and issuing of a stored product
• pressure vent valves

The technological equipment is customized.

Horizontal tanks fabrication

The Saratov Reservoir Plant has all the necessary Certificates of Conformity for the production of aboveground and underground horizontal tanks.

Traditionally they are made of the following materials:

• mild steel C245 (or St3) for the operation under the temperatures above -40°C
• light alloyd steels С345 (09Г2С) for the operation under the temperatures below -40°С
• stainless steel

The thickness of rolled stock varies from 4 to 10 mm.

Tanks production is carried out in two ways:

• method of rolling-up
• shells assembly method

Horizontal tanks production by the method of rolling-up

The method of rolling-up involves the initial preparation of metal sheets for their further assembly and welding into a cylindrical shape. The thickness of the metal used is calculated on the basis of the requirements for the strength and stability of the tank at the site. This type of manufacture is more productive than assembling from shells, but it is possible only with shell thicknesses of not more than 4 mm. At this stage, the sheets are flattened on the levelling machine, a surface, longitudinal and transverse edges are treated, the sheets geometry is checked, and quality-tests are carried out. Next, the steel sheets are assembled into the map sweep and rolled into the cylinder.

Then, an integration bench is used. These are vertical parallel rolled steel joists, horizontal shelves are placed above and below. The lower shelves are attached to the concrete platform. The size of the integration bench allows to assemble of two tanks. Prepared and processed steel sheets are connected and welded by manual welding. For stability, stiffener rings are made, which are mounted on the edge of the panel. Further, folding the panels into rolls is taken place: the steel ropes on one side are fixed to the stiffeners, on the other - to the electric winch drums, with the help of which ropes are wound on the drums. Then the heads are welded to the received roll. Thus, all elements are welded to the roll up to the longitudinal seam.

At all stages of assembly, weld inspection, quality control of surface treatment, geometry of construction are carried out.

Horizontal tanks, manufactured by the method of roll-up, represent a single cylindrical tank of full factory readiness.

Horizontal tanks assembling from shells

The main way to produce horizontal tanks is to assemble from shells. The number of shells is calculated in advance, based on the required capacity.

Each shell is made of metal sheet or steel coil up to 2000 mm thick. Depending on the diameter the shell is one or several milled steel sheets. To give it a cylindrical shape, the sheets are placed on the bending rolls. We have the technical capability of sheet bending up to 25 mm thick.

Heads are made either from one or more stamped plates or from a welded billet. The shells are welded together on a turning rolls to avoid any shifts. Depending on the thickness the joints are welded from two sides. Centering equipment is used for even assembly. The head is attached to the shell, installed in a vertical position with the help of assembly ribs, or stitches, which are removed during the welding process.