Ufa Metalworks PJSC AK VNZM

+7 (347) 216-45-65

16/2 Yubileynaya St., Ufa

Vertical steel tanks

Description

Vertical steel cylindrical tanks RVS are used for collection, storage and discharge of liquid products.

Generally the vertical tanks are used for storage of:

Popularity of vertical cylindrical tanks as a storage method for oil products, water and other liquids is based on their low price, speed of their production and ease of operation.

Our company offers complex supply and installation of vertical steel tanks with capacity of 63 m3 — 120 000 m3, as well as individual performance of the services including: designing, production, installation of thermal insulation and heating, delivery, supply of processing equipment and assembly.

Designing and production of vertical steel tanks is performed according to the regulatory documents in force. Designing is performed on individual basis for every Customer.

Technological capabilities of our company enable manufacture of tanks using rolling method and plate-by-plate method.

Our specialists can help you to choose the optimal design variant, taking into account all wishes, can offer the functional and least-cost solution meeting all requirements, regulatory documents and safety rules in force.

In order to facilitate the product purchase process, we suggest you downloading and filling out the questionnaire in Excel. Thereafter you can send it to us using the information request form or to corporate e-mail. Thus you can quickly obtain information on equipment cost proceeding from its specification.

Don’t forget to enter your contact details in the corresponding columns and our specialists will contact you and provide detailed information on manufacturing cost and answers to all your questions.

Types of vertical steel tanks RVS

The choice of type of cylindrical tank depends on stored product, specific features of technological process of the company and characteristics of the installation site. There are 4 basic types of vertical cylindrical tanks.

RVS — vertical steel tank with fixed roof without pontoon

It is used for storage of products with relatively low volatility (saturated vapour pressure up to 26,6 kPa) and ignition point over 61 °C. The most frequently products in these cylindrical tanks are fuel oil residues, diesel, domestic kerosene, bitumen, liquid asphalt, oil (including oil for food) and water. Vertical steel tank with fixed roof and without pontoon also can be used for storage of more volatile (vapour pressure up to 93,3 kPa) and highly inflammable products. In such cases RVS tank is equipped with gas piping or vapor recovery unit.

RVSP — vertical steel tank with fixed roof and pontoon

It is used for storage of products with vapour pressure 26,6 — 93,3 kPa and ignition point under 61°Ñ. The most frequently products in these cylindrical tanks are oil, gasoline, kerosene and jet fuel. A pontoon is a rigid gas-tight floating cover in form of a disk which is inserted in the tank body on the product surface so that at least 90% of its area is covered. The annular gap between the pontoon and the tank wall is sealed off with special rim seal. The pontoon is used for reduction of saturation rate of the steam-and-gas zone of the vertical tank with vapours of stored product.

PVSPk —vertical steel tank with internal floating roof

This version of tanks implies the use of roof located on the surface of the stored product with full contact. The floatability of the roof is achieved by means of application of leak-proof frame bays or buckets. The roof in the emptied vertical cylindrical tank is located on the special support mounted on the bottom. The non-rotation of the floating roof of the tank is achieved by means of use of guide columns. The weak point of the floating roof is probability of pollution of the stored product due to precipitation. There are also cases when rim seal freezes to the wall. The advantage of this roof design is reduction of product evaporation losses.

Cylindrical tanks with protective wall («glass in glass»)

Such version of vertical tanks is used at production sites where bunds of a tank farm are impossible to install. These cylindrical tanks with protective wall are also located near water basins and in urban areas for purposes of protection of environment and people. The protective wall is installed in order to avoid leakage of the product in case of tank depressurization.

Vertical steel tank production

There are two methods of manufacture of vertical steel tanks.

Rolling method

This method implies that tank wall, bottom and roof are brought to the construction site in form of strip panels. The advantages of this method are the following:

  • reduction of tank installation period by 3-4 times as a result of cutting down the volume of welding procedures on the construction site by about 80 % at the average;
  • high quality of welds achieved by double-sided automatic welding at the plant.

Strip panels are produced from steel sheets of modular size 1500×6000 mm. Strip panels are automatically welded on a special coiling machine.

Plate-by-plate method

This method implies that the wall sheets (maximum size 2500×10000 mm) which are rolled to the radius stipulated by the design project and the bottom sheets are prepared at the plant. Then the sheet elements are packed in a special way in order to be prepared for transportation. Wall and bottom assembly (welding) shall be performed on the construction site.

Basic and constitutive elements of vertical tanks.

According to manufacturers’ glossary tank construction elements are subdivided into basic and constitutive elements.
Tank basic elements include elements without which construction of tanks of specific design with observance of reliable and safe operation requirements is impossible.

Basic elements

Walls

For today there are two basic methods of production of tank wall: plate-by-plate and rolling method.

Rolling method is used for tanks with 18 mm bottom flange and above, as well as for all standard sizes of tanks upon request of the Customer.
Plate-by-plate method uses metal-roll 1.8-3 m wide and 12 m long. Sheet edges are processed by mechanical method (milling) or plasma cutting on the program control equipment.

Sheet rolling is performed on 3 or 4 roller bending machine.

It is recommended to use the rolling method for manufacture of tank walls with total volume up to 20 000 m3 and 18 mm bottom flange. The panels have rectangular form with stagger of plant vertical joints and straight initial and end edges. The longitudinal seams in the area of these edges have underwelded areas with preparation for saw-tooth joint. The saw-tooth joint is built by means of cutting of technological allowance of the panel along the length, which is usually 150...300 mm.

Triangular technological extensions on initial and end edges are used to ensure high-quality formation of tank wall rolls with capacity over 5 000 m3.

Wall panels of tanks with capacity up to 5000 m3.
Wall panels of tanks with capacity over 5000 m3.

Tank bottom

Tank bottoms can be flat (for tank capacity of up to 1 000 m3) or conic with inclination from or to the center.

It is recommended to use the inclination from the center, it allows compensating possible differential settlements.

The flat bottoms consist of sheets of the same thickness, the conic bottoms have the central part and thickened annular plate. It is recommended to use plates for tanks with capacity of over 2000 m3.

Manufacture of flat bottom and central part of the conic bottom up to 7 mm thick is performed by rolling method, over 8 mm — by plate-by-plate method.
For improvement of a geometrical form of the bottom (reduction of clearance gaps arising at sheet rolling and increasing due to welding deformations) it is recommended to apply bottoms with minimum thickness 5 mm, including 1 mm for corrosion allowance.

Fixed and floating roof

Conical shell

Fixed roof of tanks with capacity 100 m3-1000 m3 can be manufactured as smooth conic shell with conical angle 15°-30°. If shell is up to 7 mm, the roof is manufactured on the works as a rolling sheet. If shell is over 7 mm, the roof panel is assembled and welded with double butt joints on the installation site (with panel edging).

Spherical shell

Fixed roof in form of smooth spherical shells can be used effectively for tanks with capacity 1000 m3 — 5000 m3 and thickness of shell from 6 mm to 10 mm. There are no frame supporting elements.

Spherical shell consists of doubly curved blades welded at the works and assembled on the special fixture from rolled elements.

Conical frame roof

Conical frame roof is used for tanks with capacity from 1 000 m3 to 5 000 m3.

The roof consists of the sector frames made at the works, ring frame elements, central board and rolled covering panels. Installation of frames is carried out in process of unfolding of a wall roll similarly to installation of conventional panel roof.

It is necessary to unfold the covering panels near the tank bottom and then put them on the frames connected by means of ring elements. Panels are welded to each other by coursing joints and to the wall corner along the perimeter. Fastening of panels to frame elements is not allowed.

Conical frame roof is manufactured in explosion-preventive version. The roof covering is not welded to the frame in this case, but remains attached only to the upper ring element of the wall. This enables the covering to be torn off the wall in case of emergency pressure increase inside the body of the tank, for example in case of explosion or heating due to fire in the adjoining tank. The explosion-protected roof plays a role of an emergency valve which relieves pressure at a critical moment and keeps the tank and the product safe.

Spherical frame roof

Spherical frame roof is used for tanks with capacity over 5000m3.

The roof consists of main and intermediate rolled radial beams, frame ring elements, central panel and covering sheets which are freely supported on frame elements. There is a stiffening ring along the wall perimeter which takes up the thrust force of the cone and ensures fixation and stability of the geometrical form of wall during installation.

Requirements for explosion proofness of spherical roofs are similar to requirements to conical frame roofs.

Floating roof

Floating roofs are used in tanks without fixed roofs. This roof type is to be used in areas with standard snow load up to 1.5 kPa.

There are two types of floating roofs: single-deck floating roof and double-deck floating roof.

Single-deck floating roofs consist of sheet diaphragm, produced by rolling or plate-by-plate method, and annular buckets along the perimeter.

The roof diaphragm has inclination to the center in order to provide storm water drainage. A flexible or swinging water outlet is installed in the center, with an intake and a backpressure valve. The backpressure valve makes it possible to drain water and to prevent entering of the stored product to the roof surface. The inclination of the diaphragm to the center is provided by tightening weight.

Single-deck floating roofs are meant for tanks of up to 50 m in diameter installed at the production sites with the standard wind speed within the limits of 100 km/h.

Larger diameters and higher wind speed cause considerable dynamic loads on the roof diaphragm which can lead to its damage.

There are two versions of double-deck floating roofs:

  • standard roof with outside radial bays and annular bays of the central part, that are made in the course of installation;
  • uniform roof with factory-built radial buckets application of with reduces the scope of assembly and welding procedures by over 40% in comparison with the standard version.

The advantages of double-deck floating roofs in comparison with single-deck floatig roofs are:

  • higher rigidity of roof which bears maximum loading (i.e. wind, snow and earthquake load);
  • increase in roof floatability due to arrangement of pressurized bays in the entire area of the tank;
  • entering of the product on the upper deck of the roof in case of outlet seal failure is excluded (there is no backpressure valve on the intake of the outlet);
  • availability of emergency outlets on roof surface which exclude overload and flooding of the roof with storm waters in case of failure of the main water outlet;
  • reduced heating of upper product layers by solar radiation and thereby reduced evaporation losses.

Pontoons

Pontoons are used in the tanks with fixed roofs and intended for reduction of evaporation losses of oil and oil products.

Customer can choose the following types of pontoons in the Order Form: single-deck (contact) or floating aluminum.

There are two versions of single-deck pontoons: rolled and panel version. The rolled pontoon consists of factory-built single-deck panel and radial and annular bays assembled on the installation site, which provide the necessary floatage.

Panel pontoons consist of large rectangular factory-built buckets connected with each other with sheet covering. Use of panel pontoons is recommended for tanks with capacity over 5000 m3.

Stairs, platforms

There are two types of tank stairs: shaft stairs or circular stairs.

Shaft stair is a constructive and technological element which plays a role of the stair itself to climb to the tank roof, as well as a frame on which the wall panel is rolled on (in case of tanks up to 3000 m3 the wall panels with bottom and roof can be rolled on).

The shortcomings of shaft stairs are the following:

  • shaft stairs are installed on a separate base plate;
  • stairs should be fastened to tank wall in several rows of radial stiffeners which cause undesirable stress concentration, especially in case of earthquakes.

Circular stairs meet Russian standards for tank design and have no shortcomings as specified for shaft stairs.

It is recommended to arrange circular platforms on perimeter of the roof in order to meet safety requirements and provide serviceability for the equipment installed on the fixed roof. In case of tanks without pontoon with capacity over 1000 m3 the platforms can be arranged on ¾ perimeter.
The passages of platforms can be made of expanded steel sheet, pressed or perorated sections or imported serrated galvanized grating.

Platform fencing is usually made of angle section; the hand-rail can be made of pipes upon request of the customer.

The constitutive elements include elements which ensure fulfilling additional requirements of the technological project of the tank regarding fire safety and ease of use.

Main constitutive elements

Lightning rods and grounding structures

Availability and type of fire protection devices which include foam fire fighting devices, cooling and lightning protection devices are determined in the technological part of tank project.

The Customer should specify type and quantity of foam generators, necessity in ring irrigation line, height and quantity of lightning rods and quantity of grounding devices in the Order for execution of KM project.

KM project includes design of platforms and flanges of foam generators on the wall, brackets for fixation of pipelines, lightning rods and grounding devices.

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