Tank pontoons

Vertical tanks pontoons are installed to reduce evaporating from the oil level, which can cause its quality deteriorates during reforming or transportation. They are located between the stationary roof and the petroleum product. When flammable liquids are stored, evaporating and harmful flammable gases enter the atmosphere, which leads to possible ignition and economic losses of oil operator.

The level of losses depends on the operating conditions (temperature, product properties, pressure) and operating parameters (the number of turnover, the presence of trapping devices, the ratio of the tank capacity and its fullness). All this leads to economic losses of oil operator. The solution is a metal or aluminum pontoon, which is located between the roof and the surface of the operational product.

Advantages of using Vertical Tanks pontoons

• reduce of evaporation loss of oil
• provide explosion and fire safety
• decrease of the negative environmental impact from harmful gases entering the air
• they are installed both in the newly constructed tank and in the already used
• preservation of quality of oil products

Pontoons: types and structural designs

The Saratov Reservoir Plant manufactures various types of pontoons depending on operating conditions and requirements to their design. Each type has the same tightness and unsinkability and differs only in design.

A typical pontoon design has a thin-walled floating central disk and a peripheral ring that rests on pillars with cylindrical floats. The number of floats should be 100% unsinkable. The floats are submerged in the stored product by less than 40%. The diameter is calculated for the diameter of the shell - not less than 90% or 400 mm less. Free space is formed between liquid urface and the flooring, which is filled with petroleum vapor. In order that it does not go into the atmosphere, a hydraulic seal or sealing gates are installed between the shell and the peripheral ring to maintain tightness. When loading or emptying of tank the pontoon go up/ falls. After full emptying, the pillars rest on the bottom, forming a space for the installation of ventilation pipes, siphons, manways.

The Saratov Reservoir Plant produces the following types of pontoons:

• single-deck
• double-deck
• float type
• multilayered

Single-deck pontoons

They can be rolled or panel. The rolled single-deck pontoons are a central single-layer membrane (or deck) and circular ducts around the perimeter. Panel single-deck pontoons are a set of rectangular boxes, which are fastened together inside the tank with the help of sheet flooring. The overlapped assembly ensures their tightness. The latter type is traditionally installed in a large tank with a capacity of 5000 m³.

Single-deck rolled pontoon	Single-deck panelled pontoon

Double-deck pontoons

They are a flooring plates, consisting of the necessary number of boxes around the perimeter.

Aluminum pontoons

They consist of a peripheral ring, to which floats are attached. The floats are mounted on the legs connected to each other. A gas-tight flooring consisting of aluminum bands is placed on the frame around the perimeter.

Double-deck pontoon	Floating pontoon

Multilayered pontoons

They are a membrane covered with polyurethane foam and lined with a metal or polyurethane "jacket".

Manufacture of tank pontoons

Only light metals (aluminum and stainless steel) are used for production, which can provide a float and unsinkability. Aluminum is a light and stable metal to liquid hydrocarbons, which makes it possible to use aluminum pontoons in 80% of cases.

Pontoons made of stainless steel are corrosion-resistant and are operated with highly aggressive liquids. If it adversely affects aluminum, the parts in contact with the operational product are made of stainless steel. The latter option is the most economical compared to fully made of stainless steel.

The basic requirements to the design and manufacture of pontoons are set out in:

• GOST 31385-2016 "Vertical cylindrical steel tanks for petroleum products. General technical specifications"
• STO-SA-03-002-2009 "Rules for design, fabrication and erection of vertical cylindrical steel tanks for petroleum products"

In accordance with them our specialists calculate the pontoon:

• it should not be skewed and rotated (guides are used for this)
• thickness of steel elements - 3-7 mm (excluding corrosion margin)
• pontoon floatability should be ensured in case of depressurization: for one-deck - two boxes or one box and central part, for double-deck - three boxes, for float - less than 10% of floats
• floatability is calculated based on the weight ratio (=2) and the density of the product (0.73 t/m³)

Certificates and approval documents for pontoon design and manufacture are listed here.

Installation of pontoons

Pontoon assembling are carried out in conformity with VSN 311-89 “Vertical steel tanks erection for petroleum products storage with the capacity from 100 to 50000 м³”.

Installation in an already operated or newly constructed tank is fairly simple and is carried out through the manway in the first tank course. Usually the installation takes 3-4 days.

The installation of the pontoon is possible after unrolling of the bottom and in parallel with the unrolling of the shell: first peripheral boxes are mounted, welded together, and then the central disk is placed. Both parts are attached to the bottom on the base plate for the columns. Then the verticality of the pontoon is checked, the tightness test is performed by filling tank with water. After the test, the final welding work is carried out.

Advantages of our own make pontoons

• compatibility with all liquid media
• reserve buoyancy is 100%
• high grade of manufacture
• no anticorrosion protection required
• possibility to height adjustment of the support legs and the pontoon canting angle, depending on the bottom slope

The price of a pontoon is formed on the basis of:

• tank diameter
• condition of operational fluids
• operating conditions
• requirements to additional equipment configuration (manways, siphon drain, samplers, ventilation and installation branch pipes, breathing valves, seals, gaskets, etc.)

We perform packaged supply of vertical tanks pontoons on special terms and conditions.