Extremely reinforced insulation of steel pipes - a reliable method of corrosion protection

One of the key problems of steel pipelines is the occurrence of corrosion.It occurs when exposed to moisture, aggressive soil, or stray currents. This problem is relevant for underground pipelines passing through liquid media. To solve this problem, highly reinforced insulation of steel pipes is used, the technology and materials of which depend on the operating conditions.

General description of surface treatment

The method involves applying a multilayer coating to the surface of steel pipes. This eliminates their contact with the external environment, and, as a result, the development of corrosion processes. Treatment can be performed during production or before installation of finished products. The main regulatory document for creating highly reinforced insulation (VUS) of steel pipes is GOST 9.602 2005.

Information on highly reinforced insulation technology:

• insulating materials – bitumen, polymer coatings;
• pipe diameter – from 57 to 830 mm, depending on processing technology;
• the purpose of the highways is to transport cold water, oil products, gas, sewage;
• working environment temperature – from -15 C to +40 C;
• methods of installing pipelines - underground, surface, underwater.

The essence of the method is the formation of several protective layers. For better adhesion, a thermal effect on the pipe occurs at different stages of application. Its surface is pre-treated - corrosion zones, painting, and old protective materials are removed. Dust is also removed.

Important - to ensure complete protection of the pipeline, it is necessary to apply reinforced insulation to the joints - couplings, sockets.

Requirements according to GOST 9.602 2005

The regulatory document describes the conditions for the formation of highly reinforced insulation, requirements for materials, and characteristics of the insulating layer. The technology is used for all types of pipelines laid in the ground. For gas pipelines there is a maximum pressure limitation - it should not exceed 1.2 MPa. Very reinforced insulation is used for the protection of underground tanks and steel communication structures.

The table indicates the operational and technical requirements for coatings of this type.

These parameters are controlled during the manufacturing process of products and their operation. The thickness is checked using thickness gauges or similar instruments without damaging the outer shell. During repairs, the integrity of the protective layer is restored. It is important that its characteristics match those of the rest of the coating.

Advice - after manual installation of insulation, 10% of the surface is checked. This is done at 4 points around the circle.

Details - overview of highly reinforced insulation materials

The technical and operational qualities of highly reinforced insulation depend on the selected materials and the technology of their use. When choosing, in addition to the degree of protection from moisture, additional factors are taken into account:

• complexity of installation;
• storage requirements;
• transportation requirements.

Each type of highly reinforced insulation material must be considered separately.

Polymers

Processing occurs during pipe manufacturing (in the factory) or in special preparatory workshops. To form the first layer, thermosetting resins are used that have a high adhesion to steel. Then additional coatings are applied. Roll-type materials and mastics are used.

Types of highly reinforced polymer insulation:

• two-layer - after mechanical and thermal treatment, a layer of primer (thermosetting resin) is applied to the pipe. A protective shell is then formed from extruded polyethylene;
• three-layer - a hot-melt polymer sublayer is installed on top of the primer. After this, a protective shell is applied. This increases the temperature range of use of the product;
• combined three-layer - the second protection zone after the primer is polyethylene tape with an adhesive base. Installed in 1 layer, thickness not less than 0.45 mm.

Advantages of using polymer materials:

• mechanical strength;
• reliability of sealing of steel pipes;
• the ability to perform repairs (restoration of the protective layer) in “field” conditions.

The disadvantage is the relatively high cost of processing.

Important - the total thickness of polymer-based insulation must be at least 1.8 mm.

Mastic (bitumen) coating

Belongs to the category of basic. It is formed in the factory or on premises before being sent to the installation site. For processing, a bitumen composition with polymer or rubber additives is used. It has increased heat resistance, elasticity, and stretchability.

However, due to low mechanical strength, it is necessary to install protective layers - kraft paper, reinforced fiberglass.

Classification of mastic (bitumen) highly reinforced insulation:

• tape The base is bitumen or asmol primer. A bitumen tape (2 mm) is installed on top of it. The outer protective layer is kraft paper or polymer wrap;
• mastic. Insulating mastic is applied to the bitumen or polymer-based primer. Fiberglass is used to form the protection;
• heat-shrinkable. The technology is used to repair pipelines on site. The material is heat-shrinkable with a layer of mastic. Inner side with adhesive base.

Mastic (bitumen) insulation of steel pipes is applied quickly, which makes it possible to quickly install pipelines. However, due to the weak mechanical strength of the protective layer, special requirements are imposed on the storage and transportation of pipes.

Important - for highways with a working environment temperature up to +130 C, a bitumen-rubber composition can be used. But for such cases, heat-resistant protective materials are chosen.

Combined VUS

To compensate for the shortcomings of the methods described above, a combined technology using bitumen and polymer layers has been developed. It is possible to apply very reinforced insulation at the pipe manufacturing stage, in preparatory workshops or on routes. This increases mechanical strength while maintaining moisture-proof characteristics.

The order of the layers in the combined highly reinforced insulation is:

1. Preparatory layer. A bitumen composition is used. In some cases, it is possible to use polymer-asmol components.
2. Basic protection. It is formed from polyethylene polymer-bitumen tape.
3. Outer shell. Polymer, minimum thickness 0.6 mm.

When choosing materials, their compatibility is taken into account. It is important that they have the same thermal expansion. Otherwise, delamination and leakage may occur. The introduction of new application technologies occurs only after testing.

The choice of method for forming highly reinforced insulation of steel pipes is influenced by operating conditions and technical requirements of the project. Depending on the location of the pipeline, various VSS technologies can be used.

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The video will complement our article.

Applying insulation to a pipe. Bitumen films.