Bitumen in Pipe Coating

Bitumen in pipe coating related to the protective coating of the external surfaces of steel pipes with petroleum bitumen or coal tar materials and the internal lining of steel pipes with bitumen materials (except steel pipes for the transport of drinking water). The Contractor shall provide all necessary machinery, tools and manpower and perform the operations mentioned in accordance with these specifications. This type of coating has been used for a long time to protect the inner and outer walls of steel pipes and has been perfected over time in terms of deficiencies and defects. The coating is applied both in the factory and on the job site.

It is necessary to clarify that when applying coal tar coating, due to the adverse effects on the lungs and skin of workers who work with it, health and safety regulations must be fully observed. To apply the coating, first the pipe surface is completely cleaned to the desired degree by sandblasting or shot blasting until the metal surface of the pipe turns a dull gray color. After cleaning and preparing the pipe surface, a suitable primer layer is sprayed on the pipe surface and left to dry for a while.

Bitumen Applying process for coating

Hot coating of steel pipes with bitumen or tar materials Then the pipe is pushed forward over rollers with a rotary motion and at the same time, bitumen or molten tar is poured onto the pipe surface from the bitumen pouring mouth. The thickness of the bitumen layer is controlled by adjusting the rotary and axial motion of the pipe and the amount of bitumen pouring. Simultaneously with the bitumen pouring, one or two layers of fiberglass reinforcing tape (inner tape) are wound around the pipe in a spiral shape. This tape is wound with the appropriate amount of tension in such a way that it is embedded the bitumen in pipe coating.

Due to the porous nature of the tape, the bitumen passes through its pores and the tape is completely impregnated with bitumen. At the same time, a layer of bitumen-impregnated tape (outer tape) is wrapped around it with the appropriate amount of tension. When applying the coating, it is necessary to have two bitumen springs, one before the inner tape and one before the outer tape. To perform the internal coating of the pipes, after cleaning the inner surfaces of the pipe (similar to the outer surfaces of the pipe), a suitable primer layer is applied to the surface of the pipe.

During the lining process, bitumen is sprayed onto the inside of the pipe through a conveyor pipe while the pipe is rotating. Reinforcing strips are not used for the inner lining of the pipes, and the thickness of the lining layer is controlled by adjusting the amount of bitumen applied and the longitudinal movement of the conveyor pipe. 2-2-5 Standards and Reference.

Bitumen in pipe coating standards

Bitumen in pipe coating has technical specification is for the application of external coating and internal lining of underground steel drainage pipes with bitumen or tar materials prepared by hot method and includes cleaning and preparation of the pipe surface, application of primer on the pipe surface, preparation of bitumen or tar materials, application of external coating and/or internal lining of the pipe, repair of the coating and tests required for the coating.

If these technical specifications are incomplete or unclear in the context of the application, reference should be made in the first instance to the standards approved by the Iranian Standards and Industrial Research Organization, publications of the country’s Management and Planning Organization, or the relevant sections of the latest editions and revisions of the international standards JIS, DIN, BS, AWWA, ISO, as described below:

A – ISO 5256 Bitumen or tar coating for external and internal protection Underground steel pipes.

B – AWWA C203 Coal tar coating for external and internal protection of steel pipelines.

C – BS 4147 Petroleum bitumen coating for protection of metal surfaces

D – DIN 30673 Petroleum bitumen coating for external and internal protection of steel pipes.

E – JIS G 3491 Petroleum bitumen coating for internal and external protection of steel pipelines. The materials required for coating include bitumen or tar, primer, internal reinforcing tape made of fiberglass, and external mechanical protection tape made of fiberglass or other types impregnated with bitumen or tar.

To prepare the materials, it is recommended to first refer to the standards approved by the Standards and Industrial Research Institute of Iran (ISIRI) and the publications of the country’s Management and Planning Organization, and then refer to the aforementioned international standards.