Internal coating or lining of pipes is a widely used technology to protect steel pipelines from corrosion and to reduce flow friction. This method is essential in long-distance transport lines, including those for oil, gas, fuel, condensate, chemicals, potable or industrial water, sewage, outfall pipes, and drilling pipes.
Depending on the specific transport medium, its aggressiveness, and other requirements, various types of coatings can be applied to provide the necessary protection:
- Cold or Hot Epoxies: These coatings can be solvent-based or solvent-free, offering flexibility depending on the conditions of the pipeline and the substance being transported.
- Fusion Bonded Epoxy (FBE): A powder coating that provides excellent corrosion resistance, often used in demanding pipeline environments.
- Polyurethanes: Ideal for applications that require durable, high-performance coatings to withstand extreme conditions.
How It Works
Internal pipe coating is typically applied in one or more layers, depending on the pipe coating standard or manufacturer recommendations. Special primer layers may be required in certain cases. To ensure proper adhesion, the pipe surface must be clean, dry, and free from contaminants like dust, rust, and oil. This is achieved by using the following processes:
- Internal Washing: Pipes may undergo internal washing to further clean the surface, particularly if the pipe has been exposed to dirt, oil, or grease.
- Pre-heating: Pipes can be pre-heated to ensure proper coating application and faster curing.
- Abrasive Blasting: To prepare the pipe surface for coating, it must be abrasive blasted to remove any impurities.
Once the coating is applied, post-heating can be used to speed up the curing process, ensuring the coating hardens properly and adheres securely to the pipe surface.
Key Equipment and Full Scope
Selmers provides a comprehensive range of equipment for internal pipe coating, including:
- Internal Wash System: The internal pipe wash system is used to wash the internal pipe surface from e.g. dust or sand, or for a pre-cleaning step to degrease the surface.
- Internal Heating System: A gas-fired heating system is used to preheat pipes before blasting and coating, which helps dry them and prepares them for the application.
- Internal Blasting System: This system uses dry-grit blast lances based on either mechanical or pneumatical technology to effectively remove contaminants, such as rust and mill scale, ensuring a clean surface for coating adhesion. It also includes an optional alkaline wash system for cleaning sand, mud, oil, and grease when necessary.
- Blow-Out System: This system efficiently removes dust and loose abrasive particles from the pipe after blasting, ensuring the surface remains clean and ready for coating.
- Internal Pipe End Masking System: This is a device that applies a temporary tape on the pipe and in order to keep the pipe end clean for later welding.
Once the pipe surface is properly prepared, the following systems are used for coating and curing:
- Internal Coating System: This includes equipment for applying liquid epoxy, polyurethane, or FBE powder coatings to the inside of the pipes.
- Curing Equipment: A curing chamber system, often supported by a chain conveyor, is used to properly cure the coatings, ensuring durability and performance.
- Internal Marking & Inspection Station: For quality control, the system includes stations for marking and inspecting the coated pipes.
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