Internal coating of the Pipes helps to enhance the corrosion resistance ability of pipes, improves the flow, and also helps to reduce deposit formation. There different types of pipe internal coating, such as Fusion Bonded Epoxy (FBE) Coating and Glass flake Coatings.
1. Fusion Bonded Epoxy Coating
FBE is a type of a high-performance coating that is made by anti-corrosion powder for average operating temperatures. This coating is generally suitable for temperatures up to 80 °C.
FBE Coating Application Procedure
Visual examination is a must before blast cleansing to check the appearance of oil or grease. The surface of the pipe has to be entirely cleaned by blast cleaning to remove rust, scale, or any other unwanted particles. This offers a rugged surface finish. The roughness value required in this type of coating is 50 – 100 microns. After blast cleaning, the internal surfaces of pipes are painted by using a spray gun. This helps to spread the coat on the heated pipe at a steady speed. The pipe continually rotates in its longitudinal axis. The powder melts and converts into a liquid after arriving in connection with the heated surface. This liquid FBE coating moves onto the pipe’s surface and quickly becomes a solid layer. This is the process of Fusion Bonding.
Advantages of FBE Coating
- This coating is suitable for higher temperatures.
- This coating offers corrosion resistance.
- It is suitable to apply on pipes with different diameters between 2” and 48”.
- It is perfect for a wide array of thicknesses.
- It offers chemical resistance under soil conditions and high impact resistance.
Limitations of FBE Coating
- The highest life of the pipes with FBE coating is 12 years, and the highest plant design life is 25 years. It is required to replace piping once.
- It has an intricate design.
- Applicators are not easily available.
2. Internal Glass Flake Coating
It is also known as Chemflake/ Belzona coating, which is as per PCS – 8 of SP-1246. This type of coating is generally suitable for up to 93 °C working temperature. Internal glass flake coating is suitable for bigger pipe sizes. It is generally carried out in the flanged pipe spool to join non-flanged pipe spools.
Internal Glass Flake Coating Application
These are the steps for applying or using internal glass flake coating:
- Cleaning: It is done by applying the blast cleaning method, which maintains a roughness value from 75 to 130 micron.
- Spray: Spray is done by standard airless spray equipment.
- Brush:; It is recommended to stripe coating and also for coating small areas. To achieve the defined dry film thickness, it should be done with proper care.
- Curing: One coat needs about 24 hr to get a completely dry coat.
Advantages of Internal Glass Flake Coating
- It offers excellent resistance against chemical and solvent
- Good adhesion and weather properties
- It has low permeability
- This coating has outstanding finish detention.
Limitations of Internal Glass Flake Coating
- This coating is temperature and pressure-dependent, which is suitable only for a maximum of 10 bar pressure
- It is not suitable to use with caustic fluids or slurries
- It can cause skin soreness
- This coat needs recoating intervals, and chalking is a time-consuming process
- It is very costly and applied only for fewer spools
- The design life can be only up to 3 – 4 years