What is the Standard for 3LPE Coating?
In recent years, with the all over of world use of oil, gas and water transportation pipelines globally, 3LPE anti-corrosion has become increasingly popular in international projects. The standard for 3LPE anti-corrosion coating is also the most concerned point for the purchasers and project engineers. A 3LPE anti-corrosion layer that meets the standard directly determines the usage of buried steel pipe pipelines and the safety of the project.
But, what is 3LPE Coating?
3LPE Coating is three-layer polyethylene, the three-layer anti-corrosion coating applied to the outer surface of buried steel pipes is the most commonly used for oil and gas pipelines as well as water pipelines.
The whole 3LPE coating materials of three tightly connected layers applied in factory production lines.
The first layer is fusion bonded epoxy, also called FBE primer, which sticks firmly to the cleaned steel pipe surface and stops electrochemical corrosion.
The second layer is adhesive. This layer acts as a connecting bridge. It bonds the FBE layer and outer polyethylene layer to avoid peeling between different layers of 3LPE coating.
The third layer is polyethylene outer layer, also called HDPE. This thick outer shell protects the whole 3LPE coating from impact, scratch, soil pressure and water penetration during transport, burying and long-term underground service. Compared with single-layer coatings, complete 3LPE coating balances anti-corrosion performance and mechanical protection, so it becomes the preferred choice for buried pipelines in most regions across the world.
Many buyers cant struggle the difference between 3LPE coating and FBE coating. The biggest difference is layer quantity. FBE coating is only one single-layer coating, while 3LPE coating is a three-layer composite system built based on FBE coating. Regarding physical protection, FBE coating forms a thin film on surface of steel pipes. It performs well against chemical corrosion, but lacks strong resistance to impact and abrasion. If steel pipes touch sharp stones during installation, FBE coating is easy to break. But, 3LPE coating adds adhesive and thick polyethylene outside the FBE base layer. The outer polyethylene greatly improves anti-impact ability. When it comes to working temperature, standard 3LPE coating fits pipelines running below 80°C. FBE coating can work steadily under higher temperature conditions. From construction cost, FBE coating needs simpler production equipment and lower overall cost. 3LPE coating requires complex continuous production technology, leading to higher manufacturing investment. In construction projects, engineers choose FBE coating for high-temperature pipelines or projects with strict budget limits, and choose 3LPE coating for pipelines buried in rocky soil or areas with high mechanical damage risks.
Then, what material is used for pipe coating?
The materials used for pipe coating are the key to whether the pipes can be protected from corrosion, especially for the raw materials of 3LPE coating and FBE coating. For the standard 3LPE coating, its three-layer structure is composed of three main materials: the bottom layer uses epoxy powder, which is used for FBE coating. This powder melts and solidifies on the heated steel surface, forming a dense anti-corrosion film layer; the middle layer of 3LPE coating uses adhesive, which can be fused with epoxy resin and polyethylene under controlled temperature conditions; the outer layer selects polyethylene and adds an appropriate amount of carbon black to enhance the anti-aging performance. The independent FBE coating only uses thermosetting epoxy powder, supplemented by curing agents and functional additives. All qualified raw materials for 3LPE coating and FBE coating must pass the material qualification tests stipulated by international standards before the large-scale coating operation on steel pipes is carried out.
Some buyers will ask: What is FBE coating in a pipeline?
The full name of FBE coating is fused epoxy coating, which is a classic single-layer anti-corrosion coating widely used for steel pipes. The construction workers spray the dry epoxy powder onto the preheated surface of the steel pipe. After the powder melts and flows, it solidifies to form a continuous and pore-free coating film. FBE coating has stable chemical adhesion with the steel and possesses excellent cathodic stripping resistance, which is a key technical indicator for underground pipeline anti-corrosion. FBE coating can be used as the outer coating of the pipeline or as an inner lining. In many cases, FBE coating can be used alone, and it is also an indispensable base layer in the complete 3LPE coating system. If the qualified FBE primer is lacking, the entire 3LPE coating system will face potential risks such as delamination and early failure. Although FBE coating also has anti-corrosion performance, in harsh environments, a single-layer coating cannot meet the anti-corrosion requirements, and a 3-layer anti-corrosion coating still needs to be selected.
After understanding coating types and materials, that us come back to the main question: What is the ISO standard for coating, especially for 3LPE coating?
The main international ISO standard for 3LPE coating is ISO 21809-1:2018. The full name of this standard covers the outer polyolefin coating for buried and underwater steel pipelines in the oil and gas industry, including 3LPE coating and 3LPP coating. This ISO standard has strict requirements for surface treatment of steel pipes, raw material requirements, coating thickness, construction techniques, testing methods, as well as the impact resistance and scratch resistance of 3LPE coating products, to ensure the stability of the quality of 3LPE coating products. For independent FBE coating, the corresponding ISO standard is ISO 21809-2. Besides ISO standards, European projects generally adopt DIN 30670 as the standard for 3LPE coating. Many national standards also base on ISO 21809-1 to formulate local technical specifications. When customers ask "What is the standard for 3LPE coating?", suppliers should confirm before manufacturing the pipelines whether the project requires using ISO 21809-1:2018 or other regional standards.
The work step for SLPE
Steel pipe blasting → Induction heating → FBE powder spraying → Adhesive extrusion → PE extrusion → Cooling
Shot blasting pretreatment
Steel pipes are blasted to Sa 2.5 grade to remove rust and form anchor texture, ensuring coating adhesion.
Induction preheating
The cleaned pipe is heated to 190–230°C for FBE powder melting.
Electrostatic FBE powder spraying
Epoxy powder is electrostatically sprayed onto hot steel pipe, forming the first anti-corrosion layer (FBE coating).
Adhesive & PE extrusion wrapping
Before FBE fully cures, adhesive and outer polyethylene layer are extruded and wrapped continuously to complete the 3LPE coating system.
Water cooling & online inspection
If you want to know the information about 3LPE Anti-corrosion Equipment, please check below news.
