The Principle and Insulation Details of Anti-corrosion Steel Pipes

First, the Principle of Anti-corrosion Steel Pipes
Coating anti-corrosion is a uniform, dense coating formed on the surface of rust-free metal steel pipes, which isolates them from various corrosive media. Steel pipe anti-corrosion coatings increasingly utilize composite materials or composite structures. These materials and structures must possess good dielectric properties, physical properties, stable chemical properties, and a wide temperature range.

External Wall Anti-corrosion Coatings: Types and application conditions of coatings for the outer walls of steel pipes. Internal Wall Anti-corrosion Coatings: This film is applied to the inner wall of the steel pipe to prevent corrosion, reduce frictional resistance, and increase usage. Commonly used coatings are amine-cured epoxy resins and polyamide epoxy resins, with a steel pipe coating thickness of 0.038 to 0.2 mm. To ensure a firm adhesion of the coating to the steel pipe wall,

Surface treatment of the inner wall of the steel pipe is necessary. Since the 1970s, the same materials have been used to coat both the inner and outer walls of steel pipes, allowing for simultaneous coating of both surfaces. Anti-corrosion and heat-insulating coatings are used on small- and medium-diameter heat transfer crude oil or fuel oil steel pipes to reduce heat loss from the steel pipes to the soil.

A composite layer of insulation and corrosion protection is added to the outside of the steel pipe. Rigid polyurethane foam is commonly used as the insulation material, and its applicable temperature range is within a certain range. To increase its strength, a high-density polyethylene layer is applied to the outside of the insulation layer to form a composite material structure, preventing groundwater from penetrating the insulation layer.

Second, what are the methods for heat insulation of anti-corrosion steel pipes?
Anti-corrosion steel pipes are a common type of steel pipe. To slow down and prevent corrosion and deterioration of the steel pipes under the chemical and electrochemical effects of internal and external media, or due to the metabolic activity of microorganisms, proper corrosion protection is necessary. Besides corrosion protection technologies for the transported media, most steel pipes transporting oil and natural gas are located in relatively complex soil environments, and the transported media are also corrosive. Therefore, the inner and outer walls of the steel pipes are likely to corrode. Once the steel pipe is corroded and perforated, it will cause oil and gas leaks, which will not only seriously pollute the environment but also cause fires and endanger human lives. Therefore, it is necessary to perform anti-corrosion work on steel pipes. However, there are actually many methods for insulating anti-corrosion steel pipes, and different methods must be selected according to different types.

1. Insulation Methods for Anti-corrosion Steel Pipes
This mainly uses uncertain insulation materials (such as expanded perlite, expanded frog stone, asbestos powder, asbestos fiber, and diatomaceous earth clinker, etc.), adding a certain amount of binder (such as cement, water glass, and refractory clay, etc.). Alternatively, a coagulant (such as sodium fluorosilicate or nepheline aminopyrine) can be added. The component ratio is selected, water is added, and the mixture is evenly mixed to form a shaped mud lump. This lump is then directly and evenly applied by hand. This application method is called the coating method for insulation.

2. Wrapping Insulation for Anti-corrosion Steel Pipes
① The wrapping insulation method mainly involves making the insulation material into rope or strip shapes and then directly wrapping it around the steel pipe that needs insulation.
② The main insulation materials used in daily life for this method include: slag wool felt, glass wool felt, straw rope, asbestos tape, etc.

3. Prefabricated Components of Anti-corrosion Steel Pipes for Thermal Insulation
① Prefabricated insulation structure for steel pipes. When the pipe diameter is DN≤80mm, a semi-circular pipe shell is used. If the pipe diameter is DN≥100mm, fan-shaped or trapezoidal tiles are used.
② The materials used in the prefabricated components are mainly foamed concrete, asbestos, slag wool, glass wool, expanded perlite, calcium silicate, etc.

4. Filling Method for Insulation of Anti-corrosion Steel Pipes
① If the insulation material is in bulk, this method can be used for removable insulation materials.
② During construction, round steel support rings are fixed to the steel pipe wall. The thickness of the ring is the same as the thickness of the insulation layer, and then the support rings are wrapped with iron sheets, aluminum sheets, or metal wire mesh for insulation material filling.
③ This filling method can use prefabricated hard arc bricks with porous material as the support structure. The spacing between them is about 900mm, just like plain weave metal wire mesh. According to the outer perimeter of the insulation layer of the steel pipe, the slag is machined by a circular machine to cover the surrounding of the support. The filling and insulation structure should be made of a metal protective shell as much as possible.