Regarding pipeline anti-corrosion

And how is anti-corrosion treatment generally applied inside valves?

http://bbs.hcbbs.com/thread-452858-1-1.html Some things are mentioned there

I would like to know how to prevent corrosion in heating pipes. Could you give some advice?

Heating pipes are generally coated with an external anti-corrosion paint, while internal coating for anti-corrosion on valves is used less frequently

What is usually done inside heating pipes?

For chemical industry pipelines, internal anti-corrosion treatment involves using ordinary carbon steel pipes as the base material. An inner lining made of plastics such as PE, PO, PP, F4, F40, UHMW-PE, etc., is applied; this combination offers the mechanical properties of steel pipes along with the advantages of plastics in terms of wear resistance, corrosion resistance, reduced scaling, and difficulty in supporting microbial growth. Such pipes are ideal for transporting various fluids, powders, slurries, gases, and particles, and they are widely used in industrial fields such as the chemical industry, mining, thermal power generation, water treatment, river dredging, port cleaning, and offshore engineering. 2. The lining rubber uses rubber with excellent properties such as corrosion resistance, wear resistance, and heat resistance as the lining layer. Taking advantage of the rubber’s unique characteristics such as high elasticity, high airtightness, impact resistance, wear resistance, weather resistance, radiation resistance, chemical resistance, and vibration absorption, it is compounded and vulcanized through a special process using high-performance adhesives. The resulting product boasts high wear resistance, resistance to acid, alkali, and salt corrosion, high temperature tolerance, reduced scaling, high bonding strength, low operating resistance, the ability to transport a wide range of media, a long service life, as well as energy and material savings. It can significantly reduce the impact wear caused by the transported media on the pipe walls, and is widely used in industries such as metallurgy, power generation, chemicals, petroleum, coal, and cement for pipeline equipment that transports media at temperatures ranging from -30°C to +150°C, in environments where both wear and corrosion occur. Commonly used external anti-corrosion methods include 3PE coated steel pipes, epoxy coal tar pitch coated steel pipes (with one layer of fabric and two layers of paint, two layers of fabric and three layers of paint, one layer of fabric and three layers of paint, two layers of fabric and four layers of paint, three layers of fabric and five layers of paint, etc.), IPN8710 for internal anti-corrosion in drinking water pipelines, and FBE single- or double-layer epoxy powder coated steel pipes. When insulating the heating pipes, corrosion protection is also provided. Commonly used types include polyethylene-clad polyurethane foam insulation pipes, pre-fabricated directly-buried insulated steel pipes, steel-in-steel directly-buried insulated pipes, and foam-insulated pipe fittings. Polyethylene-clad polyurethane foam insulation pipe – First layer: Working steel pipe layer. Depending on design requirements and customer specifications, seamless pipes (GB8163-87), spiral-welded pipes (GB9711-88; SY/T5038-92), and straight-seam welded pipes (GB3092-93) are generally selected. After being treated with an advanced shot blasting process for rust removal, the surface of the steel pipe can reach the Sa2 grade as specified in the GB8923-1988 standard, while the surface roughness can reach R=12.5 microns in accordance with the GB6060.5-88 standard. Second layer: Polyurethane insulation layer – This is created by using a high-pressure foaming machine to inject the raw liquid of rigid polyurethane foam directly into the cavity formed between the steel pipe and the outer protective layer. That is the commonly known “tube-in-tube foaming process”. Its functions are first, to prevent water leakage; second, to provide insulation; and third, to support the weight of the heating network. When the temperature of the medium being transported is between -50°C and 120°C, rigid polyurea foam plastic is used as the insulation layer. Third layer: High-density polyethylene protective layer – Pre-made black (yellow) plastic pipes with a certain wall thickness; its functions are to protect the polyurethane insulation layer from mechanical damage and hard objects, as well as to provide corrosion and water resistance. Steel-clad steel insulated pipes: The insulation structure of such pipes can be divided into two types based on the manner of sliding – internal sliding and external sliding. 1. Internal sliding type: The insulation structure consists of the working steel pipe, aluminum silicate, a drag-reduction layer, microporous calcium silicate, an insulating layer, stainless steel fastening strips, an aluminum foil reflective layer, a polyurethane insulation layer, an outer steel pipe, and an outer anti-corrosion layer (this type is hardly used any more). 2. External sliding type: The insulation structure consists of a working steel pipe, glass wool insulation layer, aluminum foil reflective layer, stainless steel fastening straps, sliding guide brackets, air insulation layer, an outer protective steel pipe, and an outer anti-corrosion layer. 1. Anti-corrosion layer: Protects the outer steel pipe from corrosion by corrosive substances, thereby extending its service life. 2. Outer protective steel pipe: Protects the insulation layer from erosion by groundwater, supports the working pipe, and can withstand certain external loads to ensure the proper functioning of the working pipe. 3. Glass wool insulation layer, air insulation layer: To maintain the temperature of the medium and ensure that the surface of the outer protective tube remains at normal temperature. 4. Aluminum foil reflective layer: Prevents organic foam material from entering the inorganic, rigid, high-temperature resistant layer ； Reflects some of the heat from the high-temperature layer. 5. Inorganic rigid insulation layer: resistant to high temperatures, ensures an appropriate interface temperature with the organic insulation layer, and prevents the foam from carbonizing. 6. Stainless steel fastening straps and sliding guide brackets: Ensure free movement of the working steel pipe due to thermal expansion and contraction. 7. Working steel pipe: Ensure normal flow of the transported medium

Pipeline anti-corrosion generally refers to the rust removal and painting (spraying) of pipelines, whether they are process pipelines or those used for circulating water, heating, etc. It usually refers to the area outside the pipe; cleaning, flushing, and even degreasing are required inside the pipe.

The external anti-corrosion treatment for heating pipes generally involves rust removal followed by the application of high-temperature resistant rust-proof paint. It seems there’s no special treatment inside generally.