Boiler tubes include medium-pressure boiler tubes and high-pressure boiler tubes, which are generally manufactured using seamless technology instead of welded steel pipes.
Boiler tubes materials and standards
The standards and materials of steel pipes include carbon steel, alloy steel and stainless steel materials.
Carbon steel: ASTM/ASME A/SA 106, ASTM A179, ASTM A192, ASTM/ASME A/SA 210, ASTM A333 Gr 1, 6, 7 to Gr 9.
Alloy steel: ASTM/ASME A/SA 213T1, T2, T5, T9, T11, T12, T22, T91, T92; ASTM A335 P1, P2, P5, P9, P11, P12, P22, P91, P92.
Stainless steel: ASTM A268, ASTM A213, TP304/L, TP316/L, 310S, 309S, 317, 317L, 321, 321H and duplex stainless steel materials, etc.
Common sizes: outer diameter from 6 mm to 1240 mm, thickness from 1 mm to 50 mm.
Type: straight boiler tube, U-shaped boiler steel tube for tube bundle exchanger.
The boiler tube size range is in accordance with different ASTM standards as required. Such as ASTM A106 or ASTM 179, 192 etc. But most boiler pipes are smaller in size, usually less than 1 1/2" (1/4", 1/2", 3/4", 1", and 1 1/2" in outside diameter. Next in size are 2", 2 1/2", 3", and up to 4".
Differences between medium and high pressure boiler tubes
Depending on the working temperature, medium-pressure or high-pressure boiler tubes should be used. Usually divided into the following situations:
1. Generally, the working temperature of boiler tubes is lower than 450℃. Medium-pressure boiler tubes are mainly produced by hot rolling or cold drawing.
2. High-pressure boiler tubes are often used under high temperature and high pressure conditions. Under the action of high-temperature flue gas and steam, the pipes will be oxidized and corroded. High-pressure boiler tubes are required to have high lasting strength, anti-oxidation and corrosion performance, and good structural stability.
The manufacturing method of medium and high pressure boiler tube is the same as that of seamless steel pipe, but attention should be paid to several key manufacturing processes: precision drawing, surface brightening, hot rolling, cold drawing, hot expansion.
Boiler tubes heat treatment methods
Heat treatment is a method of changing the physical properties of high pressure boiler tubes by heating and cooling. Heat treatment can improve the microstructure of high pressure boiler tubes to meet the required physical requirements. Toughness, hardness and wear resistance can be obtained through heat treatment. In order to obtain these characteristics, quenching, annealing, tempering and surface hardening are required.
1. Quenching
Hardening, also known as quenching, is to uniformly heat the high-pressure boiler tube to an appropriate temperature, then quickly immerse it in water or oil for rapid cooling, and cool it in the air or in the solidification zone. So that the high-pressure boiler tube can obtain the required hardness.
2. Tempering
The high-pressure boiler tube will become brittle after quenching. The stress generated by quenching will cause the tapping of the high-pressure boiler tube to break. The tempering method can be used to eliminate the brittleness. Although the hardness of the high-pressure boiler tube is reduced slightly, the toughness can be improved and the brittleness can be reduced.
3. Annealing
Annealing is a method to eliminate stress in high-pressure boiler tubes. The annealing method is to heat the steel to a critical temperature, then put dry ash, lime, asbestos or seal it in a furnace and slowly cool it down.
Basic methods of rust removal
1. Cleaning
Solvents and emulsions are used to clean the surface of high-pressure boiler pipes to remove oil, grease, dust, lubricants and similar organic matter, but dust, oxide scale, welding flux, etc. on the surface of the pipes cannot be removed. Therefore, it can only be used as a supplementary means in anti-corrosion production.
2. Tools
Tool rust removal mainly uses tools such as wire brushes to polish the surface of high-pressure boiler tubes, which can remove loose or warped oxide scale, rust, welding slag, etc. Manual tools can reach SA2 level, and power tools can reach SA3 level. If iron oxide scale is attached to the surface, the anchoring depth required for anti-corrosion construction cannot be achieved.
3. Pickling
High-pressure boiler tubes are generally pickled by chemical or electrolytic methods.
4. Spray rust removal
Spray rust removal can not only completely remove rust, oxides, and dirt, but also the high-pressure boiler tube can achieve the required uniform roughness under the impact and friction of the abrasive. Spray rust removal can not only expand the physical adsorption amount on the surface of the high-pressure boiler tube, but also enhance the mechanical bonding force between the anti-corrosion layer and the pipe surface, so spray rust removal is an ideal method for pipeline corrosion rust removal.
Read more: What are the Common Materials for Seamless Boiler Tubes?
Boiler tubes materials and standards
The standards and materials of steel pipes include carbon steel, alloy steel and stainless steel materials.
Carbon steel: ASTM/ASME A/SA 106, ASTM A179, ASTM A192, ASTM/ASME A/SA 210, ASTM A333 Gr 1, 6, 7 to Gr 9.
Alloy steel: ASTM/ASME A/SA 213T1, T2, T5, T9, T11, T12, T22, T91, T92; ASTM A335 P1, P2, P5, P9, P11, P12, P22, P91, P92.
Stainless steel: ASTM A268, ASTM A213, TP304/L, TP316/L, 310S, 309S, 317, 317L, 321, 321H and duplex stainless steel materials, etc.
Common sizes: outer diameter from 6 mm to 1240 mm, thickness from 1 mm to 50 mm.
Type: straight boiler tube, U-shaped boiler steel tube for tube bundle exchanger.
The boiler tube size range is in accordance with different ASTM standards as required. Such as ASTM A106 or ASTM 179, 192 etc. But most boiler pipes are smaller in size, usually less than 1 1/2" (1/4", 1/2", 3/4", 1", and 1 1/2" in outside diameter. Next in size are 2", 2 1/2", 3", and up to 4".
Differences between medium and high pressure boiler tubes
Depending on the working temperature, medium-pressure or high-pressure boiler tubes should be used. Usually divided into the following situations:
1. Generally, the working temperature of boiler tubes is lower than 450℃. Medium-pressure boiler tubes are mainly produced by hot rolling or cold drawing.
2. High-pressure boiler tubes are often used under high temperature and high pressure conditions. Under the action of high-temperature flue gas and steam, the pipes will be oxidized and corroded. High-pressure boiler tubes are required to have high lasting strength, anti-oxidation and corrosion performance, and good structural stability.
The manufacturing method of medium and high pressure boiler tube is the same as that of seamless steel pipe, but attention should be paid to several key manufacturing processes: precision drawing, surface brightening, hot rolling, cold drawing, hot expansion.
Boiler tubes heat treatment methods
Heat treatment is a method of changing the physical properties of high pressure boiler tubes by heating and cooling. Heat treatment can improve the microstructure of high pressure boiler tubes to meet the required physical requirements. Toughness, hardness and wear resistance can be obtained through heat treatment. In order to obtain these characteristics, quenching, annealing, tempering and surface hardening are required.
1. Quenching
Hardening, also known as quenching, is to uniformly heat the high-pressure boiler tube to an appropriate temperature, then quickly immerse it in water or oil for rapid cooling, and cool it in the air or in the solidification zone. So that the high-pressure boiler tube can obtain the required hardness.
2. Tempering
The high-pressure boiler tube will become brittle after quenching. The stress generated by quenching will cause the tapping of the high-pressure boiler tube to break. The tempering method can be used to eliminate the brittleness. Although the hardness of the high-pressure boiler tube is reduced slightly, the toughness can be improved and the brittleness can be reduced.
3. Annealing
Annealing is a method to eliminate stress in high-pressure boiler tubes. The annealing method is to heat the steel to a critical temperature, then put dry ash, lime, asbestos or seal it in a furnace and slowly cool it down.
Basic methods of rust removal
1. Cleaning
Solvents and emulsions are used to clean the surface of high-pressure boiler pipes to remove oil, grease, dust, lubricants and similar organic matter, but dust, oxide scale, welding flux, etc. on the surface of the pipes cannot be removed. Therefore, it can only be used as a supplementary means in anti-corrosion production.
2. Tools
Tool rust removal mainly uses tools such as wire brushes to polish the surface of high-pressure boiler tubes, which can remove loose or warped oxide scale, rust, welding slag, etc. Manual tools can reach SA2 level, and power tools can reach SA3 level. If iron oxide scale is attached to the surface, the anchoring depth required for anti-corrosion construction cannot be achieved.
3. Pickling
High-pressure boiler tubes are generally pickled by chemical or electrolytic methods.
4. Spray rust removal
Spray rust removal can not only completely remove rust, oxides, and dirt, but also the high-pressure boiler tube can achieve the required uniform roughness under the impact and friction of the abrasive. Spray rust removal can not only expand the physical adsorption amount on the surface of the high-pressure boiler tube, but also enhance the mechanical bonding force between the anti-corrosion layer and the pipe surface, so spray rust removal is an ideal method for pipeline corrosion rust removal.
Read more: What are the Common Materials for Seamless Boiler Tubes?
