Fluid pipes are pipes specially used for conveying media with fluid properties.
Medium with fluid properties, in addition to liquid media such as water, oil, and solution, solid media such as cement, grain, and coal powder can also flow under certain conditions.
The fluid tube can be made of steel, copper, titanium and other non-ferrous metals, or even plastic and other non-metallic materials.
The fluid pipe must have a hollow cross-section, and it can also be square, triangular or any other shape. Some equipment is restricted by conditions, and rectangular pipes must be used, but most still use round pipes. The round tube has the smallest perimeter/area ratio in all geometric sections, that is, the largest internal section can be obtained under the same amount of material.
Steel pipes are also an indispensable material for various conventional weapons. Gun barrels and barrels are all made of steel pipes. Steel pipes can be divided into round pipes and special-shaped pipes according to different cross-sectional area shapes. Because the circle area is the largest under the condition of equal circumference, the circular pipe can transport more fluids, and is widely used to transport oil, natural gas, gas, water and certain solid materials.
In addition, when the ring section bears internal or external radial pressure, the force is relatively uniform. Therefore, most steel pipes are round pipes. However, round pipes also have certain limitations. For example, under flat bending conditions, round pipes are not as strong as square and rectangular pipes. Some agricultural machinery frameworks, steel and wood furniture, etc. often use square and rectangular pipes. According to different purposes, special-shaped steel pipes with other cross-sectional shapes are required. (Remarks: The current technology continues to improve. Fluid steel pipes may not necessarily be seamless, but may also be seamless steel pipes. This process has been approved for use in low and medium pressure boilers and fluid pipelines. Customers must order fluid steel pipes in the industrial contract. It indicates that the welded pipe is seamless, and the fluid steel pipe includes the steel pipe of these two processes, but the delivery price is different)
Due to its low cost and high strength, steel pipes are widely used in fluid transportation in modern society. According to its production process, steel pipes are divided into two categories: seamless steel pipes and welded pipes. Among them, welded pipes are divided into high frequency straight seam welded pipes (ERW pipe), spiral welded pipes (SSAW pipe), submerged arc welded pipes (UOE/LSAW), etc. In the past, seamless steel pipes were traditionally used for fluid pipes. With the development and progress of material science, forming technology, and unit equipment, welded pipes have been greatly developed. Welded pipes have the advantages of better wall thickness uniformity, higher precision, less energy consumption, and higher production efficiency than seamless pipes. The demanding oil and gas pipeline (API standard) used to be almost 100% seamless pipes. Today, in the United States, More than 95% of developed countries in Japan and Europe have been replaced by welded pipes.
When welded pipe is used as a fluid pipe, it has different requirements from ordinary steel pipe:
1. Welding seam is not allowed to leak. For welded pipes required by APIs, ultrasonic flaw detection and water pressure test are also required for the weld of each welded pipe;
2. For transporting corrosive chemical solutions, all steel pipes must be treated with internal corrosion protection;
3. All fluid pipes need to remove internal burrs to reduce fluid transport resistance.
①Generally, the temperature of boiler tubes is below 450℃. Domestic tubes are mainly made of #10 and #20 carbon steel hot-rolled tubes or cold-drawn tubes.
② High-pressure boiler tubes are often in high temperature and high pressure conditions when used. The tubes will be oxidized and corroded under the action of high-temperature flue gas and water vapor. The steel pipe is required to have high enduring strength, high oxidation and corrosion resistance, and good organizational stability.
①General boiler tubes are mainly used to make water wall tubes, boiling water tubes, superheated steam tubes, superheated steam tubes for locomotive boilers, large and small smoke tubes and arched brick tubes.
②High-pressure boiler tubes are mainly used to manufacture superheater tubes, reheater tubes, air ducts, main steam tubes, etc. of high-pressure and ultra-high-pressure boilers.