Prefabricated Pipe Customized Fittings Alloy Steel/ Stainless Steel Pipe Prefabricated Fabrication For Power

Four major pipelines in power plant factory piping, four major pipelines

It is a professional manufacturer of four major pipelines in thermal power plants. The company is a supporting supply unit of alloy high-pressure alloy steel pipes and alloy pipe fittings. It also undertakes the supporting work, and undertakes the manufacture of imported high-pressure alloy elbows, alloy pipe fittings, and alloy pipe bending services. It is a complex integrating storage, operation and processing. Reserve 20,000 tons of pipe and steel pipe storage warehouse. Our company has independent import and export rights, and the market has expanded to Japan, Germany, Italy, Spain, the United States, Switzerland, Poland, Argentina, South Korea and other countries.

Detailed details of the four major pipelines in the power plant:

1. Material selection of main steam pipeline

The standardization meeting of the power station pipeline and fittings of the relevant departments of the Ministry of Electric Power proposed the specifications of the main steam and water pipelines of the power station. Among them, the supervisor of the main steam system of the 300MW unit recommended the use of A335P22 alloy pipes. Since then, most of the domestic 300Mw unit projects have been selected accordingly, and the relevant manufacturers have also developed matching pipe fittings according to the A335P22 alloy pipe specification. The 300MW units that have been put into operation, such as Jinggangshan Huaneng Power Plant and Fengcheng Power Plant's main steam pipeline and reheat steam hot section pipeline, all use A335P22 alloy tubes. A335P91 alloy pipe is an improved 9Cr1Mo high-strength martensitic heat-resistant steel. Because P91 alloy steel pipe has the characteristics of high temperature strength, high oxidation resistance and high temperature steam corrosion resistance, it has been widely used in power station equipment in Britain, the United States, Germany and other countries in the 1980s. Since the 1990s, my country has gradually used A335P91 as the material for the main steam pipeline and the reheat steam hot section pipeline of the power station.

The strength of P91 steel is higher than that of P22, and its strength decreases less with the increase of temperature. At 20℃, the tensile strength of P91 alloy tee is 41.6% higher than that of P22 alloy tee; at 538℃, the allowable stress of P91 steel But it is 83.3% higher than P22 steel. It is precisely because P91 steel has much higher allowable stress than P22 steel at high temperature. This makes the wall thickness much thinner than that of P22 steel when used as the main steam pipe. This is the main reason why P91 steel is more and more widely used in large units. A preliminary comparison between P91 alloy pipe fittings and P22 alloy pipe fittings used in the main steam pipe. When the main steam pipe is made of P22 material, the main pipe specification is Φ368×82, and the branch pipe specification is Φ273×62.23; when using P91 material, the main pipe specification is Φ368.3×40, and the branch pipe specification is Φ273×30. The comparison shows that the wall thickness of the main pipe is reduced by 42mm, and the reduction rate is 51.2%; the wall thickness of the branch pipe is reduced by 32.23mm, and the reduction rate is 51.8%. The total weight of the alloy pipes is greatly reduced, and the total weight ratio of the pipes is P91/P22=1/2.18.

At present, with the fluctuation of market price, the unit weight price ratio of alloy pipe P91/P22 is about 1.4 to 1.95. Since the total weight reduction of the pipe exceeds the influence of the price increase, it is economical to use P91 for the main steam pipe. In addition, due to the thin wall thickness of the pipeline, the thrust and moment of the pipeline to the equipment interface can be reduced. At the same time, due to the reduction of the weight of the pipeline, the load of the support and hanger is correspondingly reduced. Not only the cost of support and hanger is saved, but also the corresponding pipeline installation cost and civil construction cost will be saved.

2. Pipe material selection for reheat steam hot section pipeline

The pipes in the reheating hot section are large diameter thin-walled pipes. If P91 alloy steel pipes are used, the already thinner wall thickness will be thinner. Because the calculated pipe wall is too thin, from the safety point of view, the actual value of the wall thickness is much larger than the calculated value. In this way, compared with P22, the use of P91 alloy pipe is less economical. When P22 alloy pipe is used in the reheating hot section, the main pipe specification is Φ635×31, and the branch pipe specification is Φ508×24.8; when P91 material is used, the main pipe specification is Φ727.96×21.03, and the branch pipe specification is Φ632.97×17.98. , the wall thickness of the main pipeline has been reduced by 10mm, the wall thickness of the branch pipeline has been reduced by 6.8mm, the total weight of the pipeline has not changed much, and the total pipeline weight ratio P91/P22=1/1.39 is much greater than the price ratio, so it is still recommended to use P22 pipe .

3. Pipe material selection for reheat steam cold section

According to the standardization meeting of the power station pipe fittings of the relevant departments of the former Ministry of Electric Power, according to the experience in the use of 300MW units, A672B70CL32 electrofusion welded steel pipe should be used instead of A106B seamless steel pipe in the cold section of reheated steam, which can also meet the technical requirements. The cold section main pipe adopts A672B70CL32 seam steel instead of A106B seamless steel pipe. The seam welded steel pipe is much cheaper than the A106B seamless steel pipe, which is about 1/3 of the seamless steel pipe. The wall thickness deviation of seam welded steel pipe is smaller than that of seamless steel pipe, and its quality is no less than that of seamless steel pipe.

4. Selection of high-pressure water supply pipes

The high-pressure water supply pipeline usually uses St4518/Ⅲ pipe, which is optimized to 15NiCuMoNb5 in this project. The main pipe specification is changed from Φ406.4×50 to Φ355.6×25, and the branch pipe specification is changed from Φ298.6×36 to Φ244.5×20.15NiCuMoNb5 The elastic modulus and linear expansion coefficient of St4518/III are very similar, but the allowable stress of 15NiCuMoNb5 is much larger than that of St4518/III. Therefore, when 15NiCuMoNb5 is used in the high-pressure water supply pipeline, the wall thickness of the pipeline can be reduced by 50%. The material consumption of the hanger can be greatly saved, the economy is more reasonable, and the project cost can be effectively reduced. Therefore, 15NiCuMoNb5 alloy elbow, WB36 alloy elbow, WB36 alloy tee, WB36 alloy reducer, and 15NiCuMoNb5 alloy tee are used for high-pressure water supply pipes.

Our company provides all kinds of pipes, pipes, pipe fittings and factory processing preparations required for power plant infrastructure (including reconstruction and expansion) projects, namely main steam pipes, alloy pipe fittings, reheat steam pipes, alloy pipe fittings (hot section, cold section), main High temperature and high pressure seamless steel pipes for water supply pipelines, pipe fittings, bypass systems, etc. The company has formulated a strict quality management system, and the supply of various pipeline materials strictly implements the relevant international and domestic standards based on the American asme, astm series, German din series, European en series and international gb series, and all product documents. Complete information. Main furnace tube materials: ST45.8/iii, 20G, A106b, 15CrMoG, 12Cr1MoVG, 10CrMo910, 12Cr2MoWWTib, T91, T92, Tp304H, Tp347H, super304h, T23, T24, etc. The main materials of the four major pipelines for infrastructure: A335P92, A335P91, A335P22, A335P11, A672B70CL32, A691Gr2-1/4CrCL22, A106b, 15NiCuMoNb5 (WB36), etc.