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What are the differences in material selection for different types of flanges (e.g. plate flanges, butt-welding flanges, etc.)?
The differences in material selection for different types of flanges mainly depend on their structural characteristics, usage scenarios and performance requirements. The following are the characteristics of some common types of flanges in terms of material selection:
Plate flange
Structural characteristics: plate flange has a simple structure, usually consists of a disk with bolt holes and a sealing surface, which is directly welded or threaded to the end of the pipeline.
Usage Scenario: Generally used in low-pressure, room-temperature piping systems, such as water supply and drainage, HVAC and other systems.
Material selection:
Carbon steel: lower cost, with a certain degree of strength and corrosion resistance, to meet the general requirements of low-pressure, room temperature conditions, such as Q235B and other materials are more commonly used.
Stainless steel: when the pipeline conveying medium has certain corrosion resistance requirements, you can choose stainless steel materials, such as 304 stainless steel, can resist general acid and alkali corrosion and oxidation, suitable for food, beverage, mildly corrosive chemical media and other pipelines.
Butt-welding flange
Structural characteristics: Butt-welding flanges have longer necks and are connected with the pipelines by butt-welding, with high quality welds, which can withstand higher pressure and temperature.
Usage Scenario: Widely used in piping systems with high temperature, high pressure, flammable and explosive as well as toxic and hazardous media, such as petrochemical, electric power, natural gas and other industries.
Material selection:
Carbon steel: for pressure and temperature is not particularly high occasions, can choose carbon steel material, such as No. 20 steel, with good welding performance and a certain degree of strength, can withstand a certain pressure and temperature.
Alloy steel: in the high temperature and high pressure environment, often used chromium and molybdenum alloy steel, such as 15CrMo, 12Cr1MoV and so on. These materials have good high-temperature strength, oxidation resistance and creep resistance, and can work stably for a long time under high temperature and high pressure.
Stainless steel: when the medium is corrosive or high cleanliness requirements, stainless steel is the preferred material, such as 316L stainless steel, with excellent corrosion resistance and resistance to intergranular corrosion performance, suitable for chemical, pharmaceutical and other industries corrosive media pipeline.
Socket Welding Flange
Structural characteristics: one end of socket welding flange has a socket, the pipe is inserted into the socket and then welded, less welding workload and better sealing.
Usage Scenario: It is suitable for small-diameter pipelines, commonly used in pipeline systems of chemical industry, oil refining and other industries, especially for occasions with high sealing requirements.
Material selection:
Carbon steel: similar to plate flanges, carbon steel material, such as Q235B, can be used to reduce the cost in small-diameter pipelines with low-pressure and non-corrosive media.
Stainless steel: for small-diameter pipelines with corrosion resistance requirements, such as pipelines conveying corrosive media like acid and alkali, 304 or 316L stainless steel is often used to ensure the corrosion resistance and sealing of the flanges.
Loose set flange
Structural characteristics: loose sleeve flange consists of a loose sleeve ring and a flange, the loose sleeve ring is set on the pipe, the flange is connected with the loose sleeve ring through bolts, and there can be a certain relative displacement between the pipe and the loose sleeve ring.
Usage Scenario: It is mainly used in pipeline systems with certain axial displacement, vibration or frequent disassembly, such as the import and export pipelines of pumps, compressors and other equipments.
Material selection:
Carbon steel or stainless steel: the loose ring is generally made of the same material as the pipeline, such as carbon steel or stainless steel. The flange can be made of carbon steel or stainless steel according to the actual demand, when the requirement of corrosion resistance is high, stainless steel flange is used; for general working conditions, carbon steel flange can meet the requirements.
Non-ferrous metal: In some special occasions, such as conveying media with special requirements or needing better corrosion resistance, non-ferrous metal materials will also be used to make loose flanges, such as copper alloy, nickel alloy and so on, in order to meet the special requirements for use.
Threaded flange
Structural characteristics: threaded flanges are connected to the pipeline through threads, which is convenient for installation and disassembly and does not require welding.
Usage Scenario: It is suitable for some occasions which are not suitable for welding, such as pipeline systems with restricted installation conditions on site or requiring frequent disassembly, and some pipelines with low-pressure and non-corrosive media.
Material selection:
Carbon steel: in the low-pressure, non-corrosive media pipeline, such as general compressed air pipeline, often use carbon steel threaded flanges, such as Q235B material, lower cost, easy to install.
Stainless steel: when the medium conveyed by the pipeline has certain corrosion resistance requirements, stainless steel threaded flanges, such as 304 stainless steel, can meet the general corrosive medium conveying requirements.