What is a stainless steel flange?
　　A stainless steel flange is a disc-shaped or ring-shaped part made of stainless steel material, typically used to connect pipes, valves, pumps, and other equipment to form a sealed connection. It connects two flanges together with bolts and uses gaskets between the flanges to ensure sealing. Stainless steel flanges are widely used in petroleum and natural gas, chemical processing, water treatment, power plants, and the food industry due to their durability, high strength, corrosion resistance, and chemical resistance.
　　Main features of stainless steel flanges:
　　Strong corrosion resistance: Stainless steel has excellent corrosion resistance, able to withstand corrosion from steam, acids, alkalis, salts, and various other media, making it very suitable for use in harsh environments.
　　High strength: Stainless steel has good strength and rigidity, capable of withstanding high pressure and temperature.
　　Good hygiene: Stainless steel surfaces are smooth, resistant to scaling, easy to clean, and meet hygiene requirements, commonly used in food and pharmaceutical industries.
　　Long service life: Due to its corrosion resistance and high strength, stainless steel flanges generally have a long service life.
　　Detachable connection: Flange connections are detachable, facilitating equipment installation, maintenance, and replacement.
　　Classification of stainless steel flanges
　　Stainless steel Flange
　　1. Butt Weld Flange
　　A stainless steel butt weld flange refers to a flange with a neck, where the outer side of the neck has a bevel, used for butt welding with pipes or equipment. Its structural feature is that the flange body is welded to a tapered cylindrical pipe section (the neck), with the neck height varying according to different pressure ratings and standards. Butt weld flanges are important pipeline connectors, commonly used in medium to high pressure and temperature fluctuating pipeline systems.
　　Structural features:
　　Necked structure: Features an upward extending tapered neck that gradually thins.
　　Butt weld seam: The neck is butt welded in a ring shape to the pipe or equipment.
　　Bevel design: The end of the neck is usually beveled to facilitate good fusion during welding and ensure weld quality.
　　2. Blind Flange
　　Blind flange, also called blind plate, is a type of flange connection that has no hole in the center. One of its functions is to seal the end of a pipeline, and another is to facilitate the removal of debris during maintenance. In terms of sealing, it serves the same purpose as end caps and pipe caps, but unlike end caps which cannot be removed, blind flanges are bolted and can be easily disassembled. They are usually bolted to the flange of a pipe or equipment, with a gasket between them to achieve sealing.
　　Structural features:
　　No center hole: This is the most distinctive feature of a blind flange.
　　Disc or circular shape: Usually circular and disc-shaped, but can be made in other shapes according to special requirements.
　　Bolt holes: Several bolt holes evenly distributed around the perimeter for connection and fixation with other flanges.
　　3. Socket Weld Flange
　　A stainless steel socket weld flange is a type of flange where the pipe end is inserted into the socket hole of the flange and then welded with a circular fillet weld. Its feature is that the flange inner diameter has a socket hole slightly larger than the pipe outer diameter, with a step to position the pipe insertion depth. Socket weld flanges are commonly used in small to medium diameter, low-pressure pipeline systems.
　　Structural features:
　　Socket hole design: The flange inner diameter is machined into a stepped socket hole where the pipe is inserted and positioned by the step.
　　Fillet weld connection: Connection is achieved by welding a circular fillet weld between the outside of the flange and the pipe.
　　No bevel: Unlike butt weld flanges, the pipe end of socket weld flanges usually does not require beveling.
　　4. Threaded Flange
　　A threaded flange has its inner hole machined with pipe threads and connects with threaded pipes, making it a non-welded flange. Its feature is that the flange inner hole is threaded according to standards, allowing connection by simply screwing without welding. Threaded flanges are usually used in low-pressure, small-diameter pipeline systems where welding is not required, especially suitable for situations where welding is not allowed or difficult to perform on site.
　　Structural features:
　　Internal thread design: The flange inner hole is machined with threads meeting relevant standards.
　　Non-welded connection: Connected by screwing onto external threads on pipes or equipment without welding.
　　Multiple sealing face options: Sealing faces such as flat face (FF) and raised face (RF) can be selected according to requirements.
　　5. Slip-On Flange
　　A stainless steel slip-on flange is a type of flange that is slipped over the pipe end and then welded with circular fillet welds on both the inside and outside of the flange. Its feature is that the flange inner diameter is slightly larger than the pipe outer diameter; during installation, the flange is slipped onto the pipe, and double-sided fillet welds are required. Slip-on flanges are commonly used in low to medium pressure pipeline systems where high connection strength is not required.
　　Structural features:
　　Sleeve-type connection: The flange inner diameter is slightly larger than the pipe outer diameter and is slipped directly onto the pipe during installation.
　　Double fillet welds: Fixed by welding two circular fillet welds on the inside and outside of the flange to the pipe.
　　No neck design: Usually does not have a tapered neck like butt weld flanges.
　　6. Loose Flange
　　A stainless steel loose flange is not directly welded to the pipe but connected through a stub end with a flange. The loose flange itself is a ring with bolt holes, and its inner diameter is slightly larger than the outer diameter of the stub end, allowing it to slide freely over the stub end.
　　Structural features:
　　Loose Ring: The flange itself is a loose ring, with an inner diameter slightly larger than the outer diameter of the connector (usually a flanged short piece).
　　Flanged Short Piece: A short pipe section that has been flanged, with one end welded to the pipeline and the other end forming a sealing surface and a pressed flange.
　　Non-Welded Connection (Flange Itself): The flange itself is not directly welded to the pipeline.
　　Sealing Achieved by Flanging: The seal is achieved by bolts pressing the flange of the flanged short piece.
　　Applications of Stainless Steel Flanges
　　1. Petrochemical Industry:
　　- Crude oil and natural gas transportation
　　- Refineries
　　- Chemical plants
　　2. Pharmaceutical Industry:
　　- Active pharmaceutical ingredient production
　　- Formulation production
　　3. Power Industry:
　　- Thermal power generation
　　- Nuclear power
　　4. Shipbuilding Industry:
　　- Ship pipeline systems
　　5. Water Treatment Industry:
　　- Water supply and wastewater treatment
　　6. Machinery Manufacturing Industry:
　　- Hydraulic and pneumatic systems
　　- General machinery equipment
　　7. Other Industries:
　　- Construction industry
　　- Environmental protection engineering
　　- Scientific research field

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