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1. Slip-on pipe flanges
Slip-on pipe flanges actually slip over the pipe. These pipe flanges are typically machined with an inside diameter of the pipe flange slightly larger than the outside diameter of the pipe. This allows the flange to slide over the pipe but to still have a somewhat snug fit. Slip-on pipe flanges are secured to the pipe with a fillet weld at the top and the bottom of the slip-on pipe flanges. These pipe flanges are also further categorized as a ring or a hub
2. Weld neck pipe flanges
Weld neck pipe flanges attach to the pipe by welding the pipe to the neck of the pipe flange. This allows for the transfer of stress from the weld neck pipe flanges to the pipe itself. This also reduces high stress concentration at the base of the hub of the weld neck pipe flanges. Weld neck pipe flanges are often used for high-pressure applications. The inside diameter of a weld neck pipe flange is machined to match the inside diameter of the pipe.
3. Blind pipe flanges
Blind pipe flanges are pipe flanges used to seal the end of a piping system or pressure vessel openings to prevent flow. Blind pipe flanges are commonly used for pressure testing the flow of liquid or gas through a pipe or vessel. Blind pipe flanges also allow easy access to the pipe in the event that work must be done inside the line. Blind pipe flanges are often used for high-pressure applications. Slip-on pipe flanges with a hub have published specifications that range from 1/2" through 96".
4. Threaded pipe flanges
Threaded pipe flanges are similar to slip-on pipe flanges except the bore of the threaded pipe flange has tapered threads. Threaded pipe flanges are used with pipes that have external threads. The benefit of these pipe flanges is that they can be attached without welding. Threaded pipe flanges are often used for small diameter, high pressure requirements. Slip-on pipe flanges with a hub have published specifications that range from 1/2" through 24".
5. Socket-weld pipe flanges
Socket-weld pipe flanges are typically used on smaller sizes of high-pressure pipes. These pipe flanges are attached by inserting the pipe into the socket end and applying a fillet weld around the top. This allows for a smooth bore and better flow of the fluid or gas inside the pipe. Slip-on pipe flanges with a hub have published specifications that range from 1/2" through 24".


Standard of Steel Flange

Endress+Hauser usually delivers only flanges with a flat face. This type of flange has hardly changed. Thus, a comparison is done only for these sealing surfaces. Due to the change of the designation of the sealing surface, mistakes may occur occasionally. The roughness (Rz) of the old raised face form C and the new one B1 overlap between 40 and 50 μm. In this roughness window, both standards are fulfilled.
Therefore, at Endress+Hauser, the flanges are specified according to both flange standards. This double marking makes it clear that both standards are met.



Painting & Coating of Steel Flange
Light Oiling, Black Painting

Welding Neck (WN) Flanges: Feature a long tapered hub that is butt-welded to the pipe. They distribute stress evenly and are ideal for high-pressure, high-temperature, and critical applications.
Slip-On (SO) Flanges: The pipe simply slips into the flange and is fillet-welded. They are easier to align and more cost-effective, making them suitable for low-to-medium pressure applications.
Raised Face (RF): The most common type, featuring a raised ring where the gasket sits. Ideal for general industrial applications.
Flat Face (FF): The entire face is flat. Typically used with cast iron or plastic flanges, or in low-pressure water lines.
Ring Type Joint (RTJ): Features a groove for a metal ring gasket. Designed for extremely high-pressure and high-temperature environments, such as oil and gas pipelines.
Sizes: From 1/2" to 80" (DN15 to DN2000).
Pressure Classes: ANSI Class 150 to 2500, and DIN PN6 to PN400.
Materials: Carbon Steel (ASTM A105, A350 LF2), Stainless Steel (ASTM A182 F304/316/321), and Alloy Steel.
A: Quality is non-negotiable. Every flange undergoes rigorous testing, including chemical composition analysis, mechanical property tests, and 100% Non-Destructive Testing (NDT) such as Ultrasonic Testing (UT) to detect internal flaws. Every shipment includes a comprehensive Mill Test Certificate (MTC), and we fully welcome third-party inspections (SGS, BV, TUV).