Flanges are used to connect together pipes or to connect a pipe to a choke, tee, valve or other equipment. There are many different flange standards to be found worldwide.
To allow easy functionality and inter-changeability, these are designed to have standardised dimensions.
Common world standards include ASA/ANSI/ASME (USA), PN/DIN (European), BS10 (British/Australian), and JIS/KS (Japanese/Korean).
The most used flange types in Petro and chemical industry are:
Lap Joint Flange
For pipes that are frequently taken apart for repair or replacement, lap joint flanges are used. These flanges are used with a universal stub-end insert that is easily rotated and makes it easy to line up bolt holes. This type of flange is used for junctures that do not come in contact with anything flowing through the pipes, which increases their durability and renders them reusable. Caution should be taken not to use lap joint flanges for jobs where high temperatures or high pressure conditions are possible.
Slip-on flanges are thinner than most flanges as they are slid over pipe ends, easily aligned with bolt holes, and then permanently welded into place. Unlike lap joint flanges, they are designed to withstand contact with liquids and can withstand low-pressure atmosphere. They are stronger than other flanges, low cost and dependable at preventing leaks.
Threaded Pipe Flange
This popular type of flange not only comes in a wide range of materials and sizes, it can also be attached to pipes without welding, as it is a threaded flange. Extremely useful in connecting small pipes, it is a low cost flange that can be safely used in highly explosive and high pressure areas of projects and machinery.
Weld Neck Flange
The most popular type of high pressure pipe flange is the weld neck flange. The tapered hub design provides an extremely strong connection and these flanges can be repeatedly manipulated and bent without compromising the quality of the material and/or connection. The weld neck flange is highly resistant to extreme high and low temperatures.
Socket Welding Flange
The socket welding flange was created specifically for small piping that must withstand high pressure and/or contact with chemicals. With expert grinding and welding, socket welding flanges allow the unfettered flow of any type of liquid.
Standards, Dimensions & Weight
- ASME/ANSI B16.5 Class 150 SW
- ASME/ANSI B16.5 Class 300 SW
- ASME/ANSI B16.5 Class 600 SW
- ASME/ANSI B16.5 Class 1500 SW
These flanges are commonly used to seal or blank off the ends of valves and pipes. They are always round and have bolt holes around their perimeter. They are economical.
- Cabon steel: A105, A350 LF2
- Stainless steel: A182 F304/F304L/F316/F316L/F321
- Alloy steel: F11, F12
Packing: plywood case and plywood pallet
Some piping system designs require constant changes in pipe diameters to accommodate changing conditions. The reducing flange economically connects different types and sizes of flanges, can endure extreme changes in pressure and are easy to attach.
Except for the bore and hub dimensions, the flange will have dimensions of the larger pipe size.
Reducing flanges are normally provided as one of three types:
- Welding Neck flange
- Slip-On flange
- Threaded flange
- Special Flanges
Except the most used standard flanges, there are still a number of special flanges such as:
- Orifice Flanges
- Long Welding Neck Flanges
- Weldoflange / Nipoflange
- Expander Flange
- Large size flange
- Figure-8 Blanks (Spectacle Blind Flange)