Pipe Flanges

General information on pipe flanges

Pipe flanges are pipe accessories for connecting two pipes or pipe sections. The ring-shaped discs are usually firmly connected to the pipes to be joined by welding or screwing them in. Pipe flanges have either a hole or an extension with an opening in the middle. Pipe flanges are available in many different designs, including slip-on flanges, welding neck flanges, threaded flanges, and lap joint flanges.
Welding neck flanges have an attachment that is welded to a pipe or spigot. This type of flange can also be used at high nominal pressures thanks to its special stability. Threaded flanges have an internal thread and are screwed to the pipe. Loose flanges, as the name suggests, are not firmly connected to the pipe but are pushed on loosely. A welding ring is welded to the pipe, against which the loose flange rests and transfers the bolt forces to the pipe.
Smooth flanges are also pushed onto the pipe, but are then welded to the pipe. Blind flanges are used to seal pipe ends or spigots tightly. They are designed as closed round discs.
Requirements for round steel flanges for pipes, valves, fittings and accessories are specified in EN 1092-1, for example flange types, sealing surface shapes, materials and tolerances for the various pressure ratings (PN) and nominal sizes.

Manufacture of pipe flanges

Pipe flanges are made of different materials and with different manufacturing processes. They are often made of stainless steel. However, they are also made of cast iron or copper or copper alloys.
Forged pipe flanges are usually manufactured by drop forging. In this process, a blank is heated to forming temperature and formed. This is followed by deburring and piercing of the forged part. Threaded flanges are provided with an internal thread. Heat treatment allows certain material properties, such as the strength of the forging, to be adapted to the requirements in question, and machining residues can be removed by descaling.
Turned pipe flanges are manufactured by turning on a lathe. In this process, the turned part rotates around its own axis while a turning tool traces the contour to be produced. Since flanges are usually rotationally symmetrical, this process is well suited for their manufacture. Cast pipe flanges are usually made of cast iron in foundries. Casting processes can also be used to create very complex shapes.

Applications of pipe flanges

Pipe flanges are used to connect pipe sections or as blind flanges to seal pipe ends or spigots. They are mainly used in the following areas:

• Pipeline construction
• Plant engineering
• Apparatus engineering
• Mechanical engineering
• Heating construction
• Chemical industry
• Petrochemical industry
• Food industry

Advantages of pipe flanges

Pipe flanges offer the advantage that they can be used to make very tight connections in piping systems that remain detachable.