What’s a Flange Joint?

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Flange joints are a removable way of joining steel and plastic pipes, consisting of two discs with fixing holes. They are quick to fit and remove, suitable for various pipe designs and sizes, and can connect pipes to equipment. Flanges have different designs, including slip-on, raised face, and lap joint flanges, and can have gaskets for hermetic seals. There are various types of flanged joints, including threaded, slip, lap, blind, and insulated flanges, all manufactured to standard sizes for compatibility.

A flange joint is a non-permanent, removable method of joining or shearing steel and plastic pipes. Flange joints consist of a pair of identical discs with a row of fixing holes close to the outer circumference. When two pipes are to be joined, the two discs are placed against each other so that the holes are aligned. The bolts are then passed through the holes and tensioned, thus pulling the flanges tightly against each other. Flanges are available in a range of designs including slip-on flanges, raised face flanges and lap joint flanges, all to suit different piping system requirements.

The flange joint is one of the most convenient and efficient removable pipe joining and shearing systems in common use. Flanged joints are suitable for a wide range of pipe designs, materials and sizes and are common on systems as diverse as large municipal water mains and small high pressure steam lines. Flange joints are quick to fit and remove and can be included on stock lengths of pipe or installed in situ to existing pipe loops. The flange joint allows for the quick and effective connection of pipe sections and for joining pipe sections to ancillary equipment such as pumps, valves and metering devices. The wide range of types also means that there is a flange joint to suit most transport vehicles.

A typical flange joint consists of two identical discs or plates that have similarly positioned sets of mounting holes arranged around the periphery. Some flanges are permanently welded or epoxy welded onto the pipe or even cast as part of the pipe or fixture. Other flange designs feature a slip-on disc that lifts against a collar or shoulder permanently attached to the pipe. When the joint is made, the two plates or discs are placed against each other and bolts are driven through the holes. When the bolts are tensioned, the two plates pull hard against each other, thus forming a secure joint.

Depending on the application and the particular flange design, a gasket or gasket may be placed between the discs prior to tensioning. The tension force then compresses the gasket to form a good hermetic seal. Flanges often have corresponding grooves and protrusions in their faces or series of concentric serrations that help locate the gasket. These gaskets are typically used on piping systems that carry high pressure fluids or gases.

There are a variety of flanged joint designs available on the market that cater to an equally diverse selection of pipe types and applications. These include threaded flanges that screw onto the pipe and slip or lap joint flanges with free-spinning discs. These loose flange couplings are the easiest to install on existing pipe systems because the discs can be rotated to line up the holes when pipes can’t. Other types of flanged joints include blind flanges used to close off unused pipe ends and insulated flanges which prevent cathodic corrosion by electrically isolating pipe sections. Flanges are all manufactured to standard size sets ensuring cross application compatibility and ease of use.




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