A guide to flange design and industrial applications

A flange is usually a piece of metal that is used to strengthen structural elements in buildings or equipment. It increases the element’s strength to resist bending. A flange is also used to join parts of a more complicated system. These could be piping, tanks, valves and prosthetic limbs.

Flange design

A pipe flange is probably the most common type of flange that many people recognise. It can be welded or screwed onto a pipe to give the piping extra strength and to connect two pipe parts. A strong seal is provided by inserting a gasket between two mating flanges. There are six types of flange.

A slip on pipe flange really does slip over the pipe. The idea is that it has an internal diameter that is slightly larger than the external diameter of the pipe over which it will fit. These flanges are sometimes called rings or hubs.

A weld neck pipe flange is attached to the neck of a pipe by welding. Stress from the flanges transfers to the pipe and reduces the stress at the neck. The inside diameters of the flange and pipe match.

A blind flange seals the end of a piping system or pressure vessel and prevents any flow. This type of flange must allow easy access to the pipe for any repair or maintenance work.

A lap joint pipe flange is welded to the stub end of a pipe and is free to rotate around it. These flanges are used in systems that need frequent dismantling.

A threaded pipe flange is similar to the slip on version but instead has tapered threads. These are used with pipes that have external threads and can be attached without welding.

A socket-weld pipe flange is used on small sized high pressure pipes. These are attached by inserting the pipe into the socket end of the flange and joining the two pieces together with a fillet weld.

Offshore drilling

Sometimes a flange can be attached to a fitting made of a different metal. Titanium metal is used frequently in the offshore oil and gas industry for drilling risers. These are the pipes that are used to carry drilling mud down to a drilling target and bring the used mud and rock debris back to the surface. Titanium is a metal with a very high resistance to seawater corrosion and the high temperatures that occur when drilling at great depths. The welding of titanium flanges onto riser pipes is a very expensive process. So titanium is used mainly for tapered joints to control the curvature of the pipe while a steel-titanium alloy with a shrink fitting connection is used for the flanges.

Flanges are used for strengthening and joining equipment parts used over a wide range of industries. They are used as common fittings in domestic plumbing and in joining components of oil drilling equipment. Titanium flanges are used extensively in prosthetic limb manufacture because of the high biocompatibility of titanium metal.


Tom Brown is a mechanical engineer with 15 years of professional experience. He works on flange design and writes for a wide range of website and blogs covering the industrial machinery sector. Visit the Chempro website to see an extensive range of flanges.


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