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What Is a Flange Adapter?

Paul Scott
Paul Scott

Flange adapters are an extensive family of flange joint accessories that allow the execution of joints between dissimilar flange types or flanged and non-flanged equipment. The significant flexibility gained by using these devices becomes apparent when the enormous range of common flange types in general use is considered. In fact, most manufacturers of flanges or flanged equipment produce their own lines of flange adapter accessories, allowing their products to be integrated into other systems with ease. Although these adapters are themselves represented by a vast array of different types, they fall into two main categories. The first are flange-to-flange types, with the second being those used to join flanged and non-flanged equipment.

Flanges are little more than flat discs or shoulders integral to or loose fitting on the relevant part or pipe. The flange disc is fitted with a number of holes around its periphery through which locking bolts are passed. To join two similarly flanged pieces of equipment, the two halves are brought together, locking bolts are passed through the holes in both flange discs and tensioned. This pulls the two flanges hard up against one another, effectively joining the two pieces of equipment.


The flange adapter is used where the two pieces of equipment do not have similar flange types or only one-half is flanged. These adapters fall into two broad categories, namely those used on dissimilar flange pairs and those used in situations where a non-flanged part is joined to a flanged part. Flange-to-flange adapters are usually represented by those adapters designed for dissimilarly-sized flanges and those used to join flanges of the same size with differing hole arrangements.

Joints featuring flanges of different sizes may easily be made using a flange adapter featuring one of each of the two flange sizes joined by a short reducer section. These adapters are simply arranged so the relevant flange sizes are matched between the parts and the adapter, and tensioned in the normal fashion. Adapters used to join flanges with differing hole patterns are even simpler and typically consist of a single disc drill halfway through on either side with the two different hole patterns. The holes in the adapter are tapped with a standard screw thread so that, when slipped between the two dissimilar flanges, bolts can be used to tension each of them up against the adapter. In general, this type of adapter will be supplied with a set of the correct bolts.

Flanged to non-flanged joints require a special type of flange adapter that generally has a flange on one end and a secondary locking mechanism suitable for the relevant equipment on the other. For instance, a flange adapter designed to join an non-flanged hose to a flange-equipped pipe will have a suitably-sized flange on one end and a compression or half-shell hose clamp on the other. The flanged end is bolted to the secondary device's flange in the normal way and the non-flanged hose securely attached with the hose clamp.

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