WHAT IS A SWIVEL FLANGE?
A swivel flange has a ring around the hub that can be rotated, during the installation, independently from the flange hub and the connected pipe. Swivel flanges facilitate the alignment of bolt holes to the counter flange, a feature that may be helpful in many circumstances. They are manufactured by forging steel and machining the part to the required specification.
The major standards for swivel flanges are ASME/ANSI, DIN, BS, EN, ISO, etc. The most common standard for petrochemical application is the ANSI/ASME B16.5. They are suited for oil, gas, hydrocarbon, water, chemical and other demanding services.
The swivel flange is made of two main parts:
- The hub, which is welded to the pipe
- The swivel ring, which is fitted on the hub, has the bolting holes and can rotate freely around the hub
USE OF SWIVEL FLANGES
Swivel flanges are used to easily align the bolt holes of the flanges at both ends of the pipe and then bolt the flanges properly. This is particularly helpful in case of large diameter pipes, that would be very challenging to bolt properly with standard flanges and their required alignment activities. In such case, for instance, the pipe could be fitted at one end with a standard flange and with a swivel flange at the opposite end (that would be rotated easily to achieve the needed alignment prior the bolting). Another typical application of swivel flanges is offshore (subsea and shallow waters), as they facilitate the pipe assembly in challenging environments and underwater.
TYPES OF SWIVEL FLANGES
Swivel flanges are available in all the standard shapes of common flanges, i.e. weld-neck, slip-on, lap-joint, socket weld etc, in all material grades and in a wide dimensional range (sizes can vary from 3/8” to 60” and pressure rating from 150 to 2500).
MATERIALS FOR SWIVEL FLANGES
Swivel flanges can be manufactured in carbon steel (ASTM A105), alloy steel (ASTM A182 F1, A182 F5, A182 F9, A182 F91), and, stainless steel (ASTM A182 F304, A182 F304L, A182 F316, A182 F316L). For more information about the materials for forged flanges, refer to this article.