Weldneck Flange
characterized by it's smooth hub transition from flange to weldend. These are the most common type of flange used for high pressure applications. They are recognized by their long tapered hub. The hub provides an important reinforcement to the flange itself and acts to reduce rotation of the flange at bolt-up. The smooth transition between the flange and the hub combined with the strength of the butt weld joint, allows the flange to be used in extreme conditions of cyclic loading, bending and temperature fluctuations.

Slip-On Flange
fits over the pipe and is then welded in position. Only available in smaller pressure ratings/diameters. Slip-On Flanges are ideal for lower pressure applications. Their ease of fitting and welding reduces fabrication costs. Less time needs to be spent ensuring the accuracy of the cut pipe and they are somewhat easier to align. They do not have as much strength as a weldneck flange and are not available in higher pressure ratings and diameters.

Socket Weld Flange
pipe fits in to the recess to allow smooth flow through the flange. Used for small diameter applications. The fabrication of these items is similar to that of a Slip-On Flange. However, their internal pocket allows for a smooth bore and better fluid flow.

Lap Joint Flanges
must be used with their associated stub end. The stub is welded to the pipe and the Lap Joint then works as a backing ring. The main advantage of this type of flange is that the bolt holes can be aligned with the matching flange after the welds have been completed. A Lap Joint Flange is not suitable for areas with high external or dynamic loads. Useful for complex spools and rigid pipe work.

Threaded Flanges
can be fitted to the pipe without welding, though a seal weld can sometimes be used. They are suitable for small diameter high pressure services. At larger diameters, the difficulty in machining the thread on to both the flange and pipe makes them unviable. They are also not suitable for areas having high external loads, particularly torsion.

Blind Flanges
are used to blank off the ends of piping, valves and pressure vessel opening. From the standpoint of internal pressure and bolt loading, blind flanges, particularly in the larger sizes, are the most highly stressed of all flange types; however, since the maximum stresses in a blind flange are bending stresses at the center, they can safely be permitted to be higher than in other types of flanges.

Orifice Flanges
are widely used in conjunction with orifice meters for measuring the rate of flow of liquids and gases. They are basically the same as standard welding neck and slip-on flanges except for the provision of radial, tapped holes in the flange ring for meter connections and additional bolts to act as jack screws to facilitate separating the flanges for inspection or replacement of the orifice plate. In choosing the type of orifice flange, the considerations affecting the choice of welding neck and slip-on standard flanges apply with equal force.