Different Types of Flanges Used in Piping Applications

• Blind Flanges

A blind flange is a flange that does not have a bore and is used to blank off the end of pipes, valves, and pressure vessels. In terms of internal pressure and bolt loading, blind flanges are the most overstressed flange type, especially in larger sizes. Nevertheless, most of these pressures are bending types near the center, and since there is no standardized inner diameter, these flanges are ideal for higher-pressure temperature systems, as there is no standard inner diameter. Flanges like these are used to block out a segment of pipe or a nozzle that is not in use on a vessel when it is not in use. As a result of pressure checks in a plant or simply because the consumer doesn’t need all the nozzles provided on the tank, the nozzle is often blanked off with a blind flange.

• Spectacle Blind Flanges

There are many instances where the use of Spectacle Blinds is deemed necessary by the project owner. This type of blind can be used for permanent bridging, or it can be used for simply connecting pipes to one another.

As it happens, the two discs are connected by a part made of steel, much like the part that goes on the nose of a pair of glasses. As its name suggests, the assembly is a lot like eyeglasses. One disc is a solid plate and one is a ring with an inner diameter similar to that of a flange. They both look like spectacles or glasses. In order to maintain the separation of structures from other installations on a regular basis, spectacle blinds are often used. As the Spectacle Blind is usually installed in the position of “open” to permit the flow of water through the pipe, it is to be turned in the “closing” position to prevent the flow of water. If it is rotated into the “closed” position, the flow of the water is blocked off.

• Lap Joint Flanges

Stainless steel pipe systems can be equipped with stub ends, but lap joints are often used with flanges as well because they can be used with a carbon steel pipe. For example, the carbon steel flange won’t come into contact with the substance in the pipe. Despite the fact that the stub ends are butt-welded to the pipes, these flanges have beveled edges in order to clear the stub end radius during construction. The inner radius of these flanges has been designed to have a beveled edge in order to facilitate the process of metal pipe connectors. A lap joint flange is almost similar to a slip-on flange, except that it has a radius that accompanies the flanged portion of the stub end at the intersection of the flange face and bore. As a result of their low pressure holding ability and fatigue life, which is only one-tenth as long as the flanges used on the Weld Neck flanges, they do not hold pressure as well as Slip On flanges. Thus, a lap joint flange is typically used in applications that do not require criticality or high pressure.

• Reducing Flanges

When the size of the pipe with flange changes, reducing plumbing flangesare designed to adjust the size of the pipe. They are typically designed to match the larger pipe size (NPT) with a smaller bore to match the smaller pipe size (NPT). These flanges generally come in neck flanges that are blind, slip-on, threaded, and welded. They are available in all pressure classes and offer an excellent option for connecting two pipe sizes of different sizes. 

An unexpected change, such as a change in pressure at a pump, would cause unnecessary turbulence if this type of flange is used.

Designed for use in piping systems of changing diameters. It consists of a federal flange of a certain diameter combined with a separate bore with a smaller diameter that is separate from the flange. There are dimensions for the flange of the larger pipe size except for the bore and hub dimensions. Reducing flanges are usually attached by welding, gluing, or clamping flanges of the same size together with various connecting pieces.

• Threaded Flanges

While threaded flange metal look very similar to Slip-On flanges, the key difference between them and Slip-On flanges is that the threaded flange has been bored to match the inside diameter of a particular pipe in order to provide a more secure fit. It is a type of flange that conforms to ASME B1.20.1 and has taper pipe threads in its bore. It can be used in piping systems where the possibility of welding the flange onto the pipe is not possible, such as in highly explosive zones where welding could cause serious damage. The threaded flange is fixed onto a pipe that has additional threads to the taper pipe. Galvanized and cast-iron pipes are commonly used with threaded flanges. Generally, threaded flanges are used in very high-pressure systems and in very small diameters and their biggest advantage is that they are able to be installed without welding.

• Square Flanges

This type of flange is usually used for connecting pipes to each other and between components, and it is manufactured in compliance with the JIS B2291/JIS F7806 standards. They are also used for connecting pipe flange dimensions to pipes as well as pipe to components. It is common for them to be used in hydraulic systems where there is fluid flow and they are manufactured from steel and stainless steel, respectively. The full set of square flanges comes with the ring, bolts, a female coastal Tube flange (oring side), as well as a male flange (flat side). The female flange is listed as part of a complete set of square flanges. The male flange 1 2 is referred to as Part B. The full set is referred to as Part AB.

It is recognized and recommended by the API standards that there are three types of Square Flanges, are they SHAB – used with hexagon hex bolts, the larger size of the 2 in pipe flange body, SSAB – used with socket cap screws, the smaller size of the flange body than SHAB, and LSA – oring only, L shaped internal flow.

• Long Neck Weld Flanges

Oil and gas companies, especially those involved in high pressure and high (or fluctuating) temperature situations, often use long welded neck texas flanges (often abbreviated to LWN) for their application. With a standard welded neck Steel pipe flange, you are able to insert your pipe directly into the flange and the long neck provides the pipe with reinforcement that is not possible with a standard welded neck flange. It is of utmost importance for industrial, commercial, and even residential high-pressure systems to be safe. A Long Weld Neck Flange, unlike many other flange types, is a flange that has no schedule bores. Some Long Weld Neck Flanges are also square cut, and they are usually made with square cuts for replacing the pipe and not to be welded to the pipe.

In a factory or apartment complex, the long weld-neck flange anchors water mains or gas sources being pumped into a larger network of pipes.

• Expander Flange

In the world of expandable flanges, which are often referred to as EXPF, the hub extends to a larger size (one or two sizes) than a standard welded neck flange. In the event that you do not have enough space or simply want to connect to a larger pipe diameter, then this is a great place for equipment, pumps, and vents. In comparison to a flange with a reducer-welding neck, this compact size saves space, which in turn eliminates the need to use both flanges and reducers. The expander flange is also considered a cost-effective alternative to the reduced-welding neck flange as they meet the same pressure and dimension requirements of the ASME B16.5. The Expander Flange has a raised face which allows a single buttweld to be used in the process of installing it.

• Spade And Ring Spacer Flange

A Spacer Flange and Spike Flange, in essence, are the same thing as Spectacle Blinds except that they are not connected on both ends. It is common for spades and spacers to be used in systems where maintenance is not often required or in large pipe-size applications. A spade can weigh hundreds of pounds depending on the flange size and the level of stress. In order to avoid additional weight, two separate pieces have been chosen for the flange connection so that the Spectacle Blind does not increase in weight. When replacing the Ring Spacer temporarily with a spade in order to reduce the risk of a pipe system failure due to high maintenance, it can be a very good choice.