7 Types of Flanges Used in Piping Systems

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A flange is a type of mechanical joint system that provides a reliable means to connect pipes, valves, pumps, and other components to form a seal-proof piping system. 

Flanges are typically threaded or welded, and two flanges are connected by bolting them with gaskets to form a seal that allows easy access to the pipe system. 

A flange is an essential part of pipeline infrastructure and the second-most used joining method after welding.

The various types of flanges utilized in pipe systems are described below according to their diameters and other variables:

1. Slip-on Flange

A slip-on flange is a flange that attaches to a pipe or fitting via two fillet welds, one within the flange cavity and the other outside the flange. 

Slip-on flanges are flanges that slip over a pipe, hence the name. The bore size of a slip-on flange is greater than the connecting pipe's outer diameter, so the pipe must move inside the flange to be connected by a fillet weld.

Slip-on flanges are a kind of flange that is often used in fluid pipelines.

2. Threaded Flanges

Threaded flanges resemble slip-on flanges, but the main difference is that the threaded flange has been bored out to fit the inner diameter of a particular pipe.

The threaded flanges save time and money and are great for piping systems with small diameters. They are also the only choice for flanges in areas with a high risk of explosions where welding is dangerous.

3. Weld Neck Flange

A weld neck flange is also called a high-hub flange or tapered hub flange. The pressure that builds up at the bottom of the flange may be reduced by using a weld neck flange with a neck that can move the tension in the pipe. 

It is suitable for pipes that function at both high and low temperatures and can resist high pressure. The connected pipe's diameter must match the flange's dimension. A circular fitting with a protruding edge all the way around makes up a weld neck flange. Weld neck flange has been effectively utilized even at a pressure as high as 5000 psi.

4. Socket Weld Flanges

Socket weld flanges are connected to pipes with a single fillet weld executed outside the flange (different from the slip-on flange type that requires two welds). To ensure that the pipe is positioned properly after the welding procedure, the pipe is inserted into the socket with a little gap.

A socket weld's bottom clearance aims to minimize any residual pressure that may build up at the weld root when the metal solidifies during the welding process.

Socket-weld flanges are appropriate for compact, high-pressure pipe systems carrying non-corrosive liquids.

5. Blind Flange

Blind flanges are made without a bore and are used to prevent the flow of fluids by sealing the ends of the pipes, valves, and pressure vessel openings.

Blind flanges must bear significant mechanical stress due to system pressure and bolting forces.

These flanges block a pipe or nozzle on a vessel while it is not in use. For pressure checks at a plant or simply because the customer does not use all the nozzles given on the tank, the nozzle is often blocked off using a blind flange.

When these flanges are fused with the right gaskets, they provide an excellent seal even in high-temperature conditions.

6. Lap Joint Flange

Lap joint flanges have a flat face and must be used in conjunction with a stub end at all times.

Unlike slip-on flanges, lap joint flanges have a radius where the flange face meets the bore. This is so that the flanged part of the stub end can fit.

Bolts are used to attach the lap joint flange to the stub end so that it may slide over the pipe. Since the lap joint flange may be constructed of lower-quality material than the stub, lap joint flanges provide a mechanical connection that is reasonably priced, lowering the total cost of the pipe system.

For stainless steel or nickel alloy pipelines, using lap joint flanges in combination with stub ends is an economically beneficial option since the material of the lap joint flange may be of a lower grade.

7. Long Neck Weld Flanges

Long welded neck flanges are used in high-pressure and high (or changing) temperature conditions, mostly in the oil and gas industry.

Long weld neck flanges are similar to standard weld neck flanges; however, the neck (tapered hub) is much longer and functions similarly to an extension bore.

The long weld-neck flange is often used in the process of anchoring water mains or gas sources that are pumped into a larger network of pipes, such as those found in a manufacturing facility or an apartment building.

Special Types of Flanges

1. Weldo Flange / Nipo Flange

A Nipoflange is made by combining a welding neck flange with a forged Nipolet for 90-degree branch pipes. Weldoflanges are a mixture of a weld neck flange and a branch fitting connector (a Weldolet in this case).

2. Elboflange and Latroflange

Other kinds of flange Olets that are less prevalent include the so-called "Elboflange," which is a combination of a flange and an Elbolet, and the "Latroflange" (combination of a flange with a Latrolet). Elboflanges are what are used in the process of branching off a pipeline at a 45-degree angle.

3. Orifice Flange

Orifice flanges are a type of flange used with orifice meters to determine the volumetric flow rate of either liquids or gases inside a certain pipeline.

4. Expanding Flange (Expander)

Expanding flanges, also called expander flanges, are used to increase the pipeline bore from one point to another or to connect pipes to mechanical equipment with different inlet sizes, such as pumps, compressors, and valves.

5. Reducing Flange (Reducer)

Reducing flanges, also called reducer flanges, do the opposite of what expander flanges do. Instead of making a pipe bigger, they make it smaller.

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