Introduction to Flanges | Types Of Flanges

A flange is a method of connecting valves, pipes, pumps, and other equipment to form a piping system.

The primary purpose of flanges is to provide attachments to connect pipes, valves, and other equipment. Flanges are usually attached by screwing or welding them to pipelines. The flanges are secured to pipelines with the help of welding or bolts.

Types of Flanges

The standard flanges used in the Petro and Chemical industry are:

· Welding Neck Flange

· Slip-On Flange

· Socket Weld Flange

· Lap Joint Flange

· Threaded Flange

· Blind Flange

#1. Welding Neck Flange

It features a long tapered hub that can be welded with a pipe.

Usually, it is used in high-pressure and high/low temperatures applications, requiring an unhindered fluid flow through the piping system. The tapered hub allows a smooth distribution of the mechanical stress between the pipe and the weld neck flange. It also facilitates the execution of radiographic inspections to detect possible leakages and welding defects.

#2. Slip-on Flange

Technicians use two fillet welds to connect slip-on flange to the pipe or the fittings. The one end of the fillet is welded inside and one outside the cavity of the flange. The diameter of a slip-on flange is larger than the outside diameter of the connecting pipe. These flanges are also known as “Hubbed Flanges.” You can easily recognize them due to their slim and compact shape.

#3. Socket Weld Flange

Professionals use a single fillet weld to connect Socket weld flanges to pipes. The single fillet weld is executed on the outer side of the flange. The Socket Weld Flanges are mainly used for small-size and high-pressure piping that does not transfer highly corrosive fluids. These flanges corrode easily due to the gap area between the pipe’s end and the socket’s shoulder. They have static strength similar to slip-on flanges’; however, fatigue strength is higher due to a single, instead of double, fillet weld.

#4. Lap Joint Flange

These flanges feature a flat face, primarily used along with a stub end. The lap joint flanges along with stub ends are a cost-effective alternative for nickel alloy or stainless steel pipelines. This pairing has two advantages:

· It reduces the overall cost of the pipeline’s flanged joints as it reduces the usage of high-grade materials.

· The bolting operations get simplified, as the lap joint flange can easily rotate around the pipe to bolster alignment.

#5. Threaded Flange

Threaded flanges are joined to pipelines by screwing the pipe. They are available in sizes up to 4 inches and multiple pressure ratings. However, they are mainly used for small-size piping in low pressure and low-temperature applications, like water and air utility services. These flanges are mandatory requirements for gas pipelines; welding these pipes can lead to potential danger.

#6. Blind Flange

These flanges have holes in their center. They’re mainly used to seal valve/pressure vessels, pipelines and stop fluid flow. The blind flanges should be strong enough to withstand mechanical stress due to system pressure and the required bolting forces. The flanges make pipelines easily accessible as the blind flanges can be easily bolted.

If you still have any doubts about flanges, do let us know in the comment section.