Are you looking forward to selecting, buying, inspecting, or maintaining flanges for your plumbing system? It is important to understand their different characteristics to be able to select the right category. Keep reading as we dig deeper into flanges to highlight their functions and design to assist you in making the right decision.

What are Flanges and How Do They Work?

A flange is a protruding lip, ridge, or rim used to attach two objects, especially shafts and pipes, to help transfer torque or extend flow. In plumbing, using flanges is the second most preferred method of connecting a pipe with another, valves, or equipment like pumps.

Flanges are preferred in most cases because, unlike welding that makes joints permanent, they help to add flexibility by allowing for easier assembly and disassembly of various parts. If you take a closer look at a flanged connection, it comprises a number of parts, including flanges, bolting, and gasket. See the demonstration below:

In most cases, the bolting and gasket materials are designed from the approved or same as piping material that will be connected. Although this might not be a major issue in water plumbing systems, it is central when working with corrosive or reactive liquids. Common flange materials include chrome-moly, Inconel, and Monel.

Common Flange Types: What Are Their Characteristics?

When selecting flanges, know that there is no one-type-fits-all style. Indeed, everything, from size to durability, is different. So, here are the standard categories:

• Threaded Flanges

Also referred to as screwed type, these flanges are designed with threads inside the flange bore. During installation, the flange bore matches with the male thread on the plumbing fitting or pipe. Because of the threaded connection, it implies that you can avoid welding in most cases.

• Slip-On Flange

This category of flanges is very common and comes in a wide range of sizes to support high or low throughput. You only need to match the flange with the outer pipe diameter when selecting this type of flange for your equipment. However, installation is slightly different and more technical than others because you have to use fillet weld on each side to secure the flanges to the pipe.

• Lap Joint Flanges

These flanges are made with a two-piece design, and require butt welding of the stub end to the fitting or pipe using a backing flange to form the connection. The design makes the flange style very popular, especially for systems with limited physical space or that require regular maintenance/dismantling.

• Weld Neck Flanges

Just like lap joint flanges, the weld lap joint flange also requires welding for effective installation and operation. However, its integrity, performance in multiple repeat bends, and efficiency in high temperature/ high-pressure systems make it an excellent choice for high-demanding tasks.

• Blind Flanges

These flanges are used for isolating pipes. So, they are essentially boltable blank discs that can easily be removed from the system.

The above five flanges are the main categories, but additional specialty models are also available for specific environments. Good examples include nipoflanges, expanding flanges, reducing flanges, weldoflanges, and orifice. Remember that no matter the flange that you select, it is paramount also to have the right tools, such as wrenches or pneumatic tools, for installation.

How to Select the Right Flange Type: A Closer Look at Flange Dimensions

Now that you know the different types of flanges, there is one more thing before you can place an order: dimensions. When thinking about the flange dimensions, the most important section is the interface with the gasket and pipes for proper sizing. So, here are the main dimensions to consider:

• Outside diameter: This is the distance between two opposite sides of a flange face.
• Bolt diameter: This is the distance between opposing bolt holds when you measure them from center to center.
• Thickness: This measurement evaluates the thickness of the outer attaching rim of the flange.
• Pipe size: This is the designation of the pipe size that the flange corresponds to.
• Nominal bore size: This is the size of the flange connectors on the inner diameter.

In addition to these characteristics, flanges are also classified based on their ability to withstand temperatures and pressures. So, you might get them with suffixes, such as "#," "lb," or "class. Note that the pressure tolerances will vary based on the design, material used, and size. The only constant is that the pressure rating drops as the temperature goes up.

As you can see, flanges are critical plumbing fittings, and it is prudent to get them right for the effective functioning of your system. In addition to this guide, it will also be a good idea to work with a technician so that you can determine the exact working condition of the plumbing line or facility. Do not just look for any flange; go for the best!