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Factors to Consider When Choosing Flanges for Your Industrial Piping System

Flanges play a vital role in the gas and oil piping system, connecting valves with other equipment. Pipe flanges are the second-most commonly used joining mechanism after welding.

It also provides added flexibility that allows easier disassembly and assembly of pipe systems. They provide easy access during the inspection, repairs, and cleaning of natural gas and oil pipelines.

Here are a few factors to keep in mind during the flange selection process:

Flange types

Flanges come in different types for industrial use. You may need to choose carefully an ideal flange design that fits well with your piping system. The most common type of flanges used in the petrochemical industry are:

1. Slip-on flange

2. Welding neck flange (buttweld)

3. Socket weld flange (counterbore)

4. Blind flange

5. Lap joint flange (rotating flange)

6. Threaded (companion) flange

pipe flanges

Other special flanges commonly used in the gas and oil industry include:


Reducing flange

Expander flange

Orifice flange

Long weld neck flanges

The flange face types and design may have a significant impact on the piping system’s final performance.


Forged carbon steel pipes are one of the common types present in the market. Additionally, you can find flanges manufactured from bronze, cast iron, aluminum, and stainless steel. You may also find flanges with specialty metals like Monel, Inconel, and chrome-moly.

The type of material used depends on the piping systems and industrial application. It is to ensure that they are strong and durable enough in the long run. However, in most instances, the flanges and pipes are made of the same material.


If you want a flange in a proper fit, you need to look into the flange dimensions and size. You need to be keen on how the flange interfaces with the pipes and gaskets to ensure an ideal size. Below are a few standard dimension considerations:

1. Pipe size

2. Thickness

3. Bolt circle diameter

4. Inner diameter

5. Nominal bore size

6. Outside diameter


All flanges fall under different categories specified by ASTM or ASME standards. Characteristics of a specific flange type impact its performance across a range of industrial environments. Steel pipes are available in a variety of pressure classes and styles. The classification of metal flanges is from 150 to 2500# rating. Some standard classifications used in petrochemical industries include:

2500# (and higher for API)






The different categories vary depending on the temperature and pressure tolerances, flange size, design, or material used. The pressure ratings may decrease with the rise in temperature.


Depending on how thick the flange is, it is easy to determine the high pressure it can handle, in any application thicker flange can resist higher pressures.

Bolt holes

Bolt holes make it easy to measure the size of the pressure class and flange. The number of bolt holes, pitch circle diameter, and the actual bolt hole size on the flanges are 3 factors that need to be addressed.

Pressure class

Pressure class helps to understand the marginal pressure level under which the flange can function safely and sustain. Each standard has several levels of pressure available, from high-pressure to low-pressure tolerance. The pressure level of the products to which the flange will be connected must be the same as the valves and pipes in the process.

Statistics on Industrial Pipeline

The Pipeline and Hazardous Materials Safety Administration under the US Department of Transportation have made an estimate which shows approximately 1,585,672 miles of natural gas pipeline and 160,521 miles of liquid petroleum pipeline across the nation. Over 28.3 trillion cubic feet of natural gas was delivered to consumers in 2019 via the gas-integrated transportation network.


There’s an endless list of factors to consider when you choose flanges for the Industrial Pipeline system. However, the given above are a few specific or crucial ones you must not skip out.

We hope that with the help of this guide, you will be able to identify the key things before purchasing flanges. To learn more about flange basics, visit


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