Introduction

If you need to come into contact with the industrial pipeline industry, you may encounter the professional term “flange class”. So what does it mean, you need to understand it. Does it refer to specifications, dimensions, weight? Or does it refer to production standards? You don’t need to obtain a professional engineering certificate to understand it. This article will provide a simple explanation of this professional term, using common language to introduce it, so that even those who are new to the product of flanges can understand what “flange class” is.

What are Flange Pressure Classes?

The flange grade is the pressure rating that a specific model of flange can withstand based on production standards. If it is ASME/ANSI standard, flange grades usually include: 150 #, 300 #, 600 #, 900 #, 1500 #, etc. The higher the flange grade, the higher the pressure and temperature it can withstand. Of course, the higher the grade, the thicker it will be.

Why Do Flange Classes Matter?

The level of flanges is related to their specific application scenarios and locations. Because the flanges required in pipeline systems can withstand different pressures and temperatures. Valves require higher grade flanges.
If the flange grade selection is incorrect, it may cause the following effects:

• Leakage of liquid or gas.
• Equipment failure caused by high temperature or high pressure.
• In severe cases, there may be risks to the safety of operators.

So choosing the appropriate grade of flange is very important in pipeline systems.

What is the Difference Between Class 150, 300, and 600 Flanges?

Class 150, 300600 are three commonly used flange grades, with the following differences:

Class 150 flange

• The pressure rating is 285 psi at 100 ° F (20 bar at 38 ° C).
• The main uses are: plumbing pipes in low-pressure piping systems, and some household piping systems.

Class 300 flange

• Pressure rating: 740 psi at 100 ° F (51 bar at 38 ° C)
• The main applications are: medium and low pressure industrial pipeline systems, such as chemical plants and petroleum pipeline systems.

Class 600 flange

• Pressure rating: 1480 psi at 100 ° F (102 bar at 38 ° C)
• The main applications are: medium and high pressure industrial pipeline systems. For example, oil and gas pipeline systems.

The higher the pressure level, the higher the price.

How Do You Determine Flange Class?

During flange production, different pressure levels will be produced according to the required standards. How to determine which grade of flange to use in a pipeline system?

The following three factors are available for reference:

1. Material of the overall pipeline: Different materials can withstand different pressure levels and temperatures. Among the three materials of carbon steel, stainless steel, and alloy steel, stainless steel of the same grade can withstand higher pressure.
2. Working temperature of pipeline system: The pressure tolerance of flanges will decrease with increasing temperature, so higher grade flanges should be selected according to the specific temperature they can withstand. A 300 level flange may not be able to withstand the same pressure at 100 ° F (approximately 37 ° C) as at 600 ° F (approximately 184 ° C).
3. Maximum pressure level in the pipeline: To ensure the safety of the overall pipeline system, it is necessary to choose flanges that are one level higher than the working pressure.

Flange Class Chart (Simplified)

The following are the pressure levels that carbon steel flanges of different grades can withstand at a temperature of 100 ° F (approximately 37 ° C):

Note: The actual rated value may vary depending on the material and temperature.

Flange Classes vs Schedules

The flange grade and pipeline diameter are two different ways of representing specifications in different products.

• The flange grade indicates the pressure that the flange can withstand.
• The pipe diameter represents the wall thickness of the pipe fittings.

Although they represent different products, they are also related because they need to be connected. Select the same caliber for welding according to different specifications.

How to Identify Flange Class

The method of identifying the grade of flanges is relatively simple and can be carried out from the following two aspects:

• Check the markings: Usually, after the flange production is completed, the manufacturer will mark its specifications.
• Check thickness: Flanges produced according to standards have a fixed thickness, so checking the thickness can determine the grade of the flange.

Common Uses of Different Flange Classes

Different grades of flanges have different purposes. Introduce its use using conventional 150,300,600.

1. Class 150: Household piping system, HVAC system.
2. Class 300: Water supply pipeline system, medium pressure chemical system.
3. Class 600: Oil and gas pipeline systems, high-pressure steam systems.

In short, the higher the pressure level, the more suitable industrial pipeline systems are.

Summary

The pressure rating of a flange represents the pressure rating and temperature that the flange can withstand under this standard.

• Class 150 is commonly used for low-voltage daily use.
• Class 300-600 levels are commonly used in medium and low pressure industrial pipeline systems.
• Class 900 level and below are mostly used for high-pressure and high-temperature pipeline systems.

The higher the pressure level, the higher the tolerable pressure level and the stronger the strength.

Therefore, the choice of flange grade must be based on the actual application scenario. Choosing the wrong option may pose a certain level of danger.