What is true about Class 300 flanges?

What is true about Class 300 flanges?

• A. Thicker Hub and Higher Pressure Rating than Class 150
• B. Thinner Hub and Lower Pressure Rating
• C. Same Hub and Rating
• D. Larger Bolt Circle

Answer: (A)

The main idea tested is how flange class relates to the flange’s strength and dimensions. For a given nominal pipe size, increasing the pressure class means the flange is designed to handle higher pressures, which requires a thicker hub and overall flange body to resist the greater stresses. Therefore, Class 300 flanges have a thicker hub and a higher pressure rating than Class 150 flanges. The bolt circle (the pattern and spacing of bolt holes) and the overall external dimensions for a given nominal size are standardized and do not increase just because the class number is higher, so the bolt circle is not larger in a higher-pressure class. That’s why the statement about a larger bolt circle isn’t correct. Similarly, the idea of the same hub and rating or a thinner hub doesn’t fit the needs of a higher pressure class.

The main idea tested is how flange class relates to the flange’s strength and dimensions. For a given nominal pipe size, increasing the pressure class means the flange is designed to handle higher pressures, which requires a thicker hub and overall flange body to resist the greater stresses. Therefore, Class 300 flanges have a thicker hub and a higher pressure rating than Class 150 flanges.

The bolt circle (the pattern and spacing of bolt holes) and the overall external dimensions for a given nominal size are standardized and do not increase just because the class number is higher, so the bolt circle is not larger in a higher-pressure class. That’s why the statement about a larger bolt circle isn’t correct. Similarly, the idea of the same hub and rating or a thinner hub doesn’t fit the needs of a higher pressure class.