Flange Dimensions & Weights for ANSI Flanges
Flange Dimensions & Weights for ANSI Flanges
ANSI (American National Standards Institute) flanges are essential components in piping systems, ensuring secure connections between pipes, valves, and equipment. These flanges are classified by pressure ratings, dimensions, and material specifications to ensure compatibility and safety across various industrial applications.
ASME/ANSI B16.5 Flanges and Bolt Dimensions
The ASME/ANSI B16.5 standard provides comprehensive specifications for flange dimensions, bolt patterns, and pressure ratings. Below is a reference table for Class 300 flanges:
ASME/ANSI B16.5 Flanges and Bolt Dimensions - Class 300
| Nominal Pipe Size (NPS) | Flange Diameter (inches) | Number of Bolts | Bolt Diameter (inches) | Bolt Hole Diameter (inches) | Bolt Circle (inches) |
|---|---|---|---|---|---|
| 1/4 | 3.38 | 4 | 1/2 | 0.62 | 2-1/4 |
| 3/8 | 3.62 | 4 | 1/2 | 0.62 | 2-5/8 |
| 1/2 | 3.88 | 4 | 1/2 | 0.62 | 3 |
| 3/4 | 4.62 | 4 | 5/8 | 0.75 | 3-1/2 |
| 1 | 4.88 | 4 | 5/8 | 0.75 | 3-7/8 |
| 1-1/4 | 5.25 | 4 | 5/8 | 0.75 | 4-1/4 |
| 1-1/2 | 6.12 | 4 | 3/4 | 0.88 | 4-7/8 |
| 2 | 6.50 | 4 | 3/4 | 0.88 | 5-1/2 |
| 2-1/2 | 7.50 | 4 | 3/4 | 0.88 | 6-3/8 |
| 3 | 8.25 | 4 | 3/4 | 0.88 | 7 |
| 3-1/2 | 9.00 | 8 | 3/4 | 0.88 | 7-5/8 |
| 4 | 10.00 | 8 | 3/4 | 0.88 | 8-1/2 |
| 5 | 11.00 | 8 | 3/4 | 0.88 | 9-1/2 |
| 6 | 12.50 | 8 | 3/4 | 0.88 | 10-5/8 |
| 8 | 15.00 | 8 | 7/8 | 1.00 | 13 |
| 10 | 17.50 | 12 | 1 | 1.12 | 15-1/4 |
| 12 | 20.62 | 12 | 1 | 1.12 | 17-3/4 |
| 14 | 23.00 | 12 | 1-1/8 | 1.25 | 20-1/4 |
| 16 | 25.25 | 16 | 1-1/8 | 1.25 | 22-1/2 |
| 18 | 27.75 | 16 | 1-1/4 | 1.38 | 24-3/4 |
| 20 | 30.00 | 20 | 1-1/4 | 1.38 | 27 |
| 24 | 36.00 | 20 | 1-1/2 | 1.62 | 32 |
ANSI Flange Dimensions
ANSI flanges follow standard dimensions set by ASME B16.5 (for pipe sizes up to 24 inches) and ASME B16.47 (for larger sizes). Understanding these key dimensions is essential for proper flange selection and installation.
Key Dimensions
Outer Diameter (OD) The overall diameter of the flange determines the space required for installation and affects the bolt circle diameter and number of bolt holes.
Bolt Circle Diameter (BCD) The diameter of the circle on which the bolt holes are centered. This dimension is critical for ensuring proper alignment between mating flanges.
Bolt Hole Diameter & Number of Holes The size and number of bolt holes must match between mating flanges to ensure proper bolting and sealing. The bolt hole diameter is typically slightly larger than the bolt diameter to allow for alignment.
Flange Thickness The thickness of the flange affects its pressure handling capacity. Higher pressure classes require thicker flanges to withstand the increased stress.
Raised Face (RF) or Flat Face (FF) The face type determines the gasket seating surface. Raised face flanges have a small raised area (typically 1/16" for Classes 150 and 300, 1/4" for higher classes), while flat face flanges have a completely flat surface.
Hub Diameter & Length For weld neck flanges, the hub dimensions vary depending on the flange type and size. The hub provides a smooth transition from the pipe to the flange, reducing stress concentrations.
ANSI Flange Pressure Classes & Their Dimensions
Flanges are categorized based on pressure ratings, ranging from Class 150 to Class 2500. Each class has specific dimensional requirements that increase with the pressure rating. Here's a general guide to dimensions for common ANSI flange classes:
Class 150 Flange Dimensions (Example for 6" Pipe Size)
- Outer Diameter (OD): 11.00 inches
- Bolt Circle Diameter (BCD): 9.50 inches
- Bolt Holes: 8 holes, 0.88-inch diameter
- Thickness: 0.88 inches
- Weight: Approximately 22 lbs (varies by material)
Class 300 Flange Dimensions (Example for 6" Pipe Size)
- Outer Diameter (OD): 12.50 inches
- Bolt Circle Diameter (BCD): 10.62 inches
- Bolt Holes: 8 holes, 0.88-inch diameter
- Thickness: 1.12 inches
- Weight: Approximately 37 lbs
Class 600 Flange Dimensions (Example for 6" Pipe Size)
- Outer Diameter (OD): 14.00 inches
- Bolt Circle Diameter (BCD): 12.00 inches
- Bolt Holes: 8 holes, 1.00-inch diameter
- Thickness: 1.50 inches
- Weight: Approximately 70 lbs
ANSI Flange Weights
The weight of a flange depends on its material, pressure rating, and size. Different materials have different densities, which directly affect the weight. Here's an estimated weight chart for different ANSI flange classes for a 6-inch nominal pipe size:
Weight Chart (6" NPS, Weld Neck Flange)
| Flange Class | Weight (lbs) |
|---|---|
| 150 | 22 |
| 300 | 37 |
| 600 | 70 |
| 900 | 120 |
| 1500 | 190 |
| 2500 | 320 |
Note: Weights are approximate and vary by material. Carbon steel and stainless steel have similar weights, while alloy materials may differ.
For larger pipe sizes and higher pressure classes, weights increase significantly due to additional material thickness and reinforcement required to handle the increased pressure and stress.
Selecting the Right Flange
When choosing an ANSI flange, consider the following factors:
Operating Pressure & Temperature
Ensure the flange class meets or exceeds your system's maximum operating pressure at the highest operating temperature. Refer to pressure-temperature rating tables in ASME B16.5 for specific values.
Material Selection
Common materials include:
- Carbon Steel: For general applications
- Stainless Steel: For corrosion resistance
- Alloy Steel: For high-temperature applications
- Special Alloys: For extreme environments
Gasket Compatibility
The face type (Raised Face or Ring Type Joint) determines the gasket type required. Ensure compatibility between the flange face, gasket material, and operating conditions.
Application Requirements
The flange type (weld neck, slip-on, blind, etc.) affects performance and installation. Consider factors such as:
- System criticality
- Maintenance requirements
- Installation constraints
- Cost considerations
For more detailed flange dimension charts and weight calculations, visit: TEXAS FLANGE DIMS / WEIGHTS