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ANSI Flange Dimensions Chart
Contents
- 1 1. What Is an ANSI Flange?
- 2 2. ANSI Flange Standards and ASME B16.5
- 3 3. Key ANSI Flange Dimensions and Terminology
- 4 4. ANSI Flange Pressure Classes: 150, 300, 400, 600, 900, 1500, and 2500
- 5 5. Complete ANSI Flange Dimensions Chart
- 6 6. ANSI Class 150 Flange Dimensions Chart
- 7 7. ANSI Class 300 and Class 600 Flange Dimensions Charts
- 8 8. ANSI Class 900, 1500, and 2500 Flange Dimensions Charts
- 9 9. How to Read and Measure ANSI Flange Dimensions
- 10 10. How to Select the Correct ANSI Flange Size and Pressure Class
- 10.1 Determine the nominal pipe size
- 10.2 Establish the design pressure and temperature
- 10.3 Select a suitable flange material
- 10.4 Choose the flange type
- 10.5 Select the flange facing
- 10.6 Verify mating-flange compatibility
- 10.7 Select the gasket and bolting
- 10.8 Consider external piping loads
- 10.9 Final flange selection checklist
- 11 Conclusion
ANSI flanges are widely used to connect pipes, valves, pumps, pressure vessels, and other equipment in industrial piping systems. Their standardized dimensions allow components from different manufacturers to be assembled while maintaining proper alignment, pressure containment, and sealing performance.
An ANSI flange dimensions chart provides essential measurements such as outside diameter, flange thickness, bolt circle diameter, number of bolt holes, bolt-hole diameter, and raised-face dimensions. These values vary according to the nominal pipe size, flange type, and pressure class.
Although the term “ANSI flange” remains common in the piping industry, most dimensional requirements are now published by the American Society of Mechanical Engineers (ASME). For example, ASME B16.5 covers pipe flanges and flanged fittings from NPS ½ through NPS 24, while ASME B16.47 covers larger flanges from NPS 26 through NPS 60.
This guide explains ANSI/ASME flange dimensions, pressure classes, terminology, and measurement methods. It also provides dimensional charts to help engineers, fabricators, purchasers, and maintenance personnel select compatible flanges for their piping systems.
1. What Is an ANSI Flange?
An ANSI flange is a standardized mechanical component used to create a removable connection between sections of pipe or between a pipe and another piece of equipment. Two flanges are normally joined using bolts or studs, with a gasket installed between their sealing faces to prevent fluid leakage.
The expression “ANSI flange” refers to flanges manufactured according to dimensional and pressure-temperature standards originally developed or approved by the American National Standards Institute. However, ANSI does not directly design or manufacture flanges. Today, the relevant standards are primarily maintained by ASME, so the technically correct term is usually “ASME flange” or “ANSI/ASME flange.”
Common standards include:
- ASME B16.5: Pipe flanges and flanged fittings from NPS ½ to NPS 24.
- ASME B16.47: Large-diameter steel flanges from NPS 26 to NPS 60.
- ASME B16.36: Orifice flanges used for differential-pressure flow measurement.
- ASME B16.48: Line blanks, including spectacle blinds, spades, and spacers.
ANSI/ASME flanges are available in several configurations, including weld neck, slip-on, socket weld, threaded, lap joint, and blind flanges. Each design provides a different method of connecting to the pipe and is suited to particular pressure, temperature, maintenance, and installation requirements.
Flanges are also assigned pressure classes such as Class 150, 300, 400, 600, 900, 1500, and 2500. The class number is not the flange’s maximum working pressure in psi. Its actual pressure rating depends on the flange material and operating temperature, as specified in the applicable ASME pressure-temperature tables.
For two ANSI flanges to connect correctly, several characteristics must be compatible:
- Nominal pipe size
- Pressure class
- Flange standard
- Flange facing type
- Bolt-hole quantity and diameter
- Bolt-circle diameter
- Gasket dimensions
- Material and pressure-temperature rating
Standardizing these features makes ANSI/ASME flanges interchangeable within the limits of the applicable standard, simplifying piping design, component replacement, fabrication, and maintenance.
2. ANSI Flange Standards and ASME B16.5
The term “ANSI flange” is still commonly used in the piping industry, but most modern flange dimensions and pressure-temperature ratings are established by ASME standards. ANSI approves the standards, while ASME develops and maintains the technical requirements.
The principal standards associated with ANSI/ASME flanges include:
| Standard | Scope |
|---|---|
| ASME B16.5 | Pipe flanges and flanged fittings from NPS ½ to NPS 24 |
| ASME B16.47 | Large-diameter steel flanges from NPS 26 to NPS 60 |
| ASME B16.36 | Orifice flanges used in flow-measurement systems |
| ASME B16.48 | Spectacle blinds, spades, and ring spacers |
| ASME B16.20 | Metallic gaskets for pipe flanges |
| ASME B16.21 | Nonmetallic flat gaskets for pipe flanges |
| ASME B16.25 | Butt-welding end preparation |
| ASME B16.1 | Gray iron pipe flanges and flanged fittings |
| ASME B16.42 | Ductile iron pipe flanges and flanged fittings |
ASME B16.5 flange size range
ASME B16.5 is the primary standard used for steel pipe flanges. It covers nominal pipe sizes from NPS ½ through NPS 24 and includes the following pressure classes:
- Class 150
- Class 300
- Class 400
- Class 600
- Class 900
- Class 1500
- Class 2500
The standard specifies critical dimensional and technical requirements, including:
- Flange outside diameter
- Flange thickness
- Bolt-circle diameter
- Number and diameter of bolt holes
- Flange facing dimensions
- Hub dimensions
- Bore dimensions
- Dimensional tolerances
- Materials and markings
- Pressure-temperature ratings
- Testing and inspection requirements
ASME B16.5 covers weld neck, slip-on, socket-weld, threaded, lap-joint, and blind flanges. However, not every flange type is available in every nominal size and pressure class.
ASME B16.47 for large-diameter flanges
Flanges larger than NPS 24 are generally covered by ASME B16.47. This standard applies to steel flanges from NPS 26 through NPS 60 in Classes 75, 150, 300, 400, 600, and 900.
ASME B16.47 includes two flange series:
- Series A: Generally heavier and designed with larger bolt diameters and fewer bolt holes.
- Series B: Generally lighter, with smaller bolt diameters and a greater number of bolt holes.
Series A and Series B flanges of the same nominal size and pressure class are not normally interchangeable because their outside diameters, bolt circles, bolt quantities, and bolt-hole dimensions may differ.
ANSI class and actual working pressure
A common mistake is to treat the flange class number as its allowable working pressure in psi. For example, a Class 300 flange is not automatically rated for 300 psi under all operating conditions.
The actual allowable pressure depends on:
- Flange material group
- Operating temperature
- Pressure class
- Applicable ASME standard
- Gasket and bolting limitations
The pressure-temperature tables in ASME B16.5 or ASME B16.47 must therefore be consulted when determining the allowable working pressure.
3. Key ANSI Flange Dimensions and Terminology
Understanding flange terminology is essential when reading an ANSI flange dimensions chart. The chart measurements define whether a flange will fit the pipe, align with the mating flange, and provide a reliable sealed connection.
Nominal Pipe Size
Nominal Pipe Size, abbreviated as NPS, identifies the approximate pipe size connected to the flange. It is a nominal designation rather than a direct measurement of the pipe’s inside or outside diameter.
For NPS ¹⁄₈ through NPS 12, the NPS value does not equal the actual pipe outside diameter. From NPS 14 upward, the nominal size generally matches the pipe outside diameter in inches.
A flange must be selected according to the pipe’s NPS and, where applicable, its wall thickness or schedule.
Flange outside diameter
The flange outside diameter, usually represented by O or D, is the maximum diameter measured across the flange body. It affects the amount of installation space required around the flange.
The outside diameter generally increases with:
- Nominal pipe size
- Pressure class
- Flange design
- Applicable dimensional standard
Higher-pressure flanges are usually larger and thicker because they require stronger bolting and greater structural capacity.
Flange thickness
Flange thickness, commonly represented by T, is measured from the back of the flange to the basic flange face. The raised face is normally excluded unless the chart or drawing specifically states otherwise.
A thicker flange provides greater resistance to bending caused by bolt preload and internal pressure. Flange thickness generally increases as the pressure class rises.
Bolt-circle diameter
Bolt-circle diameter, also called BCD, PCD, or diameter of bolt circle, is the diameter of the imaginary circle passing through the centers of all bolt holes.
The bolt-circle diameter must match between mating flanges. Even if two flanges have the same NPS and outside diameter, they cannot be connected if their bolt-circle dimensions differ.
Number of bolt holes
The number of bolt holes varies according to flange size and pressure class. The holes are equally spaced around the bolt circle to distribute gasket-compression force uniformly.
A standard flange joint should use every specified bolt hole. Operating a flange with missing bolts can produce uneven gasket loading, flange rotation, and leakage.
Bolt-hole diameter
Bolt-hole diameter is slightly larger than the nominal bolt or stud diameter. This clearance helps accommodate manufacturing tolerances and simplifies flange alignment during installation.
For example, a flange designed for ¾-inch bolts may have bolt holes larger than ¾ inch. Therefore, bolt size should not be determined solely by measuring the bolt hole.
Flange bore
The flange bore is the central opening through which the process fluid flows. Its dimensions depend on the flange type and the pipe wall thickness.
For weld neck and socket-weld flanges, the bore may be specified according to the pipe schedule. Matching the flange bore with the pipe’s inside diameter helps maintain a smooth flow path and reduces turbulence.
Raised-face diameter and height
A raised-face flange has a circular sealing surface elevated above the main flange face. Its diameter provides the seating area for the gasket.
Typical raised-face heights are:
- Class 150 and 300: approximately 1.6 mm or 1⁄16 inch
- Class 400 and above: approximately 6.4 mm or ¼ inch
Raised-face height is generally additional to the listed minimum flange thickness, although the applicable standard and dimensional notes should always be checked.
Hub diameter and hub length
Weld neck, slip-on, socket-weld, and threaded flanges may include a hub. Important hub dimensions include:
- Diameter at the base of the hub
- Diameter at the welding end
- Hub length
- Transition profile
The tapered hub of a weld neck flange transfers stress gradually from the flange into the pipe, making it suitable for high-pressure, high-temperature, cyclic, and severe-service applications.
Flange facing
The flange facing is the surface that contacts the gasket. Common facing types include:
- Raised Face (RF)
- Flat Face (FF)
- Ring-Type Joint (RTJ)
- Tongue-and-Groove
- Male-and-Female
Mating flanges must have compatible facing arrangements. The gasket must also be selected for the facing type, flange class, process fluid, pressure, and temperature.
4. ANSI Flange Pressure Classes: 150, 300, 400, 600, 900, 1500, and 2500
ANSI/ASME pressure classes categorize flanges according to their pressure-temperature capability and dimensional design. ASME B16.5 includes Classes 150, 300, 400, 600, 900, 1500, and 2500.
As the pressure class increases, a flange generally becomes thicker and may have a larger outside diameter, larger bolts, or more bolt holes. However, the exact dimensional changes depend on the nominal pipe size and flange type.
Class 150
Class 150 is the most common low-pressure flange class. It is widely used in:
- Low-pressure water piping
- Cooling-water systems
- Utility air systems
- Low-pressure steam service
- General chemical-processing systems
- Fire-water piping
Despite its designation, a Class 150 flange is not limited to 150 psi. At ambient temperature, some materials may have an allowable pressure higher than 150 psi. The rating decreases as operating temperature increases.
Class 300
Class 300 flanges are heavier and stronger than Class 150 flanges. They typically have greater flange thickness, larger bolts, and different bolt-circle dimensions.
Common applications include:
- Medium-pressure steam
- Oil and gas processing
- Chemical plants
- Refinery piping
- Compressed-gas systems
- High-pressure utility services
A Class 300 flange cannot normally be directly bolted to a Class 150 flange because their dimensions and drilling patterns differ.
Class 400
Class 400 is less frequently used than Classes 300 and 600. It is available for applications requiring pressure capacity between these two common classes.
Because Class 400 components may be less readily available, designers often select Class 600 when greater standardization, inventory availability, or future replacement is important.
Class 600
Class 600 flanges are commonly used for high-pressure and high-temperature process services. Typical applications include:
- Refinery process lines
- Petrochemical systems
- High-pressure steam
- Gas transmission
- Offshore facilities
- Power-generation systems
Class 600 flanges have heavier bodies and stronger bolting arrangements than lower-class flanges. Correct bolt tightening and gasket selection become increasingly important because of the higher joint loads.
Class 900
Class 900 flanges are designed for severe pressure and temperature conditions. They are often found in:
- High-pressure oil and gas production
- Compressor discharge systems
- High-pressure steam systems
- Process injection lines
- Offshore and subsea facilities
Ring-Type Joint facings are frequently selected for Class 900 service, particularly where high pressure or cyclic loading requires a robust metal-to-metal sealing arrangement.
Class 1500
Class 1500 flanges are used for very-high-pressure services where joint integrity is critical. Their heavy construction requires careful consideration of piping loads, equipment nozzle capacity, installation clearance, and lifting requirements.
Typical applications include high-pressure gas processing, chemical injection, wellhead-related systems, and high-pressure process piping.
Class 2500
Class 2500 is the highest pressure class included in ASME B16.5. These flanges are exceptionally thick and require large-diameter, high-strength bolting.
Typical applications include:
- Very-high-pressure gas systems
- High-pressure injection service
- Critical refinery processes
- Specialized chemical-processing systems
- Severe high-pressure equipment connections
Class 2500 flanges are available only in a limited size range compared with lower pressure classes.
Comparison of ANSI flange pressure classes
| Pressure class | General service level | Typical applications |
|---|---|---|
| Class 150 | Low pressure | Water, air and low-pressure utilities |
| Class 300 | Medium pressure | Steam, chemical and refinery piping |
| Class 400 | Medium to high pressure | Specialized industrial systems |
| Class 600 | High pressure | Refinery, petrochemical and power systems |
| Class 900 | Severe high pressure | Oil and gas, high-pressure steam |
| Class 1500 | Very high pressure | Gas processing and injection systems |
| Class 2500 | Extremely high pressure | Critical and specialized process service |
Pressure class selection must be based on the pressure-temperature rating for the exact flange material rather than a general class description. The flange, gasket, bolting, valves, and connected piping components must all be suitable for the system’s design pressure, design temperature, fluid, and service conditions.
5. Complete ANSI Flange Dimensions Chart
An ANSI flange dimensions chart identifies the measurements needed to confirm whether two flanges can be connected. The most important dimensions are the flange outside diameter, minimum thickness, bolt-circle diameter, number of bolt holes, and bolt-hole diameter.
The following symbols are commonly used in flange dimensional tables:
| Symbol | Dimension | Description |
|---|---|---|
| NPS | Nominal Pipe Size | Nominal size of the connected pipe |
| OD | Outside Diameter | Maximum diameter across the flange |
| T | Flange Thickness | Minimum thickness of the flange body |
| BCD | Bolt-Circle Diameter | Diameter through the centers of the bolt holes |
| n | Number of Holes | Total number of equally spaced bolt holes |
| d | Bolt-Hole Diameter | Diameter of each drilled bolt hole |
| RF | Raised Face | Raised gasket-contact surface |
| Bore | Internal Opening | Central opening through the flange |
| X | Hub Diameter | Diameter at the base of the flange hub |
| Y | Flange Length | Overall length through the hub |
| A | Weld-End Diameter | Outside diameter at the welding end |
Dimensions controlled by pressure class
For a given nominal pipe size, several flange dimensions change when the pressure class changes:
- Outside diameter
- Flange thickness
- Bolt-circle diameter
- Number of bolt holes
- Bolt-hole diameter
- Required bolt or stud size
- Raised-face diameter
- Ring-joint dimensions, when applicable
Therefore, pipe size alone is not enough to determine flange compatibility. For example, an NPS 4 Class 150 flange has a different drilling pattern from an NPS 4 Class 300 flange.
Dimensions controlled by flange type
Some dimensions also vary according to flange type:
- Weld neck flange: bore, hub diameter, weld-end diameter and overall length
- Slip-on flange: bore, hub diameter and overall length
- Socket-weld flange: socket bore, socket depth and pipe bore
- Threaded flange: threaded bore and thread dimensions
- Lap-joint flange: bore, hub and corner radius
- Blind flange: flange thickness and internal profile
The outside diameter, bolt circle, number of holes and bolt-hole diameter are generally common to different flange types within the same NPS and pressure class. However, thickness and hub-related dimensions may vary by flange type.
Metric and inch dimensions
ANSI/ASME flange charts may present dimensions in either inches or millimetres. The basic conversion is:
Millimetres = inches × 25.4
Converted metric values may contain decimals because the original ASME dimensions are normally based on inch units. When inspecting a flange, the standard values and applicable dimensional tolerances should be used instead of rounding measurements excessively.
Important chart limitations
The tables below show the principal dimensions used for flange identification and bolt-pattern matching. Detailed manufacturing dimensions—such as bores, hubs, welding ends, facing finishes and tolerances—must be selected according to:
- Flange type
- Pipe schedule
- Material
- Facing type
- Pressure class
- Applicable standard edition
The charts should not be used alone to establish the allowable working pressure. Pressure-temperature ratings must be checked separately using the flange material group and operating temperature.
6. ANSI Class 150 Flange Dimensions Chart
Class 150 flanges are widely used for water, air, oil, low-pressure steam and general industrial piping. The table below presents the principal ASME B16.5 Class 150 drilling dimensions in inches.
| NPS | Flange OD (in.) | Min. Thickness (in.) | Bolt Circle (in.) | No. of Holes | Hole Diameter (in.) |
|---|---|---|---|---|---|
| ½ | 3.50 | 0.44 | 2.38 | 4 | 0.62 |
| ¾ | 3.88 | 0.50 | 2.75 | 4 | 0.62 |
| 1 | 4.25 | 0.56 | 3.12 | 4 | 0.62 |
| 1¼ | 4.62 | 0.62 | 3.50 | 4 | 0.62 |
| 1½ | 5.00 | 0.69 | 3.88 | 4 | 0.62 |
| 2 | 6.00 | 0.75 | 4.75 | 4 | 0.75 |
| 2½ | 7.00 | 0.88 | 5.50 | 4 | 0.75 |
| 3 | 7.50 | 0.94 | 6.00 | 4 | 0.75 |
| 3½ | 8.50 | 0.94 | 7.00 | 8 | 0.75 |
| 4 | 9.00 | 0.94 | 7.50 | 8 | 0.75 |
| 5 | 10.00 | 0.94 | 8.50 | 8 | 0.88 |
| 6 | 11.00 | 1.00 | 9.50 | 8 | 0.88 |
| 8 | 13.50 | 1.12 | 11.75 | 8 | 0.88 |
| 10 | 16.00 | 1.19 | 14.25 | 12 | 1.00 |
| 12 | 19.00 | 1.25 | 17.00 | 12 | 1.00 |
| 14 | 21.00 | 1.38 | 18.75 | 12 | 1.12 |
| 16 | 23.50 | 1.44 | 21.25 | 16 | 1.12 |
| 18 | 25.00 | 1.56 | 22.75 | 16 | 1.25 |
| 20 | 27.50 | 1.69 | 25.00 | 20 | 1.25 |
| 22 | 29.50 | 1.81 | 27.25 | 20 | 1.38 |
| 24 | 32.00 | 1.88 | 29.50 | 20 | 1.38 |
Class 150 dimensions in millimetres
| NPS | Flange OD (mm) | Min. Thickness (mm) | Bolt Circle (mm) | No. of Holes | Hole Diameter (mm) |
|---|---|---|---|---|---|
| ½ | 88.9 | 11.2 | 60.3 | 4 | 15.7 |
| ¾ | 98.6 | 12.7 | 69.9 | 4 | 15.7 |
| 1 | 108.0 | 14.2 | 79.2 | 4 | 15.7 |
| 1¼ | 117.3 | 15.7 | 88.9 | 4 | 15.7 |
| 1½ | 127.0 | 17.5 | 98.6 | 4 | 15.7 |
| 2 | 152.4 | 19.1 | 120.7 | 4 | 19.1 |
| 2½ | 177.8 | 22.4 | 139.7 | 4 | 19.1 |
| 3 | 190.5 | 23.9 | 152.4 | 4 | 19.1 |
| 3½ | 215.9 | 23.9 | 177.8 | 8 | 19.1 |
| 4 | 228.6 | 23.9 | 190.5 | 8 | 19.1 |
| 5 | 254.0 | 23.9 | 215.9 | 8 | 22.4 |
| 6 | 279.4 | 25.4 | 241.3 | 8 | 22.4 |
| 8 | 342.9 | 28.4 | 298.5 | 8 | 22.4 |
| 10 | 406.4 | 30.2 | 362.0 | 12 | 25.4 |
| 12 | 482.6 | 31.8 | 431.8 | 12 | 25.4 |
| 14 | 533.4 | 35.1 | 476.3 | 12 | 28.4 |
| 16 | 596.9 | 36.6 | 539.8 | 16 | 28.4 |
| 18 | 635.0 | 39.6 | 577.9 | 16 | 31.8 |
| 20 | 698.5 | 42.9 | 635.0 | 20 | 31.8 |
| 22 | 749.3 | 46.0 | 692.2 | 20 | 35.1 |
| 24 | 812.8 | 47.8 | 749.3 | 20 | 35.1 |
The thickness values shown are basic minimum flange-body dimensions. Raised-face height, manufacturing tolerances and corrosion allowances may affect the flange’s measured overall thickness.
7. ANSI Class 300 and Class 600 Flange Dimensions Charts
Class 300 and Class 600 flanges are used where higher pressure-temperature capability is required. Compared with Class 150 flanges, they generally have thicker bodies, stronger bolting and different drilling patterns.
ANSI Class 300 flange dimensions
| NPS | Flange OD (in.) | Min. Thickness (in.) | Bolt Circle (in.) | No. of Holes | Hole Diameter (in.) |
|---|---|---|---|---|---|
| ½ | 3.75 | 0.56 | 2.62 | 4 | 0.62 |
| ¾ | 4.62 | 0.62 | 3.25 | 4 | 0.75 |
| 1 | 4.88 | 0.69 | 3.50 | 4 | 0.75 |
| 1¼ | 5.25 | 0.75 | 3.88 | 4 | 0.75 |
| 1½ | 6.12 | 0.81 | 4.50 | 4 | 0.88 |
| 2 | 6.50 | 0.88 | 5.00 | 8 | 0.75 |
| 2½ | 7.50 | 1.00 | 5.88 | 8 | 0.88 |
| 3 | 8.25 | 1.12 | 6.62 | 8 | 0.88 |
| 3½ | 9.00 | 1.19 | 7.25 | 8 | 0.88 |
| 4 | 10.00 | 1.25 | 7.88 | 8 | 0.88 |
| 5 | 11.00 | 1.38 | 9.25 | 8 | 0.88 |
| 6 | 12.50 | 1.44 | 10.62 | 12 | 0.88 |
| 8 | 15.00 | 1.62 | 13.00 | 12 | 1.00 |
| 10 | 17.50 | 1.88 | 15.25 | 16 | 1.12 |
| 12 | 20.50 | 2.00 | 17.75 | 16 | 1.25 |
| 14 | 23.00 | 2.12 | 20.25 | 20 | 1.25 |
| 16 | 25.50 | 2.25 | 22.50 | 20 | 1.38 |
| 18 | 28.00 | 2.38 | 24.75 | 24 | 1.38 |
| 20 | 30.50 | 2.50 | 27.00 | 24 | 1.38 |
| 22 | 33.00 | 2.62 | 29.25 | 24 | 1.62 |
| 24 | 36.00 | 2.75 | 32.00 | 24 | 1.62 |
An important example is the NPS 2 flange. A Class 150 flange uses four bolt holes on a 4.75-inch bolt circle, while a Class 300 flange uses eight bolt holes on a 5-inch bolt circle. The two classes are therefore not interchangeable.
ANSI Class 600 flange dimensions
| NPS | Flange OD (in.) | Min. Thickness (in.) | Bolt Circle (in.) | No. of Holes | Hole Diameter (in.) |
|---|---|---|---|---|---|
| ½ | 3.75 | 0.56 | 2.62 | 4 | 0.62 |
| ¾ | 4.62 | 0.62 | 3.25 | 4 | 0.75 |
| 1 | 4.88 | 0.69 | 3.50 | 4 | 0.75 |
| 1¼ | 5.25 | 0.81 | 3.88 | 4 | 0.75 |
| 1½ | 6.12 | 0.88 | 4.50 | 4 | 0.88 |
| 2 | 6.50 | 1.00 | 5.00 | 8 | 0.75 |
| 2½ | 7.50 | 1.12 | 5.88 | 8 | 0.88 |
| 3 | 8.25 | 1.25 | 6.62 | 8 | 0.88 |
| 3½ | 9.00 | 1.38 | 7.25 | 8 | 1.00 |
| 4 | 10.75 | 1.50 | 8.50 | 8 | 1.00 |
| 5 | 13.00 | 1.75 | 10.50 | 8 | 1.12 |
| 6 | 14.00 | 1.88 | 11.50 | 12 | 1.12 |
| 8 | 16.50 | 2.19 | 13.75 | 12 | 1.25 |
| 10 | 20.00 | 2.50 | 17.00 | 16 | 1.38 |
| 12 | 22.00 | 2.62 | 19.25 | 20 | 1.38 |
| 14 | 23.75 | 2.75 | 20.75 | 20 | 1.50 |
| 16 | 27.00 | 3.00 | 23.75 | 20 | 1.62 |
| 18 | 29.25 | 3.25 | 25.75 | 20 | 1.75 |
| 20 | 32.00 | 3.50 | 28.50 | 24 | 1.75 |
| 22 | 34.25 | 3.75 | 30.63 | 24 | 1.88 |
| 24 | 37.00 | 4.00 | 33.00 | 24 | 2.00 |
Class 300 versus Class 600
Some smaller Class 300 and Class 600 flanges share the same outside diameter and drilling pattern. This does not mean they have identical pressure ratings or that components may be substituted without engineering review.
Differences may exist in:
- Minimum flange thickness
- Hub dimensions
- Weld-end dimensions
- Bore dimensions
- Facing details
- Pressure-temperature ratings
- Required materials and bolting
Flange compatibility must therefore be verified using the complete designation rather than bolt alignment alone. At a minimum, the NPS, pressure class, standard, flange type, facing, material and pipe schedule should be confirmed before installation.
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Contents1 1. What Is an NPT Thread?1.1 Understanding National Pipe Taper Threads1.2 How NPT Threads Create a Seal1.3 NPT vs Straight Threads2 2. NPT Thread Standards and Specifications2.1 ASME B1.20.1 Standard2.2 Thread Form and Geometry2.3 NPT Thread Classes3 3. Complete NPT Thread Size Chart3.1 Standard NPT Thread Size Chart3.2 Large Diameter NPT Sizes3.3 Why Nominal […]
Contents1 1. What Is an NPT Thread?1.1 Definition of NPT1.2 Purpose of NPT Threads1.2.1 Mechanical Connection1.2.2 Fluid Sealing1.3 Common Industries Using NPT Threads2 2. NPT Thread Design and Geometry2.1 Tapered Thread Construction2.2 Thread Profile2.3 Male and Female Thread Components2.3.1 Male Thread (External Thread)2.3.2 Female Thread (Internal Thread)3 3. How NPT Threads Create a Seal3.1 Thread […]
Contents1 2 1. What Is a Hydraulic Pipe Size Chart?2.1 Why Hydraulic Pipe Sizing Matters2.2 Key Factors Used in Hydraulic Pipe Size Charts2.2.1 Flow Rate2.2.2 Operating Pressure2.2.3 Fluid Velocity2.2.4 Pipe Material2.3 Common Hydraulic Pipe Standards2.4 Hydraulic Pipe vs Hydraulic Tube3 2. Understanding Hydraulic Pipe Sizes3.1 Nominal Pipe Size (NPS)3.2 Outside Diameter (OD)3.3 Inside Diameter (ID)3.4 […]
Contents1 2 1. What Is BSP Thread?2.0.1 What BSP Means2.0.2 Main BSP Thread Types2.0.3 BSPP (British Standard Pipe Parallel)2.0.4 BSPT (British Standard Pipe Tapered)2.1 BSP Thread Standards2.1.1 ISO 72.1.2 ISO 2282.1.3 BS 212.1.4 Where BSP Threads Are Used2.1.5 Oil and Gas2.1.6 Hydraulics2.1.7 Pneumatics2.1.8 Water and Utility Systems2.1.9 Industrial Manufacturing3 2. What Is NPT Thread?3.1 Definition […]
Contents1 What Is a Hydraulic Pipe?1.1 Definition and Key Characteristics of Hydraulic Pipes1.2 How Hydraulic Pipes Are Manufactured1.3 Materials Commonly Used for Hydraulic Pipes1.4 Typical Applications of Hydraulic Pipes1.5 Pipe Size Standards Used in Hydraulic Pipes1.6 Pressure Capability of Hydraulic Pipes1.7 Connection Methods for Hydraulic Pipes1.8 Advantages of Using Hydraulic Pipes1.9 Limitations of Hydraulic Pipes2 […]