Industrial Pressure Standards
ANSI, ISO, and Pressure Class Ratings
Learn the StandardsIndustrial equipment—valves, pipes, flanges, and vessels—must be rated for specific pressures to ensure safety and compatibility. Different standards organizations have developed pressure classification systems used worldwide. 理解する ANSI classes, ISO ratings, and industry-specific standards helps specify the right equipment for your application.
ASME/ANSI Pressure Classes
The American Society of Mechanical Engineers (ASME) defines pressure classes for flanges, fittings, and valves. These "Class" ratings indicate pressure-temperature capabilities.
| ANSI Class | Approx. PSI @ 100°F | Approx. Bar @ 38°C | Typical Use |
|---|---|---|---|
| Class 150 | 285 | 19.6 | Low pressure systems |
| Class 300 | 740 | 51.0 | Medium pressure |
| Class 600 | 1,480 | 102.0 | High pressure |
| Class 900 | 2,220 | 153.0 | Very high pressure |
| Class 1500 | 3,705 | 255.5 | Extra high pressure |
| Class 2500 | 6,170 | 425.5 | Maximum standard rating |
Note: Actual pressure ratings decrease at higher temperatures.
PN (Pressure Nominale) Ratings
European and ISO standards use PN ratings, indicating approximate pressure capacity in bar at 20°C.
| PN Rating | Pressure (bar) | Pressure (PSI) | Approx. ANSI Equivalent |
|---|---|---|---|
| PN 6 | 6 | 87 | — |
| PN 10 | 10 | 145 | — |
| PN 16 | 16 | 232 | Class 150 |
| PN 25 | 25 | 363 | Class 150-300 |
| PN 40 | 40 | 580 | Class 300 |
| PN 63 | 63 | 914 | Class 600 |
| PN 100 | 100 | 1,450 | Class 600 |
| PN 160 | 160 | 2,320 | Class 900 |
| PN 250 | 250 | 3,625 | Class 1500 |
| PN 400 | 400 | 5,800 | Class 2500 |
Pressure-Temperature Relationships
Pressure ratings are always specified at a reference temperature. As temperature increases, allowable pressure decreases due to material strength reduction.
ANSI Class 150 Example
| Temperature | Allowable Pressure (PSI) |
|---|---|
| -20°F to 100°F | 285 |
| 200°F | 260 |
| 300°F | 230 |
| 400°F | 200 |
| 500°F | 170 |
| 600°F | 140 |
Always consult manufacturer tables for exact ratings based on material and temperature.
Industry-Specific Standards
Oil and Gas (API)
- API 6A: Wellhead equipment (2K, 3K, 5K, 10K, 15K, 20K PSI)
- API 6D: Pipeline valves
- API 600/602/603: Steel valves
Chemical Processing
- ASME B31.3: Process piping
- ASME B16.5: Flanges and fittings
- ASME BPVC: Pressure vessels
Water/Wastewater
- AWWA: American Water Works Association standards
- Typically lower pressures (125-350 PSI)
Pressure Vessel Ratings
ASME Boiler and Pressure Vessel Code
Pressure vessels have design pressures and Maximum Allowable Working Pressure (MAWP):
- Design pressure: Pressure used for calculations
- MAWP: Maximum continuous operating pressure
- Test pressure: Typically 1.3-1.5× MAWP
- Relief valve setting: At or below MAWP
Common Vessel Pressure Ranges
| Vessel Type | Typical MAWP (PSI) |
|---|---|
| Air receivers | 150-300 |
| Process reactors | 150-3,000 |
| Heat exchangers | 150-600 |
| High-pressure autoclaves | 1,000-15,000 |
Selecting the Right Pressure Class
Factors to Consider
- Maximum operating pressure: Include surge/water hammer
- Operating temperature: Derate for high temperatures
- Fluid type: Corrosive fluids may require higher ratings
- Safety factor: Typically 3-4× operating pressure
- Code requirements: Industry regulations may mandate minimums
General Guidance
- Operating at <25% of rated pressure: May be over-specified
- Operating at >75% of rated pressure: Consider upgrading
- Always account for temperature derating
まとめ
Industrial pressure standards—ANSI classes, PN ratings, and API specifications—ensure equipment compatibility and safety. ANSI Class 150 through 2500 is standard in North America; PN 10 through PN 400 is used internationally. Pressure ratings always depend on temperature, and the weakest component determines system limits. Proper specification of pressure class is fundamental to safe industrial system design.