What are Pressure Ratings?
Pressure ratings refer to the maximum working pressure that components (such as flanges, fittings, valves, etc.) used in a piping system can withstand under specific conditions.
These pressure ratings are typically closely related to temperature and the properties of the materials, ensuring that the piping system can operate safely under varying conditions.
Influencing Factors
Temperature: At higher temperatures, the strength of materials generally decreases, which means pressure ratings tend to be lower at elevated temperatures.
Material Type: Different materials have different resistance to pressure. High-strength alloys typically have higher pressure ratings compared to standard carbon steel.
Pressure ratings are an important basis for the design and selection of piping system components, ensuring that they can safely operate within specific working pressures and temperatures. Exceeding these pressure ratings could lead to equipment failure or leakage, posing safety risks.
Pressure Ratings for Common Flange Materials at 100°C and 200°C
The pressure ratings for the materials you mentioned at 100°C (150# flange rating) depend on their mechanical properties, temperature, and design code (such as ASME B16.5). Below is an approximation of the pressure ratings for these materials,
| Material | Pressure Rating (at 100°C) | Pressure Rating (at 200°C) | Application |
| A105 (Carbon Steel) | 285 psi | 270 psi | General-purpose, low to medium pressure |
| A182 Gr. F304 (Stainless Steel) | 740 psi | 725 psi | Corrosive environments, high temperature service |
| A182 Gr. F51 (Duplex Stainless Steel) | 740 psi | 725 psi | High strength, stress corrosion resistance in aggressive environments |
| B564 Gr. N04400 (Monel 400) | 740 psi | 725 psi | Marine, chemical processing, high corrosion resistance |
Key Factors in Material Selection
| Table 2-1.1 Pressure-Temperature Ratings for Group 1.1 Materials | |||||||
| Nominal Designation | Forgings | Castings | Plates | ||||
| C-Si | A105 (1) | A216 Gr.WCB(1) | A515 Gr.70(1) | ||||
| C-Mn-Si | A350 Gr. LF2 (1) | … | A516 Gr.70(1),(2) | ||||
| C-Mn-Si | … | … | A537 Cl.1 (3) | ||||
| C-Mn-Si-V | A350 Gr. LF6 Cl. 1 (4) | … | … | ||||
| 3/₂Ni | A350 Gr. LF3 (5) | … | … | ||||
| Temp.,℃ | Working Pressures by Classes,bar | ||||||
| Class | |||||||
| 150 | 300 | 400 | 600 | 900 | 1500 | 2500 | |
| -29 to 38 | 19.6 | 51.1 | 68.1 | 102.1 | 153.2 | 255.3 | 425.5 |
| 50 | 19.2 | 50.1 | 66.8 | 100.2 | 150.4 | 250.6 | 417.7 |
| 100 | 17.7 | 46.6 | 62.1 | 93.2 | 139.8 | 233.0 | 388.3 |
| 150 | 15.8 | 45.1 | 60.1 | 90.2 | 135.2 | 225.4 | 375.6 |
| 200 | 13.8 | 43.8 | 58.4 | 87.6 | 131.4 | 219.0 | 365.0 |
| 250 | 12.1 | 41.9 | 55.9 | 83.9 | 125.8 | 209.7 | 349.5 |
| 300 | 10.2 | 39.8 | 53.1 | 79.6 | 119.5 | 199.1 | 331.8 |
| 325 | 9.3 | 38.7 | 51.6 | 77.4 | 116.1 | 193.6 | 322.6 |
| 350 | 8.4 | 37.6 | 50.1 | 75.1 | 112.7 | 187.8 | 313.0 |
| 375 | 7.4 | 36.4 | 48.5 | 72.7 | 109.1 | 181.8 | 303.1 |
| 400 | 6.5 | 34.7 | 46.3 | 69.4 | 104.2 | 173.6 | 289.3 |
| 425 | 5.5 | 28.8 | 38.4 | 57.5 | 86.3 | 143.8 | 239.7 |
| 450 | 4.6 | 23.0 | 30.7 | 46.0 | 69.0 | 115.0 | 191.7 |
| 475 | 3.7 | 17.4 | 23.2 | 34.9 | 52.3 | 87.2 | 145.3 |
| 500 | 2.8 | 11.8 | 15.7 | 23.5 | 35.3 | 58.8 | 97.9 |
| 538 | 1.4 | 5.9 | 7.9 | 11.8 | 17.7 | 29.5 | 49.2 |
NOTES:
(1) Prolonged use above 425°C is permissible but not recommended. Prolonged exposure above 425°C may cause the carbide phase of steel to convert to graphite.
(2) Not to be used over 455°C.
(3) Not to be used over 370°C.
(4) Not to be used over 260°C.
(5) Not to be used over 345°C.
