Class 600 Flange Pressure Rating Chart
The Class 600 flange pressure rating represents the third-highest standard pressure class in the ASME B16.5 system, positioned between Class 400 and Class 900. At ambient temperature, a Class 600 ASTM A105 carbon steel flange is rated for 1,480 psig (102.0 barg)—suitable for high-pressure hydrocarbon service, steam systems, and critical process applications. This article provides the complete Class 600 pressure rating chart and explains when to specify this class.
Class 600 Pressure Rating Chart
| Temperature | A105 (Group 1.1) | A182 F304 (Group 2.1) | A182 F316 (Group 2.3) | A182 F11 (Group 1.9) |
|---|---|---|---|---|
| -20 to 100°F (-29 to 38°C) | 1,480 psig | 1,440 psig | 1,440 psig | 1,500 psig |
| 200°F (93°C) | 1,350 psig | 1,235 psig | 1,240 psig | 1,500 psig |
| 300°F (149°C) | 1,315 psig | 1,130 psig | 1,160 psig | 1,455 psig |
| 400°F (204°C) | 1,270 psig | 1,020 psig | 1,060 psig | 1,440 psig |
| 500°F (260°C) | 1,200 psig | 930 psig | 1,010 psig | 1,410 psig |
| 600°F (316°C) | 1,095 psig | 860 psig | 960 psig | 1,370 psig |
| 700°F (371°C) | 1,065 psig | 800 psig | 910 psig | 1,340 psig |
| 750°F (399°C) | 1,010 psig | 770 psig | 880 psig | 1,320 psig |
| 800°F (427°C) | 825 psig | 730 psig | 860 psig | 1,300 psig |
| 900°F (482°C) | 535 psig | 670 psig | 790 psig | 1,160 psig |
| 1,000°F (538°C) | 340 psig | 620 psig | 690 psig | 900 psig |
Values from ASME B16.5-2020. Linear interpolation is permitted for intermediate temperatures.
Key Points
Typical applications: Class 600 flanges are used for high-pressure steam (above 600 psig), high-pressure hydrocarbon processing (catalytic reforming, hydrotreating), subsea wellhead connections (in combination with API standards), and high-pressure gas transmission pipelines.
Comparison with adjacent classes: At ambient temperature, Class 600 provides exactly twice the pressure capacity of Class 300 (1,480 vs. 740 psig). At elevated temperatures, the ratio changes slightly due to different derating slopes. Class 600 is often specified where Class 300 is insufficient but Class 900 would be oversized.
Material selection impact: At 900°F, an A105 Class 600 flange drops to 535 psig, while an F11 alloy steel Class 600 flange retains 1,160 psig—more than double the carbon steel capacity. For high-temperature applications above 800°F, alloy steel materials provide significantly better pressure retention.
Class 600 Flange Dimensions (NPS 6 Weld Neck)
| Parameter | Class 600 Value |
|---|---|
| Outside diameter | 355.6 mm (14.00 in) |
| Thickness | 47.8 mm (1.88 in) |
| Bolt circle | 317.5 mm (12.50 in) |
| Number of bolts | 12 |
| Bolt size | 7/8 in |
| Approximate weight | 27 kg (60 lb) |
| Raised face height | 6.4 mm (0.25 in) |
Dimensions per ASME B16.5.
For detailed flange dimension tables and the full ASME B16.5 PT rating data for all pressure classes, see the flange rating guide.
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