Valve Comparison Guide
ASME Class 300 vs Class 600: Pressure Rating Comparison for Valves
ASME Class 300 vs Class 600 pressure rating comparison: pressure-temperature tables, body materials (WCB vs LCC vs WC6), face-to-face dimensions, cost, and when to specify Class 600 valves.
Overview
ASME Class 300 is the second standard pressure class for industrial valves and flanges per ASME B16.34 and ASME B16.5. Class 300 WCB (carbon steel) valves are rated at 51.1 bar (740 psi) at 38°C (ambient) and 13.8 bar (200 psi) at 538°C. Class 300 is sufficient for the majority of general process plant, refinery, and pipeline applications where operating pressure is below 40–45 bar.
51.1 bar at 38°C (WCB) | 44.8 bar at 204°C | 27.6 bar at 427°C | ASME B16.34, ASME B16.5
ASME Class 600 is the third standard pressure class per ASME B16.34, rated at 102.1 bar (1480 psi) at 38°C for WCB carbon steel. Class 600 provides exactly double the pressure rating of Class 300 at ambient temperature. Class 600 is the entry point for high-pressure gas service, offshore wellhead, high-pressure steam, and refinery high-pressure units (hydrocracker, hydrotreater, catalytic reformer).
102.1 bar at 38°C (WCB) | 89.6 bar at 204°C | 55.1 bar at 427°C | ASME B16.34, ASME B16.5
Pros & Cons
ASME Class 300
ASME Class 600
ASME Class 300 vs ASME Class 600 — Specification Comparison
| Parameter | ASME Class 300 | ASME Class 600 |
|---|---|---|
| Max Pressure at 38°C (WCB) | 51.1 bar (740 psi) | 102.1 bar (1480 psi) — exactly double Class 300 |
| Max Pressure at 204°C (WCB) | 44.8 bar (650 psi) | 89.6 bar (1300 psi) |
| Max Pressure at 427°C (WCB) | 27.6 bar (400 psi) | 55.1 bar (800 psi) |
| LCC (Low Temp Carbon Steel) at 38°C | 51.1 bar | 102.1 bar |
| WC6 (1.25% Cr) at 538°C | 17.2 bar (250 psi) | 34.5 bar (500 psi) |
| Flange Standard | ASME B16.5 Class 300 RF or RTJ | ASME B16.5 Class 600 RF or RTJ |
| Face-to-Face (DN100 gate valve) | Shorter — per ASME B16.10 Class 300 | Longer — per ASME B16.10 Class 600 (heavier piping) |
| Body Wall Thickness | Thinner — lower pressure rating requirement | Thicker — higher pressure containment requirement |
| Relative Weight (DN100 gate valve) | ~100 kg (approximate reference) | ~165 kg (approximately 50–65% heavier) |
| Typical Applications | General process plant, refinery utility/atmospheric units, pipelines <50 bar | High-pressure gas, offshore wellhead, hydrocracker, HP steam, H2 service |
When to Use Each
Use ASME Class 300 when:
Use ASME Class 600 when:
Decision Guide
The selection between Class 300 and Class 600 is driven by the operating pressure and temperature of the specific service, read against the ASME B16.34 pressure-temperature table for the specified body material. As a practical guide: if the maximum allowable operating pressure (MAOP) of the pipeline or system is below 40 bar at ambient temperature, Class 150 or Class 300 is almost certainly sufficient. If the MAOP exceeds 50 bar, Class 600 becomes the appropriate class for carbon steel (WCB) at ambient temperature. For high-temperature service, always check the derated pressure at the operating temperature — a Class 300 WCB valve rated at 51.1 bar at 38°C is only rated at 27.6 bar at 427°C, which can easily be exceeded in steam service. Key decision triggers for Class 600: (1) operating pressure above 50 bar at any temperature; (2) high-pressure gas transmission offshore or onshore gas compression stations; (3) refinery high-pressure units (hydrotreater, hydrocracker, catalytic reformer); (4) high-pressure steam headers above 80–100 bar; (5) subsea wellhead manifolds; (6) high-pressure hydrogen service above 40 bar.
Frequently Asked Questions
What are all the ASME pressure classes for valves?
Can Class 300 and Class 600 valves be connected in the same pipeline?
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