Class 300 vs Class 600 — Stepping Up ASME Valve Class
Class 300 is common for elevated process pressure versus Class 150. Class 600 is selected when Class 300 P-T limits are exceeded. Flanges, bolting, and valve mass increase.
Quick selection
Stay on Class 300 when design P/T fits. Move to Class 600 when tables demand it. Related: Class 150 vs 300.
Comparison table
| Factor | Class 300 | Class 600 |
|---|---|---|
| Relative capacity | Mid process class | Higher pressure class |
| Flanges | Heavier than 150 | Heavier than 300; often RTJ on high P |
| Typical RFQs | Hydrocarbons, steam auxiliaries | Higher P process / pipeline |
| Testing | API 598 (or project std) | API 598 / API 6D as specified |
| Buyer action | State Class 300 + facing | State Class 600 + RF/RTJ + MOC |
Facing and ends
Raised face is common; RTJ appears more often as pressure rises.
- Do not mix Class 300 valves with Class 600 flanges casually.
- Forged small-bore may use Class 800 (API 602) — different product line.
RFQ wording that works
- “WCB gate, Class 300, RF flanged, API 600, API 598 tested, size __.”
- Or: “Class 600 ball / gate, RTJ, CF8M, with MTC 3.1.”
FAQ
Is Class 600 always twice Class 300 pressure?
Not as a simple rule. Use ASME B16.34 P-T tables.
Do I need Class 600 for steam?
Depends on design P/T.
API 6D and Class 600?
Pipeline valves may be API 6D at Class 600 — cite both.
Class 600 vs PN100?
Different systems. Correlate via piping class.
Related RFQs and hubs
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