What is the difference between API 600 and API 602 gate valves?
API 600 covers cast steel gate, globe, and check valves — typically WCB/CF8M bodies from 2" upward, bolted bonnet, Class 150–2500#. API 602 covers forged steel gate, globe, and check valves — usually 4" and smaller (often ≤2"), socket weld or threaded ends, for high-integrity small-bore service.
API 600 vs API 602 Gate Valve
Cast Steel vs Forged Steel Gate Valves — Standards & Selection
API 600 and API 602 are both gate valve design standards, but they address different manufacturing methods, size ranges, and end connections. Confusing them leads to wrong specs on P&IDs and RFQs.
Head-to-Head Comparison
| Factor | API 600 (Cast) | API 602 (Forged) |
|---|---|---|
| Body manufacturing | Sand casting — WCB, WC6, CF8M | Forging — A105, F316, F11, F22 |
| Typical size range | 2" to 24"+ (large bore) | 1/4" to 4" (small bore) |
| End connections | Flanged RF/RTJ (ASME B16.5) | Socket weld, threaded, extended BW |
| Bonnet type | Bolted bonnet OS&Y (standard) | Bolted or welded bonnet, compact |
| Pressure classes | 150, 300, 600, 900, 1500, 2500 | 800, 1500, 2500, 4500 (SW/threaded) |
| Wall thickness | ASME B16.34 cast schedule | Thicker forged wall for small bore |
| Primary use | Mainline isolation, steam headers | Instrument, drain, vent, bypass lines |
| Testing | API 598 | API 598 |
Verdict
Specify API 600 for flanged cast steel gate valves on process and steam mains 2" and above. Specify API 602 for forged small-bore gate valves on drain, vent, instrument, and high-pressure socket-weld branches where compact forged bodies are required.
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Frequently Asked Questions
Can API 602 valves be flanged?
API 602 is primarily for socket weld and threaded ends. Flanged small-bore valves are sometimes supplied to API 602 design intent but API 600 is the standard for flanged cast gate valves.
Which is stronger — API 600 or API 602?
Both meet rigorous pressure-temperature ratings. API 602 forged bodies offer higher integrity in small bore and high-pressure SW service; API 600 cast valves scale to large diameters.
Is WCB an API 600 material?
Yes. ASTM A216 WCB is the most common body material for API 600 cast steel gate valves in steam and process service.
Do both require API 598 testing?
Yes. API 598 shell and seat hydrostatic testing applies to both API 600 and API 602 gate valves unless a project spec overrides with additional tests.