API 600 vs API 602

API 600 covers cast steel gate valves with flanged, butt-welding, and pressure-seal ends for sizes 2” and above. API 602 covers compact forged steel gate, globe, and check valves for sizes typically below 2” (up to 4” in some classes). The choice between them is primarily determined by valve size and manufacturing method.

When to Use Each Standard

API 600 applies to valves with cast bodies: manufactured by pouring molten steel into a mold. Casting allows complex shapes and large sizes but requires radiographic or ultrasonic inspection to detect internal porosity and inclusions.

API 602 applies to valves with forged bodies: manufactured by shaping solid steel billets under heat and pressure. Forging produces a denser, stronger microstructure with fewer defects. Forged valves are standard for small-bore, high-pressure, and critical applications.

Comparison Table

Parameter	API 600	API 602
Scope	Cast steel gate valves	Compact forged steel gate, globe, check valves
Body manufacturing	Cast (investment or sand casting)	Forged (from billet)
Size range	2” and above (up to 60”+)	1/4” to 4” (typically up to 2”)
Pressure classes	150, 300, 600, 900, 1500, 2500	150, 300, 600, 800, 1500, 2500
End connections	Flanged, butt-weld, pressure-seal	Threaded (NPT), socket weld, butt-weld, flanged
Valve types	Gate only	Gate, globe, check
Body materials	A216 WCB, WCC, A217 WC6/WC9, A351 CF8M	A105, A182 F11/F22/F304/F316/F51
Wall thickness	Thinner (cast structure acceptable for larger valves)	Thicker relative to bore (forged, compact design)
Microstructure	Cast grain (may have porosity)	Forged grain (dense, uniform)
Inspection	RT or UT per ASME B16.34	VT, MT/PT per ASME B16.34
Trim numbers	Standardized (Trim 1, 5, 8, 12)	Referenced from API 600/602
British equivalent	BS 1414	BS 5352

Class 800: Unique to API 602

API 602 includes Class 800, a pressure class that does not exist in API 600 or ASME B16.34. Class 800 is a socket weld or threaded end forged valve rated for pressures between Class 600 and Class 1500. The rating is based on the valve body wall thickness and is independent of the flange class system. Class 800 forged gate, globe, and check valves are the standard small-bore isolation valves in refineries and petrochemical plants.

Size Overlap (2” to 4”)

Between 2” and 4”, both API 600 (cast) and API 602 (forged) valves are available. The decision depends on end connection and pressure class:

Connection	2” to 4”	Recommendation
Flanged RF	API 600 (cast) is standard	Cast body, flanged ends per B16.5
Socket weld	API 602 (forged)	Forged body, compact design
Threaded NPT	API 602 (forged)	Forged body
Butt-weld	Either	Forged preferred for high-integrity service

Pro Tip

For Class 800 socket weld and threaded valves, always specify “API 602” explicitly on the datasheet. Some manufacturers supply generic forged valves that do not meet API 602 testing and documentation requirements. API 602 compliance ensures proper body wall thickness, trim quality, and pressure testing.

Both API 600 and API 602 valves reference ASME B16.34 for pressure-temperature ratings and are specified in piping material specifications.

Read the full guide to valve types