HomeValve ComparisonsAPI 600 vs API 602 Gate Valve: Flanged vs Compact for Refinery Service

Valve Comparison Guide

API 600 vs API 602 Gate Valve: Flanged vs Compact for Refinery Service

API 600 vs API 602 gate valve comparison: size range, bonnet type, end connections, body wall thickness, and selection guide for main process lines vs instrument bypasses in refinery and chemical service.

Overview

API 600 Gate Valve

API 600 (Steel Gate Valves — Flanged and Butt-Welding Ends, Bolted Bonnets) covers large, heavy-duty cast steel gate valves designed for general refinery and pipeline service. API 600 is the workhorse gate valve standard for main process lines, covering DN50 (2-inch) through DN900 (36-inch) in flanged and butt-weld ends.

DN50–DN900, Class 150–2500, WCB/WC6/WC9/CF8M, flanged RF/RTJ or BW ends, API 600 / ASME B16.34

API 602 Gate Valve

API 602 (Steel Gate, Globe, and Check Valves for Sizes DN100 and Smaller for the Petroleum and Natural Gas Industries) covers compact, forged or cast steel gate valves in DN15 through DN100 (1/2-inch through 4-inch) for auxiliary, instrument, drain, vent, and bypass service in refineries and chemical plants. API 602 valves are available in socket-weld, butt-weld, threaded, and flanged ends.

DN15–DN100, Class 800–2500 (SW/NPT) or Class 150–2500 (flanged), WCB/F316/F11/F22, SW/NPT/BW/flanged ends, API 602 / ASME B16.34

Pros & Cons

API 600 Gate Valve

Full-bore design providing zero pressure drop in the fully open position — ideal for pipeline mainline isolation
Flanged ends in Class 150 through Class 2500 per ASME B16.5 (or Class 300–2500 BW per ASME B16.25)
OS&Y (Outside Screw and Yoke) rising stem provides unambiguous visual open/closed position indication
Pressure-seal bonnet option available at Class 900 and above for high-pressure steam and hydrogen service
Available in full range of alloy steels: WCB, WC6, WC9, C5, C12, CF8, CF8M for all temperature ranges
Heavy body wall construction per API 600 minimum wall tables — designed for long service life in refinery process lines
Multi-turn operation (10–25 turns) — slow to open and close; not suitable for emergency shut-off
Large, heavy body — significant weight and installation space requirements for large bore sizes
Higher cost than API 602 at equivalent bore size due to heavier construction
Not available in socket-weld or threaded ends under API 600 — these are API 602 territory
Minimum size is typically DN50 (2-inch) — not manufactured for small instrument or auxiliary connections

API 602 Gate Valve

Compact and lightweight — forged steel body with reduced face-to-face vs API 600 bolted bonnet design
Available in socket-weld (SW), threaded (NPT/BSP), butt-weld (BW), and flanged ends — maximum installation flexibility for small-bore piping
Suitable for instrument root valves, chemical injection quills, vent and drain connections, bypass lines around larger valves
Pressure-seal bonnet option available at Class 1500 and 2500 for compact high-pressure applications
Lower cost than API 600 at equivalent bore size due to compact forged construction
Forged body provides superior material homogeneity vs cast body for small-bore, high-pressure applications
Maximum size DN100 (4-inch) — not available in larger sizes
Reduced-bore design common (ID smaller than nominal pipe bore) — minor pressure drop across the valve in the open position
Multi-turn operation (same as API 600) — not for quick isolation
Socket-weld and threaded ends not available in API 600 — there is no large-bore equivalent for small-bore needs
Less familiar to some maintenance teams than the dominant API 600 design

API 600 Gate Valve vs API 602 Gate Valve — Specification Comparison

ParameterAPI 600 Gate ValveAPI 602 Gate Valve
Governing StandardAPI 600 (flanged and BW, bolted bonnet)API 602 (DN100 and smaller, multiple end types)
Size RangeDN50–DN900 (2"–36")DN15–DN100 (1/2"–4")
End ConnectionsFlanged (RF, FF, RTJ) or butt-weld onlySocket-weld, NPT threaded, butt-weld, or flanged
Pressure Class RangeClass 150–2500 (flanged); Class 600–2500 (BW)Class 800–2500 (SW/NPT); Class 150–2500 (flanged)
Body ConstructionCast steel (WCB, WC6, WC9, CF8M)Forged steel (A105, F316, F11, F22) or small cast
Wall ThicknessHeavy — API 600 minimum wall tables per standardCompact — API 602 body dimension tables
Bonnet TypeBolted bonnet (standard); pressure-seal bonnet (Class 900+)Bolted bonnet or pressure-seal bonnet (Class 1500+)
WeightHeavy — significant for large bore sizesLight — compact forged construction
Typical ServiceMain process line isolation, pipeline block valvesInstrument root valves, drains, vents, bypass, auxiliary
CostHigher for small sizes (cast heavy construction)Lower for small sizes (forged compact construction)

When to Use Each

Use API 600 Gate Valve when:

Main process line isolation in refineries, petrochemical plants, and pipelines from DN50 to DN600+
High-pressure steam service (Class 600–2500) in power plants and utility steam systems
Crude oil and product pipeline block valves requiring full-bore, no-restriction flow paths
Infrequently operated isolations (fully open or fully closed, rarely throttled)
Flanged connections in Class 150 through Class 2500 process piping

Use API 602 Gate Valve when:

Instrument root valves and block valves on pressure gauges, thermowells, transmitters, and analysers
Bypass valves around control valves and larger isolation valves
Drain and vent valves on pressure vessels, heat exchangers, and piping low points
Chemical injection connection isolation valves
Small-bore auxiliary connections (DN15–DN50) in Class 800 through Class 2500 high-pressure service

Decision Guide

Choose API 600 when: (1) the pipeline or process line size is DN50 and above and flanged or butt-weld end connections are used; (2) the service is a main process line (crude, product, steam, gas) requiring a full-bore, heavy-duty gate valve designed for refinery service life; (3) API 600 is specifically listed in the applicable piping class (typically for nominal pipe size 2-inch and above in most refinery piping specifications). Choose API 602 when: (1) the valve size is DN50 and below (1/2-inch through 2-inch), where the compact API 602 forged body is the standard and API 600 is not practical; (2) the end connection is socket-weld or threaded — these are not available under API 600 and are the domain of API 602; (3) the service is auxiliary — instrument root valve, bypass, drain, vent, chemical injection isolation — regardless of pressure class. Many refinery piping specifications draw the boundary at 2-inch (DN50): DN50 and below uses API 602; DN50 and above uses API 600 (with some companies specifying API 600 from DN65 and above). The two standards are complementary, not competing — a well-designed plant uses both.

Frequently Asked Questions

What pressure class are API 602 socket-weld gate valves?
API 602 socket-weld and threaded gate valves are typically manufactured in Class 800 and Class 1500 (using ASME B16.11 socket-weld or threaded fittings pressure ratings — these are not ASME flange classes but an equivalent pressure designation). Class 800 SW gate valves are the standard for DN15–DN50 instrument and utility service in Class 150 and Class 300 flanged piping systems — the SW Class 800 valve is compatible with Class 300 flange pressure-temperature ratings for most services. Class 1500 SW gate valves are used for higher-pressure applications, and Class 2500 forged gate valves are available for very high-pressure hydrogen, steam, and chemical service. For flanged API 602 gate valves, the standard ASME B16.5 flange classes apply (Class 150 through Class 2500), exactly as for API 600.

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