API 603

Covers — corrosion-resistant, bolted-bonnet gate valves with flanged and butt-welding ends, in austenitic stainless and other corrosion-resistant alloys, with thinner wall sections than API 600.

Does NOT cover (exclusions) — the following are governed elsewhere:

• Heavy-duty carbon/low-alloy steel gate valves → API 600.
• Compact / small-bore forged valves → API 602.
• Ratings basis → ASME B16.34; testing → API 598.

Choose API 603 when the corrosion resistance of the alloy — not a heavy wall — governs the design.

API 603 sets minimum requirements for corrosion-resistant gate valves:

• Materials — austenitic stainless and corrosion-resistant alloy body/bonnet with compatible trim.
• Design — bolted bonnet with thinner (lighter) wall than API 600, sized to the B16.34 rating.
• Examination & Testing — shell and seat testing per API 598.

API 603 provides corrosion-resistant bolted-bonnet gate valves in stainless and alloy construction with lighter walls than API 600. It suits chemical and corrosive process service where the alloy handles corrosion and a heavy carbon-steel wall would be unnecessary.

Rating and testing follow ASME B16.34 and API 598, exactly as for API 600 — the distinction is the corrosion-resistant, thinner-wall design.

Engineering Note: Confirm the alloy is compatible with the specific corrosive medium (e.g., chloride stress-corrosion cracking risk on austenitic stainless) before selecting API 603.