Gate valves are specified against three different API standards, and choosing the wrong one is one of the most common mistakes in valve procurement. The confusion is understandable: the documents carry similar titles and overlapping vocabulary. But their scopes do not overlap — each covers a distinct family of valves, and a specification that cites the wrong standard creates rework at the vendor stage.
API 600 is the specification for bolted-bonnet steel gate valves for petroleum and natural gas industries, covering flanged and butt-welding ends in pressure classes from 150 through 2500. It is the default standard for large-bore gate valves in refinery and petrochemical service, and it defines face-to-face dimensions, wall thickness, stem requirements and bonnet designs.
Contrary to a common misconception, API 600 covers gate valves only. It is not a combined gate-globe-check document. If your line calls for a steel globe valve, the governing document is API 623 (bolted-bonnet steel globe valves), not API 600.
API 602 is the one that covers all three functions — gate, globe and check — but only for compact, small-bore valves: NPS 4 and smaller, in Class 150 through 2500. These forged-body valves dominate instrument, drain, sample and bypass lines. Because the same document governs all three functions, engineers sometimes project that logic onto API 600. It does not carry over: API 600 is gate-only.
API 603 covers Class 150 bolted-bonnet gate valves in corrosion-resistant materials — typically austenitic stainless steels — for services where carbon steel would corrode. Scope is narrower than API 600: lighter pressure classes and a materials focus. When the service is acidic, chlorinated or otherwise corrosive at moderate pressure, API 603 is usually the correct citation.
Standards citations drive vendor quotations, testing scope and delivery times. An API 600 valve built to refinery wall thickness costs more and weighs more than an API 603 equivalent at Class 150. Conversely, asking a forged-valor shop to certify an API 600 valve that is actually an API 602 product wastes weeks. Before issuing an inquiry, confirm the valve function, bore size, pressure class and corrosivity of the media — then cite the standard whose scope matches all four.