API 600 Explained — Cast Steel Gate Valve Design, Materials & Testing Requirements

API 600 is the industry’s primary specification for bolted bonnet cast steel gate valves used in petroleum refinery, petrochemical, and oil and gas processing service. For engineers specifying isolation valves in high-temperature, high-pressure hydrocarbon service, procurement professionals reviewing vendor documentation packages, or quality inspectors verifying factory acceptance test compliance, API 600 defines the technical baseline that governs design integrity, material performance, dimensional requirements, and testing verification from NPS ½ through NPS 24. This page provides a structured, engineering-level breakdown of API 600 — covering its scope, design and material requirements, mandatory testing, its relationship with complementary standards, and practical guidance for procurement and engineering review.

For a complete overview of all key valve standards used across industrial applications, visit our Valve Standards pillar page.

What Is the API 600 Standard?

API 600 Standard Overview

API 600 — formally titled Bolted Bonnet Steel Gate Valves for Petroleum and Natural Gas Industries — is published by the American Petroleum Institute (API) and establishes minimum requirements for the design, material selection, manufacturing, testing, and marking of bolted bonnet steel gate valves intended for use in petroleum refinery and related process industries. The standard is one of the most widely referenced valve specifications in the global oil, gas, and petrochemical sector and serves as the default gate valve specification on the vast majority of refinery and petrochemical plant projects worldwide.

API 600 covers the full range of design and qualification requirements that a cast steel gate valve must meet before it can be legitimately offered and accepted as an API 600 — compliant product. These requirements span body and bonnet geometry, wall thickness, stem design and blowout prevention, packing arrangements, end connections, dimensional interchangeability, pressure-temperature ratings, material specifications, and mandatory factory pressure testing. Valves manufactured and tested in accordance with API 600 may additionally carry the API Monogram — a voluntary licensing mark administered by API that indicates the manufacturing facility has been independently audited against API quality requirements.

Scope of API 600

Valve Types and Size Range

API 600 applies specifically to bolted bonnet gate valves with cast steel bodies, in sizes from NPS ½ through NPS 24, across pressure classes 150, 300, 600, 900, 1500, and 2500. The standard covers both full-bore (full-port) and reduced-bore designs, with flanged end connections (raised face or ring type joint) and butt-welding ends as the primary connection types addressed. Both outside screw and yoke (OS&Y) and inside screw rising stem designs are covered, though OS&Y construction is by far the most common configuration for refinery and process plant applications.

API 600 does not cover non-metallic or lined gate valves, cryogenic extension bonnet designs beyond the standard’s scope, or compact forged steel gate valves — which are separately governed by API 602. For pipeline gate valves in oil and gas transmission service, the applicable standard is API 6D rather than API 600 — a distinction that engineers must clearly establish when developing valve specifications to avoid applying the wrong design standard to the application.