An Overview of API Standard 600
Steel Gate Valves—Flanged and Butt-welding Ends, Bolted Bonnets

API 600 standard for Bolted Bonnet Steel Gate Valves for Petroleum and Natural Gas Industries is a standard developed by the American Petroleum Institute (API). It specifies the requirements for the design, materials, manufacturing, testing, and inspection of bolted bonnet steel gate valves used in the petroleum and natural gas industries.

Industries Using API 600 Valves:

• Oil & Gas (upstream, midstream, downstream)
• Refineries
• Petrochemical plants
• Power generation
• LNG (liquefied natural gas) facilities

Key Features of API 600:

1. Valve Type: Covers bolted bonnet steel gate valves (rising stem or non-rising stem).
2. Pressure-Temperature Ratings: Follows ASME B16.34 (pressure classes: 150, 300, 400, 600, 900, 1500, 2500).
3. End Connections: Flanged, butt-weld, socket-weld, or threaded.
4. Materials: Specifies body, bonnet, trim, and sealing materials (carbon steel, stainless steel, alloy steel, etc.).
5. Design Requirements:
   • Pressure sealing (optional for high-pressure classes)
   • Stem design (anti-blowout feature)
   • Fire-safe design (API 607/API 6FA compliance if required)
   • Extended bonnet for cryogenic or high-temperature applications
6. Testing: Hydrostatic shell test, seat leakage test (API 598 standards)
7. Marking & Documentation: Requires proper identification and certification.

Scope & Applicability

• Valve Types: Rising stem (OS&Y) & non-rising stem gate valves.
• Size Range: Typically NPS 2 to 24 (DN 50 to 600).
• Pressure Classes: 150, 300, 400, 600, 900, 1500, 2500 (ASME B16.34).
• Temperature Range: -29°C to 538°C (-20°F to 1000°F) and beyond (with special materials).

How API 600 is Used?

1. Valve Selection: Helps engineers choose gate valves that meet stringent industry requirements for oil, gas, and petrochemical applications.
2. Manufacturing Compliance: Ensures valves are built to withstand high pressures, corrosive environments, and extreme temperatures.
3. Quality Assurance: Mandates testing and inspection protocols to ensure reliability and safety.
4. Procurement & Contracts: Often referenced in project specifications to ensure compliance with industry standards.
5. Interoperability: Ensures compatibility with other API/ASME standards (e.g., ASME B16.34, API 598).

Important Sections and Considerations in API 600:

Section 1 – Scope and Definitions:

• Clearly states that the API 600 specification applies to steel gate valves used in the oil and gas industry and the various pressure classes and sizes that fall within the scope.

Section 2 – Design and Materials:

• Defines the valve design, including stem and gate types, as well as material grades and specifications.
• Discusses the types of gate valves (wedge, flexible, etc.) and the materials used for sealing and body components.

Section 3 – Dimensions and Testing:

• Covers face-to-face dimensions for different valve sizes and pressure classes.
• Specifies testing procedures for ensuring the valve’s integrity and performance.

Section 4 – Quality Control and Inspection:

• Sets the standards for visual and mechanical inspections, including mandatory checks for dimensional accuracy and material compliance.

Related Standards:

• API 602: Compact steel gate valves (smaller sizes)
• API 603: Corrosion-resistant gate valves
• API 598: Valve testing standards
• ASME B16.34: Pressure-temperature ratings

API 600 ensures durability, safety, and performance in critical applications, making it a key standard for gate valves in the energy sector

Example: Selecting a Gate Valve for High-Temperature Steam Service

Here’s a specific, practical example of how the API 600 standard is used in the oil and gas industry, with a focus on valve selection and compliance:

Example: Selecting a Gate Valve for High-Temperature Steam Service in a Process Plant
A refinery needs a bolted bonnet steel gate valve for a steam line operating at 400°C (750°F) and 600 psi.

Step-by-Step API 600 Application

Step 1: Define Service Conditions First

2. Valve Type Selection

• Service: Steam (high temperature, high pressure)
• Valve Type: Gate valve — suitable for isolation (on/off) service
• Bonnet Type: Bolted bonnet — preferred for high-temperature/high-pressure to allow for maintenance

API 600 Requirement:

• Standard covers bolted bonnet steel gate valves (Section 1).
• Must be rising stem, wedge-type for tight shutoff.

3. Valve Material Selection

Material must withstand steam, temperature (400°C), and pressure.
Common API 600 materials:

• WCB (carbon steel) – Disqualified (400°C is acceptable but marginal for steam). Not good above ~425°C.
• WC6 (1.25Cr-0.5Mo alloy steel) — good up to ~600°C.
• WC9 (2.25Cr-1Mo alloy steel) — even better.

ASTM A217 Grade WC6 or WC9 steel body both are suitable for high-temp steam

4. Trim Selection

Service Condition: High-temperature steam (erosive).
Use API 600 Table 8 (Trim Materials):

Trim 5 (9Cr-1Mo) recommended because Matches body temperature capability, it is hard-faced Stellite seat and disc which is very good for steam.

• Seat/Disc: ASTM A217 C12 (9Cr-1Mo)
• Stem: A182 F6a (13% Cr steel)
• Hardness: 22–30 HRC (to prevent galling)

5. Pressure-Temperature Rating

Use ASME B16.34 referenced in API 600.

Key Points:

• ASME B16.34 gives pressure-temperature ratings for valve body materials.
• Ratings are based on material group (carbon steel, low alloy steel, stainless steel, etc.).
• Pressure ratings decrease as temperature increases.
• Ratings are organized by Pressure Classes (150, 300, 600, 900, etc.).

Using ASME B16.34 (referenced in API 600 Table 1):

For WC6 (1.25Cr-0.5Mo) material:

• At 400°C: MAWP = 1,550 psi (well above 600 psi requirement)
• At 550°C: MAWP drops to 1,150 psi (still safe)

Verification Against Actual Design