API Standards for Valves: The Complete Reference Guide
What Are API Standards?
The American Petroleum Institute (API) publishes standards that define design, manufacturing, testing, and documentation requirements for equipment in the petroleum and natural gas industries. API valve standards are recognized globally and often required by project specifications.
API Standards Quick Reference
| Standard | Valve Type | Scope | Typical Application |
|---|---|---|---|
| API 6D | Ball, gate, check, plug | Pipeline and piping service | Oil & gas pipelines, refineries |
| API 600 | Gate valve | Steel gate valves | Refinery hydrocarbon service |
| API 602 | Gate valve | Compact steel gate valves (DN <= 100) | Small bore, high pressure |
| API 608 | Ball valve | Metal ball valves | Petroleum refining |
| API 609 | Butterfly valve | Butterfly valves | General and petroleum service |
| API 594 | Check valve | Wafer and dual-plate check | Piping systems |
| API 607 | Fire-safe | Fire-safe test for quarter-turn | All quarter-turn valves |
| API 598 | Leakage testing | Valve inspection and testing | All valve types |
| API 520/521 | Relief valves | Sizing and selection | Overpressure protection |
API 6D: Pipeline and Piping Valves
Scope: Covers design, manufacturing, testing, and documentation for pipeline valves including ball, gate, check, and plug valves.
Key Requirements
- Materials: Must comply with ASME B16.34 or equivalent
- Face-to-face dimensions: Per ASME B16.10
- Flange dimensions: Per ASME B16.5 (NPS 1/2-24) or ASME B16.47 (NPS 26-60)
- Testing: 100% shell test, seat test per API 598
- Documentation: Material Test Reports (MTR), test certificates, traceability
API 6D Valve Types
- Through-conduit gate valves: Full bore, low pressure drop
- Ball valves: Trunnion-mounted for large bore (DN >= 100)
- Check valves: Swing, tilting disc, and dual-plate designs
- Plug valves: Lubricated and non-lubricated designs
API 600: Steel Gate Valves (Refinery Service)
Scope: Covers bolted bonnet steel gate valves for petroleum refinery and related applications.
Key Requirements
- Size range: NPS 2-24 (DN 50-600)
- Pressure classes: Class 150, 300, 600, 900, 1500, 2500
- Body-bonnet joint: Bolted bonnet design
- Trim: Standard trim includes 13% Cr stainless steel
- Testing: Per API 598
API 600 vs API 6D (Gate Valves)
| Feature | API 600 | API 6D |
|---|---|---|
| Application | Refinery service | Pipeline service |
| Design | Bolted bonnet | Varies (bolted, welded) |
| Size range | NPS 2-24 | NPS 2-48+ |
| Full bore | Required | Required |
| Through-conduit | Preferred | Required for some |
API 602: Compact Steel Gate Valves
Scope: Covers compact steel gate valves for small bore, high-pressure service.
Key Requirements
- Size range: NPS 1/2-2 (DN 15-50)
- Pressure classes: Class 150 to 2500
- Design: Compact body, reduced face-to-face dimensions
- End connections: Flanged, threaded, or welded
- Application: High-pressure instrument and sampling systems
API 607: Fire-Safe Testing
Scope: Defines fire test procedure for quarter-turn valves and valves equipped with non-metallic seats.
Test Procedure
- Valve is set in the open position
- Exposed to fire at 760-982°C (1400-1800°F) for 30 minutes
- External leakage measured during fire
- Internal leakage measured after fire (after cooldown)
Acceptance Criteria
- External leakage: Must not exceed specified limits during fire
- Internal leakage: Must not exceed specified limits after fire
- Valve operability: Must be operable after fire test
Fire-Safe Design Features
- Secondary metal-to-metal sealing behind soft seat
- Graphite body seals and packing
- Fire-safe stem sealing
- Anti-static device (spring between ball and stem)
API 598: Valve Inspection and Testing
Scope: Covers inspection, examination, and pressure testing requirements for valves.
Test Requirements
| Test Type | Medium | Duration | Acceptance |
|---|---|---|---|
| Shell (hydrostatic) | Water | Minimum 2 minutes | No visible leakage |
| Seat (liquid) | Water | Minimum 2 minutes | Per leakage class |
| Seat (gas) | Air/N2 | Minimum 2 minutes | Per leakage class |
| Backseat | Water | Minimum 2 minutes | No visible leakage |
Leakage Classes (API 598)
| Class | Test Medium | Allowable Leakage |
|---|---|---|
| Soft seat | Liquid | Zero visible leakage |
| Metal seat Class I | Liquid | 0.18 ml/min per inch of nominal size |
| Metal seat Class II | Gas | Bubbles per minute per inch |
| Metal seat Class III | Gas | Defined by manufacturer |
How to Verify API Compliance
1. Check the Nameplate
Every API-compliant valve must have a nameplate with:
- API standard number (e.g., API 6D)
- Size and pressure class
- Material grade
- Heat/lot number for traceability
- Manufacturer name and logo
2. Request Documentation
- Material Test Report (MTR): Chemical composition and mechanical properties
- Pressure Test Certificate: Shell and seat test results
- Certificate of Conformance: States compliance with specific API standard
3. Verify Traceability
- Heat numbers on body and bonnet must match MTR
- Material must match specification on data sheet
- Pressure class must meet or exceed design requirements
Find API-Compliant Valves
Use ValveSpecs Pro to filter valves by API standard compliance. Every valve in the database includes the applicable standards and certifications.
Frequently Asked Questions
What is the difference between API 6D and API 600 for gate valves?
API 6D covers pipeline service gate valves (including through-conduit design) for oil and gas pipelines. API 600 covers steel gate valves specifically for refinery hydrocarbon service with bolted bonnet design.
What does API 607 fire-safe testing involve?
API 607 tests quarter-turn valves by exposing them to a fire at 760-982°C for 30 minutes. It measures external leakage during the fire and internal leakage after cooldown. Fire-safe valves use secondary metal-to-metal sealing to maintain integrity after the soft seat is destroyed.
How do I verify that a valve is API compliant?
Check the valve nameplate for the API standard designation, request Material Test Reports (MTR) and pressure test certificates, verify heat number traceability, and confirm the pressure class meets your design requirements.
Is API 598 the same as ISO 5208?
No. API 598 is an American standard for valve inspection and testing. ISO 5208 is the international equivalent with more granular leakage rate classifications (Rate A through Rate R). ISO 5208 Rate A (zero visible leakage) is more stringent than API 598 soft seat requirements.