ASME B31.8
Standard Specification

ASME B31.8 Plug Valves

What ASME B31.8 requires for plug valves — applicability, key and testing requirements, the alternative standards, and compliant supply with full certification.

What does ASME B31.8 require for plug valves?

ASME B31.8 (Gas Transmission and Distribution Piping Systems, American Society of Mechanical Engineers (ASME)) sets the design, material and testing requirements for plug valves in its scope. ASME B31.8 is the primary piping code for natural gas transmission and distribution systems - covering gas gathering, transmission pipelines, storage, LNG facilities, and distribution mains. It is the basis for US federal pipeline safety regulations (49 CFR Part 192) and is referenced by pipeline operators worldwide. All valves in ASME B31.8 systems must be rated for the operating pressure class and installed with accessible operators for emergency shutoff.

Applicable Pressure Classes

Class 150Class 300Class 600Class 900Class 1500

Key Requirements

  • Mainline block valves required at specific intervals depending on location class (urban vs. rural) - typically 7.5-mile maximum spacing in HCA Class 3/4 areas
  • Manual or automated (ESD) emergency shutoff valves (ESV) at pipeline sections, compressor stations, and high-consequence areas
  • Valve operators accessible within 15 minutes by emergency responders - remote or telemetry-operated ESVs recommended for HCA
  • Ball valves and gate valves must comply with API 6D (Class 150–2500) or ASME B16.34
  • Class 2 location (semi-urbanised areas) and Class 3/4 (urban/densely populated) require higher design factors and more frequent valve spacing
  • Pigging equipment (launcher/receiver) and mainline ball valves must accommodate in-line inspection (ILI) tool passage

Testing Requirements

  • Valve testing per API 598 or ISO 5208 required at manufacture
  • Field hydrostatic test of new pipeline: 1.25–1.5× MAOP depending on location class
  • Leak survey by walking or aerial survey required after commissioning

Alternative Standards for Plug Valves

Other standards that also govern plug valves — useful for spec cross-acceptance.

API 6DSpecification for Pipeline and Piping ValvesASME B16.34Valves - Flanged, Threaded, and Welding EndAPI 598Valve Inspection and TestingISO 15848Measurement, Test, and Qualification Procedures for Fugitive Emissions - Industrial ValvesBS 6755Testing of Valves - Production Pressure Testing and Fire Type Testing RequirementsAPI 6FASpecification for Fire Testing of ValvesISO 5208Industrial Valves - Pressure Testing of Metallic ValvesISO 10497Testing of Valves - Fire Type-Testing RequirementsASME B16.5Pipe Flanges and Flanged Fittings NPS 1/2 through NPS 24 Metric/Inch StandardAPI 6ASpecification for Wellhead and Christmas Tree Equipment
Reviewed by Valve Standards Engineering, Vajra Industrial SolutionsDiscipline: Industrial Valve Standards & ComplianceLast reviewed: 20 June 2026

Connected Engineering

Standards
API 6D
Products
Ball ValvesGate ValvesCheck ValvesPlug Valves
Comparisons
Gate vs Ball Valve
Tools
Pressure Class Converter

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Relevant Products
Vajra Plug Valves

Engineering references

ASME B31.8 full standardScope, requirements & documentationVajra Plug ValvesFull range, specs & standardsStandards Applicability MatrixWhich standard governs which type