Valve Standard Reference
ASME B31.8
AmericanGas Transmission and Distribution Piping Systems
ASME B31.
What is ASME B31.8?
ASME B31.8 (Gas Transmission and Distribution Piping Systems) is an industrial valve standard issued by American Society of Mechanical Engineers (ASME). Applies to gas transmission lines (high-pressure, typically Class 600–900), gas distribution mains (Class 150–300), compressor station piping, gas storage fields, and LNG satellite facilities.
- Issuing Body:
- American Society of Mechanical Engineers (ASME)
- Category:
- installation
Overview - ASME B31.8
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.
Scope
Applies to gas transmission lines (high-pressure, typically Class 600–900), gas distribution mains (Class 150–300), compressor station piping, gas storage fields, and LNG satellite facilities. Covers metallic and plastic piping in gas service from wellhead to customer meter set.
Vajra Industrial Solutions manufactures and supplies valves engineered to comply with ASME B31.8, each delivered with EN 10204 3.1 MTCs for body, bonnet, stem, and pressure-containing parts and API 598 or ISO 5208 pressure test certificate as standard.
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Applicable Valve Types
Ball Valves - full-bore API 6D for mainline, actuated ESV
Gate Valves - API 6D, rising stem for above-ground installations
Check Valves - API 6D swing check for compressor station discharge
Plug Valves - lubricated and non-lubricated for distribution systems
Applicable Pressure Classes
Key Requirements - ASME B31.8
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 - ASME B31.8
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
Documentation Required for ASME B31.8 Compliance
EN 10204 3.1 MTCs for body, bonnet, stem, and pressure-containing parts
API 598 or ISO 5208 pressure test certificate
Certificate of conformance to API 6D or ASME B16.34
Actuator torque certification (if motorised or pneumatic ESD valve)
Related Standards
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