Valve Standard Reference
ASME B31.1
AmericanPower Piping
ASME B31.
Overview — ASME B31.1
ASME B31.1 is the power piping code governing the design, material selection, fabrication, installation, inspection, examination, and testing of piping systems in electric power generating stations, industrial and institutional plants, geothermal heating systems, and central and district heating and cooling systems. It covers the most demanding steam service conditions — high-pressure, high-temperature boiler external piping, main steam lines, reheat lines, and feedwater piping — where valve failure can be catastrophic. All valves installed in B31.1 scope systems must meet the code's strict material, pressure class, and documentation requirements.
Scope
Covers all piping external to boilers as defined in ASME Section I, plus all other power plant piping: steam (up to supercritical conditions), condensate, feedwater, drain, vent, instrument, and service piping. Particularly critical for main steam (Class 1 piping), hot reheat, and cold reheat lines. Boiler external piping must comply with both B31.1 and ASME Section I.
Applicable Valve Types
Gate Valves — main steam and feedwater isolation
Globe Valves — throttling in steam and feedwater service
Check Valves — feedwater and condensate return
Ball Valves — auxiliary steam and drain service
Applicable Pressure Classes
Key Requirements — ASME B31.1
Valve design must comply with ASME B16.34 pressure-temperature ratings for the service class
High-pressure steam valves: typically Class 1500 or Class 2500, Cr-Mo alloy steel body (WC6/WC9/P91)
Minimum wall thickness of pressure-containing components per B31.1 formula
Bolting: high-temperature alloy steel fasteners (ASTM A193 B7, A194 2H) for steam service
Welding procedures and welder qualifications per ASME Section IX
Post-weld heat treatment (PWHT) mandatory for alloy steel welds
Examination requirements escalate with pressure class: visual, radiographic, or ultrasonic per class
Valve stem packing must be rated for the maximum operating temperature and pressure
Testing Requirements — ASME B31.1
Hydrostatic test of each valve per ASME B16.34 / API 598 before installation
System hydrostatic or pneumatic test after installation per B31.1 test requirements
NDE examination of welds (RT or UT) for Class 1 and critical piping
Documentation Required for ASME B31.1 Compliance
ASME B16.34 compliance marking on valve body
Material Test Reports (MTR) per EN 10204 3.1 for alloy steel bodies
Weld procedure specifications (WPS) and procedure qualification records (PQR) per ASME Section IX
PWHT records for alloy steel valves and weld-end installations
Pressure test certificate
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