Valve Standard Reference
BS 6755
BritishTesting of Valves — Production Pressure Testing and Fire Type Testing Requirements
BS 6755 is the British Standard for valve testing, covering production pressure testing (Part 1) and fire type testing (Part 2).
Overview — BS 6755
BS 6755 is the British Standard for valve testing, covering production pressure testing (Part 1) and fire type testing (Part 2). It is widely referenced in UK, Middle East, and Indian project specifications as an equivalent to ISO 5208 (production testing) and ISO 10497 / API 607 (fire testing). BS 6755 Part 1 defines leakage rate classes A through D, and is the most-cited valve leakage acceptance criterion in British-influenced project specifications.
Scope
BS 6755 Part 1 (Production Pressure Testing) applies to all industrial valve types and defines shell hydrostatic test, high-pressure seat test, and low-pressure seat test procedures with leakage rate acceptance classes A, B, C, and D. BS 6755 Part 2 (Fire Type Testing) covers fire endurance testing of valves — largely superseded by ISO 10497 and API 607 but still referenced in older British project specifications and some Middle East contracts.
Applicable Valve Types
Ball Valves
Gate Valves
Globe Valves
Butterfly Valves
Check Valves
Plug Valves
Needle Valves
Applicable Pressure Classes
Key Requirements — BS 6755
Part 1, Leakage Rate A: Zero leakage (bubble-tight) at test pressure — the tightest class, typically required for toxic, hazardous, or zero-leakage applications
Part 1, Leakage Rate B: Maximum 0.006 cm³/min per mm of nominal bore — applicable for gas and vapour service
Part 1, Leakage Rate C: Maximum 0.18 cm³/min per mm DN — for general liquid service
Part 1, Leakage Rate D: Maximum 1.8 cm³/min per mm DN — used for lower-criticality liquid isolation duties
Shell hydrostatic test: 1.5× rated pressure at 38°C for a minimum duration per valve size
High-pressure seat test: 1.1× rated pressure — checks seat sealing integrity under operating conditions
Low-pressure seat test (Part 1): 0.6 ± 0.1 bar (air test) — verifies seat seal at near-atmospheric pressure, critical for gas valves
Part 2 fire testing: valve must remain operable and maintain acceptable leak rate after 30-minute fire exposure at 750–1000°C
Testing Requirements — BS 6755
Shell hydrostatic test at 1.5× pressure rating (production test on every valve)
High-pressure closure test at 1.1× pressure rating
Low-pressure air seat test at 0.6 bar ± 0.1 bar
Duration per BS 6755 Table 1 (varies by valve size, NPS 1/2" through NPS 60")
Temperature: ambient (10–40°C) for production tests
Documentation Required for BS 6755 Compliance
BS 6755 Part 1 test certificate with leakage rate class (A, B, C, or D) stated
Material test reports (MTRs) per EN 10204 Type 3.1 or 3.2
Dimensional inspection report per BS 6755 and end-connection standard
Third-party witness test certificate (if required by specification)
BS 6755 Part 2 fire test certificate (if fire-safe valves specified)
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