Overview
EN ISO 11363-1:2018 (ISO 11363‑1:2018) specifies the geometric dimensions and tolerances for two taper screw threads used to connect valves to gas cylinders: nominal diameters 17,4 mm (17E) and 25,8 mm (25E). Published by CEN as an adoption of the ISO text, this standard defines thread geometry, reference planes and nomenclature for valve stems and cylinder neck threads - but does not address mechanical strength, gas tightness, or repeated assembly performance.
Key topics and technical requirements
- Thread sizes: Nominal diameters 17E (17.4 mm) and 25E (25.8 mm) for valve-to-cylinder connections.
- Taper: Specified nominal taper values:
- Taper ratio: 3/25
- Taper angle: 6° 52′
- Taper slope: 12%
- Thread form: British Standard Whitworth (BSW) profile with a 55° thread angle. Threads must be cut with profile measurements perpendicular to the cone surface (not perpendicular to the axis).
- Pitch: Nominal pitch P = 1.814 mm.
- Thread rotation: Right‑hand thread (advances away from observer when rotated clockwise).
- Dimensional system: Definitions for major, minor and pitch diameters; reference planes (A, B, F, G); reference lengths and full‑form thread lengths.
- Scope limits: The standard explicitly excludes requirements for mechanical strength, gas tightness and repeat assembly capability. Gauge inspection and acceptance criteria are covered in ISO 11363‑2.
Applications and practical value
EN ISO 11363‑1:2018 is used to ensure interchangeability and correct mating of valves and gas cylinders across manufacturers and markets. Typical uses:
- Design and manufacturing of gas cylinder valve stems and cylinder necks to specified tapers and thread forms.
- Production engineering: tooling, thread cutting, and machining set‑up based on defined tapers, pitches and reference planes.
- Quality control and inspection planning (dimensional checks referenced; gauge inspection per ISO 11363‑2).
- Procurement and specification: calling out compliant thread types (17E / 25E) on drawings and purchase orders.
- Regulatory and conformity contexts where standardized mating interfaces are required.
Who should use this standard
- Gas cylinder manufacturers and valve producers
- Mechanical designers and HVAC / gas systems engineers
- Quality assurance and inspection laboratories
- Standardization and procurement teams in industrial gas supply
Related standards
- ISO 11363‑2 - Gauge inspection for 17E and 25E threads
- Other ISO/CEN transportable gas cylinder standards and national adoptions (EN ISO 11363‑1:2018 is the CEN-endorsed text)
Keywords: EN ISO 11363‑1:2018, ISO 11363‑1:2018, gas cylinders, 17E, 25E, taper threads, valve connection, BSW thread, taper ratio, thread pitch.
