Overview
EN ISO 15245-1:2021 (ISO 15245-1:2021) specifies the definitions, dimensions and tolerances for parallel screw threads used to connect valves to medical and industrial gas cylinders. It covers the three standardized thread sizes used for valve-to-cylinder connections: M18 × 1.5, M25 × 2, and M30 × 2. The standard defines the thread form, pitch, sealing features (O-ring recess), thread reliefs and other geometric details needed to ensure compatible valve and cylinder components.
This document does not address:
- Mechanical strength of the connection
- Gas tightness performance
- Capability for repeated assembly/disassembly (this is covered by ISO 13341)
Key topics and technical requirements
- Thread form and rotation: Threads are right‑hand and use the ISO standard 60° profile (ISO 68‑1).
- Pitches: M18 = 1.5 mm; M25 = 2.0 mm; M30 = 2.0 mm (defined with reference to ISO 724).
- Dimensional specifications: Detailed dimensions and tolerances are provided for valve stem threads and cylinder neck threads, including flange diameters, stem lengths, minimum full thread lengths, sealing recess geometry and thread relief lengths.
- O‑ring sealing: Sealing recess diameter and depth, O‑ring internal diameter and cross‑section (thickness) are specified to ensure consistent sealing interfaces between valve flanges and cylinder necks.
- Thread end finish: Chamfering or radiused root options are given (e.g., chamfer 45°/radius values for certain sizes) to avoid sharp first threads.
- Optional vent grooves: Provision for up to two vent grooves on the valve stem is allowed; maximum groove depth is limited (figure note states max 1 mm below root diameter) and edges must be smooth to avoid thread damage.
- Normative references: Includes ISO references such as ISO 724 (pitches), ISO 68‑1 (thread form), ISO 965 (tolerances), ISO 5408 and ISO 10286 for terminology.
Applications and users
This standard is essential to ensure interchangeability, safety and compatibility in the gas-cylinder supply chain. Typical users:
- Cylinder manufacturers and designers
- Valve manufacturers and suppliers
- Medical gas equipment manufacturers and procurement teams
- Industrial gas suppliers, distributors and service technicians
- Testing laboratories and conformity assessors
- Standards and quality engineers responsible for device/component interoperability
Related standards
Keywords: EN ISO 15245-1:2021, ISO 15245-1, gas cylinders threads, parallel threads, valve-to-cylinder connection, M18×1.5, M25×2, M30×2, O-ring sealing, cylinder manufacturers, valve manufacturers.
