ISO 15245-1:2021

Overview

ISO 15245-1:2021 specifies parallel screw threads used to connect valves to medical and industrial gas cylinders. The standard defines terms, dimensions and tolerances for three nominal thread types: M30 x 2, M25 x 2 and M18 x 1.5. It clarifies thread form, pitch, thread-end finish, O‑ring requirements and marking conventions, but does not address mechanical strength, gas tightness or repeated assembly durability (see ISO 13341 for repeated assembly).

Keywords: ISO 15245-1, gas cylinders, parallel threads, valve connection, M30 x 2, M25 x 2, M18 x 1.5, O-ring, thread dimensions, tolerances

Key topics and technical requirements

• Thread types and pitch: M18 × 1.5, M25 × 2.0 and M30 × 2.0 (ISO metric pitches from ISO 724).
• Thread profile: ISO standard 60° metric thread form (ISO 68‑1); right‑hand rotation.
• Dimensions & tolerances: Detailed minimum/maximum values for valve stem and cylinder neck (including flange diameter, stem length, sealing recess, thread relief and minimum full thread length). Tolerances reference ISO 965 series.
• O‑rings: Internal diameter and cross‑section sizes are given (sized per ISO 3601‑1). Recommended hardness nominal 90 Shore A and material compatibility with contained gas (see ISO 11114‑2). Note: dimensional tolerances can cause O‑ring overfill - manufacturers must verify performance.
• Thread end finish: Chamfer (45°) or radius specified for valve stem and cylinder neck openings.
• Optional vent grooves: Up to two vent grooves, maximum 1 mm depth below root diameter; edges must be smooth to avoid damaging mating threads.
• Marking: Threads must be marked with “18P”, “25P” or “30P” to indicate M18, M25 and M30 parallel threads respectively.

Applications and who uses it

ISO 15245-1 is used by:

• Cylinder manufacturers and fabricators producing neck threads for valves
• Valve and fitting manufacturers designing valve stems and O‑ring interfaces
• Medical gas equipment suppliers and industrial gas producers
• Design engineers, quality and inspection labs checking thread conformity
• Procurement and regulatory bodies ensuring interchangeability and safety of cylinder/valve assemblies

Practical applications include ensuring compatibility of replacement valves, standardizing production tolerances for mass manufacturing, and supporting safe, gas‑compatible sealing interfaces across medical and industrial gas supply chains.

Related standards

• ISO 13341 - Fitting of valves to gas cylinders (repeated assembly capability)
• ISO 68‑1, ISO 724, ISO 965‑1/‑2 - Metric thread forms and tolerances
• ISO 3601‑1 - O‑ring sizes and tolerances
• ISO 11114‑2 - Material compatibility for non‑metallic components

For manufacturers and engineers, ISO 15245-1:2021 ensures consistent, interchangeable parallel thread connections between valves and gas cylinders.