ISO 13341:2025

Overview

ISO 13341:2025 - "Gas cylinders - Fitting of valves to gas cylinders" specifies the procedures and practices for connecting cylinder valves to gas cylinders using ISO screw threads. The standard covers inspection, preparation and valving procedures for both taper and parallel threaded connections and provides torque values (Annex A) for steel, aluminium-alloy and composite cylinders with metal neck bosses. It also includes guidance on sealants (tape, soft‑metal and PTFE cones) and safe working practices for assembly.

Key topics and requirements

• Scope and applicability: Applies to valve/cylinder combinations with threads in accordance with ISO 11363-1 (taper threads) and ISO 15245-1 (parallel threads); procedures can be applied to other thread systems where compatible (see ISO/TR 11364).
• Inspection & preparation: Visual inspection of threads and sealing faces; removal of old PTFE tape, sealants, paints and contaminants; cleanliness checks to avoid debris entering the cylinder.
• Sealing methods: Approved options include sealant tape, soft metal cones and PTFE cones; compatibility with the gas service must be confirmed (refer to ISO 11114-2).
• Taper thread procedure: Wrap sealant tape from the small end, hand-start valve, then torque using appropriate tooling. Soft metal cones must be sized and worked into the thread; lead-containing cones are not permitted for aluminium cylinders.
• Parallel thread procedure: Use a correctly sized O-ring (conforming to ISO 15245-1) and ensure valve flange seating surfaces are clean and paint-free. Do not use lubricants or tapes in oxidising gas service.
• Torque control & validation: Torques for specific materials/geometries are given in Annex A; periodic validation of applied torque is required. Use calibrated torque tools and avoid exceeding maximum torques.
• Special precautions: Lower torques for aluminium alloy and composite cylinders, avoid valving at elevated temperatures (differential contraction risk), ensure cylinder and valving tool axes are aligned, and follow manufacturer-specific instructions where provided.
• Safety notes: Cleaning remnants of sealants from cylinders that contained oxidising gases carries flash‑fire risk - follow safety guidance.

Applications and users

ISO 13341:2025 is intended for:

• Cylinder and valve manufacturers - to define assembly procedures and printed instructions.
• Cylinder filling and assembly plants - for safe, repeatable valving on production lines.
• Maintenance and inspection technicians - for refurbishment, re-valving and leak‑tight assembly.
• Regulatory bodies and safety auditors - to assess conformity to safe assembly practices. Practical uses include production assembly, routine maintenance, retesting and training of personnel on valve fitting, torque control and sealing methods.

Related standards

• ISO 11363-1 - taper thread specifications
• ISO 15245-1 - parallel thread specifications
• ISO/TR 11364 - thread identification and interchangeability
• ISO 22434, ISO 18119 - condition assessment for cylinders/valves
• ISO 11114-2 - compatibility of materials with gases
• ISO 10286, ISO 11119 series - terminology and composite cylinder design

Keywords: ISO 13341:2025, gas cylinders, valve fitting, taper threads, parallel threads, torque values, sealant tape, PTFE cone, soft metal cone, O-ring, cylinder valving procedures.