Overview
ISO 3500:2005 - "Gas cylinders - Seamless steel CO2 cylinders for fixed fire‑fighting installations on ships" defines the external dimensions, accessories, filling ratio and marking for seamless steel carbon dioxide cylinders intended for fixed shipboard fire‑fighting systems. The standard ensures interchangeability of cylinders used on cargo ships, passenger ships, salvage and heavy‑lift vessels, tug‑barge combinations and offshore drilling/production platforms that can be serviced in port or dry dock.
Key topics and technical requirements
- Cylinder design and test pressure
- Cylinders shall be seamless steel and designed/tested to a minimum test pressure of 25 MPa (250 bar) and conform to ISO 9809 (Part 1, 2 or 3 as appropriate).
- Principal dimensions and capacities
- Provides nominal outside diameter and length ranges for reference sizes A, B (preferred) and C; suppliers must certify minimum internal water capacity.
- Filling ratio
- Maximum permissible filling ratio: 0.667 kg CO2 per litre of cylinder water capacity (two‑thirds).
- Valves and discharge performance
- Valve inlet: 25E taper (ISO 10920).
- Valve outlet: W 21.8 mm × 1/14" ext. right‑hand / DIN 477 Outlet No. 6.
- Valve/siphon design must allow 85% of CO2 to be discharged into the protected location within 2 minutes. Siphon tubes must be durably fitted.
- Distance H (neck collar to valve outlet centreline): 25–40 mm.
- Pressure‑relief device
- A relief device preventing pressure rise above 22.5 MPa (225 bar) is required; commonly a bursting disc (tolerance ±10%).
- Identification and marking
- Cylinder shoulder finished safety red (RAL‑3000 / PMS‑185) with white stencil “CARBON DIOXIDE” or “CO2”.
- Permanent stamp marking per ISO 13769 showing CO2 symbol, maximum filling mass (e.g., 45KG CO2) and tare (e.g., TARE55,4KG).
- Presence of siphon tube indicated by a corrosion‑resistant ring between valve and cylinder.
Applications and users
ISO 3500:2005 is used to specify and inspect CO2 cylinders for:
- Shipbuilders, naval architects and marine safety engineers designing fixed fire‑fighting systems
- Manufacturers of seamless steel CO2 cylinders and valves
- Classification societies, port authorities and ship operators for equipment acceptance
- Service and filling stations that fill, test and maintain CO2 cylinders on vessels and offshore platforms
Adopting ISO 3500 helps ensure spare cylinder interchangeability, safe discharge performance in emergencies, and compliance with maritime fire‑safety regimes.
Related standards