BS341 Cylinder Connectors: Everything You Need to Know
BS341 cylinder connectors, sometimes referred to as gas bottle connectors or cylinder fittings, are essential components for safely connecting gas cylinders to equipment such as regulators and hoses. These connectors are designed to ensure that only the correct gas is used with compatible systems, preventing dangerous cross-contamination and accidents.
Why Different Cylinder Connectors Exist
Different gases require specific cylinder connectors to ensure safe and proper usage. Each country has its own standards for cylinder fittings, ensuring compatibility with local gas supply regulations. The key reasons for these differences include:
- Preventing incorrect connections – Using the wrong gas in an incompatible system can be hazardous.
- Avoiding dangerous gas mixtures – For example, flammable gases must never be mixed with oxygen as this could lead to serious accidents.
- Ensuring compliance with safety regulations – Each gas has a designated connector type based on its properties and risk factors.
For example, the connector standards for Nitrogen vary depending on the system in use:
- BS 341: No.3 (UK standard)
- DIN 477: No.10 (German standard)
- Nevoc: No.30 (ISO 1545 Standard)
- CGA: No.580 (America/Canadian Standard)
- Afnor: C (French standard)
The type of connector required depends on the origin of the cylinder and where it was filled. In the UK, cylinders must comply with BS341 standards, and the correct fitting can be identified by checking the stamp on the cylinder neck or the cylinder technical label/ datasheet. If in doubt, contact your gas supplier
Types of BS341 Cylinder Connectors
BS341 connectors come in two main styles, each featuring a different sealing face to connect securely to the cylinder valve:
- Bull Nose Connectors – Used for No.3 and No.4 fittings.
- Flat Face Connectors – Require a PTFE washer to ensure a secure seal.
GES Gas Equipment Services Ltd provides PTFE washers as standard with all flat face connectors, and replacement PTFE washers can be purchased separately in packs of 10 – these prolong the life of the connector. It is recommended that the sealing washer is replaced after each Gas Cylinder change to maintain system and gas purity.
Nut Size Considerations
For bull nose connectors (BS 341 No.3 and 4), the nut size can vary. Many technicians prefer longer nut sizes, as they allow for a better grip and easier tightening. Unlike most competitors, GES Gas Equipment Services Ltd offers a variety of nut sizes to cater to different user preferences.
Material Options for BS341 Connectors
GES Gas Equipment Services Ltd stocks the full range of BS341 connectors in 316 Stainless Steel and Brass, with plated brass options available on request. The choice of material depends on the type and purity of gas being used and the environment:
- Industrial gases (Grade 4.5 purity) – Typically require a Brass connector.
- Technical gases (Grade 5.0 purity) Requires Plated Brass
- Speciality gases (Grade 6.0 purity) – Require Stainless Steel to avoid contamination that could damage downstream equipment.
- Toxic / Corrosive gases and their Mixtures – Require Stainless Steel connectors, regardless of grade, for added safety.
Installation and Maintenance
The 1/4” NPT male threaded end of the BS341 connectors are attached to the onward equipment (e.g., cylinder-mounted regulators or flexible hoses) using a sealing tape such as PTFE tape (NOT Pipe Thread type), which is available for purchase from GES Gas Equipment Services Ltd. A specially cleaned tape is also stocked for Oxygen and other oxidising Gas services, if recommended. This tape is pigmented green to avoid confusion with standard PTFE tape.
Technicians should perform visual inspection of the cylinder connector on every usage. They should check sealing faces / washer for any sign of scratches.
To ensure safety and efficiency, connectors should be replaced if:
- The seal is no longer effective.
- The connection is leaking.
- A visual inspection reveals damage or wear.
PTFE tape SHOULD NOT be wrapped around a damaged bullnose / cone sealing face.
Why Choose GES for BS341 Cylinder Connectors?
All BS341 connectors supplied by GES Gas Equipment Services Ltd are sourced from highly experienced UK manufacturers, ensuring top-quality products that meet industry standards. With a wide selection of sizes, materials, and accessories, GES provides everything needed for safe and reliable gas cylinder connections.
Common BS341 Connector Numbers and Their Applications
BS341 cylinder connectors are available in various numbered types, each designed for specific gases and applications. Understanding the differences ensures safe and efficient gas usage.
The following list outlines the standard uses of various British Standard (BS 341) gas cylinder connectors:
- No.3 – Typically used for inert and oxidising gases such as air, argon, helium, krypton, neon, nitrogen, oxygen, and xenon. Common in welding, laboratory, and medical applications.
- No.4 – Designed for flammable gases including acetylene, butane, ethylene, hydrogen, methane, propane, and natural gas. Frequently used in cutting, welding, and fuel applications.
- No.6 – Assigned for specific toxic and corrosive gases like chlorine, hydrogen chloride, phosgene, and sulphur hexafluoride. Used in chemical processing and environmental monitoring.
- No.8 – Primarily used for carbon dioxide (CO₂), often found in beverage dispensing, fire suppression, and industrial processes.
- No.10 – Intended for ammonia gas applications, commonly used in refrigeration and chemical industries.
- No.12 – Associated with sulphur dioxide (SO₂), typically found in chemical and industrial processes.
- No.14 – Used for gases such as nitric acid and nitrogen dioxide, often in laboratory and industrial settings.
- No.15 – Designed for hydrogen sulphide (H₂S), which is used in certain chemical manufacturing processes.
This classification ensures the correct and safe handling of gases across various industries. Always refer to relevant gas safety guidelines and standards when selecting connectors.
Notes:
- A dash (–) indicates that there is no standard BS 341 connector assigned for that gas.
- Always check specific gas handling and safety guidelines before use. If in doubt – contact your gas supplier.
Gas Name | BS Connector No. | Gas Name | BS Connector No. |
Acetylene | 4 | Hydrogen Chloride | 6 |
Air | 3 | Hydrogen Sulphide | 15 |
Allene | – | Iso-Butane | 4 |
Ammonia | 10 | Iso-Butylene | 4 |
Argon | 3 | Krypton | 3 |
Arsine | 4 | Methane | 4 |
1,3-Butadiene | 4 | Methyl Chloride | 7 |
Butane | 4 | Methyl Mercaptan | – |
Butenes | 4 | Monoethylamine | 11 |
Carbon Dioxide | 8 | Monomethylamine | 11 |
Carbon Monoxide | 4 | Natural Gas | 4 |
Carbonyl Fluoride | – | Neon | 3 |
Carbonyl Sulphide | – | Nitric Acid | 14 |
Chlorine | 6 | Nitrogen | 3 |
Cyanogen | – | Nitrogen Dioxide | 14 |
Deuterium | 4 | Nitrous Oxide | 13 |
Dimethylamine | 11 | Oxygen | 3 |
Dimethyl Ether | – | Phosgene | 6 |
Ethane | 4 | Phosphine | 4 |
Ethyl Acetylene | – | Propane | 4 |
Ethyl Chloride | 7 | Propylene | 4 |
Ethylene | 4 | Silane | – |
Ethylene Oxide | 7 | Silicon Tetrafluoride | – |
Halocarbon-14 | 6 | Sulphur Dioxide | 12 |
Halocarbon-22 | 6 | Sulphur Hexafluoride | 6 |
Helium | 3 | Trimethylamine | 11 |
Hydrogen | 4 | Vinyl Chloride | 7 |
Hydrogen Bromide | – | Xenon | 3 |
