Handling Cylinders

BOC gas cylinders are designed and constructed in accordance with national and international standards and specifications

Design and construction of gas cylinders

BOC gas cylinders are designed and constructed in accordance with international regulations, standards and specifications. These define the material from which the cylinder is made, the method of construction, its test pressure, the maximum permissible filled pressure and the requirements for regular testing.

Periodic inspection and testing of cylinders

If you own your cylinders you must fulfil your statutory obligations with regard to periodic inspection and testing.

If you rent cylinders from BOC then BOC, as the owner of the cylinders, ensures that all legal regulatory requirements are met. This includes, for example, in relation to The Carriage of Dangerous Goods and Use of Transportable Pressure Receptacles Regulations, in respect of construction and periodic examination and testing.

Because cylinders are covered by these transportable equipment regulations, there is no need to include cylinders in any Written Scheme of Examination prepared for a static pressure system (for example, which comes within the scope of the Pressure Systems Safety Regulations).

Cylinder valves and security caps

Security caps

All BOC cylinders are fitted with a cylinder valve which must not be removed or tampered with at any time.

Some cylinders have a security cap over the cylinder valve indicating that they have been filled and checked. Immediately prior to use, this cap may be removed by rotating the hexagon nut in either direction using the regulator spanner. This will cause the cap to split for easy removal.

If you have difficulty removing the security cap, please contact BOC and ask for assistance.

Pressure regulators

Valve outlets are specially threaded to receive suitable pressure regulators or manifold hoses.

Regulators should initially be screwed in by hand and then finally nipped and tightened using a spanner.

To open a spindle-key type cylinder valve, rotate the spindle anti-clockwise using the special spindle key K5, which is obtainable from BOC Trade Outlets.

Some cylinders are fitted with handwheels which remove the need to use a spindle key.

Valve guards and protection caps

Cylinders fitted with handwheels (and some others fitted with valves) are normally fitted with valve guards or valve protection caps.

Valve guards should not be removed. Valve protection caps should always be replaced after use. Always return your cylinder with the valve in the closed position and the valve guard or cap (where provided) in place.

Valve outlet threads

Valve outlets threads for flammable gases are usually left-hand threaded, i.e. turned anti-clockwise to close. Valve outlets threads for non-flammable gases are usually right-hand threaded, i.e. turned clockwise to close.

This convention helps to limit the inappropriate interchange of fittings between cylinders containing flammable gases and non-flammable gases.

  • non-flammable gases such as oxygen, nitrogen, argon and air generally have right-hand valve outlet threads
  • flammable gases such as acetylene, hydrogen, propane and mixtures containing fuel gas generally have left-hand valve outlet threads

This guide applies generally, but has some exceptions such as for some special cylinders of dissolved acetylene, specified for purposes other than welding and cutting, and some propane cylinders used on fork lift trucks, which may have right-hand thread valve outlets despite being in nominally flammable service.

The convention means that oxygen and fuel gas pressure regulators are usually not interchangeable. Spindle keys are interchangeable.


The cylinder valves on all gas cylinders, whether they contain flammable or non-flammable gas, are right-hand threaded, i.e. opened by turning the spindle anti-clockwise and closed by turning the spindle clockwise.

NEVER open an acetylene cylinder valve completely: 1.5 turns is sufficient

BOC permanent gas cylinders are all fitted with cylinder valves in which the spindles have collars to prevent them being completely unscrewed. There may, however, still be a few dissolved acetylene cylinders which have not yet been returned for this modification. As a general rule for dissolved acetylene cylinders, never turn the spindle more than one and a half turns, and certainly no more than three revolutions.

NEVER leave the opened spindle of any cylinder valve against the backstop

An opened spindle should NEVER be left against the backstop, but should be turned back at least half a turn to avoid seizure in an open position.

NEVER tamper with cylinders in any way; if in doubt, refer to your gas supplier

Never repaint, change markings or identification, or interfere with valve threads. In most cases the cylinders are owned by the gas supplier, but there are some non-gas-supplier owned cylinders.

NEVER attempt to repair a damaged cylinder

If a cylinder is involved in an incident or otherwise appears to be damaged, withdraw it from service and set it aside, clearly marked. Contact the supplier.

NEVER attempt to disguise damage to cylinders

If a cylinder has been involved in a fire NEVER try to disguise this, for example by painting over the scorch marks. It is highly dangerous to disguise damaged cylinders.

NEVER fill or mix gases in a cylinder

NEVER mix gases in a cylinder; this must only be undertaken by authorised specialist personnel, under controlled conditions. It is illegal and lethally dangerous for unauthorised parties to fill cylinders, including by mixing, topping-up or by transferring contents from one cylinder to another.

NEVER attempt to scrap a cylinder you do not own

Only the owner of a cylinder may scrap it.

Scrap merchants and cutters should never accept or handle gas cylinders as scrap metal unless from the cylinder owner, after the items have been safely processed, de-valved and depressurised. Those in possession of asset owner’s cylinders shall never offer them for sale or transfer to any other third party – they must be returned to the owner.

If cylinders are discovered they should be set aside and the cylinder owner (usually the gas supplier) notified to arrange collection.

Pressure relief devices

Pressure relief devices are fitted to certain BOC cylinders in the UK. Where fitted they are either:

  • relief valves (which re-seal when pressure falls to normal)
  • bursting discs (which discharge the whole cylinder contents, if operated)
BOC propane cylinders are fitted with pressure relief valves which operate at approximately 26 bar. Carbon dioxide (CO2) cylinders are fitted with a bursting disc which operates at approximately 180 bar. This disc is fitted on the cylinder valve.

Bundles, also known as packs or Manifolded Cylinder Pallets (MCPs)

Bundles are available for customers who require larger quantities of gas and have appropriate handling facilities. All bundles are designed for Fork Lift Truck-handling.

Whilst all bundles may be FLT-handled, do not attempt to lift a bundle by means of suspension lifting unless the bundle has been specifically certified for lifting (not all bundles are so rated), for example, are pi / rho marked, certificated and equipped with appropriate attachments. Suspension-liftable bundles will usually require to be specially ordered and specified.

Never interfere with a bundle. Do not mark, damage, disassemble or deface any item. For example, do not remove individual cylinders. Bundles are legally certificated assemblies, designed and supplied as units. Unauthorised dis-assembly or removal of individual cylinders is illegal and lethally dangerous.

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