Design and construction of gas cylinders
BOC gas cylinders are designed and constructed in accordance with standards and specifications approved by the Health & Safety Executive.
These standards define the material of which the cylinder is made, the method of construction, its test pressure, the maximum permissible filled pressure and the method of regular testing.
Maintenance and testing of cylinders
If you own your cylinders you must be aware of your statutory obligations with regard to maintenance and periodic testing.
If you rent cylinders from BOC then BOC, as the owner of the cylinders, ensures that the requirements of Carriage of Dangerous Goods by Road Regulations 2007 (S.I. No. 288 of 2007), in respect of construction and periodic examination and testing, are met.
Because the owner regularly inspects and tests gas cylinders, there is no need to include cylinders in any Written Scheme of Examination prepared for a pressure system.
Cylinder valves and security caps
All BOC cylinders containing gas at high pressure are fitted with a cylinder valve which must not be removed or tampered with at any time except to tighten the gland nut when necessary.
Some cylinders have a security cap over the cylinder valve indicating that they have been filled and checked. This cap is 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 us and ask for assistance.
Each valve outlet is specially threaded to receive standard pressure regulators which are obtainable from all BOC Trade Outlets.
Regulators should be screwed in by hand and then tightened using the regulator spanner.
To open the 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 replace 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 fitted) in place.
Valve outlet threads
Valve outlets for flammable gases are screwed anti-clockwise to tighten. Valve outlets for non-flammable gases are screwed right-hand (clockwise) to tighten.
To prevent the interchange of fittings between cylinders containing flammable gases and non-flammable gases, the cylinder valve outlets are threaded to opposite hands.
- non-flammable gases such as oxygen, nitrogen, argon and air all have conventional right-hand threads
- flammable gases such as acetylene, hydrogen, propane and mixtures containing fuel gas all have left-hand threads
The only exceptions are special cylinders of dissolved acetylene, specified for purposes other than welding and cutting and some propane cylinders used on fork lift trucks: these cylinders have right-hand thread valve outlets.
These precautions mean that oxygen and fuel gas pressure regulators are not interchangeable. Spindle keys are interchangeable.
The cylinder valves on all gas cylinders, whether they contain flammable or non-flammable gas, are 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 acetylene cylinders which have not yet been returned for this modification. As a general rule for acetylene cylinders, never turn the spindle 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, ask 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 privately owned cylinders. If you possess some of these, please be aware that it is dangerous to change the contents or the external colour without consulting your gas supplier.
NEVER attempt to repair a damaged cylinder
If a cylinder is involved in an incident, withdraw it from service and set it aside, clearly marked. Contact the supplier.
NEVER disguise damage to cylinders
If a cylinder has been involved in a fire NEVER paint over the scorch marks. It is highly dangerous to disguise damaged cylinders before returning them to the gas supplier.
NEVER mix gases in a cylinder
NEVER mix gases in a cylinder; this must only be undertaken by authorised specialist personnel, under controlled conditions.
NEVER transfer gas to another cylinder
Never transfer gas from one cylinder to another. This can result in serious accidents.
NEVER scrap a cylinder you do not own
Only the owner of a cylinder can authorise its scrapping.
Before scrapping, a cylinder must first be destroyed as a pressure vessel. Scrap merchants and cutters should never buy gas cylinders as scrap metal unless this has been done.
If intact cylinders are discovered amongst scrap they should be set aside and the particulars of colour, service, number and markings given to the gas supplier.
Pressure relief devices
Pressure relief devices are fitted to certain cylinders in Ireland. Where fitted they are either:
- relief valves (which re-seal when pressure falls to normal)
- bursting discs (which discharge complete contents)
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.
Manifold cylinder pallets (MCPs)
Cylinders are normally used individually or connected to a manifold by the customer.
MCPs are available for customers who require larger quantities of gas and have adequate handling facilities for off-loading MCPs from the delivery vehicle and transporting them to and from the place of work.
Never remove individual cylinders from MCPs; they are designed and supplied as units and unauthorised removal of individual cylinders could give rise to a dangerous situation.