Gas cylinders contain large amounts of stored energy. It is vital that they are made to appropriate standards and are then regularly maintained to ensure the safety of those who transport, fill and use them. All gas cylinders used for the transport of gases by road in the UK are subject to Statutory Regulation. Specifically The Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations which implement the European Agreement on the Transport of Dangerous Goods by Road (ADR). ADR requires that gas cylinders are inspected and tested on a routine basis. This provides assurance that each cylinder is fit for purpose. The test periodicity is laid down in ADR, Packing Instruction P200.
NOTE: The 2015 edition of ADR allows an option to extend the period between inspection and test of certain cylinders to 15 years. This extension has to have the agreement of the National Competent Authority. In the UK this is the responsibility of the Vehicle Certification Agency (VCA), who are an Executive Agency of the UK Department for Transport (DfT). The VCA have published their policy - Extension of the Periodic Inspection Interval for Certain Aluminium Alloy and Steel seamless Cylinders - on their website, under "Cylinders for Gases". A copy can be downloaded here. VCA have a specific policy for LPG cylinders - Extension of periodic inspection interval for LPG cylinders - accessible on the same webpage, and which can be downloaded here.
An inspection is a formal examination of the gas cylinder and its valve. This may or may not be carried out at the same time. For example:
- A pressure test
- A visual examination (internal at time of manufacture and at periodic inspection and testing)
- A check of the marking and labelling
- The correct operation of the valve (or an integrated regulator).
Each cylinder is given an initial inspection and test at the time of manufacture, a pre-fill inspection is carried out prior to each fill and a periodic inspection and test is carried out at set frequencies or when the pre-fill inspection determines a need.
Initial and periodic inspection and testing can only be carried out by an inspection body authorised by the National Competent Authority. In the UK the Competent Authority is the Secretary of State for Transport, within the Department for Transport (DfT). DfT has set up a scheme to appointment inspection bodies in order to meet these obligations. The scheme is operated by the Vehicle Certification Agency (VCA) Dangerous Goods Office. DfT has appointed the United Kingdom Accreditation Service (UKAS) as the delegated ‘accreditation' body. Appointments are made by VCA following an assessment and, if appropriate, recommendation for the appointment by UKAS; successful applicants are issued an approval by the VCA defined by their individual Schedule of Accreditation.
Information on the inspection bodies who have been appointed to undertake various functions in connection with the inspection of tanks and/or pressure equipment can be found on the VCA website. Further information on appointments can be obtained from VCA.
An initial inspection and test is carried out at the time of manufacture by the manufacturer in accordance with the applicable design standards with supervision from a Notified Body selected by the manufacturer. The degree of supervision is dependent upon the choice of the manufacturer and the capability of the manufacturer's Quality Management System.
Pre-fill inspections are carried out at specially equipped filling centres, with qualified staff using appropriate procedures. Pre-fill inspections are required to conform to specific standards, the most common standards are:
- BS EN 1919, Transportable Gas Cylinders. Cylinders for liquefied gases (excluding acetylene and LPG). Inspection at time of filling.
- BS EN 1920, Transportable Gas Cylinders. Cylinders for compressed gases (excluding acetylene and LPG). Inspection at time of filling.
- BS ISO 24431, Gas cylinders. Cylinders for compressed and liquefied gases (excluding acetylene). Inspection at time of filling.
NOTE: Cylinders are only allowed to be filled and transported if they are in date for their periodic inspection and test, however, you are allowed to transport an out-of-date cylinder provided you are returning it to a place where it will be tested.
A periodic inspection and test is carried out by an inspection body. The relevant European standards describing the periodic inspection and testing requirements for cylinders are:
- BS EN 1802, Transportable gas cylinders. Periodic inspection and testing of seamless aluminium alloy gas cylinders.
- BS EN 1803, Transportable gas cylinders. Periodic inspection and testing of welded carbon steel gas cylinders.
- BS EN 1968, Transportable gas cylinders. Periodic inspection and testing of seamless steel gas cylinders.
- BS EN ISO 10462, Gas cylinders. Acetylene cylinders. Periodic inspection and maintenance.
- BS EN ISO 11623, Transportable gas cylinders. Periodic inspection and testing of composite gas cylinders.
BCGA Guidance Note 25 provides guidance on assessing the competency of personnel who are required to undertake periodic inspection and testing of gas cylinders.
After successful completion of the initial inspection and test, and any subsequent periodic inspection and test, cylinders are permanently marked with mandatory stamp marks. The stamp mark will consist of the date of the inspection and the identity mark of the inspection body. In addition, it is good practice to identify the next periodic inspection and test date by the use of a cylinder test ring. Cylinder test rings provide a quick, visual reference. They consist of a plastic disc, fitted between the cylinder and the valve, colour coded and shaped to indicate the year when the next periodic inspection and test is due. This ring may also give an indication of the month. Some companies use two separate plastic rings to indicate the month and year.
It is not acceptable to disfigure or remove these stampmarks, for example by grinding. Where cylinder test rings are fitted they shall always be whole. If there is evidence of deliberate damage to stamp marks or cylinder test rings, for example, split rings, the cylinder is to undergo inspection and test before further filling or use is allowed.
Inspection bodies operate under the control of a Notified Body. A Notified Body is a third-party, accredited body which provides verification and certification services. They ensure and assess compliance to defined standards and regulations, and can also provide an official certification mark or a declaration of conformity. Notified Bodies are appointed to carry out initial inspection of new cylinders and the periodic inspection of used cylinders either directly or authorising others to apply their mark so they can be used and transported throughout the European Union. Additional information on Notified Bodies is available here.
Within BCGA cylinder testing is the responsibility of Technical Sub-Committee (TSC) 2. Members can access information on TSC2 via the ‘Members' area.
BCGA CP 32, The safe filling of beverage gas cylinders.CP 43, The safe filling of gas cylinders.BCGA GN 6, Avoidance and detection of internal corrosion of gas cylinders.BCGA GN 8, Catalogue of gas container marks used by BCGA members and their inspection bodies.BCGA GN 25, Guidance on assessing the competency of personnel undertaking periodic inspection and testing of gas cylinders.BCGA TIS 6, Cylinder identification. Colour coding and labelling requirements.
Cylinder testing providers
Several members of the BCGA have been appointed and offer the services of an Inspection Body and as a Notified Body. Other BCGA member companies carry out cylinder testing and/or a range of associated services. See the full list here.