The International Marine Contractors Association (IMCA) has published an information note on non-destructive evaluation (NDE) testing of gas cylinders.
Advancements in NDE testing techniques for gas cylinders have been the subject of extensive discussion by members of the IMCA Diving Division Safety, Medical, Technical & Training Committee (SMTT). A dedicated workgroup of industry experts was established to take the issue forward and to develop an update of detail sheet 9.1 of IMCA D 018 – Code of practice on the initial and periodic examination, testing and certification of diving plant and equipment. The updated detail sheet 9.1 of IMCA D 018 will be included in the next revision of IMCA D 018. The information note (IMCA D 08/11) is available to IMCA members on the ‘members-only’ website.
The detail sheet sets out additional guidance for the possible use of ultrasonic NDE testing techniques in place of a five yearly internal examination and overpressure test, provided that certain key prerequisites have been met. Internal moisture levels are a key factor to consider when using such testing techniques and, as such, NDE testing of cylinders used for compressed air storage would not be appropriate.
The information note stresses six key points:
- The ultrasonic testing system used must conform to the requirements of ISO 6406:2005 (section 11.4 – ultrasonic examination);
- In many countries there are detailed national regulations concerning gas cylinders, particularly if these are transportable. Such regulations must be complied with, even if they conflict with or are more onerous than the recommendations given above;
- Hydraulic testing of large storage tubes subject to dry internal service is not recommended as it introduces moisture in to the system which may prove difficult to remove. In such cases pneumatic or gas overpressure testing may be substituted;
- If testing is not hydraulic and the competent person requires it then other testing such as wall thickness measurement or acoustic emission testing may also be required;
- Some national regulations, certifying authorities or gas cylinder codes may give no option but to apply hydraulic overpressure testing;
- In all types of overpressure testing, suitable safety precautions must be taken to ensure the safety of all testing personnel and others.
- It is recommended that a pressure leak test is carried out after hydraulic test in order to detect any possible leakage of the pillar valve stem seals prior to return to service.
Further information on IMCA is available at www.imca-int.com and from the association at 52 Grosvenor Gardens, London SW1W 0AU, UK. Tel: +44 (0)20 7824 5520; Fax: +44 (0)20 7824 5521; firstname.lastname@example.org