H&S - COMPRESSED AIR WORK | INSIGHT


HPCA – INTEGRATED PACKAGE OF GUIDANCE AND STANDARDS


On the topic of HPCA, there is an extensive integrated package of guidance and standards. The headline publication is the ITA/BTS CAWG Report 10.


However, that primarily covers the HPCA process, including operational issues and relevant gas physiology. It does not address the safety of the necessary hardware on the TBM, its manlocks or the TUP shuttle. Report 10 does, though, cover the safety requirements for any surface habitat required as there are no tunnelling industry or diving industry standards for such installations. First published in 2012, Report 10 has been revised three times, the most recent revision being published as discussed, in 2024. The latest revision is a much more comprehensive document than the original Report. Report 10 itself is not a standalone document but provides the add-on guidance covering high pressure mixed gas and saturation exposure techniques, to the BTS ‘Guidance on good practice for Work in Compressed Air.’ The latter addresses the health and safety aspects of compressed air work in general as well as low and intermediate pressure compressed air work. The two documents should be read as a pair.


EN 16191 ‘Tunnelling machinery – Safety requirements’ sets out the essential safety requirements for the TBM,


including those parts relating to compressed air work. The standard is currently being revised with the provisional revised text published in early 2023 and the final harmonised text expected in late 2025. EN 12110 ‘Tunnel boring machines – Air locks’ sets out the essential safety requirements for airlocks. The standard is currently being revised into two parts: Part 1 setting out essential safety requirements for airlocks for air mode exposures and oxygen decompression; Part 2 to set out essential safety requirements for mixed gas use and for saturation exposure techniques along with requirements for TUP shuttles. Part 2 is similar in format to Part 1 but because there are three mixed gas supplies to be controlled, requires a much greater complexity of valves, gauges, etc, as well as gas analysis equipment. In addition, to achieve the performance levels required in CEN standards – which incorporate life safety critical control systems – considerable redundancy and diversity is required. The TUP shuttle is essentially a mobile mixed gas personnel lock but with safety requirements arising from its mobility included. The provisional revised texts were published in early 2023 and the final harmonised texts are also expected in late 2025.


Further additional personnel are required to handle


umbilicals and provide support for transfer under pressure (TUP) shuttle movements. The additional competencies required for mixed gas or saturation techniques are also set out. Section 5 provides guidance on operational


matters, including planning the work, geotechnical considerations, applications in smaller tunnels, and extending the guidance in Section 7 of the BTS Guide. Section 6 of Report 10 deals with plant, equipment


and gas supply. It includes guidance on umbilicals and masks as well as guidance on docking systems for TUP by shuttle. There are also recommendations for the safe movement of the shuttle in both shafts and tunnels. There is extensive guidance on gas supply covering procurement, minimum quantities, mixing, storage facilities, testing, and putting into supply. Compatibility of hoses, valves, etc, with the gases being used is covered along with requirements for oxygen cleanliness of pipework, etc, to mitigate fire/explosion risk. Helium reclaim, which can have commercial benefits, is also discussed. Extensive guidance on requirements for habitats, including their protective enclosures, essential services and facilities for ‘hotel services’ along with accommodation for life support staff is also set out. Section 7 extends the guidance in the BTS Guide on


medical and health matters to HPCA work and life in saturation.


Above: Interior of living compartment of saturation habitat July 2025 | 27


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