Page 71 - Safety and health in construction
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Cofferdams and caissons and work in compressed air
Signalling
10.2.21. Reliable means of communication such as bells, whistles or telephones
should be maintained at all times between the working chamber and surface
installations.
10.2.22. The code of signals should be conspicuously displayed in convenient
positions at workplaces.
Lighting
10.2.23. All locks and working chambers should be provided with adequate
electric lighting.
10.2.24. There should be two separate lighting installations supplied from
independent sources of current.
10.3. Work in tunnels in compressed air
10.3.1. The bulkhead separating the working chamber from areas of lower
pressure should be of sufficient strength to withstand safely the maximum pressure to
which it will be subjected.
10.3.2. When necessary to prevent danger in the event of rapid flooding, the
bulkhead should be sufficiently close to the face or shield to allow the workers to
escape in an emergency.
10.3.3. Safety bulkheads should be provided within 60 m of the working face in
all tunnels having a danger of inrush of water or material.
10.3.4. If the compressor is driven by electricity, stand-by compressor plant
should be provided capable of maintaining at least 50 per cent of the air supply if the
electrical power fails.
10.3.5. If the compressors are not driven by electricity, not more than half of them
should be driven from the same source.
10.3.6. Each air line should be equipped with an adequate air receiver, a stop
valve, a pressure-reducing valve, and a non-return valve close to the man locks.
10.3.7. The air supply should be provided by duplicate air lines between the air
receiver and the working chamber.
10.3.8. An adjustable safety valve should be fitted on the outside of the bulkhead
to a separate pipe leading from the working chamber through the bulkhead to the
outside air.
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