Civil Engineering Reference
In-Depth Information
Fig. 11.29
The transportation of
the divers in the
pressure-shuttle
During diving operations - increasing by depth and diving time - body tis-
sues become saturated with the gas mixtures that have been inhaled. The
tissues must get rid of those gases (e.g. nitrogen) again in a dosed manner,
comparable to the slow decorking of a bottle of champagne.The 'decorking'
must be dosed as such, that there are no nitrogen bubbles which could
result in the blockage of capillaries. If that does happen, decompression ill-
nesses like bends and staggers could come about: severe pains in the joints
and skin disorders (bends) or in the most serious cases, disorders of the
central nervous system (staggers).
By using diving tables especially developed for the project which are differ-
ent dependent on the working depths, the diving time and the gas mixture
used, reducing the pressure in steps while simultaneously inhaling 100%
oxygen, the decompression illnesses could largely be prevented.
Working under increased air pressure up to 4.5 bar
The type of work that the divers carried out consisted of inspecting the
cutting wheel, the replacement of the cutting teeth of the cutting wheel
when these were worn out, and activities for the various repairs.
The excavation chamber, which was accessible via an air lock, was generally
filled with air placed under increased pressure during diving activities.
During diving operations of a short duration, the divers could (up to a pres-
sure of approximately 4 bar) work without special breathing apparatus. The
decompression time amounted to a maximum of 2 hours, also because of
the not very comfortable circumstances in the decompression chamber. At
the end of every diving operation a medical check was undertaken in which the
divers were observed for a period of four hours.
At pressures above 3.6 bar, symptoms of nitrogen narcosis were observed.
Divers worked slower and made more mistakes. After 672 'compressed air
exposures' there were three cases of decompression illness (bends) at a pres-
sure of 3.9 to 4.2 bar.The activities which were carried out then were excep-
tionally heavy: the switching of digging teeth. Besides, the divers had been
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