Tunnels and underground shafts have different tasks. They can serve as access to plants and machinery or for inspection and maintenance. They can also provide ventilation or venting of underground caverns and landfills. In principle, galleries and shafts must be designed in such a way that the penetration of dangerous and explosive gases is largely prevented. Nevertheless, before people enter an underground structure, it must be ensured that no explosive atmosphere has formed there.
Therefore, tunnels, shafts and galleries must be ventilated as a precaution.
"The air velocity must be monitored" according to BGR 127 section 5.4.16. This is done with flow sensors. Mobile or permanently installed systems can be used here.
For this purpose, the flow velocities for the ventilation of the shaft / landfill facility, tunnel, mine shaft or final disposal site are defined in advance. In addition to explosion protection, fire protection must also be taken into account. Here, it is necessary to remove the air and thus the oxygen from the source of the fire. The fans must therefore work in the opposite direction. Thus, two flow sensors must be used, one for each direction. Alternatively, a sensor with direction detection already integrated can be used.
Application example / reference Cavern power plant in Wehr in the south of Baden-Württemberg
The power plant is a pumped storage power plant with a generator capacity of 910 MW. It has a lower and an upper basin. On the one hand, the water can flow through the generator from the upper to the lower basin and produce electricity. On the other hand, in times of electricity surplus, water can be pumped back into the upper basin by means of the pumps and thus energy (positional energy) can be stored. The machines, i.e. the pumps and generators, are housed in a cavern, a hollow space blasted into the rock. This space is accessed at the Wehr power plant via a 1.3 km long access tunnel. The cavern must be ventilated and de-aerated. This is done via various tunnels and channels with cross-sections of approximately 8, 9 and 17 square metres. The fresh air gallery in particular is operated in reverse during a fire and is intended to ensure that the air and thus the oxygen is removed from the fire.
Since 2022, the flow in the various tunnels has been monitored there by means of three stationary flow sensors from Höntzsch.
The measured values are monitored in the control room, where all the power plant's measurements converge. In the future, these measured values will be used to control the frequency-controlled fans.
![[Translate to English:] Schacht- und Deponieanlagen, Verkehrstunnel, Bergwerkstollen, Endlagerstätten](/fileadmin/media/graphics/content_images/Branchen/Illustrationen/Tunnel_Schacht.jpg)
