Waterbury Democrat., 1902-05-27
TUNNEL VENTILATION.

In the yentilating plant used at the Simplon tunnel the two sets of fans on the north side and on the southern side of the tunnel are identical, put there are some minor differences in the location of the fans and of the air. ways. Thus on the north side the fan building is constructed close to the tunnel portal, while on the south side it is separated therefrom by the Sim plon-Varza road. There are two fans at each end of the tunnel, each of which is 3, ,75O metres (12.3 ft) in diam eter. There is a suction opening on each side of the fan disc 1,25 metres (41O ft) in diameter. Each fan is driven direct by continuous current motor capable of exerting POO horse power at speed of 400 revolutions a minute In normal working, however, the fans are run at $50 revolutions per minute, at which speed they absorb 15O horse power each, and can each deliver 25 cubic metres (SS2.S cubic feet) of air per second against water guage of 25O millfmetres 9.84 in.) This ventilating plant is intended to be used for the ventilation of the tun- nel, not only during the period of con-
 
 A feature of special interest is the air passages and shutters by which a number of different methods of work ing the fans are possible. Either can be worked separately, and can then be used to force air into the tunnel or to suck it out, since the openings into the tunnel can be connected up with either the suction or the deliv- cry passages of the fan, suitable doors and shutters being provided for the purpose. The two fans can also be worked. simultaneously forcing into the tunnel or withdra wing from 1t air at the rate of 1.765.6 cubic feet per second. Again, the delivery from one fan may be coupled up to the suction of the second, in which case the two work tandem" fashion, and can force or extract air against a higher pres sure. As at present arranged the fans force air into the lateral gallery which is later on to be enlarged into a sec ond single-line tunnel. This air re- turns to the portal thrugh the finished portion of tunnel No. l.
 When checking the axia1 line of the tunnel, however, a different plan of ventilation is followed. The air pas sages are changed over so that the fans draw air from the side gallery. fresh air entering through the portal of No. l tunnel. The ventilation thus obtain ed is excellent, and the atmosphere re- mains remarkably free from fog. so that it is possible to sight direct to the working face at a distance of 5000 metres 16.4O0 feet from the tunnel portal. The main air current does not reach the working face, and hence aux Hilary blowers are used for this pur- pose. These consist of couple of fans mounted on one and same bed plate and driven by Pelton wheels working under head of 80 atmospheres, and giving about ten horse power effective. The fans, which measure 560 milli- metres (25.1 inch) in diameter, are run at 2.5OO revolutions per minute. and deliver each 0.75 cubic metres (26. : cubic feet) of air per second under a head of 800 millimetres (1S7 inchl of water. The two fans can be coupled either in series or parallel similarly to those in the main fan building at the tunnel entrances -Schweizerische Bau- Zeitung.