GOTTHARD ROAD TUNNEL FAN REPLACEMENT IN SECTION 64
In the longest road tunnel in the Alps, huge fans ensure that operations can continue safely by replacing over 600,000 cubic meters of air per hour. Every ten years, these MOTOREX-lubricated “lungs” have to be refurbished.
There’s a draft. As there should be, because air quality in tunnels is strictly regulated. Opened in 1980, the Gotthard Road Tunnel between Göschenen and Airolo is no exception. With 11 intake and 12 exhaust fans and 178 exhaust vents, the climate in the Gotthard Tunnel can be controlled in all conditions. Normally this is done automatically using a built-in system of sensors which measure wind, visibility, carbon monoxide, traffi c, air pressure, and temperature. The system is monitored and, in emergencies, controlled manually at the operations and command post in Flüelen. Emergency actions can also be carried out from the Göschenen operations center.
CONCEALED IN THE CEILING
The air ducts and fans in the 16.9-kilometer tunnel are concealed, built into the ceiling. The turbine-like fans are accessible from above for regular maintenance. The space above the fans also contains the hydraulic system that adjusts the blades to control airfl ow and the lubricant circulation system for the rotor bearings. The various fan models weigh anywhere from 16 to 30 tonnes. A fi reproof panel built into the tunnel ceiling gives access to each fan from the roadway so it can be removed from below. The process requires a complete shutdown of the tunnel and is very costly in terms of logistics and manpower.
24 HOUR REPLACEMENT TURNAROUND
An overhauled, working replacement unit for each of the five different fan types is always in stock at the Airolo maintenance center. When the time comes for a major overhaul, Michael Zgraggen (mechanical team leader at the Flüelen maintenance center) springs into action with his ten-person crew. This time a general overhaul is scheduled for the fan in tunnel section 64. The tunnel is shut down from 8:00 p.m. to 5:00 a.m. Once it’s closed, a team on the roadway removes the fi reproof panel from beneath the fan while mechanics above get the unit ready to remove. Space is extremely tight as, after four hours, the nearly 30-tonne fan is lowered from its chamber onto a specially designed lowboy trailer. Workers position the trailer with centimeter precision using lasers and hydrodynamic steering. Next a police escort accompanies the lowboy to the Flüelen maintenance center. The lowboy is driven by a three-axle tractor truck at each end; the whole rig weighs over 110 tonnes.
LUBRICATING THE ROTOR BEARINGS
The biggest of the fans is driven by a 2,920-kW electric motor. The rotor is surrounded by oversized tapered roller bearings at the front of the motor. Since these bearings can only be replaced when the fan is dismantled, they are designed to last a good ten years. Extreme temperature fl uctuations, high bearing pressure, and a warm, humid climate make lubrication a challenge. When the Uri cantonal construction department, responsible for tunnel maintenance, found excess wear on the bearings, it turned to MOTOREX for advice. Following a battery of analyses, the task was accomplished using multi-range MOTOREX Corex HV 100 industrial and hydraulic oil. Lubricant is supplied to the bearings from above and to the side by injection in a closed-circuit system. It flows over the bearings into an oil sump where the lower part of the bearing is continuously lubricated and cooled. MOTOREX Corex is ideal for use in fl uctuating low and high temperature conditions. Its extreme shear stability and long-lasting anti-corrosive properties make Corex HV 100 the perfect choice for the Gotthard Tunnel.
OVERHAUL WITH KNOW-HOW
By now each of the fans in the Gotthard Road Tunnel has undergone a general overhaul three times on a rotating schedule. These overhauls are performed in accordance with manufacturer’s directions at the Flüelen maintenance center. Once the fans have been dismantled and cleaned, all movable parts are measured and those subject to wear are replaced, including the bearings. Even after ten years in service with MOTOREX lubrication, they show only minimal striation. “That’s reassuring,” says Michael Zgraggen, the man responsible for the smooth functioning of the Gotthard Road Tunnel’s mechanical systems for over 25 years. For him, the only thing that counts is absolute reliability. •