High-Performance Lubricants Critical to Bridge Project
EP Editorial Staff | April 22, 2014
When moving parts must function smoothly under heavy load, reliable lubrication is required. A new vertical-lift bridge in France is a case in point.
A concrete-and-steel vertical-lift bridge that opened last May in Bordeaux, France, presented several lubrication challenges due to its design and location. The new Pont Jacques Chaban-Delmas bridge is the longest vertical-lift bridge in Europe (1,421 feet long by 141 feet wide), and spans the city’s Garonne River, which links Bordeaux and the Atlantic Ocean. It provides two lanes for cars in each direction, as well as paths for pedestrians and bicycles on each side. Two additional middle lanes are reserved for public transportation. The bridge’s 384-foot long middle section can be lifted to allow large, seagoing vessels to enter Bordeaux. It takes 11 minutes to reach its lifting height of 174 feet, which occurs about 120 times per year. (See the bridge in action here: www.youtube.com/watch?v=rf2QXfNpahk.)
Because the historical center of Bordeaux is a world heritage site, the bridge had to satisfy not only technical requirements, but also had to fit in aesthetically to meet strict UNESCO criteria for new buildings in historical areas. The area’s strong winds and river currents presented another challenge. This unique project required collaboration among the construction firm, the engineering firm and lubrication expert Klüber Lubrication, based in Germany. Lubricating this extraordinary design with its many moving parts proved a demanding task.
A special high-viscosity grease for rolling bearings that run slowly under heavy loads was recommended for the bearings of the cable drums and winches.
Expert lubrication needed
The Pont Jacques Chaban-Delmas bridge features four freestanding pylons that reach 253 feet from their bases. The pylons support the lifting middle section’s full weight of approximately 2,750 tons. The bridge’s lifting mechanism works like a giant elevator. Its counterweights—four metal bars weighing a total of 2,694 tons—run up and down inside the pylons. They are connected to the middle section of the bridge by sets of cables that run via pulleys 13 feet in diameter, which are mounted at the top of the pylons. In the bases of the pylons, the cables are wound onto drums. The control center for operating the motors and winches is situated on shore. Following an analysis of the system, Klüber Lubrication recommended three specialty lubricants with the characteristics needed to satisfy the requirements of the numerous friction points involved.
The bearings of the cable drums and winches required a grease with a high viscosity, above 1000 mm²/s. Klüberlub BE 41-1501, a special grease for rolling bearings that run slowly under heavy loads, was recommended. It is based on a highly viscous mineral oil (ISO VG 1500), lithium special soap and extremely effective EP/AW additives. To allow for insufficient lubricant supply and ensure emergency lubrication, it contains MoS2 and graphite as solid lubricants.
Because the moving parts in the lifting mechanism are subject to extremely heavy loads, lubrication here had to be reliable and failure-proof. And with some friction points hard to access, relubrication intervals had to be as long as possible. Moreover, as Bordeaux is near the Atlantic Ocean, its air is rich in salt, which has a corroding effect and causes lubricants to deteriorate rapidly. Another requirement was to use only a small number of different lubricants to rule out product mix-up and make purchasing and storage less complex.
Accordingly, Klüber tribologists recommended Klüberplex AG 11-462. This lubricant is specifically developed for marine applications and can cope with a salty atmosphere. It is a brushable, adhesive white operating and priming lubricant that contains an aluminium complex soap, mineral oil and white solid lubricant particles. Klüberplex AG 11-462 is resistant to high loads and offers very good corrosion protection when exposed to sea water. It also offers good adhesion and elevated wear protection at low temperatures due to specially selected solid lubricants and additives. Since the lubricant is white, the need for cleaning the area of application is reduced. Klüberplex AG 11-462 offers numerous uses, such as in gear rim and pinion drives, as well as in bearings. The couplings, joints, locking mechanisms and guideways of the lifting middle section are also lubricated with Klüberplex AG 11-462.
Synthetic gear oils for maximum reliability
Klübersynth GH 6-320—a synthetic high-temperature gear oil based on polyglycol—was specified for use in the bridge’s gearboxes. It offers high resistance to scuffing and micropitting, as well as very good wear protection to prevent premature bearing failure. Thanks to the excellent aging and oxidation resistance of its synthetic base oil, Klübersynth GH 6-320 attains a much longer service life than mineral-oil-based lubricants, leading to longer service intervals. The optimized friction behavior of the polyglycol base oil reduces power loss and improves gear efficiency. Its excellent viscosity-temperature behavior also supports the formation of a sufficient lubricant film at a wide range of service temperatures.
For more information about Klüber lubricants, please visit klueber.com/us.