The Pont Jacques-Chaban-Delmas is an impressive lifting bridge built of concrete and steel. Opened in spring 2013, it links the Bacalan and La Bastide districts of the city of Bordeaux, which are situated on opposite banks of the Garonne. It is 433 metres long and a maximum of 43 metres wide. It provides two lanes for cars in each direction as well as paths for pedestrians and bicycles on each side. Two additional lanes in the middle of the bridge are reserved for public transport. The most impressive part of the bridge is its 117 metre long middle section, which can be lifted to allow the passage of large vessels, e.g. cruise ships, calling at the port of Bordeaux. This happens about 120 times per year. The bridge takes about 11 minutes to reach its lifting height of 53 metres.
As the historical centre 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 the strict UNESCO criteria for new buildings in historical surroundings. The strong winds prevailing in the region and the whirling waters of the Garonne proved another challenge.
Lubrication calling for experts
The lifting bridge was designed by architects Lavigne and Cheron. Its most prominent features are four freestanding pylons reaching up 77 metres from their bases and resting on a surface area of 11 times 5.3 metres each. It is these pylons that have to support the lifting middle section's full weight of approx. 2750 tons. The construction was executed by GTM from VINCI group. The study was made by the engineering firm NFM Technologies, who cooperated with Klüber Lubrication. The lubrication of this extraordinary design with its many moving parts proved a demanding task, which is why Klüber Lubrication was entrusted with all its friction points.
The lifting mechanism of the bridge works like a giant elevator: counterweights in the form of four metal bars with a total weight of 2694 tons run up and down inside the pylons. They are connected to the middle section of the bridge by sets of cables running via pulleys four metres 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 centre for operating the motors and winches is situated on the right river bank.
Long relubrication intervals matter
All moving parts in this mechanism are subject to extremely high loads and their lubrication must be reliable and failure-proof. Since some of the friction points are hard to access, relubrication intervals were to be as long as possible. Moreover, as Bordeaux is situated near the Atlantic coast, its air is rich in salt, which has a corroding effect and causes lubricants to deteriorate rapidly. Another requirement of the client was to use only a small number of different lubricants to rule out product mix-up and make purchasing and storage less complex.
Three high-performance lubricants for all friction points
Following an analysis of the system, Klüber Lubrication recommended three special lubricants offering the characteristics needed to optimally satisfy the individual requirements of the numerous friction points involved.
The bearings of the cable drums and the winches required a grease with a very high viscosity, i.e. above 1000 mm²/s. Klüberlub BE 41-1501 is a special grease for rolling bearings running slowly under heavy loads. 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 to ensure emergency lubrication, it contains MoS2 and graphite as solid lubricants.
Salt is in the air
Due to the proximity to the Atlantic, the corrosive effect of salt had to be taken into account by the tribologists. Klüberplex AG 11-462 was specifically developed for marine applications and can therefore cope with a salty atmosphere. It is a brushable adhesive white operating and priming lubricant containing 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 also when exposed to sea water. It offers very good adhesion and elevated wear protection also at low temperatures due to specially selected solid lubricants and additives. As the lubricant is white, the need for cleaning the area of application is reduced. Klüberplex AG 11-462 offers versatile uses, e.g. in gear rim and pinion drives, bearings, etc. 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
For the gearboxes involved, Klüber Lubrication selected Klübersynth GH 6-320, a synthetic high-temperature gear oil based on polyglycol. Klübersynth GH 6-320 offers high resistance to scuffing and micropitting as well as very good wear protection to prevent premature bearing failure. Thanks to the excellent ageing 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 optimised friction behaviour of the polyglycol base oil reduces power loss and improves gear efficiency. Its excellent viscosity-temperature behaviour supports the formation of a sufficient lubricant film also at elevated or high temperatures. Klübersynth GH 6-320 has a wide service temperature range.
The reliable lubrication of moving components is essential to protect installations against failure, especially if they are as large as in this example. Tribology experts like Klüber Lubrication have the comprehensive expertise required and actively assist operators in their activities from the planning stage to the actual building.