Engineering Competence
Ferris wheel in Mtatsminda Park in Tbilisi, Georgia.

Wheel keeps on turning

Scheduled inspection of the giant Ferris wheel in Mtatsminda Park in Tbilisi, Georgia, was still months away when the wheel developed an alarming noise. Technical support was urgently needed.

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The Ferris wheel that stands at the foot of Mtatsminda mountain is a whopping 63 metres high and a key attraction at Mtatsminda Park, the biggest amusement park in the city of Tbilisi, Georgia. The 80-year-old park attracts some 1.5 million visitors a year, both local residents and tourists.

Mtatsminda Park

Mtatsminda Park was officially founded in 1938.

The park contains four sites of historical and cultural significance that have state-protected status: the Ferris wheel, the 276.5-metre-tall television tower, the funicular cable-tram used to reach the park, and the Funicular Restaurant Complex, which overlooks the city of Tbilisi and St. David’s Church.

The Ferris wheel was scheduled for inspection in autumn 2017, in keeping with the manufacturer’s recommendations, but before then the park’s service team detected a noise coming from the central section of the wheel. They analysed the sound and determined that it came from the bearings.

There is a crucial issue of people’s safety involved here.

Gela Digmelashvili

“There is a crucial issue of people’s safety involved here, and the safety level must be very high,” says Gela Digmelashvili, the amusement park director. “This is not a production line when the result can lead to costly downtime. In our case, if the Ferris wheel grinds to a halt, people will be stuck up there, feeling uncomfortable and unsafe, and we’ll have to call in the emergency services.” A reliable and long-lasting solution was needed.

The amusement park management reached out to SKF because it was known to have a wealth of experience in the field, having been deeply involved in the design and the assembly of the High Roller in Las Vegas, which stands 168 metres high, as well as other landmark constructions, such as the Navy Pier Ferris Wheel in Chicago and Gothenburg’s Liseberg Amusement Park Observation Wheel.

After a thorough inspection of the Mtatsminda wheel, a number of questions arose. The entire Ferris wheel construction, including bearing units, was manufactured in 2010, but the documentation and technical specifications did not provide any information on the bearings installed nor any instructions on how they should be serviced. Worse, there was no facility for lubricating the bearings.

To repair the Mtatsminda Ferris wheel, SKF supplied two 23188 CAK/W33 spherical roller bearings for the main shaft. SKF LGEV 2 grease, optimal for very heavy loads and slow rotation, was chosen for relubrication.

Finding the right solution was further complicated by a host of factors, says Aliaksandr Badun, head of SKF Industrial Sales for Caucasus and Middle Asia, who worked on the problem with Giorgi Chrelashvili, director of LLC, the SKF authorized distributor in Georgia.

“When we dismantled the bearing unit, the markings had worn down, so it was very difficult to understand what we were dealing with,” says Badun. “Inspecting the bearings revealed that a cage had been damaged, which was the cause of the noise. The park management made the right decision to act quickly, because the situation would have only got worse.”

SKF determined that the customer needed a complete solution for the problem, including correct bearings and greasing options based on the operating conditions. The wheel operates all year round in varied weather conditions and temperatures ranging from –25 to +45 ˚C.

“We also had to take into consideration the very heavy construction weight of 190 tonnes,” says Badun. “Moreover, since there was no way to relubricate the bearings in the original design, we had to create a customer-tailored solution and design a proper lubrication device for the bearings. The grease should provide reliable protection under heavy load conditions and slow rotation, and we selected SKF extremely-high viscosity bearing grease.”

Further complications resulted from the fact that in order to replace the bearings, the entire wheel had to be taken apart. The dismantling and reassembly work was carried out by Kano, a Georgia-based metals services company, using two large cranes, under the guidance of SKF specialists.

“As we were going to dismount the whole wheel anyway, it made sense to carry out full repairs, with all the components stripped back to the metal and repainted,” says Digmelashvili. “It also made finding the optimal solution all the more important as the whole process took a very long time. It made sense to do everything we could to ensure that we wouldn’t have to shut the wheel down again any time soon.

“We are very grateful to SKF for such a quick and effective solution, as are the visitors to our amusement park,” Digmelashvili says. “The installation work results were verified with laser measuring devices, and every component was assembled with accuracy.”

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