Article from March/April Wire Rope Exchange,
by Stephanie Aurora Lewis, RA, LEED AP
The newest, most revolutionary breakthrough in elevator technologies was conceived by a Finnish inventor in the comfort of his home’s sauna. The curious creator began to experiment with threading together several thin strands of wrapped carbon fiber by hand. Then to build the shape, heat was needed. When his wife said the oven was “off limits,” he took the hand-threaded rope to his sauna to melt the fibers together into a carbon fiber elevator hoisting rope prototype. Through years of extensive testing, KONE’s UltraRope™ is transforming the elevator industry, skyscraper and urban design.
Passenger elevators were introduced by Elisha Otis during the Industrial Revolution at the 1854 New York World’s Fair. In fact, the invention of the elevator itself enabled buildings to soar higher than five stories because people generally would not walk up more than five flights of stairs. Since June 2013, the Finnish KONE elevator company revealed the latest technology that may have the most powerful impact on the built environment since the passenger elevator was introduced.
KONE’s UltraRope diverges from traditional hoisting rope technology with its carbon-fiber-reinforced polymer (CFRP) material core, commonly referred to as carbon fiber or simply carbon. By contrast, traditional elevators use steel wire hoisting ropes. Carbon allows the ropes to weigh only 19% of steel wire ropes, last at least twice as long, and avoid corrosion. Carbon fiber is elastic and only stretches when tensioned to a certain point to compensate for a heavier load. Steel hoisting ropes, however, stretch lengthwise causing the need to typically trim the ropes several times at the beginning of the elevator’s use.
“You wouldn’t think it, but rope weight impacts everything,” says Tomio Pihkala, Executive Vice President, Safety, Quality and Installation, KONE Corporation. “If you have a lighter rope, you can have a smaller and lighter elevator counterweight and sling. This means the overall moving masses are reduced.” Looking rather like black licorice, the wide and flat ribbon hoisting ropes are sheathed in a polyurethane high-friction coating. The UltraRope’s flat bar or belt shape is formed by four longitudinal bars melted together.
Until the cost of carbon fiber drops further, KONE recommends the carbon fiber ropes for travels of 500 feet (150m) and above. UltraRope currently is used with elevators with blocking arrangements where the car and rope speeds are the same (1:1 roping) while blocking arrangements where the car speed is half of the rope speed (2:1 roping) is still in development. Lubrication oils are not needed for the carbon hoisting ropes such as with steel wire rope. While an oil spill is rare, eliminating the need for these lubrication oils reduces the risk of a hazardous environmental waste and associated intervention from the EPA.
Since the carbon fiber hoist rope was invented in 2004, KONE has performed many tests such as lifetime, environmental effects, temperature behaviors, and friction properties in applicable conditions. “We were surprised at how problem-free it was,” says Pihkala. “Often, there are a lot of problems when you develop something completely new. But our faith in this started to grow very quickly.”
KONE has two testing sites, one reliability lab at the Hyvinkää site and another at the Tytyri high-rise testing facility. Tytyri’s testing facilities extend approximately 1,150 feet (350m) underground where the total strength of the carbon fiber hoisting ropes were evaluated. “Then a third-party validation by the Lift Instituut from the Netherlands (an authorized body for both the EU and the US markets) was carried out from early on and throughout the solution creation process,” says Johannes de Jong, Head of Technology of KONE Major Projects & Industrial Ltd.
KONE’s technology team jumped hurdles to test the carbon fiber hoisting ropes at speeds that exceeded 6mph (2.5 m/s). “The shape and structure and the guidance of KONE UltraRope had to perform under very high speeds,” says de Jong. Consequently, the UltraRope has been tested for speeds of up to 34 mph (15 m/s) which is shy of passing four floors in only one second. In order to test the UltraRope fully, KONE built special bending machines, friction testers, and aging equipment. “Testing of [rope] lifetime is a slow process,” says de Jong.
Urban & Environmental Impact
Lightweight elevator hoisting ropes significantly decrease the amount of energy needed to lift the car. De Jong notes, “Hoisting ropes is a component whose weight increases exponentially as the travel distance increases.” In a parallel fashion, the amount of energy saved by using lighter ropes is also exponential. With a 1,640-feet (500m) elevator journey, there is a 15 percent energy savings over using steel wire rope. On a 2,625-feet (800m) elevator journey, the savings are over 40 percent.
While elevator’s traditional steel wire ropes have an average lifespan of seven to ten years, the carbon fiber rope lasts at least two times longer. Even more, KONE also designed a real-time rope condition monitoring system. Passengers can travel up to 3,280 feet (1km) high in an elevator that uses carbon fiber hoisting ropes; twice as high in a single ride than elevators using traditional steel wire ropes. In the World’s tallest building, the Burj Khalifa, passengers take several elevator rides to a number of sky lobbies to make it to the top floors.
In skyscrapers that exceed approximately one hundred floors, carbon fiber hoists reduce the numbers of elevator groupings. This reduction of mechanical space allows the designers more room to use for living spaces. Building owners save on maintenance costs because the ropes are more durable and do not need lubrication. Finally, the ropes have a resonance frequency different than that of the rest of the building. So, in big storms and high winds, the elevators can continue to function safely.
The Urban Land Institute recognizes this technology as having a big impact on urbanization. With less square footage ground space covered, soaring buildings can help to decrease urban sprawl that threatens agricultural lands and habitats. Asia and the Middle East are eager to build taller buildings. If the rumors are true that there are nearly a dozen mega-tall skyscrapers (over 2,000 feet tall) in the works for 2020, the space and energy savings due to carbon fiber hoist ropes would be tremendous. Currently, the Burj Khalifa in Dubai is 2,723 feet (830m) tall. By 2018, Saudi Arabia hopes to complete its first building that reaches approximately 3,280 feet (1 km).
At its beginning stages
Carbon fiber hoisting ropes are at the beginning stages for project installations. KONE’s first UltraRope installation is located at the new Marina Bay Sands hotel in Singapore. “At present, there are some 2000 existing buildings that could benefit from a KONE UltraRope modernization,” says de Jong. “Solutions need to be ecologically sustainable, but also need to be economically sustainable. As costs go down, lower travels will be feasible in the future.”
“We are on the brink of something big. In a sense, we have reinvented the high-rise elevator, says Pihkala. A single strand of carbon fiber is thinner than human hair. Yet, this tiny strand is five times stronger than steel and weighs two-thirds less. A tiny element in the midst of what will be yet the tallest buildings on earth turns out to have monumental, cascading effects on skyscrapers, and urban design for the future.