New heights of construction15 April 2011
Cranes are an important piece of equipment on any dam construction site. Here IWP&DC takes a look at several projects where cranes are proving their worth
Brazilian dam for Liebherr
Ten Liebherr tower cranes are being used for the construction of the 3150MW Santo Antonio hydroelectric project on the Madeira River in northern Brazil, the only tower cranes to be used on this development.
Eight of the Liebherr tower cranes working at Santo Antonio are of the EC-H Litronic series. Four of these are 630 EC-H 40 Litronic units, which have a maximum lift capacity of 40t and a maximum radius of 80m, at which the crane can lift 5.8t. The other four in the EC-H series are 550 EC-H 40 models, which have a maximum lift of 40t and which can lift 5.2t at the maximum jib radius of 81.5m. Also on site are two Liebherr rail-mounted 111 AS cranes.
Project manager Carlos Augusto Doares da Silva explains why Liebherr cranes were chosen: “The Liebherr units constitute the bulk of our high lift capability, and consequently it is vital that they continue working without unscheduled downtime for the duration of the project.
“They were delivered to the site in 2008 and some of them will still be here in 2016, when the final phase of the project will be completed. So the structural strength of the cranes and their mechanical reliability is essential to us,” he says.
The cranes are serviced by Liebherr Brazil engineers who have been seconded to the site for the duration of the project, which is due to begin first-phase operations in 2012.
Brazilian electricity regulatory agency Agência Nacional de Energia Elétrica awarded the San Antonio dam contract to Consoricio Madeira Energia, which comprises Brazilian construction firm Odebrecht, along with local power utilities Furnas and Companhia Energetica de Minas Gerais (Cemig). The consortium also includes construction firm Andrade Gutierrez and Spanish bank Santander and Portuguese bank Banif.
The dam is of a run-of-river design which is being built across an area of shallow rapids and an island that covers about half of the channel in order to minimise the reservoir footprint. The dam and spillway comprise two 300m concrete structures, one with 15 spans on the left bank of the river and the other with five spans at the channel between Presídio Island and the right bank.Construction of the dam is being undertaken in two stages, with cofferdams on the left bank diverting the flow to allow dry excavation and construction of roughly half the dam and the spillway. The river will then be routed through the completed portion of the dam, with new cofferdams built to protect the works in what will become the riverbed. A second hydroelectric project, Jirau, is being built simultaneously adjacent to Santo Antonio. Jirau will produce 3450MW of power, and the two projects are considered a crucial element for the future supply of electricity in Brazil. Twelve Liebherr tower cranes are also working at Jirau. The two dams together have an estimated cost of US$11.6B and are scheduled to begin feeding the energy grid in 2012. By 2016, they are to be fitted with their maximum combined generation capacity of 6450MW, approximately 8% of the country's total electricity generation.
potain powers up Turkey and Vietnam
The US$1B Boyabat hydropower dam in Turkey is currently home to four Potain special application tower cranes.
Working on the project which is located in the northern province of Sinop are two MD 1100 and two MD 2200 cranes.
Thibaut Le Besnerais, vice president of special applications cranes at manitowoc, says the cranes were custom manufactured to meet the needs of the project.
“Each project is different, and we often modify our designs to achieve the best performance for the given application,” he says. “We also send a highly experienced team of engineers for each installation to supervise the erection and ensure customers get the most benefit from their Potain cranes.”
Main contractor, Dogus Insaat, purchased the cranes specifically for the Boyabat project. It is building the dam for Turkish utility Boyabat Elektrik Üretim. Construction work is taking place in sections, and the cranes are helping manoeuvre a conveyor system to place the large amount of concrete the dam requires in the most efficient manner.
In addition to moving the conveyor trusses for pouring concrete, the four on-site special application cranes are lifting reinforcement bar, penstocks and other components. They are also pouring concrete and working with 6m3 and 9m3 buckets. The cranes can lift 20t loads to all areas of the job site.
The Potain MD 2200 special application cranes have a maximum capacity of 64t and are working with the full 85m of jib at Boyabat. They can lift 20t at their jib end. Both will climb as construction progresses, and by the end of the project, they will reach heights of 104m and 225m. The MD 2200 cranes are equipped with elevators set inside the mast system for operators.
The Potain MD 1100 cranes have a maximum capacity of 40t and are working with 55m jibs, although they can accommodate up to 80m. When working with 55m jibs, the cranes can lift 20t at the tip. One MD 1100 will eventually reach a working height of 120m and the other will reach 137 m.
Upon completion, the Boyabat dam (which will include 2.7Mm3 of poured concrete) will stand 195m tall and span more than 262m across the Kizilimark river. Construction is expected to take 54 months.
The dam will eventually generate more than 1.5BkWh of electricity per year and will help meet energy demand in Turkey, which is rising between 6-8% per year. Once complete, estimates suggest the dam may supply up to 10% of Turkey’s electricity
Seven Potain tower cranes, including five special application cranes, are also playing an integral role in the construction of the Son La hydropower project in Vietnam. This US$3.2B project was commissioned by Vietnam Electricity Corp and construction is under the control of state-owned construction company Song Da Corp.
Minh Chi, Manitowoc dealer for Potain tower cranes, supplied Song Da with the cranes for the project which include two MD 2200s, three MD 900 Bs and two MC 310 K12.
Do Quang Loi, deputy general director of main contractor Song Da 5, says reliability was a key factor in selecting cranes for this job.
“Because of its national importance, we had to have the right crane for the job,” he explains. “Having used Potain cranes on other successful dam builds, we know their efficiency and reliability are second to none. Having a permanent on-site technician was an added bonus.’
Five of the cranes, the MD 2200s and MD 900 Bs, have been on site since August 2008. Since their deployment they have been working constantly, running three shifts seven days a week. The cranes are mostly pouring concrete and building the dam’s penstock system and water intake. Each of the cranes is operating at a different height, ranging from 56-86m. The MD 2200s are working with 80m jibs, while the MD 900Bs are working with 60m jibs and have a maximum capacity of 50t.
With a strict construction timetable, productivity and uptime are essential to the project’s success. Therefore, in addition to Song Da’s own team of technicians, Minh Chi provides a permanent on-site technician while Manitowoc Crane Care personnel also visit the job site regularly to ensure the cranes keep running smoothly. Do Quang Loi said he is confident the project would be completed on schedule.
“The growing concern over energy is reaching every corner of the globe and here in Vietnam we are tackling the issue head-on,” he says. “Being the largest dam in Vietnam, Son La requires the best equipment for the job. Because we have used Potain cranes on other dam projects with great success, we are certain they will keep us on track here.”
Located in northwestern Vietnam on the Da River, the Son La dam will be one of the world’s largest measuring 138m high, 90m wide and close to 1km long. It will have six turbines and require over 3.1Mm3 of roller compacted concrete and 1.2Mm3 of conventional vibratable concrete. Due for completion in 2012, the dam will provide 9500GWh in hydroelectric power each year – equivalent to 10% of Vietnam’s current energy usage.
Swiss installation for Stahl
Modernisation of the 58 year-old Grimsel I power plant in Switzerland entailed replacing one of its two turbine generator units with a higher rated replacement. The original turbines had operated in a cavern below the Grimsel Lake 2000masl but the new turbine was to be lowered 30m below the existing machine room floor in an attempt to further increase yield.
Ever since the power station had been built, an old 140t crane had been used for maintenance work on the turbines in the cavern. However its maximum lift height was insufficient to use it for subsequent inspection work on the new lowered machine. So a modifed hoist was required to a lifting height of 40m.
Swiss company Amacher Technik is a specialist for crane systems in power plants and has been a close partner of STAHL CraneSystems' Swiss subisidiary. When analysing the existing crane system, Amacher reached the conclusion that it was not practicable to modify the old hoist and instead suggested the installation of an additional crane bridge with new, state-of-the-art hoisting technology.
The new crane bridge was manufactured by STAHL CraneSystems in its Ettlingen crane factory and equipped with an 85t eight-rope winch. In addition, an auxiliary hoist for installation work and transporting lighter loads was also requested, and which was also to be used for work on the backflow valve in the gallery to the Räterichboden Lake 40m lower down. For this work, STAHL CraneSystems installed a wire rope hoist with a 10t safe working load which was designed with a relatively high auxiliary hoisting speed to accommodate the maximum lifting height of 40m.
The power plant operators can control the crane with extreme accuracy, while hoisting and travelling speeds are in the region of a few millimetres per second. A specialised Swiss company took on the difficult job of transporting the 13m long crane bridge on site via the steep and winding Grimsel Pass. The narrow approach gallery down to the cavern also presented a particular challenge. In spite of accurate calculations manoeuvring the crane bridge through the 2.5m wide and 2m high cavern approach required precision work.
Since construction was completed the new crane has been used for inspection work on the new turbine. It is also working in tandem alongisde the old crane on the existing craneway.
US awards for K&N Electric Motors
K&N Electric Motors recently won a US$2.9M contract to rehabilitate a 600t bridge crane. The US Army Corp of Engineers requires the work to be carried out at the powerhouse of the 810MW Lower Monumental project on the Snake river in Washington. Work to be carried out includes a new bridge drive arrangement, new crane access gate, repair of defective welds and a new crane fall restraint system.
The Portland District of USACE also awarded K&N Electric Motors work with the rehabilitation of the 100t bridge crane at Dexter dam in Oregon. The main hoists, auxiliary hoists, trolley drives and bridge drives were rehabilitated. A new operator cab, hoist drum and gears were also provided in this US$5.3M contract.
Kuenz systems put to work in Austria
In its portfolio of projects, Kuenz of Germany has provided crane systems for many hydro and dam projects. Amongst these the company supplied the gantry cranes for the Gamp hydropower in Hallein, Austria. The 2x18t capacity cranes have a lifting height of 15.5m. The track width is 11.2m wide and the crane way is 134.5m long. At Austrian pumped storage plant Kopswerk II, Kunz supplied the two powerhouse cranes with a lifting height of 48m and a 130t capacity.
Cranes in brief
• Rehabilitating the cranes at the 1062MW Akosombo hydro project on the Volta river in Ghana has been entrusted to the Sinohydro Corporation of China in a US$5.7M contract. World Bank funding enabled Ghana’s Volta River Authority to undertake the work which will also include rust treatment of the cranes.
• Crane America Services is set to refurbish a 275t bridge crane and a 140t gantry crane at the 198MW Folsom dam in California, US. The US Bureau of Reclamation awarded the US$1.5M contract in September 2010.
• Demands for rough terrain cranes are growing across Africa, the Middle East and Eastern Europe. In response to this Italian crane builder TCM developed a new range of rough terrain models (the RTCW 35 and RCTW 55). The crane’s five-section hydraulic boom which is able to work under load means it can be put to use inside tunnels and galleries, or to shift mechanical equipment and mount overhead cranes without having to remove roofing etc.
• There is currently a K-1800 from Kroll at The Three Gorges Project on the Yangtze River in China. The crane was delivered with a 300 kW hoist winch capable of lifting a 20 ton concrete bucket with a speed of 63 m/min.