Hitherto restricted to civil structures such as tunnels, bridges, flyovers and underpasses, precast construction is finding gradual acceptance in commercial and residential real estate projects as well. The precast construction method provides benefits such as faster and timely completion of projects, better quality of work, and is less labor-intensive.
The concrete precast sections are factory-produced in a controlled environment, and then transported to site, where they are installed with the help of tower cranes and other equipment. The process requires a high level of precision in the production of the precast sections, and complete accuracy in their placement at site, which is done by high capacity tower cranes.
"The first thing customers look for is capacity. Beams used in precast work weigh around 12 ton or 10 tons at a minimum. There are also very fine margins in the placement of precast components, so customers want a crane with close control. Finally, they will also want the greatest possible free-standing height – typically around 60 m. The most popular Potain cranes for precast construction are our MC 465, MC 475 and MD 689, as well as MD 1100 from our MD Maxi range as these cranes take into account all the factors for precast construction," avers Amol Badgujar, Regional Sales Manager, Manitowoc.
He says that Potain's LVF variable frequency technology automatically adjusts movements to the load on the hook and gives operators greater flexibility in both fast and slow lifts. The technology features in many Potain cranes in India that are purchased for precast work.
Action Construction Equipments (ACE) is providing indigenously manufactured tower cranes of 10 ton to 25 ton capacity. A special grade of steel for mast and associated hardware has been used in the cranes to enable them to lift the heavy concrete sections. All the hardware and components are tested by a third party. The cranes are equipped with VFD (variable frequency drive) for smooth and jerk-free operation while hoisting and slewing.
Says Mayank Pundir, Country Head-Tower Cranes, ACE, "Since the crane operator has to place the heavy concrete precast segments with great accuracy, we have equipped our cranes with Safe Load indicators (SLI), which indicates the weight of the material being lifted, along with the safe load at that radius. In fact, SLI is a third level of safety after the moment limiter and the ergo meter. Our tower cranes are also provided with anemometers to check the wind speed. In high wind speed conditions, tower cranes are not supposed to work, plus the jib is left free to align itself to the wind's direction, thereby reducing the wind pressure on the crane. We also offer an anti-collision device for building projects where two or more tower cranes are working close to each other."
Zoomlion ElectroMech has tower cranes ranging from small models with tip loads of 1.3tons at 50m up to 40tons at 40m. "Heavy capacity tower cranes make construction at sites easier, faster and safer. The mast configuration in our various models gives higher free-standing heights, which is an important criterion in precast construction as it becomes difficult to fix a walling anchor if the design of the building is based on a load-bearing wall structure. Our flattop tower cranes of 10-ton to 150-ton are designed in compliance with JOST German technology to give best-in-class lifting capacity at various radius," informs Arun Bishnoi, Director – Sales, Zoomlion ElectroMech.
"The recent push for affordable homes by the Central Government has seen high demand for precast homes as the volume is very high and timelines are very short. Our cranes are equipped with unique operation control through SLI + PLC + VFD in all motions i.e. hoisting, slewing and trolley, to give micro motion and precise motion control for very high accuracy. Anti-collision device is also provided in case multiple cranes are working in close proximity," he adds.
Krishna Kumar, Divisional Head-Liebherr Tower Cranes India Pvt. Ltd., informs, "Liebherr tower cranes have special features like Micromove for handling precast elements. Micromove helps in achieving a minimal speed and high accuracy while positioning loads, which save time and avoid any damage to precast panels and the structure. The cranes also feature an advanced safety function called 'Guided lowering functions' to help avoid any free fall of loads or malfunctioning of brakes."
Schwing Stetter India has a wide range of XCMG flattop tower cranes from 10 to 25 tons for use in precast construction. Says V.G. Sakthikumar, Managing Director, Schwing Stetter India, "Since tower cranes have to lift heavier loads and withstand heavier dynamic factors like wind speed, the sections of our tower cranes are made of a superior grade of steel and welded by automated robotic welding. To ensure greater reliability, the cranes have superior quality controls, gear boxes and other components sourced from global manufacturers."
Advanced Technical Support
Every step of precast construction requires both macro- and micro level calculations. Project developers, therefore, during tower crane selection, look for the right tonnage, jib length, tip load, precise crane configurations, their safety and other features, and cost benefits. The selection process also involves a close collaboration amongst project heads and crane manufacturers to assess the project's exact requirements, the minimum numbers of cranes that will do the job, and cost estimation.
Arun Bishnoi concurs, "Precast construction is in a nascent stage in India, therefore clients are not aware of many things. They do not take into consideration the correct tower crane estimations during the project planning stage, as the cranes used in precast construction must be of a much higher capacity than required in conventional construction. We at Zoomlion ElectroMech, take all inputs from client such as project completion timeline, element weights, building layout etc. and factor in all these to calculate the cycle times for construction of each structure/building and then select the model and number of cranes to cover 100% building area, stockyard and unloading points."
Zoomlion ElectroMech offers operation and maintenance as a package deal. Service is rendered by well-trained personnel and operators. Regular service camps are organized at job sites so as to minimize breakdowns and machine downtime."
Says Pundir, "Broadly, the two most important criteria in selecting a tower crane are lifting capacity and stability. However, the choice of tower crane for a particular site also depends on factors such as type of loads that have to be lifted; height and horizontal distances that need to be covered; radius of the swing, and time period of the lifting operations. At ACE, we take into consideration all these factors and deliver the right solutions. We also provide customized Autocad solution to customers to maximize utilization of the cranes."
ACE tower cranes are supported by a pan India sales and service network operating from more than 100 locations and with over 50 dedicated service engineers. The cranes are working at various precast construction projects such as the Zuari Cable stay bridge in Goa (being executed by Dilip Buidcon); the Amrapali Developers Housing Project in Noida; the Pradhan Mantri EWS project in Hyderabad (by DEC Infrastructure), the Central Park project in Gurgaon, and the Jain Temples being constructed in Bhopal and Kundalpur.
Sakthikumar informs that Schwing Stetter India provides installation, commissioning with follow-up training for safe operation of the cranes and dismantling of its cranes. "We have a close collaboration with customers right from the conceptualization stage of the project to gather the necessary information pertaining to the weight of the precast sections to be lifted, the radius and height at which the sections are to be lifted, and most importantly, the cycle times that will be required as per the project completion schedule. We deploy the right cranes based on all these factors."
Liebherr has a project department called TCS for Tower Crane Solutions. People from this department and customers discuss the project requirements and the most suitable, economical and technically solutions are proposed. "This service is given for free by Liebherr and customers benefit by executing the project safely and on time. One of the prestigious projects where our cranes are working is in Bangalore, which is being executed by M/s Sobha where 4 Liebherr 550 EC-H 20 cranes are deployed, of which three are on rail version."
Liebherr service engineers render the appropriate training and product familiarization to P&M staff/operators, and the company has service centers in various locations across the country.
Manitowoc's Potain tower cranes are catering to customers like KEF and L&T for precast work in India. "Our customers know our cranes well and value our expertise and insights. We also make sure that we fully understand their needs and the project needs before making recommendations. As the world's leading tower crane brand, Potain cranes offer the best solutions. There is demand for cranes in precast construction, though not widespread yet in India, but certainly better than what it was a few years ago," says Badgujar.
Precast developments that have been completed using Potain cranes include Yenepoya University in Mangalore and the Meitra Hospital in Calicut. Manitowoc's most recent delivery was to KEF of its MD 689 tower crane for a project of Infosys in Bangalore, and another high capacity unit will be delivered by end of February.
According to Badgujar, Manitowoc's customer support is regarded as one of the best in the industry and a reason why many customers continue to invest in Potain cranes. "Manitowoc Crane Care program is built around maximizing crane uptime and delivering industry-leading return on investment to Potain crane owners. We assist customers with installation of the cranes at project sites and give onsite training to operators and technicians. Our service team responds immediately to any technical issues and we stock a high number of spare parts in India so there is minimum disruption caused by repair work," he says.
For proper selection and application of tower cranes, manufacturers must collaborate closely with the contractors, and render end-to-end technical support across the project and equipment's lifecycle. This will instill confidence in the performance and reliability of tower cranes in precast construction, and thereby, such precast projects will gain traction in the building industry.