Handling 33m long precast segments
weighing 75t with the highest safety
Perfectly synchronised handling using two gantry cranes powered by advanced electronics and Wi-Fi technology
EKK is a renowned name in the infrastructure sector and is the largest infrastructure company in South India. It has over 50 construction projects of airports, roads, bridges and regulator bridges to its credit. However, roads and bridges are their speciality. Through a highly competitive bidding, EKK has been awarded the contract for the four-laning of the Thalassery-Mahe Bypass section of NH 17 under NHDP Phase-III on EPC mode in the state of Kerala.
NH 17 is a busy national highway in India that runs along the western coast and connects Mumbai to Kochi (Ernakulam), passing through four states. At 1,296 km, it is the seventh longest highway in India and a vitally important link connecting several coastal towns. In the state of Kerala, the road between Thalassery and Mahe passes through crowded cities, resulting in traffic congestion and slowing down of vehicular movement. To ease the traffic, the government has planned a four-lane bypass between Thalassery and Mahe. This project consisting of an eighteen km stretch is challenging owing to the patches of wetland and loose soil structure. Construction in such a terrain necessitates use of concrete and precast segments are a proven solution allowing faster completion and durability.
Considering the stringent deadline and to ensure the quality of construction, EKK decided to opt for concrete precast segments for this project. The EKK design team decided the optimum size of the precast segments as 33m in length, with a weight of 75t each. However, this posed a challenge at the precast yard while handling such bulky and heavy sections for onward transport.
Lifting a 33m long precast segment, almost 1.5 times the length of a rail coach, is possible only when it is suspended at a minimum of two points. Also, it is vitally important that the lifting is even (i.e., without tilting) at both the ends and that the section always remains parallel to the ground.
In such cases, foolproof synchronisation is essential. Failure to achieve synchronisation may cause the load to tilt or fall, endangering people operating in that area. Uneven lifting may develop internal cracks in a precast section, weakening it and in turn, resulting in its rejection. This obviously implies financial losses and project cost overrun. It also means loss of valuable time, causing project delays and possibly imposition of penalties, resulting in further losses. If, inadvertently, precast segments with internal cracks get used in road construction, safety and durability of the construction are compromised with.
Considering all these aspects, tilt-free handling of precast segments has gained utmost importance in the entire project. After evaluating several options of material handling systems, together with the EKK team, we arrived at the conclusion that gantry cranes are the most viable option.
ElectroMech was the partner of choice owing to its track record of reliable solutions for handling of precast segments at many prestigious infra projects in India and outside. After evaluating several other crane manufacturers, they arrived at the conclusion that ElectroMech was the only company possessing vast experience in this domain and the required competence. Moreover, considering the strict timelines for executing the project, service assurance was also a key parameter while selecting the partner. The service expertise of Cranedge corroborated the decision to go with ElectroMech.
Once on board, the ElectroMech team of experts visited the project site and thoroughly analysed the requirement parameters. Ensuring the tilt-free handling of a mammoth, 33m long precast segment was indeed a challenge for any crane manufacturer. However, our team was confident, as it had successfully addressed several such challenging requirements in the past.
The most pertinent solution for this requirement came in the form of 'twin' gantry cranes, identical in capacity and configuration, both travelling on the same rail. A precast segment can be suspended at two ends with a crane on either side. This allows easy lifting and the load is evenly distributed on both the cranes.
The most important part of the project was to ensure perfectly synchronised movement during vertical lift as well as linear traverse. 'Tandem cranes', or cranes working in perfect synchronisation, is not a new concept to ElectroMech. We have developed a unique technology for this application and have deployed it across several projects in India and abroad.
Out of the two cranes, one is a master crane and the other is a slave crane. The master crane is controlled using multiple options viz. pendant, cabin, RRC or HMI providing higher flexibility to control and operate. The controller is provided with a 'tandem' mode selection option. Once the tandem mode is selected, only the master crane accepts the command and transmits signals instantaneously to the slave crane. This way, both the cranes receive the same command simultaneously, ensuring synchronised movement. With the use of industrial Wi-Fi, signal transmission is instantaneous without any time lag. This perfect synchronisation of the two cranes during vertical movement eliminates the possibility of tilting of the precast segment. Using a similar, tandem movement technique, simultaneous long travel (LT) and cross travel (CT) of both the cranes is achieved.
Use of wireless communication for synchronisation also avoids manual intervention, unlike in other conventional systems, where the operator has to climb up to access the control panel and connect the wires manually.
The project site is in the coastal area of Kerala, which frequently experiences gusty winds and heavy rainfall. Our design team took into consideration these aspects while designing the crane structure, control panels and wireless communication. Everything was designed to withstand extreme weather conditions. Further, digital prototyping and simulation reinforced the trust of the EKK team about the feasibility of our solution.
The entire control system is programmed for automatic sequential check-up ensuring enhanced safety. However, in case of a problem, remote diagnostic facility enables quick resolution.
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