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How Are Tower Cranes Built Or Set Up?
The one question that many people ask when they drive past tower cranes being used to erect skyscrapers is how on earth these machines are built. They stand so tall that it doesn’t take a genius to figure out that another crane has probably been used somewhere in the setting up. In this article, we have aimed to explain how tower models in particular are erected in the hope that you will develop a far greater appreciation for these useful machines.
- Mast Section
The mast section of a tower cranes is set into a foundation using steel pedestals. It is plumbed to a degree of 1:500 (meaning that it must not deviate more than an inch from plumb for every 500 vertical inches). Concrete is poured and, once it has cured, the crane itself is ready to be erected.
- Base Section
The first piece to be set is the base. Bolts are installed using nuts that have been torqued with a hydraulic wrench (to as much as 4300 feet and pounds). The process continues with mast sections being added until the necessary height has been achieved.
- Turntable SectionTower Top
Once the turntable has been successfully installed, the tower top is added. Four large pins are added as the connecting members. Whilst the bolts on the mast section are being tightened, the jibs for the crane are assembled.
- Counter Jib
The counter jib is erected as a single piece. It is connected via large gates or pins at the turntable. It is then elevated to about 15 degrees above horizontal and the pendants are connected using pins with cotter pins. The counter jib is then lowered to horizontal. Sometimes, the machine package (with electrical panel and hoist) is installed with this jib and, other times, it is installed separately.
- Working Jib
The working jib is also installed at the turntable and elevated. The hoist is then connected to the pendant attached to the jib, pulled to the tower top and connected with a pin. The jib is then lowered back to horizontal.
- Jib Outer Section
The installation of the jib outer section is completed via three pins. Finally, the ballast is installed on the counter jib and the structural setting up of the tower crane is complete. This usually marks the end of the first day.
To make the tower crane operational, ropes must be installed. A hook is moved along the working jib using a trolley; ropes are attached to the trolley and a winch. The load line is installed next; it runs from the back of the crane, through the tower top and out under the jib to the outer tip. The final process in making the machine operational is to set the motion limits for the hoist and the trolley, followed by the completion of a load test.
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