First of all, the height from ground to the roof top was only 60 meter but the lifting height for the grab (64 metric tons) was 52.50 meter. The roof and trusses were not allowed to be opened by the client despite the space limitation. Therefore, it left a limited boom height of only 2.5 meter for our cranes boom clearance. To overcome this limitation, we extended our boom length to only 55 meter and the lifting lug was welded to suit the length of the slings in order to reduce the working height.