CKV’s AC 700 drops an AC 650 down a borehole to help assemble a tunnelling machine

At the Bosporus in Istanbul, Turkey, the Asian and European continents are being connected by means of a gigantic construction project. The project consists of a double-tube train tunnel with a length of 13.6 km and the modernization of 63 km of existing railroad tracks. The Bosporus is crossed in a 1.4 km long, earthquake-proof tunnel that will traverse the straits 56 meters below sea level. At the end of 2006, CKV Heavy Lifting & Assembly Ltd. provided the necessary lifting force for the Yenikapi – Yedikule segment (1,835 meters of tunnel per tube) with three cranes by Terex Demag.

The task: The assembly of a tunnel-boring machine (TBM) with a length of 106 meters and a total weight of 1,000 tons. A Terex Demag AC 700, a Terex Demag AC 650, and a Terex Demag AC 350 were on location. What was special about this: The AC 350 and AC 650 were lowered into the construction pit 15 meters below for the installation work, since the dimensions and weight of the tunnel-boring machine necessitated its assembly directly at the entry point of the tunnel. As a first step, the AC 650 lowered the AC 350 for the pre-assembly of the smaller components. In a second step, the AC 700 hooked up the AC 650 that carried out the final assembly at the entry point.

Crane configuration and load

Lifting a Terex Demag AC 650, which weighs a total of 120 tons, is certainly no easy task. Smaller cranes are frequently lifted up, but it’s very rare to have such a giant dangling from a hook.

The AC 700 crane stood parallel to the excavation trench. The AC 650 was driven behind it in reverse. The star-type outriggers in front and back were turned and fixed in a working position. After the attachment, the AC 700 swung the AC 650 over the trench wall and, with a reach of 14 meters, lowered it precisely into its new application area at the bottom of the construction trench.

In order to save weight, mobile cranes have no special attachment points to allow the placement of a sling or lifting hook to lift the crane. But the outriggers are robust and strong enough to attach the hoisting cables. What is particularly crucial here is the crane’s center of gravity. It is usually located a little towards the front. That is why during this lift more strain is placed on the front supports than the rear ones. In the front outriggers, the weight was at 45 tons each, with 15 tons each at the rear ones. The use of spreader bars prevented placing excessive lateral strain on the supports.

The Terex Demag AC 700

With 700 tons lifting capacity, the Terex Demag AC 700 is the strongest mobile telescopic crane worldwide that can travel with a complete main boom, Terex-Demag says. The 60 m main boom can be carried without exceeding the 12 ton axle load. The enormous increase in the lifting capacity, especially at steep boom positions, is achieved by the Sideways Superlift (SSL) boom suspension system patented by Terex Demag. Thanks to the star-type outriggers, the system deformation is minimized and excellent lifting capacities can be achieved with an outrigger base of only 12.2 x 12.4 m. Despite its high lifting capacity, the crane is compact, with a carrier length of only approx. 18.60 m, offering outstanding driving features due to its modernized drivetrain. It receives its traction force from a state-of-the-art DaimlerChrysler engine (480kw, EuroMot3) and a fully-automatic ZF TC-Tronic transmission with integrated torque converter. The four drive axles (3+4 and 8+9) have differential locks.

At the construction site, the crane distinguishes itself through its excellent maneuverability: eight axles can be steered, one to five and seven to nine. In addition, an automatic leveling feature is offered. The crane can be configured with a luffing fly jib between 24 and 96 meters. With a few maneuvers, the fly jib can be rearranged into a rigid fly jib with a length between 20 and 50 meters, or, as a lighter system, between 6 and 36 meters. A Terex Demag AC 700 contains the know-how developed from the production of the AC 1600, AC 500 and the AC 650.

CKV-Heavy Lifting & Assembly Ltd, headquartered in Ankara, Turkey, is a full service provider in the areas of logistics and crane operations. The company, founded in the early sixties, now offers its customers an extensive portfolio of telescoping and lattice boom cranes – from 20 t cranes to the largest of the fleet, the 700 t Terex Demag AC 700. In addition to its activities in Turkey, the company is active in Europe, Asia, and Africa. Its tasks include heavy lifting and rigging, heavy transportation, assembly and disassembly and international multi-modal transportations and contracting/ sub-contracting European full logistics companies in their activities in Turkey.


CKV’s AC 700 drops an AC 650 down a borehole to help assemble a tunnelling machine CKV’s AC 700 drops an AC 650 down a borehole to help assemble a tunnelling machine