Tower crane is one of the most commonly used lifting equipment on the construction site, also known as "tower crane", with a section of the length (height)(referred to as "standard section "), used to lift the construction of steel bars, wooden, concrete, steel pipes and other construction raw materials. The tower crane is an essential equipment on the construction site.

The function of the tip of the tower crane is to bear the upper load from the boom rope and the balance arm rope, and pass the structural components of the rotating tower, turntable, pedestal, etc., directly through the turntable to the tower structure. The top of the jack-up tower has a truncated conical column type, a forward-leaning or back-leaning truncated conical column type, a hermet-frame type and a diagonal brace type.

All the upper rotary tower crane needs to set a balance weight, its function is to support the balance weight, to form the balance torque required by the design of the opposite direction of the lifting torque. In addition to the balance weight, a lifting mechanism is often installed at its tail.

The reason why the lifting mechanism is placed at the end of the balance arm together with the balance weight is that part of the counterweight can be played, and the distance between the rope drum and the spire guide wheel can be increased to facilitate the winding of the wire rope and avoid the phenomenon of disorderly rope.

The amount of balance weight is inversely proportional to the length of the balance arm, and there is a certain proportional relationship between the length of the balance arm and the length of the lifting arm. The balance weight is considerable, the light tower crane is generally at least 3 ~ 4t, and the heavy one is nearly 30t.