The key terms and explanations.
Other descriptions: small crane, self-erector, bottom-slewing crane, GMA crane.
- The pivot point (= slew ring) is located directly above the supports on which the crane is standing. This means that the crane rotates at the bottom.
- The power units for lifting (upward and downward movement) and swivelling (rotary movement) are located at the bottom of the crane but also rotate with it.
- The entire crane tower rotates with the crane.
- The dismantled crane is transported on the road as a trailer. Only the concrete ballast must be loaded onto a truck.
- Relatively large space requirement on the ground due to the turning radius.
- Economical erection and dismantling. Only suitable trucks and a loading crane are required.
- Limitation to the hook height: Specific heights are strictly defined and cannot be changed.
Other descriptions: top-slewing crane, element crane, tower crane with trolley jib, GME crane Tower cranes can only be assembled and dismantled with the help of mobile cranes or other suitable lifting equipment. Self-erection and self-dismantling are not possible.
- The pivot point is located below the cabin. Hence only the uppermost part of the crane (the tower head) rotates as a result of which it is known as a top-slewer.
- The power units for lifting and swivelling and the slew ring are located on the upper, rotating part
- The crane tower does not rotate with the crane.
- There are several possible variants for the crane base. The space requirement can be reduced to a minimum. The minimal space requirement is limited to the dimensions of the crane tower.
- Assembling / dismantling and transport are laborious and, thus, also expensive (transport by semi-trailer truck, mobile crane).
- An almost unlimited range of heights (hook heights) can be realised.
For terms and explanations see tower crane
Other descriptions: flat top crane, beam crane Topless cranes largely resemble tower cranes. The only difference is in the silhouette because the tower has no tip – hence they have a flat top.
This feature brings advantages. They can be used, for example, below bridges and high-voltage power lines and close to airports. In addition to this, several such cranes which swivel above and below each other can be used simultaneously.
- The rotating part is flat, there are no unnecessary higher elements.
- For all other features: see tower crane
Other description: luffer,
Luffing jib cranes are principally used in locations where high buildings make it impossible for the crane to rotate freely. The hook height can also be increased by lifting the jib.
- Rather than being horizontal the jib can be raised or lowered.
- Erection / dismantling and transport are very laborious.
- Performance is reduced by the slow raising and lowering of the jib.
- The crane operator must be specially trained to operate the crane.
A connecting element which transfers rotational movements. The slew ring is effectively a huge ball bearing that largely resembles a gear wheel with external teeth. In the case of self-erecting tower cranes the slew ring is located immediately above the crane base / chassis. In the case of tower cranes the slew ring connects the crane tower with the tower head.
The forward-facing horizontal part of the crane. This determines the horizontal reach or so-called jib length. The counter jib is the rear jib. This carries the counter ballast and also – usually – the hoisting winch, which is responsible for the lifting movement.
There is a difference between trolley jibs ,telescopic jibs and luffing jibs (adjustable jibs), on which the inclination of the jib can be altered. The most common variant in Austria is the trolley jib hook. Here, the trolley provides the horizontal movement of the loading hook along the jib.
The distance between the crane tower and the furthermost point on the jib to which the hook can be moved. The jib length (which is sometimes also described as the reach) thus defines the maximum horizontal range of the crane.
The trolley is located on the crane jib and provides the horizontal movement of the hook block and the loading hook. The trolley and the hook block form a single unit. This makes it possible to operate in 2-rope mode (SM variant) or, by reeving the hoist rope, in 4-rope mode (SM/DM variant). This reeving of the hoist rope to 4-rope mode makes it possible to carry the maximum load. 2-rope mode permits a higher end load (at the furthest end of the jib).
If the 2C version of the crane is operated the reeving of the hoist rope from 2 to 4-rope mode is achieved by a second trolley. In 2-rope mode the first trolley remains at the foot of the jib.
Transport axles are required for moving self-erecting tower cranes by road. There are two basic types:
- axles for transport as trailers
- axles for transport on semi-trailer trucks
In order to enable different types of crane to be transported the so-called “adapter” is used at the connection between the crane axle and the crane.
The distance between the hook or its bottom edge and the ground or the top edge of the ground rail. Hence, the hook height also defines the vertical range of the crane.
The maximum load that the crane can or is permitted to handle in a particular position. A distinction is generally made between the maximum loading capacity – the maximum permitted weight of the load – and the loading capacity at the end of the jib which refers to the maximum permitted weight at the maximum reach (at the end of the jib).
Ballast is usually made from concrete and is available in a wide range of sizes and forms. There is a difference between central and counter ballast. On a tower crane the counter ballast is hung on the counter jib. Depending upon the form of the base of the crane the central ballast is piled on either the cross frame base or the undercarriage.
Guidelines for the uniform calculation and designation of numerical data about cranes. In concrete terms these make it possible to compare technical data and to use cranes safely. The values applied by Stirnimann correspond with the latest European Norm EN 14439.
Self-erecting tower cranes always stand on four supports. It is also usually possible to attach chassis or bogies to the supports in order to allow the crane to move along rails. As the crane is driven backwards and forwards along the rails a cable drum winds and unwinds the power cable. In order to ensure that the crane is exactly horizontal the supports have screw shafts that allow the height to be finely adjusted. The supporting base is represented by the external dimensions of the four supports, the square (sometimes also a rectangle), on which the crane is standing, measured to the centre of each screw shaft. If the crane is mobile this dimension also generally corresponds with the width of the track.
There are several variants for the support of tower cranes. The following options for the crane base are available.
- Setting in concrete with fixing angles; the dimensions correspond with the external dimensions of the tower. The fixing angles are lost.
- Cross frame base; this is the simplified version of the normal undercarriage or chassis. The cross frame usually consists of three parts. One longer and two shorter steel beams which directly incorporate the connections for the tower. Base plates of differing dimensions are positioned below the cross frame. These transfer the load evenly onto the crane base. The necessary central ballast is piled symmetrically onto the cross frame all around the crane tower. Various gauges can be realized – as can mobile variants.
- Undercarriage or chassis with mast base element: The undercarriage is very robust. The four lateral anchorings between the mast base element and the undercarriage enable large weights to be lifted and high hook heights to be achieved. Various gauges are possible. The erection /dismantling is more laborious than in the case of a cross frame foundation
The portal is an accessory that can be fixed below an undercarriage or cross frame. Self-erecting tower cranes can also be mounted on such portals.
Portals are executed with a range of gauges and vertical clearances. This makes it possible to walk or drive below the crane. The use of a portal can make sense in, for example, narrow streets where pedestrians and vehicles must continue to be able to circulate.
These motorized accesses for crane operators are mounted either inside or outside the crane tower. They offer the crane operator and, in some cases, erection teams a safe and comfortable way of climbing the tower. In some European countries these systems are obligatory above a certain hook height.