Gantry crane
A gantry crane is a location based, but mobile crane.
Description
The gantry crane spans his work area such as a portal. He mostly runs on two parallel rails on which it rests with its supports. This distinguishes them from a bridge crane that runs on elevated tracks. The portal is a steel structure, which is mostly performed in truss or frame construction. The crane has one hinged support and a rigid support to compensate for the temperature-induced change in length of the crane bridge ( the horizontal part of the portal ). Along the bridge crane moves the trolley with the hoist. It can be mounted on the crane bridge and a rail crane. The rails can be moved freely or sunk into the ground. The power supply is usually a motor or spring cable drum, a conductor line, a towing cable system or via sliding contacts in the ground. The drive of the portal must be on both sides same way to travel in order to avoid tilting. The wheels should actually be connected by a rigid shaft, but it is used an electric wave. Here, each wheel is driven by a slip-ring motors. The motors have a common rotor circuit, thereby the slip frequencies and also the speeds the same. The two motors act as two synchronous machines which are fed with a variable frequency. The electric wave has even inherited the tendency to oscillation of the synchronous machine.
Due to its design gantry cranes can lift very heavy loads between supports. Since the supports are vertically loaded, the maximum bending stress on the crane bridge and the lifting capacity of the Seilhubwerks for the maximum possible load is crucial in the first place. It is also not necessary counterweight when the crane bridge does not project beyond the supports. However, this is often the case with portal cranes in harbor facilities, there is the rail on the quay wall very high demands on them, as they support is most burdened. Depending on the boom length, an additional weight on the opposite side to be necessary, this is usually installed in the drive of the support.
The gantry crane can move the load in all three directions.
Area of application
Gantry cranes are used on cargo handling spaces and storage spaces, in addition you will find the assembly ( assembly halls, and in shipyards in shipbuilding ) and the track construction (on track construction trains) application.
Special shapes
In semi-portal cranes, one of the rails is elevated, for example on a hall wall. If both sides are elevated, it is not a gantry crane, but a bridge crane.
A gantry crane, which is operated only stationary and its supports shall not be moved under load with gantry crane is called.
Cranes, which carry a ( paddles ) - Crane on the portal instead of a crane bridge are called Portal ( bobbing ) crane.
Mobile gantry cranes with rubber tires, so-called straddle carriers are used for loading and transporting containers at the container storage areas.
Harbor cranes that are mounted on a small portal are called straddle crane. Most is under the portal room for one or two truck widths or railroad tracks.
Another special form are rubber-tired Potalkrane called RTG ( rubber tyred gantry cranes ) which do not use the guide rail. They are used for container handling at the container storage areas and drive lanes across the container stack and one or more truck lanes. Due to the rubber tires they are able to change the container aisles. They are driven by diesel engines, with a strong trend towards electrification is emerging in recent years by means of slip lines. This is called E-RTG. To change the lanes also E-RTG operate a diesel engine.