User talk:Crane Dong

Overhead crane configuration
Overhead crane mainly have two configurations: Top running overhead cranes and under running overhead cranes.

Top running overhead cranes
The top running overhead crane or bridge crane refers to the crane which has the bridge travel on the top of rails mounted on a runway beam supported by either the building columns or columns specifically engineered for the crane. The top running overhead crane or bridge crane is the most common crane configuration with the feature that the crane loads are transmitted to the supporting columns or free standing structure and with the advantage of minimum head room and maximum height of lift.

Classification of top running overhead cranes

Top running overhead cranes can be further classified into single girder, double girder, and box girder overhead crane or bridge crane in terms of girder types. Single girder overhead crane or bridge crane is consisted of two end trucks, trolley hoist unit and a single bridge girder, on the bottom flange of which the trolley runs on. Single girder overhead crane designed for your application can be cost-effective. Single girder overhead crane has lower wheel loads so that it will save on new support structures and it will also allow you to add more lifting capabilities to your runway structure without upgrading. Double girder overhead crane or bridge crane is consisted of two end trucks, trolley hoist unit and two bridge girders, on the top of which located the rails on which the trolley runs. Double girder overhead crane provides better hook height for the hoist of the double girder overhead crane is mounted on top of the bridge rather than underneath. Box girder overhead crane or bridge crane is a crane equipped on a girder formed by multiple walls in the shape of enclosed tube, rather than on an I-beam or H-beam. Box girder overhead crane is used for heavy duty material handling with the feature of extremely rigidity and durability.

Under running overhead cranes

Under-running or under-hung overhead crane or bridge crane has the end trucks ride on the bottom flange of the runway, which is usually suspended from the roof, with no need of extra floor columns for the support of the runway. The under-running or under-hung overhead crane has the advantage of taking no floor space and saving cost for supporting system. Moreover, an under-running or under-hung overhead crane can be applied to the sloped ceilings or multiple crane systems.

Classification of under-running or under-hang overhead crane

In terms of crane girder, the under-running or under-hang overhead cranes can be grouped into single girder, double girder and box girder overhead cranes. Single girder under running overhead crane provides you a cost effective material handling solution for it can save new support structure because of its reduced wheel loads, which also makes it possible to add more lifting capabilities without upgradation. Double girder under running overhead crane is usually used for handling loads over 25 tons, which is usually provided with a complete material handling solution. Double girder cranes provides a higher lifting height for the crane hook travels between the beams, comparing with that of the single girder overhead crane.

Overhead crane comparison -top running Vs. under running
To choose the top running or under running overhead crane is mainly determined by two factors:

Capacity: Even though the under running overhead crane can be up to 25 ton capacity, the practical limit is more like 15 tons. Support structure: Under running overhead crane can be suspended directly from the overhead steel for the lighter duty crane. Top running overhead cranes needs a bracket off the building support steel (up to 10 tons capacity) or independent columns for larger capacities. Top running overhead crane configuration is best used when headroom is an issue. Double girder top running configuration is the most space efficient one. Whereas when the headroom is not an issue a top or under running configuration can be either single girder or double girder.