Roof cranes or overhead cranes are a type of cranes that run on an elevated runway structure along the length of a factory and provide three axis hook motion (up/down, left/right and backward/ forward). These cranes have a lifting device called hoist, that's mounted on a trolley & moves horizontally across a bridge beam.
The bridge beams are connected to one or more horizontal girders, which are supported at either ends by the end trucks. The end trucks are attached in a right angle position to the girders and move on fixed runways. These cranes are either operated manually or electrically. Overhead cranes are available in a variety of specifications and used with a number of attachments to facilitate load lift.
Different variety of attachments can be added to the roof crane's hoist to handle varied lifting activities or positioning of different loads. These include C hook, Gripping lifters, Vacuum lifters, Sheet lifters, Pallet lifters, Magnet lifters, Slings or strap hoist and Drum turners.
Types of Roof Cranes :
Single Girder – These cranes have a single bridge beam attached to the runways and end trucks. Single girder supports a lifting mechanism or hoist that runs on the bottom flange of the bridge beam.
Double Girder - These cranes utilize two bridge beams set atop the runway end trucks. They incorporate a top running trolley hoist that moves along the two bridge beams on their own set of wheels
Box Girder - Also known as tubular girder that forms four sided configuration with multiple walls, rather than an I or H-beam.
Truss Girder – These are a type of roof crane designed with structurally reinforced bridge girders for greater span and loading capabilities.
Top Running – These types of roof cranes run on a rail or track, which is above the runway beam.
Under Hung – In this type, end trucks of the crane ride on the bottom flange of the runway beam.
Roof Cranes vs Forklifts :
Less Product Damage – Roof cranes cause minimal damage to the product in comparison to forklifts.
Cost Effective Use of Space – Forklifts can only stack products as high as the mast will elevate. However, roof cranes allow greater hook height and more efficient use of space.
Less Labor – One roof crane can replace multiple forklifts in terms of efficiency.
Less Maintenance – Forklifts need to be replaced after few years of their use, but roof cranes can be used for a long period of time with minimal maintenance.