Introduction Many kinds of cranes are used for lifting, shifting or laying load, equipment's or other materials. They may vary in dimensions, viz, shape, weight, function, design, etc. We use cranes to help us do these activities with ease. In general, they are divided into two categories:
Boom CranesThese differ from overhead cranes. In boom-type cranes, the rope of the hoist drops from the boom that can oscillate, incline and even telescope to the desired position. There are many types of boom cranes. In this article, we will discuss 3 kinds of Boom cranes.
Jib CranesThese cranes are used to move loads from one point to another either vertically and horizontally in a circumferential direction as per the length of the boom swing. The boom stretches out away from the vertical construction member. The boom is securely attached to the vertical structural member about 2/3rd of the way from the base. The stiff-leg bracing is fixed to the vertical structural member and rear of the boom that helps to support and strengthen the boom. The guy supports from the upper segment of the vertical arrangement member to the operational end of the boom and provides extra boom support.
Image source: https://en.wikipedia.org/wiki/Crane_(machine)#/media/File:Pedestal_Jib.jpg
The lifting device(hoist) is linked to the horizontal boom which slings from a trolley mounted block. The trolley mounted block glides along the boom length in forwarding or backward motion that helps to move the weight to any location within the span of the crane travel. The crane radius is controlled by the length of the boom, structural make-up of the vertical structural member and the workshop support plan. The jib crane radius can be 180°, 270° or 360°. The 360° radius swing is possible as there is no objection and is free to rotate a full circle radius and fulfill a large area. The 270° radius can swing as it has a facility support member. The crane radius of 180° swing is because of being attached to the structural member within the facility support wall. Most of the 180° swing cranes are installed after the original building construction to serve the shop area.
The jib crane's capacity varies on the design of the physical shape, structure size and boom length. The lifting volume should not surpass the boom's rated capacity which is given on the boom/device for easy reference. As a precaution, do study the capacity, control system and plan of the device and job to be performed.
Crawler cranesThese are fitted on caterpillar tracks which are operated by an engine and can move about are known as Crawler cranes. These are used for construction (Piping, precast, excavation) and heavy industry. These cranes are stable as the weight of the chassis and tracks helps it from tripping under load. The crawlers enable the crane to operate and function on all terrain and extremely rough ground. The booms are controlled by cables. They are usually controlled from a cabin containing many levers, each for certain functions. The levers direct the boom swing, lift, extension and selection of hoist. Some cranes also have extendable legs that help to increase the base of the crane while lifting a heavy load and adds to its steadiness. Most crawler cranes are equipped with a boom that can be extended or reduced according to necessity. The boom used with the crawler crane is called the "lattice boom". These are called as these are crisscrossed open work of metal structure members linking the upper and lower cords. The capacity of crane varies because of crawler chassis size and boom structural member size.
Image source: https://en.wikipedia.org/wiki/Crane_(machine)#/media/File:Crane_machine_slewing_platform.svg
The crawler crane is made up of a revolving unit and a traveling unit. These have 3 sets of machinery.
The revolving unit is built around a bed plate which carries the machinery frame. It carries the transmission and operation. The machinery is placed so that the entire revolving unit is balanced around the center of rotation. A counterweight is used by the Crawler to balance the lifting load and avoid the crane from tipping from a heavy load. The counterweights are often placed in pockets behind the engine or outside of the cab (The part that houses the operator and operation controls) to the rear of the deck in the revolving unit. Some crawler cranes can travel short distances with hanging load fastened to it but need to consult with the manufacturer's handbook before trying to travel with the overhanging load.
Automotive mobile cranesThese types of cranes have boom attached to a truck chassis. It can travel and ploy to the best hoisting position as per the job requirement. Most automotive cranes are four-wheel drive with extra-low gear range for journeying on soft or rough surfaces.
Image source: https://en.wikipedia.org/wiki/Mobile_crane
The operation of the Automotive mobile cranes or the truck crane's boom, turn-table and working area in a housing which also serves as counterweights when lifting loads. It uses outriggers to offer added support when lifting heavy loads. The outrigger prevents the crane from turning over while lifting loads to raised height are perpendicular to the truck chassis. Some Automotive mobile cranes or the truck cranes are supplied with lattice booms and some are fitted with hydraulic booms. The capacity of the Automotive mobile cranes or the truck cranes depends on the boom type, size and truck chassis. One should refer and consult with the manufacturer's handbook before trying any operation.
Lattice boomsThe lattice boom is a boom that looks like latticework i.e. the diagonal placement of members linking the lower and upper cords. A lattice boom consists of the following components:
The lattice booms are designed according to the crane type by the manufacturer. It should be used only with the specific type for which it is designed. The booms can be shortened or lengthened accordingly. When adding boom to adjust the required length, one must refer to the manufacture's handbook for the correct procedure. You can insert several booms for a high lift.
Hydraulic BoomsThe hydraulic boom uses hydraulic cylinders for boom movement and are manufactured in various lengths. It contains two to three extensions within its outer cylinder. The Hydraulic pressure powers the extension of the boom outward. The oil pump associated with the power drive unit provides the hydraulic pressure and force needed to extend the boom outwards. When lifting the full load, the hydraulic boom must be fully and carefully rigged with all wheels of the truck grounded.
I hope this article has cleared some of your doubts about the boom cranes that are normally used in construction companies and helped you to understand the different types of cranes, it's parts and its working.