CRANESREPORT

CONSTRUCTION EQUIPMENT

Heavy equipment refers to heavy-duty vehicles, specially designed for executing construction tasks, most frequently ones involving earthwork operations.

They are also known as heavy machines, heavy trucks, construction equipment, engineering equipment, heavy vehicles, or heavy hydraulics.

They usually comprise five equipment systems: implement, traction, structure, power train, control and information. Heavy equipment functions through the mechanical advantage of a simple machine, the ratio between input force applied and force exerted is

multiplied. Some equipment uses hydraulic drives as a primary source of motion.

CRANES

A crane is a type of machine, generally equipped with a hoist rope, wire ropes or chains, and sheaves, that can be used both to lift and lower materials and to move them horizontally.

It is mainly used for lifting heavy things and transporting them to other places. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of a human. Cranes are commonly employed in the transport industry for the loading and unloading of freight, in the construction industry for the

movement of materials and in the manufacturing industry for the assembling of heavy equipment. Cranes exist in an enormous variety of forms – each tailored to a specific use. Sometimes sizes range from the smallest jib cranes, used

inside workshops, to the tallest tower cranes, used for constructing high buildings. Mini-cranes are also used for constructing high buildings, in order to facilitate constructions by reaching tight spaces. Finally, we can find larger floating cranes, generally used to build oil rigs and salvage sunken ships.

Some lifting machines do not strictly fit the above definition of a crane, but are generally known as cranes, such as stacker cranes and loader cranes.

COMPONENTS OF CRANE

TYPES OF CRANES

1.MOBILE CRANES are widely used in construction since they are capable of moving freely around a job site. Rubber tired cranes are also capable of moving rapidly between construction projects. Crawler cranes have excellent local mobility but must be transported on equipment trailers between projects.

a. Crawlerb. Telescoping-boom truck mountedc. Lattice-boom truck mounted

d. Rough-terraine. All-terrainf. Heavy liftg. Modified cranes for heavy lifting

2. TOWER CRANES are widely used on building construction sites as well as on other construction projects requiring large vertical clearances and having restricted space in the work area. Such cranes are able to move loads over a wide area and have an almost unlimited vertical range.

a. Top slewingb. Bottom slewing

MOBILE CRANE

CRAWLER CRANE The full revolving superstructure of this type of unit is mounted on a pair of

continuous, parallel crawler tracks.

Vertical boom arrangement on a mobile crane

The crawlers provide the crane with good travel capability around the job site. Inclined lattice mast, which helps decrease compressive forces in the boom. Relocating a crawler crane between projects requires that it be transported by

truck, rail, or barge. These machines usually have lower Initial cost per rated lift· capability, compared with other mobile crane types is

low, but movement between jobs is more expensive. Therefore, crawler-type machines should be considered for projects requiring

long duration usage at a single site.

TELESCOPING-BOOM TRUCK-MOUNTED CRANE These truck-mounted cranes have a self-contained telescoping boom. Most of these units can travel on public highways between projects under their

own power with a minimum of dismantling. These machines, however, have higher initial cost per rated lift capability. For small jobs requiring crane utilization for a few hours to a couple of days,

a telescoping truck crane should be preferred. Telescoping-boom truck cranes have extendable outriggers for stability.

LATTICE-BOOM TRUCK-MOUNTED CRANE The lattice-boom truck crane has a fully revolving superstructure mounted

on a multi axle truck/carrier. The advantage of this machine is the lattice boom. The lattice-boom

structure is lightweight. This reduction in boom weight means additional lift capacity, as the machine

predominately handles hoist load and less weight of boom.

The lattice boom does take longer to assemble. The lightweight boom will give a less expensive lattice-boom machine the same hoisting capacity as a larger telescoping-boom unit. The disadvantage of these units is the time and effort required to disassemble

them for transport. In the case of the larger units, it may be necessary to remove the entire Superstructure.

ROUGH-TERRAIN CRANE These cranes are mounted on two-axle carriers These units have a lower cost. These units are equipped with unusually large wheels and closely spaced axles

to improve maneuverability at the job site. They further earn the right to their name by their high ground c1earence

allowance, as well as the ability of some models to move on slopes of up to 70%. Most units can travel on the highway but have maximum speeds of only about

30 mph. In the case of long moves between projects, they should be transported on

low-bed trailers.

ALL-TERRAIN CRANE Designed for long-distance highway travel. The carrier has all-axle drive and all-wheel steering, crab steering, large tires,

and high ground clearance. All-terrain cranes have dual cabs, a lower cab for fast highway travel, and a

superstructure cab that has both drive and crane controls. Most appropriate machine when multiple lifts are required at scattered project

sites or at multiple work locations on a single project.

It has a higher cost than an equivalent capacity telescoping truck crane or rough-terrain crane. All-terrain machine can be positioned on the project without the necessity of

having other construction equipment prepare a smooth travel way as truck cranes would require.

MODIFIED CRANES FOR HEAVY LIFTING These are basically systems that significantly increase the lift capacity of a

crawler crane. A crane's capacity is limited by one of two factors: (1) structural strength or

(2) tipping moment. Manufacturers have developed systems that provide the heavy lift capability

while maintaining machine integrity. The three principal systems available are:

o Trailing counterweighto Extendable counterweighto Ring systemo Guy Derrick

MECHANICAL PRINCPLESI. LIFTING CAPACITY

Lifting capacity depends upon:o Boom length Ao Radius of load Bo Counter weight Fo Weight of crane

o Boom angle C The tipping load is that load which produces Tipping condition at a specified radius. Load capacity will vary depending on the quadrant position of the boom

with respect to the machine's Undercarriageo Over the sideo Over the drive end of the trackso Over the idler end of the tracks

II. STABILITY

For stability, the sum of all moments about the base of the crane must be close to zero so that the crane does not overturn.

In practice, the magnitude of load that is permitted to be lifted (called the "rated load" in the US) is some value less than the load that will cause the crane to tip, thus providing a safety margin.

For stationary pedestal or kingpost mounted cranes, the moment created by the boom, jib, and load is resisted by the pedestal base or kingpost.

Stress within the base must be less than the yield stress of the material or the crane will fail.

TOWER CRANE

Tower cranes provide high lifting height and good working radius, while taking up a very limited area. These advantages are achieved at the expense of low lifting capacity and limited mobility, as compared to mobile cranes. The three common tower crane configurations are

o a special 'vertical boom arrangement ("tower attachment") on a mobile crane

o a mobile crane superstructure mounted atop a tower o a vertical tower with a jib.

Tower cranes are a modern form of balance crane that consist of the same basic parts. Fixed to the ground on a concrete slab (and sometimes attached to the sides of structures), tower cranes

often give the best combination of height and lifting capacity and are used in the construction of tall buildings. The base is then attached to the mast which gives the crane its height. Further the mast is attached to the

slewing unit (gear and motor) that allows the crane to rotate. On top of the slewing unit there are three main parts which are: the long horizontal jib (working arm), shorter

counter-jib, and the operator's cab. The long horizontal jib is the part of the crane that carries the load. The counter-jib carries a counterweight,

usually of concrete blocks, while the jib suspends the load to and from the center of the crane. The crane operator either sits in a cab at the top of the tower or controls the crane by radio remote control

from the ground. In the first case the operator's cab is most usually located at the top of the tower attached to the turntable, but can be mounted on the jib, or partway down the tower. The lifting hook is operated by the crane operator using electric motors to manipulate wire rope cables

through a system of sheaves. The hook is located on the long horizontal arm to lift the load which also contains its motor. A tower crane rotates on its axis before lowering the lifting hook. In order to hook and unhook the loads, the operator usually works in

conjunction with a signaller (known as a 'dogger', 'rigger' or 'swamper').They are most often in radio contact, and always use hand signals. The rigger or dogger directs the schedule of lifts for the crane, and is responsible for the safety of the rigging and loads.

PARTS OF TOWER CRANE

Mast: the main supporting tower of the crane. It is made of steel trussed sections that are connected together during installation. Slewing unit: the slewing unit sits at the top of the mast. This is the engine that

enables the crane to rotate.

Mobile crane superstructure mounted atop a tower

Operating cabin: the operating cabin sits just above the slewing unit. It contains the operating controls. Jib: the jib, or operating arm, extends horizontally from the crane. A "luffing" jib is able

to move up and down; a fixed jib has a rolling trolley that runs along the underside to move goods horizontally. Hook: the hook (or hooks) is used to connect the material to the crane. It hangs at the

end of thick steel cables that run along the jib to the motor. Weights: Large concrete counterweights are mounted toward the rear of the mast, to

compensate for the weight of the goods lifted.

TOWER CRANE

TOP SLEWING TOWER CRANE(FIXED TOWER)

Vertical tower with a jib.

Top-slewing tower cranes have fixed towers and a swing circle mounted at the top, allowing only the jib, tower top, and the operator cabin to rotate. Top-slewing cranes require a longer duration to erect and dismantle,

but they can be erected virtually up to any height. These cranes are suitable for medium-to high-rise construction projects where they are needed for longer durations. The main parts of a typical top-slewing crane are undercarriage, mast, operator's cabin,

slewing ring, jib and counterjib. These cranes are usually of stationary type, resting on the concrete or structural steel foundations. In the travelling tower crane, modular concrete blocks are used in the base to provide stability. The crane travels on heavy wheeled bogies mounted on a wide-gauge rail track. The travelling tower crane provides better site coverage. For additional stability, counter-weights in the form of modular concrete blocks are also provided

in the counterjib of the crane. Top-slewing tower cranes have a mast (also called tower) with modular, lattice-type sections. The mast is erected with the help ofanother lifting device. The crane rises in height by addition of sections one by one. Tower cranes also have provision of telescopic climbing frame through which new sections arc

inserted and height of the crane is raised. Slewing ring provides the rotating mechanism of the crane and is located at the top of the mast

just below the boom. In the top-stewing tower crane, only the jib, tower top and operators cabin rotate.

.

BOTTOM SLEWING TOWER CRANE(SLEWING TOWER)

Bottom-stewing tower cranes have the swing circle located at the base, and both the tower and jib assembly rotate relative to the base. Bottom-stewing cranes have height limitations although they can be erected and

dismantled very quickly-the reason they are known to be self-erecting and fast-erecting. These are suitable for low-rise construction and for short-term assignments.

Bottom-slewing tower cranes also consist of undercarriage, stewing ring, stewing platform, mast and jib. It has a stewing ring located near the base and both the mast and the jib rotate relative to the base. Since virtually the entire crane rotates, anchoring the crane with some fixed support is not possible. Ibis is the reason for the shorter height of a bottom-stewing crane relative to a top-stewing crane.

SELECTION OF TOWER CRANES

Weight, dimension and lift radii of the heaviest loads Maximum free-standing height of the crane Maximum braced height of the crane Crane-climbing arrangement Weight of crane supported by the structure. Available headroom Area that must be reached Hoist speeds of the crane Length of cable the hoist drum can carry

OPERATION

I. MOBILE CRANES RIGGED WITH VERTICAL TOWERS

Crawler- and truck-mounted tower cranes use pinned jibs extending from special booms that are set vertically. A crawler-mounted tower crane can travel over firm, level ground after the tower is erected, but it has only limited ability to handle loads

while moving. A truck mounted tower crane must have its out riggers extended and down before the tower is raised. Therefore, it cannot travel with a load, and the tower must be dismantled before the crane can be relocated.

Recent models of truck-mounted tower cranes merge a bottom-slewing Tower crane with a mobile truck crane. The resulting crane provides excellent lifting height and outreach, as would a normal tower crane, and yet it is possible To erect and dismantle the crane in less than 15 min.

II. FIXED-BASE TOWER CRANES

The fixed-base-type crane, commonly of the top-slewing configuration. The tower is mounted on an engineered concrete mass foundation, either on

fixing angles or bolted to the concrete base A large crawler or mobile crane is used to erect the tower crane to its full

height; however, many of these tower cranes have the capability to independently increase their tower height by means of a climbing mechanism.

There is a vertical limit known as the maximum free-standing height to which fixed-base cranes can safely rise above a base, typically 200 ft for average-size top-slewing cranes, and up to 400 ft for the larger-size cranes.

To raise the tower above this limiting height, lateral bracing must be provided. Guy ropes may be used to brace tower cranes, but in the majority of cases the towers are tied to the structure being constructed using engineered steel brackets.

III. CLIMBING TOWER CRANE

Along with the externally braced tower crane, the climbing tower crane is a common choice of crane for high rise building construction; and is a lifting mechanism solution for buildings exceeding the maximum-braced height tower crane limit.

Structurally supported by the floors of the building that is being constructed, the crane climbs on special climbing collars that are fitted to the building‘s completed structural floors .

The weight of both the crane and the loads lifted is transmitted to the structure of the host building. The crane will have only a relatively short mast because it moves upward with vertical construction progress . The taller the mast, the less frequent the climbing procedure. The mechanism that enables the climbing of the tower crane is shown in the figures below. The mechanism comprises a hydraulic jack (iii) and a pair of interim supports (iv). The hydraulic jack is used for pushing the tower crane upwards.

This crane's main beam was broken due to an overload

Upon reaching the full stroke length of the jack, two interim supports are inserted to upkeep the tower crane, allowing the hydraulic jack to be retracted for the next push.

It should be noted that during climbing, all vertical supports to the tower crane are released, and the self-weight of the tower crane rests only on the hydraulic jack which is placed on one side of the tower crane mast.

It follows that there self-weight of the entire tower crane is supported only by one steel beam (ii), ie, the one in the near face in the above figure.

The load effects under this condition appear to be critical as demonstrated below.