Introduction It is a common fact that we find a wide variety of construction machines on every construction sites, which make the construction jobs easy, safe and quicker. Good project management in construction must vigorously pursue the efficient utilization of labor, material and equipment. The use of new equipment and innovative methods has made possible wholesale changes in construction technologies in recent decades. The selection of the appropriate type and size of construction equipment often affects the required amount of time and effort and thus the jobsite productivity of a project. These act as a backbone in the case of huge construction projects. Proper use of the appropriate equipment contributes to economy, quality, safety, speed and timely completion of a project. Equipments are use for highway projects, irrigation, buildings, power projects etc. Almost 15-30% of total project cost has been accounted towards equipment and machinery. It is therefore important for site managers and construction planners to be familiar with the characteristics of the major types of equipment most commonly used in construction. Advantages of utilizing the construction equipments: Increase the rate of output through work progress with the best effective and efficient methods. Reduce the overall construction costs especially for large contracts. Carry out activities which cannot be done manually or to do them more economically and much faster. Eliminate the heavy manual work by human thus reducing fatigue and eliminates various other hazards and health issues. Maintain the planned rate of production where there is a shortage of skilled or unskilled labor. Maintain the high quality standards often required by present-day design and specifications (technical standards).
CLASSIFICATION OF CONSTRUCTION EQUIPMENTS Depending on the application, construction machines are classified into various categories which we are discussing here. 1. Earth-moving equipment 2. Earth-compacting equipment 3. Hauling equipment 4. Hoisting equipment 5. Conveying equipment 6. Aggregate production equipment 7. Equipments used in Concrete Construction. 8. Pile-driving equipment
EARTH-MOVING EQUIPMENTS SELECTION CRITERIA FOR EARTHWORK EQUIPMENTS The selection of earthmoving equipment is mainly dependent on the following factors: Quantities of material to be moved The available time to complete the work the job conditions The prevailing soil types, the swell and compaction factors, etc. The job conditions include factors such as availability of loading and dumping area, accessibility of site, traffic flows and weather conditions at site. In order to plan the number of Earthwork Equipment needed, the planner first determines the following: The suitable class of equipment for earthwork-for example, if the soil to be excavated is loose and marshy, and bulk excavation is involved In the project, one may opt for a dragline. The appropriate model of equipment based on different characteristics such as payload of bucket and speeds required. For example, draglines come in different capacities ranging from 0.38 cum to 3.06 cum; scrapers in capacities ranging from 8 cum to 50 cum and so on. The number of equipment needed for the project to carry out the given quantity. The number of associated equipment required to support the main equipment
1. Excavators Excavators are heavy construction equipment consisting of a boom, stick, bucket and cab on a rotating platform (known as the "house"). The house sits atop an undercarriage with tracks or wheels. Excavators are also called diggers Excavators are used in many ways: a. Digging of trenches, holes, foundations b. Material handling c. Brush cutting with hydraulic attachments d. Forestry work e. Demolition f. General grading/landscaping g. Heavy lift, e.g. lifting and placing of pipes h. Mining, especially, but not only open-pit mining i. River dredging j. Driving piles, in conjunction with a pile driver
2. Back hoe Backhoes are mainly used to clean up construction areas, to dig holes in the ground, to smooth uneven ground, to make trenches, ditches and to help remove deep roots from trees. It can exert high tooth pressures and hence can excavate stiff material which normally cannot be excavated by dragline. Out put of hoe is greatest when the excavation is done near the machine, because cycle time of operation reduces. A backhoe, also called a rear actor or back actor, is a piece of excavating equipment or digger consisting of a digging bucket on the end of a two-part articulated arm. They are typically mounted on the back of a tractor or front loader. Also known as hoe, back shovel and pull shovel It is used to excavate below the natural surface on which it rests. Generally used to excavate trenches, pits for basements and also for grading works, which requires precise control of depths. The basic parts are boom, Jack boom, Boom foot drum, Boom sheave, Stick sheave, Stick, Bucket and Bucket sheave.
The section of the arm closest to the vehicle is known as the boom, and the section which carries the bucket is known as the dipper or dipper stick (the terms "boom" and "dipper" having been used previously on steam shovels). The boom is attached to the vehicle through a pivot known as the kingpost, which allows the arm to slew left and right, usually through a total of around 200 degrees. Modern backhoes are powered by hydraulics. Applications: It is the most suitable machine for digging below the machine level, such as, trenches, footings, basements etc. It can be efficiently used to dress or trim the surface avoiding the use of manual effort for dressing the excavated the surface.
3. Front shovel A front shovel (also stripping shovel or power shovel or electric mining shovel or Dipper Shovel's power shovel) is a bucket-equipped machine, usually electrically powered, used for digging and loading earth or fragmented rock and for mineral extraction. They are mounted on crawler tracks. To excavate the earth and to load the trucks It is used to excavate earth of all classes except hard rock and load it into wagons. Size varies from 0.375m 3 to 5m 3. Basics parts of power shovel including the track system, cabin, cables, rack, stick, boom foot-pin, saddle block, boom, boom point sheaves and bucket. Power shovels are used principally for excavation and removal of overburden in opencut mining operations, though it may include loading of minerals, such as coal. They are the modern equivalent of steam shovels, and operate in a similar fashion. Front shovel are mainly used for excavation purposes above its own track or wheel level. They are suitable for heavy positive cutting in all types of dry soils.
Old Front Shovel New Front Shovel A shovel's work cycle, or digging cycle, consists of four phases: a. digging b. swinging c. dumping d. returning
Applications of Front Shovel: Suitable for close range of work Capable of digging very hard materials, can remove big sized boulders. It is used in various types of jobs such as digging in gravel banks, clay pits, digging cuts in road works, road-side berms, etc. Factors affecting output of power shovel Class of material Depth of cutting Angle of swing Job condition Management condition Size of hauling units Skill of the operator Physical condition of the shovel
4. Dragline They are used to excavate soft earth from below ground and to deposit or to load in wagons. Output of dragline is measured in Cubic Meters per hour. They are used for bulk excavation below its track level in loose soils, marshy land and areas containing water. The drag line is so name because of its prominent operation of dragging the bucket against the material to be dug. Unlike the shovel, it has a long light crane boom and the bucket is loosely attached to the boom through cables. Because of this construction, a dragline can dig and dump over larger distances than a shovel can do. Drag lines are useful for digging below its track level and handling softer materials. The basic parts of a drag line including the boom, hoist cable, drag cable, hoist chain, drag chain and bucket.
Applications of Dragline: It is the most suitable machine for dragging softer material and below its track level It is very useful for excavating trenches when the sides are permitted to establish their angle of repose without shoring. It has long reaches. It is mostly used in the excavation for canals and depositing on the embankment without hauling units.
5. Clamshell It consists of a hydraulically controlled bucket suspended from a lifting arm. It is mainly used for deep confined cutting in pits and trenches. It is having bucket of two halves which are hinged together at top. It is used to excavate soft to medium materials and loose materials. This is so named due to resemblance of its bucket to a clam which is like a shell-fish with hinged double shell. The front end is essentially a crane boom with a specially designed bucket loosely attached at the end through cables as in a drag line. The capacity of a clam shell bucket is usually given in cubic meters. The basic parts of clam shell bucket are the closing line, hoist line, sheaves, brackets, tagline, shell and hinge.
Applications of Clamshell: Used for handling loose material such as crushed stone, sand, gravel, coal etc. Main feature is vertical lifting of material from one location to another. Mainly used for removing material from coffer dam, sewer main holes, well foundations etc.
Comparison between different types of equipment Sr.no. Items of comparison Power shovel Back hoe Drag line Clam shell 1 Excavation in hard soil or rock Good Good Not good Poor 2 Excavation in wet soil or mud Poor Poor Modera tely good Moderately good 3 Distance between footing and digging Small Small Long Long 4 Loading efficiency Very good Good Modera tely good 5 Footing required Close to work Close to pit Fairly away from pit 6 Digging level Digs at or above footing level Digs below footing level 7 Cycle time Short Shortly more than power shovel Digs below footing level More than power shovel Precise but slow Fairly away from pit Digs at or below footing level More than the other equipment
6. Bulldozers A bulldozer is a crawler (continuous tracked tractor) equipped with a substantial metal plate (known as a blade) used to push large quantities of soil, sand, rubble, or other such material during construction or conversion work and typically equipped at the rear with a claw-like device (known as a ripper) to loosen densely-compacted materials. They are used for moving earth up to a distance of about 100m and act as a towing tractor and pusher to scraper machines. They can be track-mounted or wheel-mounted. The heavy blade attached to the tractor pushes the material from one place to another. The tractor can be of the crawler or the wheeled type. Classification of bull dozer 1. Position of blades Bull dozers in which the blade perpendicular to the direction of movement Angle dozers in which the blade is set at an angle with the direction of movement. 2. Based on mountings Wheel mounted Crawler mounted 3. Based on the control Cable controlled Hydraulically controlled
Applications 1. For spreading the earth fill 2. For opening up pilot roads through mountainous and rocky terrains. 3. Clearing construction sites. 4. Maintaining haul roads 5. Clearing land from the trees and stumps 6. back-filling trenches at construction sites by dragging the earth from one place to another
7. Scraper It is a device to scrap the ground & load it simultaneously, transport it over required distance. It can dig, load, haul and discharge the material in uniformly thick layers. In civil engineering, a wheel tractor-scraper is a piece of heavy equipment used for earthmoving. The rear part has a vertically moveable hopper (also known as the bowl) with a sharp horizontal front edge. The hopper can be hydraulically lowered and raised. When the hopper is lowered, the front edge cuts into the soil or clay like a plane and fills the hopper. When the hopper is full it is raised, and closed with a vertical blade (known as the apron). The scraper can transport its load to the fill area where the blade is raised, the back panel of the hopper, or the ejector, is hydraulically pushed forward and the load tumbles out. Then the empty scraper returns to the cut site and repeats the cycle. They are used for site levelling, loading, hauling over distances varying between 150m-900m. They may be towed, two-axle or three-axle type. Unique machine for digging and long-distance hauling of plough able materials. self-operating machine It is not dependent on other equipment. Wheels of machine cause some compaction. The basic parts of scrapers are the bowl, apron and tail gate or ejector.
8. Grader A grader, also commonly referred to as a road grader, a blade, a maintainer, or a motor grader, is a construction machine with a long blade used to create a flat surface. Typical models have three axles, with the engine and cab situated above the rear axles at one end of the vehicle and a third axle at the front end of the vehicle, with the blade in between. In civil engineering, the grader's purpose is to "finish grade" (refine, set precisely) the "rough grading" performed by heavy equipment or engineering vehicles such as scrapers and bulldozers. Graders are commonly used in the construction and maintenance of dirt roads and gravel roads. In the construction of paved roads they are used to prepare the base course to create a wide flat surface for the asphalt to be placed on. Graders are also used to set native soil foundation pads to finish grade prior to the construction of large buildings. It is used for grading and finishing the upper surface of the earthern formations and embankments. They usually operate in the forward direction It is self propelled or towed machine motor grader, Used for light or medium works. It shapes the ground and spreads the loose material..
9. Loaders A loader is a heavy equipment machine often used in construction, primarily used to lift material (such as asphalt, demolition debris, dirt, snow, feed, gravel, logs, raw minerals, recycled material, rock, sand, and woodchips) into or onto another type of machinery (such as a dump truck, conveyor belt, feed-hopper, or railcar). A bucket is attached to arms, capable of being raised, lowered and dumped through mechanical control. Application-Land filling, road Maintenance. Skid-Steer Loader: A skid loader or skid-steer loader is a small rigid frame, engine-powered machine with lift arms used to attach a wide variety of labor-saving tools or attachments. Though sometimes they are equipped with tracks, skid-steer loaders are typically four-wheel vehicles with the wheels mechanically locked in synchronization on each side, and the left-side drive wheels can be driven independently of the rightside drive wheels. Wheeled Loader
Crawler Loader The crawler loader combines the stability of the crawler tractor with the abilities of a wheel loader. However, to construct a reliable crawler loader it requires more than simply attaching a loader bucket onto a crawler tractor. It must be designed with its specific purpose in mind to ensure it has the strength to withstand heavy excavating. The introduction of hydraulic excavators diminished the market for the crawler loader because it was unable to match the excavator's lifting power and flexibility. However, crawler loaders are capable of maneuvering across the entire construction site under its own power, whereas most hydraulic excavators require towing or transport. While crawler tractors are still being manufactured today for niche markets, they reached their peak of popularity in the 1960s.
10. Trenching Machines Trenchers, or ditchers as they are sometimes called, are similar to excavators in the sense that they penetrate the earth, breaking soil and rock, and remove it from the ground. They differ from excavators in that the soil is removed in one continuous movement. Trenchers are specifically used for digging trenches for pipes, but other machines have been improvised in the past to serve this purpose. Trenchers can come in two types: ladder trenchers and wheel trenchers, and can dig trenches at speeds that other machines cannot compare to. Used for excavating trenches for laying pipelines, sewer, cables etc. Operation is quick giving the required depth or width. Two types of trenching machine are wheel type and ladder type
11. Tractors Multi-purpose machines used mainly for pulling and pushing the other equipment. Important Equipment for earthmoving, worked by Diesel engines, having horse power ranging from 20HP to 200HP. Tractors may be classified as a) Crawler type tractor- Used to move bull dozers, scrapers. The crawler has a chain by which these tractors can be very effective even in the case of loose or muddy soils. The speed of this type dose not exceed 12 kmph normally. b) Wheel type tractor- The engine is mounted on four wheels. The main advantage is higher speed, sometimes exceeding 50 kmph it is used for long-distance hauling and good roads.
Comparison between crawler and wheeled tractors Crawler type Wheeled type 1. Slow speed 1. Greater speed 2. More compact and powerful and can handle heavier jobs 2. Con handle only lighter jobs 3. costly 3. cheaper 4. Cost of operation and maintenance is high 4. Operational and maintenance cost is less 5. Stick control for steering 5. Wheel steering control 6. Moves on rough roads only 6. Moves on rough as well as good roads 7. Used for short distances 7.Used for longer distances 8. Requires skillful operation, maintenance and repairs 8. Lesser skills required for operations, maintenance and repairs
EARTH COMPACTION EQUIPMENTS Compactors are machines frequently used to compact materials such as soil in order to increase its density for construction. 1. In addition, compactors are utilized in landfill tasks. 2. Common varieties are plate tampers (also known as rammers) 3. Vibratory plates, compactors (also known as tamping foot rollers) & 4. Vibratory pad foot compactors. These categories are further divided below. 1. Smooth-wheel rollers These are most suitable for compacting gravels, sand and such like materials. Examples are Three wheeled or macadam rollers and tandem rollers. Plain steel rollers Self-propelled type Weighing from 5 to 15 tonnes Used for ordinary rolling work where deep compaction is not required These rollers may have one front and two rear wheels The rear wheels being usually larger in diameter and the front one being winder. Weight of rollers may be increased by filling water or sand ballast in hollow cylinder. These rollers are effective in compacting granular soils, such as sand, gravel and crushed stone.
2. Sheep-foot rollers It consist steel cylindrical drum with projection extending radial direction outward from surface of cylinder & may be propelled or towed by tractor. It is suitable for silty & clay sand, medium and heavy clay. For compacting earth work in embankments and canals (where compaction deep into the layer of the earth is required) These gives best result in compaction when the soil is clay or predominantly cohesive and impervious. The sheep foot rollers may weigh upto 15 tonnes or more Travel at a speed of 25 kmph As roller moves over the surface, the feet penetrate the soil to produce a kneading action and a pressure to mix and compact the soil from bottom to top layer. With repeated passages of the roller, the penetration of feet decreases.
3. Pneumatic-tyred rollers It gives kneading action as well as compression to the soil underneath. It is suitable for moderately cohesive silty soils, clayey soils, gravelly and clen sand. It consists of a base or a platform mounted between two axles. The rear of which has one more wheel than the front. Most suitable for compacting fine-grained soil and well graded sands. Ballasting is done using water, sand or pig iron in order to increase the self weight. Major advantages are the ability to control the ground contact pressure by: a) Altering the weights of machines, b) Increasing the number of wheels, c) Increasing the tyre width d) Changing the contact area of the tyre by altering the contact pressure.
HAULING EQUIPMENTS The equipment used for transportation of material are known as hauling equipment or simply haulers. Haulers may operate on the roadways or railways It involve transportation of building materials, carriage and disposal of excavated earth Haulage of heavy construction equipment. Haulage by road is carried out by trucks, rubber tyred tractor with wagons or crawler tractor with wagons. It transports the earth, aggregate, rock, ore, coal and other materials. Road vehicles used for haulage on construction work are two types. 1. On Highway Vehicle-Design to be used on Public Highways 2. Off Highway Vehicle-Designed to be used construction sites & designed and manufactured to preclude there use on their use on public roads and they may or may not comply highway limitation.
1. Truck They have high mobility, good speed and adoptability. The truck capacity varies from 0.4 Cum to 20 Cum & speed vary from 10kmph to30 kmph.
2. Dump Truck These are the trucks which are fitted with automatic unloading devices. The loading is normally done by loading shovels or loaders. The trucks have capacity as high as 53 tones. These trucks can be rear dump truck. These are used for earth moving purpose. The selection of the type of dump trucks for a specific job depend on the soil condition. (a) Side or rear dump trucks- These are heavy duty trucks with strongly built body which is hinged on the truck chassis at the rear end and one side respectively, and can be fitted to the rear in the case of rear dump and to the hinged side in case of the side dump, through the action of hydraulic jacks. These trucks are suitable for use in hauling wet clay, sand, gravel, quarry rocks etc. Side dump truck Rear dump truck
(b) Bottom dump trucks These are similar to semi-trailers in which their front is supported on the rear of the hauling tractor and their rear is resting on their own wheels. The body of the truck remains in the same position and the discharge of the material takes place through its bottom after opening of two longitudinal gates. The gates are hinged to the side of the body. These trucks are suitable for use in hauling free flowing material, such as, sand, gravel, dry earth, hard clay etc.
3. Dumpers A dumper is a vehicle designed for carrying bulk material, often on building sites. Dumpers are distinguished from dump trucks by configuration: a dumper is usually an open 4-wheeled vehicle with the load skip in front of the driver, while a dump truck has its cab in front of the load. The skip can tip to dump the load; this is where the name "dumper" comes from. They are normally diesel powered. A towing eye is fitted for secondary use as a site tractor. Modern dumpers have payloads of up to 10 tones and usually steer by articulating at the middle of the chassis. High speed pneumatic wheeled trucks 4. Short chassis 5. Strong bodies 6. Loading, hauling and dumping is done very fast as compared to other equipment 7. Suitable for short hauls on rough roads 8. Especially where a shuttle movement is required.
4. Tippers A truck or lorry the rear platform of which can be raised at the front end to enable the load to be discharged by gravity also called tip truck. Tippers are suited for the rough and tumble of mining & quarrying operations, as well as for carrying bulk loads in construction and infrastructure industries. Complete maneuverability, high performance and long-term endurance are common to all trucks, resulting in lower operating costs.
5. Ttrailers A trailer is generally an unpowered vehicle pulled by a powered vehicle. Commonly, the term trailer refers to such vehicles used for transport of goods and materials.
HOISTING EQUIPMENTS Hoisting is the lifting a weight from one location and moving it to another location which is at a reasonable distance. These equipments are used for lifting the loads, holding them in suspension during transfer from one place to other and placing them at designated location. Big projects such as, construction of dams, industrial buildings etc. require hoisting equipment. Hoisting equipment includes jacks, winches, chain hoists and cranes. Crane is the only single machine which, as a single piece, is capable of providing three-dimensional movement of a weight. It constitutes a group of equipment which are employed mainly for lifting or lowering of unit load and other. Forklifts A forklift truck (also called a lift truck, a fork truck, a forklift, or a tow-motor) is a powered industrial truck used to lift and transport materials. Forklift trucks are available in many variations and load capacities. In a typical warehouse setting most forklifts used have load capacities between one to five tons. Larger machines, up to 50 tons lift capacity are used for lifting heavier loads.
HOISTS A hoist is a device used for lifting or lowering a load by means of a drum or liftwheel around which rope or chain wraps. It may be manually operated, electrically or pneumatically driven and may use chain, fiber or wire rope as its lifting medium. The load is attached to the hoist by means of a lifting hook Also known as a Man-Lift, Buck hoist, temporary elevator, builder hoist, passenger hoist or construction elevator, this type of hoist is commonly used on large scale construction projects, such as high-rise buildings or major hospitals. There are many other uses for the construction elevator. Many other industries use the buckhoist for full time operations. The purpose is being to carry personnel, materials, and equipment quickly between the ground and higher floors, or between floors in the middle of a structure.
a. Boom Hoist Boom hoists are used to lift weights on the hooks that are attached to the special metal ropes designed to bear maximum loads. Boom hoist is mostly used as industrial machine where it loads the weight on containers. b. Chain Hoist Chain hoists are quite common example of hoist system and it can be seen at most of the construction and industrial purposes. Basically, chain hoist consists of chain rope and pulley that is used to move the load from up to down.
c. Electric Hoist Electric hoist is modernized form of chain and boom hoist mostly used in the industries for fast working. It is very much popular in material handling industries because it saves labor costs by handling maximum loads at a time with no damage threats. Electric hoist is modernized form of chain and boom hoist mostly used in the industries for fast working. It is very much popular in material handling industries because it saves labor costs by handling maximum loads at a time with no damage threats.
d. Tractor Hoist Tractor hoist consist of a boom that is attached with base of tractor and a hook with rope is installed on this boom that can operated through driver controls. CRANES A crane is a type of machine, generally equipped with a hoist, 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 man. 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 are considered to be one of the most important equipment used in construction due to their key role in performing lifting tasks all over the construction site. Plenty of crane models are available in different shapes and sizes.
SELECTION OF CRANES Factors affecting the selection of cranes are 1. Building Design Building Height Project Duration 2. Capability Power Supply Load lifting frequency Operators Visibility 3. Safety Initial Planning and Engineering 1. Derrick cranes- Derrick cranes consist of a mast, a boom and a bull wheel on which the boom rotates about a vertical axis and guys or supporting members. Preferable for high-rise and apartment buildings. Can be used for both long term and short term projects. Cheaper than mobile and tower cranes. Not considered to be safe. Used when clearance is inadequate for the other units and sufficient space is unavailable for the erection of a tower foundation. Electrically operated, diesel operated or diesel-electrically operated. The boom can revolve through 360º. This crane is used for heavy loads upto 200 tons.
2. Mobile cranes- These cranes are mounted on mobile units which is either crawler type or wheel type Truck cranes have high mobility while the crawler mounted cranes move slowly. Crawler mounted cranes are capable of moving on rough terrain. Adequate for all types of structures (up to 107 m) Used for shorter projects duration (less than 4 months). Not considered to be very safe due to lack of safety devices or limited switches to prevent overloading. Can operate in muddy terrain but requires good ground conditions. Needs adequate operating clearance.
3. Overhead or gantry cranes- large service area, freedom from floor obstructions and three-way mobility, Widely used in erection, foundry, steel plants, storage yards and different types of industrial works. These type of cranes consist of two main parts i.e., the bridge and the crab. The bridge consists of two main girders fixed at their end to end and capable of moving on gantry rails. The crab consists of the hoisting gear mounted on a frame. The frame itself is mounted on another set of wheels and capable of travelling across the main girder. 4. Traveler cranes Travelling or bridge cranes have their crabs moving on girders which are supported on legs instead of on overhead gantry track as used in overhead cranes. The legs are capable of moving on tracks laid on the floor.
5. Tower cranes Tower cranes are actually a derrick crane mounted on a steel tower. Tower cranes are usually used for industrial and residential high-rise buildings. These are commonly used for assembly of industrial plants with steel structures. The main parts of tower crane are under carriage, slewing platform, tower with operator s cabin and jibs. The tower has a truss structure welded from steel bars and channels. Preferable for high-rise (over 107 m). Used for longer project duration. Considered to be very safe due to the presence of limit switches. Can operate where ground conditions are poor. Does not need adequate operating clearance.
CONVEYING EQUIPMENTS A conveyor system is a common piece of mechanical handling equipment that moves materials from one location to another. Conveyors are especially useful in applications involving the transportation of heavy or bulky materials. Conveyor systems allow quick and efficient transportation for a wide variety of materials, which make them very popular in the material handling and packaging industries Transporting material from one place to another over a stationary structure. Caries material in continuous stream with its distinct feature such as endless chain or belt. Can be done horizontally, vertically or inclined. When the equipment does horizontal conveying, it is known as conveyor and when it does vertical, it is known as elevator. Conveying are mainly used in mining, construction and in some of the industries. In construction industry, conveyors are mainly used for concreting purpose. Utility The Advantage of using conveyors are as follows:- It increases the output. It facilitates continuity in operation. It results in time saving. There are no waiting periods.
1. Belt conveyor Used when large quantities of materials have to be conveyed over long distances at fast speed. It consists of a belt running over a pair of end drums or pulleys and supported at regular intervals by a series of rollers called idlers. These idlers are supported on a conveyor frame. The middle sag provided in the belt prevents the spilling of material. Generally, rubber is most commonly used as conveyor belt. The advantages of using belt conveyor are as follows:- 1. It can handle light as well as heavy materials, dry or wet, fine or coarse etc. 2. It can and for distances to convey several thousand tons of material per hour and for distances of distances of several kilometers. 3. It can carry material horizontally or inclined. 4. It is lighter in weight then other conveyors. 5. It gives controlled discharge of material and discharge can be controlled by the speed of the belt.
2. Screw conveyor Widely used for handling granular or pulverized material. The quantity of material conveyed is less compared to the conveyor, but at the same time the cost is also less. A screw conveyor consists of a helix mounted on a bearing at the ends and at intermediate points and is driven by a motor from one end. The material enters the through at one end is carried to the other end by screwing action of helix. The length of the conveyor is about 65m. with an inclination up to a maximum of 350.
3. Bucket conveyor It has buckets in the shape of V which are open at the top. They may be feeder loaded or may drag in a vertical movement or along an incline. The length of these type of conveyors are generally limited to 25 m. (due to weight of the conveyor and strength of the chains.) This type of conveyer is mainly used in coal handling where bucket elevators carry the material vertically.
4. Aerial transport Aerial transportation through cableways, rope-ways and tram ways Often used with advantage for transportation of material in hilly regions. Reducing the distance of transportation as well as cost of transportation The load being passed over intermediate towers or stations for long distances.
Aggregate production equipment Aggregate has to be produced at the site, if the quantity needed is very large. Therefore, in any project where concrete requirement is very high, an aggregate preparation and processing plant is essential to complete the concreting operations. Aggregate production consists of two stages is recovery and processing. Basic material, such as stone, is recovered from a rock quarry or from the river bed and processing is done which consists of crushing, grading, washing and stock piling of aggregate. Crushers are used mainly to reduce the size of large stone or rock to smaller uniform sized aggregates required for concrete mix. Crushing consists of Pressure, Impact, Attrition A combination of these operations. 1. Jaw crushers It is one of the primary crushers. It operates by allowing stone to flow into the space between two jaws, one of which is stationary and other is movable, which together constitute the crushing surfaces. The distance between the two jaws decreases as the stone travels downward under the effect of gravity and ultimately passes through the lower opening. The moveable jaw is capable of exerting a pressure sufficiently high to crush the hardest rock. The movable jaw is suspended from a shaft mounted on bearings on the crusher frame.
The jaw plates are made of manganese steel which can be removed, replaced or reversed. 2. Gyratory crusher This is another type of primary crusher. This type of crusher comprises a hardened steel head has a long conical shape, with a trough shaft suspended in a bearing at the top, and an eccentric base connection connected to gears. Thus, as the cone is rotated, the gap between itself and the walling changes from a maximum to minimum for each cycle. The rock is feed into the chamber at the top and as it moves downward, crushing is done and finally emerges through the bottom gap. The size of this type of crusher is the width of the receiving opening measured between the concaves and the crushers head. It is available in sizes varying from 20cm to 200cm.
3. Cone crusher Cone crusher are used as a secondary or tertiary crusher. These crusher are capable of producing large quantities of uniformly fine crushed stone. It has a shorter cone with smaller inlet and outlet openings as compared to the gyratory crusher. 4. Roll crusher Roll crushers are also one of the secondary or tertiary crushers. This crusher consists of a heavy cast iron frame equipped with two counter rotating rollers mounted on a separate horizontal shaft. The crushed rock from the primary crusher is feed through the gap between the two rollers for crushing further. Usually one roller has a fixed axis while the other can be adjusted to give the required setting.
The crusher is compact, light weight and low in cost. 5. Hammer mill Hammer mill is one of the impact crushers mostly used as primary or secondary crusher. It consists of a housing frame, a horizontal shaft extending through the frame, number of frames and hammers attached to the frame and one more hard steel breaker plates. As the stone is feed to the mill, the hammers, which are driven by a motor, move at the high speed and brake the stone into pieces and driving them against the hard plate, further reduce their size.
6. Rod mill and ball mill These are the tertiary crushers. A rod mill consists of a circular steel shell. The interior of the shell is lined on the inside with a hard material wearing surface. The shell contains a number of steel rods. The length of these rod is slightly less then the length of the shell. Crushed stone is feed through the inlet and fine aggregate of the size of sand is discharged at the other end. If the rods are replaced by steel balls to provide the impact required the grind the stones, the crusher are known as the ball mill crusher. The size of the balls generally used is 50 mm dia. Size.
CONCRETING EQUIPMENTS They are mainly used for weighing and mixing large quantity of concrete constituents. capacity:- 20cum/hr-250cum/hr Concrete is basically cement, aggregate & water mixed together and then deposited and permitted to solidify. Operation involved in concrete production batching, mixing, handling and transportation, placing, finishing curing. In huge concreting concrete and quality depends on time of mixing, so mixers are used. 1. Concrete production plants For mixing different ingredients in required proportion. It consists of storage bins for storing materials like cement and admixtures. Aggregate is mix in it with the help of a hopper which is fixed in plant.
2. Concrete mixers A concrete mixer (also commonly called a cement mixer) is a device that homogeneously combines cement, aggregate such as sand or gravel, and water to form concrete. A typical concrete mixer uses a revolving drum to mix the components. For smaller volume works portable concrete mixers are often used so that the concrete can be made at the construction site, giving the workers ample time to use the concrete before it hardens. Special concrete transport trucks (in transit mixers) are made to transport and mix concrete up to the construction site. They can be charged with dry materials and water, with the mixing occurring during transport. With this process, the material has already been mixing. The concrete mixing transport truck maintains the material's liquid state through agitation, or turning of the drum, until delivery. They are mainly used for mixing small quantities of concrete constituents. Capacity:- 200lt/batch (small mixers) 200-750l/batch (large mixers)
3. Concrete transit mixers They are mainly used for transporting concrete from batching point. capacity:- 3cum- 9cum 4. Concrete pumps They are used for horizontal and vertical transportation of large volumes of concrete in short duration. capacity:- 30cum/hr (ordinary construction) 120cum/hr(specialized construction)
5. Vibrator For compacting the concrete after its placement concrete vibrator is used. It help volume of concrete quickly placed, give high density, reduce air voids. Types of Vibrators Internal vibrators-use on large work for flat slab. External or form vibrators-uses for thin section of walls. Surface vibrator-used to finish concrete surface such as bridge floor, road slab, section platform. Table Vibrator-used for consolidation of precast units.
Needle Vibrator Surface Vibrator Table Vibrator
SELECTION CRITERIA FOR CONCRETING EQUIPMENTS Selection of concreting equipment can be complicated and difficult. The decision will involve many issues that have to be analysed. The following factors are noteworthy: Site characteristics such as boundary conditions, noise limitations and other restrictions. Equipment availability-local availability of equipments, whether the contractor owns that equipment Continuity of operation Effect of permanent work Weather conditions Temporary works Time restrictions Concrete specifications Concrete-mixing equipment selection will depend on factors such as the Maximum and the total output required in a given time frame Method of transporting the mixed concrete Requirement of discharge height of the mixer. Concrete-placement equipment selection depends on factors such as the Capacity of the vehicle Output of the vehicle Site characteristics Weather conditions Rental costs and the temporary haul roads.
Pile driving equipment The process of pile driving involves lifting the piles into position, holding it to refusal or to a specified depth. Driving is accomplished through hammering the pile top with a hammer. Equipment are so designed for driven effectively at an economical cost. Major pile driving equipment are: Pile driving rigs Pile driving hammers