Unit 1 MATERIAL HANDLING EQUIPMENT Structure 1.1.
Introduction
1.2.
Objectives
1.3.
Selection of materials handling devices
1.4.
Types of materials handling equipment
1.5.
Conveying equipment (conveyors)
1.6.
Traction Type Conveyors
1.7.
Escalators
1.8.
Tractionless-Type Conveyors
1.9.
Hoisting Equipment
1.10.
Hoisting machines
1.11.
Elevators
1.12.
Transport equipment
1.13.
Non-powered equipment
1.14.
Containers of Supports
1.15.
Bulk handling equipment
1.16.
Feeding equipment
1.17.
Handling of construction materials
1.18.
Warehousing equipment.
1.19.
Bulk Transport Equipment (Hauling Equipment)
1.20.
Dump trucks
1.21.
Summary
1.22.
Keywords
1.23.
Exercise
1.1.
Introduction
Need of the present day is for the equipments to handle heavyloads with fast speed, reliability, safety and economy. In order tomeet the variety of requirements, equipments of different types andsizes have been developed and are being manufactured. Applicationof material handling devices is a prime consideration in designingnew plants and for modifying existing plants. These devices increaseoutput, improve quality, speed up the deliveries and therefore,decrease the cost of production. Utility of these devices have furtherbeen increased due to increase in labour costs and problems relatedto labour management. Materials handling equipment are mechanically, electrically,
hydraulically or
pneumatically operated or uses their combination.Materials handling equipment are not production machinery. Theseare auxiliary equipments which improve the flow of materials whichin turn reduce stoppages in production machines and thus increasetheir production.
1.2.
Objectives
After studying this unit we are able to understand
1.3.
Selection of Material Handling Devices Material handling devices, should be able to give maximumefficiency, economy, life and
reliability of service. Under-utilisation and faulty selection of the materials handling equipment is anexpensive luxury which gives rise to increase in operating costs. The equipment selected should be according to the requirement of thejob in respect to the size, shape, weight, material to be handled etc. According to George Hageman, the important "Engineering andEconomic" factors to be considered in every materials handlinginstallation can be classified as: • Factors relating to the plant and operating methods. • Factors depending on materials or parts handled. • Factors relating to the handling equipment. • Money factors. Factors relating to the Plant and Operating Methods • Are the present manufacturing or operating method permanent or temporary? • How long will the present buildings remain in service? • Is the general plant layout the beat for manufacturing and handling requirements?
• Is the sequence of operations that which gives greatest efficiency? • What processes and departments must be tied together? • If trucks or floor types of equipment are to be used, are aislesand passage ways ample for conveniences in handlingspeed, safety and non-interference with production? Arethe floors made of water-resistant materials? Are they leveled and smooth? Will they withstand the loads? • If overhead systems are contemplated, is the buildingstructure strong enough to hold them and are clearances sufficient for their installation? Factors Depending on the Materials or Parts Handled • Kinds or nature of materials or parts handled. • Bulk or units • Large or small • Heavy or light • Shape • Rough or fragile. • Handled separately or in containers • Quantities handled • Continuous or intermittent flow • Under processing while moving • Distances over which transported. Factors Relating to the Handling Equipment • Kind or kinds suitable for the job. • Capacity of equipment. • Hours it will be in service daily. • Size of equipment. • Space required for operation (For trucks this factor covers, aisles, passage ways, elevators, platform sizes etc.) • Flexibility (According to loads etc.) • Adaptability to other service. • Power requirements. • Ease of operation.
• Speed of operation. • Durability. • Relationship to other handling equipment in use or contemplated. • Auxiliary equipment which is required, and economical toinstall loading platforms, etc. Money Factors • Initial cost of equipment • Cost of installation, re-arrangement, and alterations topresent equipment, buildings etc. • Cost of maintenance, repairs, supplies etc. • Cost of power. • Rate of depreciation. • Rate of obsolescence. • Probable salvage value when finally discarded. • Cost of labour to operate • Cost of any necessary auxiliary equipment (such ancharging equipment for truck batteries, etc.) • Taxes and Insurance. • Interest on Investment. • License fees (for trucks that may operate on highways). • Rent of space (also garage rent for trucks). • Cost of supervision. • Savings that the equipment will bring about in direct labour cost (number of men released for other work). • Saving in labour burden (supervision etc.) • Increased production brought about. • Savings in fixed charges on equipment discarded. • Unamortized value of equipment discarded.
1.4.
Types of Material Handling Equipments
1. Conveying Equipment: These follow horizontal, vertical or compound motions through the air, over fixed routes by gravity or by power. Conveying equipment is a group of machines which move loads in a continuous flow and which may have no lifting gear.
2. Transportation and Transferring Equipment: (a)Transportation Equipment: These follow horizontal motion overfixed or variable, level or nearly level routes by pulling or pushingon surface riding vehicles. (b) Transferring Equipment: These followhorizontal, inclined or declined motions through the air over fixedroutes or limited areas, with intermittent motions. Transportation equipment may be (a) Surface transportationequipment and (b) overhead transportation equipment. Surfacetransportation equipment is a group which are equipped withrunning gear that remains in contact with surface over which itmoves. These normally operate over horizontal path of travel.Overhead transportation equipment is a group of machines whichusually handle loads in batches and which may not be providedlifting gear. 3. Hoisting equipment (Lifting, lowering or elevatingequipment): (a) Lifting and lowering equipment: These are usedin the operation of lifting a load, handling them in suspension,lowering and placing them at required locations. (b) ElevatingEquipment: Vertical motion over fixed vertical or steepy inclinedroutes with continuous or intermittent motion is followed by these equipments. Hoisting equipment is a group of machines with liftinggear intended for moving loads mainly in batches. Since materials handling equipment are used for moving loads in premises, departments, factories and plants, at construction sites, storage and reloading points etc. they move loads over comparatively short distances. These generally depend on theavailable external and intra-plant transporting facilities, externaltransporting facilities, supply the enterprise writh raw materials, semi-finished items, fuels, auxiliary materials etc. and dispatch theready production and wastes from the enterprise. Intra-planttransporting facilities distribute the loads, which come in, throughout the enterprise. For important loading and unloading operations some handlingmechanisms are provided with special grabbing devices operated byauxiliary machine and appliances or manually.
1.5.
Conveying Equipment (Conveyors) Conveyors of different types and sizes are available inproduction, mining, and
construction industry. It is possible to startand stop conveyors, interrupting the flow of materials whenrequired. Materials can be diverted, transferred, raised or lowered,loaded or unloaded by means of conveyors at one or more locations.Conveyors may be portable or fixed. Limitation of
fixed or stationaryconveyor is that, once installed, it is almost inflexible regardingalteration in location, shape capacity etc. These are suitable fordirect routes at high capacity rates, and can be placed at floor levelor elevated above the worker's heads or other operational levels, tosave valuable floor space. Conveyors do not necessarily require an operator. These arereliable in operation and have minimum downtime, requires veryless time for preventive maintenance. These can be used to handlelarge variety of materials including different types of packages, loosematerials, bulk materials etc. If the path for the flow of material is fixed then the provision ofthe conveyors at suitable levels eliminate a good deal of lifting andlowering of materials. Conveyors require no stopping or startingbut is continuous in operation. In these, transportation is effectedby friction between materials being transported and the belt. Theseconveyors have the advantage that they largely save labour cost,but have disadvantage that they take up considerable space, arerelatively fixed and in most cases the investment cost is high.Conveyors may be used for horizontal, vertical (also known aselevators) or inclined conveying of materials. Conveying machinery is intended to move loads in a continuousstream without stops for loading and unloading. Bulk materials arehandled by these machinery in a continuous or intermittent flow,and unit loads can be moved in piecemeal. Conveying operationsfollow a standard pattern so that conveyors lend themselves toautomation more rapidly than cranes. Performance of the conveyor can be known by its capacity, whichis the volume or mass of a load moved per unit time. Capacity ofconveyor is, Q=wV where, Q =Capacity of conveyor in tons/hr, V =Volumetric capacity of conveyor in m3/hr. and
w = Bulk weight i.e., mass per unit volume of material.
1.6.
Traction Type Conveyors
1. Belt Conveyors Belt conveyors are the most common form of materials handlingsystem used in manufacturing and mining industry, thermal plantsand in construction projects.
Heavy industries like steel, fertilizer, chemical and cement etc. cannot function without the belt conveyors. In construction projectsthe belt conveyors are used for handling the materials in AsphaltPlants, Crushing and Screening Plants, Aggregate-mixing plantsetc. In coal mining and other mining industries these are used for handling of coal or other raw materials. The belt conveyors arecapable of conveying large quantities of materials continuously overconsiderably long distances at a fast speed. For transporting the material for short distance conveyor maybe a portable or a fixed unit. When a belt conveyor system is usedto transport materials for a considerable distance, upto several kilometres in some cases,' the system consists of a number of flights.Each flight is complete conveyor unit discharging its load onto thetail end of the successive unit. Belts used in the system are costly and perishable item andhence need to be carefully maintained. The belts are generally madeof rubber covered cotton or rayon laid up in plies. The strength ofa rubber belt depends on number of plies. Canvas plies, woven wire mesh and steel belts are also used depending upon the strengthrequired for the conveyors to convey various types of materials, theirtemperature, quantity to be transported etc. Belts are specified bywidth, number of plies, and weight of each layer of ply. Belt conveyors consist of a belt running over drums or pulleysprovided at the end and are supported at intervals by a series ofrollers known as idlers. These idlers are supported on the conveyorframe, and help to support the conveyors and reduce the sag of thebelt and prevent the loose material from spilling. These idlers arefree to move on bearings. Since 1000 to 1200 idlers per kilometerof belt length are provided, it is important to design, select andmaintain for maximum life and to give best performance. Selectionof proper bearings with minimum friction value, standardisation, strict quality control and proper finish/tolerance of shafting isessential. The dust proof bearings packed with lubricant with efficient seals, require no further attention for years. The spacing of idlers depend upon the weight of the material handled, if the idlers are widely spaced, the sag between them becomes excessive,which will result in wastage of power, increase in belt wear, chances for spillage of material due to impact at each idlers. Advantages Following are the main advantages of belt conveyors: • It is capable of handling light or heavy, fine or coarse, wetor dry material. • It can handle, thousands of tons of material per hour forseveral kms.
• It can handle hot materials upto160 C or so. • It is lighter in weight, and consumes less power. • It operates without noise. • It gives a continuous discharge and quantity of which canbe varied by varying the speed of conveyor belt. • It can carry the material horizontally or in an inclination. • It is used for carrying the material over rough country,where use of other means is difficult and costly. Belt Conveyor Components Following are the main components in a belt conveyor system: (i) Belt: Rubber belt is the costliest single component in thesystem. Conveyor belt consists of a carcass imbedded in rubber. Thecarcass is made up of plies or layers of fabric (cotton or synthetic)bonded together and carries tension and absorbs impact. The rubbercompound maybenatural,syntheticora blend Steel-wire strandedcables are now-a-days also used in place of fabric yarn in carcass to have higher tensile strength. Vulcanizingor mechanicalfasteners are used to make the conveyor belts endless at the job site.Mechanical fasteners are also used for quick repairs of cuts and ripsin conveyor belting in an emergency. (ii) Pulleys and Idlers: Pulleys are generally located at theterminals of a belt conveyors, where they support the belt andtransmit driving power The conveyor belts are supported on idlers,between the terminals. The idlers are generally of the three-rolltype, with the center roll horizontal and the two-side rolls inclinedto form a trough. This angle is generally kept at 20°. The idler rollsare made up of steel tubing, with welded end discs which hasantifriction bearings. The idler supporting the loaded strand of the belt is known as upper idler and the one which is supporting the return belt is called as lower idler. The upper idler are 3-roller type or single roller type,but lower idler always have single roller. The belt runs flat on a single roller, while takes the shape of a trough on multi-roller idlers.
Belt Conveyor
(iii) Drives: Nearly all belt conveyors are driven by electricmotors. Speed reduction may be achieved by chain and sprockets,'V' be Its or gearing. The drives are generally located at the dischargeends of inclined conveyors. (iv) Motors and Controls: Squirrel-cage and wound-rotortypemotors are commonly used in conveyors. The motor for a conveyorbelt drive must have sufficient torque to overcome the startingfriction of the system. Fig. above shows a belt conveyor, which consistof moving endless belt and carries materials within supportingframes. (v) Conveyor Belt Take-ups: Take-ups are provided to adjustthe increase in length of the belt due to its elongation after it is putinto operation. Take-ups are oftwo types: (a) Screw take-ups, whichare used to increase the length of the conveyor by moving the heador tail pulley. This system is used for short belts. (b)In anothersystem, weighted pullies are provided to createuniform tension inthe returning belt.
(vi) Hold Backs: Holdbacks are provided on the driving pulleyto prevent the load from causing the belt to run backward in theevent of a power failure, if the belt is operating on an incline.Hold backs are mechanical devices which allow the driving pulley torotate only in normal direction, and prevents it from rotating in theopposite direction. Types of Belt Conveyors (1) Flat Belt Conveyors Thisisan endless fabric, rubber, leather belt operating oversuitabledrive, tail end, bend terminals, and over belt idlers forhandling materials, packages, or objects placed directly upon thebelt. These belts are supported by flat rollersand .carry units,cartons, bags, boxes, bales etc. These belts run on flat tables (calledas slider belts) or on rollers. (2) Troughed Belt Conveyors These are the belt conveyors with the edges elevated on thecarrying run to form a trough supported on idlers or other surfaces.These are suitable for bulk materials. The material carrying capacity of the conveyor is controlled by the speed, width and depthof trough. Like flat belts these are also endless belts or vulcanised, or joined by belt fasteners at the site.
The trough is made by 3 or 5 roller pattern, the length anddiameter of rollers depends upon the capacity and type of material.The rollers are set at 20° to 30° to the horizontal. For larger volumeof material, deep troughed conveyor belts with rollers set at 50° to 70°
to
the
horizontal with nylon and polyester belts are used. (3) Portable Belt Conveyor These are ideal for quick, efficient, and economical loading ofloose and free flowing materials from heaps on the floor to the trucks.These are more productive and suitable for large production work. 2. Roller Conveyors (Gravity, and Live Rollers) This is used to transportvarious shapes of products such as boxes or materials, which extendover several rollers. This type consists of rollers supported in framesover which materials are allowed to move. They are driven by poweror gravity. These are of different varieties and can move materialsin horizontal direction as well as from the upper floor to lower flooretc. These have long life, readily assembled and installed, easy toadjust and used for handling large variety ofloads. Loads with rigidand smooth base are moved on the roller conveyors,.other items canbe moved after placing them on flat boards. Pitch of the rollers shouldbe such that minimum of 3 rollers must remain under load at alltimes. Spacing is generally kept at 8 cms, 10 cms or 15 cms. Rollers generally range from 2 cms to 8 cms in diameter withlength governed by load. The rollers are made of cylindrical tubing with a bearing on each end. Generally tapered rollers are providedat the turns. Roller conveyors are used for relatively short distances ascompared to belt conveyors. Roller conveyors using gravity are known as gravity roller conveyor,while those operated by power are known as powered roller (or live rollers) conveyors. In powered roller conveyors, power is applied to some or all of the rollers to propel the loads. In powered roller conveyors, the
power is generally applied by chain on sprockets. These are used for moving objects on level runs up slight grades (uptoabout 10°), or descent on downgrades (upto 17°). These are more expensive than gravity roller conveyors or belt conveyors but are more rugged than belt conveyors.
3. Chain Conveyors These are moved by chains or cables in horizontal direction and installed flush with floor or alittle above it. This is used for movingbarrels and heavy boxes. This is also used for moving grates of bigboilers. These serve as a continuous moving table. Chain conveyors employ continuous chains wrapped around head and tail end sprockets. The conveying units are generally operated by motor drives, attached to the head drive shaft. Materials can be carried directly on aprons or pushed in a trough by flights attached to the chain. The chain conveyors may be apron,flight, bucket, car conveyors depending upon the type of attachment it uses. The units can be arranged for operation horizontally, inclined or in combination. These can be designed to operate upto45° inclination. Capacity of a chain conveyor = available cross sectional area xchain speed. Speed ofthe chain depends upon the type of material, and variesfrom 3 to 6 m/min for abrasive material to about 30 metres per minor more for mildly abrasive materials. Chain conveyors can be used at elevated temperatures, canhandle coarsely broken material unsuitable for the belt conveyor;chain positively transmits the drive imparted to it by the sprocket,and displays low stretch ability under a load. Its numerous articulations require careful attention and regular lubrication.
4. Elevating Conveyors (Bucket Elevators) The elevating conveyors are used for transporting dry granular materials (the material that will not stick to the buckets) in thevertical direction with the help of buckets and trays. These are alsoknown as Bucket elevating conveyors or Bucket elevators and carry the material in bucket to vertical or near vertical positions. Theseare either (i) chain bucket elevator, in which buckets are attached to one or two chains which move on two end wheels, or (ii)Belt bucket elevator, in which buckets are attached to the belt moving on pulleys provided at two ends.
Bucket elevators are operated between head and foot terminal machinery in a supporting frame. The buckets are loaded by scoop action at foot end or by a chute above. Belt types have higher speedand capacity, smoother and quieter, while chain types are heavier duty and suitable for abrasive materials. Such elevators arc sometimes used as portable elevators which are known as stackers, consists of a base on wheels, a vertical frame or mast, a lifting or lowering mechanism, and a load carrying platform. Lifting of such elevators is accomplished by hydraulic or mechanical action. The mast may be telescopic or non-telescopic. Bucket elevators consists of an endless chain of buckets which elevates the materials. The elevators is usually enclosed in a sheet of metal casing with necessary inlet and outlet openings and chutes.These are widely used in handling coals, chemicals, cement etc. 5. Cage Elevators (Lifts) Cage elevators, also called lifts, are intended exclusively for vertical lifting of freight and passengers in a cage which moves on rigid guide rails. These are extensively used in industrial enterprises, dwelling houses, offices and departmental stores, Cage elevators are classified as freight or passenger lifts The type of drive employed classify them as electric, and hydraulic Electrically driven elevators are the most popular type Travel speed of freight elevators range from 0.1 to 1.6 m/scc, while passenger lifts travelat a speed of 0.5 to 3.5 m/sec.
Passenger lifts arc usually available in capacities of0.25 to 1.6tons, freight elevators can handle from 0.25 to 15 tons. Electric cage elevator comprises the following main parts: cageor car. self-supporting guide rails, shaft way. Counter weight, suspension gear, hoisting machine, safety devices and electriccontrols. 1.7.Escalators Escalators are specially adopted chain conveyors for the verticaltransportation of people. An escalator is an inclined conveyor withthe driving traction element in the form of steps 1, attached tostep-drive chain 2. These are used in undergrounds, departmentalstores, public places like, airports, busy railway stations, largeshopping mall etc. They operate at speeds between 0.5 and 1metre/sec. Escalators mainly consist of a stepped apron with two hauling chains, a drive, take-up supporting metal structure with guidetracks, entry stages, an enclosure with frame, hand rails, reduction units, brakes (service and safety) and couplings. Escalators are supplemented by a standby drive, which is less powerful and is usedduring inspection and repairs. Escalators are unidirectional and run continuously. Pair of escalators are necessary for two way service. In this, people enjoyservice, the moment they reach the landing. Starting, stopping orreversal should be done only by an attendant and with the assurance that no one is riding at that time.
1.8.Tractionless-Type Conveyors Sliding-friction gravity conveyors, chutes, screw or spiralconveyors, twin-helical conveyors, vibrating and oscillatingconveyors, hydraulic, pneumatic conveyors are the main conveyorsof this type. 1. Gravity-Type Conveyors This type of conveyors depend on gravitation to perform its function . The most simple are slides, chutes, and tubes arranged soas to enable the load to slide down. Gravity conveyors have long been known simply as chutes. In these, bulk or unit loads move ona declined surface or vertically under the force of gravity. The angle of inclination is determined by the coefficient of friction for the material of its surface and the material conveyed as well as by the angle of repose.
Gravity roller conveyor is a material handling installation inwhich the bed consists of rolls fitted to a frame. These are equally suitable for the handling of unit loads and containerized high volume materials. Smooth operation is obtained by spacing the rollers not more than 1/3 to 1/4 of the length of the load.
Rollers, which are at rest at the beginning of a conveying cycle,acquire circumferential speed changing from zero to the rated valueV, as shown in the Fig. below,due to load travelling over them.When the load has passed, the speed gradually decreases due tobearing friction and may become zero.
2. Chute This is one of the simplest device which has both vertical andhorizontal motion. These may either be straight or spiral. These gravity chute conveyors, large or small, curved or straight, are usedto move the materiel from higher level to a lower level. These are either in the form of flat-bottomed troughs or with troughs curved suitable for a particular type of load and are manufactured for aparticular type of load and are manufactured of steel, wood, plastic or lined with other materials and can handle loose items or packages.The number of different sizes and
weights of packages should be restricted, otherwise heavier packages will travel very fast while lighter ones will tend to come to rest. Spiral chutes are used when height is more in a given length.In this, load is lowered following a helical path around a verticalaxis. These are designed so that the outer edges is higher than theinner one, so as to protect the load being thrown off the chute by the centrifugal force set up during descent. A transverse gradient of 10 sup romanoto 15 sup romanois normal. Packages should always befed and discharged from a straight section ofthe chute. Spiral chutes has advantages of low price, no power requirement, low maintenance cost, economical use of space and controlled speed of descent.
3. Screw or Spiral Conveyors Screw conveyors, also known as auger conveyors, consist of ascrew rotating in a stationary trough or tube. As the shaft, on which screw type spiral blades are fitted, rotates, the spiral blade causes the material to be pushed forward along the trough. Screw conveyors can operate in a horizontal, inclined or even vertical upward direction. While the materials are being
moved, the screw conveyors can also be used to perform the process of blending and mixing materials. These are used to move materials over a trough by a rotating screw. This is formed by a helical blade attached to a drive shall which is coupled to a drive and supported by end bearings and
by
inner
bearings.
The
trough
of
the
round-bottom
shape
is
topped
by
a cover plate with an opening for loading the conveyor. A similar unloading opening is provided in the bottom of the trough. The helical blade forcing the load along the trough when the shaft is set rotating is made of 4 to 8 mm steel plate and attached to the shallby welding. Helical spiral blades are used for dry materials ranging in sizefrom powder to medium lumps. Ribbon spiral blades are used to handle coarsely-broken and sticky loads. Paddle spirals and cut flights are adopted to convey flow-resistant solids tending to cake. By virtue of their design ensuring gas-tightness, screw conveyors are widely used to handle dusty or hot loads and those which liberate harmful gases. Screw conveyors can be used for handling powders, food products, pulverised coal (for feeding intothe furnace) or other granular materials. For abrasive materials extra seals should be fitted to the screw shaft bearings.
Screw conveyors easily negotiate rising gradients and con also operate vertically, lifting material upto 15 m. For lifting the material vertically, the vertical conveyor is assisted by a screw feeder or a horizontal screw conveyor which serve to create a thrust at the foot of the lifting screw.
4. Conveying by Hydraulic Means In hydraulic transport installations, also called as hydraulic conveyors, bulk loads are carried in a pipe or trough by the stream of a liquid (usually water). The mixture of a material with water is called hydraulic mixture, pulp or slurry. In troughs, the pulp is moved by gravity and the trough must be declined in the direction of pulp motion. In pipes, the pulp can be carried by gravity or dueto the pressure of the liquid created by a pump. In the latter case,the material can also be transported horizontal or upwards. Hydraulic pumps and pipe lines are generally used for transportation of liquids like petroleum products, or materials likesilt, soil etc. removed for throwing out in the form of slurry, e.g., during construction of tunnels, digging of tube well etc. 5. Pneumatic Conveyors Free flowing light powdery materials like cement, fly-ash and minerals can be conveniently transported through an air tight pipeor duct by air stream of high velocity. This system is free from unhygienic dusty conditions and requires little maintenance, but can transport materials only in one direction. This is largely used for transporting dry, pulverized or granular materials, chemical powder, sand, cement etc. It can be operated by air pressure positive or negative (i.e. suction). The initial cost of this system is relatively high and the use is limited to selected materials. This system is cleaner, dust free, easy to install, requires lesser staff to handle or operate, and minimum interruption. Maintenance is also less since moving parts are not involved. This system is popular for handling cement on large scale construction works.
A system of vertical and horizontal pipes, which carry particles of solid materials by means of air pressure in the system, areclassified as: (i) Positive pressure system:In this system a blower creates the positive air flow in the pipeline, and materials are injected into theair stream and blown via the pre-set conveying path to a storagesilo or a process bin. (ii)Negative pressure (Vacuum) system: In this system, vacuumis created in the pipe line, a suitable intake mechanism with ahopper and a receiving station is provided where material particles are separated from the moving air stream by tangential or cyclonicaction and discharged to storage or process bins. (iii) Combination system:This employs both the positive and negative systems. In this system, vacuum is used for unloading of material from storage, thereafter positive pressure is used for distributing into single or multiple storage silos. Pneumatic conveyors can handle small metal parts of densities ranging between 1.2 to 4.0 tons/m sup 3. These are self-cleaning type, and are flexible i.e. easy to add to, change in length, operating procedure or layout. This requires minimum maintenance. This type of conveyor system is economical because of the (i)saving in the cost of bags and other packages, (ii) less expenses on bulk handling, (iii) less labour costs, (iv) no chances of damage, spillage or residual materials in the discarded bags. The factors determining the power requirements and the sizeof equipments are the vertical lift, horizontal pipe length, size ofmaterial to be transported and throughout required. A pneumatic conveying system consists of (a) air supply unit,(b) feeder unit, (c) pipelines, and (d) separation unit. Air supplyunit is generally consists of blower, gear box, and a motor. Feederunit is used to transfer the material into pipeline. These should beable to withstand the abrasion of the material to be transported. Pipe-line should be strong enough to suit the conveyed material and the pressure of the system. Separation unit, usually employed for separating the material at destination, is high efficiency cyclone separators. 6. Vibrating and Oscillating Conveyors In vibrating conveyor vibrations are created at high frequencyand small amplitude/while in oscillating conveyors frequency isrelatively lower and amplitude is larger. The vibrations are inducedelectrically or mechanically. These conveyors are rugged, require low maintenance.
These conveyors are generally used as afeeder, and for screening, blending or separating. These conveyorsare fitted with metal or plastic trough over which materials consisting of fragments of varying sizes are kept, which while moving are separated, larger ones travel at a higher speed than those of smaller ones. For designing a vibrating conveyor, it is essential to specify nature of material to be handled indicating density, g-m size andother characteristics. 1.9.
Hoisting Equipment Hoisting equipment is a group of machines withfor moving loads mainly in batches.
Hoisting equipment can be classified into following three groups: 1. Hoisting Machines: Hoisting machines are a groupofperiodic action devices designed as selflifting gear or for hoistingand moving loads, or else as independent mechanismof cranes andelevators. The hoisting mechanisms isgenerally required to facilitate other operations i.e., transport, assembly mounting on amachine tool. The jacks, pulleys hoists, special purpose monorail, winches, crane trolleys etc. are the main hoisting machines. 2. Cranes: Cranes are a combination of separate hoistingmechanism with a frame for 1ifting or both for lifting and movingloads which can be freely suspended on or secured to them. 3 Elevators: Elevators are a group of periodic-action machinesintended for raising loads or passengers in guideways. 1.10. Hoisting Machines Hoisting is the operation of lifting a load, handling them m suspension, and lowering and placing them at required locations. Hoists: Hoists are device for lifting or lowering the loads suspended from a hook on the end of retractable chains or cables. The loads are generally supported from overhead by a hook or travelling on a track. These devices are rugged, simple, dependable easy to install, versatile, and economical. Hoists have limitation of handling lesser loads, slow, manual operation, fixed path and require an overhead support. Hourly capacity of hoisting machines can be expressed by theformula: C = n.Q tons/hr. where, C = Hourly capacity of hoisting machines n= Number of machine cycles per hr. Q = Weight of live load, in tons. When handling unit loads Q = weight of 1 unit load whenhandling bulk materials.
Q = V. w. ϕ where,V = Capacity of grab, bucket etc. in cum. w= Weight of one unit volume of materials in tons/m3 ϕ = filling factor. 1. Jacks The jacks are simple lifting devices which are directly applied to the load to be lifted. They are commonly employed in repair and erection jobs to lift loads through a short distance, say 0.3 to 1.0 m.Jacks may be classified as: (a) Rack and Lever Jack (b) Rack and Pinion Jack
(c) Screw Jack: Screw Jack is an application of screw and offersthe greatest mechanical advantage of all the simple machines. It employs a screw spindle and nut. A detachable handle is used to rotate the screw spindle by means of a ratchet and pawl mechanism. Pitch (P) of the screw is the distance between two successive threads. It is the distance by which screw advances during onerevolution. When the lever arm (handle) of the screw is moved through one complete revolution, it traverses a circular distance equal to 2πl. Where l is the length of lever arm i.e. distance of point,where effort (E) is applied, from the centre line of the screw. During one revolution, weight W is lifted through a distance P. The relationship between E and W can be written as: Ex 2πl = W x P
Therefore, Mechanical Advantage = (d) Hydraulic Jack: Hydraulic Jacks work on the principle that, the pressureexerted by a liquid on a surface, is proportional to the area of the surface. Due to this principle, Jacks are capable of lifting greatweight. Surface pressure exerted by a liquid depends upon the ratioof face areas of the ram and plunger. Hydraulic jack works on the same principle as that of hydraulicpress. These are used to lift loads, and are commonly used or liftingautomobiles to facilitate cleaning and repair work. These are usedto lift heavy loads through a short distance.It is provided with plunger on one side. This plunger isreciprocated by a handle attached to it. Another side ofthejack isprovided with a ram, by means of which loads are lifted. Up and down motion ofthe handle reciprocates the plunger. This movement of the plunger draws the water (or oil) from the reservoir and delivers to the cylinder fitted with the lifting ram through the delivery valve. Both the suction and delivery valves are the non-return valves. Addition of high pressure water at the bottom of the ram causes it to move upward. Loads can be placed at thetop of the ram. Load is lowered with the help of a lowering screw. By unscrewing it, high pressure water from the bottom of the ram rushes to the reservoir, thus reducing the pressure of the water below the ram and causes the ram and hence the load to come down. Theoretical force on the ram = Force on the plunger x Ratio ofareas Actual force on the ram =Theoretical force x Efficiency Velocity ratio of Jack =
x Leverage
2. Pulleys A pulley is a small sheave or wheel with a grooved rim usually mounted on a pin on which it turns, a frame or block in which itruns and with a flexible rope or chain passing through the groove.A unit consisting of one or more sheaves mounted in a frame is known as 'block'. Block is mostly equipped with an eye, a hook or some similar device at one or both ends of the frame, by which objects can be attached. In pulley system, fixed or movable pulleys are connected in different combinations.
The system of pulley block is used for lifting loads through vertical distance and is most simple and inexpensive in cost. Thisis one of the oldest system of getting mechanical advantages. 3. Winch Winches are used to lift loads vertically by winding the rope or cable on a drum. These can be operated manually or by power to get a much greater mechanical advantage than that obtained with the help of a block and tackle (pulleysystem). It is frequently used in loading heavy equipment into ships,construction industry and in similar other jobs. Capacity of a winch can be increased by increasing the number of gear trains. These are very useful, simple and low cost equipmentfor lifting heavy loads. Ratchet brakes may be fitted on the winchto hold a suspended load and to prevent reverse travel of gears andthus provide safety against accidental dropping of load.
4. Power Hoist
Fig. shows a power hoist, which is often operated between fixed guide rails, for lifting things vertically. There is an infinite variety of hoists suitable for different purposes. The simplest is the chain hoist, which is operated by hand. There are also hoists operated by compressed air, diesel engine, or by electric power. The hoists are smaller to elevators except that, a hoist does not carry the operator in it, but is operated from one or two other points. Hoists used for short distance horizontal hauls are suspended from trolleys or carriers travelling over an overhead single rail track, commonly a rolled I-beam. In this case trollies are pushed by handfor capacity under 1 ton or they are fitted with hand-or mechanically operated drives. Electrical hoists capable of hoisting speeds between 5 and 25 m/min are available in capacities ranging between 0.25 and 15 tons. The speed of their travel over a single-rail track varies depending on the distance to be covered and the purpose the hoist serves.
5. Worm-Wheel Hoists In these hoists, worm-wheel arrangement is employed with two chains. These uses two chains, one is called the hand chain while the other as the load chain. The pull applied to the hand chain is transmitted to the load chain after being multiplied by the mechanical advantage. The worm is mounted on the shaft of load chain wheel and moves when this chain is pulled, while the wheelis provided with an extended hub to which two load sheaves are screwed. The load chain is received over these two sheaves and theload hook is secured to both ends of this chain. As the worm rotates the rotation is conveyed to the load sheaves through the wheel, and this raises or lowers the load depending upon the direction of pull of the hand chain.
1.11. Elevators (1) Hydraulic Elevators Fig. below shows a hydraulic type elevator, this is differentiated from hoists by the fact that the operator rides with the loud.Although there are different types of drives for such elevators, ingeneral the only important type is the electric one. Hydraulic elevators are now used only where it is dangerous to take the chancean electric spark, as in acetylene generator houses.
Recent developments in elevators have replaced conventional rope type ordinary elevators by Rack and Pinion type elevators. Earlier elevators (rope type) required, machinery room for housingthe machinery and could be used only after the complete building and the lift room have been made, which is a permanent installation. Present day elevators- rack and pinion type can stand on their own base and go upto18 metres without any support, and
hence can start working right from the very first day the work on the construction site starts. This can stop anywhere in between levelsor wherever we want to stop it, while conventional elevator stopsonly at predetermined levels. New elevator is simple, rugged andeasy to maintain. Using the same tower of this type of elevator,concrete skip can also be provided on the other side of the tower,which can run independently without disturbing the passenger cage. For very high structures like cooling towers, chimneys andT.V. towers, these can be made to travel even on inclined/curved surfaces, and cango upto a height of 600 meters. By using these elevators speed of work enhances considerably,and makes supervision easy which otherwise by climbing such aheight becomes difficult and making sufficient and satisfactorysupervision is almost impossible. Because of the above mentioned advantages, and saferoperation, as these stop smoothly in case of any fault in the system,the rack and pinion type elevator hoists are fast replacing the conventional rope type elevator hoists. (2) Bucket Elevators Refer earlier section on 'conveyors' in this chapter. (3) Monorails In this system, loads are suspended from wheeled carriers ortrollies that are rolled along an overhead track. The carrier wheelsgenerally roll along the top surface of the rail forming the track,whereas trollies are supported from or within an overhead trackand connected by an endless propelling medium such as chain orcable. These have low operating costs, require little maintenance,utilises overhead space releasing the floor space. The monorails are mostly used for point to point move followinga fixed path, handling through connecting buildings, handling ladlesfor pouring molten metals. These are suitable for low volume andlow speed handling. (4) Hydraulic Lift It consists of a cylinder and a ram: A platform or a cage is fittedat the top of the ram. Load or the persons are carried from one floorto another floor by means of these platforms or cages. Water underpressure enters the bottom of the cylinder and pushes the ramupward. Thus ram moves up along with a case, in which load andpersons may be there. In this type oflift (known as direct acting lift)stroke of the ram is equal to the lift of the cage. The cage
movesbetween guides and can be stayed at any level so that one can get in or out of the cage to the floor. For lowering it high pressure wateris gradually taken out. Direct acting lifts require deep wells for the ram and cylinder.To overcome this difficulty, modified form of hydraulic lifts fittedwith jigger are common. By providingjigger, these lifts require smallram and cylinder and thereby reduces the cost of construction. Thecage is suspended with the wire rope and gets its motion by means of a Jigger, in the same way as the hydraulic crane. Such type of lifts are commonly known as suspended type of lifts, and is shown in Fig. below.
Now-a-days electric lifts are very common and hydraulic liftsare not so common. But hydraulic lifts are very useful at the placeswhere electric supply is not available. · 1.12. Cranes Cranes have wide application in construction projects,industries, shipping etc. These are used for lifting the loads (maybe construction materials, loose materials, packages, containers,finished and semifinished products in industries etc.) and placing them at desired place. For this purpose the cranes have three motions in general, namely hoisting, derricking and slewing. cranes are generally electrically operated, diesel operated or may have diesel-electric drive. The cranes can be classified in following classes: • Derrick cranes. • Mobile cranes. • Hydraulic cranes.
The
• Overhead cranes, also known as Gantry cranes. • Traveller cranes. • Tower cranes. 1.13. Transport Equipment These are the devices which are used for horizontal motion. Transport equipment can be categorised into following categories: •Non-Powered Equipment. • Powered Equipment. • Supports and containers. 1. Non-Powered Equipment These are the equipment operated manually. Following aresome of the common nonpowered i.e. manually operated equipment. (1) Wheel Barrow: These
have
single
or
double
wheel
fitted
generally
in
the
front,
and
pushed by a man as shown in the Fig.
(2) Hand Trucks: The simplest transporting devices are wheel barrows and handtrucks. These are still in use by a number of small industries allover the country. Fig. below shows a Hand truck and a wheeler, used to carry material inside the shops.
All such equipments involve a large amount of manpower for are relatively small load. The chief advantages of this equipment is itsvery low cost, great flexibility and easy portability from one job toanother. (3) Box Trolley: Box trollies are used for transporting finished products.
(4) Platform Trolley: This is a small low platform type load carriers with one or more small rollers or wheels. These are used to carry low volumes forshort distances and variable paths and are suitable for large variety of loads. (5) Pallets: This is a horizontal platform used as a base of assembling, storing, and handling materials as a unit load.These are made ofwood, metals or plastic etc. and helps in protecting the goods fromdamage during handling. (6) Skids: These are shown in Fig. below and are used with lift trucks. Goodsmay be loaded into skids and then picked up with lift trucks. Theskid can be loaded as a unit and transferred from
position to position without subsequent loading and unloading. Both skids and palletsraise the load off the supporting surface and allow the easy insertion of the conveying means. Some materials are stored on dollies. This can be moved on their casters. Other material is stored on skids. The most common skids, which can be picked up in either direction, consistof a wooden platform and four steel legs. Skids are similar to the pallets, but are heavier and stronger,and are therefore suitable for heavier loads. These are not suitablefor stacking like pallets, due to having only one face.
2. Powered Equipment (1) Tractors and Trollies: These are one of the most common modes of horizontal transportation. Great flexibility is achieved as tractors can be usedto haul such a variety of different types of trailers. Trailers can belift-loaded and can be picked up by different tractors. This system has the advantage of great flexibility plus all the advantages of industrial railways and there is no investment in laying tracks. This is one of the most important methods of handling material inside the plant, or work area, and from one building to another.
(2) Trailers:
These are the load carrying platforms mounted on four or more wheels. These are towed by a prime mover, and steered either through turn table or through wheels. Two types of trailers are used namely, full trailers and half(semi) trailers Pull trailers, also known as wagons, are self-supported and are provided with a swiveling axle and a drawbar for connecting to the prime mover. Semi-trailers are supported on their own wheels only at the rear, while front end is supported on the prime mover. The semi-trailers have more maneuverability as compared to full trailers. The front end of the semi-trailers has a goose neck resting on the rear of the prime-mover(driving unit). The semi-trailers can be turned and operated in amore limited space than that needed for a truck or for a full trailer,this can turn up to 90° either to the right or to the left without moving forward. This is of more importance in tunnel work or on narrow mountain roads. It is suitable, where there are no steep grades.
(3) Narrow Gauge Rail Road: In general, little use is made of such equipment because it requires a heavy investment in the roadbed and tracks, has little flexibility and is difficult to change at a later date. These were usedin the days before the development of rubber-tired equipment. They are still found in metalworking industries (blast furnaces, copper refineries and steel-rolling operations) and in mining activities,where it is cheaper or more desirable to lay tracks than to pave theentire area. (4) Platform Lift Truck:
The lifting feature in lift trucks provide clearance in the floor to lift the skids and permits horizontal transportation. These are generally operated by battery or diesel engine. (5) Crane Truck:
Small crane trucks operate on the same principle aslift trucks. They are used for materials that cannot be put on skids,or not available for skids at the present time, or too much heavy to handle in the lift trucks. This moves quickly over smooth, even andhard ground. This can be carried at will and to any place. In these cranes, the solid rubber tyres are used. The cranes are rotary type, so that the load can be lifted from any position.
(6) Fork Lift Trucks: Auto trucks need no particular explanation except for the development of tail board called fork, which will receive the load atground level and elevate it hydraulically to the level of the ceiling heights, so that all manual lifting is avoided. When theload is to be shifted from one shop to another, fork trucks are used.These trucks do not require any extra man, and driver operatingthe truck can lift, carry, unload, stack, un-stack, lower the materials.S elf-loading and unloading can be earned out by providing a forkat the front end of the truck. Front attachment of the truck various with the type of load to be lifted and may consist of crane scoop, hydraulic clamp, hydraulic wood clamp, hydraulic pipe clamp or hydraulic bucket instead of the fork. Fork lift trucks ore widely used in workshops, stores and inconstruction works. These are used for handling cartons, boxes,crates, bag? etc. and by using various attachment they can also be utilised for timber handling including logs, heavy coils, sheet metal,large size tyres, drums etc. 1.14. Containers and Supports Based on unit load principle, material is kept in containers oron supports so as to handle them conveniently and economicallywithout any risk of damage etc. Some of the commonly usedcontainers and supports are described hereunder:
(1) Pallet Box: A box is constructed on a pallet The box is made from wood,sheet metal, wire mesh etc. depending upon its requirement i.e.permanent, detachable or collapsible. These help in easy inventory, easy handling of un-stackable material and minimises packing of individual items, easy storage and arc reusable. (2)
Skid Box: These are made of skids and are similar to pallet box.
(3)
Bulk container: Bulk container is used to transport material in bulk as a singleunit generally from 3 cum
to 6 cum capacity. These are especiallyuseful in handling powdered, granular or liquid material. Thesecontainers are made of metal, plastic, wood etc. depending upon thetype of material. These are transported on trucks or trailers. Sometimes these containers are made collapsible for ease during theirreturn when empty. These are very suitable for transportingmaterial which are likely to be affected by weather and there arechances of pilferage or contamination. (4) Shipping Container: These containers are designed to facilitate shipment ofmaterials or goods by large trailers, ships or air. Duringtransportation these are sealed to avoid pilferage andcontamination. This saves handling of individual item, reducespackaging and packing costs. 1.15. Bulk Handling Equipment Most manufacturing concerns producing powdered or granular materials, refineries, construction industry find it necessary totransport their materials; in some type of packages suitable for manual handling like drums, bags etc. but these are costly to provide, fill and handle. It is therefore become necessary to use forklift trucks, hopper bottom trucks, shipping containers,
tankers,trailers and transport them through road, rail road, air or sea. These transport equipment have already been discussed in earlier part ofthis chapter. For storage of these bulk materials silos, tanks, hoppers, etc.are used. Silos are common in storing very large quantities ofpowdered materials like cement etc. These are high steel and cement structures with circular cross -section. The material is delivered intothe top of the silo by an elevator or a conveyor. The material is removed from the silo from its conical bottom into a truck. A valveis fitted at the bottom of the silo to control the delivered quantity.
1.16. Feeding Equipment During processing in any industry, it is essential for effective and efficient performance to have a uniformly controlled feed.Uniform feeding operation and its control is obtained either by mechanical or electrical means. Mechanical feeders are generally offollowing types : • Adjustable feed opening. • Adjustable speed. • Vibratory. In order to control the feeding rate or to achieve the varying feeding requirements, mechanical feeders (generally hoppers) areequipped with provision of adjusting the gates at feed opening, orvariable speed drives. Selection of the type and size of the feeder depends upon capacity requirement, material characteristics and size, flow ability, moisture contents etc. Commonly used feeding arrangements are: (a) Belt Feeders: These ore the short belts and feeds the material at uniform rates. These are provided at the bottom of the hopper and extract the material from it. For varying the rate of discharge the speed of feed belt is varied as per requirement.
(b) Hoppers with Adjustable Gates and Chutes: These are used for feeding the material to the belt conveyors.These are used for uniform loading the running belt through a chute and rate of material flow is controlled through gates at the mouthof the chutes. These gates can be controlled either manually, or hydraulically or electrically or by means of compressed air chute isused to discharge the material on the conveyor belt in its direction of movement, so as to reduce the impact of material on belt. The size of the chute opening should be designed in such a way so as to avoid spillage of material from belt, and also avoid blockage of opening by lumpy material, if any. The inner walls of the chute should be lined with the anti-abrasive material. Toavoid the spillageof
material
and
guiding
the
material
on
belt,
two
rubber
pads
are
also provided on the sides at the loading point.
(c) Vibrating Feeders: When loading non-free flow materials, vibrating feeders areused. Vibrations are produced by electro-magnetic means or mechanical means. This feeding system is most suitable for almost all types of bulk materials: may it be dry or damp, hot or cold, orfine or coarse size grains. The vibrating mechanism is fitted eitheron the wall of the hopper above the chute or in case of rectangular container the device is fitted at the bottom plate to produce vibrations. 1.17.
Handling of Construction Materials
For bulk handling the construction materials, equipment usedare: • For aggregate, stones, sand, earth etc., dump trucks,dumpers etc. are used for transportation while loaders areused for loading into them. • For excavation, lifting and loading of materials back hoe,dragline, clamshells are used. • For transportation of cement, silos are used. • For transportation of bitumen, bitumen bowsers/tankerswith heating arrangement are used. • For transportation of cement concrete, transit mixers oragitating mixers are used.
• For transportation of cement and steels, trucks or trailersare used. 1.18. Ware-Housing Equipment Main function of the warehousing is the safe keeping of goods and provides overall control of the entire function. Over all control include economy, proper coordination of necessary activities,facilities and manpower. Activities involved in the warehousing are • Receiving. • Identification and sorting. • Dispatching to storage. • Placing in the storage. • Storage. • Order picking. • Order accumulation. • Packing. • Loading. • Shipping. • Record keeping and control. For mechanisation in a warehouse, above mentioned activities need be mechanised. For this purpose various factors are requiredto be considered to identify the activities for mechanisation and itsextent. The equipments should be selected out of a wide range tosuit these activities. Final selection of specific equipment is carried out after careful analysis of various factors as already discussed for selection of material handling equipment. Warehousing Activities and Commonly used Equipment Commonly used equipment for various warehousing activities are indicated below:
1.19. Bulk Transport Equipment (Hauling Equipment) These units transport the earth, aggregate, rock, ore, coals and other materials: Hauling units may be road vehicles or rail road locomotives. Haulage mainly consists of trailers pulled by tractorsor trucks. Trucks have high mobility and can haul various types ofmaterials. But their performance and output is greatly hampered on rough roads and in bad weather. For better performance, greater road maintenance with lesser grade is required. Whereas rubber tyred tractors with separate wagons have better mobility and haulage speeds on less maintained rough roads and can carry heavier loads than that of trucks. Crawler tractors with wagons are employed when roads are very rough and maintenance of roads isvery costly. These are used for short hauls due to low speeds.Locomotives are suitable for long distance haulage on a fixed route,which is likely to be continued for a long period. These can be usedin any weather, and rail road equipment require less maintenance. Road vehicles used for haulage works are of two types:
• On-highway vehicles. • Off-highway vehicles. On-highway vehicles are designed to be used on publichighways, whereas off-highway: vehicles are designed to be used onconstruction sites and mining areas, and are designed andmanufactured to preclude their use on public roads and thus theymay or may not comply with legal on-highway limitations. 1.20.
Dump trucks
Dump trucks are open vehicles which are capable of carryingand dumping earth, aggregate or other loose material to sites ofvarious projects such as dams, highways, ports etc. Generallyheavy-duty machines of more than 10 tonnes payload are intendedfor on-site haulage of construction or mine materials. Dump trucksin many sizes with pay loads ranging upto more than 300 tonnes are available. These may have two axle or three axle, and may be 4x 2 (2 wheels driven out of 4); 4 x 4 (all 4 wheels driven out of 4);6x4(4 wheels driven out of 6). Special features of dump trucks usually include: heavy dutyall-welded chassis to sustain rough ground conditions, extra largewheel and tyre to support load and give good ground clearance,
ultraheavy duty tipping
bodies
constructed
with
high
tensile
steel
to
withstand damage from high impart and highly abrasive materials. As mentioned earlier the dump trucks are of two types, namelyon-highway and offhighway. On-Highway Dump Trucks For a construction and mining project Dump truck is a very common and essential equipment and is available in various sizes and types. These on-highway dump trucks are generally classified by the volumetric or tonnage payload capacity. Generally dump trucks of capacities ranging between 3 to 25 cu m are commonly used with a speed upto 80 km per hour. However, dump trucks ofmore than 200 cu m (300 tonnes) capacity have also been manufactured. On-highway dump trucks have chassis, prime-mover and power transmission system similar to that of truck, whereas the body inthe dump truck is heavy duty type and is capable of tilting towards one side by means of hydraulic jacks and can be operated from thecabin On onhighway dump trucks, a tail gate is provided at therear so that while moving on the highway, the materials do not fellon the road. The tailgate opens when the body is doing the tipping operation
for dumping the material. The speed with which on-highway dump truck, travel is high and can be upto 80 km perhour or so depending upon the condition of the road.
Off-Highway Dump Trucks These are used off the highway specially in earth moving and mining applications. These are commonly known as Dumpers. The body construction is specially designed to absorb highimpact loading. The floor of the body is of high-tensile steel to reduce abrasion damage. The ratio of gross vehicle weight to horsepower is generally lower than for an on-highway dump truck. Top speed of off-highway dump truck is very slow (30-40 km per hour). Since these are used on rough roads, oversize air cleaners and filters, shockproof mounting of all instruments, dust-proofing of electrical system, cushioned mounting for radiators etc. are provided.
To satisfy a particular set of job requirements, an off-highwaydump truck can be selected out of various types available. Maintypes of off-highway dump trucks are: • Rear Dump trucks. • Bottom Dump trucks. • Side Dump trucks.
1.21. Summary In this unit we have studied Selection of materials handling devices Types of materials handling equipment Conveying equipment (conveyors) Traction Type Conveyors Cage Elevators, Escalators. Traction Type Conveyors Tractionless-Type Conveyors Hoisting Equipment Hoisting machines Elevators Transport equipment Non-powered equipment Containers of Supports Bulk handling equipment Feeding equipment Handling of construction materials Warehousing equipment. Bulk Transport Equipment (Hauling Equipment) Dump trucks
1.22. Keywords Hoisting Equipment Hoisting machines Elevators Transport equipment Non-powered equipment Containers of Supports
Bulk handling equipment Feeding equipment Warehousing equipment. Hauling Equipment Dump trucks
1.23. Exercise 1. Explain selection of material handling devices. 2. What are the different types of material handling equipments? Explain. 3. Write short notes on Conveying Equipment. List the different types. 4. Explain belt conveyors and its types. 5. Write notes on roller, chain and elevating conveyors. 6. Explain Cage elevators and escalators. 7. What are tractionless type conveyor? Explain a few types. 8. Write short notes on Pneumatic conveyors. 9. Elaborate on Hoisting equipment and machines. 10. Write short notes on Jacks and its types. 11. Write short notes on following: a) Pulleys, b) Winch, c) Worm- Wheel hoist and d) Power hoist. 12. What are the different types of Elevators? Explain. 13. Write a short notes on Transport Equipment and its types. 14. What are Containers and supports and their uses? 15. What are the different types of Feeding Equipment? Explain. 16. Write notes on Hauling Equipment. 17. What is Bulk Handling Equipment? How do you handle construction materials?
