WIRE ROPES Presented by Prof. Devidas S. Nimaje Assistant ProfessorDepartment of Mining Engineering National Institute of Technology Rourkela-769008, INDIA
Wire ropes are made from steel wires of plain carbon steel havinghigh tensile strength.Typical analysis of steel is as follows (by weight percentage):Carbon – 0.5Silicon – 0.11Manganese – 0.48Sulphur – 0.033Phosphorous – 0.014 andIron – restAccording to I.S. Specification no. 1835 of 1961, neither sulphurnor phosphorous content in the steel for wire rope should exceed0.080 %.Ultimate tensile strength (breaking strength) of the wires used forhaulage/winding ropes is generally between 140 – 170 kgf/mm2 2 2
Ropes of stainless steel are not used as the material has less tensilestrength.If the wire rope is to be used in a wet shaft, the wires aregalvanized, i.e. coated with molten zinc.The wire is subjected to the following tests carried out accordingto the standards provided by I.S. specifications:1.Tensile test2.Torsion test3.Bending test4.Wrapping test5.Looping test
Types and construction of wire ropes:On the basis of use, wire ropes are classified as:Standing RopesRequired to carry the burden or load but are more or lessstationary. i. e. guide ropes, track ropes etc.Running Ropes:Undergo frequent movement, running or coiling often withvarying loads and are flexible e. g. ropes used for winding,haulage coal cutting machine etc.
On the basis of construction, wire ropes are classified as: Stranded ropes: are made of strands and each strand consists of number of concentrically twisted wires laid in the form of helix round a central steel wire. Non-stranded ropes: They include locked coil ropes.
The flexibility of a strand depends upon:1.Type of core- a strand with a flexible core is more flexible thanone with steel core at the centre.2.Thickness of individual wires – Thinner the wires, more is theflexibility. and3.Number of wires- Larger the number of wires, more is theflexibility.
Lay of wire rope:The lay of a wire rope describes the manner in which either the wiresin a strand, or the strands in the rope, are laid in a helix.Left and right hand lay:Left hand lay or right hand lay describe the manner in which thestrands are laid to form the rope. To determine the lay of strands inthe rope, a viewer looks at the rope as it points away from them. Ifthe strands appear to turn in a clockwise direction, or like a right-hand thread, as the strands progress away from the viewer, the ropehas a right hand lay. If the strands appear to turn in an anti-clockwisedirection, or like a left-hand thread, as the strands progress awayfrom the viewer, the rope has a left hand lay.
The lay of wires in each strand is in the oppositeOrdinary lay direction to the lay of the strands that form the rope. The lay of wires in each strand is in the sameLangs lay direction as the lay of the strands that form the rope. Strands alternate between Langs lay andAlternate lay ordinary lay; e.g.: in a 6-strand wire, 3 strands are ordinary lay, and 3 are Langs lay.Regular lay Alternate term for ordinary lay.Reverse lay Alternate term for alternate lay.
The specification of a wire rope type – including the numberof wires per strand, the number of strands, and the lay of the rope– is documented using a commonly accepted coding system,consisting of a number of abbreviations.The rope 6x19 FC RH OL FSWR [where 6- Number of strandsthat make up the rope, 19 - Number of wires that make up eachstrand, FC- Fibre core, RH OL FSWR - Right hand Ordinary layFlexible steel wire rope].
Warrington differs from the other types (Filler Wire and Sealeconstruction) in that the outside layer of wires in each strand of thewire rope is composed of wires alternately large and small. Theoutside wires of both the Filler Wire and Seale construction ropesare uniform in size.The fundamental difference between these types is that the layer ofwires underneath the outside layer in the Seale type is made up ofwires all of the same size. The wires under the outside layer of theFiller Wire rope are made up of a combination of main wires, eachof the same size, and smaller filler wires, each of the same size,nested between the main wires. The outside layer of wires,therefore, is supported partly by the main inside wires and partlyby the filler wires.
Some ropes have shaped or formed (triangular) wires to improvethe wear and bearing properties of the outer layers (rather thancircular drawn wire.By having different lay directions of the strands and wire (leftand right - also known as S and Z); it is possible to balance thetorque value - resulting in a rope that does not tend to untwistwhen load is applied. This is called torque balanced or non-rotating rope.
Flat Rope:These are used for winding and are made with a flat construction. Itconsists of a number of small ropes or strands laid side by side andlaced or stitched together with soft iron wire. The individual wiresare laid up in opposite direction so that those of adjoining ropes testclosely together. For use with the flat rope, a special winder, knownas the reel winder is designed. This is arranged so that the flat ropewinds upon itself in concentric layers which are retained all thesides by radial arms or by side plates on the reel. By mounting tworeels upon the common shaft, a partly balanced system of windingcould be arranged. The effect is similar to that of a conical drumwith which the cage at greater depth i.e. the greater suspended load(including rope) is at smaller diameter. The development of circularstranded ropes, which are cheaper to manufacturer, more reliable inuse and easier to operate cause them to superside the flat rope andlead to the development of reel winders by drum
Advantages:1.Compared to the round stranded ropes, they are more flexible.2.They have been preferred as balancing ropes on the koepesystem of winding.Disadvantages:1.Wear in the rope lacing or stitching which holds the individualrope section together causes difficulty in operating flat ropeswhile repairs are slow and expensive.2.Their life is much shorter compared to the round strandedropes.
Round Wire Rope:The most important attribute for a winding rope is the ability towithstand, without permanent deformation, repeated bending understress such as when the rope is wound over the head sheave or onthe drum.This requires a construction which is flexible, which the constituentmembers are restrained in their respective positions. A constructionusing wires laid evenly in a helix about a central core has theseproperties and is able to yield under stress, returning to its originalform when the load is removed.
Advantages:1. Ability to withstand without permanent deformation repeated bending under stress.2. Flexible3. It returns to its original form when the load is removed.Disadvantages:1. Compared to the flat rope they are less flexible.2. Compared to the flat rope they have less strength.
Locked Coil Rope:They differ from standard ropes in construction and are made byspinning concentric layers of single wire around a core and finishingwith one or more surrounding layer of shaped wires which are interlocked to restrain, the centre layers and to make a smooth cover.Each layer of wires is spun in a helix about the centre core. Dependingupon the design one or more of the inner layers are made up ofalternate round and shaped or half locked wiresThe outer layers of fully inter locked wires is laid on in the oppositedirections to the inner layers with the result that the rope is almostnon-spinning. The cross section of the locked coil rope shows that thecentral portion consists of strands of thick round wires only the outerlayer (or two layers) consists of round wires placed between speciallyshaped wires of I section, rail section or trapezoidal so that the wireslock with one another and the rope surfaces is smooth and plain as
Cross-section of different wire ropes(First row: Flattened strand rope, Middle row: Locked coilrope and Bottom row: Spiral strands)
Advantages:1.It has a major advantage in sinking shafts where guide ropesare not available.2.For winding and hoisting purposes a locked coil rope issometimes preferred.3.It has capacity factor which permits a high factor of safety.4.Their smooth exterior causes less abrasion and wear of thesurface in contact. Hence it gives more durability.5.It has more space factor (75%). Hence greater strength.6.It has more tendencies to twist or rotate. It reduces wear on thecage guide.7.They are greater strength than the round rope because the wiresare more completely arranged.8.They are greater resistance to crushing.9.They have fewer tendencies to twist and stretch in working.
Disadvantages:1.Construction is somewhat difficult.2.Its interior cannot be lubricated from outside.3.It is not so flexible.4.It is somewhat difficult to cap as compared to the standard ropes.5.They do not stretch as much as the standard ropes and theirsmooth exterior cause less abrasion and wear of the surface incontact.6.They are not preferred for koepe winders because of smoothsurface and low coefficient of friction.
Precautions:1.Avoid use of the rope with fiber core, when the rope is subjected toheat flames and extreme pressure.2.Buy right construction of rope suitable for the job.3.Corrosion can be delayed by using galvanized rope.4.Do not load the rope beyond its safe working load.5.Ensure that the rope is strongly seized before it is cut.6.Flexibility of rope should be suitable to the size of the drums andpulleys and diameter of the rope grooves.7.Grease the rope and cover properly before storing in a dryventilated shed.8.Handle the rope carefully while transporting and uncoiling to avoidkinks.9.Inspect the rope periodically and lubricate with acid free lubricant.10.Judge the safe life of the rope for the conditions under which it hasto work and replace it in proper time.
Selection of wire ropes:A wire rope is to be selected on the following considerations:1.Watery place and corrosive atmosphere - to prevent rusting andeffect of corrosive fumes, a galvanized wire rope should be used insuch places.2.High temperature – ropes with fibre core should be avoided andin such places steel core should be used i.e. in foundries, steelmelting shops, etc.3.Stationary or running /coiling rope – stationary ropes can be oflarger diameter rods or strands e.g. guide ropes in a shaft. Running orcoiling ropes requires flexibility and smaller the drum/ pulley, moreis the flexibility required.
4. Spinning or rotating quality – in a crane rope, one end is free to rotate and a non-spinning rope or one with ordinary lay should be used. In a sinking shaft, the sinking bucket is not travelling on guides and therefore non-spinning rope of locked coil construction or a rope with ordinary lay should be used.5. Shock loads – when the rope has to withstand shock loads, a rope with steel core should be used e.g. coal cutting machine rope.6. Resistance to wear- Ropes for haulages and winders have to be flexible and resistance to abrasive wear. Such ropes should be of Lang’s lay construction as they offer more wearing surface.7. Tensile strength and factor of safety – ropes used for winding of men should have high tensile strength and high FOS than those used for winding of materials only. Ropes of Lang’s lay construction stretches under load more than the rope of regular lay construction.
8. Bending fatigue- Bending fatigue of a wire rope over sheaves or drums causes fatigue failure of the wires. The rope should be flexible which is possible in a rope having large number of smaller wires.9. Groove size – the rope should not be loose or too tight in the groove of the pulley or drum.10. Crushing and distortion – a flattened strand rope and locked coil rope is better able to withstand crushing than a round strand rope. The core should be of steel wire.Once the construction lay and other characteristics of the rope are decided upon, one has to decide its size after calculating the stresses that the rope may have to withstand.
Ropes used for different purposes:1.Winding ropes:6 x 7 Lang lay FC6 x 19 Seale regular or Lang lay FC6 x 21 Filler wire regular or Lang lay FC6 x 25 Filler wire regular or Lang lay FC6 x 27 Flattened strand Lang lay FC6 x 30 Flattened strand Lang lay FCLocked coil hoist rope2.Guide ropes:3.Half locked coil guide rope
3. Winding rope for shaft sinking:19 x 7 Non-rotating Regular lay or locked coil hoist rope.4. Haulage ropes:6 x 7 and 6 x 19 Seale construction in either Regular or Langs lay FC, depending upon operating conditions.5. Coal cutting machine ropes:6 x 37 Regular lay with IWRC or 6 x 31 Regular lay with IWRC.6. Dipper shovel ropes:• Dipper hoist ropes:For 32 mm and smaller size, 6 x 25Filler Lang lay with IWRCFor 35 mm to 68 mm size, 6 x 41 Seale Filler Lang lay with IWRC• Crowd and Retract ropes:For 58 mm and smaller size, 6 x 41 Seale Filler Lang lay with IWRC• Boom Hoist ropes:For 30 mm size, 6 x 25 Filler wire Lang lay with IWRC
7. Dragline Hoist ropes:For 32 mm to 58 mm size, 6 x 25 Filler wire Lang lay with IWRC or6 x 41 Seale Filler Lang lay with IWRC8. Dozers:6 x 25 Filler wire Regular lay with IWRC (Blade hoist ropes)9. Guy Ropes (ship masts- stability:Galvanised strand 1 x 7, 1x 19, 1 x 37 etc or 7 x 7 or 7 x 1910. Aerial ropeways:• Bi-cable ropeway:Track cable: Locked coil (Full or Half lock)Traction ropes: 22 mm and larger, 6 x 19 seale Lang Lay FC or 6 x25 Filler wire Lang lay with IWRC• Monocable ropeway:6 x7 Lang lay FC6 x 21 Filler wire Lang lay FC
11. Mobile Cranes: • Main Hoist rope: 6 x 25 Filler wire Regular lay with FC (use IWRC ropes to takecare of crushing of the rope on the drum) • Boom hoist rope: 6 x 25 Filler wire Regular lay with IWRC
Mass and strength of wire ropes:The mass of a rope depends upon the quantity of steel in it i.e. thespace factor and the design of the rope.Mass of rope (kg/m length) = kd2Where k is a constant depending on rope design and d is diameter ofrope in cmStrength (Breaking strength) (KN) = sd2Where k is a constant depending on rope design and quality of steeland d is diameter of rope in cm
Type of rope k sRound strand with fibre core 0.35 52Round strand with wire core 0.40 56Flattened strand with fibre core 0.41 55Flattened strand with wire core 0.45 58 Locked coil 0.56 85
Socketing or Capping a rope end:The end of a rope where the load is to be attached should be a goodportion of the rope, free from worn, rusted, bent or broken wiresand free from the effects of bending and corrosion.The simplest and easiest way to make the rope end suitable forattachment of load is to use a grooved thimble and bend back therope end on it and part of the rope before finally tightening 4-6rope clips at intervals on it. It needs less skill and such attachmentis permissible for haulage and skip hauling on inclined planes butnot permitted for winding ropes. Rope length under clips is nearly30 times the rope diameter.There are different ways of attaching capels or sockets1.Split capel with rivets2.Coned socket type capel3.Interlocking wedge type capel (Reliance capel)
Interlocking wedge type capel (Reliance capel)
TRANSPORT SYSTEM Presented by Presented by Prof. Devidas Nimaje Devidas S. S. Nimaje Assistant ProfessorDepartment of Mining Engineering National Institute of Technology Rourkela-769008, INDIA
The main methods of transport are as follows:A. Rope Haulage 1. Direct rope haulage a. Tail rope haulage 2. Endless rope haulage a. Over-rope b. Under-rope 3. Main and tail rope haulage 4. Gravity haulageB. Conveyor system of haulage 1. Belt conveyor 2. Cable belt conveyor
3. Chain conveyor a. Scraper chain conveyor b. Armoured chain conveyor c. Gate end loader d. Mobile stage loader e. Pick-aback conveyor 4. Plate conveyor 5. Disc conveyorC. Locomotive haulage a. Diesel locomotive b. Electric battery locomotive c. Trolley wire locomotive d. Cable reel locomotive e. Compressed air locomotive f. Electro-gyro locomotiveD. Shuttle cars
Underground transport arrangements are divided into twocategories:1.Main Haulage2.Gathering haulageThe main haulage arrangement is that which operates betweenwinding shaft/incline and the main underground loading points. Atthe main loading point, the loads are collected from one, two ormore districts.The gathering haulage arrangement is that which operates betweenthe working faces and the main loading points.In a large mine, where the working faces are far from the mainloading point, an intermediate transport arrangement operates and itis known as secondary haulage.
ROPE HAULAGE Presented by Presented by Prof. Devidas Nimaje Devidas S. S. Nimaje Assistant ProfessorDepartment of Mining Engineering National Institute of Technology Rourkela-769008, INDIA
Direct Rope Haulage Simplest system employing in the mine. consist of one pulling rope and one haulage drum for hauling minerals in tubs or mine cars up a gradient which is generally steeper than 1 in 10. The haulage engine is situated at the top of an inclined roadway. The train of tubs is attached to one end of the rope, the other end being fixed to the haulage drum. The empty tubs attached to the end of the haulage rope travel on the down gradient by their own weight and do not require power from the haulage engine. The drum shaft is therefore provided with a jaw clutch to disengage it from the engine. A slip ring motor with drum controller is used.
Advantages:1.The rope speed is generally 8-12 km/h and the system can operatebetween any point of the haulage plane and the haulage engine.2.It can, therefore, cope with the haulage requirements of anadvancing working face.3.Only one haulage track is required.4.The system can also serve branch roads if the gradient is suitablefor down-the-gradient movement of empties by gravity. For thisreason, the branch road deviating at an angle of not more than 40 0off the main road is convenient.
Disadvantages:1.High peak power demand as load starts its journey up thegradient.2.Severe braking duty on the downward run.3.High haulage speed demanding high standard of trackmaintenance.4.Not suitable for mild inclination of roads.5.A derailment is associated with heavy damage because of highspeed.
Direct rope, double drum balanced haulage It is the modification of direct rope haulage, two drums are provided so that when a train of full tubs is being hauled outbye, a set of empty tubs is lowered inbye. Both the drums are fitted with clutches and are mounted on the same shaft. Weights of the rope and the tubs are balanced and only the unbalanced load for the engine is mineral. This results in a reduced peak power demand and easier braking. The system gives higher output in each trip of the rope brings the loads and there is regular delivery of the loaded tubs. The system requires wider roads for the haulage tracks.
Track layout of Direct rope(E- Track of empties and F – Track of loads)
Endless rope haulageIn this system there are two parallel tracks side by side.One for loaded tubs and another for empty tubs and the endlessrope passing from the driving drum located at out bye end of thehaulage road to the in bye end and back again via a tension bogey.The tubs loaded as well as empties are attached to the rope withregular interval with the help of clips so that the entire rope lengthhas tubs on it at intervals.
Only one end of the tub is attached to the rope at a time. Butwhere lashing chain is used for attachment the normal practice isto attach a set of tubs and the attachment or detachment isperformed by stopping the rope if however clips are used forsingle tubs they can be attached or detached when the rope is inmotion.The gradient of haulage road is mild and rarely exceeds 1 in 6.The rope speed ranges between 3 km/h and 7 km/h and thehaulage is slow moving.The rope moves in one direction only.
Types:There are two types of endless rope haulage.1.Over Rope type: In over rope type the haulage rope passesover the tub or set of tubs.2.Under Rope type: In under rope type it passes beneath the tubor set of tubs.Advantages:1.Because of slow speed, less wear and tear.2.Accident from derailed tubs does not cause much damage due toslow speed.3.Motor of less power required.4.It does not place heavy demand on the power supply.
Disadvantages:1.It requires wide roads for two tracks.2.It is not suitable for sleep gradient.3.Load on the rope is large and a rope of larger cross-section isrequired.4.Large number of tubs and clips are required as rolling stock.5.If a breakdown of any tub occurs the whole system comes to astandstill.6.It cannot serve a main road and a branch road simultaneouslyunless elaborate arrangements are made to course the rope to thebranch line with the help of deflection pulleys. The tubs of mainroad rope have to be detached and reattached at the branch line.
Rope clips used in Endless haulageThe tubs, loaded as well as empties, are attached to the rope atregular intervals with the help of clips, so that the entire ropelength has tubs on it at intervals. When the clips are used forsingle tubs they can be attached or detached when the rope is inmotion.Types of rope clips:The design of endless haulage rope clips depends on whether thehaulage is of over rope type or of under rope type. Some of theclips used in the endless haulage are as follows:-1.Screw Clip2.Smallman Clip3.Cam Clip and4.Lashing Chain
Screw Clip:This clip is tightened on the rope by a handle and screw and the handle is coupled to the draw bar of the tub by a long steel rod hinged to the clip.Smallman Clip: consists of a pair of steel cheeks or side plates, loosely held together by the adjustable central bolt which has a spring surrounding it to keep the plates apart and kept in position by pins supporting the lever and the coupling hook. The clip can be detached automatically from the rope by fixing a bridge-piece or trip bar to a sleeper at such a tight and in such a way that the rope passes underneath while the lever of the clip strikes against it.
Cam Clip:This consists of a plate and a cam-shaped lever which is pivotedand is connected by a small chain to the tub to be hauled. The pullof the tub turns the lever around the pivot so that the grip of the clipon the rope is proportional to the load. On undulating roadways, aclip must be provided at each end of the tub .Lashing Chain:The lashing chain is usually 2.5 to 3 m long with a hook at eachend. One hook is attached to the draw bar of the tub and the otherend of the chain is coiled 3 to 4 times around the haulage rope andis linked to the chain. It slows down the speed of tubs causing lesswear and tear. It helps to prevent accidents by derailing the tubs.When the lashing chains are used to join tubs, it helps to attach tubsat different level easily .
Main and Tail rope haulageThe hauling engine is provided with two separate drums one forthe main rope, which haul the full train out and one for the tailwhich haul for the empty train in.When one drum is in gear, the other revolves freely on the shaftbut controlled when necessary, by the brake to keep the rope taut.The main rope is approximately equal to the length of the planeand the tail ropes twice this length.
Only one track is required.This system of haulage is suitable for undulating roadwayswhere it is impossible or undesirable to maintain the double trackrequired for endless rope haulage.It can readily negotiate curves and it is convenient for workingbranches.It operates at fairly high speeds and with long trains and if aderailment occurs, the resulting damage and delay likely to beconsiderable.
Advantages:1.This system of haulage is suitable for undulating roadways,where it is impossible or undesirable to maintain the doubletrack.2.Unlike endless rope haulage, this system requires one track.3.Less maintenance cost for one track compare to two tracks.4.Can readily negotiate curve.5.It is convenient for working branches.6.It operates at fairly high speed.
Disadvantages:1.As it operates at fairly high speed, more wear and tear.2.Derailment can cause more harms to man and machine.3.Long length of rope is required causing more cost ofmaintenance.4.It became very difficult to manage the system properly. Tail rope haulageIt is situated at the lower level and the empties are hauled up thesloping track. The haulage rope passes to the train of empty tubsvia a deflection pulley located at the top of the roadway. The loadstravel by gravity down the gradient but as the rope is attached tothem; their descent is controlled by the haulage driver.
Gravity haulage or Self acting incline This haulage operates without any motor or external source of power and consists of a cast iron pulley of 1.3 m to 2 m diameter having a brake path on the side and a strap brake. It is located at the top of the inclined roadway and is employed to lower by gravity the loads attached to one end of the rope which passes round the vertical jig pulley. Only single track is required for the operation but at the mid way of the road where the loads and empties meet, double track or a bye-pass is essential.
Jig pulley of gravity haulagePlan and section of layout of gravity haulage
Safety Devices in HaulageThe various safety devices used on haulage roadways are asfollows:1.Stop-blocks:A stop-block is a common arrangement placed near the top ofinclines. It consists of a stout beam or blocks lying across the rails,pivoted at one end and held against a pivoted side-block at theother. The side-block may be straight or bent. When it is desired toopen the blocks, side block is first opened and then the stop-blockis turned.
2. Buffers:When any roadways or face is in direct line with a haulage trackand persons may be exposed to danger from runaway tubs, strongbuffer is provided and maintained on haulage road to prevent suchdanger; Buffers may be horizontal or vertical.3. Back catches:It may consist of a pivoted piece of steel rail placed between thetwo rails as shown in the figure (monkey catch). Tubs can moveover it only in one direction. In case of backward runway it willcatch the tub axle thus arresting the tubs. A stout wooden block ispivoted at one end and passed over the rail by a strong springallows the tube in one direction only and prevents runway(backward) in case of spring catch.
4. Pointer plates:This is fitted on the main haulage track to deflect a backwardrunway into the prepared side of the roadway. The derailed tubsmay be automatically re-railed when drawn forward.5. Drop warwick:It consists of a girder (heavy type) hinged at one end to a speciallyset roof girder and held up at the other by an eye-bolt and pin. Thewarwick is released when required in emergency by a haulageworker pulling the wire to withdraw the pin. It may also beoperated automatically when the uncontrolled movement of tubsgives long swing to an operating handle.
An obvious disadvantage that excessive impact into the warwickmay displace the roof support, thus causing a roof fall, if thewarwick post (drop girder) is hinged to a roof bar. It is essentialtherefore to anchor the warwick to a girder not forming part of theroof support but firmly set into the side of the roadway. Thoughtmust also be given to the sitting of the warwick between refugeholes, avoiding possibility of accidents to persons shelteringtherein. The automatic closing type of warwicks are used whichare balanced by weights. The drop girder is slightly heavier thanthe weight rod attachment in this case. The moving tub itselfstrikes the weight rod attachment in this case. The moving tubitself strikes the weight rod to cause dropping of the girder at somedistance.
Such warwicks may be operated by means of:1.a weight rod suspended from the roof2.a side warwick in which a side arm is balanced to return to theclosed position either by gravity or by a set of weights after a lasttram has passed, the type has the swinging movement controlledby balance weights and pulleys.
Where, it is desirable to have the roadway closed that is againstrunways when tubs are passing under warwick. It is possible toconnect two warwicks in series so that when one tram opens andthe other is automatically closed. This system can only be installedwhere the trams run in one direction.Warwicks can be arranged to have an automatic tripping deviceincorporated whith comes in to operation when the normal speed isexceeded. This work on the principles that the trams travelling atnormal speed move a pendulum without disconnecting the slip linkwhich is holding a drop girder by means of a chain and cable. If acertain speed is exceeded the pendulum is struck a harder blow andsufficient to release the slip link and thus causing the girder to dropto the closed position.
6. Agecroft device:This is designed to arrest forward runways automatically. Theseworks on the principle that the first axle of the tubs depresses thehigher end of a catch raising the forked end to axle height. If thetub is passing at normal speed, the forked end drops before theback axle reaches it. If the tub is moving too fast the back axle isheld by fork and the tub is stopped.7. Backstays:Any train of tubs ascending an incline (except endless rope) shallhave a drag or backstay attached to the rear tub so as to preventthe train from running back. These may be attached to the tubaxle or to the tub drawbar according to their types.
8. Runway switches:The basic principle of these is that the tubs breaking loose froma rope are diverted by means of an open track switch.The runway points are closed by the tub wheels as the trainascends the incline but they are immediately opened againautomatically by the action of a spring.Runway tubs are then guided into the side to a place prepared toreceive them.The points are held in the closed position for tubs descendingthe incline, by a light rope attached to a specially designed catch29-30 m up the incline, which is released by a haulage hand whenthe train has gone over the point leaving them in safety positionwith the light rope slack.
A form of interconnected stop block and runway switch is usedat the brow of the direct rope haulage plane.It is so constructed that at one time either the stop block or therunway switch is effective in the event of a backward runway of aset of tubs.It is manually operated by the haulage attendant when the set oftubs has to pass clear of the stop block.The distance between the stop block and the safety switch issufficient to accommodate the full length of the train.
9. Jazz rails:The principle of this device is that tubs travelling at normalspeeds pass over a section of the jazz track negotiating the bendreadily.If the tubs travel at an excessive speed as in the case of runwaythey will fail to get round the bend and a derailment occurs.Rails should be bent to correct radius.
10. Retarders:Slowing down and stopping tubs are integral parts of haulageoperations.A hand operated retarder consists of two planks, lined on the topwith belting and mounted on cams. An end cover plank fastened tothe inside faces of planks serves to hold the plank in position.They are operated by a single lever. When the cams are fully raisedthe tub wheels are lifted clear to the rails and a braking action isprovided on the axle. The tub retarders represent waste of energy andshould be avoided in planning. However the speedy movement oftubs required for quick turnover and higher raising may make itsapplication essential at pit tops, pit bottoms, haul browheads, etc.there are many types of elaborate designs and manually controlled.Smooth braking may be effected by air or hydraulic braking.
Fully automatic retarders, which are released by pneumatic cylinders, are widely used. The device consists of two pairs of hinged bars faced with renewable skid plates and breaking action effected by movements of two opposing pistons in a cylinder containing air. The bars are raised above rail level and grip the wheels. When no braking is desired, the valve releasing to the atmosphere is opened after cutting off compressed air supply. A spring draws back the braking bars to normal position. Automatic hydraulic tub retarder is suitable for locomotive haulage or ordinary rope haulages. The hydraulic pressure is supplied from a 1-2 KW electrically driven pump. The oncoming tram is retarded by the tread of the leading wheels running between fixed skids and an inclined hinged platform which acts as wedges.
10. Approach warning device:It is sometimes necessary to warn men working or travelling in ahaulage roadway.A simple way of operating a warning device in rope haulageroads is an arm protruding into the path of oncoming trams whichwhen deflects closes an electric circuits connected to a signal lampor bell.The device is operated by a lever depressed by tram axle.
A back catch Runaway switchDrop warwick Signaling system with relay
LOCOMOTIVE HAULAGE Presented by Presented by Prof. Devidas Nimaje Devidas S. S. Nimaje Assistant Professor Department of Mining Engineering National Institute of Technology Rourkela-769008, INDIA
1. Where the gradient of the roadway is mild. Nearly flat gradient is preferred. A gradient of 1 in 15 against the loads is considered to be limit though locos are generally employed on gradients milder than 1 in 25.2. Where the loco track is in settled ground not subjected to movement by mining operations.3. In the intake airways where the velocity is adequate to keep firedamp percentage appreciably low. If diesel locos are used the exhaust gases of the locos should be diluted by the air current sufficiently well so as to be unharmful to the workers.4. Where roads are reasonably wide and high.5. Where transport of mine cars involve long haul distances. Small locos for shunting and marshalling at pit bottom are common.
Diesel Locomotive It is commonly used. Their weight ranges from 3 to 15 te and the power from 15 to 75 KW. The power unit is a diesel engine with 2,3 or 4 cylinders of 4 stroke cycle, compression ignition type. Heavy duty locos are of 6 cylinders. Locos used in an underground coal mines have the power unit in a flameproof enclosure as a safeguard against ignition of firedamp. The intake air going to the engine passes first through a filter and then through a flame trap. Similar flame trap is fitted on the exhaust side of the diesel engine [Exhaust conditioner].
The exhaust gases from the engine (very low CO%, O2, N2, CO2and small quantity of oxides of sulphur and nitrogen mixed withcertain organic compounds like aldehydes which smellabominably and cause irritation to the nose, throat and eyes)amounting to all about 0.085 m3/BHP/min are conducted to theexhaust conditioner, the hot gases are cooled down, filtered ( slagwool) properly and the flames are trapped inside the exhaustconditioner ( to remove oxides and aldehydes) and then the gasesare mixed with about 30 - 40 times their volume of fresh airbefore being exhausted into the ventilating current.
The filtering material and the flame grids (number of stainless steel plates 50 mm wide and ½ mm apart welded between adjacent plates in stainless steel housing) are readily removable and must be replaced by a clean set every 24 hours. The exhaust smell may mark the odour of spontaneous combustion and in mines where the coal is liable to spontaneous heating; the diesel locomotive should be avoided. It is not permitted in underground coal mines when the percentage of inflammable gases more than 1.25 % in the general body of air. If the water is allowed to fall below a certain level in exhaust conditioner, the fuel is automatically cut off from the engine and the brakes are applied.
Electric battery locomotiveThe power unit is a DC electric motor receiving its current froma storage battery carried in a casing on the upper part of the chasis.It is for light and medium duties as they are less powerful,though battery locos of 13 te weight available in our country.Range is from 4 – 70 KW continuous rating.It is quiet in operation and produces no objectionable fumes,produces less heat, can meet an appreciable overload of shortduration.
There are 2 batteries on a loco and it constitutes nearly 60%weight of the weight of the locomotive.The batteries are of lead acid type and each battery consists of a40-70 numbers of 2 volts cell.The battery cannot be made flameproof and its container has tobe well ventilated.It gives service of 8 hours of regular traction duty. At the end ofa shift, the battery has to be placed on a charging rack and it takesnearly 8 hours to fully charge.By a lifting tackle, the nearly discharged battery of a loco isremoved and placed on charging bays at the end of a shift andfully charged battery from the charging station replaces it.
The direct current for charging at the station may be available from the motor generator set or by the use of a mercury arc rectifier (no moving or rotating parts). The battery charging station should be close to the intake airway.
Overhead wire locomotive (Trolley wire locomotive)It is equipped with electric motor fed with current fromoverhead electric wire through a pantagraph or through a long polewhich is kept pressed against the overhead conductor by springtension.Only direct current is supplied to the overhead wires though insome foreign countries A.C. is permitted (conversion equipment isnot required but shock hazards are much more serious). The D.Csupply to overhead wires is at 250 volts. It is used in a number of coal mines near Kurasia colliery andfew other coal mines of degree-1 gassiness though DGMS office isgenerally conservative to granting permission for theirintroduction in underground coal mine..
The bare overhead conductors are of hard drawn copper wiresuspended centrally over the track at a height of more than 2 m.the conductors are suspended through insulators from short crosswire of mild steel.An earth leakage wire is connected to cross wire. The rail trackforms the return path for the electric supply circuit and thereforethe former must be suitably bridge at each rail joint by copperconductors.Section isolation switches for isolating parts of the roadwayshave to be used in easily accessible position to the roadsides.
The roadways should be sufficiently high and wide to provide safe clearance and the ground free from any movement arising out of mining operations. The roadways have to be equipped with overhead wires and the support system. Branch roads cannot be negotiated unless they are also so equipped. Locos are taken to the face by feeding power through a cable reel from the terminal of the trolley wire line. Mining regulations are stringent in trolley wire locos regarding shock to workers and fire damp explosion. Such locomotives are used in a wide scale in West Germany in deep gassy mines and also American underground coal mines.
Advantages:1.High Efficiency- of all the other locomotives used in mines,trolley wire locomotive is more efficient.2.High Overload capacity- for short periods, especially duringpeak loading activity, overloading of the motor do not pose anyproblem.3.Simple maintenance- most of the skilled work is to be done inthe power house.4.High speed/weight ratio- the motor speed can be easily increasedto give more tractive effort.5.Reliability- it is robust in construction and not liable tobreakdown.6.Good control- it gives smooth acceleration and high torque.
AERIAL ROPEWAY Presented by Presented by Prof. Devidas Nimaje Devidas S. S. Nimaje Assistant ProfessorDepartment of Mining Engineering National Institute of Technology Rourkela-769008, INDIA
An aerial ropeway is an installation in which transportation ofmaterial or men is effected by moving carriers pulled by ropessuspended above the ground.Types:On the basis of number of ropes and the mode of transportation, theropeways are classified as:1.Mono-cable Ropeway – the ropeway has a single running endlessrope which both support and moves the carriers.2.Bi-cable Ropeway- the ropeway has two fixed track ropes alongwhich the carriers are hauled by an endless traction rope.3.Twin-cable Ropeway- the ropeway has two pairs of track ropes tosupport the carriers and one endless traction rope.
ApplicabilityAerial ropeway provides the only economic means of long distancetransport over rough country, hilly and difficult terrain, even it canpass through the congested areas, marshy lands, nallahs, rivers, forestsand important agricultural land.Aerial ropeways have found wide application in:1.Transporting and conveying bulk materials between two fixed pts.2.Aerial dumping of load at any point along the line of route3.Stocking of materials4.Dumping of waste materials5.Transporting of persons in mountainous regions
Advantages:1.A relatively high transport capacity (upto 500 t/hr)2.Regularity of service and immunity to all weathers3.Ability to overcome natural obstructions (rivers, marshy ground etc.)4.Inherent ability to keep the ground free for other purposes5.Ability of negotiating steep gradient (70% and over)6.Possibility of using automation7.Minimum time lost in transportation8.Low initial and operating cost and short time for return on capital
Disadvantages:1.Fixed location of loading station2.Susceptibility to damage by string winds.3.The length of the line and transport capacity is limited byeconomic and technical consideration.
Bi-cable RopewayIt has following components:1.Two track ropes or cables stretched at required tension2.An endless traction rope for handling the loads,3.Carriers suspended from the track ropes and hauled by the tractionrope and4.Machinery and other arrangements for loading and unloadingcarriers, suspending the track ropes and driving the traction rope.
Scope of applicability and LimitationsBi-cable ropeways are suitable for capacities 100 to 400 t/hrandlengths up to 6 km in one section of traction rope.For capacities less than 100 t/hr and distances less than 300m, bi-cable ropeway cannot provide the desirable economy.
Different partsRopes:Track ropes:Track ropes are usually locked coil ropes made of large size wiresin order to have longer life. Locked coil ropes provide a smooth surface for the movement ofcarrier wheel and the surface wear of it is relatively uniform.The factor of safety for track rope during installation should be 3and must be withdrawn from service when it reduces to 2.5. Average life of the rope is 5 to 7 years.
Traction rope:Traction ropes are Six-strand lang’s lay with fibre core.The rope diameter varies from 12 to 46 mm.The factor of safety should be 5 during installation and ropesshould be withdrawn when it comes down to 4.
Carriers:A carrier has the carriage, hanger, bucket and grip for tractionrope.Carriage runs on track rope with wheels, and it runs on the trackrope, with the help of wheels (20 – 30 cm/diameter) mounted on it.The number of wheel is 2 for light loads and 4 for medium orheavy loads .The hanger is suspended from carriage to make its axis vertical.The bucket is supported by the hanger and grip on carriage.Three types of carriers are commonly used namely rotatingcarrier, bottom discharge carrier and fully enclosed bucket .
Standard car (Two wheeled and Four wheeled) of a Bi- cable ropeway for the transport of bulk materials
Trestles:The trestles for bi-cable ropeways provide support to both thetrack and traction ropes. as well as giving necessary profile to theropeway.The track ropes rest on the saddles at the top crossbeam and thetraction rope on the sheaves at the cross beam below.Trestles are constructed either in steel, reinforced concrete /timber.The height of the trestles is usually in the shape of a truncatedpyramid. The ht. of the trestles is usually 8 to 12 m on levelground and spaced at intervals of 100-250 m. But in amountainous region, they must be as high as 100 m and spaced at500 m or more. The trestles should be erected on firm ground.
Saddles:These are rolled steel section bent along their longitudinalcentral line to allow rope curvature on the support.The upper part of the saddle is grooved to accommodate andsupport the track rope.For safety against unloading of the rope, the groove dia. shouldbe 1.5 d and the depth of the groove 0.8d, where d is the diameterof the rope.
Stations:Loading station:Station where carriers are loaded are called loading station and inbi-cable ropeway it is more complicated than monocable ropeway.At the loading stations, the track rope tensioning device isavoided and the end of it is anchored instead. However thetensioning of the traction rope may be incorporated.
At the entry to station, the carrier leaves the track rope and rideson the station rail and while leaving it, rides back on the rope. Tofacilitate those, rope deflecting saddles are put at the transitionpoint.The carriers passes through the arrangement of releasing andgripping of the traction rope movement of the carrier is controlledmanually or by running chain at automatic station.Unloading station:It is the discharged end of the rope way.The unloading station should be sufficiently high enough abovethe ground level to make possible unloading by gravity.
Intermediate station:When a bi-cable ropeway has more than one section,intermediate stations are provided where it passes from onesection to another.Arrangements are there for tensioning.Angle station:When it is not possible to take a straight line route, anglestation are provided to change the direction of route.Here the track ropes of adjacent arms terminate by means ofanchorage or tensioning arrangement.
Examples:The following are the particulars of the different ropewaysoperating in jharia coalfield, India. These are only meant fortransportation of sand in the different collieries:-Loyabad ropeway- its starting point is river damodar (villagesJatudih, Ganeshadih, Jarma and Petia, district Dhanbad ). Thelength of the ropeway is 21,777 m.Terminating and serving points are1.Badroochuck colliery2.Mudihih colliery3.Mudihih-Tentulmari colliery4.Loyabad colliery
Sijua-Malkera ropeway- its starting point is river damodar( village tangabad, district Dhanbad). The length of the ropeway is 14,346 metres. Terminating and serving points are-1. Sijua colliery2. Malera colliery Potkee-kankanee ropeway- its starting point is river damodar (village Dhawardah, district Dhanbad). The length of the ropeway is 22,265 metres. Terminating and serving point are-1. Kankanee colliery2. Potkee colliery
BELT CONVEYOR Presented by Presented by Prof. Devidas Nimaje Devidas S. S. Nimaje Assistant ProfessorDepartment of Mining Engineering National Institute of Technology Rourkela-769008, INDIA
The belt conveyor is basically an endless belt in a straight line stretched between two drums, one driving the system and the other acting as a return drum. In coal mines and other mines of stratified deposits, where the underground mineral if won by longwall method, the transport media which often consists of conveyor .
Layout of face, gate and trunk conveyors in a coal mine
The system of transport by belt conveyor consists of thefollowing:1.A flat endless belt which moves continuously and carries at itstop surface the material to be conveyed.2.The idlers which support the belt.3.The structure of channel iron on which the idlers are mounted.4.The tensioning arrangement for keeping the belt in propertension.5.The drums at the discharge and tail end over which the beltpasses.6.The drive head which comprises the electric motor, coupling,gearing and snub pulleys
Arrangement of a belt conveyorCross-section of belt for conveyor system
Selection of belt conveyor:1.Amount of material to be conveyed2.Continuity of operation needed3.Size of lumps4.Distance of transportation5.Environmental allowance6.Gradient7.Method of coal winning, i.e. Longwall or Bord and Pillar•Capital Available
Advantages:1.A continuous supply of material.2.Low operating cost than road transportation system.3.High rate and speed of supply.4.Bunding can be done to get fair grade.5.More efficiency and low cost.
Limitations:Belt conveyor:1.Cannot be used for long distances2.Required high one time capital3.Lumps should not be of big size.4.Place should be dry enough and air velocity should not be high.5.Cannot be worked for high inclinations
Factors for designing of belt conveyor:1.The average tonnage (t/h), peak rate (t/min) and frequency of peakrates.2.Characteristics of the material i.e. density, maximum lump size,nature of material-dry, wet, sticky, dusty, chemical action on belt.3.Graphical layout of conveyor profile and motive power available(i.e. electric motor).4.Operating conditions - hours of working, climatic conditions etc.5.Suitability of a belt conveyor & width and speed of belt6.Belt shape.7.Power and layout required.
Take- up arrangements (Tensioning device):Tensioning of the belt is necessary to prevent excessive sagging ofthe belt or belt in good contact with the driving drum.1.Automatic take ups2.Gravity take ups.3.Take up pulley with counter weight.4.Counter weighted loop take.5.Counterweighted wheel mounted tail end pulley6.Power take ups7.Electric motorized winch and load cell loop take up.8.Pneumatically operated take up9.Hydraulically loop takes up.10.Rigid or manual take ups11.Screw take up12.Jack take up13.Winch take up
Arrangement of a drive motor, loop take-up andtensioning weights on a belt conveyor discharging downhill
Arrangement of a driving gear and loop take- up for a belt conveyor on level or uphill
Belt conveyor Troubleshooting Trouble Causes Corrections One or more idlers inbye of the Advance the end of idler to which1. Conve trouble not at right angles to belt has shifted in the direction of yor longitudinal centre line of belt. belt travel belt runs to Conveyor frame not lined up Stretch line along edge to determine one properly or idler boards not how much out of line and correct side at centred on belt. a Sticking idlers Replace or free idlers particu Structure not level and belt Level structure lar tends to float to low side point on the Improve maintenance. Install belt convey Build up of materials on idlers. and pulley scrapers or
Joint not square Rejoint, cutting belt ends square.2. One section of If bow is in new belt, it may correct itself belting runs off to Crooked belt after being run in, if not try and re-cut joint one side all along caused by bad to counteract otherwise replace with new the conveyor storage length.3. Conveyor belt runs to one side of Improper loading Mostly receiving hoppers or chute to load structure along of belt material centrally conveyor line May be due to newness. If it so, allow time4. Conveyor belt has to settle down. It will shorten the time, if erratic action belt is left loaded not in use. Tilt troughing Belt too stiff following no idlers forward a maximum of 30.Use self- particular position. aligning idlers. Use more flexible belt or less steep troughing idlers.
Head pulley out of Check alignment of pulley alignment and adjust if necessary5. Belt running off at head Troughing idlers Check alignment of pulley approaching head pulley troughing idlers and adjust out of alignment. if necessary Clean idlers and provide Build up of materials on more maintenance and return idlers better belt cleaners.6. Belt running off at tail Return idlers out of Check and adjust as pulley alignment necessary. Adjust loading chute to Unequal loading properly centre the load.
Adjust tension on belt take-up device. Slippage between belt and Increase angle of wrap of the belt on drive pulley the drive pulley with snub pulley. Lag drive pulley or renew worn-out lagging.7. Excessive wear Stitching or seized Replace or free on back cover troughing idlers of belt Install scrapers in front of tail pulley Material spillage between on return belt or snub and bend pulley and belt. pulley Too large a pitch causes belt trough Excessive pitch of to flatten and belt slip between belt troughing idlers and wing idlers rolls remaking trough. Reduce pitch of idlers.
Install belt cleaners, snub Dirty, frozen or misaligned pulley scrapers and plough at return idlers. tail end pulley. Clean, adjust and replace where necessary. Excessive sag between troughing idlers causing Increase belt tension if too8. Excessive wear on top cover load to jog as it passes over little. Reduce idler pitch. of belt idlers. Use soft rubber skirt material, Abrasive Skirt board never use old belting. Engineer loading chute to load material centrally, in the same Poor loading direction and as near belt speed as possible.
Reduce friction by cleaning up conveyor, replace stuck or worn out idlers. Provide better maintenance. Reduce belt tension by lagging drive pulley or increasing angle of wrap of belt on drive Too much tension due to pulley. Increase belt speed keeping improper maintenance of9. Excessiv tonnage same. troughing and return idlers e stretch Reduce tonnage keeping the same belt in belt speed. Slacken tensioning device until the tension is just enough to keep belt from slipping. Belt too tight for the horse Replace with proper belt of lower power to be transmitted elongation or higher strength.
Impact of large Use impact idlers. Engineer the loading chute so lumps felling on the impact hits the back plate. Load in line with the belt at loading belt at a speed equal to belt speed. station10. Short Material trapped breaks in between belt and Install ploughs or scrapers ahead of tail pulley. the cercass pulley of the belt Use of deep Reduce angle of troughing or replace with troughing idlers correctly designed belt.
Reduce friction by cleaning up conveyor, replace stuck or worn out idlers. Provide better maintenance. Reduce belt tension by lagging drive pulley or increasing angle of Tension too high wrap of belt on drive pulley. Increase belt speed keeping tonnage same. Reduce tonnage keeping the same belt speed.11. Fasteners pull out Slacken tensioning device until the tension is of belt just enough to keep belt from slipping. Mildew Use mildew inhibited belt. Wrong type of fasteners and Replace belt joint with correct fasteners. improper jointing Improper starting Use fluid coupling on torque clutch between (Direct-on-line- motor and reduction gear. starting)
Difference of 1/8” in Unequal diameters of diameter will cause pulleys squealing.12. Excessive noise or Too little tension applied Tighten belt by tensioning squealing in tandem to the slack side of the device. drive gear belt at driving gears Incorporate fluid coupling Too sudden a start between motor and reduction gear. One or both pulleys Tighten pulleys loose on shafts13. Thumping noise in the Gears out of mesh tandem drive improperly machined of Change gears badly worn
SCRAPER CHAIN CONVEYOR Presented by Presented by Prof. Devidas Nimaje Devidas S. S. Nimaje Assistant Professor Department of Mining Engineering National Institute of Technology Rourkela-769008, INDIA
It is mostly used in the longwall face. The capacity of a commonly used scraper chain conveyor is 30 to 40 tph on a level roadway, nearly 50 m long and the drive motor is of 12- 15 KW. The main application of scraper chain conveyors in underground is transportation at the face and adjoining short workings, where they are ready to withstand mining condition. They are also used to haul the coal along gate roads over short distances before it is feed to gate belt conveyor. They are also used for transporting on inclines having an angle of inclination exceeding 180 where belt conveyors are not used. They are also used on the surface for conveying coal from shaft to bunker as well as in screening and washing plants.
Different parts:1.Trough:These are stationary things usually 2m long, and consisting ofdetachable section bolted together or joined by hooks,2.Flights:An endless chain with flights moving in the troughs, which arenearly 450 mm wide at top and 300 mm at bottom.3.Chain (endless):The chain of endless character is installed there. The chainconsists of links and after 3-4 links a flight is provided so, that theflights are 2-2.5m apart.
4.Tensioning head:The return or, tail end of the conveyor with its totally enclosedsprocket drum, is provided with telescopic trough by which thetension of the chain can be adjusted through Sylvester chain5.Drive:For enabling movement a power arrangement with drivingarrangement.6.Angle iron frame:to support the troughs.
Types:On the basis of flexibility—1.Rigid chain conveyor2.Flexible / Armoured chain conveyorOn the basis of number of chains used—1.Single chain conveyor2.Double centered chain conveyor3.Double outboard chain conveyor4.Triple chain conveyor
Rigid chain conveyor:1.A rigid chain conveyor essentially consists of stationary steeltroughs, each usually 2m long, connected together end to end, andan endless chain with flights moving in the troughs.2.Troughs supported on angle iron frame work, slightly dished atone end. So, that the next one fixed in to form a flush point.3.Adjacent troughs are secured together and to the frame underwayby both.4.This gives rigidity to conveyor.5.The return end is provided with a tensioning arrangement.6.The capacity is 30- 40 tph on a level roadway, nearly 50m longand 15KW motor.
Armoured chain conveyor:1.Used generally on long wall faces, it can be advanced withoutdismantling, with hydraulic rams.2.They can work with lateral or, vertical undulations, and coalcutting machine and shearers can be mounted on them.3.Motor power varies between 30 to 185 KW.4.Pan width at top varies from 750 to 850 mm and pan length from1.3 to 1.8 m. the vertical flexibility of pans is 3-4 0 and horizontalflexibility is 2-30.5. Limiting gradient with flights 1 in 1.5 and without flights 1 in 3.6. Length may be upto 360 m and capacity is upto 100 tph.
Advantages:1.Can convey uphill against relatively steep (1 in 3 or more)gradient as well as of downhill gradient.2.Much stronger and can be roughly handled.3.Flexible so, as to dismantle, extended or shortened.Disadvantages:1.High initial cost.2.High power consumption3.Wear and tear more4.Highly noisy5.Producing high percentage of fine dust
SCRAPER HAULAGE Presented by Presented by Prof. Devidas Nimaje Devidas S. S. Nimaje Assistant ProfessorDepartment of Mining Engineering National Institute of Technology Rourkela-769008, INDIA
Scraper haulage is the simplest method of transportation ofbroken materials where a scraper bucket digs into materials andtransports it by dragging it over natural or specially-preparedfloor.Types:Scraper haulage is classified as:1.Two drum hoist2.Three drum hoista)Without obstacleb)With obstacle
1. Two drum Scraper hoist: There may be different arrangements of scraper haulage depending on working conditions and type of scraper hoist used. The arrangement is generally used where load has to be transported along a straight line. The main rope is attached to the front end of the scraper bucket, while the tail rope passes round a tail block sheave 4 secured at the face and is fastened to the rear end of the bucket.
The main rope hauls the bucket from the face to the ramp 5 for loading into cars or to an ore pass wherein its content is emptied out. The tail rope pulls the bucket back to the face for reloading. Where load has to be transported from wide faces the tail block would require to be shifted along the face to avoid manual shoveling of material on to scraper path. This would involve considerable manual work and also decrease the performance of hoist. For that reason a 3-drum hoist (instead of 2-drum) may advantageously be used.
Arrangements of two drum Scraper haulage Two drum Scraper hoist
Construction:It consists of an electric or compressed-air motor 14, main andtail drums 8 and 9, gears, and two operating handles forcontrolling the band brakes 12 and 13.The motor drives the main shaft through gears 1-2 and 3-4.The main shaft carries two sun wheels 5 which rotate the planetwheels 6 mounted freely (on ball bearings) on the shafts 10 and 11which are rigidly connected to the drums.The planet wheels in turn rotate the wheels 7 (mounted on ballbearings) by meshing with its inner teeth, when the brakes are off.
On applying the brake, the rotation of wheel 7 is prevented, as aresult of which the planet wheel revolves round the sun wheel thussetting the drum in motion.The drums are thus driven by gears of force of friction betweenthe bands of the brakes and the outer surface of wheels 7.This prevents overloading of the motor as well as breakage ofropes and damage to other parts when the scraper bucketencounters obstacles due to the bands slipping on the wheel 7.
Two-drum scraper hoists with sun-and-planet gearing are simple and reliable. But they have the disadvantage that the tail black has to be shifted along face for proper cleaning if the latter is wide (otherwise hand-shoveling becomes necessary). The more complicated three-drum scraper hoists do not suffer from this disadvantage. They have similar construction and are fitted with three band brakes and consequently three operating handles.
2. Three drum scraper hoist:In this case three ropes (two tail and one main) are attached tothe bucket and two tail blocks are installed one at each end of theface so that the scraper bucket may be hauled back to any pointalong the face by suitable manipulation of the tail ropes.The main rope only hails the loaded bucket.Any modification of this method may be used where the scraperbucket has to be manipulated around obstacles (for example,around the pillar).
In this case, two main and one tail ropes are used. One of the main ropes is guided by a guide block while the other is guided around the obstacle by a guide roller. The loaded bucket is first hauled by the rope passing round one guide block sheave to a point clearing one obstacle and ones hauled by one, second main rope to one unloading point after emptying. The bucket is hauled back with the aid of the first main rope and the tail rope. A similar arrangement may be adopted where the load has to be transported along two roadways meeting at an angle.
Method of Scrapping with three drum hoist – a) without obstacle b) with obstacle Types of Scraper buckets
BucketsVarious types of scraper buckets are used in practice, dependingon working conditions and properties of materials to be handled. The box-type buckets are suitable for relatively light and well-fragmented materials. They have a slanting back for easy digginginto the interior and vertical sides for counting the materials duringits transport.For hard-digging and large-size materials, hoe-type buckets areused. These dispense with side walls and are often fitted withdetachable manganese-steel digging teeth.
The main factors governing the performance of a scraper bucketare its weight G and the angle of digging ( the angle between theslanting back or teeth and the horizontal).The tare weight of a bucket is usually equal to 0.5 to 0.6 G,where G is weight of the material in the bucket.Some types of buckets are provided with arrangements forincreasing their weight by adding two or three cast-iron weights toimprove their digging characteristics.The angle of digging is chosen as 30 to 35 degree for box-typebuckets and 50 to 60 degree for the hoe-type ones.
Tail Block The tail block is anchored to the face by an eye blot wedged in a 0.5 m deep hole. It should be light in weight for easy removal and refixing at face. The block sheave is usually 200 to 350 mm in diameter. Ropes The ropes for scraper haulage should be flexible and resistant to abrasion. The parallel-lay rope of Seale-strand construction, in which an inner layer of thinner wires is covered with thicker outer wires, is most suitable for scraper haulage.
WINDING Presented by Presented by Prof. Devidas Nimaje Devidas S. S. Nimaje Assistant ProfessorDepartment of Mining Engineering National Institute of Technology Rourkela-769008, INDIA
Winding system are classified into two groups based onthe device employed to hoist the cage or skip to thesurface:1.Drum winding2.Koepe winding (Friction winding)i.Ground mounted koepe systemii.Tower mounted koepe systemIn the drum winding system, cylindrical drum with tail rope orbi-cylindro-conical drum are commonly used in most of the minesbecause it gives balanced system and reduced the peak powerdemand and negative torque.
In koepe winding system, the power is transmitted through thefriction between the winding rope and the lining of the sheaves.In ground mounted koepe system, the winding engine is installedat the ground level and the headgear sheaves are situated one abovethe other or side-by-side on the headgear. The rope operates in theplane of koepe driving wheel without any angle of fleet.In tower mounted koepe system, the winding engine is installedon the headgear. It also requires deflecting pulley to deflect thewinding rope.
Selection of Winding system:It is based on the following factors:1.Depth: For deeper shaft, koepe winding system is suitable ascompare to drum winding system which is suitable for shallowshaft.2.Decking system:For multideck winding system, the drumwinding is suitable.3.Space: For less space, koepe winding is suitable and for largerspace, drum winding is more suitable.
4.Multilevel: Winding from different levels, drum winding issuitable while koepe winding is suitable to hoist from one level.5.Simplicity: Koepe is simple and maintenance is easy.6.Safety: Drum winding is more safe compare to koepe windingsystem.7.Economic: Koepe is more economic in terms of maintenance,installation and fitting are easy as compare to drum windingsystem
Main Parts of the winding systemHeadgear and Pulley:The head gear is a steel or concrete framework on the shaft mouth.Its purpose is:1.To support the head gear pulleys, the weight of the hoisting rope,cages and rope guides.2.To guide the cage to the banking level.It should withstand dead and live loads and wind pressure.
The dead loads on the headgear are reasonably constant and calculable but the live load due to winding is a variable one depending on the length of ropes in the shaft, the contents of the cages and the rate of acceleration and deceleration. Head gear is used for tower mounted koepe winders are designed to carry in addition the load of motors, winding pulley and other equipment for winding. The head gear consists of nearly vertical columns or girders braced with horizontal girders. The members narrow at the top and battered at 1 in 8 to 1 in 10 for a larger width at the foundations.
Of the four legs the two nearly vertical main legs are connected to two inclined back legs (towards the winding engine room). The top of the headgear has a steel platform or plate and the bush bearings of the winding pulleys rest on the vertical members of the headgear frame. It is usual to design the upright members of the headgear frame to carry the dead weights and the wind pressure, leaving the back legs to the take care of the resultant of the live loads due to the ropes and cages.
The height of headgear is decided by considerations of number of decks on a cage, banking level or skip discharging point, pit top layout and depth of the shaft. The headgear pulley should be at such a height above the detaching plate that the rope capel is released before it comes in contact with head gear pulley. The distance is about 3m. The design of the headgear depends upon dead and live loads, the depth of the shaft, the quantity of material raised per hour, the diameter of the shaft, size of the skip or cage and the winding speed of the drum.
The head gear pulley should have as large a diameter as possible to minimize bending stresses in the winding rope. Its diameter should be at least 100 times the rope diameter. Pulleys of over 2.5 m diameter are generally constructed in two halves and bolted together. Normally the diameter of the groove of the headgear pulley should be 110% of the rope diameter for stranded ropes and 105% for locked coil ropes. This ensures that 1/3rd of the circumference of the rope are in contact with the groove. A lesser angle of contact causes excessive strain on the rope and wear on the pulley.
The headgear pulley is keyed to a mild steel forged shaft, which rests in plain bushed journal bearings. The angle of fleet, which is the angle between the vertical plane of the pulley and the rope, when the cage is at the pit top or pit bottom, should not exceed 1.50. More fleet angle results in wear of the rope and wear of the pulley. The shafts of the two head gear pulleys which are placed side by side are in a horizontal line and their planes of rotation are vertical and parallel. In the case of koepe winders, ground mounted the planes of rotation of the two headgears pulleys are one below another. If a drum winder is used for a deep shaft, it may be necessary to consider double layer coiling of rope in order to accommodate all the rope on the drum and keep the fleet angle limited to 1.50.
Fleet angleArrangement of driving sheave and pulleys in koepewinding Left: tower mounted; right: ground mounted
Cage attachment to Winding RopeA typical arrangement of attaching cage to winding consists offour cage chains in the case of a single cage (and 6 chains in thecase of a tandem cage) attach the cage to a triangular distributionplate which is connected to a safety detaching hook through D-links. The detaching hook is attached to rope capel.Under mining regulations all the chains are to be checked inevery 6 months and the detaching hook is made of 1.5%manganese steel.
Cages and SkipsThe cage is a lift suspended from the winding rope, open at bothends where gates can be positioned during man riding and it hasrails fitted to the floor for mine cars or tubs.To prevent the mine cars/ tubs from falling outside the cages,catches are provided on the floor which act against the axles of themine car / tubs; in addition, a long bar, turned at both ends andhinged at one side of the cage, prevents movement of the tubsduring travel up or down the shaft.Cages used for man riding have a hand bar near the roof for themen to hold and at both ends collapsible gates are provided whichcan be closed or opened manually or by compressed air.
The roof has a hinged or removable door for accommodating longtimber or rails whenever necessary.A cage which can accommodate only a single tub is a single cageand one with two tubs is called tandem cage.Cages with more decks are used in mechanized mines dealingwith large output. The cage travels in the vertical plane.
Advantages of cage:1.They are made to travel in vertical plane.2.Winding coal and mineral from different levels is easy.3.These are best used in shallow mines.4.A high head gear is not required.5.Cost is low and efficiency is high.Disadvantages of cage:1.The ratio of payload/ gross load is low around 0.352.They cannot be fully automatic.3.There is a problem of accurate landing of cage at decking level.4.Manpower is required for handling of tubs.
A single deck cage and skip A skip for automatic tipping in an inclined shaft at Mosabani
Skip can be filled with minerals through its top opening skips traveling in a vertical plane have a discharge opening at the bottom for unloading the mineral content but skips traveling a rail along an inclined haulage plane are so tilted, during travel, near the unloading end that their contents are discharged from the top end. Skips moving in a vertical plane are sometimes partitioned for accommodating men at the upper half and material/ mineral at the lower half. Skips are provided with cast steel guides shoes having malleable cast iron brusher, usually four shoes per cage or skip. The skip carries a large payload, usually 8 ton or more, compared to the cage and the ratio payload/ gross weight of skip (loaded) is high for skip
Advantages of skip:1.Skip winding is best suitable for deeper shafts where high output isdesirable.2.The ratio of payload/gross load of loaded skip is high nearly 0.6.3.Skip lends itself to automatic loading, unloading and deckingoperations, and thereby providing quicker cycles.4.There is less man power requirement for skip installation.5.Fully automatic installation of skip is possible.6.Skip can travel on vertical or inclined plane.Disadvantages of skip:1.Separate arrangement -made for winding of men and material.2.It is difficult to import dirt, washery refuse for goaf.3.It is essential to load skip in upcast shaft.4.Winding of coal/mineral from different levels is not convenient.5.A high headgear is required and the shaft sunk deeper.
KepsKeps are retractable supports for cages that ensure not onlysupport to the cage but their use results in proper alignment of thecage floor and decking level so that the stretch of the winding ropecreates no difficulty during decking.Keps are used at the pit top under our mining regulation.Their use is not necessary at the pit bottom as the cages rests onrigid platform at steel girders and wooden planks.Keps are not required at the mid-set landing and in a shaft servedby koepe winding system.
In the case of koepe winder, the decking difficulties arise and areovercome by the use of tilted or hinged platforms.Keps may be operated by hydraulic or pneumatic power. Wherethe keps are pneumatically operated they are interlocked with otherdecking equipment so that they can be withdrawn or brought intouse at the correct time in the cycle of operations of the associatedequipment at the pit top.Types:These are of two types.1.Rigid keps2.Davies improved keps gear
Rigid keps:Rigid keps provide support to cages on hinged platforms.They are manually operated by the banksman at the pit top.The ascending cage pushes the keps back and as it is raisedslightly higher than the decking level, the keps fall back in positionby gravity after releasing opening lever.The cage, after it has come to a halt, is lowered by the windingengineman to rest on the keps.When the top cage is to start on its downward journey, thewinding engineman raises the cage only slightly to make it clear ofthe keps; the banksman withdraws the latter by manual operation ofa lever which is held by him till the cage is lowered past the keps.
Disadvantages of Rigid keps:1.Accumulation of slack rope on the pit bottom cage when the topcage is raises a little for withdrawal of keps. Ascent of the pitbottom cage is generally associated with shock load on the windingrope and the stress amounts to 200% of the static load.2.Loss of time and power in lifting the top cage before its downloadtravel.
Davies improved keps gear:The gear consists essentially of the shafts S to which is keyedthe hand lever and a pair of arms A with a steel roller R mountedon a pin between the arms.The roller presses against a renewable roller path on a swinglever L which is pivoted at P and carries a “pallet” mounted on asteel pin at its other end.The pallet is free to move upward and around the pin, andallows upward passage of the cage, but it is prevented frommoving downwards by a projection on the lever L.
The cage is thus securely supported on the upper surface of thepallet.The gear may be withdrawn, however without first raising thecage.It will be seen that when the hand lever is moved to the left, theroller R moves upward along the roller path on the lever L, thusallowing the lever to rotate downwards by gravity around the pinP until the pallet is clear of the cage.
Detaching HookDetaching hook which is just placed below the rope capel, is asafety device which acts when an overwind takes place.Its purpose is to suspend the cage/ skip in the headgear if anoverwind occurs and at the same time to release the rope to go overthe head gear pulley.Types of hooks:1. Ormerod detaching safety hook.2.King detaching safety hook.
King detaching safety hook: It is generally used in most of the winding system. It consists of four wrought iron plates i.e., two being moveable inner plates and two fixed outer . The two inner plates are placed together in opposite ways so that the hook of one plate and that of the other jointly form a secure hole for the reception of the rope capel bolt. A main bolt or centre pin passes through the holes and in all four plates and serves1. To bind the plates together2. To transmit the tension of the winding rope from the hooks of the inner plates to the shackle both of the main D- link and3. To provide a pivot on which the two inner plates can move.
The hooks are so curved that pull of the winding rope has no tendency to open out the inner plates. A copper pin is placed through the holes c in all four plates and riveted over to prevent inadvertent movement of the inner plates when they are not under tension. During an overwind as the ascending cage goes up the hook is partially drawn through the circular hole in catch plate, securely attached to a horizontal member of the headgear and the lower wing d of each plate (inner) is forced inwards. The copper pin is thus sheared and hooks in are forcibly separated, so releasing the D-link of winding rope capel. Simultaneously the catches g on the inner plates are forced outwards so that rest on the upper side of the catch plate and the cage in thereby safety held.
When the weight of the cage is taken by the catches g, the inwardpressure of the wing d is borne by the sloping sides of a wedgeshaped block which is placed between the lower ends of the twoouter plates which is securely bolted to them.For lowering the cage after an overwind, a vertical slot h isprovided in each outer plate and an inclined slot t in each innerplate.The cage being suspended, the slots in the outer plate remainvertical but those in inner plates take different positions so, as tomaintain circular hole through all the plates.
To restore the cagePlace a few rails across the shaft top.Bring the winding rope capel back over the pulley and attach it tothe plates by special D-link whose pin should pass clear through thehole on it.Raise the cage slightly and pull of the rope on new D-link pincauses the latter to rise along the inclined faces of the inner slots.This forces the hook m and catches g inwards in their normalpositions.Now lower the cage to the banking level.Replace the hook and fit it with a new shearing pin. The catchplate should also be changed.
Inner plates Outer platesHook assembled and in Hook detached and cage working order suspended during overwind
Example:Narwapahar underground uranium mine (UCIL,India)The type of winding system is ground mounted friction winder. Theshaft has two winders one for cage and the other for the skip. Thecage is for men and material movement and the crushed material isloaded to skip for hoisting. Specification Cage Winder Skip Winder Make ABB Sweden ABB Sweden Pay load 5 tonnes 5 tonnes Max. Speed 8 m/sec 8 m/sec Total hanging load 13.772 tonnes 14.37 tonnes Hoisting speed 3.5/6.0 m/sec(man) 8 m/sec(ore)
Acceleration 0.77 m/s2 0.77 m/s2Retardation 0.77 m/s2 0.77 m/s2Hoisting distance 321.5m 324.14 mPulley diameter 2.8 m 2.8 mPulley speed 54.6 rpm 54.6 rpmRope diameter 28 mm 28 mmRope length 427.181 m 450 mNumber of ropes 2 2Counter weight 8.445 tonnes 8.634 tonnesTail rope diameter 48 mm 48 mmTail rope length 356 m 373 mGuide rope diameter 32 mm 32 mmGuide rope length 356.8 m 383 mMotor DMA 315 L DMA 315 LRated output 186 KW 250 KWRated voltage 391 V 397 VRated current 510 A 683 ARated speed 751 rpm 751 rpm
Safety devices1.Cage block switch (Thyristor controlled):Cage block switch is used to provide support to the cage during itsdownward motion preventing accident. It’s construction is suchthat it allows the upward motion but restricts the downwardmotion of the cage. It is similar to safety catches.2.Gate close switch:Gate close switches are provided which closes the cage from allsides while transportation of men and material.
3.Over speed MP (Master Piece) :Over speed switches are provided which cut off the power supplyin case of over speed.4.Over speed and overwind contrivances (LillyDuplex controller):Position of cage in the shaft:Two cam dials, one for each direction of motion, are mounted onhubs, keyed to a common shaft and driven by a spur and wormgearing on a drive from the rotating winding drum. The gear ratiois such that a maximum angular movement of the dials of about300° corresponds to the travel of the cages or skips in the shaft.
Speed of cage in the shaft:Two centrifugal governors, driven by a shaft from the windingdrum, operate on a floating lever system which is connected to apair of floating contacts. An increase in speed causes the governorsto exert more force on the lever system and the floating contactscome closer together. An increase in speed of about 10% abovenormal sounds an alarm and if no action is taken, these contactsclose to operate the safety circuit which cuts off power to thewinding engine and actuates the braking system.5. Wooden arrester:It has internal linkage to the cage block controller, in case it fails toarrest the cage ,wooden arrester will be placed automatically whichblocks the cage.