GUIDE ROPE LUBRICATION

A CASE STUDY IN UCIL’sJADUGUDA MINE

PINAKI ROY

PREAMBLE• In underground mines, the entry into the mine is mostly through a

mine shaft by means of the mine winder and its conveyances. With the entire workforce to be daily transported through this form of transport deep into the mine, the winding system must maintained optimally and safely.

• In order sustain very high safety standards, all the components of the winding system i.e. the entire winding mechanism, controls, shaft accessories, conveyances and specifically the various steel wire ropes, require utmost care - as any laxity can prove to be disastrous with critical rescue operations.

• The challenges of evacuation in a mine accident are different from other accidents as in these accidents the approach route (whether a mine shaft or decline) gets blocked.

• One such example may make it clear.

The Chilean Mining AccidentThis mine accident took place on 5th

August because of a cave-in a 120 yearold copper–gold mine.The mine is located deep in the AtacamaDesert in northern Chile, South America.33 miners were trapped 2,300 ft belowground and about 5 Km from the mine'sentrance connected via spiralingunderground ramps. The mixed crew of old and youngMiners and technical support personnelsurvived for a record 69 days deep inthe mine before their rescue.

These 33 persons were lucky tohave come out alive because inmost cases – images could be different

IMAGES YOU WOULDN’T LIKE TO SEEA rock fall, roof collapse or even a wire rope failure can put many lives below ground to severe risk and cause untold trauma to their families. Thus regular inspection, care and upkeep of all mine areas and equipment assumes critical importance.

MINE WINDERSBefore talking about mine ropes one shouldknow where they are used as it may helpunderstand their importance.

Mine Winders are fundamentally elevatorswhich hoist and lower men, mineral andmaterials into and out of the mine. While theprinciple of working is similar the main difference isthat mine conveyances are bigger, more rugged andtravel much deeper into the ground carrying heavierloads and at higher speeds, through the mine shaft. A mine shaft can thus be envisaged as an elevatorwell in reverse, going thousands of feet into theground. The mine conveyances are driven from thesurface by means of wire ropes - the onlyconnection.

Understanding an Elevator In elevators, the passenger compartment is raised

and lowered by steel traction ropes. The ropes are attached to the elevator car and looped around a sheave (3) which can be a drum or a pulley with grooves around the circumference. The sheave when rotated makes the ropes move. The sheave is connected to an electric motor (2). The rotation direction of the motor causes the elevator to go hoist or lower. The ropes that lift the car are also connected to a counterweight (4), which hangs on the other side of the sheave. The purpose of this is to conserve energy as with the counterweight it only takes a little bit of force to tip the balance one way or the other. Both the elevator car and the counterweight ride on rigid guide rails (5) along the sides of the elevator shaft. The sheave, the motor and the control system (1) are all mostly housed in a machine room located above the elevator shaft.

What is a wire Rope ?

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Wire rope is a type of rope which consists of several strands of metal wire laid (or 'twisted') into a helix. Initially wrought iron wires were used, but today steel with a carbon content of 0.4 to 0.95% is the main material used for the manufacture of wire ropes. Wire rope systems are used as a means of transmitting mechanical power.

Stranded ropes are manufactured in 3 operations:1. Manufacture of the core (center)2. Spinning the wires into strands3. Laying the strands to form the rope

Construction of a Wire Rope

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The wires are the smallest elements which form the strands.

The strands are helically around the core.

The core forms the foundation for the strands.

Wire

Strand

Wire Rope

wire

Strand

Rope

Properties & Types of Wire RopesTensile StrengthTensile strength is the strength necessary to withstand a certain maximum load applied to the rope.

Crushing Strength Crushing strength is the strength necessary to resist the compressive forces that distort the cross section of a wire rope, as it runs over drums under a heavy load.

• Fatigue Resistance• Fatigue resistance is the ability to withstand the

constant bending and flexing of wire rope that runs continuously on sheaves and hoist drums.

• Abrasion Resistance• Abrasion resistance is the ability to withstand the

gradual wearing away of the outer metal, as the rope runs across sheaves and hoist drums.

Wire ropes may be of open spiral or lockedtypes.

Open spiral ropes have round wires withround strands laid helically overa centre.

Half-locked and full-locked coil ropeshave a centre made of round wiresbut these ropes have one or moreouter layers made of Z shaped profilewires. This construction prevents thepenetration of dirt and water and it alsoprotects the loss of lubricant.

Another very important advantage isthat the ends of a broken outer wirestays in place and cannot leave therope.

The Importance of Lubrication in Wire Ropes

• All wire ropes require consistent maintenance and proper care in order to remain in good condition and functionally efficient.

• During operation the strands that make up a wire rope are under constant stress and strain.

• The strands constantly rub against one another causing friction.

• The friction cause strands to wear.

•The friction heat causes oxidation resulting in high internal core temperatures which in turn accelerates rusting and causes premature rope failure.Proper lubrication reduces the friction, thus resulting in the full and functional

lifespan of the rope. Besides, the lubricant also provides total protection against

corrosion.

Wire Rope Lubricants

• The lubrication treatment during rope manufacture provides the finished rope with protection for a reasonable period of time which sustains for the early stages of the rope's working life. However this lubrication has then to be supplemented, at regular intervals depending upon the type of rope application.

• In most cases it thus becomes necessary to either thoroughly clean the rope or to use a high pressure lubrication device which forces new lubricant into the rope

• LETS NOW SEE A SPECIFIC CASE STUDY … 11

Wire rope lubricants should perform two principal functions:

1. To reduce friction as the individual wires move over each other.2. To provide corrosion protection and lubrication in the core and inside wires and on the exterior surfaces.

KOLKATA

CHENNAI

MUMBAI

DELHI

Soon after India’s independence, the exploration for uranium ore began in order to meet the requirement of uranium for the country’s nuclear programme.

INDIA

RANCHIDHANBAD

JAMSHEDPUR

GHATSILAJADUGUDA

BiharU.P

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ORISSA

Wes

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A CASE STUDY IN UCIL’s JADUGUDA MINEAn ISO 9001:2008, ISO 14001:2004, IS 18001:2007 company

The first find of Uranium was made at a place called Jaduguda, in Jharkhand (then Bihar)

URANIUM MINE AT JADUGUDA JADUGUDA MINE, located in the forested

tribal belt in East Singhbhum district of Jharkhand, is the FIRST URANIUM MINE OF THE COUNTRY

It was initially developed to a depth of 315m in the FIRST STAGE and then deepened to 640m in the SECOND STAGE. Today after THIRD STAGE of sinking, it is 905m (almost 3000 feet) deep– making it one of the deepest mines in the country.

The entry into the mine is through a vertical shaft having two conveyances – a double deck cage for men & materials and a skip for ore transportation. Both the cage and the skip are balanced with counterweights. The winders for these are housed in the 45 m high head frame on surface. A second underground sub-vertical shaft from 555m depth then provides entry till the final depth of 905m.

Jaduguda Winding SystemThe winding system at JadugudaMine comprises of motors,gearboxes, drums, brakes etc allhoused in a 7.5m diameter and46m high concrete tower (headframe) located exactly above the5m diameter mine shaft. The controlroom is located on the surface.

WIRE ROPES IN JADUGUDA SHAFT WINDING SYSTEM

The cage (passenger compartment)movement is by 3 numbers of 20 mmdiameter locked coil wire ropesbalanced with one 41mm tail ropewhile the skip travel is by 4 Nos. of 20mm diameter full locked coil wireropes & two 34mm tail ropes. Thecage moves on rails while the skip andboth the counterweights travel onguide ropes.

There are a total of 8 nos. of guideropes all of 41mm diameter, halflocked construction and lengthsvarying between 630 to 635 m.

Wire Ropes in Jaduguda Shaft

GUIDE ROPESGuide rope

Tensioning Weights

Guide ropes are used to ensurethat the conveyances travel along afixed path from the shaft top to shaftbottom safely -without fouling orcausing any damage. Rope guides provide minimal frictional resistanceto the travel of the conveyance withlesser fatigue and tensile stressesbeing imparted to the winding ropes.

Guide ropes are fixed at the shaft topand tensioned by attaching weights atthe other end located near theBottom of the mine shaft.As guide ropes have to be kept intension a value of about 10 kN/100 mof depth is generally applied.

GUIDE ROPES FUNCTIONSGuide ropes are used to ensurethat the conveyances travel along afixed path from the shaft top to shaftbottom safely -without fouling orcausing any damage. Rope guides provide minimal frictional resistanceto the travel of the conveyance withlesser fatigue and tensile stressesbeing imparted to the winding ropes.

Guide ropes are fixed at the shaft topand tensioned by attaching weights atthe other end located near theBottom of the mine shaft.As guide ropes have to be kept intension a value of about 10 kN/100 mof depth is generally applied.

Guide ropes are mostly of half-lock construction with the proviso that the wires of the outer layer must be of particularly large altitude because of the wear to be expected.

• Guide ropes should be lubricated in the course of manufacture with a corrosion - inhibiting grease or in some cases may be galvanised.

• The tensile strength of the wires is 1140 N/mm - 1570 N/mm .

• It is recommended that where several ropes are used the tension weights should be staggered by 5% to 10% to avoid resonance.

• Geometric analysis for the best arrangement of the guide ropes reveals that corner guides give a greater restoring moment.

Guide Ropes in Jaduguda Mine

41 mm Guide ropeshanging in Jaduguda shaft

As mentioned earlier there are of 8 nos.of 41mm diameter guide ropes inJaduguda shaft .

One end is fixed on top of the HeadFrame while the other end is tensionedby weights attached to the guide rope inthe shaft bottom.

One end is fixed on top of Head Frame

CHALLENGES IN GUIDE ROPE LUBRICATION The first major challenge - selecting the proper lubricant

The first step was to assess the properties required from the lubricant for our stationary guide ropes suspended in the shaft, in varying environmental conditions. After detailed study we came to the following conclusions regarding the properties to look for:

a) the lubricant should adhere firmly to the wires and be viscous enough to resist gravitational forces as the ropes hang vertically.b) must have water-repellent properties to protect internal and external surfaces from corrosion c) should not deteriorate with age, exposure or temperature changes, e.g. by hardening or cracking. d) The selected lubricant must be non-corrosive and stable over the range of temperatures and environmental conditions likely to be encountered and should not give rise to any by-products which could attack the metal strands.

Next, the causes of guide rope deterioration were assessed

Deterioration of Guide RopesCAUSES: The deterioration of guide ropes occurs because of two majorreasons: corrosion and abrasion.

Corrosion- causes shortened rope life due to metal loss, pitting and stress risers from pitting. Proper and adequate lubricant application in field conditions is the only way to reduce corrosive attack on the guide rope.

Abrasion- Studies revealed that in guide ropes abrasive wear occurs on the inside and outside of the ropes. The outside of the rope accumulates dirt and contaminants from the mine environment causing 3 body abrasive wear(i.e. foreign hard particles trapped between two sliding surfaces and abrading one or both surfaces or embedded in a softer surface and abrading the opposing one and thereby eroding the outer wires and strands. Abrasive wear can reduce rope diameter resulting in core failure and internal wire breakage. The solution is to apply wire rope lubricants having penetrating properties to reduce abrasive wear inside the rope and also wash off the external surfaces to remove contaminants and dirt.

Zeroing on to the proper lubricantWith the above information detailed discussions were held with technical representatives of two leading Indian oil companies whovisited our site & saw the application. After study one companysuggested the use of a heavy duty grease while the other proposedusage of a heavy bodied, adhesive type black lubricant (used for opengears).Samples were supplied by both the companies and the respectivelubricant was applied on different guide ropes.While the application of the heavy duty grease was comparatively easybut after a few days it was found that some areas of the rope wereexposed with the grease having been washed off. In the second case (while the high viscous and tackability properties made applicationrather difficult) but even after six weeks the lubricant had largelyretained its location with only a minimal amount of downward travel.

The final selected lubricant• A small sample of this lubricant was scraped off the rope and given

for testing. Test results revealed only marginal differences in kinematic viscosity and specific gravity with external dust particles clinging on to the rope surface but without any internal ingress.

• This lubricant was procured, applied on all the 8 guide ropes and kept under close visual inspection. With no negative fallouts over a period of time, this lubricant became our standard lube for all guide ropes.

• The lubricant is a heavy bodied, adhesive type black bitumen based lubricant which (as per data sheets) has been formulated using extremely refined steam cylinder oils having good thermal and chemical stability. It has a kinematic viscosity of 200-250 cSt at 40 °C.

• The bituminous component has been providing a long lasting lube film and excellent adhesiveness with minimal throw off. This lube has protected the guide ropes against rusting and has provided effective resistance against water, which drips in the shaft.

• The lubricant’s adhesive property has resulted in applications in small quantities thus actually reducing lubrication cost.

CHALLENGES IN GUIDE ROPE LUBRICATION The second major challenge - selecting the proper

method of application

The proper and even application of very high viscositylubricants on guide ropes is a problem being faced in alldeep mines. The major problem is that unlike other ropes which

travel,guide ropes are stationary and run all through the shaftdepth. Thus either there should be a device whichcan travel along the rope and lubricate automaticallyor else a person/s should travel on cage or skip tops toaccess the guide rope and lubricate the ropes manually.

Mechanical Method of Application.

Over the years we at UCIL have tried outsome mechanical methods of application. A short write-up on a mechanical methodtried out a few years ago is explained andthe reason why it had to be abandoned.• The system comprised of a high pressure air

pump with flow controlling valve, ball valve, drum cover, flow control value, follower plate, flexible hoses, lubricating chamber and anchoring chains.

• The air supply to the pump had to be atleast 8 bar. Split seals were fitted around the rope and clamped in placed by the two halves of the lubricating chamber. The unit was anchored by two chains to some stationary object. The pump was started and the wire rope was to be pulled through the Lubricator.

The failure of this methodThe lubricant under high pressure penetrated, cleaned and lubricated the wire

rope but it was noticed that in order to obtain total penetration through the rope the pressure required in the chamber was actually much higher - around 20 bar.

The reasons for the failure of this method was as follows:• In this system the rope had to be pulled through the lubricator for lubrication

to take place. This was not possible in case of guide ropes which were fixed and stationary. An attachment was thus made by fixing the lubricator to the edge of the conveyance with the seals clamped to the adjoining guide ropes and the conveyance was made to move downwards or upwards. However this method was only possible till a few meters from the ground level as with the compressors being located on the surface, it was impossible to supply high pressurized air to the pump due to hose length restrictions.

• With such high pressures being encountered it also became a potential risk for persons standing on the mine conveyance very close to the machine in a restricted area and operating the lubricator.

Manual LubricationThus in spite of the generalassumption that lubricating withthe aid of brushes, rags, gloves or byother means is costly, risky and notvery effective, the good old handapplication method has still proved tobe the most convenient in UCIL.

If the rope is dirty or hasaccumulated layers of hardenedlubricant or other contaminants, it iscleaned with a wire brush and solventbefore re-lubrication. The wire rope isthen dried and lubricated immediatelyto prevent rusting.

Precautions while lubricating guide ropes

Although the lubricant does not containany hazardous ingredient but mild eyeand skin irritations have been observed attimes.

As such all personnel involved in lubricationwear nitrile rubber gloves, aprons, rubbershoes and goggles (although due to humidunderground conditions these have to beoccasionally cleaned as they become foggy.

Lubrication is carried out by at least twopersons on a rotational basis who areadvised to take occasional breaks at a freshair base.

WRAPPING UP….• Proper lubrication of guide ropes with the correct lubricant can

result in the long life of guide ropes and prevent unforeseen problems, provided correct maintenance practices are followed and regular inspections are carried out.

• Hence all personnel involved in lubrication should have a passion to perform without considering the job to be dirty or demeaning.

• Believe me its easier said than done & its for those occasions that the passion to love one’s job – should be instilled.

SO ITS VERY IMPORTANT-TO TEACH ALL PERSONNEL TO LOVE THEIR JOBS

Remember the famous words of Mother Teresa when she said:

“God doesn't look at how much we do, but with how much love we do it”

THESE WORDS ECHO THE ESSENCE OF PROPER LUBRICATION

THANK YOU