belt conveyor project 03-07-2013

7/27/2019 Belt Conveyor Project 03-07-2013

http://slidepdf.com/reader/full/belt-conveyor-project-03-07-2013 1/57

CHAPTER-1

INTRODUCTION OF BELT CONVEYORS

“PREVENTION IS BETTER THAN CURE”. It is moretalked about than practiced.It is economical, peaceful,prudent and safe to

prevent an untoward happening and thus prevent loss than to bemoan the

loss, trying to investigate the cause/s, the after-effect and invent cure: for

accidents are caused and do not occur as a matter of course.Even with the

advancement of modern technology, in different disciplines wherein various

types of cures are available for various ills and shortcomings, Cure is only a

cure and does not and cannot restore the original status and /or shape prior to

the happening.There are side-effects which need greater caution and after-

care, after the cure.Thus ,the emphasis for “prevention”than attempt a “cure”after the event.

Loss may be in manpower, material and money. In an

organization, loss due to breakdown has been worked out with

precision.Whenever a breakdown occurs not only that equipment is not

available till it is restored, but a substitute has to be arranged,if it is a

continuous process, involving loss due to extra man-power, time and money in

arranging the substitute or alternative arrangement.

Then, we have consider, how we go about preventing a loss due to accident.It

is by adapting “Safety Measures” and following “Safety Principles” for

“Safety is First.” “Safety” is first and foremost and is always first and never

be relegated to a second position.”Safety” is not only first and is essential in

every walk of life and situation, be it in the Field of Factory,Office, Household

including Kitchen and Bed-room, for lurks in every corner and every

moment.

Belt conveyors are perhaps the most common,economic and efficient means

for continuous movement of materials between fixed points. These are in use

in many industries and establishments for conveying a wide variety of materials ranging from small parcels to ore in bulk.Their size varies from a

few meters in a warehouse to several hundred meters in a mine.

Like any other transmission machinery, belt conveyors present

risk of injury. Experience shows that conveyor accidents often involve fatal or

very serious `injuries and severe damage to property. As conveyor systems are

vital links in the production chain, their stoppage due to accidents or



breakdowns can lead to serious business interruption loss as evidenced in

some of the fire incidents in power plants and elsewhere.

In bulk material transportation systems, excessive spillage represents

wastage of material and can present occupational safety and healthy pro

CHAPTER-2

Hazards in Belt Conveyor Systems

Most accidents in Belt Conveyors occur when hands of persons working on

the conveyors come into contact with the moving belt and the inadequately

guarded nip points and pinch points near pulleys and idlers.Such accidents

are usually severe,and sometimes fatal too.Mechanical failure of conveyor

components due to deficiencies in design, operational and maintenanceprocedures also render the conveyor systems hazardous.Spillage of material,

fires from friction, overheating,static charge and other electrical sources are

the other important hazards encountered in belt conveyor system.

CHAPTER-3

DESIGN AND CONSTRUCTION

For good performance, the Conveyor belt chosen for installation shouldhave adequate tensile strength, wear resistance,frictional characteristics,

flexibility and stretch.For special applications, the belt may require resistance

to heat, oil, water, chemicals and static charge.

Conveyor belts are generally constructed of a fabric core which must be

strong enough to withstand and transmit the tension necessary to operate the

belt.Use of multilayers or reinforcement with metal strands or mesh can add

to the strength of the fabric core.The fabric core is then either covered or

impregnated with appropriate flexible compound,natural or synthetic, and

further strengthened as necessary with suitable wearing faces made again of natural or synthetic compounds.For example, a 6 ply nylon carcass with top

and bottom rubber will suit bumpy and abrassive materials,whereas a 4-ply

cotton carcass will be suitable for warehousing operations.Guidance on the

most suitable type of belt for handling the required material is available from

the manufacturers of conveyor belts and should be sought for.



The belt loading system should fill the belt with minimum spillage of excess

material.The design criteria should take into account the quantum of spillage,

the operating and maintenance procedures to clear the same and the

associated injury hazards.In one of the newsprint mills, the authors came

across an investigation into a fatal accident to a worker engaged for clearing

the spilled bagasse pulp and shoveling it back on to the conveyor belt, which

highlighted the design deficiency that resulted in substantial spillage of excess

burden on the conveyor which simply could not match the loading rate.

All parts of the conveying system should as far as possible meet the applicable

national or international standards.During design and construction stage, it is

necessary to adhere to the relevant provisions in the following statutes:

1.Factories Act, 1948 and the Factories Rules framed thereunder.

2.The Mines Act, 1952

3.The Indian Electricity Act, 1910.

4.The Dock Workers (Safety,Health & Welfare) Scheme, 1961.

Further by choosing critical components of latest design, it is possible to

reduce maintenance requirements of these parts. For example, self-aligning

rollers reduce the problems of belt centering and spillage of

materials.Permanently lubricated idlers, pressure oiling, or automatic gravity

lubricators can eliminate the need for periodical lubrication and the

possibility of injury to the personnel.

SAFE ACCESS:

Walkways on the sides of the conveyor facilitate inspection,

repair and maintenance.Many conveyors run above ground level and should

have gangway all along the length.The gangways should have chequered plate

flooring to reduce risk of slipping and guarded by standard railing and toe

boards.For access to the gangways, stairways are preferred to fixed ladders. If

portable ladders are used they should be equipped with protection devices

against falls. Such devices include anchoring arrangements to prevent lateralmovement of ladder, antislip rubber shoes for stiles, etc.

Plant personnel may have to cross the conveyors to reach work place on the

otherside.Crossover bridges provided at short distances can reduce the

temptation of employees to take a short cut from under the conveyor carriage

or over the conveyor belt.Accidents involving persons falling off the crossover



bridges are also reported.To prevent such accidents, the platform and

stairways of the crossover bridge should be non-slip type having hand rails

and toe boards.A top rail at one metre height,an intermediate rail at 66 cm

height and a toe board of 15 cm height from the safety requirements for

stairways and work platforms or passageways at heights.In conveyor tunnels,

adequate drainage should be maintained to drain out the rain water and

underground water seeping through the tunnel walls.

For safety of personnel working in conveyor enclosures especially at

remote, elevated or underground enclosures, emergency exits should be

provided and located conveniently to facilitate evacuation in the event of

fire which generally spreads along the conveyor and also generates heat

and smoke that obsecures the vision.

CHAPTER-4

ELECTRICAL EQUIPMENT AND SAFETY DEVICES:

The electrical equipment and wiring for the conveyor systems should

conform to the statutory provisions and codes of practice.Whenever,

bulk material is conveyed, the dusty atmosphere around warrants use of

dust-tight electrical motors, switches and fittings.Fuses,relays, overload

protection devices should be incorporated in the control systems.The

overload device may be arranged to shutoff driving power may be

considered for misalignment of belts also.By passing or sort circuiting of

the above devices can create serious fire hazard.The need for periodicinspection of these devices for reliable operation is obvious.

All starting and stopping switches should be positioned in a convenient

location so that the operator can see as much of the conveyor as

possible.These start-stop devices should be marked clearly and kept free

of obstructions.

Guards:

All moving and power driven parts of the conveyor equipment should

be guarded. This is a statutory requirement under Factories Act and the

Rules. In general, guards are required for all accessible moving parts of

conveyor system. These include the moving belt, motor-gear box

couplings, tail and head pulleys and tension pulleys. The guards should

be sturdy enough and should withstand the vibration. They may be of

sheet metal or expanded metal, but as far as possible, the guards should



be so designed as not to hamper maintenance, repair or cleaning jobs.

For example, a guard should be positioned so that spillage falls outside

the guard and can be easily cleared away without exposing the

personnel to risk of injury.

For tail and head pulleys and other vulnerable parts, guards should beinterlocked with the drive mechanism such that it is not possible to have

access to the mechanism unless the machine comes to a stop. One such

method is to have doors that open after predetermined time delay after

switching off the machine.

The underside of an overhead conveyor section passing over an aisle or

passageway should have sheet metal guard if there is a possibility of

materials falling off the running belt. Such a guard can protect the

passers from the sticky material that may fall off the return belt

portion.

Control & Disposal of Spillage:

Material spilt from conveyor belts represents wastage and injury

hazard.Bulk materials such as Urea & hygroscopic and render the

neighbourhood of conveyor slippery.Spillage of combustable materials

like wood chips and coal enhances the fire risk. Excessive spillage

warrants deployment of manpower to put back the spilled material on

the running conveyor belt to reduce the chance of materials falling off

the belts. These can be conveniently erected at the conveyor loadingpoints to retain in place the material that falls on the belt from the

loading chutes. When properly fixed,they reduce spillage of materials

substantially.

For proper working, the skirt should be made of solid rubber. Use of

discarded, old conveyor belts for the purpose should be avoided. Where

metal skirts are used, they should either have sufficient clearance from

the belt surface or be provided with rubber strips at the point of contact

with the belt. In the absence of this precaution, the metal skirt may

damage the conveyor belt.

The spillage along the conveyor and the carry-over at the end of the

conveyor, present problems of jamming of idlers and heating of

conveyor belting. Where it is not possible to reduce such carry-over or

to clear the same by shoveling it back onto the belt, arrangements

should be made to sweep it into a terminal hopper. This is particularly



important at transfer towers or other elevated platforms which can

accumulate substantial unwanted spillage with no easy way of removing

it to ground level. Sweeping it into the surrounding air accentuates the

dust nuisance. A hopper and a chute pipe to return the spillage from

the elevated places either to the conveyor system or to a closed container

at ground level would prove to be convenient and effective spillage

disposal system.

Brakes:

Brake is expected to stop the conveyor in an emergency and should be

capable of sustaining 25% excess of the peak load when applied. Back

stop devices are provided on inclined conveyors to prevent the belt from

running backwards when stopped on load. Ratchet and pawl and

differential band brake are the two types of backstop devices normally

provided on conveyors. These require regular inspection for properworking.

Tensioning Devices:

Tensioning devices are provided on conveyors for three reasons. To

provide adequate belt tension, to prevent belt spillage and to

compensate for stretch or shrinkage. For small conveyors (less than

50m), tension adjustment is done manually. The tail pulley and shaft

should be properly guarded while adjusting the take-up manually when

the belt is running.

On large conveyors, automatic adjustment of belt tension is achieved by

gravity counterweights or pneumatic/hydraulic tensioning

arrangements. In the event of belt breakage the take up pulley and the

counter-weight would drop down. To avoid possible injury to work men

in the neighbourhood, it is necessary to guard the entire take up

assembly by means of a wire mesh.

Cleaning Devices:

Belt cleaning devices are provided to reduce the accumulation of

spillage along the length of the belt on return side and to keep the belt

clean. These cleaning devices or scrapers as they are sometimes called,

also reduce the wear and tear of the belt.

Rotating brushes, scraper blades and water sprays are the three basic

devices commonly used. Rotating brushes are used for removing damp



and sticky material from belts operating at high speed (1000 to 1500

rpm). For good results the scraper blade or the rotating brush should be

placed behind the pulley at a point where the belt leaves the pulley.

Water jet by itself is not considered effective. The jet can be used in

conjunction with the rotating brush.

Automatic self-aligning troughing and return rollers may be provided

for belt centering. Outboard guide rollers fixed to the self-aligning

frames cause the idlers to swing on contact with belt edge. These

aligning rollers are effective in controlling spillage when provided on

long conveyors. It is recommended that a distance of 40-50m be

maintained between two self aligning frames.

Fire Prevention and Protection:

Belt fires often prove costly. They not only damage or destroy the belt,drive motors, speed reducers, electrical cables and structural parts but

also cause loss of production till the conveyor system is brought back

into operation after necessary repairs or replacement. In a power

generation plant, a conveyor belt fire was responsible for non-

availability of electric power supply to consumers for several weeks.

Further a fire in a running conveyor transporting materials like coal

can be very dangerous because coal presents a potential fire hazard due

to spontaneous ignition. The main sources of ignition in conveyor belts

are friction between the belt and jammed idlers, belt slippage at the

drive drum, materials carried by the belt(as in sinter plants), welding

and cutting sparks and static charge accumulation on the belt.

Conveyor belt fires and the associated losses can be controlled by

providing fire resistant or non fire propagating belting, flame-proof

motors in hazardous areas, provision of oil seals in speed reducers to

avoid oil leakage, effective spillage, removal and disposal procedures,

hot work permit system for welding or cutting work on, near or over the

conveyor belts and frequent fire watch.Good operating and

maintenance procedures obviously reduce the chance of outbreak of

fire,especially due to friction.

Static electricity collectors help to reduce fire and explosion hazards on

belts that handle flammable dusty materials. Tinsel or needle point

static collectors can be placed close to the pulleys and idlers which can

be grounded through carbon or bronze brushes on the shaft. Bonding

and grounding of drums and pulleys is also necessary.



The effective extinguishing medium for fires involving rubber belt is

water in spray form. Automatic sprinklers or water spray protection

along conveyor structure would prove useful especially if the conveyor

belts are not fire resistant type.

Small bore hose reels (1 ½”) or hydrants with landing valves at variouslevels may be provided to reach any part of the conveyor system.

In pulverized coal conveyors it is advantageous to provide an automatic

fire detection and alarm system coupled with a water spray

arrangement along the conveyor and a water mist curtain at the head of

conveyor where the material leaves the conveyor and enters into

transfer towers. In enclosed coal conveyors, provision of carbon dioxide

nozzles for manual or automatic operation may also be considered. It

should be remembered that fire protection in belt conveyor installations

is a specialist ,s job that requires careful consideration of thecombustible nature of the material conveyed and of the belt material,

the conveyor speed and the rate of application of the extinguishing

medium for effective fire suppression.

In the context of fire safety also, the utility of pull-cord to stop the

movement of conveyor and consequently to reduce the speed of fire

spread cannot be over emphased.

Sometimes, conveyors may have to pass from one section to the other

separated by a fire wall. It may be possible in certain situations to runconveyor through the roof over the fire wall. Otherwise, an

automatically closing fire door has to be installed in the portion of the

fire wall through which a conveyor may pass. A careful design of the

controls is necessary to ensure that conveyor is stopped at a position

where material on the conveyor will not block the fire door from

closing. Alternatively, water spray protection for conveyor opening in

fire walls may be provided.

Dust control

Dust extraction devices should be installed where the dust of material being

conveyed creates a fire hazard, toxic effects or a nuisance problem in theneighborhood, proper enclosures in conjunction with mechanical ventilation

system at transfer points, bunker floors and near surge bins would reduce this



hazard. In some situations where the nature of material permits wetting, by water

spray system could also effectively control the dust emission.

Miscellaneous

The equipment should be clearly visible, and hence permanent lightingshould be provided bright enough and properly distributed in all theconveyor gantries, tunnels and pits.

Operational Precautions Overload or interlocking devices should never be bypassed.

Good housekeeping enhances safety and minimizes the risk of fire. Allareas especially those surrounding the conveyor drives, walkways, safety

devices and controls, should be kept free of spillage of materials being

conveyed, unused equipment components and other obstacles. Dustdeposits, oily rags, cardboard packagings, paper wrapping materials, cansand drums of lubricants should not be allowed to accumulate near conveyors

in view of their fire hazard. All weeds, bushes or trees should be clearedfrom underneath and for at least 25 feet from both sides of conveyers‟

supports.

Oiling and lubrication should be done after stopping the conveyor unlessthere is an arrangement which does not require an oiler to come enclosed

proximity to moving parts. Further no adjustment or repair should be made

while conveyor is in motion. Operating personnel and cleaners should avoideven minor repairs on a running conveyor. Repair and maintenance preferably should be left to maintenance department.

Riding on conveyors should be prohibited and this prohibition enforcedstrictly

Effective supervision in necessary to ensure adherence to safe practices and

to correct deviation before accidents occur.

Conveyors should not be overloaded above the design parameters.Conveyors operators should wear protective helmet, safety shoes and close fittingclothes during operation. Innumerable accidents took place when loose clothing of

workmen entangled with rotating or moving parts of the conveyor system anddragged the workmen into dangerous pitch points and interspaces between

conveyor moving parts. Most of such accidents turn out to be fatal or serious. In a paper mill, a worker engaged in collecting the spilled bag asset from a conveyor,



lost his life when his dhotis got entangled with an idler and dragged him forward

on to the moving conveyor belt.

Conveyors should not be started without warning men who might be attending to

repairs or lubrication of parts. The warning should preferably be an audible alarm

given through public address system. In modern plants, closed circuit televisionsystem with screens grouped together in the control room gives the operator in thecontrol room a view over the entire length and branches of the conveyor system.

While loading the conveyors or removing materials workers sometimes stand on

the supporting frames of conveyors. As the workers may slip and get caught in theconveyor belt, suitable platforms should be provided for the purpose.

Inspection and Maintenance Precautions

A standard preventive and scheduled maintenance programmed should be

developed for all conveyor parts along with an inspection checklist. Initially, themaintenance schedule should be drawn up based on manufacturer‟s

recommendations and later modified based on experience on behavior of the

equipment under the conditions of use. The observation during the inspections andthe details of repair/maintenance work carried our should be recorded for reference

and analysis. For example, the date of replacement of conveyor belt, the dare of jointing, the date of replacement of idlers, etc., would be useful, in review and

modification of maintenance schedules based on experience. Such data would also

help to indentify parts that suffer abnormal wear and tear or exhibit abnormal

behavior and to investigate into the reasons for the same.

Belt joints should be inspected frequently and the conditions of the joints should berecorded. In case of steel cord belts, the length of the joint should be measured and

recorded every year. 2 to 3% increase in the length of the joint indicates imminent

failure of the joint. Hence rejoining of the belt may be undertaken after detailed

examination, if necessary.

Motors when meggered once in every 6 months can provide a valuable earlywarning of failure. Hence periodic resting of motors may be incorporated in the

inspection schedule. Motors require regular cleaning to remove accumulation of dust which restricts cooling and leads to dangerous overheating.

Other parts of the conveyor system that need specific attention during maintenance

are idlers which may wear flat by belt friction in the absence of free rotation andthe gravity take up unit that may “bottom-out” with belt stretch or spillage



accumulation under it. Checking these parts as also the belt alignment periodically

is important from the point of view of fire safety also.

The inspection and maintenance schedules should also include periodic checking

and cleaning of water spray nozzles and regular resting of the entire fire protection

system.

Attention should be paid to lubrication of conveyor part. It is important to use the

appropriate grade of lubricant for heavy duty gear boxes and motors based onmanufactures‟ recommendations. Permanently lubricated idlers are of advantage

in this context.

Inventory management of critical parts like belts, pulleys, bearings, etc., assumes

great significance in this context. Replacement of worn-out parts in time not only

reduces the down time of conveyors but also the risk of accidents significantly.

Often, safety is compromised by continued use of workout or broken downequipment because of no availability of suitable spare parts. Safe systems and procedures for maintenance are also important. How work permit system for

welding or cutting work on or around belt conveyors, electrical work permitsystem for protection against electric shock and accidental starting of conveyor

during the currency of the maintenance work, are some of the important elementsof safe maintenance system.

Before commencing any maintenance work on belt conveyor, ensure that all

controls are switched off and locked out.

Maintenance personnel should be aware of the fire hazard with the clanging fluids

used in belt splicing and jointing work and fire prevention measures should betaken as required.

The maximum tension rating for the belt recommended by the manufacturer should

not be exceeded. Use of snub pulley under the drive pulley without increasing thetension of the belt.

Training and Education

It is common knowledge that causes 0f most accidents can be attributed to humanerror which in turn can be traced to lack of skills, knowledge and positive attitude

to safety. Hence it is important that all those connected with conveyor operationare trained not only in safe operating procedures but in their attitude to work

safety.



Every operator should understand the method of starting and stopping, hazards

likely to arise in operation, the utility of guards and safety devices the need toreport malfunction or non-functioning of any equipment and to avoid short cuts.

They should be made aware of the nearest fire exits, communication facilities and

the fire fighting techniques.

Operator training in the backdrop of safe systems, procedures and environment is bound to enhance life of plant and equipment, reduce down time and of course

improve the standard of safety.

CHAPTER-5

STATUTORY PROVISIONS SPECIFICALLY APPLICABLE TO

CONVEYOR SYSTEMS

Dock workers (Safety, Health & Welfare) Scheme, 1961.

1. Conveyors shall be of sound material, good construction and of sufficientstrength to support safety the loads for which they are intended and shall be

kept in good repair.

2. i) Conveying machinery shall be so constructed and installed as to avoid

hazardous points between moving and stationery part or objects.

ii) When a passageway is adjacent to an open conveyor, a clearance of atleast 90cm (3 feet) shall be provided.

3. When dock workers have to cross over conveyors, regular crossing facilities

affording safe passage and adequately lighted shall be provided.

4. Might pass beneath them, sheet or careen guards shall be provided to catch any

material which might fall from the conveyors.

5. Power-driven conveyors shall be provided at loading and unloading stations, at

drive and take-up ends, and at other convenient place, with devices for stopping theconveyor machinery in an emergency.

6. Adequate fencing shall be provided at transfer point.

7. Conveyors which carry loads up inclines shall be provided with mechanical

devices that will prevent machinery from reversing and carrying the loads back towards the loading point in the event of the power being cut off.



8. Where two or more conveyors are operated together the controlling devices shall

be so arranged that no conveyor can feed onto a stopped conveyor.

9. Where the tops of hoppers for feeding conveyors are less than 90 cm (3 feet)above the floors the openings shall be adequately guarded.

10. I) where conveyors extend to points not visible from the control stations, they

shall be equipped with gongs, whistles of signal lights, to be used by the

operators before starting the machinery so as to warm dock workers who might be in positions of danger.

ii) Similar provisions shall be made where necessary to enable the dock

workers to communicate with the operator.

11. Conveyors shall be provided with automatic and continuous lubricationsystems, or with lubricating facilities so arranged that oiling and greasing can

be performed without the oilers coming within dangerous proximity to moving parts.

12. Conveyors shall be thoroughly inspected once in every three months.13. Dock workers shall not ride on conveyors.

14. Belt conveyors shall be provided with guards at the nips of belts and drums.

15. Intake openings of blowers or exhaust fans for pneumatic conveyors hall be

protected with substantial metal screens or gratings.16. Frames of gravity rollers and chutes shall be kept free of splinters, sharp edges

and rough surfaces.17. Gravity rollers and chutes shall not be used for the passage of dock workers.

18. Sideboards of chutes shall be of sufficient height to prevent cargo from fallingoff.

*********



CHAPTER-6

LIST OF INDIAN STANDARDS

BELT CONVEYORS

1. IS: 1891 - 1978 (Part 1) : Rubber Conveyors and Elevator belting

General Purpose belting

(Part 2) : Heat Resistant belting

(Part 3) : Oil Resistant belting

(Part 4): Hygienic belting

2. IS: 3181 -1978 Fire – Resistant Conveyor belting for under-ground

use in Coal Mines.

3. IS: 4240 - 1984 Glossary of Conveyor terms and definitions.

4. IS:4776 -1977 (Part 1) Troughed belt Conveyors for surface

installation.

(Part 2) Troughed belt Conveyors for underground

installation.

5. IS : 6687 -1972 Code of Practice for selection, storage, installation and

maintenance of conveyor belting.

6. IS : 7155 -1974 Code of Practice for Conveyor Safety

7. IS : 7465 -1974 Portable and mobile and troughed belt Conveyors.

8. IS : 8531 -1986 Pulleys for Belt Conveyors

9. IS: 8597 -1977 Flat Belt Conveyors

10. IS: 8598 -1977 Idlers and Idlers sets for Belt Conveyors

11. IS: 9295 -1983 Steel Tubes for idlers for troughed Belt Conveyors.

12. IS: 9405 - 1980 ( Methods of kest of Conveyor Belt fasteners

13. IS: 11507 -1985 Synchronous best drive Pulleys.

14. IS: 11592 -1985 Code of Practice for selection and design of Belt

Conveyors.



OTHER CONVEYORS

15. IS: 5895 -1985 Steel Roller Conveyors

16. IS: 7423 - 1974 Dimensions for Apron Conveyors

17. IS: 8599 -1977 Recommendations for selection of Apron Conveyors

18. IS: 8646 - 1977 Scraper Conveyors19. IS: 5563 - 1985 Screw Conveyors for Industrial use20. IS: 5626 - 1970 Shackle type connecter units for high tensile steel chain for

conveyors in mines

21. IS: 8723 -1978 Dimensions for Vibrating Conveyors and feeders with

rectangular or trapezoidal trough22. IS: 7439 -1974 Dimensions for Aeroslides

23. IS: 5972 -1970 Glossary of Pneumatic and Hydraulic Conveyor terms anddefinitions

24. IS: 8647 -1977 Design Criteria for Pneumatic Conveying systems25. IS: 6834 -1973 Conveyor chains, Chain – wheels and attachments.

(Part) : Chains(Part 2) : Chain Wheels

(Part 3): Attachments.

CHAPTER-7

PREVENTION OF ACCIDENTS DURING BELT CONVEYORSMAINTENANCE

The development of any country depends on its industrial potential.

Industrially, our country is making rapid progress. Materials handling

activity in organisations is also picking up greater momentum and

every industry is trying to have maximum output with faster and

quicker methods. Amongst the materials handling equipment, the belt

conveyor system has the advantage of simplicity in construction, high

efficiency and low frictional loss resulting in low power requirement

and economy in upkeep.

The advantages of Belt Conveyor haulage have transformed what might

be called “Mechanical Curiosity” to an indispensible component in the

haulage system with a reputation for genuine usefulness in an ever

widening field of application. Conveyor belts came into existence

around 1868 when LYSTER, an English Engineer described to the



British Engineering Society his work on conveying bulk materials by

endless belts made of two pulleys of rubber faced canvass. This mode of

transport which was confined to a few thermal stations and cement

plants is increasing in its use in ports, open cast and underground

mines, steel plants and in various other fields.

The Conveyors may be horizontal or inclined or a combination of both

and can be arranged to convey material either up or down an incline.

There are two main types of conveyors; (1) Flat type-generally used for

bags, bottles, boxes and other packaged materials,widely used in

production units although under certain conditions, loose materials in

bulk such as soap may also be satisfactorily handled; (2) Trough type

which enables the loading capacity to be increased by 60% without

danger of spillage and is suitable for almost all bulk material in a dry,

damp or semi-wet condition.

The basic components of any Belt Conveyor are (1) Belt; (2) Carrying

Idlers; (3) Return Idlers; (4) Head-end, Tail-end Snub Pulleys; (5)

Drive mechanism. Cost wise, belting alone forms nearly 35 to 40% of

the total cost and the other major share is the Conveyor rollers.Of the

remaining components, the critical ones are parts of conveyor drive like

Pulleys, Gear boxes, Couplings, electrical motors and other components

and fixing arrangements.

Visakhapatnam Port, one of the major Ports in India situated in East

Coast,has first installed the Conveyor system in 1965 for exporting Iron

Ore to Japan. Intially started with a loading rate of 2600 tonnes per

hour its capacity increased to 3200 tonnes per hour. As the demand has

further increased and the need to have a deep draft vessels along side

the berth has been felt, the outer harbor came into existence in 1976,

with a higher capacity loading of 8000 tonnes per hour. The whole

system is divided in two parts as Receiving system and Shipping system.

The Receiving system comprises of wagon tipplers and stackersconnected by Conveyor system, for off-loading the ore from the wagons

mechanically and to stockpile in stack yards with the help of stackers.

All the Receiving system Conveyors are 1200mm wide steel cord

conveyors and a few fabric belts. The shipping system comprises of

Bucket wheel Reclaimers and a shiploader, connected by 1600mm wide

steel cord conveyors. During shipment the ore is reclaimed with the help



of reclaimers and traverses a distance of about 5KM in different belts,

finally

off-loads into the ship.

Totally about 20KM of belting is installed for the various operations. It

is a herculean task to maintain this conveyor system which will be

working round the clock all the 365 days of the year. Some conveyors

are at an elevation of 10-20 metres. All the belts are interlocked and any

weak link in the chain will bring the entire operation to a grinding halt

causing appreciable loss. If the shipment is not done in time, heavy

demurrages have to be paid and the prestige of the country is involved.

To meet the export commitments effective maintenance of the conveyor

system is to be carried out in an effective way. Inspite of several

protective devices in-built in the system, accidents do take place while

attending to the conveyors and have to be prevented both for the systemand personnel working near-by. There should not be any compromise in

safety aspect. Safety can; be analysed in terms of (1) System safety; (2)

Personnel safety;

Generally in a belt conveyor system a number of safety devices are

provided, such as Emergency Switches, Pull Chord Switches, Overload

Switches, Thermal fault, Belt tensions, Fluid Coupling hot, Sirens, etc.

The purpose of provideing so many safety devices is to safeguard the

system.

As far as the safety of the personnel working near the conveyor system,

is concerned, a number of provisions exist. These include cross-overs,

guards on couplings and provision of meshing around the pulleys in

drive houses, Ladders to reach elevated places for greasing the bearings,

or for condition monitoring of bearings, easy accessibility for

maintenance purposes or for changing the pulleys or idlers etc.Apart

from these, personal protective equipments like boiler suits,

helmets,goggles, gloves, aprons, safety belts, etc. also are provided to all

the employees.

Inspite of these precautions, accidents do occur on account of personal

factors. These can be controlled through measures such as councelling

and educating the personnel involved.



Let us consider the accidents that happen to the system and personnel

during maintenance :-

1.Belt Jointing

Conveyor belts fail prematurely due to a through cut,foreign material

piercing the belt, impact of over-sized boulders, joint failure, or

excessive wear of belt.When the belt fails while the loading is in

progress,great effort has to be put in to restore the system quickly.

People do commit mistakes in such circumstances, leading to accidents.

Case Study:-

One of the joints of the lengthiest overhead conveyor No.6 has failed

while the shipment was in progress. The belt passes through a lattice

structure gallery.After the joint was positioned for making a fresh

vulcanising joint, the staff were deployed. As it is a lattice structure

wooden planks were arranged for people to move freely and safely toattend the work. The joint was prepared by the usual procedures of

peeling, core separation, alignment matching etc.To have an

uninterrupted work and also to attend quicker, the Incharge has asked

the 3rd

shift staff to continue in the 1st

shift on O.T., even though the 1st

shift staff were available. As soon as the 1st

shift staff reported at site,

the night batch wanted to go for tea break as they had to continue to

work further.They went for tea and came back. One operator took some

more time and came late. After coming, he saw the Asst.Engineer at

spot checking the progress of work. This operator felt that he may be

questioned for late coming, tried to go to his place in another way and

kept his foot on a loose plank and fell down from that height of 10

metres. He had head injury and expired within 10 hours.

The reasons for this accident were analysed. It was purely due to not

following and adopting the basic safety principles.The contributing

factors were as follows:

(1) Anet should be provided under the gallery when vulcanising work is

in progress. In this case, the net was there.

(2) The staff should use the helmets when they are working at elevations,which precaution was not followed.

(3) Continuing the work from especially night shift to 1st

shift.

All precautions should therefore be taken before attending to

maintenance work.Several other types of accidents occur at the time

of attending to belt repaires, such as cuts and lacerations to body

while pealing of rubber due to the slippage of knife and in-eperience.



Smoking should be strictly prohibited. Uncured rubber, vulcanising

cement and other chemicals will be used for vulcanising purpose

which are highly inflammable.

Electrical short circuits, bad earthing also create sparks and cause

fires, and hence proper cables to be used and proper earthing should

be provided for machines.

2.Gear Box Maintenance

A constant watch on the gear boxes especially by maintenance

crew, is arranged because it is a vital link between the motor and the

conveyor.The oil is checked frequently and will be changed

depending on its condition.

Case Study

The maintenance staff attended for changing oil to the BoomConveyor Gear box of Stacker.They have taken clearance from all

the concerned, informed to the operator not to start the conveyor till

they give clearance and started their work. They drained the old oil

and filled the Gear box with new oil. As their work was at an

elevation of about 100 metres, the oil had to be lifted manually in

stages, with the help of cans. A worker who was actually pouring the

oil into the gear box positioned himself by keeping one leg on the

Boom Conveyor pulley and the other leg on the gear box. When the

work was in progress,the operator suddenly started the conveyor.

One person who was standing near the conveyor jumped out, but the

person who was standing on the conveyor had no chance to escape on

any side. His leg was caught in between the idlers and belt and was

cut off. The rest of the body fell down from that height resulting in

instantaneous death.

An exercise to find out causes of this fatal accident gives rise to the

following questions and many other issues.

(1) How did the operator start the conveyor knowing fully well that

the maintenance staff are working and have not returned

clearance?(2) Whether the maintenance staff have switched-off the Pull Chord

Switch and emergency switch before attending to work.

(3) Whether the Siren that is provided before the starting the

conveyor below or not or whether both took place simultaneously.

(4) Whether the Control Room Operator switched – off the entire

supply to the machine or not?



After studying all in detail, strict instructions were given to use all

the safety devices and take preventive measures like switching off

the switches etc,before attending to any work.

3.Maintenance on Idlers

Idlers form an important item in conveyor system. Stucked-up

idlers, damaged idlers and improper fixing cause damage to

belts.When the ground clearance is less, the return idlers will get

buried or jammed with heavy accumulation of slush, slurry,

dribbles and fines especially in monsoon season. This jamming

causes the belt to rub resulting in fast wear and also throws the

belt out of alignment, some times causes damages by cutting the

edges very badly and punctures, through-cuts, etc. Labour have to

be engaged for clearing these accumulations for safe running.Sometimes the work may have to be attended while the belt is

running if the accumulation is less. When it is more, the belt has

to be stopped and proper precautions have to be taken by

switching-off the switches and informing the concerned.

Case Study

The No.1 Conveyor runs through a tunnel 10 Metres

deep and comes out. As the area is a marshy area, lot of seepage

water accumulates and it is pumped out very frequently to

prevent flooding. Dust and fines mix with this water and form a

slurry that fills the whole area and causes obstruction for the

running of conveyors. The operator has to see that there is no

accumulation under the conveyors for safe running and whenever

it is there, he arranges for clearing by the labour. One day after

he reported for duty in the night shift, he found heavy

accumulation. He stopped the conveyor, switched-off the Pull-

Chord and arranged for cleaning. After cleaning, he switched on

the Pull Chord switch and gave clearance for running the belt. He

stood on the Tail pulley frame to observe the belt for any damageor rubbing. After getting the clearance, the control room operator

started the belt. The Operator who was standing on the frame

slipped and fell on the belt and crushed between pulleys and died

on the spot.



4.Pulley Maintenance

Failure of pullies due to shaft shearing, failure of welding on

the hub side, blow holes bearing failure or due to any other reason

causes heavy damage to the costly belts.

In one of the main conveyors a pulley had failed by shearing of a

shaft on one side. By the time the operato realised this and

stopped the conveyor, considerable damage had occurred. Nearly

1200 Metres length of belt was sheared-off into two pieces

longitudinally. This belt was running at a speed of 210

metres/minute. Failure of any part of the pulley causes havoc.

Conclusion:

Even though the conveyor system helps us to do faster work, we

must see that it should not cause havoc and play with our lives.

Necessary training in using the various safety devices provided

and following strictly without any hesitation or reservation as far

as safety principles and procedures are concerned, will help in

preventing the accidents to a great extent in and during the

maintenance of conveyor system.

The watch words are --- Never attempt to middle with any part

when the belt is running. Never attempt to cross the belt when it is

idle. Use always the safety equipments provided.

Life is precious, once lost cannot get back. We demand for

everything, but fail to use them. Until this concept changes, there

is no salvation. So atleast change now and use the protective

equipments supplied, follow the safety procedures and save your

precious life and agony for your family.



CHAPTER -8

TYPICAL ACCIDENTS IN CONVEYOR SYSTEMS

Unfenced Driving Drum

The belt on a recently installed conveyor at a concrete works was found to be

riding to one side and the operator made an adjustment. The following day he

went up the catwalk to examine the top driving drum and pulley and, somehow, hisright arm got caught between the belt and drum and was torn off.

As a result of the accident the man‟s employers were prosecuted for failing to

fence dangerous machinery.

A director of the company said that the conveyor had been received from the

manufacturers as a package plant complete with catwalk and ancillary equipment.

He had assumed that all the necessary guards had been fitted when the plant waserected. The drum had since been guarded and in such a way them when the guardwas opened, the electric supply to motor was automatically cut off.

Unguarded Tail-End pulley

A worker employed for cleaning of iron spillage at the dumper house of mechanical oven handling plant in a port, met with an accident. While working on

this job he slipped and was caught in between the two rollers of the conveyor. He

was taken to the hospital where he died afterwards. It was found that the two

rollers and the belt at the tail end of the conveyor on which the workers wereloading this spillage manually were neither guarded nor fenced off. The pull cord

wire arrangement f sting the conveyor was found cut and was not viable at the

point where the worker was doing the job.

Lack of Supervision

A lady worker was engaged on contract basis on the job of cleaning the coal

spillages from the mechanical coal handing plant. The plant employed a chain pulley conveyor for transferring the coal discharged from ships to a thermal power

station. While removing the spillage of coal with the help of shovels and broomsticks, the worker got entangled between the running belt and idlers of the

conveyor. On hearing her cry, the belt was stopped by a worker in the vicinitywith the help of pull cord arrangement. The lady was taken to the hospital where

she succumbed to her injury.

Lack of safety consciousness and knowledge about hazards on working withconveyor belts was the main reason for this accident.



Better guidance/instructions and adequate supervision might have prevented this

accident.

Inadequate Fire Protection

A conveyor belt installed at a part for transferring sculpture from the wharf to thestorage shed caught fire. As per the investigation, metal aids employed for collecting sculpture spillage might have generated the frictional heat leading to

fire. Fire fighting system provided in to port was not functioning properly andhence the fire could not be controlled at its initial stage.

Need for Scrapers

In a coal washing plant, a worker was cleaning the tail end drum of a conveyor

when he was frapped in between the belt and the drum resulting in fatal injuries.

Investigation revealed that the tail-end drum and the belt were not guarded. Inorder to prevent danger, all head and tail pulley and belt in takes should be soguarded that access to them is impossible. Guards should extend at least 1 meter

from the danger points.

Necessity of Permit to work System

Many accidents have occurred during maintenance work on or near conveyors

when a permit-to-work system either has not been adopted or has not been drawn

up with sufficient care. One such example id that of a fitter who was fatally

injured when a bucket conveyor in which he was standing suddenly started anddragged him along beneath the metal frame work of the conveyor.

This bucker conveyor was installed in the basement of a gas works and was used,

in association with belt conveyor, to transport coke from the retort house to storagehoppers. The coke had been withdrawn from the retorts earlier in the afternoon

and the yard men were working overtime in order to finish filling the storage

hoppers r eady for the next day‟s deliveries. The shift foreman sent one of his men

down into the basement to clear up spillage from the conveyors and then went intohis office to write his report.

When the man reached the basement he found that the conveyors had stopped and

that a fitter was at work repairing a chute. The fitter was standing at one side of the bucket conveyor am leaning across it to reach the chute. Seeing the man, the

fitter asked him to give him the spanner that fell down. The man searched in thecoke spillage and eventually retrieved the spanner. The man then decided that he



must get nearer to the job, so he climbed into one of the buckets and the man

handed up the tool-kit to the fitter, who put it in the bottom of the bucket.

Meanwhile the yard foreman had noticed that the conveyors had stopped although

the storage hoppers were not yet completely filled, so he met the up the staircase to

the control-point for the conveyors. On the way he met the shift charge hand (whowas responsible for the immediate control of to conveyors) and asked him why theconveyor were not running. The charge hand said that he had switched off because

the thought that the yard men had finished using the conveyors for the day. The

yard foreman then continued on his way and switched on the conveyors.

The fitter was still working from the bucket conveyor and, at the time when the

yard foreman set the conveyors in motion, he was crouching down to selectanother tool from those lying in the bottom of the bucket, He sensed what was

happening by the slight jerk given by the conveyor as it started to move. He tried to

jump clear, but lost his balance and fell. The other man quickly pressed theemergency stop but it took about 30 seconds for the conveyor to come to rest. Inthe time the fitter had been dragged along beneath the conveyor and had received

multiple injuries as he was crushed against fixed parts of the plant.

No one except the man who had gone to clear up the spillage was aware that thefitter was socking on the conveyor. The fitter himself had not taken any action to

isolate the plant, but even if he had done so there would have been no guaranteethat it would not be re-started as was indeed done by the yard foreman. The bucket

conveyor should, of course, have been securely guarded so as the prevent access toall trapping points, but the fitter would have found it necessary to remove at least

some of the guards in order to work on the chute. In such circumstances the onlyreliable way in which he could have been protected was by the operation of an

effective permit -to- work system that ensures disconnection of power supply,locking the circuit breaker or the switch, display of action notice on the switch

about the men at work and issue of a written permit to maintenance men which hasto be necessarily surrendered before the power can be switched on.

Failure to Follow Instructions

A bagging operator was operating the automate bag filling machine, which feeds50 lbs bags of polyethylene onto a conveyor belt, when he saw that a bag at the end

of the conveyor was lying angled across the idler rollers at the end of the angled position, in doing so his left foot was trapped and drawn between the conveyor belt

and the idler rollers.



The injured said that he had pushed the stop button by is operating seat before

getting on to the conveyor belt, but he thought it probable that he had not pushed ithard enough. Asked if he had been warned and instructed not to climb onto a

moving conveyor, he said that he had been warned. The committee noted that a

safety poster 1‟8” x 2‟6” was posted at eye level 12‟ away from the baggingoperating control position, warning persons not to go on conveyor belts.

The push button was operated by the committee to see if the belt would continue

moving after the stop button had been pushed; the movement of the belt after the

button had been pushed was 2”.

Evidently, the cause was failure to follow instructions. This accident has been

brought to the attention of all personnel emphasizing the danger of walking on amoving conveyor. They were reminded that severe disciplinary action may be

taken against any person disregarding a safety rule. As an engineering remedy, the

idler roller closest to the conveyor belt was fitted so that the axle of the roller restsin open ended angled slots. The existing jointed conveyor belt was also replacedwith an endless belt. It was also decided that in addition to the stop button to stop

the conveyor, the opening to the belt from the operator‟s control position should beguarded by a swing arm connected to a micro switch.

Unsafe Posture at Unguarded pulley

Conveyors were started prior to resuming normal plant operation and were

carrying reclaimed produce during cleanup. Several minutes after the conveyors

were started up, the return belt alarm sounded, indicating a conveyor belt was notmoving due to slipping of the drive pulley under the belt. The employee, who was

on the floor above, rushed downstairs in an efforts to get the return belt movingquickly to prevent the product spilling onto the floor. He mounted the steel frame,

placed one foot on the drive pulley bearing housing and pressed down on the beltwith the other floor. His floor slipped from the housing into the cramped area

between the “wing-type” drive pulley and the frame, and his ankle was struck bythe rotating pulley.

Slipping at the drive point occurred because the product dust, when moist, is

extremely slippery and because the drive pulley was placed at the lower end of the belt when originally installed due to lack of space at the head of the belt.

Also, protective guards had to been provided which would have made it impossible

for the employee to get into this unsafe position. (Investigation revealed that hehad seen others do the same thing without incident).



The employee disregarded safe work procedures which called for (1) spreading

some product dust on the underside of the belt to increase friction, and /or (2)stopping the belt and having it tightened.

As a preventive measure, the plant undertook an engineering study to determine to

possibility of changing the drive to the head of the belt. A job safety. Analysiswas also made of this operation, after which the correct procedures were reviewedwith all concerned personnel. Guards were installed on all exposed pulleys.

Employees were instructed to stop the conveyor drive when slipping occurs and to

notify their supervisor, immediately, so that the belt may be tightened properly.

Need for Lockout and Tagging

Product accumulation was being removed from a centrifuge conveyor. While the

injured employee was cleaning the drive pulley, the conveyor suddenly beganmoving and his arm was frown in between the pulley and the belt resulting in

fractures of the right radius, ulna and humorous.

The injured employee did not observe recognized good practice which requires

lock-out and tagging of the main switch before starting work on power-drivenequipment. Even though he had been talking with the injured employee just a few

minute before the accident, the centrifuge operator did not understand that cleaning

work was in progress and that it would continue. The injury occurred when he

reset the relays, which had been tripped, and started the unit in order to unload oneof the centrifuges.

Safety rules and practices must receive the full support of all employees, and strict

adherence must be required by supervision. Employee‟s hold is instructed on proper lock-out and tagging procedures, which should also be reviewed. When

men are working together, it is essential that there be complete understanding byeach person as to both the work being done and that which is planned. This subject

could be discussed at plat safety meetings.

Accident during Alignment Correction

Operator noticed the conveyor belt was running to one side tail pulley, and he

attempted to align the belt by throwing fine material between the bottom of the beltand the top of the belt idler. After throwing the fine material, has leaned over the

belt to check he alignment; he attempted to support his body‟s weight with hisright hand, and his hand slipped and was caught between the belt and an idler. A



second man heard him call and pulled the emergency stop cable located alongside

of the belt. He suffered a fractured finger and abrasions on the back of the hand.

The Employee performed an unsafe act and placed himself in a vulnerable

position. All employees should have been instructed not to throw fines on belts in

order to align them. An emergency stop cable should be installed along side of thetail pulley, and a guard be placed at this location to prevent anyone from gettingclose to the roll.

Improper Design of Guard

An operator sustained a partial amputation of his finger when it was caught in a

conveyor belt drive. The injured had noticed the product conveyor belt from No.1

cooler was not moving. He reported it to his foreman, who obtained the services of

two electricians to determine if a fuse had burned out. The electricians found the

fuse to be O.K. and in checking the switch from found a load to be on the line.One of the electricians and the production shift foreman then checked out visuallythe motor for the belt drive on the conveyor. By the use of a flashlight, the two

men could tell the motor, approximately eight feet off the floor, was running but belt was slipping in the motor belt sheave.

The shift foreman explained to the operator that the motor was running but the beltwas slipping and he used a flashlight to point this out. While the operator was

obtaining a ladder for a closer look, the shift foreman hen into the bag room a few

feet away to review his production requirements and see if he could at until

maintenance arrived at 8.00 a.m. to get the unit repaired.

The operator placed the ladder and climbed up near the west side of the motor andreached his right hand behind the metal belt guard to determine if the belt was

moving. At the precise moment he touched the belt, the operator said the belt

apparently began moving and pulled his right hand toward the motor pulley. His

right middle finger was caught between the belt and the pulley, amputatingapproximately two-thirds of the distal phalanx.

Trapped by pulley and belt

A rubber conveyor belt used for handling foundry sand was cellar beneath the

foundry floor. It was used to elevate sand from the cellar floor and to deposit it ina hopper; the head pulley of the conveyor being 9ft.above the cellar floor. Access

to the head pulley was obtained through a trapdoor in the ground floor. When afoundry worker noticed some sand sticking to the face of the head pulley he

opened the trapdoor and stepped down onto part of the frame of the conveyor and



endeavourer to scrape the sand off the pulley surface while the conveyor was

running. His arm was caught between the belt and pulley but fortunately hisinjuries were not severe. Following the accident close fitting guards similar to that

already fid to the tail pulley, were provided at the head pulley.

The need for effective guarding extends dangerous parts which are accessibleduring normal working and should be provided where any work, however unusual,has to be done.

In another case a workman‟s arm was severely bruised when he was caught in the

intake of a pulley and conveyor belt while attempting to clear away sand. Theconveyor was being used to convey sand across a foundry floor. At the time of the

accident the man was standing on a pile of sand with his arm in a gap in the sideframe of the conveyor to clear sand from the vicinity of the belt tensioning device.

When the sand on which he was standing moved, he stumbled and his hand went

into the nip between the conveyor belt and tail pulley.

The guarding which was provided was not completely effective although in this

case the man obtained access to the dangerous nip by putting his arm through afairly small opening in the machine support frame. This could be a case where

partial enclosure had, to some extent, hidden the dangerous nip.

Cleaning should not have been carried out in either of these cases with the

machinery in motion.

Insecure position + Inadequate GuardingAs accident occurred on a coke belt conveyor of the trough type which was usedfor conveying coke from a hopper to a stock yard. At the retime of the accident the

plant had only been operating for a short time and there had been numerousteething troubles one of which had been the failure of coke to flow freely through

the hopper opening onto the conveyor. As a result a man had to be stationed permanently above the hopper opening to free blockages with an iron bar. To do

this he sat on an angle support adjacent to the hopper opening and while in this position his foot went into the nip between an idler roller and the conveyor belt. At

this point slipping plates were provided alongside the belt and these prevented the belt from lifting. The operator‟s foot was jammed between the idler roller and the

spillage plate. Fortunately the belt slipped on the driving drum although the drivedid pick up intermittently, driving the man‟s foot further into the nip. He was in

this position for about an hour before his shouts for help were finally heard and theconveyor stopped. He was very lucky to escape with only a severely brushed foot.



Absence of Nip Guards

A similar accident happened in a chemical works in a section of the plant involved

in the production of synthetic magnesia. In this case the belt conveyor was used to

carry magnesium hydroxide paste from a filter plant to a hopper feeding a drying

kiln. The conveyor was inclined to the hopper from ground level to a height of about 45 if. A walkway alongside the belt gave access for cleaning and greasing.During its progress up the conveyor and due to its semi liquid nature, the paste

tended to seep over the edge of the belt and to build up on the idler rollers and on

the sides of the head pulley and these deposits were removed by workers using

hand tools.

The accident happened when a worker was attempting to scrape the paste depositfrom the head pulley with the conveyor in motion. The scraper slipped and his

hand was taken into the nip between and the head pulley. He was trapped in this

position with the belt abrading his arm, for more than 10 minutes. It was foundnecessary to cut the belt and release the drum from its bearing block in order tofree him. He suffered severe friction burns on his arm and chest.

Again only one stop button was provided for the conveyor and this was not in a

very convenient position. Quite obviously nip guards should have been fitted tothe dangerous in running nip between the head pulley and the belt.

Conveyor belt Fire in a steel plant

A major fire broke out recently in the coal conveyor system of the thermal power project pf a steel plant. The conveyor belt at the bunker level caught fire and was

damaged beyond repair. No one was injured. Though investigation is yet to becompleted and the actual events that led to the incident are to be determined, the

damage was believed to be substantial owing to high cost of the belt, about 100

meters of which were destroyed in the fire. In another fire incident in the coal

landing conveyor belt that occurred an year back in the same plant, nearly 900meters of the conveyor belt the electrical motors were burnt, resulting in a loss

that was estimated to run into crosses of rupees.

The fire safety of the conveyor systems in the plant need to be assessed for findingthe deficiencies and the feasible remedial measures.

Overheated Clinker Shuts Down cement plant

Clinker at a cement mill was transferred from two kilns to storage by acomplicated system of belt conveyors in un spkrinklered corrugated asbestos and

corrugated iron enclosures. Clinker leaving the kilns at about 2100oF was cooled



to 150oF – 200oF. Thermocouples in the cooler recorded clinker temperatures and

adjustments were made to the operation of the kiln to maintain proper temperatures. A fixed water-spray system at the cooler was available. Hot clinker

ignited one of the rubber conveyor belts, and the flames spread to five other belts.

Six conveyor belts were consumed. Conveyor machinery, enclosure, scales, anelevated bridge, and electrical equipment were heavily damaged. Full production

was not resumed until 2 ½ week later.

Improper Design of Conveyor Capacity contributed to Fatality

In a paper mill, a worker engaged in removing the spillage of burgesses along a belt conveyor section met with a fatal accident. His job was to remove the spilled

material by a shovel and to put it back on the running conveyor. During the progress of such work the shovel got entangled between the idler and the conveyor

belt, and he tipped forward onto the belt. This occurred at the tail end section of

the belt that feeds onto a discharge chute leading to lower elevation. The worker was carried by the belt section and thrown into the chute through which he rolledwon. In the process, his head struck against some fixed part and died.

Investigations revealed scope for guarding at the tail end section of the belt andalso for redesigning the belt width so as to minimize the chances of spillage of the

material.

CHAPTER-9

DESIGNING ‘ELECTRICALS’ FOR SAFETY IN CONVEYORS

Designing „Electricals‟ in Conveyor technology is always showing up new

problems in connection with safety. Techniques are changing almost every day,

new techniques replacing the old ones. Yet it is almost surprising to find that the

principles involved are just the same, although, the processes or products are quite

different.

Protective Devices

The following are a few electrical devices, to be provided in the belt conveyor

systems:



1. Selection of mode of operation by the selector switch as a programmer

setter.

2. De-interlock switch.

3. Starting the conveyor by sequence switches.

4. Simultaneous stopping of the conveyors.

5. Rope operated emergency switches to stop the conveyor from any place.

6. Limit switches to prevent excessive sway of the belt.

7. Indication lamp to indicate the running of the conveyor.

8. Indication lamp flashing to locate the conveyor that was stopped by

emergency.

9. Siren to hoot in advance to the starting of the conveyor system.

10. Annunciation panel to indicate the fault that caused stoppage.

11. Over speed relays, wherever necessary.

12. Electronic weighing arrangement.

13. Metal detectors.

14. Magnetic separators.

15. Electronic timers.

16. Single Phase prevention relays

17. Magnetic pick-up.

18. Instruments like voltmeter ammeter, etc.,

19. Kilo-watt hour mater.

20. Programmer logic control.

21. Public address system

22. Wireless transmitting and receiving sets

23. Intercom

24. Good lighting



The Electrical/Electronic Controllers in control apparatus may be classified as

Automatic or Non-automatic according to the application and construction.

Automatic Equipments of Devices

These devices consist of the following:

1. Air break contactors employed for switching on and off of electricmotors as well as other power equipments.

2. Devices like relays that respond to changing of electrical values in acircuit and acting upon the second or control circuits of other apparatus

to obtain automatic performance.

3. Devices like limit switches by means of which the operator can actuate

the control circuit or other devices like contactors, relays, etc. in order to

start and stop the control operations or to change a control programmer.Usually these devices are mechanically handled with the operatingmachine and act upon control circuits in a sequence depending upon the

position, the machines go through in their operations.4. Devices like regulators that serve for maintaining or changing the

operating valves of control electrical installations. Again apparatus may be low-voltage or high-voltage depending upon the working voltage of

the circuit in which it is employed.

Non-automatic Apparatus or Devices

These will consist of the following:

1. Knife switches, change over switches, rotary switches, etc., with performmanual on/off switching and change over operations in low voltage power

circuits.2. Low-voltage fuses specially designed of the protection of power circuit and

electrical installations from large short circuit and overload currents.

3. The resistors, rheostats and controllers designed to control currents andvoltage in electrical machines and circuits.

Common protective Arrangements

The following protections are commonly employed for an electrical drive.



1. HRC fuses for short circuit protection.

2. Relays for overload protection

Fuses

H.R.C. Fuses are normally provided for short circuit protection. When the motor is of smaller size it is usual to employ re-wearable type fuses. This will have theadvantage of renewing the fuse wire whenever it melts. But there is a tendency for

these fuses to get aged and consequently deteriorate unevenly when subjected torepeat over currents that invariably occur during the starting of A.C Induction

Motors. This may result in single phasing conditions. In case one of the threefuses blows the motor will still be working drawing higher current in the two

sound lines.

Cartridge Type Fuses

These are popular known as H.R.C.Fuses, i.e. high rupturing capacity fuses. As in

the previous case the fuse elements will not suffer from any material ldeterioration. The characteristics of these fuses are as below:

H.R.C Fuse link consists of a metallic fuse element surrounded by an arc-

extinguing fixture in the from of a granular non-conducting material. The elementand filler are totally enclosed in a strong and robust insulating container which has

flame proof and heat resistant properties.

Application

The H.R.C Fuses are usually employed in series with the ACB‟s of capacities

inadequate to deal with an increased short circuit kilo volt amperes. This will prevent any damage to the ACB‟s the replacement of which will be costly and time

consuming. The H.R.C.Fuses also protect the3 motors from any abnormal shortcircuit conditions.

Irrespective of the supply system (whether neutral is earthed or not) it is necessaryto fix one fuse in each of the three supply lines.

Overload protection

The employment of the following devices is found common in practice.



Solenoid Overload Relay

This is usually dash pot type. The mode of operation is that each supply line

current energies a solenoid causing on iron plunger to lift. This lifting again

pushes a common bar to trip the ACB by cutting off supply to its coil, whenever a

sustained over current flows. In order to prevent plunger action and tripping due toany momentary over currents like those while starting an induction motor adamping arrangement is provided by filling each dash pot with oil. There is also a

setting to adjust the time delay.

Thermal Overload Relay

Commonly the actuating element in such a relay is a Bi-metal strip. The thermo

static element is made by welding together , throughout their entire length, strips of

two metals having widely different coefficients of expansion. When a straight strip

of this bi-metal is fast ended to a fixed base at one end and it is subjected to achange in temperature, the differential expansion causes the free and to move andactuate a relay. It can be used to operate either to open or close a normally- closed

to normally open contact. In some makes the motor current flows direct to theelement and in others through a heater coil located close to the bi-metal strip.

Load setting adjustments ate provided with a compensating device to allow for variations in the expansion of the metals due to ambient temperature. The time

taken for the bi-metal strip to expand sufficiently to operate the trippingmechanism gives the necessary retarding action.

Positive Back-up protection

In spite of the conventional overload protection as discussed above there is every possibility for a failure of an electric motor due to sustained overload in its

windings not sensed by the above protections. The type of fault is usually in theform of earth fault or short circuit. So, it is better to provide a positive back-up

protection to sense and indicate any abnormal over-current dentition first and if notattended to in time trip the power supply to the motor. The latest trend is to imbed

devices called thermostats at a few critical locations. The thermostat will sense a pre-set temperature and give indication before the temperature develops to a level

that would be dangerous to the insulation.

Thermostats are semi-conductors of ceramic material made by sintering mixturesof metallic oxides such as cobalt, manganese, nickel, copper and uranium. These

are available in forms of beads, discs, washers and rods.



Each stator phase winding will be embedded with two sets of such sensors. Each

set with three thermostats one on each phase will be connected in series. One setwill be used to give an alarm indicating an excess temperature of 120oC in the

windings. In the case of motors that have Class B insulation, the permissible

maximum temperature rise „to the windings is 130 oC, the temperature goes beyond this limit it will be injurious to the windings of the motor. Hence, quick

and suitable action will have to be taken to prevent the cause continuing. Beforetaking any remedial action if the temperature in the winding shoots-up over 130oc,

the second set will

trip the motor from its power supply, thereby ensuring an efficient positive back-up protection. The two sets of the thermostats for two different response temperatures

will have different color Cades and hence will help in connecting them in series.

Combined Thermal Overload and Single phase preventer

The relay embodies three bi-metal strips carrying the line currents and an auxiliaryswitch for connection in the tripping circuit of the main control equipment. The

thermal strips project between the hinged insulated brats which are normally heldtogether by a spring. The heating of the thermal strips by the passage of current

causes them to bend upwards, so raising the thermal strips by the passage of current causes them to bend upwards, so raising the upper bar. The lower one

follows, as it is held to the upper one by a spring. After a predeterminedmovement of the bimetal strips, a projection from the lower bar strikes a step,

which prevents it following the upper bar any further. The step which limits themovement of the lower bar does not carry any current, but is made of bi-metallic

strip with the same characteristic as the strips which do, so that changes of temperature other than those die to the passage of current affect both in the same

way. This makes the relay independent of ambient temperature. A continued upward movement of the thermal strips will raise the upper bar unit as separated from

the new stationary lower bar sufficiently for the mechanical trip to be released andso opening the circuit of a no-volt coil situated on the main control equipment.

Sing-phase prevent or

If one supply line is open-circuited, its thermal strip will cool and down, while theother two will continue to bend up. This will separate the bars and trip the auxiliary

which, thus opening the circuit of a release coil situated elsewhere.

In general, thermal overload devices are especially suitable for the smaller h.p.motor. It is preferable that they be protected by distribution fuses to open the

circuit, in the event of short-circuit conditions, i.e. the current reaching 5 to 6 times



the full load current of the motor, to avoid any permanent change in the

characteristic of the bimetal by prolonged heavy current.

No-volt Release

The purpose of fitting no-volt release devices is to automatically disconnect themotor from the supply in the event of a general failure of power supply, and toensure that the commented apparatus cannot be re-started or be damaged when the

supply is resumed. No-volt releases are usually of the magnetic type, with an iron plunger excited by a coil connected across two of the supply lines. When the coil

is energized the plunger is drawn upwards to engage some mechanisms or electrical contracts, so making the starting gear operative. The coil continues to

hold when the voltage is about 20% less than normal at ordinary workingfrequency, but releases if the voltage falls about 50% less than normal.

Contactor as No-Load Release

The energizing coil of a contactor is often employed as a component part of astarter or circuit breaker. As this coil is excited across two of the three supply

lines, and controlled by START and STOP push-buttons, or other equivalent, thecoil ceases to hold on and disconnects the motor from the supply when the voltage

fails. Upon the resumption of supply, the connected motor should not be able to

function until the RE-SET button or device, been operated.

Description of Electrical Devices in Brief

A selection switch provided at the drive of a conveyor or at control desk in acontrol room would enable it to be starte3d manually or in sequence, and stopped.

In position‟s‟ of the switch, the conveyor could be started manually be present 3 of

the switch, the conveyor could be started only when the succeeding conveyor in

the direction of flow is started and reaches 80-90% of the rated speed. By turningthe switch to 2” position the conveyor could be sto pped. So long as this switch is

in this position, it will not be possible to start it under any condition.

DE-Interlock switch

To facilitate test running the conveyor independently, provision is made byemploying a key-switch which should be normally available with supervisory

personnel and should be operated only under his authority. During production, theconveyor should not be run in the de_interloked condition.



Sequence Switch

The starting of the conveyor in sequence is made possible by the employment of a

sequence switch. This switch prevents the possibility of choking of the rail end of

the conveyor. Father this switch will stop the conveyor from the point of feeding

along with the loading excavator.

Simultaneously, stopping of all the preceding conveyors including the leading the

loading excavator will be made possible by suitable provision in the system. Thiswill prevent any possible over dumping of a tail end of a conveyor .i.e. the transfer

point.

Pull Cord Switch for Emergency Stopping

During an emergency, it would be possible to stop the conveyor from any place by pulling a rope stretched along both the sides of the conveyor, by using a pull cord

tripping switch. One end of the rope will be anchored to a lever operated switch atthe end or at any convenient location. Once the conveyor is stopped by operating

the switch, the attendant will have to look into the cause and reset the switch, start

the conveyor again. Without manually resetting, it will not be possible to start theconveyor. The person who actuated the emergency switch should announce the

cause. The conveyor should not be allowed to work without these switches incircuit under any circumstances.

Contactor as No-Load Release

The energizing coil of a contactor is often employed as a component part of a

starter or circuit breaker. As this coil is excited across two of the three supplylines, and controlled by START and STOP push-buttons, or other equivalent, thecoil ceases to hold on and disconnects the motor from the supply when the voltage

fails. Upon the resumption of supply, the connected motor should not be able tofunction until the RE-SET button or device, been operated.

Description of Electrical Devices in Brief

A selection switch provided at the drive of a conveyor or at control desk in a

control room would enable it to be starte3d manually or in sequence, and stopped.In position‟s‟ of the switch, the conveyor could be started manually be present 3 of

the switch, the conveyor could be started only when the succeeding conveyor inthe direction of flow is started and reaches 80-90% of the rated speed. By turning



the switch to 2” position the conveyor could be stopped. So long as this switch is

in this position, it will not be possible to start it under any condition.

DE-Interlock switch

To facilitate test running the conveyor independently, provision is made byemploying a key-switch which should be normally available with supervisory personnel and should be operated only under his authority. During production, the

conveyor should not be run in the de_interloked condition.

Sequence Switch

The starting of the conveyor in sequence is made possible by the employment of asequence switch. This switch prevents the possibility of choking of the rail end of

the conveyor. Father this switch will stop the conveyor from the point of feedingalong with the loading excavator.

Simultaneously, stopping of all the preceding conveyors including the leading theloading excavator will be made possible by suitable provision in the system. This

will prevent any possible over dumping of a tail end of a conveyor .i.e. the transfer point.

Pull Cord Switch for Emergency Stopping

During an emergency, it would be possible to stop the conveyor from any place by

pulling a rope stretched along both the sides of the conveyor, by using a pull cord

tripping switch. One end of the rope will be anchored to a lever operated switch atthe end or at any convenient location. Once the conveyor is stopped by operating

the switch, the attendant will have to look into the cause and reset the switch, start

the conveyor again. Without manually resetting, it will not be possible to start theconveyor. The person who actuated the emergency switch should announce thecause. The conveyor should not be allowed to work without these switches in

circuit under any circumstances.

Limit SwitchesThe conveyor belt can move to the right or left. In order to limit its travel, twolevel operated switches will be fixed on either side of the belt. They may be made

to give an alarm or stop the conveyor in case of excessive swing.

Red Indication Lamp



A red indication lamp will be fixed at a topmost point of the drive head of a

conveyor so as to be conspicuous and visible from a distance. This will glow onlywhen the conveyor runs. Obviously, when it is not glowing it indicates that the4

conveyor is idle.

Yellow indicating Lamp

One yellow indicating lamp also will be fixed at the top most point of the drive

head of a conveyor. When the lamp flashes continuously, it indicates that theconveyor is stopped by emergency.

Siren

A siren should be fixed to give an audible warning in advance to the starting of a

conveyor system by manual sequential operation. This would help the working personnel to clear away from the conveyor or its close vicinity.

Annunciation Panel

An illuminated annunciation panel should be fixed in the kiosk of each drive head.This would indicate the fault due to which the conveyor could not be started or

stopped.

Over speed Relays

It is essential to continuously monitor the running of the motor or conveyor atmore than its rated speed and most important in case of down-hill conveyor. The

belt speed is usually detected by a Photo-Electric pulse transmitter driven by a

drum on the drive head or tail end section of the belt. Usually it may be in theform of a sensing wheel with projections mounted on the shaft of the motor with

proximity pick up magnetic read switch or a photo-electric cell with a train of pulses.

This signal is given to an electronic circuit that will sense the duration between the

pulses. If the interval between pulses is more than set time and if it continues for more than the time delay set, a relay will be de-energized or energized according to

the design of the circuit. This can be automatically or manually re-set. In case of manual re-set, acknowledgement push-button could be made available.

Electronic Weighing Arrangement



For an efficient operation, the rate of flow of material on the conveyor has to be

monitored continuously for taking necessary corrective measures for the optimumoutput. An electronic weigh bridge is to ideal to be fixed. These weigh bridges are

easily available in the market.

Metal Detectors

Sensing and detecting the iron a piece flowing along with the materials in the

conveyor is necessary to save the belt as well as the crushers which will be fed byto the choice, so that these materials can be picked-up in a running conveyor, if it

is a low speed conveyor. In case the speed of the conveyor is high the device may be made to trip the conveyor.

Magnetic Separators

A magnetic separator sense the presence of iron pieces in the material flow, attracts

them and throws them out on the side of the conveyor by a small conveyor runningcrosswise. This magnetic separator laid across the running conveyor possesses a

powerful magnet which attracts the iron pieces carry sideward by which time it

passes the non-magnetic sing zone and thrown out side wards.

Electro Mechanical Relays and Static Relays

At present it is common to employ electro mechanical relays for basic protectivefunctions. Their operation is simple and visible. These are sensitive enough to

handle the normal fault condition. They can be easily handled by electricians.

But some moving parts are involved in time. As is well known, any moving partis a trouble giving part is a welcome feature. A solid state relay has no vitalmoving part. It can stand higher shock and vibration. It occupies comparatively

lesser space. The input burdens usually low. Hence, the size is smaller. It can beoperated with instrument transformers. Since no moving part exists, there is

practically no maintenance involved. When these are to be employed in anopencast mine laden with fine dust, some extra protection will become necessary to

prevent ingress of fine dust.

Wilding Protection

In a normal operation of conveyors, there is every possibility of a contactor of a

drive getting welded especially while breaking a high current when the conveyor isswitched off by the push button on the control circuit. The consequence of such

occurrences however rare it maybe, will prove to be, will prove to be disastroussince the motor/s will continue to run. All the related protections through the

control circuit will become defunct. The consequences of such a situation may



prove to be beyond repairs. As such it becomes imperative to avoid such an

occurrence, by redesigning the control circuit. Positive protection to the motor could be given by disconnecting the source of supply to the incoming the

contactor.

CHAPTER -10

SYNOPSIS

MAINTENANCE OF CONVEYOR SYSTEMS

Management talks about maintenance to ensure safety of the equipments.

Employees talk about their own safety. However, these two aspects are the two

sides of the same coin. Good maintenance of equipment automatically ensures

safety of people. In respect of belt conveyor systems, the types of accidents that

are likely to occur due to lack of proper maintenance and maintenance facilities

have been explained with real life experiences. The types of maintenance,

maintenance facilities and equipments required to ensure safety of equipment,

properties and people have been suggested.

CHAPTER-11

TYPES OF BELT CONVEYORS &SAFETY MEASURES



1.PORTABLE BELT CONVEYORS

2.GRAVITY BELT CONVEYORS

3.ROLLER OR WHEEL BELT CONVEYORS

4.LIVE ROLL BELT CONVEYORS

5.VERTICAL BELT CONVEYORS

PORTABLE BELT CONVEYORS: Belt, flight,apron,extendible,and fixed bucket

conveyors are made also as inclined portable units on a pair of large wheels, for

loading rail road cars and trucks with bulk materials and for raising construction

material from one elevation to another.

The various types of portable conveyors should be provided with guards as

specified for the corresponding types of fixed conveyors.

Weather proof electrical equipment should be used.With three-phase power, the

flexible cord that is connected to the power outlet should be a four-conductor, the

fourth wire being grounded in all plugs and receptacles.The cable should be so

arranged that it can not be run over by trucks or other machines. If the cable must

cross a driveway, it should be hung on poles at a minimum height of 14ft(4.3 m).If

two or more sections of cable are required, the connectors should be kept above the

ground, since these machines are used most in the worst weather.



Portable Belt Conveyors should have skirt boards or side boards (not less than 10

in(25 cm) high to keep heavy material from falling over the sides and light or loose

material from blowing off.This safety feature applies to belt conveyors, as well as

to the other types, because troughing of the belt gives insufficient protection

against such spillage.The conveyor should be stable and should be fitted with a

locking device to hold the conveying unit at various fixed elevations.

The mechanism for raising and lowering the boom on all types of portable

conveyors should be closely checked periodically- It constitutes one of the greatest

sources of hazard in the use of such machinery. Any positive type may be used, but

the self-walking worm or jack-screw type preferable.Gear drives should be

completely housed and run in oil.All chains within easy reach of workers should be

thoroughly guarded,and a system should be provided for convenient oiling for

chains.In warehouses,the boom of portable conveyors usually consists of two

sections to permit their use in a small space.These conveyors should be so

designed that material will not roll back from one section to the other at the

transfer point.

When Portable Conveyors are used for loading or unloading railroad cars, a

suitable safety device should be provided to prevent the car from shifting during

the operation.The device should not be removed until the crew is sure that no one



is in the car.A red banner or a standard blue warning sign at each end of the car is

recommended as a warning to switching crew.When Portable conveyors are used

in raising or lowering construction materials, ample stairs or ladders should be

provided in the immediate vicinity of the conveyor.Walking on idle or moving

conveyors should be prohibited.

GRAVITY CONVEYORS: The fact that Gravity Conveyors depend wholly upon

the natural force of gravity for their operation often leads to disregard of some

necessary safe practices. Even though it is not power-driven, this equipment can be

the source of serious accidents.

There is real danger if an employee climbs upon a conveyor to release

a blockade. He may either slip on the rollers or be knocked down should the jam

suddenly be released. To guard against this hazard,workers should be prohibitedfrom climbing onto conveyors.In

addition, steel or wood plates should be installed between rolls, so that neither a

worker,s body nor limb can fit between the rolls.Gravity conveyors are divided

into two general classes-Chute conveyors and roller or wheel conveyors

Chute conveyors chutes of polished metal sheets or bars are used to lower packing

cases,cartons and crates from one floor to another and from the side walk to the

basement of amercantile building through a side walk elevatorshaft or other

opening.Some gravity chute conveyors are built in the form of a spiral around a



vertical pipe with a slope at the outer edge between 18 and 30 degrees.In removing

packages from the delivery end of spiral chutes, workers frequently injure their

hands,which become caught by decending packages or are mashed against others

on the delivery table.Where the chute is enclosed, a warning sign should be placed

over the delivery end. A Simple mechanical or electrical device that will give

warning when a package is about to be delivered from the chute is

advisable,especially where the packages cannot be plainly seen descent.Spiral

chutes present a serious fire hazard because they form flues from lower floors to

upper floors through which fire will spread quickly. Two methods of eliminating

this hazard are in general use: one is to enclose the chute in a tower made of fire

resistant material, such as steel, concrete, or masonry;the other is to provide

automatic fire doors (draft checks) where the chute passes through floors.The

enclosed tower has doors at each charging station and a door at the delivery end.

The charging station doors should be kept closed,except when charging is being

done. The door at the delivery end should close automatically in case of fire.Where

an open chute is used, a guard rail and toe board should be provided at each floor.

The charging stations should be guarded either by a movable railing or by a hinged

door or gate.

ROLLER OR WHEEL CONVEYORS: Gravity Roller or wheel conveyors are

similar to chute conveyors,except that the angle of slope is much less (2 to 4



percent). The conveyors can be used to convey packages for considerable distances

on one floor.If the rollers or wheels are placed radially instead of parallel,the

course of travel can be changed from a straight line to a curve.

The principal hazards in the use of roller conveyors are that material may

run off the edge of the rollway and fall to the floor,and that loads may run away. A

guard railing often is provided on each side of the roller conveyor way,to guide the

material and prevent it from running off. Such guard rails are especially advisable

at corners and turns and on elevated conveyors under which men must work or

pass.Where heavy loads are conveyed, retarders,brakes, or similar means should be

provided to prevent the loads from running away,or a power conveyor on which

speed can be controlled should be substituted.A vertically swinging hinged section

of a roller or wheel conveyor should be hinged to that end of a stationary section of

the conveyor from which the material is flowing to help block the oncoming

material.The open end of the conveyor line should have a stop that automatically

projects above the level of the rollers or wheels when the hinged section is opened

and automatically retracts when the hinged section is closed.Where a horizontally

swinging hinged section occurs in a conveyor,the open ends of stationary

sections(the two ends adjacent to the hinged section) should be equipped with

retractable stops to prevent loads from droping off when the hinged section is

open.



LIVE ROLL BELT CONVEYORS: A Live roll (or roller) conveyor consists of a

series of rolls over which objects are moved by power applied to all or some of the

rolls through belts or chains.Where installed at floor level or used in working

areas,live roll conveyors should be designed to eliminate hazards from pinch points

and moving parts, unless other provisions are made to prevent personnel from

coming in contact with or crossing the conveyor.

VERTICAL BELT CONVEYORS: Vertical Belt Conveyors handle packages or

other objects in a vertical or substantially vertical direction.In some cases, a hinged

section,interlocked to the power in the main system,will be provided for acess to

the work station. The interlock should shut down the entire system until the section

is restored to its position.There are three basic types.1.Vertical Reciprocating

Conveyor 2.Suspended Tray Conveyor 3.Vertical Chain Conveyor

Vertical Reciprocating Conveyor a power or gravity actuated unit that receives

objects on a carrier or car bed,usually constructed of a power or roller conveyor,

and elevates or lowers them to other locations.

Suspended Tray Conveyor a vertical conveyor having one or more endless chains

with pendant trays,cars, or carriers that receive objects at one or more elevations



and deliver them to another or several elevations.Protection of the underside is

critical to prevent materials from falling on people.

Vertical Chain Conveyor (opposed shelf type): two or more vertical elevatingconveying units opposed to each other, each unit consisting of one or more endlesschains whose adjacent

facing runs operate in parallel paths.Thus, each pair of opposing shelves or

brackets receives objects (usually dish trays) and delivers them to any number of

elevations.Where vertical conveyors are loaded and unloaded automatically

,guards should be provided to protect personnel from contact with moving

parts.Where they are loaded and unloaded manually, guards and safety devices,

such as lintel and sill switches and deflectors,should be installed.Carriages of

vertical reciprocating conveyors designed to register at a floor, balcony,gallery, or

mezzanine level never should have a solid bed.This type of conveyor is not

intended to carry passengers or operators or to have its car or carriage called to a

station by a manually operated push button.



CHAPTER- 13

BELT CONVEYORS TROUBLESHOOTING – CAUSES & CURES

belt conveyor project 03-07-2013

Documents