Conveyors

Rousseau Jooste
Boschfontein Shaft

12 August 2009
 Overview

„ Objectives

„ Application of Conveyors in Underground Hard Rock

Mines
„ Belt Conveyor System
„ Legal Requirements
„ Safety Devices
„ Maintenance
„ Conveyor Belt Innovation
„ Incidents
„ Conclusion
 Overview

„ Objectives

„ Application of Conveyors in Underground Hard Rock

Mines
„ Belt Conveyor System
„ Legal Requirements
„ Safety Devices
„ Maintenance
„ Conveyor Belt Innovation
„ Incidents
„ Conclusion
 Objectives

„ Introduce the use of conveyor belts in the bulk handling of ore in

underground, hard rock mines

„ Discuss the legal requirements regarding conveyor belt

installations

„ Highlight the applicable standards and procedures

„ Share best practice with regards to installation, maintenance and

safe operation of conveyor belt installations

„ Raise awareness with regards to the hazards and risks

associated with conveyor belt installations

„ Receive feedback and affirmation that I have achieved the required

competence level
 Overview

„ Objectives

„ Application of Conveyors in Underground Hard Rock

Mines
„ Belt Conveyor System
„ Legal Requirements
„ Safety Devices
„ Maintenance
„ Conveyor Belt Innovation
„ Incidents
„ Conclusion
Application of Conveyor Belts in Underground Hard Rock Mining

„ Belt conveyors are commonly used for lateral and inclined ore transfer

„ Energy efficient (near 95%) and have a payload-to-dead load ratio of 4:1

„ Belt conveyors require high initial investment and do not allow for flexibility

„ Economical conveyor belt transfer requires relatively high production rates

and significant transport distances

„ Availability if well maintained could be up to 90%

„ The reliability and operating cost of the system are largely dependent on
material sizing of the broken rock and elimination of tramp material

„ Easy to automate
 Overview

„ Objectives

„ Application of Conveyors in Underground Hard Rock

Mines
„ Belt Conveyor System
„ Legal Requirements
„ Safety Devices
„ Maintenance
„ Conveyor Belt Innovation
„ Incidents
„ Conclusion
 Belt Conveyor System
The main components of the belt conveyor system are the conveyor belt, belt support system,
pulleys, drive train, enclosure for loading and ancillary equipment

Simplified illustration of a conveyor belt installation Comments

„ Boschfontein 4 belt legs
„ Inclined a 15°
„ 3 interlocked
„ Capacity of 500tph
„ Installed 1.1MW
„ Speed of 2.2 m/s
„ Length
„ CV1 belt is 567.57m
„ CV2 belt is 511.55m
„ CV3 belt is 527.14m
„ CV4 belt is 597.13m

Anglo Platinum 7
 Belt Conveyor System
A conveyor belt comprises of two parts, the reinforcement or carcass and an elastomeric
covering

Illustration of conveyor belt types Comments

„ Multiply belt carcass

„ Multiple plies of woven belt fabric
„ High adhesion inter plies
„ Hard ores
„ <1000m, <125kN/m

„ Solid Woven
„ Solid woven carcass with PVC impregnation
„ Rip and impact resistant
„ Coal
„ <160kN/m
„ Steel cord
„ Steel cords embedded in rubber compound
„ Higher tensile strength
„ Excessive loads
„ Virtually stretch less - steep inclines
Anglo Platinum 8
 Belt Conveyor System
None of the conveyor belt components are as important as the belt and all measures should be
taken to safeguard the integrity of the belt

Illustration of correct conveyor belt storage Comments

„ Select construction that suits application

„ Carcass with adequate tensile strength to move load
and absorb impact energy
„ Cover thickness that will sustain abrasion, impact and
wear
„ Bulk density 2.5t/m3
„ Belt width 3-5 times maximum lump size (-300mm)
„ SOW 10:1
„ Belt 900mm 2000/4 ply (8x3) N - SANS 1173-1977
„ Storage
„ Upright position
„ Out of direct sunlight
„ 10-25° C
„ ¼ turn every 3 months to relieve pressure
concentration points
„ Away from oil and water

Anglo Platinum 9
 Belt Conveyor System
The two ends of a multiply conveyor belt can be connected using the mechanical joint,
cold or hot splice method in accordance with the written procedure called for in Sect.
8.9(10) of the MHSA 29 of 1996
Insertion of a mechanical joint Hot splicing taking place

„ Flexco riveted mechanical joint „ REMO contractor

„ In house „ 100% strength
„ Water ingress and flexing weakens „ Flexible
belt
„ Sealed
„ Minimum production interruption
„ New to new; old to old
„ 8hrs
Anglo Platinum 10
 Belt Conveyor System
For a conveyor to provide total control of dust and spillage the engineer should do everything
possible to keep the belt’s travel line consistently steady and straight

Illustrations of a idlers Comments

„ Idler brackets carried on stringers

„ 3 roll troughing idlers (900mm)
„ Angle (20-45°) allowing empty belt troughing
„ Steel, PVC, sealed bearing
„ Anti roll back
„ Flat return idlers (3m)
„ Lagging for tracking

„ Training idlers
„ Keeps belt trained
„ Disadvantage is ply separation due to sidewall tears
„ Weightometer
„ Hinging frame with idler bracket and load cell
„ mV signal output converted to tph

Anglo Platinum 11
 Belt Conveyor System
The belt conveyors at Boschfontein Shaft are powered with two drive trains located near the head
pulley

Illustration of one drive assembly Comments

„ 3 ph 525V 160kW Induction motors

„ High speed fluid coupling
„ Thruster brake
„ David Brown Reducion gearbox 40.927:1
„ Low speed fluid coupling
„ Drive pulley shaft

Anglo Platinum 12
 Belt Conveyor System
The shaft power from the drive train is transferred in to linear movement of the conveyor belt
through an arrangement of drive and snub pulleys

Illustrations of lagged pulleys and mounting Comments

„ Drive pulleys
„ Diamond lagging
„ Rubber µ = 0.42
„ Increased life
„ Ceramic
„ Snub Pulley
„ Determine angle of wrap
„ Shaft and Plumber block
„ Solid shaft / stub shaft
„ Bearing seated in plumber blocks
„ Self lubricating
„ Mounted so that pull force exerted on steel structure

Anglo Platinum 13
 Belt Conveyor System
It is necessary to remove the fugitive material, carryback and spillage, which has
accumulated on the surface of the belt using scrapers

Illustration of two types of scrapers Comments

„ Prevent damage when trapped between belt and

pulley
„ Restores coefficient of friction

„ Carry side scraper

„ Sprung blade scrapers
„ Clean surface from carryback after discharge

„ Inside belt
„ Plough scraper configuration
„ Remove spillage accumulation on return belt

Anglo Platinum 14
 Belt Conveyor System
In order to effectively drive the conveyor, it is required that the conveyor belt is
appropriately tensioned

Tensioning car with gravity take up Comments

„ Equal tension across the width of the belt

„ Automatically take up any slack or stretch

„ Horizontal tension car

„ Screw type
„ Tower weight

„ Gravity take up
„ Take up pulley under return belt
„ Upper and lower limit switches
„ Lower to ground or sprag with RSJ beams

Anglo Platinum 15
 Belt Conveyor System
The loading point is designed to maintain and control the broken rock when being
transferred from a static source to a moving belt

Illustration of a loading point Comments

„ 75-90% of belt wear occurs at the loading points

„ Operation - procedure RPMRS-EPR-ENG-STD-094

„ Feeder
„ Shear material from static consolidation, accelerate
„ Vibrator – economical, reliable, cheap & easy to
maintain
„ Apron – abrasive, lumpy /sticky ores
„ Match belt capacity

„ Loading Chute
„ Langlaagte chute

„ Radial door

Anglo Platinum 16
 Belt Conveyor System
For an effective minimum spillage transfer point is essential that the belt line be
stabilised and well supported

Illustration of impact reduction devices Comments

„ Impact reduction
„ Impact idlers
„ Impact cassettes

Illustration of skirt boards

„ Skirt boards
„ Gap tapered from rear to front
„ The length of skirt boards should be at least 3 times
the belt width

Anglo Platinum 17
 Belt Conveyor System
The challenge of the transfer point is to tip all the broken rock form one belt leg onto another in a
manner that prolongs the belt life, prevents spillage and keeps the belt trained

Illustration of a transfer point Comments

„ The most expensive material is the material spilled

from the belt
„ Feed in- line or from strike conveyors
„ Impact curtain
„ Finger grizzly
„ Fines create bed for coarser rock
„ Maintain flight velocity at belt speed

„ Discharge point
„ Impact curtain
„ Chute linings

Anglo Platinum 18
 Belt Conveyor System
The belt conveyor structure can be installed in the footwall or hanging wall

Illustration of a hanging wall conveyor Comments

„ PRO
„ Easy to install and extend
„ Less costly
„ CON
„ Maintenance arduous
„ Inspections timely

Illustration of a footwall conveyor

„ PRO
„ Accessible for maintenance
„ Easy to inspect belt
„ Easy to lash

„ CON
„ Higher capital investment
„ More intricate installation

Anglo Platinum 19
 Overview

„ Objectives

„ Application of Conveyors in Underground Hard Rock

Mines
„ Belt Conveyor System
„ Legal Requirements
„ Safety Devices
„ Maintenance
„ Conveyor Belt Innovation
„ Incidents
„ Conclusion
 Legal Requirements

MHSA,sect 8.8(2) employer to take reasonable practicable measures to prevent persons being
injured because of any machinery failling as a result of…(c) poor maintenance

MHSA,sect 8.8(3) The measures taken by the employer must ensure

a) Only persons authorized by the employer to do d) Machinery is only operated if all installed safety
so, start, operate and maintain any devices are operational and functional
machine…which may pose a significant risk to any
person

MR 20.1.1 The operation of or attendance on machinery shall be in charge of a competent

shiftsman …

Anglo Platinum 21
 Legal Requirements

MHSA,sect 8.9(1) In compliance with 8.8(1) the employer must ensure that

a) A conveyor belt installation is not cleaned when b) The power supply of a stationery conveyor belt
any of its parts are in motion installation is locked out during repairs,
maintenance, routine cleaning and cleaning of
spillage

h) … sequence interlocking is provided which will automatically stop all conveyors feeding a belt conveyor
which has stopped and prevent a conveyor from starting until the conveyor on to which it feeds has
started

i) Only persons authorized to do so by the employer operate, maintain, clean and repair a conveyor belt
installation

MHSA,sect 8.9(9) The employer must take reasonable measures to ensure that the
functionality of…any other safety devices relating to the conveyor belt installation are tested
weekly

Anglo Platinum 22
 Overview

„ Objectives

„ Application of Conveyors in Underground Hard Rock

Mines
„ Belt Conveyor System
„ Legal Requirements
„ Safety Devices
„ Maintenance
„ Conveyor Belt Innovation
„ Incidents
„ Conclusion
 Safety Devices
Many fatal accidents and lost time injuries have taken place because the danger points
of belt installations were unguarded or inadequately guarded

Tail pulley fencing and nip guard Comments

„ MHSA 8.8(1) requires employer to take reasonable

practicable measures to prevent injury from moving parts
of machinery
„ MR 20.5 calls for moving exposed machinery to be fenced
off and efficient guards at source of danger
„ Memorandum on Guarding of Belt Conveyors
„ Body, clothing or tools trapped at nip point
„ Effective guard or fence – upward, over, into, around or
through (min 850mm)

„ Nip guard over width of head, tail and snub pulley

„ Max clearance of 8mm not to vary under tension

„ Also fenced off

Anglo Platinum 24
 Safety Devices
Since 2000, 73 persons were fatally injured and 666 were injured due to conveyor
accidents…
Pull key MHSA 8.9(1)(c) Misalignment MHSA 8.9(5) Slip detector MHSA 8.9(1)(d)

Rip detector MHSA 8.9(5) Arrestor MHSA 8.9(1)(d) Magnet

Anglo Platinum
 Safety Devices
…hence many safety devices are installed on the conveyor to ensure that the
installation is operated safely and effectively
Earthing, lightning
Start up siren and light Decking plates protection MHSA 8.9(6)
MHSA 8.9(1)(f)

Anti Roll back pulleys Fire extinquishers RS-050-

Illumination, walkway MHSA 8.9(3)
0003

Anglo Platinum
 Safety Devices
20 September 2004 a conveyor belt caught alight at Northam Platinum Mine, claiming
the lives of 9 employees due to inhalation of poisonous gasses and fumes.

Fire suppression system Comments

„ MHSA 8.9(4) calls for measures to prevent, detect
and combat fires
„ Deluge fire detection and suppression system
installed
„ Alarms then trips on combination of
„ Bearing temperature
„ CO and smoke sensors
„ Linear detection tube
„ Infrared heat detector
„ 1738 l/min transfer, head, drive, takeup
„ Point of discussion
„ slipping belt, rise in temp of pulley due to friction, if
tripped heat transferred to belt and ignition takes
place, ideally start suppression system but keep belt
running
„ Caution with deluge system
„ Can the dewatering system accommodate the amount
of water discharged per minute?
„ Are available water reserves adequate to sustain
prolonged suppression?
„ Avoid flammable material and cables above
Anglo Platinum conveyor installation 27
 Safety Devices
Conveyor loading and discharge points are prime sources for the creation and release
of airborne dust

Basics of dust control Comments

„ Contribution factors
„ Nature of material
„ Height of drop
„ Speeds
„ Angles of loading and unloading

„ Remedies
„ Reduce air quantity through the load zones
„ Reduce air velocity through load zones
„ Reduce dust creation inside load zones

„ How?
„ Exit area dust curtains
„ Sealing at entry area
„ Filter bag
„ Water
„ Fog
„ Foam

Anglo Platinum 28
 Overview

„ Objectives

„ Application of Conveyors in Underground Hard Rock

Mines
„ Belt Conveyor System
„ Legal Requirements
„ Safety Devices
„ Maintenance
„ Conveyor Belt Innovation
„ Incidents
„ Conclusion
 Maintenance
In order to ensure the continued safe and effective functioning of the conveyor belt installation it
is imperative that maintenance is completed as per the scheduled task lists

Maintenance Comments
„ Daily „ Pre-use checklist
„ Fitter
„ Logbook
„ Appointments
„ Weekly „ Design parameters
„ Fitter „ Equipment
„ Boilermaker „ Belt type
„ Electrician „ Splices, clips
„ Rigger „ Pulley lagging
„ Condition of belt (edge tears, cover)
„ Monthly „ Idlers, impact bed
„ Fitter „ Bearing temperatures
„ Engineer „ Motor and cables
„ Gearbox, coupling
„ Vibrator feeder, chutes
„ Trips
„ Job report
Anglo Platinum 30
 Overview

„ Objectives

„ Application of Conveyors in Underground Hard Rock

Mines
„ Belt Conveyor System
„ Legal Requirements
„ Safety Devices
„ Maintenance
„ Conveyor Belt Innovation
„ Incidents
„ Conclusion
 Conveyor Belt Innovation
Pull keys are required to extend around the head and tail pulleys in such a manner that
the guarding cannot be removed without tripping the conveyor

Retrofit pull-switch and tail end Comments

„ 90° angle prohibits effective activation of the Cuttler-

Hammer pull switch

„ Innovative thinking by Jacques Kause, apprentice

electrician at Boschfontein

„ Retrofit end pull switches with 16A male and female plug
used from winch signalling device

„ Terminal pins connected to complete pull-key circuit

„ Used in conjunction with 6mm wire rope to threaded

around head and tail pulley

„ Male plug easily dislodges when pulled and opens circuit

(file off lid catch)

Anglo Platinum 32
 Conveyor Belt Innovation
Cecil Swanepoel, boilermaker foreman at Mortimer Concentrator invented a device
that isolates a chute radial door, preventing it from closing

Pneumatic cylinder lock out Comments

„ Incident in 1 June 2008 at Richard Shaft

„ MO instructed a shift supervisor to hold open a chute door

for him to inspect where the box hung up

„ Hand slipped off the controls and the door closed on MO

„ Air is applied to cylinder to open radial door

„ Clamping device fits over cylinder rod

„ Lock out facility

„ Cost of R500

„ Joint winner of the CEO Anglo Employee Safety Award

2008

Anglo Platinum 33
 Overview

„ Objectives

„ Application of Conveyors in Underground Hard Rock

Mines
„ Belt Conveyor System
„ Legal Requirements
„ Safety Devices
„ Maintenance
„ Conveyor Belt Innovation
„ Incidents
„ Conclusion
 Incidents
On 27 July 2009 the failure of a mechanical joint on the 3rd leg conveyor belt at
Brakspruit Shaft resulted in a belt runaway, injuring an employee

Conveyor runaway carnage Comments

„ Involved
„ Rebecca Tsamaesi, boilemaker assistant

„ Cause of injury resulting in puncture to the knee

„ Boilermaker and assistant and aide travelling along the belt
conducting routine inspection
„ Belt break occurred
„ Belt runaway
„ Broken rock on belt was spilled onto walkway
„ Rock struck assistant on the left leg
„ MTC progressed to a LTI

„ Root cause
„ Mechanical joint pulled out of belt
„ Mechanical joint should only serve as temporary measure
„ Good practice to replace with cold or hot splice within 1 week
(Boschfontein)

Anglo Platinum 35
 Incidents
On 19 March 2002 an incident took place at Boschfontein Shaft when the chain link on
a 3T chain hoist failed, later resulting in a fatality.

Counterweight and failed chain block Comments

„ Involved
„ Mr Jack Mabilo, stope timberman

„ Cause of injury resulting in fatality

„ Conveyor was isolated in order to perform belt splicing
„ The now deceased assisted in lifting the top conveyor to remove
idlers
„ Was on top of the belt when the link of chain hoist failed
„ Counterweight dropped and belt tensioned
„ Whipping of belt caused deceased to strike his head against the
steel structure of the conveyor
„ Injuries to the head later resulted in death on 31st

„ Root cause
„ Chainblock failure
„ MHSA 8.8.(3)(g) calls for a written lock–out procedure for all
sources of energy
„ MHSA 8.9(1)(g) requires that take up will not move
„ Counterweight was not supported with safety slings
„ Good practice to sprag counter weight with RSJ beams
Anglo Platinum 36
 Overview

„ Objectives

„ Application of Conveyors in Underground Hard Rock

Mines
„ Belt Conveyor System
„ Legal Requirements
„ Safety Devices
„ Maintenance
„ Conveyor Belt Innovation
„ Incidents
„ Conclusion
 Conclusion

„ Belt conveyor installation forms a critical link in the handling of bulk

materials in underground mines

„ The hazards and risks associated with conveyor belt installations

are significant and safety devices require constant attention

„ Imperative for Engineer to have systems, procedures and

appointments in place to effectively manage maintenance of
equipment and structures.

„ Possible to achieve 90% availability