Management of Heat Underground. Case Study of Deeps Section at Mopani Copper Mines Mufulira Mine Site

Health and Safety


Diploma Thesis, 2014

77 Pages


Free online reading

CONTENTS

1. EXECUTIVE SUMMARY

2. DESCRIPTION OF WORKPLACE AND ACTIVITIES
2.1 The workplace
2.2 The Development Process
2.3 Activities

3. IDENTIFICATION OF HAZARDS.
3.1 Hazard 1 – Silica Dust
3.2 Hazard 2 – Noise
3.3 Hazard 3 – Manual Handling
3.4 Hazard 4 - Vibration
3.5 Hazard 5 - Illumination
3.6 Hazard 6 - Heat
3.7 Justification for selection

4. BACKGROUND RESEARCH
4.1 History of Heat stress
4.2 Health effects of working in hot and humid conditions
4.4 Legal Requirements

5. ASSESSMENT OF RISKS
5.1 Methodology
5.2 The Assessment Results/Findings
5.3 Identification of heat stress hazards
5.4 Evaluation of Existing Controls
5.5 Proposed control measures
5.6 Costs for practical and organizational controls
5.6 Benefits from ‘Organizational’ and ‘Practical’ Heat Controls

6. BIBLIOGRAPHY

7. APPENDICES
Appendix 1 - Policy
Appendix 2 – Occupational Hygiene Sampling temperature form
Appendix 3 - Heat Load from Auto Compression
Appendix 4 - Heat Load From Rock Strata.
Appendix 5 - Heat conducted through the rock strata.
Appendix 6 - Conveyor belts and Auxiliary fans
Appendix 7 - Heat Load from Humans
Appendix 8 - Total Mine Heat Load
Appendix 9 - Ventilation prediction
Appendix 9 - Training requirements Relating to Vibration
Appendix 10 - Factors Concerning Silicosis
Appendix 11 - Survey Results for Silica Dust
Appendix 12 - Heat stress Statistics at Deeps
Appendix 13 – Guide maximum handling loads
Appendix 14 - Questions raised during consultation:
Appendix 15 – Refrigeration Plant
Appendix 16 – Definition of concepts and Abbreviation

1. EXECUTIVE SUMMARY

The study was conducted at Mopani Copper Mines Plc, Mufulira mine site deeps section area. The assignment focused on the identification and assessment of the hazards related to the development activities at the deeps section. The particular activities therefore, included; face preparation, drilling, charging and timing, blasting, lashing and hoisting.

The hazards and their current control measures that were thus identified included the following; dust, noise, Manual Handling, illumination, whole body vibration and heat.

Of the listed hazards, heat was selected, assessed and discussed in details. The selection criteria were based on the exposure probability to the risk and its severity. Furthermore, inadequate control measures coupled with limited knowledge of workers formed the justification basis for the selection of heat.

The assessment reviewed adverse thermal conditions as proved by the temperature results from the different levels at deeps, all of which exceeded the occupation exposure limit of 31oC. Further, the capacity of the two air intakes delivered a total of 70m3/sec of air but the actual air which should go to deeps is 200m3/sec 100 from each air intake.

Some control measures, however, were observed to have been put in place by Mopani management which included the installation of fans and the pre assessment of the working conditions by the Persons in Charge (PICs) prior to a day’s work.

Based on the survey findings, recommendations were made to the Mopani management to improve the engineering controls in particular intake and return airways. And to minimize humidity through pumping out of accumulated water. It was further suggested that the management should provide employees with adequate drinking water to replenish the amounts lost through sweating. This could be done by providing large containers strategically positioned where they could be readily accessed. Furthermore, it was suggested to the management to ensure that its workforce is adequately trained and educated on heat stress issues.

It was estimated that in order to fully manage heat at deeps section, it would cost Mopani Copper Mines £32,550,000, a plan which would be implemented over a 1 year period.

2. DESCRIPTION OF WORKPLACE AND ACTIVITIES

Mopani Copper Mines PLC (“Mopani”) is a Zambian registered company owned by a joint venture company comprising Glencore-Xtrata International AG (73.1%) and First Quantum Minerals Ltd (16.9%)) and ZCCM-IH (10%). Minority shareholders are spread throughout the world in various locations. Mopani Mines produces and sells copper and cobalt to the international market being one of the biggest mines and exporters in the world. (Bibliography 17)

The Company has mine sites at Mufulira and Nkana, which are located on the Copperbelt province in Zambia. The Corporate Head Office is established in Kitwe and lies adjacent to the Nkana assets. Nkana has been in operation since 1931 and Mufulira, which has been in operation since 1933 lies 50 kilometres north of Kitwe. (Bibliography 17)

The Company operates the Mufulira mine, smelter, concentrator and copper refinery and the Nkana mine, concentrator and cobalt plant. The name “Mopani” was chosen by vote amongst employees. The Mopani tree is an indigenous Zambian hard wood with a long life and is extremely resilient. (Bibliography 17)

Mopani currently employs approximately 7,600 employees across the 2 sites. Assets; includes a concentrator, a refinery and a smelter; and produces 35,000 tonnes of contained copper in ore each year through the process of open stoping. The deposit lies on the eastern side of the Kafue Anticline. It lies at an elevation of about 1250m above sea level on latitude 12 degrees 32’ south of the equator. The Mufulira license is mined in three geographical areas. Namely Mufulira West Portal, Mufulira East Portal and the main Mufulira mine which comprises of the upper, central and deeps section. (Bibliography 45)

Mopani copper mines Plc. Mufulira mine site has embarked on the project called the “Mufulira Mine Deeps Project” which is intended to cover levels from 1340ml to the proposed deepest level of 2020ml. The deeps project was commenced in the mid part of the year 2004 with the expected production of 2,000,000 tonnes of ore per year from 2015 onwards. This project had an expected duration of between 8 to 10 years. (Bibliography 45)

Due to the wide range of activities and working environments undertaken at Mufulira Mine site, this study will centre on the mining operations at deeps section which is the deepest section of the Mopani Mufulira mine site underground mine. (Bibliography 45)

2.1 The workplace

The Mufulira Underground mine is physically split into 4 sections;

- Upper
- Central
- Lower
- Deeps

The main access to Mufulira mine is via Kanono shaft and Lubwe shaft, while access to Mufulira west and Mufulira East is through portals. Lubwe shaft serves as the main air intake as well as men, material and ore conveyance system. Kanono shaft serves as air intake, material and waste hoisting shaft. The two shafts have a depth of 600m. The Musombo sub vertical shaft accesses the areas below 500m mining level up to 1340m mining level. The production section below 1340m level is referred to as the Deeps section of Mufulira Mine. Other production sections accessed via Lubwe shaft are Upper, Pillar and Central. Primary access to the Deeps section of Mufulira mine is a single 5m wide x 4.8 m high decline. The decline serves as the main fresh air intake as well as the main men, material and rock conveyance. The decline can accommodate an AD55 dump truck, which is the biggest trackless unit. The decline is inclined at 8 degrees and it lies 78 meters away from the ore body in a South–West and North-East orientation and perpendicular to the principal stress axis. In this position the only the south portions of the decline will be exposed to principal stress. The decline has been designed in such a way as to maximize truck haulage cycle times. (See picture 1 below) (Bibliography 45)

The deeps section is a production section and comprises of the following levels

- 1357m mining level
- 1373m mining level
- 1390m mining level
- 1400m mining level
- 1407m mining level
- 1423m mining level
- 1440m mining level
- 1423m mining level
- Decline

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Picture 1: Decline layout in the deeps section

2.2 The Development Process

Development by definition is the process of making four by four meters (4 x 4 meters) and at times four point eight by five point five (4.8 x 5.5 meters) drives in order to access the ore body (copper). The types of development used at MCM include conventional (jack hammer) and mechanized (Boomer). This report will look at conventional flat jack hammer development. Development takes place at development ends (production sites) (Bibliography 44)

The management structure for the deeps section is illustrated below. The mine captain is the most senior official. He is supported by three section bosses and the latter communicate with 2 heavy mobile equipment operators and 2 miners in charge at operations level. Underneath this hierarchy of management are various miners in charge and Operators who supervise the timbermen, general workmen, trammers (low-skilled) assigned to the various different parts of the deeps section. (Diagram 1)

MOPANI COPPER MINES PLC
MUFULIRA MINE SITE – MINING DEPARTMENT
PROGRESSION CHART FOR MINING PRODUCTION SECTION

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Diagram 1: Deeps production organogram

The following activities are involved in conventional development process;

(Diagram 2)

- Ventilating
- Barring down
- Watering down
- Scaling down
- Lashing to expose the lifters
- Establishing the grade and direction lines
- Drilling
- Charging & timing
- Tramming and Hoisting

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The Development Process

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Diagram2: Development

2.3 Activities

2.3.1 Ventilation

Ventilation is the provision of fresh air through the use of fans, it is very vital to mining; it is therefore, incumbent upon the miner in charge to ensure that all the fans in the section where he and his men would operate from are in a good working condition. Otherwise he has to report to the electricians to have the problem rectified. (Bibliography 30)

2.3.2 Barring down

Barring down is the removal of loose hanging rocks at development ends which may fall and injure employees. It takes place before and during the shift. Leaving his men (at least 5) at the waiting place, the miner in charge carries his rubber guarded pinch bar and proceeds to the development face barring down all the loose rocks he encounters on his way. While at the development face, he bars down all loose hangings towards the face and back. (Bibliography 27)

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Picture 2: Barring down with a pinch bar

2.3.3 Watering down

This is the spraying of water at the development ends; it suppresses dust, cools the area as well as dissolving the remnant fumes and gases. It also helps to expose the loose rocks which might not have been seen whilst barring down. This exercise is carried out by atleast 2 general workmen.

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Picture 3: watering down

2.3.4 Lashing to expose the lifters

Lashing is the removal of ground to expose the whole length of the jumper (blasted area) and to basically look for explosive misfires and treat them if any exist. They then make a drain to allow water to flow away from the face. After making sure that the workplace is safe, the crew (At least 5) then prepares the face for development. The end preparation crew extends one vent duct to a distance of about 5 metres from the face so that the air can sweep the face. The end preparation crew also extends the service pipes to a distance of about 20 metres from the face (Image). The miner in charge and his men lash three metres from the face. (Bibliography 30)

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Picture 4: Lashing

2.3.5 Establishment of the Direction and Grade lines

The miner in charge establishes the direction and guide lines by marking the Grid lines and the holes to be drilled at the face according to the approved drill pattern. They are marked as follows;

- Guide lines in the roof
- The support holes (picture 5)

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Picture 5: Marking of the Direction and Grade line

2.3.6 Drilling

This step involves drilling of holes at the development end where explosives are inserted. The drilling crew consists of 3 drillers, 3 helpers, 2 spannermen and a miner in charge. The miner in charge and his crew bring the drilling machines (jackhammer) and all drilling accessories at the face and connect up. They then erect a drilling platform using the Camlok props. (Bibliography 30)

Picture 6: Jackhammer drilling process

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Picture 7: Installation of carmlock props

Drilling with a jack hammer

2.3.7 Charging and timing

Charging is the firing or lighting of the explosives; the miner in charge and his crew (at least 7) would then collect the correct amount of explosives from the magazine and transport them to the face and then insert them into the holes observing timing by detonator delay numbers. The miner in charge then charges (fires) the rest of the holes using Emulsion or Anfex (explosives). (Bibliography 30)

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Picture 8: Charging and timing

2.3.8 Blasting

The miner in charge ensures that all the men not involved in blasting operations are removed from the sections at least 30 minutes before blasting time. The section boss being the person who appears in the blasting schedule would then light his end as per the Blasting Schedule of the section and blast. (Bibliography 45)

2.3.9 Tramming and Hoisting

This is the part in the development process which involves transportation of the blasted copper ore from the development ends to surface. The tramming crew is composed of the Loco driver, whistleman and Section Boss. Tramming involves dumping and hauling of ground using equipment such as wheelbarrows, loaders, dumps trucks, hoists and locomotives. The copper is dumped either directly into the mobile equipment or into tips which connects to shooting boxes, conveyors and crushers. Hoisting involves use of skips to transport the ore from underground to surface. This is the part were heat from the equipment is introduced into the work area from the mobile equipment. (Bibliography 30)

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Picture 9: Tramming with a loader

Development operations using a jackhammer take 3.5hours. Jackhammer crew consists of a driller, a helper, a miner-in charge and support crew for pipes (at least 5 Timber man and 2 Helpers). All the above activities are supervised by the Section Boss or where there is shortage of labour the miner-in charge reports to the Shift Boss. (Bibliography 45)

3. IDENTIFICATION OF HAZARDS

A risk assessment was done through monitoring of the working conditions using a whirling hygrometer and an IR thermometer, a walk through survey was also conducted. Non structured one to one interviews were held with the mine captain, shift boss, miner in charge and some workers which were randomly selected. The following hazards were identified together with their control measures;

3.1 Hazard 1 – Silica Dust

Task – Blasting, tramming and hoisting resulting in r espiratory diseases due harmful silica dust exposure.

All employees at the deeps are potentially exposed to high levels of respirable dust containing silica during from blasting, tramming and hoisting of the copper ore. The drillers and support crew work in areas of inadequate ventilation coupled with humidity and temperature. These prevailing conditions may compel most employees to work without respirators or only wear them when they feel the area is concentrated with dust. Therefore respirable dust is inhaled for a good number of their working hours.

There are three (3) types of silicosis which depends on the rate at which the lungs gets overloaded with dust and gets scared; simple (limited obstruction/restrictive defects); chronic (10+years); accelerated (5-10 years) and acute (2 months to 2 years after exposure). (Appendix 10, 11)

Exposure to silica (<7 microns) inflames the lung, leading to fibrosis and scarring of the lung tissues which restricts oxygen transfer to and from the lungs, and cardiovascular system. The results of such pathologies range from respiratory irritation, shortness of breath, cough, fatigue, fever, lack of sleep and nausea; to more severe versions of the symptoms mentioned and death.

Existing Control Measures

Existing controls can be summarized as follows:

- Continuous watering down of the development ends to suppress dust
- Automatic water sprays located on conveyor belts, transfer points
- Annual lung function tests, records kept for 5 years for individuals, in accordance with Zambian Mining Regulation (Bibliography 16)
- Training on the harmful effects and management of silica dust (486 out of 540 workers attended, including contractors) (Safety and Occupational Hygiene Annual Report 2012)
- Use of respiratory protection equipment

3.2 Hazard 2 – Noise

Task: Short term/Permanent Hearing loss caused by drilling and blasting.

Noise is almost ubiquitous in mining. It is generated by drilling, blasting, cutting, materials handling, ventilation, crushing, conveying and ore processing. All employees involved in these activities are exposed to noise. Controlling noise has proven difficult in mining and noise-induced hearing loss remains common. Short term noise exposure may cause irritation, tinnitus, ‘ temporary threshold shift ’ (TTS) in the frequency of hearing; (a ‘dip’ of 4 kHz). Prolonged exposure, may cause the cilia hair cells within the inner ear (the cochlea) to become permanently damaged (permanent threshold shift- PTS). Unlike TTS, where the hair cells flatten for a limited period of time, PTS is irreversible. (Bibliography 1)

Existing Control Measures

- Double silencing of all force and exhaust fans underground to reduce noise.
- Continuous maintenance of drilling machines to reduce noise.
- Routine surveys by the occupational hygienist to determine the noise levels and recommend remedial measures.
- Noise hazard training at least covered during induction for both newly and those already in employment.
- Further audiometry tests are provided to workers in accordance with Occupational Health and Safety Regulation of 2010.
- It is also a mandatory requirement for employees to wear ear plugs/muffs for hearing protection. (Appendix 18)

3.3 Hazard 3 – Manual Handling

Task: Manual Handling

Trammers, workmen and timbermen shovel copper ore into wheel barrows in restricted spaces in development ends and throw 5kg mill balls 2.5m into the tips. Repetitive lifting, throwing, stooping, twisting, side bending, gripping and pushing, have the potential to cause muscleoskeletal disorders (MSD). These include bulging/prolapse/thinning of spinal discs; ligament sprains to the posterior/anterior spinal longitudinal ligaments; sciatica of the lumbar region. Sprains and strains to ligaments and tendons of the upper and lower limbs may also occur. (Bibliography 5 ). Work Related Upper Limb Disorders (WRULD) includes frozen shoulder to the rotator cuff muscles; Trigger Finger and Carpal Tunnel Syndrome, epicondylitis of the lateral collateral ligaments and peritendonitis/tenosynovitis of the forearm. (Appendix 14)

Existing Control Measures

- Mandatory use of gloves by all manual handlers.
- Hard hats and safety boots are used to protect the employees from the ‘traumatic’ effects of manual handling.
- Risk assessments, method statements and training in manual handling have been undertaken; Attempts have been made to ‘avoid’ or minimise lifting and carrying using wheel barrows for transporting copper ore into loaders, dump trucks and locomotives, with regular short breaks and stretching exercises to minimise WRULD’s. (Bibliography 26)

3.4 Hazard 4 - Vibration

Task: Whole body vibration caused by drilling and operation of mobile equipment

Whole body vibration may be experienced whilst operating mobile equipment, such as loaders and dump trucks. This can cause or exacerbate pre-existing spinal disorders. Hand–arm vibration syndrome is also encountered with the use of vibrating tools such as air leg rock drills. HAVS follows from exposure to vibrations in the range 2–1500 Hz which causes narrowing in the blood vessels of the hand, damage to the nerves and muscle fibers, to bones and joint (31) evidenced by pain and stiffness in the joints of the upper arm. The impaired circulation of blood to the fingers leads to a condition known as vibration white finger (VWF). The most damaging frequency range is 5–350 Hz. (Appendix 9)

Existing Control Measures

Occupational Hygiene tests confirmed that vibration levels do not exceed best practice exposure values 1.15 m/s2 A (8) daily exposure limit value; 0.5 m/s2 A(8) daily exposure action value for whole body vibration. Health surveillance with remedial treatment is administered by the local hospital with relevant vibration awareness training. (Bibliography 23)

3.5 Hazard 5 - Illumination

Task – exposure to inadequate illumination during the development process resulting into eye illnesses such as nystagmus.

Working in development ends exposes employees to low levels of light. Nystagmus is a condition of involuntary eye movement, acquired due to working in areas with inadequate lighting; it may result in reduced or limited vision. Due to the involuntary movement of the eye, it is often called "dancing eyes". This occupational disease is unique to underground mining workers. (Bibliography 1)

Existing controls

- No miner is allowed to go underground without cap lamp; this allows miners to have adequate illumination in development ends.
- Eye examination is part of annual medical checkups which is mandatory to all underground workers.
- Occupational nystagmus has long been regarded as essentially nonexistent in Zambia. However, among jewelers, draftsmen, hand compositors, and similar close work tradesmen, nystagmus has occasionally been encountered; but none has been noted among miners.

3.6 Hazard 6 - Heat

Task – use of heavy duty diesel mobile equipment resulting in exposure to extreme Heat

The temperatures are mainly caused by auto compression, heat conducted through rock strata and fissure water; toxic fumes from blasting and exhaust fumes from diesel equipment i.e. loaders and dump trucks.

The working conditions are further worsened by leaking ventilation ducts, air resistance in airways, wrong installation and positioning of the fans and recirculation of air .These high temperatures reduces productivity and has an adverse effect on the health and safety of underground personnel. (Bibliography 5)

Existing Controls

- Installation of ventilation fans to control temperature.

From now forthwith the rest of the report will be concentrated on heat a major health hazard at deeps section which has not been adequately addressed and controlled even though the severity is enormous.

3.7 Justification for selection

Recent research has indicated that the working areas in the Deeps sections have been experiencing unsatisfactory working environments caused by high wet bulb temperatures. The temperatures are mainly caused by auto compression, heat conducted through rock strata and fissure water; toxic fumes from blasting and exhaust fumes from diesel equipment.

The working conditions are further worsened by leaking ventilation ducts, air resistance in airways, wrong installation and positioning of the fans and recirculation of air .These high temperatures reduces productivity and has an adverse effect on the health and safety of underground personnel.

The results of the thermal conditions at deeps showed higher wet bulb temperatures exceeding the Occupational Exposure Limit (OEL) of 31 degrees Celsius and thus posing a huge risk to the employees subjected to these conditions during their working hours. According to the shifts it can be deduced that employees are exposed to these hash conditions for at least 4 working hours.

Statistically, in the year 2013, the mine site clinic recorded 35 heat exhaustion conditions and 57 other heat related illness from deeps alone. This is an indication that heat is a serious hazard underground at Mufulira Mopani site. (Appendix 12)

High levels of humidity –usually in excess of 80% RH – can seriously impede the evaporation of sweat, thus reducing the body’s ability to lose heat. In this way the effects from high humidity work activities can lead to the effects heat. The effects can range from heat rash to heat stroke which can be very fatal.

It is further imperative to note other consequences emanating from higher temperatures and humidity levels. This is because the outright decision made when conditions exceed OEL is stoppage of work until remedial actions are taken to bring the situation back to normal. When that happen production hours are lost to the detriment of the company’s profit sufficing to mention that the repercussions of heat stress may be beyond. Continuous subjection of workers to higher temperatures and humidity may lead to breaching of the statutory regulations and laws with a potential of tarnishing the corporate image as regards to the safety and welfare of its employees.

Remedial actions to address heat stress have not been adequate and effective in comparison to those that address other hazards noted, probably because such measures are slightly expensive to implement for instance installation of ventilation systems of adequate size and capacity and recruitment of more workers to reduce on the working hours.

4. BACKGROUND RESEARCH

4.1 History of Heat stress

The oldest known mine on archaeological record is the "Lion Cave" in Swaziland, which radiocarbon dating shows to be about 43,000 years old. At this site paleolithic humans mined hematite to make the red pigment ochre. Mines of a similar age in Hungary are believed to be sites where Neanderthals may have mined flint for weapons and tools. (Bibliography 42)

Ancient Egyptians mined malachite at Maadi. At first, Egyptians used the bright green malachite stones for ornamentations and pottery. Later, between 2613 and 2494 BC, large building projects required expeditions abroad to the area of Wadi Maghara in order "to secure minerals and other resources not available in Egypt itself. Quarries for turquoise and copper were also found at "Wadi Hamamat, Tura, Aswan and various other Nubian sites on the Sinai Peninsula and at Timna. It was during the Egyptian mining error when the issues of heat related illnesses started to be seen. The deeper they went underground the more cases of headaches and fainting increased. It was later realized that the high temperatures was contributing to the headache and fainting cases. (Bibliography 31)

Mining in Egypt occurred in the earliest dynasties. The gold mines of Nubia were among the largest and most extensive of any in Ancient Egypt. In order to combat heat stress, miners went underground with big water containers and access to the mines were made big to allow adequate air to go in. (Bibliography 37)

illustration not visible in this excerpt illustration not visible in this excerpt Picture 10: Early underground coal mines Picture 11: Early Egyptian copper mines

According to the United states Bureau of Labor Statistics (BLS) Census of Fatal Occupational Injuries (CFOI) data, 230 heat-related deaths have occurred from 2003 – 2009 with 81 (40%) of these fatalities in the mining industry. Over that same time period, 15,370 heat-related injuries/illnesses requiring days away from work have occurred with 4,110 (27%) of these injuries/illnesses in the mining industry. (Bibliography 44)

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4.2 Health effects of working in hot and humid conditions

Workers who are exposed to extreme heat or work in hot environments may be at risk of heat stress. Exposure to extreme heat can result in occupational illnesses and injuries. Heat stress can result in heat stroke, heat exhaustion, heat cramps, or heat rashes. Heat can also increase the risk of injuries in workers as it may result in sweaty palms, fogged-up safety glasses, and dizziness. Burns may also occur as a result of accidental contact with hot surfaces or steam. (Bibliography 14)

Workers at risk of heat stress include outdoor workers and workers in hot environments such as fire-fighters, bakery workers, farmers, construction workers, miners, boiler room workers, factory workers, and others. Workers at greater risk of heat stress include those who are 65 years of age or older, are overweight, have heart disease or high blood pressure, or take medications that may be affected by extreme heat. (Bibliography 14)

Prevention of heat stress in workers is important. Employers should provide training to workers so they understand what heat stress is, how it affects their health and safety, and how it can be prevented. (Bibliography 14)

4.3.1 Heat oedema

This is swelling, particularly of the feet and ankles. It usually occurs among those employees that are not acclimatized to the heat in the first week of exposure. This is usually alleviated by rest or on returning to a cooler environment. (Bibliography 13)

4.3.2 Prickly heat (heat rash)

Prickly heat appears in red papules on the skin usually in areas where the clothing is restrictive. It gives rise to a prickling sensation, particularly as sweating increases. It occurs in skin that is persistently wetted by unevaporated sweat, apparently because the sweat ducts become blocked (Bibliography 15). The papules may become infected unless they are treated.

Heat rash is not dangerous, although it may result in patchy areas which are temporarily unable to produce sweat. (Australian coal mines (Rogan 1972), Yugoslavian mines (Bibliography 13)

In most cases the rashes disappear when the individual is returned to cool environments. It is also thought likely that none of the rashes occur when a substantial part of the day is spent in cool and/or dry areas so the skin surface can dry (Bibliography 11).These heat rashes are not dangerous, although they may result in patchy areas which are temporarily unable to produce sweat. This may adversely affect evaporative heat loss and thermoregulation, and prickly heat has been shown to decreases tolerance to heat and reduce work capacity (Pandolf et al 1980a, 1980b). Sweating capacity has been shown to recover within 3-4 weeks of prickly heat. (Bibliography 12)

4.3.3 Heat cramps

Heat cramps (painful muscle spasm) may occur in individuals working in the heat. They are caused by salt deficiency when salt is lost during severe sweating and large amounts of water are taken without replacing the salt. The condition may have a delayed onset and is most likely in people who are not acclimatised to hot work or who have a low dietary salt intake. Cramps usually occur in the muscles principally used during work (limbs) or stomach. They can be alleviated by rest, the ingestion of water and the correction of any body fluid electrolyte imbalance, or by putting the effected muscle "on the stretch" and applying gentle massage to the area. Adequate salt intake with food should prevent this occurring. (Bibliography 10)

4.3.3 Temporary infertility

Heat exposure has been associated with temporary infertility in both males and females, with the effects being more pronounced in males (Bibliography 6). Heat related infertility is usually temporary, reduction in heat exposure or job transfer should result in complete recovery.

4.3.4 Heat fainting

Heat syncope occurs when blood pools in the lower parts of the body, causing a temporary reduction in blood supply to the brain and hence a short term loss of consciousness It is more likely to occur in the unacclimatised during early exposure to the heat. Recovery should be rapid if the patient lies down and his legs are raised above his head. However, it can become serious if the patient is held upright or injured in a fall, in which case brain damage or death may occur. (Bibliography 25)

4.3.5 Heat exhaustion

Heat exhaustion is a mild response to exposure to hot environments. It results from a combination of thermal and cardiovascular strain. Symptoms include:

- A feeling of being unwell, including tiredness, headaches, dizziness, nausea and vomiting
- Breathing difficulties / shallow rapid respiration
- Rapid pulse which may be bounding or weak
- Extreme thirst and mouth dryness
- Muscle cramps, particularly effecting the stomach and legs
- Poor control over movements / stumbling / weakness
- Irritability

Heat exhaustion is sometimes, but not always accompanied by an increase in body temperature (38- 39°C). Dehydration or, less commonly, salt deficiency may contribute to the development of heat exhaustion. Heat exhaustion in turn may predispose the worker to heat stroke. Heat exhaustion usually responds positively to prompt treatment. Data suggest that heat exhaustion is likely to occur some 10 times more frequently than cases of heat stroke (Bibliography 24)

4.3.6 Heat stroke

This is the most serious of all heat related illnesses and may occur when the body core temperature exceeds 41oC (it may reach 45oC), and the coordination of the involuntary nervous system including thermal regulation is affected. Irreversible injury to the kidneys, liver and brain may occur. Heat stroke carries a high risk of fatality from cardiac or respiratory arrest, and must be treated as a medical emergency. (Bibliography 10)

Some symptoms of heat stroke are similar to those of less serious heat illnesses, ie headaches, dizziness, nausea, fatigue, thirst, breathlessness and palpitations, but the onset of illness may be sudden and dramatic. (Bibliography 10)

Additional symptoms of heat stroke can include:

- Cessation of perspiration, the skin remains hot but is dry and may adopt a blotchy and red colouration, and the lips may take on a bluish tinge
- Disorientation, which may become severe, including dilated pupils, a glassy stare and irrational aggressive behaviour
- Shivering and other uncontrolled muscular contractions
- Loss of consciousness and convulsions

4.3.7 Illnesses exacerbated by heat

Because work in the heat increases the load on the body, in particular the circulatory system, illnesses affecting this system may well be exacerbated by work in the heat and these may affect the individual's ability to work in the heat. Some other illnesses may be exacerbated by hot conditions, while not rendering the individual unsuitable for the work. Two examples of this are dermatitis and fungal infections. (Bibliography 10)

Dermatitis is a very common skin condition resulting from irritation and inflammation of the skin by external causes (eg. abrasive dusts). Sweating softens the outer layer of skin and reduces its effectiveness as a barrier to irritants. PPE and clothing may add to the problems by occluding chemical agents against the skin and therefore increasing uptake, or by mechanical abrasion. Avoiding tight clothing, regular replacement of badly soiled clothing, and good personal hygiene help reduce the risk of having dermatitis conditions. Fungal infections are promoted by heat and humidity and therefore, tend to occur in areas of the body where such conditions are most pronounced, such as between the toes (athletes foot) or in the groin or

axillae (arm pits). Good personal hygiene, possibly enhanced by the use of an anti-fungal powder is usually effective in preventing or treating such conditions. (Bibliography 10)

4.4 Legal Requirements

4.4.1 Zambia; Occupational health and Safety Act of 2010

Under this Act the employer has a duty to place and maintain an employee in an occupational environment adapted to the employee’s physical, physiological and psychological ability. Further, provide and maintain a working environment for the employee that are, so far as is reasonably practicable, safe and without any risks to their health and safety, and which is adequate as regards facilities and arrangements for their welfare at the workplace. (Bibliography 18)

4.4.2 Zambia; Mining and Mineral regulations Act 213

Mining Regulations 902(2) considers ventilation to be adequate if:

a) Ensures that the amount of oxygen in general body of the air is not less than 19% by volume.
b) Ensures that the amount of carbon dioxide, carbon monoxide, nitrous fumes, sulphur dioxide and hydrogen sulphide in the general body of the air do not exceed the quantities set out against each such gas;
c) Dilutes or removes any other toxic gas or fume so that the amount of such gas or fume in the general body of the air conforms to the requirements prescribed, from time to time, by the chief Inspector;
d) Dilutes or removes any harmful dust so that the amount of such dust in the general body of the air conforms to the requirements prescribed, from time to time, by the chief inspector;
e) Maintains working conditions free from dangerous temperature at high relative humidity in the general body of the air; and
f) Provides any diesel unit with not less than 0.05 cubic metres of air per kilowatt for the purpose of diluting or removing any toxic gas or fume in the general body of the at places where such diesel units operates. (Bibliography 16)

4.4.3 Zambia; Factory act 441

Section 89 under the Factory Act of Zambia elucidate effective steps to be taken to secure and maintain the adequate ventilation of every working place in any excavation, pit, hole, tunnel, shaft, caisson, or other enclosed space so as to maintain an atmosphere which is fit for respiration; and to render harmless all fumes, dust or other impurities which may be dangerous or injurious to health. (Bibliography 3)

4.4.4 United Kingdom (UK); Health and Safety at Work Act 1974

Sections, 2, 3 and 4 provides the general duties for employers to ensure the health and safety of employees and others who may be harmed by exposures to poor thermal conditions while at work; Employers must ensure (so far as is reasonably practicable) that workplaces are safe and that safe systems of work are developed and implemented to protect persons from the effects of working in extremes of heat, cold or humidity (Bibliography 7)

4.4.5 United Kingdom (UK); Management of Health and Safety at Work Regulations 1999

Provide protection by requiring employers to carry out assessments of the risks arising from the work activities. Employers are duty-bound to identify and evaluate risks from working in these extreme conditions and must ensure that appropriate arrangements are in place for the effective planning, organization, control, monitoring and review of the preventive and protective measures needed to safeguard workers exposed to such conditions.

4.4.6 United Kingdom (UK); Workplace (Health, Safety and Welfare) Regulations 1992

State that there should be reasonable thermal comfort for employees. The Approved Code of Practice to the regulations helps the employer to interpret ‘reasonable’ by giving suggested suitable standards for the amount of fresh or purified air required for workplaces and for minimum temperatures in the workplace. (Bibliography 26)

4.4.7 Zambia; Mines Safety Department (MSD)

The Department is divided into four technical sections - Mining, Explosives, Machinery and Environment - which variously enforce the relevant legislative and statutory instruments, formulate new legislation and regulations, evaluate all aspects of safety in mining operations, offer technical advice and training, and offer exemptions from the relevant regulations where appropriate. The following are the recommended MSD temperature limits which all Zambian mines must comply to; (Bibliography 45)

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Key

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MSD has also enforced 31.0oC as the wet bulb Occupational exposure temperature limit (OEL) to which all Zambian underground mines must comply.

4. 5 Case Law: Watson v. Sam Knight Mining Lease

In the case of an employee who suffered fatal heat stress at work, by this proceeding the Commission denying petitioner's claim for death benefits provided in the Workmen's Compensation Act. A.C.A. 1939, § 56-901 et seq was reviewed. The Commission, by its award, found that the deceased husband and employee had died July 1, 1953, "as a result of acute heart failure due to heat exhaustion" "not the result of an injury by accident arising out of and in the course of his employment."

The facts leading up to the death show that the decedent had been in his then employment several years as an employee above ground around the mine workings and mill at Winkleman, Arizona. During the forenoon of the day preceding death the decedent had worked in the mill crusher section. The day was referred to as very hot, 109oC -110oC, with very little humidity. After lunch Mr. Watson was told to get some sand and cement for a repair job in the mill. The sand was loaded by shovel from a hillside some 400 feet from the mill, by another employee. Watson acted in the capacity of truck driver while sand was being loaded Watson made numerous trips to a water bucket located inside the machine *116 shop, a few feet distant. It appeared to one witness that the decedent was drinking an inordinate amount of water; although Watson did not disclose to anyone that he was not well, nor did his condition reveal itself to anyone present. On bringing the sand, gravel and cement the decedent mixed a 5-gallon can of dry sand and cement, out in the open. The mix was completed inside the mill by the addition of water without the aid of decedent. When the mixture was completed decedent grouted in three or four piers under some "I" beams located inside the mill building. At 4 o'clock (end of shift) deceased left for home. The employer reported that both he and Watson were sweating freely at the time the work was performed. On arrival at home Watson told his wife that the heat off the sand and cement had made him deathly sick. He immediately drank a glass of cold water, some lemonade and divided a can of cold beer with his wife. In addition he drank a glass of Alka Seltzer and later tried to drink some ginger ale. Throughout the evening and night he was in great pain, very restless, and continually wanting water which he could not keep down. A doctor was called but did not come although he prescribed some capsules which were taken and vomited up. With each seizure of pain he experienced cold sweats. Early next morning he was removed to the hospital at Globe, Arizona, a distance of sixty-three miles. On arrival at the hospital he was unconscious and in a state of shock "apparently from congestive heart failure." The attending physician could not feel or count his pulse or hear his heart through the stethoscope due to so much noise from his breathing. He did not respond to oxygen and heart stimulants and died approximately one hour and forty-five minutes after arrival at the hospital. The doctor's death certificate (printed form) report in part read:

"Medical Certification

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Kimsey Heating & Plumbing Co. v. House, 1931, 152 Okl. 200, 4 P.2d 59. It is there said:

"If the place of the employee's work, by reason of its location, nature, and climatic condition, would likely expose him to the danger of heat exhaustion, overheating, or heat exertion, or if the risk of injury by heat exhaustion, overheating, or heat exertion is naturally connected with and reasonably incidental to his employment, as distinguished from the ordinary risk to which the general public is exposed from climatic conditions, the employer will be liable for the consequential injury." (Bibliography 42)

In this case it is clear that heat exhaustion contributed to the death of the employee, this case is significant in that it clearly indicates that heat mismanagement has legal consequences such as;

- Criminal; leading to imprisonment of employer
- Civil; leading to closure of company or compensation claim
- Employee liability; leading to company being sued by its own employees

The above further leads to moral and economic effects such as;

- Loss of employee morale
- Family effects; due to death of their breadwinner
- Loss of skilled manpower
- Loss of production

Therefore in conclusion this case in tells that proper heat management is a critical responsibility for employers with high risk heat exposure operations such underground mining.

5. ASSESSMENT OF RISKS

5.1 Methodology

A risk assessment was done through monitoring of the ambient environmental conditions working conditions using a WBGT whirling hygrometer and a walk through survey. Non structured one to one interviews were held with the shift boss, miners in charge and some workers randomly selected.

A review of the current stipulated laws and regulations pertaining to prevention and control of heat stress was undertaken to assess its effectiveness. Further, documentation system and the current existing control measures were reviewed to determine their significance.

5.1.1 Temperature Survey (Bibliography 38).

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Figure 1: whirling hygrometer

Measuring procedure:

- The airstream was faced and held the instrument at arm’s length in front of the body.
- The hygrometer was whirl at a rate of approximately three revolutions per second to give an air velocity past the bulbs of about 3 m/s
- After whirling the hygrometer for 30 seconds, the two temperatures were read as rapidly as possible. The wet-bulb temperature was read first as it tends to rise when whirling ceases.

5.1.2 Psychrometer with IR Thermometer (temperature and humidity survey)

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Figure 2: Psychrometer with IR Thermometer

Measuring procedure:

- The infrared pointer was pointed at the site to measure temperature and humidity, the instruments gave instant results. To take the reading the hold key was pressed on the instrument.
- The pointer of the instrument was pointed to all the areas of the area in question to take the average reading.

5.1.4 Limitations

- Sections of the site were not in full operation due to maintenance, so not all heat hazards could be observed in its entire context.
- Some of the Plant workforce, including the Underground mangers and Mine captains, were unable to answer all relevant questions. This may be due to their perception of ‘blame’ culture, and the reluctance to divulge data which may incriminate them. Other reasons included a lack of competence in health and safety management matters.
- As this report has been conducted by an Occupational Hygienist who is in the Health, Safety and Environment (HSE) department, access to further interviews and paperwork were restricted because Mining department could not release certain information and certain sites of the study site could not be visited. As a result, where critical information had not been provided, an assumption of lack of compliance was concluded.

5.2 The Assessment Results/Findings

A thermal environmental survey conducted by the occupational hygienist showed average humidity percentage of 86.3. All the wet bulb temperatures exceeded the occupational exposure limit of 31.0oC.

Zambia Mines Safety Department (MSD) Emergency Heat Stress Index Chart (EHSI) outlined on section 4.4 of this report was used to come up with risk ratings of the findings below. Occupational Hygiene results indicated Heat exposure rating of “High Risk”. Almost all the areas monitored by Ventilation section showed risk rating of “High Risk”.

5.2.1 Occupational Hygiene Monitoring Results

All the Occupational Hygiene monitoring results were taken using an IR thermometer

Table 1: Occupational Hygiene Results

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Graph 1: Occupational Hygiene Results

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Average Reading = 36.2oC (wet bulb)

Average Humidity = 86.3(%)

Risk Rating = High Risk

The above results taken by Occupational Hygiene section exceeded Occupational Exposure Limit of 31oC and showed that there is high risk heat exposure to individuals at Deeps.

5.2.2 Ventilation Section Temperature Results

All ventilation temperature results were taken using a whirling hygrometer.

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Average Reading = 32.1oC (wet bulb)

Risk Rating = Medium Risk

The above results taken by Ventilation section exceeded Occupational Exposure Limit of 31oC and showed that there is medium risk heat exposure to individuals at 1420mL fresh air intake.

Graph 3: 1423mL Entrance Cross Cut North

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Average Reading = 32.6oC (wet bulb)

Risk Rating = Medium Risk

The above results taken by Ventilation section exceeded Occupational Exposure Limit of 31oC and showed that there is medium risk heat exposure to individuals at Deeps 1420mL fresh air intake.

Graph 4: 1423mL Face

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Average Reading = 33.9oC (wet bulb)

Risk Rating = Medium Risk (threshold ‘near high risk’)

The above results taken by Ventilation section exceeded Occupational Exposure Limit of 31oC and showed that there is medium risk heat exposure to individuals at Deeps 1423mL fresh air intake.

Graph 6: 1440mL Entrance Cross Cut North

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Average Reading = 33.5oC (wet bulb)

Risk Rating = Medium Risk (threshold ‘near high risk’)

The above results taken by Ventilation section exceeded Occupational Exposure Limit of 31oC and showed that there is medium risk heat exposure to individuals at Deeps 1420mL.

Graph 5: 1440mL Face

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Average Reading = 35.8oC (wet bulb)

Risk Rating = High Risk

The above results taken by Ventilation section exceeded Occupational Exposure Limit of 31oC and showed that there is high risk heat exposure to individuals at Deeps 1440mL face.

Graph 7: Decline Face

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Average Reading = 34.5oC (wet bulb)

Risk Rating = High Risk

The above results taken by Ventilation section exceeded Occupational Exposure Limit of 31oC and showed that there is high risk heat exposure to individuals at Deeps decline face.

5.2.3 Heat Load from Diesel Powered Equipment

Mufulira mine runs several loaders, dump trucks and mobile equipment of various makes and sizes. The mine and mineral acts require that a mine should provide 0.05m³/s of ventilation air per kilowatt of engine power. However, typical ventilation requirements for acceptable operation of diesel equipment are 0.035m³/s ‘over the engine’ per kilowatt power. The heat generated by diesel equipment has been calculated based on their total rated power and amount by which it is used. (Appendix 3)

Table 9: Heat generated by diesel equipment

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Assuming 80% availability 3,139kW is the heat estimated from diesel powered equipment.

5.3 Identification of heat stress hazards

The miners in charge, timbermen, support crew, loader driver, jackhammer crew, tramming crew, general workmen, shift and section bosses are exposed to temperatures as high as 36oC (high risk) far beyond the occupational exposure limit of 31oC. Such high temperature can seriously impede the evaporation of sweat, thus reducing the body’s ability to lose heat. In this way the effects from high humidity work activities can lead to the effects heat. The effects can range from heat rash to heat stroke which can be very fatal. (Appendix 7)

The most notably contributing factors to such high temperatures may include the natural hot water at 1440ml from rock strata which is not pumped out due to lack of hot water pumping pumps. Secondly, temperatures increase in relation to the depth. Thus the deeper you go the higher the temperatures. This is normally due to the geothermal temperature gradient created by the rock strata. (Appendix 4,5 )

5.4 Evaluation of Existing Controls

The apparent control measure of high temperatures at the deeps is the installation of fans whose capacity cannot equal the demand. Currently the 2 air intakes deliver a total of 70m3/sec of air but the actual air which should go to deeps is 200m3/sec, 100m3/sec from each air intake. Therefore, there has been a deficiency of 130m3 /sec to reverse the adverse thermal conditions back to normal.

The Mopani Safety and Health Policy lack specific reference and commitment to addressing high temperatures in working areas. (Appendix 1)

The reporting and surveillance systems of the occupational health sections have not been adequate and effective to document and evaluate the statistics of heat related illnesses. Apart from measuring the thermal conditions using the whirling hygrometer and psychrometer (with inbuilt thermometer), there has been no other methodologies/assessments to accurate define the magnitude of thermal conditions at the deeps. To qualify the fore mentioned statement, examples include the inability to measure and document the working rates/metabolic rates of loader drivers, jackhammer crew, support crew, crew boss, section and shift boss. Similarly the heat produced by mobile equipment’s for instance dump trucks and loaders have not been measured and adequately given the due consideration. (Appendix 2)

Furthermore, the safety system has not been rigid and effective enough to ensure that the workers at deeps undergo complete acclimatization process prior to full engagement.

The engineering controls have not been able to meet the challenge. The vent raise for air exhaust are small resulting in containment and build-up of heat underneath. The problem is further worsened by a low number of vent raise hence the capacity to handle exhaust air is compromised. The ventilation circuits often times than not have been prone to short circuiting or leakage of air in upper levels and this further adversely affected the ventilation capacity.

5.5 Proposed control measures

The Mopani management has a legal obligation to provide a safe working environment (Bibliography 18, 16) for its employees. This calls for concerted efforts to ensure that thermal conditions are reduced below the acceptable limit of 31oC.

The effects of heat illness must not be taken lightly, and steps must be taken to minimize the impact of the work environment, and to promote safe working practices within it.

5.5.1 Engineering controls

5.5.1.1 Rehabilitation works

The following rehabilitation action needs to be implemented in order to improve the existing ventilation conditions in the Deep section.

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Picture 12: Condition of vent tubes at deeps section

5.5.1.2 Intake airways

- Enlarging of intake raises between 1040mL and 1340mL must be completed as soon as possible.
- Holing the second ventilation intake between 1430mL and 1423mL must be done and the removal of loose rock to be done concurrently.

5.5.1.3 Return airways

In order to achieve the required air flow carrying capacities in the Deep section the following infrastructure is required. The following rehabilitation actions are recommended:

- Complete enlarging of the return raises [6.0m diameter] between 1040mL and 1340mL.
- Mining of 21 internal raises between 1323mL and 1440mL.
- Drilling a 3m diameter ventilation raise between 1340mL and 1457mL next to the internal raise.

Careful attention should be paid to the position and timing of ventilation connections, and the minimizing of leakages between intake and return out bye, to maximize the quantity of air reaching the in bye workings. Working areas of the mine should be provided with an adequate supply of clean air that has not already ventilated another working place, so series ventilation is avoided. (Bibliography 44)

5.5.1.4 Refrigeration Plants

In order to reduce temperature at deeps the air has to be cooled through the use of refrigerators. The refrigerators must be located in refrigeration points which should be strategically located in places such as fresh air intake.

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Picture 13: Refrigeration plant

Installation of refrigeration plants will surely reduce temperatures at deeps (Appendix 15)

5.5.1.5 Control of water to minimize humidity

The management must consider Installation of the piping system to take water to the pump chamber in order to drain off accumulated waters. The hot water can be collected by the same piping system to facilitate dilution with cold water and pumped to the pump chamber.

This can be achieved by eliminating standing water and by minimizing the amount of water that is introduced underground. Obvious water sources include leaks, spillages, excessive sprays, machine cooling water, and natural strata water. Allowing water to accumulate into puddles will also increase the humidity of the passing air, so that should also be avoided. Any spillage should be collected and removed through pipes. Allowing water to merely soak away or dry up is not acceptable. (Bibliography 32)

5.5.1.6 Purchase and Installation of ‘State of the art’ fans

Mopani Copper mine should also consider purchasing new ‘state of the art fans’ which are more powerful than the ones currently in use. The state of the art fans are several times more powerful than the fans currently in use at deeps. This will assist in reduction of temperatures which are remote from fan locations.

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Picture 14: State of the art fan Picture 15: Fan currently in use at Mopani

5.5.2 Organization controls

5.5.2.1 Training and education

There should be adequate training and education of the workforce, including management and supervisors. Training must cover the precautions to be taken, the behaviors to adopt, and the recognition of the signs, symptoms and treatment of heat illness. The training can be tailored such that it can be incorporated into the inductions of new employees and those returning from leave. (Bibliography 17)

5.5.2.2 Hydration

The management should ensure adequate provision of water for drinking to replenish the amounts lost through sweating. Chilled drinking water can be supplied in large containers and strategically positioned where it will be readily accessible.

The implementation of this control measure is the least expensive as the cost relies much on the polythene containers and refrigerants which are moderate in cost expects. (Bibliography 33)

5.5.2.3 Regulating number of heavy duty mobile equipment and employees

Number of mobile equipment and employees at deeps should be regulated in order to regulate temperature. When equipment is not in use, its better it is packed instead of it running aimlessly contributing to heat load at deeps. Number of employees per shift should also be regulated because humans release reasonable amount of heat which contributes to high temperatures at deeps. (Appendix 7)

5.5.2.4 Use of mobile equipment

Mobile equipment must not be left running when not required to avoid excess production of heat. Examples include diesel engines left idling when the vehicle is not being used.

Implementation of this control measure is the least the expensive, as it can be tailored in the induction sessions and morning briefings. Optimizing the running time of such equipment will obviously give financial savings as well. The shift personnel in charge of a particular level may be charged with the supervision responsibility as to effect the implementation of this control measure. (Appendix 3,8)

5.5.2.5 Establishment of Heat zones and proper signage

Through continuous monitoring by the Occupational hygiene and Ventilation sections, heat zones should be established and proper warning signs should be put in place.

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Picture 16: Example of a heat zone sign

5.6 Costs for practical and organizational controls

The cost for renovation the ventilation system, implementing engineering controls; provision of chilled drinking water through large containers and pumping out of accumulated water will cost £47,505,000 . This plan would be implemented over a 1 year period, with savings made due to in-house expertise where applicable.

Table 10: Budget

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5.6 Benefits from ‘Organizational’ and ‘Practical’ Heat Controls

The Heat stress policy commitment, monthly in-house noise awareness inductions and inspections, will encourage staff to cooperate and communicate on a wider range of health matters. Continuous monitoring with feedback, facilitated by employee recommendations, will reduce unsafe practices which can cause heat stress illness.

Timely and thorough risk assessments will reduce the likelihood, severity and number of workers suffering from heat illnesses. This will ensure legal compliance because risk assessments are an absolute duty, thus reducing fines, prison sentences or disruptive notices enforced by Zambian Government Inspectors. (Bibliography 18)

Engineered-based planned preventative maintenance, will reduce adverse temperatures and disruption to processes caused by fan failure, reducing the costs of downtime, while equipment are repaired. (Bibliography 8,9,11)

6. BIBLIOGRAPHY

1. Cvetanov V. (1968). Miliaria rubra as an occupational disease in special conditions of working environment. Arh. Hig. Rada. Toksikol. (Yugoslavia); 19: 223
2. DiBenedetto JP, Worobec SM. (1985). Exposure to hot environments can cause dermatological problems. Occupational Health and Safety; 54: 35-
3. Factories Act Vol. 24 Cap 441 of the Laws of Zambia.
4. Golbabaie F, Omidvari M. Man and Thermal Environment. 3rd ed, Tehran University Press., Tehran, Iran, 2009.
5. Golbabaie F, Alimohamadi IR, Tiagar A. Occupational hygiene in heat workplaces. Tehran University Press., Tehran, Iran, 2002.
6. Graveling RA, Sims MT, Graves RJ. (1986). Intra-abdominal pressure responses of mineworkers tostandard loads. Applied Ergonomics; 17: 105-109.
7. Health and Safety at work Act 1974
8. Health and safety Regulations (First Aid) 1981
9. Heat stress http://www.hse.gov.uk/temperature/heatstress/
10. heat stress in the workplace: A brief guide http://www.hse.gov.uk/pubns/ind451.pdf/
11. Heat stress risk assessment http://www.hse.gov.uk/temperature/heat stress/
12. Kerslake DM. (1972). The stress of hot environment. Cambridge: Cambridge University Press.
13. Khagali M, Hayes JSR. (1983). Heatstroke and temperature regulation. Sydney: Academic Press.
14. Leithead CS, Lind AR. (1964). Heat stress and heat disorders. London: Cassell.
15. Lillywhite LP. (1992). Investigation into the environmental factors associated with the incidence of skin disease following an outbreak of at a coal mine. Occupational Medicine; 42: 183-187.
16. Mines and Mineral Act Vol. 13 Cap 213 of the Laws of Zambia.
17. Training and development (2012), Best Operating Practices-All Mining Operations. Mopani Copper Mines Plc.
18. Occupation Health and Safety Act of 2010, Zambian Laws.
19. Pandolf KB, Griffin TB, Munro EH, Goldman R. (1980). Persistence of impaired heat intolerance from
20. artificially induced miliaria rubra. American Journal of Physiology: 239; 226-232.
21. Rachootin P, Olsen, J. (1983). The risk of infertility and delayed conception associated with exposures in the Danish workplace. Journal of Occupational Medicine; 25: 394-402.
22. Rick BR, Grahan BA. Avalid method for comparing Rational and empirical Heat stress indices. Ann Occp Hyg 2002; 165-174
23. Royal College of Physicians, Hand Transmitted Vibrations, 2 vols, Royal College of Physicians, London (1993)
24. Shibolet S, Lancaster MC, Danon Y. (1976). Heat stroke: a review. Aviation, Space and Environmental Medicine; 47: 73-83.
25. Weiner JS. (1972). Extremes of temperature. In: Rogan JM, ed. Medicine in the mining industry. London: Heinemann
26. Workplace (Health, Safety and Welfare) Regulations 1992
27. A Guide to Mining Regulations, Part (ix)
28. Anon., 1971, “Ventilation Planning as a Prerequisite for Winning Higher Outputs,” Mining Engineer, Vol. 30, Part 12, pp. 796–811
29. Burrows, J., et al., eds., 1982, Environmental Engineering in South African Mines, Mine Ventilation Society of South Africa, Johannesburg.
30. Hartman, H.L., Introductory Mining Engineering, 1987, Wiley Interscience, New York.
31. Hartman, H.L., Mutmansky, J.M., and Wang, Y.J., eds., 1982, Mine Ventilation and Air Conditioning, 2nd ed., Wiley Interscience, New York.
32. McPherson, M. J., 1991, personal communication on Subsurface Ventilation and Air Conditioning (in press).
33. O’Neil, T.J., and Johnson, B.R., 1982, “Metal Mine Ventilation Systems,” Mine Ventilation and Air Conditioning, 2nd ed., Chap. 14.
34. Le Roux, W. L., 1979, Mine Ventilation Notes For Beginners, 3rd ed., The Mine Ventilation Society Of South Africa.
35. Lewis, R.S., 1964, Elements of Mining, 3rd Ed., John Wiley & sons.
36. Roberts, A, 1960, Mine Ventilation, Ventilation planning Chap. 13 P260-261, Cleaver Hume Press Ltd., London.
37. Skochinsky A., Komarov, V., 1969, Mine Ventilation, Translated edition, MIR Publishers, Moscow
38. http://www.mininglife.com/miner/services/mineventilation.htm.
39. http://www.minesafe.org/underground/ventilation.htm
40. Allen C, Keen B, (2008) “Ventilation on Demand (VOD) Project – Vale Inco Ltd. Coleman Mine”, 12th US/North American Mine Ventilation Symposium, Reno, NV.
41. Marx WM et al, (2008) “Development of Energy Efficient Mine Ventilation and Cooling Systems”, Mine Ventilation of South Africa Society Journal, April/June.
42. http://law.justia.com/cases/arizona/supreme-court/1954/5896-0.html
43. Chambers of Mines of South Africa, Measurements in Mine Environmental Control, Johannesburg, 1982.
44. Ventilation and cooling study for Mindola and Mufulira shafts, BBE report 3113.
45. Geology, planning and Ventilation Departments at MCM Mufulira mine.

7. APPENDICES

Appendix 1 - Policy

Note from the editor: Removed due to copyright reasons

Appendix 2 – Occupational Hygiene Sampling temperature form

Note from the editor: Removed due to copyright reasons

Appendix 3 - Heat Load from Auto Compression

The primary cause of high temperatures in deep mines is auto compression. This is the increasing temperature due to change in potential energy. As air travels down the intake airways from the surface, its elevation decreases and there is a corresponding conversion of potential energy into enthalpy. The magnitude of the change in enthalpy can be estimated using the steady flow energy equation for a higher elevation (Z₂) to a lower one (Z₁), assuming no heat flow and no work done.

dH = H 2 - H 1 = g(Z2 - Z1 )/1000 kJ/kg

Where,

dH = change in enthalpy

H = enthalpy (J/kg)

Z = elevation (m)

g = acceleration due to gravity (9.81 m/s²)

The enthalpy thus increases by 0.981kJ/kg for every 100m decrease in elevation. This means that for every 100 metres of increase in depth, auto compression adds 0.981 kilojoules to each kilogram of air.The figure of 0.981kJ/kg of air per 100 metres is constant for every mine. For dry air, the thermal capacity is 1.005kJ/˚C therefore,

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The change in dry bulb temperature is much less if water evaporates in the shaft. At Mufulira mine the change in temperature due to auto compression are 0.5°C wet bulb and 0.9°C dry bulb temperatures per 100 metres of increase in depth.

The following equation is used in determining auto compression;

H = dt x C𝚙ₐ x Mₐ

Where,

H = heat due to auto compression (kJ/s)

dt = change in dry bulb temperature (°C)

Cpₐ = thermal capacity (kJ/kg)

Mₐ = mass flow rate of air (kg/s)

On 1440m level H = 0.9(100/100) x 1.005 x 578 = 523 kW

On 1540m level H = 0.9(200/100) x 1.005 x 693 = 1254 kW

On 1640m level H = 0.9(300/100) x 1.005 x 798 = 2165 kW

On 1740m level H = 0.9(400/100) x 1.005 x 1274 = 4609 kW

On 1840m level H = 0.9(500/100) x 1.005 x 1429 = 6463 kW

On 1940m level H = 0.9(600/100) x 1.005 x 1584 = 8596 kW

On 2020m level H = 0.9(700/100) x 1.005 x 1769 = 11200 kW

Therefore, total auto compression heat load = 34810kW

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Appendix 4 - Heat Load From Rock Strata.

Another major source of heat in mines is geothermal energy from the rock strata.

Virgin rock temperature (VRT)

Distance into borehole against temperature

1340m level Block 52/53 (Boundary) Angle: Horizontal

Borehole depth +120m Relative humidity 90%

Wet bulb temperature 30.5°C Dry bulb temperature 34°C

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VRT determination

The average VRT = 38.1°C

Distance in to bore hole against temperature

1440m level Block 56 Panel 5 Angle: +10ᵒ N/W

Wet bulb temperature 36oC Relative humidity 100%

Borehole depth +20m Dry bulb temperature 38°C

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VRT determination

The average VRT = 39.6°C

Where average temperature at 1340ml θ1 = 38.1°C and at 1423ml θ2 = 39.6 ° C,

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= 0.015 ᵒϹ/m

This translates to 1.5°C/100m

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VRTs and their corresponding levels

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Geothermal temperature gradient

Appendix 5 - Heat conducted through the rock strata.

The equation below was used to estimate the heat flow from the rock strata:

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Where,

Q = Heat pick up at development ends in kilowatts

DFA = Daily Face Advance (m/day)

VRT = Virgin Rock Temperature (°C)

WB = Wet Bulb Temperature (°C)

K = Thermal conductivity of the rock (w/m°C)

ρ = Density of the rock (2646.5 Kg/m³)

C = Specific heat of the rock (KJ/Kg°C)

The constant 13 x 106 is the value of the Kpc for quartzite.

The heat production curve was plotted using the above equation and has been used to evaluate heat generated from Stopes and development.

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Heat production curve for the deeps section

Assuming an average production of 167, 000 tonnes per month from development and stopes, using the heat production curve, the heat generated was calculated as follows:-

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Heat generated from rock strata at different levels

Total heat Load from rock strata = 104, 795 kW.

Appendix 6 - Conveyor belts and Auxiliary fans

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Where;

qconv = Conveyor heat load, (kW)

Eload = Electrical power at average belt load (kW)

Enil = Electrical power at belt load (kW)

toff = Time the conveyor is off, (hours)

tload = Time the conveyor runs loaded, (hours)

tnil = Time the conveyor runs nil loaded, (hours)

Mc =Mass moved in total time , Kg

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conveyor heat load

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Mass conveyed

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Conveyor availability

Total belt Eload =(2400+55)kw=2455kw

Total belt Enil =(660+18)kw=678kw

Maximum tload =14.5hr

Maximum tnil =2.05hr

Belt elevation =z2 +z1 =(1440-1340)m=100m

Maximum mass moved Mc = 2745000

Total time (tload + tnil + toff off) = 24hr

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Total heat load from electrical equipments = (1295 + 1510) = 2, 805kW

Auxiliary fans

In calculating the heat from electrical equipment it was assumed that all input power to auxiliary fan is finally convicted into waste heat except for those used to exhaust air from the mine, they do not affect the ventilating air underground.

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Fan characteristics

Note: A fresh air intake fan at 1420m level has a shaft power of 75kW.

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Overall total fan power developed.

Deeps total fan power developed = 1295kW

Appendix 7 - Heat Load from Humans

The amount of heat produced by the human body varies depending on the amount of work performed. According to the research carried by C. H. Wyndham in 1971, Human Sciences Laboratory, Chamber of Mines Research Organization, the following data in Table 3.5a was provided;

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Metabolic heat

Number of workers at Mufulira Deeps as at 9th September, 2013

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Table 3.5b Manpower at deeps section

Assuming work is between moderate and hard rate of work, then;

Therefore,

Total qhuman = 647×372.5w = 241kw

Appendix 8 - Total Mine Heat Load

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Table 3.6 Total mine heat load

Total mine heat load = 182, 900kW

Appendix 9 - Ventilation prediction

Total Heat discharge into the mine air stream from Auto compression, the rock, water, men, mechanical and electrical equipments has carefully been analysed based on planned production target of 167, 000 tonnes per month to be 36 855kW for the Deeps, 1340m to 2020m levels. Maintaining temperatures of the intake air at 28.0°C wet bulb for the Deeps section down to 2020m levels and a design return of 31.0°C wet bulb the volume requirement is;

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= 1, 600m³/s

Appendix 9 - Training requirements Relating to Vibration

a) Exposure limit values and action values
b) Control measures
c) Findings of risk assessment
d) Detecting signs and symptoms
e) Health surveillance requirements

Appendix 10 - Factors Concerning Silicosis

The effects of silica exposure are influenced by a number of factors:

- the proportion of silica in the material
- the mechanical work involving breaking up and/or processing the material
- work patterns influencing when and how individuals may become exposed.

Silica dust levels which exceed 10 mg/m3 over an 8-hour period and exposure to respirable dust which exceed 4 mg/m3 will significantly increase the chance of respiratory diseases. The most significant concern is that caused by respiratory dust which penetrates the lower respiratory tract, notably the lungs. The workplace exposure limit (WEL) for respiratory dust is 0.1 mg/m3 in Schedule 1 of the Control of Substances Hazardous to Health Regulations 2002 (COSHH). Should this concentration of airborne exceed this limit then the chances of silicosis increase in workers. Recent evidence suggests lung cancer is now also a risk. (HSE Guidance Silica)

Appendix 11 - Survey Results for Silica Dust

It is worth noting, that the silica levels are far less than that of other plants in the Copper Belt, due to less granite present in the ore. This therefore reduces the likelihood for silicosis.

The survey revealed that the mean crystalline silica dust content in bulk ore samples for Mufulira and Nkana were 57% and 20% respectively. The personal respirable dust results revealed that the average crystalline silica content from 67 samples in Mufulira and 52 at

Nkana out of the 100 samples collected at each mine exceeded the NIOSH recommended exposure limit of 0.05mg/m3 for crystalline silica. A follow-up personal dust sampling in the same areas which was conducted in 2008 revealed a 50% reduction in crystalline silica content at Nkana and an increase of 6% at Mufulira mine site compared to the 2006 results.

Appendix 12 - Heat stress Statistics at Deeps

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Appendix 13 – Guide maximum handling loads

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Appendix 14 - Questions raised during consultation:

1) What are the top 10 causes for occupational related admissions and outpatient support?
2) What are the occupational hazards, which caused visits to the hospital?
3) What are the existing secondary and tertiary management interventions for Mopani
4) What government legislation exists in relation to occupational hazards?
5) What medical research has taken place to identify and control health hazards?
6) What are the current barriers which must be overcome to improve the management of occupational health?
7) What occupational hazards have not been adequately risk assessed and what further hygiene tests need to be carried out?
8) What current qualifications has the physician obtained relating to occupational health?
9) What will be the costs to improve both organisational and engineered health and safety controls?
10) What are the costs and benefits for the acquisition of further primary occupational health interventions?
11) What measures have been used by your competitors to improve the management of similar sections?
12) What administrative controls (such as training, monitoring, safe systems of work) are set in place and how effective are they?
13) How comprehensive is the health and safety policy and what risk assessments have been carried out?
14) What is the employees’ perception of health and safety, and what influences their behaviour?
15) What SHE plans have been drafted and what were the objectives?

Appendix 15 – Refrigeration Plant

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Appendix 16 – Definition of concepts and Abbreviations

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77 of 77 pages

Details

Title
Management of Heat Underground. Case Study of Deeps Section at Mopani Copper Mines Mufulira Mine Site
Subtitle
Health and Safety
Course
International Diploma in Occupational Health and Safety
Author
Year
2014
Pages
77
Catalog Number
V416767
ISBN (Book)
9783668666405
File size
2220 KB
Language
English
Tags
Management, Heat, Underground, Cave, Deep, Mopani, Copper, Mines, Mufulira, Mine
Quote paper
Larry Malambo (Author), 2014, Management of Heat Underground. Case Study of Deeps Section at Mopani Copper Mines Mufulira Mine Site, Munich, GRIN Verlag, https://www.grin.com/document/416767

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Title: Management of Heat Underground. Case Study of Deeps Section at Mopani Copper Mines Mufulira Mine Site



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