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Sunday, 13 March 2011 16:33

Personal Protective Equipment in Mining

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Head Protection

In most countries miners must be provided with, and must wear, safety caps or hats which are approved in the jurisdiction in which the mine operates. Hats differ from caps in that they have a full brim rather than just a front peak. This has the advantage of shedding water in mines which are very wet. It does, however, preclude the incorporation of side slots for mounting of hearing protection, flashlights and face shields for welding, cutting, grinding, chipping and scaling or other accessories. Hats represent a very small percentage of the head protection worn in mines.

The cap or hat would in most cases be equipped with a lamp bracket and cord holder to permit mounting of a miner’s cap lamp.

The traditional miner’s cap has a very low profile which significantly reduces the propensity for the miner to bump his or her head in low seam coal mines. However, in mines where head room is adequate the low profile serves no useful purpose. Furthermore, it is achieved by reducing the clearance between the crown of the cap and the wearer’s skull so that these types of cap rarely meet the top impact standards for industrial head protection. In jurisdictions where the standards are enforced, the traditional miner’s cap is giving way to conventional industrial head protection.

Standards for industrial head protection have changed very little since the 1960s. However, in the 1990s, the boom in recreational head protection, such as hockey helmets, cycle helmets and so on, has highlighted what are perceived to be inadequacies in industrial head protection, most notably lack of lateral impact protection and lack of retention capabilities in the event of an impact. Thus, there has been pressure to upgrade the standards for industrial head protection and in some jurisdictions this has already happened. Safety caps with foam liners and, possibly, ratchet suspensions and/or chin straps are now appearing in the industrial marketplace. They have not been widely accepted by users because of the higher cost and weight and their lesser comfort. However, as the new standards become more widely entrenched in labour legislation the new style of cap is likely to appear in the mining industry.

Cap Lamps

In areas of the mine where permanent lighting is not installed, the miner’s cap lamp is essential to permit the miner to move and work effectively and safely. The key requirements for a cap lamp are that it be rugged, easy to operate with gloved hands, provide sufficient light output for the full duration of a work shift (to illumination levels required by local regulation) and that it be as light as possible without sacrificing any of the above performance parameters.

Halogen bulbs have largely replaced the incandescent tungsten filament bulb in recent years. This has resulted in three- or fourfold improvement in illumination levels, making it feasible to meet the minimum standards of illumination required by legislation even at the end of an extended work-shift. Battery technology also plays a major part in lamp performance. The lead acid battery still predominates in most mining applications, although some manufacturers have successfully introduced nickel-cadmium (nicad) batteries, which can achieve the same performance with a lower weight. Reliability, longevity and maintenance issues, however, still favour the lead acid battery and probably account for its continued dominance.

In addition to its primary function of providing lighting, the cap lamp and battery have recently been integrated into mine safety communications systems. Radio receivers and circuitry embedded in the battery cover permit the miners to receive messages, warnings or evacuation instructions through very low frequency (VLF) radio transmission and enable them to be made aware of an incoming message by means of an on/off flashing of the cap lamp.

Such systems are still in their infancy but they do have the potential to provide an advance in early warning capability over traditional stench gas systems in those mines where a VLF radio communication system can be engineered and installed.

Eye and Face Protection

Most mining operations around the world have compulsory eye protection programmes which require the miner to wear safety spectacles, goggles, faceshields or a full facepiece respirator, depending on the operations being performed and the combination of hazards to which the miner is exposed. For the majority of mining operations, safety spectacles with side shields provide suitable protection. The dust and dirt in many mining environments, most notably hard-rock mining, can be highly abrasive. This causes scratching and rapid wear of safety glasses with plastic (polycarbonate) lenses. For this reason, many mines still permit the use of glass lenses, even though they do not provide the resistance to impact and shattering offered by polycarbonates, and even though they may not meet the prevailing standard for protective eye wear in the particular jurisdiction. Progress continues to be made in both anti-fog treatments and surface hardening treatments for plastic lenses. Those treatments which change the molecular structure of the lens surface rather than simply applying a film or coating are typically more effective and longer lasting and have the potential to replace glass as the lens material of choice for abrasive mining environments.

Goggles are not worn frequently below ground unless the particular operation poses a danger of chemical splash.

A faceshield may be worn where the miner requires full-face protection from weld spatter, grinding residues or other large flying particles which could be produced by cutting, chipping or scaling. The faceshield may be of a specialized nature, as in welding, or may be clear acrylic or polycarbonate. Although faceshields can be equipped with their own head harness, in mining they will normally be mounted in the accessory slots in the miner’s safety cap. Faceshields are designed so that they can be quickly and easily hinged upwards for observation of the work and down over the face for protection when performing the work.

A full facepiece respirator may be worn for face protection when there is also a requirement for respiratory protection against a substance which is irritating to the eyes. Such operations are more often encountered in the above ground mine processing than in the below ground mining operation itself.

Respiratory Protection

The most commonly needed respiratory protection in mining operations is dust protection. Coal dust as well as most other ambient dusts can be effectively filtered using an inexpensive quarter facepiece dust mask. The type which uses an elastomer nose/mouth cover and replaceable filters is effective. The moulded throw-away fibre-cup type respirator is not effective.

Welding, flame cutting, use of solvents, handling of fuels, blasting and other operations can produce air-borne contaminants that require the use of twin cartridge respirators to remove combinations of dust, mists, fumes, organic vapours and acid gases. In these cases, the need for protection for the miner will be indicated by measurement of the contaminants, usually performed locally, using detector tubes or portable instruments. The appropriate respirator is worn until the mine ventilation system has cleared the contaminant or reduced it to levels that are acceptable.

Certain types of particulates encountered in mines, such as asbestos fibres found in asbestos mines, coal fines produced in longwall mining and radionuclides found in uranium mining, may require the use of a positive pressure respirator equipped with a high-efficiency particulate absolute (HEPA) filter. Powered air-purifying respirators (PAPRs) which supply the filtered air to a hood, tight-fitting facepiece or integrated helmet facepiece assembly meet this requirement.

Hearing Protection

Underground vehicles, machinery and power tools generate high ambient noise levels which can create long-term damage to human hearing. Protection is normally provided by ear muff type protectors which are slot-mounted on the miner’s cap. Supplementary protection can be provided by wearing closed cell foam ear plugs in conjunction with the ear muffs. Ear plugs, either of the disposable foam cell variety or the reusable elastomeric variety, may be used on their own, either because of preference or because the accessory slot is being used to carry a face shield or other accessory.

Skin Protection

Certain mining operations may cause skin irritation. Work gloves are worn whenever possible in such operations and barrier creams are provided for additional protection, particularly when the gloves cannot be worn.

Foot Protection

The mining work boot may be of either leather or rubber construction, depending on whether the mine is dry or wet. Minimum protective requirements for the boot include a full puncture-proof sole with a composite outer layer to prevent slipping, a steel toe-cap and a metatarsal guard. Although these fundamental requirements have not changed in many years, advances have been made towards meeting them in a boot that is far less cumbersome and far more comfortable than the boots of several years ago. For example, metatarsal guards are now available in moulded fibre, replacing the steel hoops and saddles that were once common. They provide equivalent protection with less weight and less risk of tripping. The lasts (foot forms) have become more anatomically correct and energy absorbing mid-soles, full moisture barriers and modern insulating materials have made their way from the sports/recreation footwear market into the mining boot.

Clothing

Ordinary cotton coveralls or treated flame-resistant cotton coveralls are the normal workwear in mines. Strips of reflective material are usually added to make the miner more visible to drivers of moving underground vehicles. Miners working with jumbo drills or other heavy equipment may also wear rain suits over their coveralls to protect against cutting fluid, hydraulic oil and lubricating oils, which can spray or leak from the equipment.

Work gloves are worn for hand protection. A general purpose work glove would be constructed of cotton canvas reinforced with leather. Other types and styles of glove would be used for special job functions.

Belts and Harnesses

In most jurisdictions, the miners belt is no longer considered suitable or approved for fall protection. A webbing or leather belt is still used, however, with or without suspenders and with or without a lumbar support to carry the lamp battery as well as a filter self-rescuer or self-contained (oxygen generating) self-rescuer, if required.

A full body harness with D-ring attachment between the shoulder blades is now the only recommended device for protecting miners against falls. The harness should be worn with a suitable lanyard and shock absorbing device by miners working in shafts, over crushers or near open sump or pits. Additional D-rings may be added to a harness or a miner’s belt for work positioning or to restrict movement within safe limits.

Protection from Heat and Cold

In open-pit mines in cold climates, miners will have winter clothing including thermal socks, underwear and gloves, wind resistant pants or over-pants, a lined parka with hood and a winter liner to wear with the safety cap.

In underground mines, heat is more of a problem than cold. Ambient temperatures may be high because of the depth of the mine below ground or because it is located in a hot climate. Protection from heat stress and potential heat stroke can be provided by special garments or undergarments which can accommodate frozen gel packs or which are constructed with a network of cooling tubes to circulate cooling fluids over the surface of the body and then through an external heat exchanger. In situations where the rock itself is hot, heat resistant gloves, socks and boots are worn. Drinking water or, preferably, drinking water with added electrolytes must be available and must be consumed to replace lost body fluids.

Other Protective Equipment

Depending on local regulations and the type of mine, miners may be required to carry a self-rescue device. This is a respiratory protection device which will help the miner to escape from the mine in the event of a mine fire or explosion that renders the atmosphere unbreathable because of carbon monoxide, smoke and other toxic contaminants. The self-rescuer may be a filtration type device with a catalyst for carbon monoxide conversion or it may be a self-contained self-rescuer, i.e., a closed-cycle breathing apparatus which chemically regenerates oxygen from exhaled breath.

Portable instruments (including detector tubes and detector tube pumps) for the detection and measurement of toxic and combustible gases are not carried routinely by all miners, but are used by mine safety officers or other designated personnel in accordance with standard operating procedures to test mine atmospheres periodically or before entry.

Improving the ability to communicate with personnel in underground mining operations is proving to have enormous safety benefits and two-way communication systems, personal pagers and personnel locating devices are finding their way into modern mining operations.

 

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Read 18212 times Last modified on Tuesday, 28 June 2011 12:21

Contents

Preface
Part I. The Body
Part II. Health Care
Part III. Management & Policy
Part IV. Tools and Approaches
Part V. Psychosocial and Organizational Factors
Part VI. General Hazards
Part VII. The Environment
Part VIII. Accidents and Safety Management
Part IX. Chemicals
Part X. Industries Based on Biological Resources
Part XI. Industries Based on Natural Resources
Part XII. Chemical Industries
Part XIII. Manufacturing Industries
Part XIV. Textile and Apparel Industries
Part XV. Transport Industries
Part XVI. Construction
Part XVII. Services and Trade
Part XVIII. Guides