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Monday, 04 April 2011 17:06

Hand and Portable Power Tool Safety

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Tools are such a common part of our lives that it is sometimes difficult to remember that they may pose hazards. All tools are manufactured with safety in mind, but occasionally an accident may occur before tool-related hazards are recognized. Workers must learn to recognize the hazards associated with the different types of tools and the safety precautions required to prevent those hazards. Appropriate personal protective equipment, such as safety goggles or gloves, should be worn for protection from potential hazards that may be encountered while using portable power tools and hand tools.

Hand Tools

Hand tools are non-powered and include everything from axes to wrenches. The greatest hazards posed by hand tools result from misuse, use of the wrong tool for the job, and improper maintenance. Some of the hazards associated with the use of hand tools include but are not limited to the following:

  • Using a screwdriver as a chisel may cause the tip of the screwdriver to break off and fly, hitting the user or other employees.
  • If a wooden handle on a tool such as a hammer or an axe is loose, splintered or cracked, the head of the tool may fly off and strike the user or another worker.
  • A wrench must not be used if its jaws are sprung, because it might slip.
  • Impact tools such as chisels, wedges or drift pins are unsafe if they have mushroomed heads which might shatter on impact, sending sharp fragments flying.

 

The employer is responsible for the safe condition of tools and equipment provided to employees, but the employees have the responsibility to use and maintain the tools properly. Workers should direct saw blades, knives or other tools away from aisle areas and other employees working in close proximity. Knives and scissors must be kept sharp, as dull tools can be more hazardous than sharp ones. (See figure 1.)

Figure 1. A screwdriver

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Safety requires that floors be kept as clean and dry as possible to prevent accidental slips when working with or around dangerous hand tools. Although sparks produced by iron and steel hand tools are not normally hot enough to be sources of ignition, when working with or around flammable materials, spark-resistant tools made from brass, plastic, aluminium or wood may be used to prevent spark formation.

Power Tools

Power tools are hazardous when improperly used. There are several types of power tools, usually categorized according to the power source (electric, pneumatic, liquid fuel, hydraulic, steam and explosive powder actuated). Employees should be qualified or trained in the use of all power tools used in their work. They should understand the potential hazards associated with the use of power tools, and observe the following general safety precautions to prevent those hazards from occurring:

  • Never carry a tool by the cord or hose.
  • Never yank the cord or the hose to disconnect it from the receptacle.
  • Keep cords and hoses away from heat, oil and sharp edges.
  • Disconnect tools when they are not in use, before servicing, and when changing accessories such as blades, bits and cutters.
  • All observers should stay a safe distance away from the work area.
  • Secure work with clamps or a vise, freeing both hands to operate the tool.
  • Avoid accidental starting. The worker should not hold a finger on the switch button while carrying a plugged-in tool. Tools which have lock-on controls should be disengaged when power is interrupted so that they do not start up automatically upon restoration of power.
  • Tools should be maintained with care and kept sharp and clean for best performance. Instructions in the user’s manual should be followed for lubrication and changing accessories.
  • Workers should assure they have good footing and balance when using power tools. Appropriate apparel should be worn, as loose clothing, ties or jewellery can become caught in moving parts.
  • All portable electric tools that are damaged shall be removed from use and tagged “Do Not Use” to prevent electrical shock.

 

Protective Guards

Hazardous moving parts of power tools need to be safeguarded. For example, belts, gears, shafts, pulleys, sprockets, spindles, drums, flywheels, chains or other reciprocating, rotating or moving parts of equipment must be guarded if such parts are exposed to contact by workers. Where necessary, guards should be provided to protect the operator and others with respect to hazards associated with:

  • the point of operation
  • in-running nip points
  • rotating and reciprocating parts
  • flying chips and sparks, and mist or spray from metal-working fluids.

 

Safety guards must never be removed when a tool is being used. For example, portable circular saws must be equipped with guards. An upper guard must cover the entire blade of the saw. A retractable lower guard must cover the teeth of the saw, except when it makes contact with the work material. The lower guard must automatically return to the covering position when the tool is withdrawn from the work. Note the blade guards in the illustration of a power saw (figure 2).

Figure 2. A circular saw with guard

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Safety Switches and Controls

The following are examples of hand-held power tools which must be equipped with a momentary contact “on-off” control switch:

  • drills, tappers and fastener drivers
  • horizontal, vertical and angle grinders with wheels larger than 2 inches (5.1 cm) in diameter
  • disc and belt sanders
  • reciprocating and sabre saws.

 

These tools also may be equipped with a lock-on control, provided that turnoff can be accomplished by a single motion of the same finger or fingers that turn it on.

The following hand-held power tools may be equipped with only a positive “on-off” control switch:

  • platen sanders
  • disc sanders with discs 2 inches (5.1 cm) or less in diameter
  • grinders with wheels 2 inches (5.1 cm) or less in diameter
  • routers and planers
  • laminate trimmers, nibblers and shears
  • scroll saws and jigsaws with blade shanks ¼ inch (0.64 cm) wide or less.

 

Other hand-held power tools which must be equipped with a constant pressure switch that will shut off the power when the pressure is released include:

  • circular saws having a blade diameter greater than 2 inches (5.1 cm)
  • chain-saws
  • percussion tools without positive accessory-holding means.

 

Electric Tools

Workers using electric tools must be aware of several dangers. The most serious of these is the possibility of electrocution, followed by burns and slight shocks. Under certain conditions, even a small amount of current can result in fibrillation of the heart which may result in death. A shock also may cause a worker to fall off a ladder or other elevated work surfaces.

To reduce the potential of injury to workers from shock, tools must be protected by at least one of the following means:

  • Grounded by a three-wire cord (with a ground wire). Three-wire cords contain two current-carrying conductors and a grounding conductor. One end of the grounding conductor connects to the tool’s metal housing. The other end is grounded through a prong on the plug. Any time an adapter is used to accommodate a two-hole receptacle, the adapter wire must be attached to a known ground. The third prong should never be removed from the plug. (See figure 3.)
  • Double insulated. The worker and the tools are protected in two ways: (1) by normal insulation on the wires inside, and (2) by a housing that cannot conduct electricity to the operator in the event of a malfunction.
  • Powered by a low-voltage isolation transformer.
  • Connected through ground fault circuit interrupters. These are permanent and portable devices which instantaneously disconnect a circuit when it seeks ground through a worker’s body or through grounded objects.

 

Figure 3. An electric drill

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These general safety practices should be followed in using electric tools:

  • Electric tools should be operated within their design limitations.
  • Gloves and safety footwear are recommended during use of electric tools.
  • When not in use, tools should be stored in a dry place.
  • Tools should not be used if wires or connectors are frayed, bent or damaged.
  • Electric tools should not be used in damp or wet locations.
  • Work areas should be well lighted.

 

Powered Abrasive Wheels

Powered abrasive grinding, cutting, polishing and wire buffing wheels create special safety problems because the wheels may disintegrate and throw off flying fragments.

Before abrasive wheels are mounted, they should be inspected closely and sound (or ring) tested by tapping gently with a light non-metallic instrument to be sure that they are free from cracks or defects. If wheels are cracked or sound dead, they could fly apart in operation and must not be used. A sound and undamaged wheel will give a clear metallic tone or “ring”.

To prevent the wheel from cracking, the user should be sure it fits freely on the spindle. The spindle nut must be tightened enough to hold the wheel in place without distorting the flange. Follow the manufacturer’s recommendations. Care must be taken to assure that the spindle wheel will not exceed the abrasive wheel specifications. Due to the possibility of a wheel disintegrating (exploding) during start-up, the worker should never stand directly in front of the wheel as it accelerates to full operating speed. Portable grinding tools need to be equipped with safety guards to protect workers not only from the moving wheel surface, but also from flying fragments in case of breakage. In addition, when using a powered grinder, these precautions should be observed:

  • Always use eye protection.
  • Turn off the power when tool is not in use.
  • Never clamp a hand-held grinder in a vise.

 

Pneumatic Tools

Pneumatic tools are powered by compressed air and include chippers, drills, hammers and sanders. Although there are several potential dangers encountered in the use of pneumatic tools, the main one is the danger of getting hit by one of the tool’s attachments or by some kind of fastener the worker is using with the tool. Eye protection is required and face protection is recommended when working with pneumatic tools. Noise is another hazard. Working with noisy tools such as jackhammers requires proper, effective use of appropriate hearing protection.

When using a pneumatic tool, the worker must check to assure that it is fastened securely to the hose to prevent a disconnection. A short wire or positive locking device attaching the air hose to the tool will serve as an added safeguard. If an air hose is more than½ inch (1.27 cm) in diameter, a safety excess flow valve should be installed at the source of the air supply to shut off the air automatically in case the hose breaks. In general, the same precautions should be taken with an air hose that are recommended for electric cords, because the hose is subject to the same kind of damage or accidental striking, and it also presents a tripping hazard.

Compressed-air guns should never be pointed toward anyone. Workers should never “dead-end” the nozzle against themselves or anyone else. A safety clip or retainer should be installed to prevent attachments, such as a chisel on a chipping hammer, from being unintentionally shot from the barrel. Screens should be set up to protect nearby workers from being struck by flying fragments around chippers, riveting guns, air hammers, staplers or air drills.

Airless spray guns that atomize paints and fluids at high pressures (1,000 pounds or more per square inch) must be equipped with automatic or manual visual safety devices that will prevent activation until the safety device is manually released. Heavy jackhammers can cause fatigue and strains which may be reduced by the use of heavy rubber grips that provide a secure handhold. A worker operating a jackhammer must wear safety glasses and safety shoes to protect against injury if the hammer slips or falls. A face shield also should be used.

Fuel-Powered Tools

Fuel-powered tools are usually operated using small gasoline-powered internal combustion motors. The most serious potential dangers associated with the use of fuel-powered tools comes from hazardous fuel vapours that can burn or explode and give off dangerous exhaust fumes. The worker must be careful to handle, transport and store the gasoline or fuel only in approved flammable liquid containers, according to proper procedures for flammable liquids. Before the tank for a fuel-powered tool is refilled, the user must shut down the engine and allow it to cool to prevent accidental ignition of hazardous vapours. If a fuel-powered tool is used inside a closed area, effective ventilation and/or protective equipment is necessary to prevent exposure to carbon monoxide. Fire extinguishers must be available in the area.

Explosive Powder-Actuated Tools

Explosive powder-actuated tools operate like a loaded gun and should be treated with the same respect and precautions. In fact, they are so dangerous that they must be operated only by specially trained or qualified employees. Suitable ear, eye and face protection are essential when using a powder-actuated tool. All powder-actuated tools should be designed for varying powder charges so that the user can select a powder level necessary to do the work without excessive force.

The muzzle end of the tool should have a protective shield or guard centred perpendicularly on the barrel to protect the user from any flying fragments or particles that might create a hazard when the tool is fired. The tool must be designed so that it will not fire unless it has this kind of safety device. To prevent the tool from firing accidentally, two separate motions are required for firing: one to bring the tool into position, and another to pull the trigger. The tools must not be able to operate until they are pressed against the work surface with a force at least 5 pounds greater than the total weight of the tool.

If a powder-actuated tool misfires, the user should wait at least 30 seconds before trying to fire it again. If it still will not fire, the user should wait at least another 30 seconds so that the faulty cartridge is less likely to explode, then carefully remove the load. The bad cartridge should be put in water or otherwise safely disposed of in accordance with employer’s procedures.

If a powder-actuated tool develops a defect during use, it should be tagged and taken out of service immediately until it is properly repaired. Precautions for the safe use and handling of powder-actuated tools include the following:

  • Powder-actuated tools should not be used in explosive or flammable atmospheres except upon issuance of a hot-work permit by an authorized person.
  • Before using the tool, the worker should inspect it to determine that it is clean, that all moving parts operate freely and that the barrel is free from obstructions.
  • The tool should never be pointed at anybody.
  • The tool should not be loaded unless it is to be used immediately. A loaded tool should not be left unattended, especially where it may be available to unauthorized persons.
  • Hands should be kept clear of the barrel end.

 

In using powder-actuated tools to apply fasteners, the following safety precautions should be considered:

  • Do not fire fasteners into material that would let them pass through to the other side.
  • Do not drive fasteners into materials like brick or concrete any closer than 3 inches (7.6 cm) to an edge or corner, or into steel any closer than ½ inch (1.27 cm) to a corner or edge.
  • Do not drive fasteners into very hard or brittle material that might chip, shatter or make the fasteners ricochet.
  • Use an alignment guide when shooting fasteners into existing holes. Do not drive fasteners into a spalled area caused by an unsatisfactory fastening.

 

Hydraulic Power Tools

The fluid used in hydraulic power tools must be approved for the expected use and must retain its operating characteristics at the most extreme temperatures to which it will be exposed. The manufacturer’s recommended safe operating pressure for hoses, valves, pipes, filters and other fittings must not be exceeded. Where there is a potential for a leak under high pressure in an area where sources of ignition, such as open flames or hot surfaces, may be present, the use of fire-resistant fluids as the hydraulic medium should be considered.

Jacks

All jacks—lever and ratchet jacks, screw jacks and hydraulic jacks—must have a device that stops them from jacking up too high. The manufacturer’s load limit must be permanently marked in a prominent place on the jack and should not be exceeded. Use wooden blocking under the base if necessary to make the jack level and secure. If the lift surface is metal, place a 1-inch-thick (2.54 cm) hardwood block or equivalent between the underside of the surface and the metal jack head to reduce the danger of slippage. A jack should never be used to support a lifted load. Once the load has been lifted, it should immediately be supported by blocks.

To set up a jack, make certain of the following conditions:

  1. The base rests on a firm level surface.
  2. The jack is correctly centred.
  3. The jack head bears against a level surface.
  4. The lift force is applied evenly.

 

Proper maintenance of jacks is essential for safety. All jacks must be inspected before each use and lubricated regularly. If a jack is subjected to an abnormal load or shock, it should be thoroughly examined to make sure it has not been damaged. Hydraulic jacks exposed to freezing temperatures must be filled with an adequate antifreeze liquid.

Summary

Workers who use hand and power tools and who are exposed to the hazards of falling, flying, abrasive and splashing objects and materials, or to hazards of harmful dusts, fumes, mists, vapours or gases, must be provided with the appropriate personal equipment necessary to protect them from the hazard. All hazards involved in the use of power tools can be prevented by workers following five basic safety rules:

  1. Keep all tools in good condition with regular maintenance.
  2. Use the right tool for the job.
  3. Examine each tool for damage before use.
  4. Operate tools according to the manufacturer’s instructions.
  5. Select and use appropriate protective equipment.

 

Employees and employers have a responsibility to work together to maintain established safe work practices. If a an unsafe tool or hazardous situation is encountered, it should be brought to the attention of the proper individual immediately.

 

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Read 16484 times Last modified on Saturday, 20 August 2011 01:34

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