Lesson 1, Topic 1
In Progress

1.7. Safeguarding Machinery & Equipment

ryanrori July 14, 2020

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1.7. Safeguarding Machinery and Equipment

A machine guard is a barrier which suitably encloses the moving parts of a machine. It must prevent any part of the body from reaching under, over, around or through the guard and entering the danger zone.

It is necessary to safeguard machines because the injuries caused by machines could be severe, disabling and permanent; such injuries are generally preventable; danger can often be reduced or removed by mechanical safeguards; and workers realise that unguarded machinery is dangerous. The employer should spend money on the safeguarding of machinery to show his sincerity in protecting the workers from injury.

Classes and types of machine guards

There are two classes of machine guards, namely, transmission guards and point of operation guards.

There are three types of guards, namely:

  • Fixed Guards these do not move with each operation;
  • Interlocking Guards these guards prevent the controls of the machine from being used until the guard is moved into place; and
  • Automatic Guards these prevent the machine operator from coming into contact with the dangerous parts of a machine while it is moving.

Requirements of machine guards

Machine guards should comply with the following requirements:

  • They should afford the maximum protection possible;
  • The danger zone(s) should be blocked out during operation;
  • The guards should be corrosion-free and fire-resistant;
  • The guards should not produce splinters or pinch the operators;
  • The guards should be fixtures of the machinery;
  • The guards should not affect the efficiency of the machine; and
  • They should be strong enough to withstand normal wear and tear.

Various machine mechanisms

Machines that should be guarded may have one or more of the following mechanisms:

  • Rotating mechanisms
  • In-running nip points
  • Forming or bending mechanisms
  • Cutting or shearing mechanisms
  • Screw or worm mechanisms

A piece of equipment may use more than one basic mechanism and therefore present more than one type of hazardous exposure. A belt and pulley, for example, has a hazardous rotating mechanism and as well as hazardous in-running nip points.

Circular saws, for instance, present the following hazards:

  • The natural characteristics of the wood which could make it dangerous’, e.g., knots;
  • contact between a part of the worker’s body and the saw teeth;
  • kickback of the stock (this is a particular characteristic of a circular ripping saw);
  • contact between a part of the worker’s body and the saw transmission;
  • hands being drawn into the automatic feed device;
  • inadequacy of the machine guards, e.g. , if the guard is incorrectly adjusted;
  • bad working practices, e.g. , loose clothing getting entwined in the mechanisms;
  • noise; and
  • The stock being sawn.

Suggested materials for machine guards

The preferred material for guards, under most circumstances, is metal. The framework of guards is usually made from structural shapes such as pipe, strapping and bar or rod stock. Filler material generally is expanded metal, perforated metal, solid steel metal or heavy wire mesh. Where visibility is required, guards of formed transparent plastic or of safety glass are widely used. An important factor in the design of a guard is to provide complete protection; the openings must be large enough to admit stock, but small enough to prevent a person or object from getting into the danger zone.

Machine guards for electrical equipment

In addition to safeguarding machinery by mechanical means, the machines which operate by electrical means must be connected correctly, i.e., all machinery which exceeds 42 volts should be connected to an earth-leakage system to prevent electric shock.

An earth-leakage system is so designed that, any leakage to earth on the tool being used will immediately be detected and the flow of current switched off automatically. In some cases, electrical machinery is double insulated to protect the user from electrical shock.

The person installing the machinery must make sure that the machinery has three-core wiring, unless of course it is double insulated.

 

In other words, the machinery that is not double insulated must have an earth wire which is usually GREEN/YELLOW in colour.
Usually the BLUE wire is the neutral wire and the BROWN wire is the live or line wire.
The wiring of electrical tools and machinery must be connected correctly.

 

Portable electrical tools/machinery must be checked regularly for: loose connections; cracked or broken insulations; earth continuity; switches in bad order; and joins in flexible cords. To protect maintenance workers from injury or electric shock from electrical tools and equipment, it may be necessary to place warning notices over machinery to indicate what dangers are latent in the machinery. It may also be necessary to lock the switches to the equipment by padlocks, and only to switch on the equipment where and if necessary. Main switches should be prominently marked.

Moving machinery

  • Maintenance and adjustments should never be carried out on machinery that is running or moving.
  • Machinery must be stopped and “locked out” before any repair or maintenance work is carried out. “Locked Out” means that any electricity, steam, air pressure or anything else that drives the machine is disconnected or isolated so that the machine being worked upon, cannot be accidentally started and so injure the person carrying out the work.

Maintenance of mechanical equipment

  • Mechanical equipment must be maintained and kept in good order to ensure efficient and smooth operation. Poorly maintained machinery will produce poor quality, place greater strain on the machine, the material and the operator and lead to early failure.
  • Cutting edges must be kept sharp.
  • Moving parts must be well lubricated.
  • Air filters must be kept clean.
  • Loose parts must be fixed properly with bolts and nuts and not tied with wire.

Inspections or repairs on machinery

  • NO One is allowed to repair, adjust, clean or oil moving machinery unless such is done by a competent person, and only when it is impractical to stop such machinery.
  • Automatic oiling devices should be installed as far as possible/practicable.
  • The operator of any machinery must be trained to inspect the machinery that he intends using daily before use.
  • Inspections must include:
  • The checking of oil and water levels
  • Air filters
  • Drive belt tension
  • Sharpness of blades, chisels
  • Controls

Company Vehicles

Company vehicles should be checked regularly for

  • Faulty brakes;
  • Faulty headlights;
  • Damaged connecting cables;
  • General lighting;
  • Worn tyres;
  • Faulty windscreen wipers
  • Defective steering wheels;
  • Broken windows;
  • Broken hooters;
  • Rear-view mirrors;
  • Engine idling system;
  • Instruments;
  • Exhaust;
  • Fire extinguishers,
  • Cooling system;
  • And emergency equipment such as fire spare bulbs and emergency triangles.

Fire hazards

Fire hazards exist in processes or operations that use flame producing equipment such as welding and cutting equipment, gas torches and blow lamps.

A few precautions are necessary before and after using this equipment:

  • Before beginning work, check that there are no combustible (materials that burn easily) materials in the work area.
  • Clear away any rubbish or litter and make sure timbers (wood) lying nearby and anything else which cannot be removed that might catch fire is protected from heat and flame. This can be done by shielding it with non-flammable material.
  • Keep a suitable fire extinguisher at hand at all times.
  • Remember that metal work (such as pipes and conduits) can conduct heat to consumable materials such as floor and ceiling joists.
  • It is very important to make a further check when the job is done to ensure that nothing has been left smouldering.
  • Blow lamps and oxy-acetylene torches must not be left burning when they are not in use. Finally, make sure that fire extinguishers are near in case of fire.
  • Acetylene cylinders must never be used or stored at an angle of less than 45° as liquid acetone may run out and damage valves and hoses. Oxy-acetylene cylinders must be returned and stored upright in a flammable material store when not in use.
  • Cylinder valves must be fully closed and torches and hoses not left under pressure but the gas pressure must be released after the cylinder valve has been closed.

 

Fire Prevention

Smoking and open fires are not permitted in any storeroom or area, which contains flammable liquids, or any no smoking areas indicated by a non-smoking sign.

Misuse or tampering with fire prevention equipment can result in severe disciplinary action being taken.

Office and other electrical equipment must be switched off after normal working hours, over weekends

 

Liquid petroleum gas

Liquid petroleum gas (LPG) is widely used in the Construction Industry as a fuel for burners, heaters and gas torches. The liquid which comes in cylinders and containers is highly flammable and needs careful handling and storage.

When not in use, the cylinders must be stored with other flammable gases in a special storage area. Usually a stock of cylinders will be grouped together, with empty cylinders separated from those containing gas and mark clearly as “empty” or “full”.

DO NOT SMOKE IN THIS AREA.

Whether in use or stored, cylinders must be kept upright, i.e. with the valve uppermost. When the cylinder is not in use the valve should be closed (check that it is, before storing) and the protective cap should be in place.

In handling cylinders do not drop them or allow them to come into violent contact with other cylinders.

When using a cylinder with an appliance attached, ensure that it is connected properly in accordance with the instructions you have been given, (if you have not been so instructed ask a competent person) and that it is at a safe distance from the appliance or equipment it is feeding.

It is essential to make sure the gas does not leak. LPG is heavier than air and if it leaks, it will not disperse in the air but sink to the lowest point and form an explosive concentration, which could be ignited by a spark.

Leakages are especially dangerous in basements, trenches, storm water drains and excavations because the gas cannot flow out if it is below ground level.

Flammable liquid store

There may be thinners, adhesives, solvents and paint strippers in the store.

The danger of releasing flammable vapours, with the consequent risk of fire, is greatly increased. Keep this in mind if you visit the store to get a supply of one or other of these substances.

Do not store any other materials such as paper, cardboard, wood, cotton waste etc. together with flammable liquids.

Safety check list for the flammable liquid store

The following rules should be observed:

  • Check the labels on the containers and make sure you use the correct substance for the job you have to do.
  • If you have to decant (pour) the liquid into another container, do it outside the store.
  • Make sure caps and stoppers are replaced on the containers used.
  • Return containers to their proper place in the store, do not mix them with other containers.
  • Never return flammable items to the store in unmarked containers, nobody else will know what is in them, and you yourself may forget.
  • If you intend to use a substance in your work, read all manufacturers directions, instructions and warnings on the container first.
  • In the event of a fire raise the alarm immediately.
  • Keep a suitable fire extinguisher at hand at all times whilst using flammable liquids or adhesives.
  • Do not smoke or strike a match whilst using flammable liquids or adhesives.

 

Asbestos

You may come across asbestos in various forms during the course of your work in the building industry and these-are:

Insulating materials used as lagging on pipes:

  • Low density (soft) asbestos-cement insulation boards used for sound and temperature control.
  • High density (soft) asbestos-cement roof sheets, ceiling boards, facias, panels and rainwater goods used on factories, warehouses, schools and-residential buildings.

It is important to learn how to use and handle all types of asbestos containing materials (ACM’s) safely. The main reason is to prevent the release fine dust from the product.

Breathing of asbestos fibres over a period of time can have a serious effect on your health. Very small fibres (too small for the human eye) can find their way deep into the lungs, where after 10 to 40 years, they can cause the following diseases:

  • Asbestosis, scarring of the lung tissue, that leaves one breathless, and can lead to lung cancer, or in rare cases:
  • Mesothelioma, a cancer or the lining or the stomach or lungs.

Loose asbestos insulation often found on older buildings, and low density insulation boards can release asbestos fibers fairly easily. High density asbestos-cement will not normally release fibres unless the material is cut, drilled or sanded.

All ACM’s that require further processing, must be labelled with an “A” that will indicate the presence of asbestos. If you are not sure when you are working with asbestos materials, treat the task as if it contains asbestos.

Special low-speed power tools, some with vacuum extraction and filtration are available from the fibre cement industry. These ensure that the dust levels are kept below the legal exposure limit.

Hand tools may be used, as they create small chips, which cannot be inhaled.

Standard precautions must be-taken when working with asbestos material using high power tools, and these precautions include the following:

  • All surfaces being worked on must be kept moist.
  • Always work outdoors, to allow the dust to dilute in the air.
  • Work away from other and not near any form of intake vents of fans and/or air conditioning units.
  • If possible, collect all excess dust with an industrial vacuum cleaner, or allow the dust to fall onto moist sawdust, that can be easily cleaned when required.
  • Do not use a broom to sweep dry asbestos dust.
  • Always wear a suitable respirator when cutting, drilling or sanding asbestos materials.
  • Avoid using angle and disc grinders, as these generate excessive high dust levels.

Preventing manual handling accidents

  • All lifting and carrying operations should be supervised.
  • Personnel should be taught the correct techniques.
  • Determine how many people would be required to move a load safely BEFORE attempting to move it.
  • Provide adequate space for the task to be done and point the load in the direction it has to be moved.
  • Employees should wear personal protective equipment like gloves, boots and aprons.
  • Where more than one person is required, teamwork is essential.
  • The supervisor MUST give clear instructions and signals.

Lifting techniques

When lifting and transporting ‘a heavy object, such as a box of tiles, or heavy equipment, you should protect yourself from injuries.

Preparing to lift

Before lifting any load ask yourself the following questions:

  • What has to be moved?
  • From where and to where must it be moved?
  • Will assistance be required?

A load which at first seams light enough will become progressively heavier the further you have to carry it. Apart from the risk of strain, it is generally inefficient to carry a load over a long distance. Before lifting and carrying make sure the route is clear of obstacles and the place where the load is to be deposited is not obstructed.

Kinetic method of lifting

The kinetic method of lifting enables you to make full use of your own body weight to initiate the lift. The natural shape of the spine should” remain throughout (although the body may be bent forward the spine should remain straight) and the lift is powered by the strong muscles in the legs and thighs.

“It is important to begin with the right posture; that is, the various parts of the body should be correctly positioned before beginning the lift.

The following points should be noted:

  • Feet are placed about-5OOmm apart, with one foot slightly forward, in the direction of movement. This gives a ‘good balance and ‘provides a secure basis for the lift.
  • Stand CLOSE to the object to be picked up.
  • Knees should be slightly bent (but not fully bent as in a squat).
  • Back must be straight, although the body may be inclined forward.
  • Arms should be as close to the body as possible. The further the arms are extended the greater the strain.
  • Elbows should be kept in.
  • Grip must be firm and secure.
  • Head should be erect with the chin at right angle.
  • Get a GOOD GRIP on the box/article or equipment to be picked up.
  • Use the thigh, leg and abdominal muscles to lift, and keep the back straight.

                                                                                                          

The load

The mass a person can lift vary according to age, physique and condition, it will also depend on whether one is used to lifting and handling heavy loads.

A compact load of 30kg can be carried safely by the average male worker, providing proper methods re used In general, if there is a feeling of strain when raising a load you should get help.

Mass is not the only factor which makes it difficult to lift and carry. The size and shape can object awkward to handle. The absence of handholds or natural handling points can make it difficult to raise and carry the object. In all such instances assistance from other people or the use of handling aids such as wheel barrows, trolleys or hoists will be required.

 

Handling Ladders

There are a number of rules which have to be adhered to whilst handling/ using a ladder:

  • Avoid bringing a metal ladder near electricity (electrical overhead wires).
  • Place the ladder so that its feet are a quarter of its own length from the object it is resting against.
  • Let someone hold the ladder if it is not tied at the top.
  • Let the ladder extend for a considerable distance above its support’ in case it slips down.
  • Inspect ladders regularly to repair or replace defective rungs and other parts.
  • Rather varnish than paint a ladder because defects may be concealed by paint.
  • Keep ladders clean to expose defects.
  • Do not expose ladders to inclement weather.
  • Do not use ladders as scaffolding.
  • Haul tools and equipment up by rope instead of hanging them onto the sides or rungs of the ladder.
  • Do not leave a ladder where it may fall and be damaged.
  • Do not place ladders in front of doors which are regularly used as thoroughfares. The door could suddenly be opened and you could be flung to the ground.
  • Equip the ladder with safety feet or non-skid devices.
  • Use both hands when climbing a ladder.
  • Only one person at a time should climb a ladder.

 

Electrical safety measures

Burns from electrical apparatus

Besides electric shock, electricity can also cause external burning, e.g. the arc of a welding machine produces temperatures between 6 0000 to 8 0000 centigrade. Persons standing nearby such an arc will be severely burnt and such an arc may start a fire by igniting flammable material.

When the arc resulting from a breakdown of the insulating material or insulating medium is contained in an enclosure, the heat produced causes the surrounding air or oil to expand rapidly and may also cause an explosion by the expansion of air or oil. Such an explosion can produce extensive damage to property and to persons.

Faulty electrical circuits

Overloading of electrical circuits can produce localised heating of the conductors. The heat so generated may be sufficient to ignite nearby flammable material and thus cause a fire, or alternatively, the heating of the conductors may result in a deterioration of the insulating material and cause a fire.

To ensure a safe and uninterrupted supply of electricity, an industrialist must ensure that the electrical installations

  • Are correctly designed;
  • Proper and suitable equipment must be used;
  • Electrical installations
  • And equipment must be maintained in accordance with planned maintenance programmes.

A well-thought out planned maintenance programme of the electrical installation will ensure that regular cleaning, inspections, adjustment, testing and planned part replacement, are carried out.  Experience has shown that this significantly reduces breakdowns, including dangerous breakdowns or dangerous conditions.

Personnel should only be permitted to work on electrical systems if the circuits have been isolated, in other words switched off or if a lock-out system has been secured. Electrocutions are frequently caused when personnel work on electrical equipment which they either believe or assume have been isolated.

There should also be electrical protective devices such as overload and fault protection mechanisms, such as

  • Double insulated portable electric tools;
  • Double wound transformers;
  • And earth-leakage systems, as described above.

However, sometimes fault protection devices do not work  this could lead to fires in storerooms and warehouses. The recommended protection of the electrical installation in storerooms or other areas where flammable materials are stored or used is to provide earth-leakage devices on all circuits, which will either isolate the circuits or sound an alarm if a pre-set leakage current is exceeded.

Besides the mentioned safety measures, there are a number of other safety precautions which should be practised.

Safety measure Reason Implication
1.      

Never overload a plug.

A multi-plug adaptor will allow you to use as many appliances as needed without the risk of overheating.

It can cause a fire.

People could be injured.
2.

Electric wires must be wired correctly.

Worn or frayed electric cords can cause accidents. Someone could be electrocuted.
3.

Broken plugs should not be used.

It could cause an accident. Broken plugs could cause someone to be electrocuted.
4.

Never pull out a plug by the cord

Pull it out by

gripping the plug

itself, and make

sure the power is

switched off.

Pulling a plug out by the cord can expose bare wires.

Putting electrical wires directly into a socket can cause accidents.

You could electrocute yourself
5.

Wire plugs properly

 

Touching live wires could cause an accident You could electrocute yourself

Using portable electric tools

The following checks should be made before operating any electrical tool:

  • Check that the machine has 3 core wiring or is doubly insulated.
  • Check that the “earth” (green/yellow) wire is connected to the earth pin of the plug with sufficient slack to ensure that the earth wire will be the last to be disconnected from its pin if the wires are pulled excessively.
  • Check that the earth wire is in full contact with the metal body of the tool. This does not apply to double insulated appliances, because they have no earth wire.
  • Ensure that the “live” wire is connected to the correct terminal in the plug. This will ensure that the electrical current goes directly to the operating switch.
  • Note: Where two wires have the same colour, the live one would be indicated by a slight ridge or line of colour.
  • Though the tool may be of double isolation design, it is always advisable to ensure that the electrical supply is fitted with earth leakage protection.

Maintenance of portable electrical equipment, including extension cords

A competent person should be responsible for the monthly inspection of such tools and findings must be recorded in a register.

Particular attention should be paid to:

  • Loose connections.
  • Cracked and broken insulation.
  • Earth continuity.
  • Faulty switches.
  • Joins in flexible cords.
  • Correct polarity of the leads.

Using hand tools

  • Hand tools must be kept in good condition.
  • Mushroomed chisels must be ground down and chisel cutting edges kept sharp.
  • Hammer handles must be without cracks or splinters, fixed with correct wedges, where applicable and no welded galvanised piping used as handles.
  • Files must be provided with handles and screwdrivers handles must be tight.
  • The bits of screwdrivers must be square and sharp.
  • Pick handles must be splinter-free and fitted properly so that it will not slide down onto the workers hands or fly off the end.

 

Precautions when using an angle grinder

  • Only the correct type of disk should be used (grinding, masonry cutting or steel cutting).
  • The correct disk for the task is absolutely essential.
  • The prescribed/recommended revolutions per minute should not be exceeded.
  • The machine guard must be in place when the grinder is used.
  • Eye protection and suitable protective clothing must be worn by the operator and assistant.
  • All electrical connections such as the on/off switch, cable and plug, must be in good working order.
  • Use the correct tools when changing disks.
  • Do not stand in line with the cut when cutting or grinding. The machine may slip and this could result in serious injury.
  • Always hold the machine in both hands when starting and during use.
  • Never put the machine down until it has stopped completely.

 

Fitting a grinding wheel properly to a grinder

  • Select the correct type of grinding wheel for the operation, look for cracks in the wheel and execute the ring test.
  • Check for any cracks and execute the ring test.
  • Ensure that the wheel speed, as recommended by the manufacturer, will not be exceeded.
  • The hole must not be enlarged and the grinding wheel must not be forced over the spindle.
  • Use recessed matching flanges and clean spacer pads (blotting paper) that cover at least one third of the wheel diameter at each side of thereof, when mounting the grinding wheel.
  • Only tighten the nut enough to hold the wheel firmly and ensure that it is in balance.
  • Replace the grinding wheel guard.
  • Adjust the tool rest so that it is no more than 3 mm away from the wheel face, square to it and at axle height.
  • Stand aside and let the wheel run for a minute before grinding.

Building or breaking down of stacks

  • Sound and level floors, strong enough to bear the burden, are essential.
  • No stack may be higher than three times its width, measured at the narrowest part of the stack.
  • Stacks should be bounded and interlocking.
  • Aisles and thoroughfares should be kept clear.
  • Stacks MUST NOT OBSTRUCT firefighting equipment, ventilation, emergency exits or lighting in the storage area.
  • Whenever stacks have to be broken down, for distribution purposes or from the danger of collapsing, they must always be broken down from the top. Should they start to collapse, it is important to break them down as soon as possible, in order to reduce the risk.
  • Stacks must always be climbed with ladders.
  • To hang onto crates or sacks when climbing a stack is extremely dangerous.

Workstations, store rooms and storage facilities

  • Nobody is allowed to smoke, use matches or lighters or have an open fire near any of the above-mentioned facilities.
  • Nobody is allowed to smoke, use matches or lighters or have an open fire near any area where liquid gas or fuel is stored.
  • The collecting of rags or wood shavings that is contaminated with oil or lubricants is forbidden, as it could cause spontaneous combustion or a fire. If it has to be stored, it must be stored in a fireproof container, which has a tight-fitting lid.
  • Fuel may not be stored closer than 100m from any other materials.
  • Storerooms must be kept clean and tidy and no combustible materials may be left lying around.
  • Construction material may not be stored closer than 1,5 meters from any ceiling lights or roof beams.
  • No open lights may be used in storerooms. They must have proper protection.
  • The use of petrol to clean equipment is not allowed. Paraffin or diesel may however be used.
  • No acids may be stored together with any flammable liquids or material (e.g. battery acid or paint).
  • Escape routes must be visible and be un obstructed to ensure a safe exit in the event of an emergency.
  • Material must be stored in such a way to prevent the spread of an accidental fire.

General safety precautions on any premises

  • All stairways, passages, basements, etc, where the lack of natural light may pose a hazard, has to be adequately lighted by artificial light sources.
  • All walkways, stairs and emergency exits MUST AT ALL TIMES be kept clear of any obstruction.
  • All openings in floors or stairwells through which a person may fall, has to be adequately boarded over or be enclosed by guardrails or other fencing material, to a height of at least 900 mm from the floor/ground level. The guarding may have to be removed upon occasion for the access of persons or material.
  • Should work be carried out at an elevated level, access to the immediate area below should be denied to all other people than the workers. Where this should be above an entrance or other area where people regularly have to work or pass through, a suitable net or catch platform has to be erected.
  • NO debris shall be disposed of from an elevated position, other than through a chute or builder’s hoist, unless suitable precautions have been taken.

 

Possible chain of event without having safety measures in place

Ladders

Safety measure Reason Implication
1. Do not use metal ladders near overhead electrical supply lines. The ladder may touch the overhead lines. You may be shocked.
2. Fit ladders with non-skid feet and position it correctly. The ladder may slip. The ladder may topple and you may be injured.
3. Do not position ladders in front of a door. Someone may open the door whilst you are on the ladder. You may fall off the ladder.
4. Do not use a ladder that is old or in need of repair. The ladder may break. You may injure  yourself if it breaks.
5. Do not leave ladders lying on the floor. You may trip on a ladder that is left lying on the floor. You may injure yourself in the process.
6. Place ladders correctly. It may fall over. You may be injured in the process.
7. Hold on to the ladder with both hands whilst climbing it. You may loose your grip and fall off. You may fall and injure yourself.
8. Ensure that ladders are always clean from grease or oil when using them. The ladder could be slippery and you could lose your grip. You may fall and injure yourself.

Floor openings, stairways and open sides of buildings

Safety measure Reason Implication
1. They must be enclosed with proper guards or rails of at least 900 mm high, but not higher than 1 000 mm. People could trip or fall into them. People could be injured.
2. When elevated construction is taking place over or near an entrance, a net or catch platform must be erected over the entrance. Objects could fall on the people walking/standing underneath. People could be injured.

Scaffold planks and supports

Safety measure Reason Implication
1. Scaffolding higher than 2m above floor level must have toe boards with a minimum height of 150 mm fitted to at least three sides of the scaffold platform and in such a way that there are no gaps between the floor and toe boards. To prevent objects accidentally falling off. People could be injured from objects falling on their heads.
2. Scaffold planks must be at least 228 mm wide and 38 mm thick. Planks must be wide enough to stand comfortably on and strong enough to carry weight of the workers. The scaffold planks could break and the workers may be injured in the process.
3. They must rest upon at least three supports and must not project more than 230 mm from the end supports. If the scaffold planks are too long, someone could knock his head on the protruding end supports. It could cause a head injury to a worker.
4. The planks must be securely fastened to prevent displacement. The planks could shift and become unstable and fall off. Workers on the scaffolding could be injured.
5. Oil/petrol drums and ladders should never be used as scaffolding Drums do not have anything to fasten the scaffolding planks onto, which makes it unsafe. Workers could be injured if the scaffold planks are displaced.

Excavations

Safety measure Reason Implication
1. Excavations which are accessible to the public must be fenced off with a barrier or fence of at least 1 m high and provided with red warning lights at night. People may trip and fall into the hole. People could be injured.
2. Excavations that are more than     1,5 m deep – sides must shored up and braced/graded properly. The sides may collapse. Someone could be injured if the sides collapse onto them.
3. A competent person must inspect the excavation for safety before the commencement of each shift and/or after any rainstorm. The excavation might have become unstable. Someone could be injured if the excavation collapses.