Mechanical Hazards

TOPIC 7a MECHANICAL HAZARDS

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TOPIC 7a : MECHANICAL HAZARDS

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OBJECTIVES: MECHANICAL HAZARDS

By the end of this topic, you should be able to:

1. Describe common of injuries resulting from mechanical hazards;

2. Explain the main requirements for safeguards

3. Apply the precautions to mechanical hazards.

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7.1 Definition of Pressure Hazards 7.1.1 Wound and Tearing

7.1.2 Shearing7.1.3 Crushing7.1.4 Fractured7.1.5 Straining and Spraining7.1.6 Puncturing 7.2 Safeguards7.2.1 Point-of-operation Guards7.2.2 Point-of-operation Devices7.2.3 Feeding and Ejection System7.2.4 Lockout/Tagout Systems7.3 Mechanical Hazard PreventionSummary

TABLE OF CONTENT : MECHANICAL HAZARDS


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INTRODUCTION

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As the term suggests, mechanical hazards are associated with power-driven machines, whether automated or manually operated.

Concerns about mechanical hazards date back to the Industrial Revolution and the earliest days of mechanization.

Machines – whether driven by steam, hydraulic, or electric power has introduced new hazards into the workplace.

In spite of advances in safeguarding technologies and techniques, mechanical hazards are still major concerns today.

In addition, the advent of automated machines has also fresh concerns about workplace safety.


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7a.1 COMMON MECHANICAL INJURIES

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In an industrial setting, people operate machines that are designed to drill, cut, shear, punch, chip, staple, stitch, abrade, shape, stamp, and slit materials such as metals, composites, and plastics.

These processes are purely mechanical; they cause material to be deformed or broken into smaller pieces.

If appropriate safeguards are not in place or if the operators themselves fail to follow safety precautions, they may be hurt by these machines.


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7a.1 COMMON MECHANICAL INJURIES

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7a.1.1 WOUND AND TEARING

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A cut occurs when our skin suddenly comes into contact with a sharp edge.

Tearing implies further opening of a cut through strong forces.

The human body's outer layer or skin consists of the epidermis which is the tough outer covering; - the dermis which is the thick part beneath the epidermis;- the capillaries which are the tiny blood vessels that branch off from small arteries and veins in the dermis;


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7a.1.1 WOUND AND TEARING

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- the veins which are the blood vessels that collect blood from the capillaries and return it to the heart; - the arteries which are the larger vessels that carry blood from the heart to the capillaries in the skin.

Deeper down below the skin are the muscle tissues which in turn wrap around the bones.

How serious is a cut or tear depends on how much damage is done to the skin, veins, arteries, muscles, and even bones.


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7a.1.2 Shearing

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To understand what shearing means, imagine using a paper cutter. Power-driven shears for cutting paper, metal, plastic, and composite materials are dangerous because of their extreme cutting properties.

However, they are widely used in manufacturing for cutting various materials to different sizes.


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7a.1.2 Shearing

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You must have heard of, or read news reports about, how such machines often amputated fingers and hands of careless workers.

Such tragedies typically occurred when the operators reached under the shearing blade to make an

adjustment or placed materials there and accidentally activated the blade before fully removing their hands.


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7a.1.3 Crushing

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Injuries from crushing can be particularly debilitating, painful, and difficult to heal.

They occur when a part of the body is caught between two hard surfaces that progressively move together, thereby crushing anything between them.

Crushing hazards can be divided into 2 categories: i. squeeze-point typesii. run-in points.


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7a.1.3 Crushing

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1. Squeeze-point hazards

Squeeze-point hazards exist where two hard surfaces, at least one of which must be in motion, close in together to crush any object that may be between them


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7a.1.3 Crushing

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2. Run-in point hazards

Run-in point hazards exist where two objects, at least one of which is rotating, come progressively closer together. Any gap between them need not become completely closed. It needs only to be smaller than the width of the object or body part to be lodged in it. Meshing gears and belt pulleys are examples of run-in point hazards.


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7a.1.4 Fractured

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Machines used to deform raw materials such as wood and steel in factories can easily break human bones. A break in the bone is known as a fracture. Fractures are classified as:(a) Simple;(b) Compound;(c) Complete; and(d) Incomplete.


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7a.1.4 Fractured

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Type of Fracture Injuries1. Simple fracture A break in a bone that does not pierce the

skin.2. Compound fracture A break that has broken through the

surrounding tissue and skin.3. Complete fracture Divides the affected bone into two or more

separate pieces4. Incomplete fracture Leaves the affected bone in one piece but

cracked.


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7a.1.4 Fractured

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Other types of fractures include transverse fracture, oblique fracture and comminute fracture.

A transverse fracture is a break at right angles to the axis of the bone, while an oblique fracture is diagonal.

Comminute fracture on the other hand occurs when the bone is broken into a number of small pieces at the point of fracture.


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7a.1.5 Straining and Spraining

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There are numerous situations in an industrial setting when straining of muscles or spraining of ligaments is possible.

A strain results when muscles are overstretched or torn.

A sprain is the result of torn ligaments in a joint.

Strains and sprains can cause swelling and intense pain.


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7a.1.6 Puncturing

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Punching machines that have sharp tools can puncture a body part if safety precautions are not observed or if appropriate safeguards are not in place.

Puncturing results when an object penetrates straight into the body and pulls straight out, creating a wound in the shape of the piercing object.

The greatest risk with puncture wounds is causing damage to internal organs.


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7a.2 SAFEGUARDS

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Modern machinery has various mechanisms that can rotate, reciprocate, or do both.

You can find many types of tools, bits, chucks, blades, spokes, screws, gears, shafts, belts, and a huge variety of other equipment for manufacturing products.

Certainly, safeguards have to be devised to protect workers from coming into contact with such mechanisms while at the same time allowing work to progress at a productive rate.


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7a.2 SAFEGUARDS

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7a.2 SAFEGUARDS

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(a) Prevent ContactSafeguards would prevent human contact with any potentially harmful machine part.

The prevention extends to machine operators and any otherperson who may need to do so, e.g. the technician or service engineer.


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7a.2 SAFEGUARDS

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(b) Secure and DurableSafeguards should be firmly attached so that they are secure. This means that workers cannot render them ineffective by tampering with or disabling them.

This is critical because removing safeguards in an attempt to speedup production is common practice.


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7a.2 SAFEGUARDS

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(b) Secure and Durable

This should not be encouraged at the expense of work safety.

Safeguards must also be durable enough to withstand the rigors of the workplace.

Worn-out safeguards will become less effective over time, in protecting workers properly.


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7a.2 SAFEGUARDS

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(c) Protect against Falling ObjectsObjects falling onto moving machine mechanisms increase the risk of accidents, property damage, and injury.

Objects that fall on a moving part can be quickly hurled out, creating a dangerous projectile.

Therefore, safeguards must do more than just prevent human contact.

They must also shield the moving parts of machines from falling objects.


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7a.2 SAFEGUARDS

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(d) Create No New HazardSafeguards should overcome the hazards in question without creating new ones.

For example, a safeguard with a sharp edge, unfinished surface, or protruding bolts introduces new hazards while protecting against the old.


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7a.2 SAFEGUARDS

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(e) Create No Interference

Safeguards can interfere with the progress of work if they are not properly designed.

Such safeguards are likely to be disregarded or disabled byworkers who find such safeguards a nuisance rather than a safety

feature.


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7a.2 SAFEGUARDS

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(f) Allow Safe MaintenanceSafeguards should be designed to allow frequently performed maintenance tasks (e.g., lubrication) to be accomplished without removing them.


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7a.2 SAFEGUARDS

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(g) Construction of SafeguardsDesign and construction of safeguards are highly specialized activities requiring a strong working knowledge of machines, production techniques, and safety.

However, it is critical that all of the factors explained in thissection be considered and accommodated during the design process.


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7a.2.1 Point-of-Operation Guards

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Safeguards are most effective when used at the point of operation, which is where hazards to humans exist.

Point-of-operation hazards are those caused by the shearing, cutting, or bending motions of a machine.


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Pinch-point hazards result from guiding material into a machine or transferring motion (e.g., from gears, pressure rollers, or chains and sprockets).

Single-purpose safeguards, because they guard against only one hazard, typically are permanently fixed and non-adjustable.

Multiple-purpose safeguards, which guard against more than one hazard, typically are adjustable.


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There are 3 types of point-of-operation guards: i.Fixedii.Interlockediii.Adjustable

Each has its own advantages and limitations.


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Type of Guard Explanation1. Fixed guards Fixed guards provide a permanent barrier between

workers and the point of operation. They offer the following advantages:

They are suitable for many specific applications, can be constructed in-plant, require little maintenanceand are suitable for high-production, repetitive operations.

Limitations include the following: They sometimes limit visibility, are often limited to specific operations, and sometimes inhibit normal cleaning and maintenance.


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Type of Guard Explanation2. Interlocked guards Interlocked guards shut down the machine when the

guard is not securely in place or is disengaged.

The main advantage of this type of guard is that it allows safe access to the machine for removing jams or conducting routine maintenance without the need for taking off the guard.

There are also limitations. Interlocked guards require careful adjustment and maintenance and, in some cases, can be easily disengaged.


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Type of Guard Explanation3. Adjustable guards Adjustable guards provide a barrier against a variety

of different hazards associated with different production operations.

They have the advantage of flexibility.

However, they do not provide as dependable a barrier as other guards do, and they require frequent maintenance and careful adjustment.


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7a.2.2 Point-of-Operation Devices

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A number of different point-of-operation devices can be used to protect workers. The six most widely used are explained below:

(a) Photoelectric devices(b)Radio-frequency devices(c)Electromechanical devices(d)Pullback devices(e) Restraint devices(f) Two-hand controls.


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The 6 Point-of-Operation DevicesPoint-of- Operation Devices

Explanation

1. Photoelectric devices

Photoelectric devices are optical devices that shut down the machine whenever the light beam is broken.

These devices allow operators relatively free movement. They do have limitations, including the following:

They do not protect against mechanical failure, they require frequent calibration, and they can be used only with machines that can be stopped.


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Point-of- Operation Devices

Explanation

2. Radio-frequency devices

Radio-frequency devices are capacitance devices that brake or quickly slow down the machine if the capacitance field is interrupted by a worker's body or another object.

These devices have the same limitations as photoelectric devices.


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Explanation

3. Electromechanical devices

Electromechanical devices are contact bars that allow only a specified amount of movement between the worker and the machine.

If the worker moves the contact bar beyond a specified point, the machine will not work.

These devices have the limitation of requiring frequent maintenance and careful adjustment.


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Explanation

4. Pullback devices Pullback devices pull the operator's hands out of the danger zone when the machine starts to operate.

These devices eliminate the need for auxiliary barriers. However they also have limitations.

They limit operator movement, must be adjusted for each individual operator, and require close supervision to ensure proper use.


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Explanation

5. Restraint devices Restraint devices hold the operator back from the danger zone.

They work well, with little risk of mechanical failure.

However, they do limit the operator's movement, must be adjusted for each individual operator, and require close supervision to ensure proper use.


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Explanation

6. Two-hand controls Two-hand controls require the operator to use both hands concurrently to activate the machine (e.g., a paper cutter or metal-shearing machine).

This ensures that his hands cannot stray into the danger zone.

Although these controls do an excellent job of protecting the operator, they do not protect onlookers or passers-by.

In addition, some two-hand controls can be tampered with and foolishly made operable using only one hand to save time.


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Explanation

6. Two-hand controls Two-hand controls require the operator to use both hands concurrently to activate the machine (e.g., a paper cutter or metal-shearing machine).

This ensures that his hands cannot stray into the danger zone.

Although these controls do an excellent job of protecting the operator, they do not protect onlookers or passers-by.

In addition, some two-hand controls can be tampered with and foolishly made operable using only one hand to save time.


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7a.2.3 Feeding and Ejection System

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Feeding and ejection systems can be effective safeguards if properly designed and used.

There are 4 types of feeding and ejection systems available for use with modern industrial machines, as below:(a) Automatic feed systems;(b) Semi-automatic feed systems;(c) Automatic ejection systems; and(d) Semi-automatic ejection systems.


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Feeding and Ejection Systems

Explanation

1. Automatic FeedSystems

Automatic feed systems feed stock to the machine from rolls.

Automatic feeds eliminate the need for operators to enter the danger zone.

Such systems are limited in the types and variations of stock that they can feed.

They also typically require an auxiliary barrier guard and frequent maintenance


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Explanation

2. Semi-automatic Feed Systems

Semi-automatic feed systems use a variety of approaches for feeding stock to the machine.

Prominent among these are chutes, moveable dies, dial feeds, plungers, and sliding bolsters.

They have the same advantages and limitations as automatic feed systems.


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Explanation

3. Automatic EjectionSystems

Automatic ejection systems eject the work pneumatically or mechanically.

The advantage of either approach is that operators do not have to reach into the danger zone to retrieve work pieces.

However, these systems are restricted to use with relatively small stock. Potential hazards include blown chips or debris and noise.

Automatic ejectors can be noisy.


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Explanation

4. Semi-automaticEjection Systems

Semi-automatic ejection systems eject the work using mechanisms that are activated by the operator.

Consequently, the operator does not have to reach into the danger zone to retrieve work pieces.

These systems do require auxiliary barriers and can be used with a limited variety of stock.


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7a.2.4 Lockout/Tagout Systems

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One of the most effective systems to control hazardous energy today is the tagout system.

This method is created to protect people from accidental activation of a machine when it is suppose to be shut.

This is very important because OSHA’s statistics shows that six percent of workplace deaths are caused by accidental or inadvertent activation of a machine while it is being serviced or repaired.


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In the lockout system, a lockout device such as a padlock is placed on an energy- isolating device to prevent the accidental or inadvertent energizing of a machine until the padlock is unlocked.

The padlock will normally bear the name, department and phone extension of the person in-charge.


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The tagout system is similar to the lockout system except that a tag is used instead of a padlock.

The tag must only be used when the lockout system cannot be implemented.

Sometimes a tag and a padlock are used together.


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7a.3 MECHANICAL HAZARD PREVENTION

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No General Precautions 1 All operators should be trained in the safe operation and

maintenance of their machines.

2 All machine operators should be trained in the emergency procedures to take when accidents occur.

3 All employees should know how to activate emergency shutdown controls.This means knowing where the controls are and how to activate them.

The following are general precautions that apply across the board where machines are used:


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No General Precautions 4 Inspection, maintenance, adjustment, repair, and calibration

of safeguards should be carried out regularly.

5 Supervisors should ensure that safeguards are properly in place when machines are in use.

Employees who disable or remove safeguards should be disciplined appropriately.

6 Operator teams (two or more operators) of the same system should be trained in coordination techniques and proper use of devices that prevent premature activation by a team member.


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No General Precautions 7 Operators should be trained and supervised to ensure

that they dress properly for the job.

Long hair, loose clothing, neckties, rings, watches, necklaces, chains, and earrings can become caught in equipment and, in turn, pull the employee into the hazard zone.


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No General Precautions 8 Shortcuts that violate safety principles and practices should be

avoided.

Deadline pressures should never be the reason for unsafe work practices.

9 Other employees who work around machines but do not operate them should be made aware of the emergency procedures to take when an accident occurs.


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SUMMARY

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1. Mechanical safety is important and must be addressed consistently with the development of technology worldwide.

2. Management must conduct a safety risk analysis on all mechanical equipment installed at their facilities.

3. From this analysis a safety procedure to handle each machine must be developed and made known to all workers.


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SUMMARY

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3. This will enable workers to understand how to use the machines safely, hence, reducing the numbers of mechanical-related accidents.

4. Workers must also be exposed to periodical mechanical safety training to ensure that they are able to use mechanical equipment at their workplace safely and correctly.


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Mechanical Hazards