Chapter 5

Question 1

Common mechanical injuries

Answer 1

1. Cutting and tearing
2. Shearing (a kind of cutting)
3. Crushing (squash)
4. Breaking
5. Straining
6. Spraining (twist)
7. Puncturing

Question 2

Cutting and Tearing

Answer 2

•The seriousness of cutting and tearing the skin by a sharp edge depends on how much damage is done to the skin, veins, arteries (الأوردة والشرايين), muscles, and even bones.

Question 3

Shearing (a kind of cutting)

Answer 3

•Power driven shears for cutting paper, metal, plastic and composite materials are widely used in manufacturing. Such machines often amputate(بتر) (cut off)fingers and hands. Such tragedies typically occur when operators reach under the shearing blade to make an adjustment or place materials there and activate the blade before removing their hand.

•

Question 4

Crushing (squash)

Answer 4

•Injuries from crushing typically occur when a part of the body is caught between two hard surfaces that progressively move together thereby crushing anything between them such as:

• a metal stamping machine,
• meshing gears and
• belt pulleys.

Question 5

Breaking

Answer 5

Machines used to deform (change shape) engineering materials in a variety of ways can also cause broken bones

Question 6

Straining

Answer 6

(توتر): A strain results when muscles are overstretched or torn

Question 7

Spraining

Answer 7

•(twist)A sprain is the result of a torn ligament(tissue that connects bones) in a joint. They cause swelling and intense pain.

Question 8

Puncturing

Answer 8

•(ثقب)(cut or stab): Punching machines have sharp tools that can puncture body parts and cause damage to internal organs if safety precautions are not observed or if appropriate safeguards are not in place.

Question 9

Point-of-operation Hazards:

Answer 9

•Are those hazards caused by the shearing, cutting, or bending motions of a machine where human exist.

Question 10

What cause the mechanical injuries??

Answer 10

•Machine – operator contact

Question 11

·The reasons for machine-operator contacts to happen:

Answer 11

• Because of inattention caused by fatigue, (weakness, very tired) distraction, curiosity.
• From machine via flying metal chips, chemicals, and hot metal splashes, and circular saw (منشار)kickbacks.
• As a direct result of machine malfunction (defect, fault), including mechanical and electrical failure.

Question 12

How to avoid or minimize Mechanical Injuries?

Answer 12

•Safegaurding = to protect, secure or to defend

Question 13

Machine safeguarding

Answer 13

is the steps taken to minimize the risk of accidents of machine-operator contact. …..

Question 14

National Safety Council safeguard requirements Safeguards should do the following :

Answer 14

1. Prevent Contact : safeguards should prevent human contact (operator or any other person) with any potentially harmful machine part.
2. Be secure and durable (strong): Workers should not be able to make them ineffective by changingor disabling them.
3. Protect against falling objects: safeguards must also shield the moving part of machines from falling objects.
4. Create no new hazard: safeguards with a sharp edge, unfinished surface, or protruding (extending)bolts introduce new hazards while preventing against the old.
5. Create no interference: Any safeguard that might impedes (slow) an operator from performing the job quickly and comfortably are likely to be ignored or disabled by workers feeling the pressure of production deadlines.
6. Allow safe maintenance: such as lubrication without the removal of guards.

Question 15

Types of point-of-operation guards

Answer 15

1. Fixed guards
2. Interlocked guards
3. Adjustable guards

Question 16

Fixed guards

Answer 16

allow a permanent barrier between worker and the point of operation. Suitable for high production repetitive operations.

Disadvantage: May limit visibility, and normal cleaning and maintenance

Question 17

Interlocked guards

Answer 17

shut down the machine when the guard is not in place.

Advantage: Allows safe access to machine for removing jams or conducting routine maintenance.

Disadvantage: May be sometimes easily disengaged(stopped or get rid of)

Question 18

Adjustable guards

Answer 18

prevent against variety of different hazards.

Disadvantage: Do not provide dependable barrier as other guards and need frequent maintenance.

Question 19

Point-of-operation devices

Answer 19

1. Photoelectric devices: shut down the machine whenever the light field is broken. Do not protect against mechanical failure, and can be only used with machines that can be stopped.
2. Radio frequency devices: are capacitance devices that stop the machine if the capacitance field is interrupted by the workers body or another object.
3. Electromechanical devices: if the worker moves the contact bar beyond a specific point the machine will shut down.
4. Pullback devices: pull the operator’s hand out of the danger zone when the machine starts.
5. Restraint devices: hold the operator back from the danger zone.
6. Safety trip devices: Stop the machine when tripped (skip, fall).
7. Two hand controls: require the operator to use both hands to activate the machine.
8. Gates: provide barrier between danger zone and workers.

Question 20

Feeding and ejection systems

Answer 20

•Feeding and ejection (throw)systems can be effective safeguards if properly designed and used. (keep safe distance from machine)

• Automatic feed
• semiautomatic feed
• Automatic ejection
• semiautomatic ejection

Question 21

Automatic Feed and semiautomatic feed

Answer 21

• Automatic Feed: systems feed stock to the machine from rolls.
  
  • Eliminate the need of operators to enter the danger zone.
  • Limited in type and variations in stock they can feed.
  • Require frequent maintenance.
• Semiautomatic feed: Chutes (slopes), same advantages as automatic feed.

Question 22

Automatic ejection and semiautomatic ejecton

Answer 22

• Automatic ejection:
  
  • systems eject the work hyraulicaalyor mechanically.
  • Operators do not have to reach into danger zone.
  • Disadvantages are debris and noise
• Semiautomatic ejection:
  
  • activated by operator.
  • Similar advantages and disadvantages to automatic ejection

Question 23

Hazards of robots

Answer 23

1. Entrapment of worker between robot and solid surface.
2. Impact(hit) with a moving robot arm.
3. Impact with objects dropped by robot.

Question 24

Robot Safeguards

Answer 24

• Erect a physical barrier around the entire perimeter (boundary) of a robot’s work area. Should be able to withstand the force of the heaviest object the robot could eject (throw).
• Shutdown guard that shuts the robot down if any person or object enters the work envelope.
• Sensitive doors or gates in the perimeter barrier that shut the robot down if opened.

Question 25

Lockout System

Answer 25

• Placing a lockout device such as a padlock(قفل) on an energy isolating device to prevent the accidental or inadvertent(unintentional)energizing of a machine or piece of equipment (Fig).
• Protect people in the workplace from hazardous energy while they are performing service or maintenance on machines, tools and equipment.

Question 26

Tagout system

Answer 26

• Placing a tag(بطاقة)on a energy isolation device to warn people so that they do not accidentally or inadvertent energize a machine or equipment
• Protect people in the workplace from hazardous energy while they are performing service or maintenance on machines, tools and equipment

Question 27

Provisionsof OSHA’s standard lockout/tagoutsystem

Answer 27

Energy control program

organizations must have:

• An energy control program that have fully documented energy control procedure,
• provide employee training, and
• ensure periodic inspections. :
  
  • At least annually, and certify the inspections have taken place.