NEBOSH IGC Question and Answers PART 8 Cont..
161) In relation to the use of 240 volt hand held electrical tools,
Outline the possible dangers
Electrical shock & burns.
Fire, explosion.
Arching
Trips & falls.
Describe suitable precautions which should be taken to control such dangers,
Reduced voltage operation.
Fuses & residual current devices (RCD’s).
Double insulation & inspections.
162) A) Describe the function & limitations of a fuse as an electrical protection device.
1) AMP rating.
2) Equipment protection.
3) Basic operation of a fuse in an over current situation.
LIMITATIONS:
The ease of using an incorrectly sized fuse and the slow response time of fuses.
B) Explain one advantage, which a residual current device (RCD) has over a fuse.
The advantages of an RCD include the fact that an RCD’s rapid response time affords some protection against shock (unlike a fuse), and that an RCD is simple and safe for non-electrical personnel to test.
163) Outline the hazards & the precautions to be taken when changing batteries.
Hazards:-
Evolution of flammable gas.
Contact with acid.
Manual handling.
Precautions:-
PPE suitable for gas shall be used i.e. organic vapour mask or air line respirator).
To avoid acid burn hand gloves shall be used while handling batteries.
While manual handling, suitable body posture is required to work related upper limb disorder. Also protection from electrical shock shall be taken.
164) A) Outline the effects on human body from severe electric shock.
Possible physical effects of electric shock on the body.
Muscular spasm that can cause interference with cardiac and respiratory functions.
Electrical burns.
Damage to the internal organs.
Secondary effects- falls from the height.
B) Describe how earthing can reduce the risk of receiving an electric shock.
All metal work with which a person may come into contact should be connected to earth in order to provide lower resistance, pathway than through the human body, and at the same time producing a sufficient current increase to ‘blow’ a fuse or to ‘trip’ a circuit breaker.
165) A) Outline the effect on the human body of a severe electric shock.
The main effects of electric shock as being interference with heart rhythm and breathing.
Severe burn.
Damage to the internal burn.
Secondary effects – Falls.
Emergency action to take if a person suffers a severe electric shock.
Raising the alarm.
Isolating the supply.
Administering the first aid as a appropriate.
Remaining with causality.
B) Outline practical measures to reduce the risk of electric shock when using portable electrical appliances.
Correct selection of equipment.
Regular maintenance & testing.
Use of insulating PPE.
Reduced voltage system.
Correct use of protection devices (RCD’s, fuses etc.)
166) Describe the principles of operation of the following types of electrical protection:
i) Earthing:-
Resistance of the earth circuit being very low such that the current flows to earth by the path of least resistance and that all metal work should be bonded to an earth connection.
ii) Reduced Voltage:-
Reduction of mains voltage by a transformer to a lower safer voltage typically 110 or 55 volts.
Diagram – centre trapped transformer.
167) Describe the functions & limitations of a fuse as an electrical protective device.
Fuse:- A ‘weak link’ in the live supply that melts when heated by excess current flowing under fault conditions, thus protecting the equipment & its wiring.
Limitations:-
1) Its action being usually to slow to prevent electric shock.
2) ease of replacing it inappropriately with a fuse of higher rating or other object.
B) Identify TWO advantages that a residual current device (RCD) has over a fuse.
The advantages of an RCD over a fuse.
1) Rapid & sensitive electrical response.
2) The ease of safety of testing & resetting and / or the fact that it is not easily defeated.
168) In relation o electrical safety, explain the meaning of the following terms:
1) Isolation:-
Refers to shutting off the electrical supply to an item of equipment or part of an electrical system by a safe means in order, for instance, to carry out maintenance work.
2) Earthing:-
Is a means whereby electrical equipment and conductive items are connected to earth by a cable or pipe work such that the route to earth provides the path of least resistance to a current flowing under fault condition.
3) Reduced Voltage Operation:-
Commonly used on construction sites, involves the reduction of mains voltage by a transformer to a lower safer voltage typically 110 or 55 volts.
4) Over current protection:-
Is a method of preventing the flow of excess current by cutting the supply under fault conditions by means of a fuse or circuit breaker.
169) Describe options for reducing the risk of electric shock when using a portable electric drill on a construction site.
Correct selection and maintenance / testing through training.
Use of insulating PPE, to specific measure such as,
i) Earthing.
ii) Reduced voltage system.
iii)Correct use of protection devices (RCD’s, fuses etc).
170) A) Outline the efforts on the human body from a severe electric shock.
Violent muscular contraction caused by contact with high voltage supplies can through causalities some way from the original point of contact.
In case of electric shock breathing & heart beat can stop together, accounting pallid for the pallid blue tinge to the skin sometimes seen.
There may also be burns visible which can indicate contact with electricity.
B) Describe earthing can reduce the risk of receiving an electric shock.
Earthing:- provides a suitable connection to earth through the metal enclosures, conduit, frame etc. this gives electricity a clear path to earth and thus protect body from becoming the earth path, it used regular inspections and tests of the earth should be carried out by a competent person.
171) List the items that should be included in an inspection checklist designed to ensure the safety of portable electrical appliances.
Equipment appropriate for task & environment.
Equipment tested:- equipment, plugs, connectors & cable free from damage, correct wiring & sound connection, fuses & other means of prevailing excess current in place and correct rating.
Accessible appropriate means of isolation.
System not overloaded.
MACHINERY & GUARDING (PUWER)
172) Provides sketches to show clearly the nature of the following mechanical hazards from moving parts of machinery.
1) Entanglement:
2) Crushing:-
3) Drawing:-
4) Shear:-
173) Describe four types of machinery guarding & give an example of where each might be used.
Fixed Guard:- Fixed guards on a conveyor.
Interlock Guard:- On a power press.
Automatic trip guard.
Adjustable Guard.
174) Outline four hazards & corresponding precautions to be taken when using conveyor system for moving materials within a work place.
Traps, drawing in:- Precautions:- Nips guard & trip devices.
Entanglement:- Fixed guard, avoid loose clothing.
Impact against overhead systems:- bump caps, barriers etc.
Manual handling Hazards:- Appropriate height of conveyor, mechanical aids etc.
Noise:- various attenuation methods, hearing protection.
Contact hazards:- Belt edge protection, restriction access, elimination of sharp edges.
175) Identify four mechanical hazards presented by pedestal drills & outline in each case how injury may occur.
Entanglement:- with belt or chuck.
Ejection:- Ejection of a broken bit or work piece.
Stabbing or puncture:- from unsecured revolving work piece.
Impact:- from unsecured revolving work piece.
Drawing in:- by itself.
176) Outline practical precautions that should be taken prior to the maintenance of machinery.
Operation of the PTW system.
Isolation / locking of source of energy.
Dissipation of stored energy (pressure release, prevention of gravity falls, cooling hot surfaces etc.
(barriers, warning signs)
Means of escape.
Provision of PPE.
Use of skilled personnel.
Provision of a safe working environment (ventilation, lighting).
177) With reference to an accident involving an operator who has come into contact with a dangerous part of a machine Describe,
1) Possible immediate causes:-
i) Inadequate or non-existence safety devices.
ii) Poor Housekeeping.
iii) Loose clothing.
iv) Machine malfunction.
v) Operator error.
2) The possible route (underlying causes).
i) Inadequate training, ‘IT IS’.
ii) Poor maintenance.
iii) Inadequate risk assessment.
iv) Personal factors such as, stress, fatigue.
v) The influence of drugs & alcohol.
vi) Purchasing of equipment policy & selection of personnel.
178) A) Identify:-
1) Two mechanical hazards associated with moving parts of machinery.
i) From moving parts of machinery.
ii) Impact, entanglement, shearing, ejection, cutting, abrasion.
2) Two non-mechanical hazards to which a machine operator may be exposed.
Hazardous substances.
Extreme of temperature.
Ergonomic issues.
B) List a hierarchy of control measures that may be used to reduce the risk of injury from dangerous parts of machinery.
1) ‘FIAT’ or other types of devices.
2) Safety aids such as holders, push stick, jigs & ‘IT IS’.
179) A) In relation to machine safety, outline the principles of the following types of machine guards.
i) A fixed guard:-
Physical barriers, not connected to machine controls, no moving parts, requires a special tools to remove.
ii) An interlocked guard:-
Linked to machine controls, no moving parts, requires a special tools to remove.
B) List TWO advantages and TWO disadvantages of a fixed machine guard.
ADVANTAGES:-
i) It is easy to inspect (simplicity) & maintain.
ii) no moving parts, leads to increase reliability.
DISADVANTAGES:-
i) Not being linked to a control means that access when required is afforded should it be removed.
ii) it is fixed and requires a special tools to remove means that access when required is more difficult, a physical barrier may also hamper inspection of the machine or work particularly if it is solid.
MAINTENANCE & CONFINED SPACES.
180) Explain the practical measures that should be taken to ensure maintenance work is undertaken safely in an underground storage vessels.
Essential elements of PTW such as pre-cleaning, purging, testing, emergency provision, lighting, access & training.
PTW PROCEDURE:-
i) Pre-cleaning.
ii) Atmospheric testing.
iii) Competent Personnel.
iv) Suitable tools.
v) Adequate lighting.
vi) Appropriate PPE.
vii) Good communication system.
Emergency arrangement for safe evacuation of staff should the need arise.
NEBOSH IGC Question and Answers PART 10 Cont.....