engineering & maintenance notes

8/3/2019 Engineering & Maintenance Notes

1/33

MISSJANETOW

USU-ANSAH

[Y

ear]

ENGINEER

INGAND

MAINT

ENANCE

[Type the abstract of the document here. The abstract is typically a

short summary of the contents of the document. Type the abstract ofthe document here. The abstract is typically a short summary of the

contents of the document.]

HYPERLINK INFORMATION TECHNOLOGY

[Type the company address]

[Type the phone number]

[Type the fax number]


2/33

Engineering and maintenance

Introduction

Engineering is basically the practical application of scientific knowledge in the design,

construction and control of machines, public services such as roads, bridges, etc, electricalapparatus and appliance, chemicals, etc. Examples of engineering programmes/courses studiedin the tertiary institutions elsewhere include electrical engineering, civil engineering, chemical

engineering, computer engineering, etc.

Work, science or profession of an engineerAn Engineer, is person who design, construct/builds and maintains engines, machines, bridges, railways, etc, because he/she is skilled in that

respect/direction.

Engineering is very relevant in the environment in which we find ourselves because it is themeans by which is we can obtain and control everything including equipment or machines

around us. That is also enhance our lives in many ways

Maintenance: To maintain means to cause to continue or keep in existence at the same level, or

stand and by regular checks on the performance of a facility.

The objective of forming and operating an industrial company is to make profit and hence no

business can continue to function unless a profit is made.

These facts although obvious, are frequently overlooked by many persons who are not ultimatelyconcerned with company management.

All activities within a company should be so organized and co-ordinate that their overall effectand ultimate aim is to increase the profitability of the business.

The introduction of any new activity to the modification of an existing one should be critically

examined to ensure that it assists the company to achieve us max objective.

Industries function by producing goods and services which can be sold for a profit to enable the

company to continue to operate.

The equipment being used for production must operate efficiently and accurately at the required

level of production and hence the need for regular maintenance.


3/33

Definition of some Terminologies

A current is the flow of electric charge in a circuit. Its SI unit is the ampere (A)

Asource can also be called the voltage. Example includes the socket at home and offices.

A loadaccepts energy from a system. Example includes blender pressing iron, mobile phones etc

Basic Theory of Electricity

a. Electricity is a convenient form of energy that can produce heat, light,

b. It can be generated, transmitted, and controlled. a. Electricity is present in all matter.

I) All matter is made of combinations of elements called molecules, which are in turn made up of

even smaller units called atoms.

2) An atom is the smallest amount of an element that retains all the properties of' the clement.

3) An atom may be broken down into smaller pieces whose relationships have been concealed or

as a miniature solar system.

a) The center of the atom consists of protons, which carry a positive electrical charge, and

neutrons, which carry no charge.

b) Electrons, which carry a negative electrical charge, orbit around the center of the atom.

c) Two kinds of electrons exist:

- Planetary electrons cannot be readily moved from their orbits.

- Free or valance electrons are loosely held in the atom's outer orbit and may drift into orbits ofnearby atoms.

d) When an atom has an equal number of protons and electrons, it is said to be electricallyneutral.

1. How is electric current produced?

a. An atom becomes electrically charged when it has fewer electrons than protons than protons.

b. The random wandering of valence electron from one atom to another does not producepermanent changes.

c. The overall material will remain the same if outside influence does not disturb the balance.


4/33

d. If an outside force, such as a battery voltage, disturbs the balance, the loosely-held outerelectrons will tend to move in one direction.

I) when voltage is applied across the ends of a conductor, the electrons, charge up and then had

been involving in different directions, are forced to move in the same direction along the wire.

2) The individual electrons all along the path forced to leave their atom and travel a short

distance to another lt need~ an electron.

3) This motion of electrons is transmitted along the path from atom to atom. as the motion of the

whip is transmitted one to the other.

e. This nonrandom flow of electrons is called If' electric current.

f. When the free electrons move randomly, the energy is small, but when they are forced to move

in the same, their collective energy is large and can be used for work.

B. Measuring Electric Current

I. Electron Flow (Amperage)

a. An electric current is a flow of electrons a conductor.

b. The speed of this flow is nearly equal to t of light, mile per second.

c. The of electricity is measured by the number of electrons that pa::,s a point i:l a wire in one

second.

d. An ampere is a measure of electron flow. It represents a of 1 coulomb of electricity (6 billionbillion electrons) past a point e in one second.

e. Compared to a water system, an ampere would be similar to a measure of water flow through apipe, such as gallon per minute.

Electromotive Force (voltage)

a. Electromotive (electron - moving) force or voltage is electrical potential which provides

energy for the movement of electron in a circuit.

b. This electrical potential results from a difference in electron energies at two points in a circuit.

c. This difference in electron energy levels in a circuit can be compared to the potential energy ofwater stored in a high water tower and the kinetic energy of water flowing through the pipe.


5/33

d. Voltage is measured in units called volts (a difference variable) and is abbreviated with the

letter symbols E or V.

e. Compared to system, a volt would be similar to a measure of water pressure in a pipe such as

pounds per square inch.

3. Resistance to Current Flow (Resistance)

a. Resistance is the ability of a material to resist electron flow.

b. Materials vary in their number of valence electrons and in the ease with which electrons will

be transferred between atoms.

c. Resistance is measured in units called ohms.

d. The symbol for resistance is R, and the symbol for ohms is the Greek letter (omega).

Conductors and insulators

Conductors are materials which permit current to flow through.

Insulators are materials which to do not allow current to flow through. Examples of conductorsincludes, aluminum, copper, silver, platinum, bronze, Gold, etc. examples of insulators include,

Glass,. Mica, Air, Rubber. Ceramic, Plastic, Varnish, Paper, Gold and certain Oils.

c. A conductor is a material through which electrons can flow freely.

d. An insulator provides great resistance to electron flow.

c. Resistance is measured in units called ohms.

4. Energy

a. Electrical energy is the amount of work that can be by voltage and current over a specific

period of time.

b. The unit for measuring electrical energy the watt-hour (more commonly spelled as kilowatt

hours with is 1000 watt hours); it is usually designated by the letter kWh.

c. The mathematical relation between voltage V, ampere A, resistance R, and electrical energy E,

is:

E = Power (watts) *Time T (hours)


6/33

5. Power

a. Electrical power is the amount of work that can be done by voltage and current.

b. The unit for measuring electrical power is the watt; it is usually designated by the letter W.

c. A watt of power is equal to one volt pushing one ampere of current through a conductor with

one ohm of resistance.

d. The mathematical relation between power and voltage, resistance and amperes IS:

P=I*V

where,

P = power (watts)

I = current (amperes)

V = electrical potential (volts)

Example of Usage of electricity

Most household/farm shop appliances and equipment are rated in watts (see the nameplate or

manufacturer's specifications). Knowing the rating in watts and the voltage to be used (normally

120 or 240), the flow of the current in the circuit for the appliance or equipment can becalculated.

e.g.

You have purchased a 120 volt plug-in electric space heater for use in your shop. It is rated at

400 watts. How much current will the heater drew?

Solution:

P=I*V

Or,

I = P divided by V

I=P/V


7/33

where,

P = 400 watts

V = 120 volts

Therefore, I=400/120,

1= 400 divided by 120 = 3.33 amperes

f. The mathematical relation between power and voltage, resistance and amperes can be rewritten

as:

1) P = I*V and, V=I*R

d. Ohm's Law

1. The physicist, George Simon ohm, discovered that the flow of electrical current through a

conductor is directly proportional to the electromotive force that produces it and inverselyproportional to the resistance in the conductor

a. If the resistance to electron flow through an electrical device is cut in half, the currentamperage doubles.

b. If the resistance remains constant, but the voltage is doubled, the current amperage doubles.

3. This relationship is expressed in ohm's law as E = IR.

a. I equals current in amperes.

b. E equals potential energy in volts.

c. R equals resistance in ohms.

Types of Electricity

1) Direct Current (DC)

a. Electrons flow constantly in one direction.

b. This is the type of electricity produced by all batteries

2) Alternating current (AC)

a. Electrons flow first in one direction and then in the reverse direction at a certain rate of

reversal (cycles per second).


8/33

- In the U.S, 60 cycles per second (60 Hertz) is the standard.-In Ghana, 50 cycles per second (50 Hertz) is the standard.

b. AC current has many advantages over DC, i. e., transformers to increase or decrease voltage

can be used only with AC current.

3) Single-phase current

a. This is the typical current supplied to households and businesses where power requirements

are not very high.

b. Single phase current can be provided by two wires.

4) Three - phase current

a. This type of current is designed especially for large electrical loads.

b. It requires at least three wires.

c. Three phase current is actually three single - phase currents combined so that peak voltages are

equally spaced.

5. Sources of Electricity

I) Friction

2) Single-phase current

3) Three - phase current

4) Heat

5) Light

E.g. Photovoltaic

6) Pressure

7) Chemical Action

e.g. a) Primary Cells

I) The combination of certain metals in an electrolyte solution will produce electricity, forexample, copper and zinc in sulfuric acid.


9/33

2) Examples of batteries that produce electricity from primary cells are dry cell (paste-like

electrolyte, carbon and zinc electrodes) and mercury batteries.

3) The zinc is used up in the process and when this happens the batteries go dead.

b) Storage batteries.1) These batteries are similar to primary cells except that the process can be reversed andthe battery can be recharged.

2) Examples of storage batteries are the lead-sulfuric acid batteries used in automobiles,tractors, etc, and the nickel-cadmium rechargeable batteries used in flashlights, radios,

etc.

c. Fuel Cells

1) A container in which fuels react in the presences of an electrolyte and electrons are madeavailable at the negative electrode terminal.

2) Oxygen and hydrogen are used as fuels in space vehicles to produce electricity.

4. Magnetic Action

a. A flow of electrons is produced in a coil of wire which is moving within a magnetic field.1) The magnetic field can be provided by a stationary magnet.2) Movement of the wire can be provided by:b) Falling water turning a turbines shaftc) Atomic power producing steam which turns a turbine shaft

d) An internal combustion engine turning a shaft.

e) This is the most common method of producing electrical energy in large quantities to

serve the home, farm, and industries.

Application of the heating effect of an electric current

When an electric current passes thru a resistor, heat is generated and the temperature of theresistor is raised. The following applications are a few examples of the many in which this effect

is utilized;

(a)Electric fires, cookers etc.The heating element is usually an alloy of nickel and chromium, since this material has a higher

resistivity and is capable of withstanding a high temperature without becoming oxidized whenexposed to the air.

(b)Incandescent Electric lamps

In the incandescent lamp, the filament must be capable of operating for long periods at a higher

temperature without appreciable deterioration and for this duty there are only two materials that

have proved satisfactory, namely, carbon and tungsten. Owning to its relatively low efficiency,the carbon filament lamp however is obsolete.


10/33

The modern tungsten-filament lamp is gas-filled. If the gas were removed from the bulb, loss of

heat from the filament by convention would be prevented: but the, vacuum was the disadvantagethat the filament vaporizes at a lower temperature than it does when gas is present. This effect is

very similar to the variation of the boiling point of water with pressure.

The vaporization of the filament reduces the cross-sectional area of the filament, therebyincreasing its, resistance and reducing the temperature and the luminous intensity of the lamp.

A fuse is a wire or strip of metal inserted in a circuit for the purpose of interrupting or openingthat circuit when the current exceeds a certain prearranged value. The wire is usually made of a

metal such as copper, tin, lead or an alloy which melts comparatively easily.

The fusing current depends upon a large number of factors, such as the material the diameter and

length of the wire, the ventilation of the fuse holder and duration of the current. The fuse wire

should be mounted on a fire proof holder, such as porcelain. Large fuses are often covered with

asbestos sleeves to prevent any metal vapor being deposited on the porcelain when the fuse

'below', since such a deposit may be sufficient to provide a conducting path between the fuseterminals.

(d) Temperature rise permissible in electrical machine.

When a generator is supplying electrical power or an electric motor is supplying mechanicalpower lost in the machine is said to be loaded, and the power lost in the machine is converted

into heat, thereby raising the temperature of the windings. The maximum temperature that is

permissible depends upon the nature of the insulating materials employed.

Resistivity of materials

Materials fall into three categories when taking consideration. The category with resistivity of

the 0 'del' of 10.8 is known as conductors, the category with resistivity falling intermediatebetween these two groups, of the order of I to 103 mm is known as semiconductors.

Metals have resistivity that increase when the temperature increase, for some alloys theresistivity increase, with an increase in temperature, for others it decreases. For semiconductors

and insulators the resistivity decreases with an increase in temp. The changes in resistivity of

semiconductors and insulators with temp are much greater than the change for conductors. Theelectrical properties of materials can be expressed in terms of the bonding between electrons and

atoms in a sold.

In a conductor, the atoms have electrons which are so easily detached that we can consider thereto be a cloud of free electrons in a good conductor. When a potential difference is applied to a

piece of conductor these electron are able to move there the material and so give a current. On

average there is about one free electron for each atom in the material. When the temp isincreased the movement of there free electrons is more impeded by oscillations of the atoms and

so they are not able to move so fast thru the material and hence the current is reduced.


11/33

Thus an increase in temperature leads to an increase in resistivity. In the case of an insulator

there are virtually no free electrons available, all being lightly bound to the atoms. Because ofthis there can be little current, hence a very high resistivity increasing the temperature can

however such a few more electrons free from the atoms and so increase the current, hence

decrease in resistivity.

Semi conductors hence, at room temp, some few electrons, generally about one per million

atoms because of this they have resistivity intermediate between those of insulators a conductor.

Maintenance in industry

Maintenance may be defined as any activity designed to keep or restore equipment, machineryor any other assets in a good working or useable condition before or after a failure. It must

increase the reliability of the asset or the operating system and to quality standards.

The main objective of forming and operating and industry or a company is to maximize profit.No business can continue to function unless a profit is made.

All activities within a company should be so organized and coordinated in such a way that their

overall effect and ultimate aim is to increase the profitability of the business. The introduction of

any new activity to the modification of an existing one should be critically examined to ensurethat it assists the company to achieve its objectives.

To ensure this, the plant or equipment being used must operate efficiently and accurately at the

required level of production, and hence the need for maintenance. There must be no unscheduledstoppage.

In our world today, the intense competitions together with a rapidly advancing technology have

wrought many changes in the pattern and outlook of industry.

New products are continually being developed; new techniques, processes, systems and methods

are being applied. Production levels are being raised while rigid schedules must be adhered tocontinual efforts are made to reduce or stabilize manufacturing costs in spite of rising material

and labor costs, thus making increased machine utilization an economic necessity.

Principles of maintenance

I. Preventive maintenance: Maintenance carried out regularly a, planted carefully inconjunction with production requircll1ents to prevent the failure of equipment during production.

2. Replacement instead of maintenance: This includes operating the equipment until it breaksdown completely then scrapping it off to buy a new one.


12/33

3. Planned maintenance: This form of maintenance includes work organized and carried out

with a forethought control and records. Thus, one can operate the equipment for a period thensell it off before it either breaks down or requires expensive overhaul.

4. Break down Maintenance: Work which is carried out and provision has been made in the

form of spare materials, labor and equipment, that is to say, operate the equipment until it breaksdown then repair it.

Classification of maintenance

Planned and Unplanned

Planned maintenance is work organized and carried out with forethought, control and records to

approved engineering standards.

Types of planned Maintenance

Planned maintenance involves the following:

Preventive Maintenance.

Predictive/Condition based maintenance.

Corrective maintenance.

Various works carried out on a facility at regular intervals with the aim of preventing or at leastminimizing the risk of failure or to keep such failure and or breakdowns within predetermined

economic limits. Careful preventive maintenance follow-up over a sufficient period will reduce

the causes of rush job.

Elements of preventive maintenance

Lubrication: Indicate the type of Lubricant, how much and where to be used.

Inspection: Utilizes only the five human senses, i.e. sight, sound, touch/feel, taste, and perhaps

smell.

Adjustment: Involve a defined tightening or clamping of component to a specific tolerance.

Cleaning: Involves the removal of contaminants, caused by the equipment during operation.egiron fillings and oil leakages, dust.

Replacement: Involves units which wear out or which reliability decreases with age. E.g. filters,belts, seals, contact brushes, etc.


13/33

Corrective maintenance

Work carried out after failure but for which advance preparation or provision has been made.

This is designed to return the component to its normal operating condition.

Planned replacements - replace only when performance fails.

Planned breakdowni.e repair only when performance fails.

Predictive or Condition Based Maintenance

This refers to the act of maintaining a facility depending on its condition using diagnostic

instruments and analytical methods.

Condition Monitoring is the method of establishing the condition of the respective plant andequipment, usually while it is in operation. Monitoring can be carried out continuously or at

periodic intervals on the plant or equipment being monitored. The equipment in use may be for

temperature, vibration and oil (Fluid) conditions.

Advantages of the condition based maintenance

Minimizes unnecessary machine shutdown & opening up, thereby reducing lost production

Reducing the cost of maintenance efforts, thus enhancing morale of employees

Reliability of facility is assured

Safe and Continuous operation

Lower Energy Consumption - i.e. less vibrations, less energy

Extends Bearing Service life - reduced vibration & lubrication failures

Unplanned Emergency Maintenance

It is referred to as emergency maintenance and it is carried out on a facility after failure and forwhich no advance provision has been made by way of materials (spares), lab and tools. This type

maintenance IS however highly undesirable.

Breakdown Maintenance


14/33

A machine is said to 'breakdown' when it is out of order or operation. Its maintenance is

considered as an unplanned emergency maintenance.

Benefits of planned Maintenance

Fewer equipment failures

Early detection of impeding problem resulting in corrective action

before problems occurs.

Efficient manpower utilization and reduction of idle time

Spare parts inventory control

Effective replacement policy

Greater productivity.

Sound standards of safe working and environmental conditions for employ ces, employers andother occupants.

1. Pure maintenance, defined as work undertaken in order to keep or restore a facility to an

acceptable standard.

(a) Maintenance of existing plant, equipment and building,

(b) Rebuilding or reconditioning old instrument and equipment

2. Installation of new equipment and services.

(,1) Installation of new equipment

(b)Alteration or modification of equipment and bui1jings.

(c) Alteration or modification of utilities and special services.

3. Operation and supervision of particular utilities and special services.

(a) Power and its generation

(b) Power supplies and ventilation systems


15/33

4. Miscellaneous duties delegated to the maintenance department because often it is the only

department with the ability to be able to handle or.

(a) Laboratory and site cleaning - roads, f1oors, windows

(b) Waste disposal.

(c) Five fighting services

(d) Site security (laboratory)

Whatever duties are assigned to the maintenance department, the main reason for its existence is:

-To ensure the availability and efficiency of existing instruments, equipment and building in a

manner required by the users.

(a) The instrument, equipment is available for use when required. (b) The instrument, equipmentmust not breakdown during use

(c) The equipment, instrument must operate in an efficient manner.

(d) The down time for maintenai1ce must not interfere with the work of those who make use ofthe instruments.

(e) The down time which may be caused be breakdown should a minimum.

Maintenance in public Service

From our earlier discussion, we considered maintenance in industrial manufacturing concerns inwhich an outage or loss in production can be measured directly in terms of loss of profit. If this

loss production is the result of breakdowns due to insufficient maintenance then the economics

of stand-by equipment replacement units or extra maintenance can be calculated and the profitabilities compared. Breakdown can jeopardize delivery dates and then effect on sales and future

orders can be forecast.

In each case, the cost can be estimated and used by the management to arrive at the effective

decision. This method can also be applied partly by certain public utilities which are required to

pay their way-gas boards water companies public transport, electricity generating and

distribution boards.

In the case of commercial offices and hotels the customer is paying for a service which includes

engineering functions electrical distribution, heating, hot and could water supply, ventilation,elevators (lifts) etc.


16/33

A breakdown of any of these services may not directly, or immediately cause a financial loss but

would eventually reflect back on the reputation of the establishment which in turn could affectbusiness.

There are also many other situations m which failure of engineering and maintenance services

cannot be assessed solely in financial terms. Hospitals function continuously a breakdown oroutage of certain equipment could prove fatal. In such case, it is necessary to install stand by

equipment to carry out repairs and maintenance on the run. A comprehensive maintenance

system is reliable at all times.

The effective disposal of refuse and sewage together with an efficient drainage system are vital

to public Health. Any failure could contribute to the spread of pests and disease within thecommunity. The successful functioning of this stand - by equipment ready to deal with flooding

or other emergencies cannot be overemphasized, as in hospitals measures must be taken to

ensure that the equipment is maintained to minimize the risk of breakdown and death.

The failure of engineering services would not be disastrous, or result in a loss of profit, but itwould cause inconvenience which in the long term can affect productivity.

* The public services do not exist to make profit; their prime function is to provide services for

the community. The value placed upon any particular service and the overall expenditure on it

varies, according to the priorities or the community. These priorities frequently change, beingaffected by national and local politics, public opinions, available resources and public or

governmental pressures. Because of these diverse and often conflicting conditions, it is

impossible standard by which the efficiency economics of any service can be estimated.

* Each situation must be judged upon the conditions prevailing, the arms and object of the

services and the boundaries within which it must operate.

* Within any service, where are sectors in which the economics and efficiencies of the variousfactors can be measured and compared. In such cases, these measurable factors should be

isolated and standards set to enable the optimum use or the existing equipment and resources to

be made.

ROLE OF THE ENGINEERING AND MAINTANANCE DEPARTMENT IN HCIM.

The duties of the maintenance department vary from company to company, and often from

factory to factory within the same company.

The scope and depth to which it executes it duties depend 01, the policy of the company, size andtype of plant type of production and skilled labor available to name but a few of the determinant

factors.

The maintenance department of a small factory may consist or only one or two person(s) who

will tackle all types of maintenance to limited extent and of and elementary nature. Outside

specialized contractors are called in for any faults. When a hotel's building, equipment, and


17/33

grounds are properly maintained, quests will be more likely to enjoy a positive experience during

their stay and hotel's ability to increase revenue is enhanced.

This is the primary job of the engineering and maintenance (E&M) department. When quests

experience poor facilities such as potholes in parking areas, leaking faucets, burned-out light

bulbs, poor heating/cooling capacities, or insufficient hot water, quest dissatisfaction increases,and the hotel's sales potential is diminished. In addition to quest satisfaction, however, an

effective l&M department achieves other important goals including:

Protecting and enhancing the financial value of the building and grounds for the hotel's owners.

Supporting the efforts of the entire hotel department through the timely attention to their E&Mneeds.

Increasing the pride and morale of the hotels staff

Ensuring the safety of those working in and visiting the hotel.

These goals will be achieved if E&M department, using outside consultants and/or contractors ofnecessary, meets its responsibilities for designing and constructing the building (engineering),

maintaining the building (maintenance), and periodically renovating and modernizing it (design

and renovation).

Maintenance of fuses

A fuse is a wire or strip of metal inserted in a circuit for the purpose in interrupting or openingthat circuit when the current exceeds a certain prearranged values.

The fuse was originally invented by Edison in your 1880 and IS being considered as the weakest

link in the electrical circuit. It is the simplest protect device and is used as circuit interruptingdevice short circuit condition. It prevents over heating of the electrical appliances. Its

performance is simple and its design does not need special experience.

Fusing element: A fuse is essentially a small piece of metal connected in between to terminals

mounted on insulated base forms a series part of the circuit.

The duty of the fuse element (wire) is to carry the normal working current safely without

heating, but when the normal working current is exceeded it should rapidly heat up to the vetting

point.

The materials which can be used as fuse wire are tin, lead, Zinc, silver, antimony, copper

aluminum, etc

Arcing time: This is the time accounted for the instant of arc initiated (end of pre-arcing time) to

the instant of arc being extinguished or the arc current becomes zero.


18/33

Types of (uses

The types of fuses include:

i) Expulsion-fuses

ii) Cartridge - Fuses

iii) Liquid Fuses:

a) Oil - break circuit breaker fuses.

b) Oil - expulsion fuses

c) Oil - blast fuses.

iv) Open fuses:

Distribution panels (Distribution Boards)

Electrical energy is generated at the generating stations by dynamos and is distributed atappropriate voltage which constant.

By convention or rule, the voltage at the consumer's terminals must not vary beyond + 5 percent

(%) of the declared voltage. That is to say, if the declared voltage is 230 V, the voltage at theconsumer's premises must not be more than 241.5V and not less than 218.5V the consumer

always connects all the lamps, fans, heaters and other appliances in parallel with supply mains. If

the consumer connects all his lamps say six lamps in series and one of the lamps fuses, and then

no lamp is replaced because the whole circuit has been shorted or short circuited. Moreover thevoltage across each lamp will be the declared by the number of voltage across each lamp = 230v/

= 38.v 6lamps. This is too low for lamps.

Also if one of the lamps develops short circuit then the potential across all the lamps will be

more than the desired value which cause excessive current to flow in the filament of other lamps

thus fusing one or even all of them.

NB: Therefore all electrical appliances like lamps, heaters etc always connected in parallels.

The transmission lines which transmit the electrical energy from the generation station todifferent distribution substations are called feeders. The feeders that are found underground way

are called cables.

These feeders terminate into distributors and the consumers are connected by means of service

mains to distributors. This indicates that the consumer's supply from the mains is always

received on to a distribution panel (board) from which the rest of the loads receive power supply.


19/33

Circuit breaker

Is an interrupting device placed in a circuit to isolate fault circuit time of short circuit.

For low voltage circuits, fuses may be used to isolate the faulty circuit but for higher voltage

(e.g. 3.3kv up wards) isolation is successively achieved by circuit breakers. The differencebetween the fuse and the circuit breaker is that under faulty condition the fuse melts and a new

one is to be replaced while the circuit breaker can closed or break the circuit without any

replacement.

Requirements of a circuit Breaker

The power dealt by the circuit breakers is quite link between the consumers and suppliers. Thefollowing are the necessary requirement for a circuit breaker;

I) It must safely interrupt the normal working current as well as the short circuit current.

2) After occurrence or fault the circuit breaker must isolate the faulty circuit as quickly as

possible, i.e. keeping the delay minimum.

3) It must have a high sense of discrimination if in systems where alternate arrangements have

been made for continuity of supply; it should isolate only the fault circuit without affecting the

healthy ones.

4) I t should not operate when an over current flow under healthy conditions.

Energy conservation opportunities

- Switch off all appliances when they are not in use.

-In the beginning of the nineteenth century, it was riot possible to do day-time work after sunset,

due to lack of adequate light.

In the year 1900, the electric filament lamps came in to the field as a source of lights and theyproved to be the best competitor to gas as sources of light. The electric lamps are preferred to

other sources of illumination for reasons of cleanliness, convenience steady light output and

reliability.

Due to proper sources of good illumination much advancement has been made in the sphere of

the industrialization of countries as it has reduced the difference between day and might. Every


20/33

work which can be done in day-light can equally be done during might time with same efficiency

too bright lights may not be confused as good illumination because it may cause viewing a bitpainful. The best illumination is that which produces no strain on the eyes.

Nature of light

Light is a form of energy which is radiated by bodies whose temperatures are increased. Themain source of lig~1t is the sun which gives out energy in the form of heat and light at a very

high rate (of order of fifty thousand billion horse power), but only a fraction of it reaches the

earth (about 250 billion hp).

Of the total energy received on earth only 40 percent is in the form of light. The energy reaches

earth in a very particular way. They energy transmitted by the sun in received without heating or

lighting the space in between and without any obvious transmitting agency such as copper

conductors in case of electrical energy.

The energy is released only when it strikes a solid object. The energy radiated in such as fashionis called radiant energy. An example of it is a room heater, in which case the heat is felt at a

distance from the radiator.

Light can be obtained from the incandescent bodies. The body which is at a higher temperature

than the surrounding medium radiated energy into the medium. At low temperatures the radiation

is only in the form of heat waves, but it becomes red hot as it emits light waves in addition to

heat waves.

Various colors are obtained when monochromatic wave of different wave length is radiated and

these include violet, blue, and green, yellow, red.

Reflecting and diffusing surfaces: In case of reflecting surface, the light falling on at is reflected

back with least absorption.

In order words, the angle of incidence in equal to the angle of reflection. Sometimes there will be

a sharp image of the light sources and such reflection is called specula reflection.

If light fall on a rough and course surfaces as diffusing glass, plastic frosted glass etc, then the

inherent quantity of the light i.e. brightness is reduced and there will be now image of the source.

The lighting in such cases is diffused in almost all direction.

Reflectors and diffusers are used to reflect the light to a direction where it is required and to

avoid brightness or direct glare respectively.

The various types of reflections in use include the following;

Depending upon therequirement, the lighting schemes can be divided into the following types;


21/33

1) Direct lighting: As significant from the name, in this scheme, the light falls directly on theobject to be illuminated medium. At low temperatures the radiation is only in the form of heat

waves, but it becomes red hot as it emits light waves in addition to heat waves.

This scheme is usually employed in industries, residential lighting and commercial lightingworking strictly' under a direct lighting system will cause strain on the eyes, about 60% of the

light is directed downward.

2) Indirect lighting: It is a system which is widely employed for illuminating drawing offices,

workshops and other places where shadows are to be eliminated. However with this type of

lighting is it found that the requirement of the light is usually more than that of direct lighting?The additional requirement of light falls in the range of 50% to 100%.

The light in this case does not fall on the object directly. The lamps are placed in opaque type

shade and the maximum light is thrown towards the ceiling from where it reaches the object by

diffusion or reflection.

The lightings of both schemes must be cleared regularly so as to have good illumination. If thefittings are not properly clean the illumination will reduce tremendously. No light is directly

thrown downwards. At least 80% of the total light in directed upwards.

3) Semi-direct system: This system is efficient and as well as reduces the chances of glare to the

eye to a considerable extent. The shades used are such a type that about 60% of' the light is

directed downwards and 40% is projected upwards. The most important characteristics of such a

system provide almost distribution of the light which increases the efficiency of the system.

4) Semi-indirect lighting system: In this system the light received by any object is due to

diffused reflection and is directly thrown.

5) General diffusing system: In this case the shades employed will produce equal distribution

upwards and downwards. This system is fact is an ideal system.

Some Terminologies in Lighting

I.Light: It may be defined as that radiant energy in form of waves which produces a sensation ofvision upon the human eye.

2.Luminous flux: it is defined as the energy in the form of light waves radiated per second from

a luminous body e.g. incandescent lamp.

3.Luminous Intensity: The luminous intensity of an object in the flux emitted by the source per

unit solid angle.

4.Lumen: It is the unit of flux per unit angle from a source of candle power.


22/33

5. Luminance or illumination or Degree or Illumination: When the light falls on surface it is

illumination. The luminous flux received per unit.

6. Brightness: It is defined as the flux emitted per unit area or the luminous intensity per unity

projected area of the sources in a direction perpendicular to the surface. Brightness is a term

which may be applied either for emission of light directly from the source covering a large areasuch as an incandescent lamp in a globe or for an installation used for production of a certain

illumination on the object to be seen in which case actually the light reflected by the object

reaches our eyes such as the light from a cinema screen.

Design of lighting scheme: The lighting arrangement should be such as to provide sufficient

illumination, uniform distribution of light and avoid glare and shadow: for designing a lightingscheme the following factors should be taken into consideration:

i. Space light ratio: It is defined as the ratio of horizontal distance between lamps and the

mounting height of the lamps.

ii. Utilization factor: The total light flux radiated out by the source is not utilized on the working

planes.iii. Depreciation factor: When the lamps are covered with dust, dirt and smoke they do not

radiate out same amount of flux as when they do at the time of filling. Similarly after some timethe walls and surrounding at which lamps are fitted are covered with dirt and dust, so the do not

reflect the same amount of light as compared with the initial conditions. The depreciation factor

takes into account all such losses of flux.iv. Waste light factor: A surface when illuminated by number of lamps, there in certain amount

of wastage due to over - lapping of light ways.

Factory Lighting

The factory lighting should be such as to provide sufficient light without glare to the workmen. If

an adequate production, improve the quantity of the product and reduce the chances of accident.

It should be noticed that, it is economical to have white walls as the reflection from white color

is more when compared to any other color.

The light scheme should be such that in addition to providing requisite, number of lumens, there

should be an equal distribution. The fittings employed must be clean and in any case they should

not produce any glare. There is a chance that the glare might exist due to reflection of light fromany object other than reflectors; every care should be taken to eliminate such chance.

The lamps should be mounted at sufficient height to provide even luminous intensity.

Flood Lighting

It is employed for flooding any open large surface with light. High filament lamps, or discharge

lamps are employed for the purpose. It is normally used to enhance the beauty of an oldmonument, for advertisement and for illuminating sports stadium, railway yard, etc.


23/33

The projectors used for flood light are water tight, fitted with reflectors. The light emitted by the

lamp is projected in a narrow bean.

Electric lamps: For illumination, the following types of electric lamps are normally employed;

i.Incandescent lamp

ii. Arc lamp

iii. Electric discharge lamp.

Incandescent lamp

When an electric current is passed through a fine metallic wire, it raises temperature of the wire,and heat energy will be radiated at low temperature. At high temperatures heat as well as light

energy will be radiated, the higher the temperature of the wire, the higher the amount of light

energy radiated.

Utility or Demand meter (indicating Demand meter)

Maintenance and serving of the demand part of the meter is purely mechanical and should onlybe attempted after familiarization with the manufacture's instruction. The watt-hour element is

identical to meters without the demand feature and is tested and serviced in the same manner,

making sure that during calibration the demand device is operated so that the additional loadimposes by it is taken into account.

Reading of the energy meter

A practical way of reading the electrical, utility meters is demonstrated. In case of any suspicion

of faulty reading or operation, the engineering and maintenance department must be informed

immediately.

Some more definitions

Maintenance: Work undertaken in order to keep or restore every facility i.e. every part of a site,

building and equipment and contents to an acceptable standard.

Breakdown maintenance:-Work which is carried out after a failure, but for which advance

provision has been made, in the form of spares, materials labor and equipment.

Check: - To compare with an acceptable standard by suitable or defined means, whilst the

faultily is non-operational.

Downtime: - Period during which a facility is not ready for use.

Emergency maintenance: - Work necessitated by unforeseen breakdown or damage

Inspection: The process of ensuring by assessment that a facility reaches the necessary standard

of quality or performance and that the level is maintained.


24/33

Inventory: A list of all facilities, i.e. all parts of a site, building and contents, for purposes ofidentification.

Accidents involving electricity

During 2002, there were a total of 27 deaths involving electric current in the UK. Of these, 24

occurred in England and Wales,

2 in Scotland,

and 1 in Northern Ireland.The estimated number of accidental injuries caused by electricity in the home was as follows

Home accidents involving electric current 2002Age in years

Injuries 0-4 5-14 15-64 65-74 75+ UNKNOWN TotalReported* 14 18 99 3 1 1 136

Nationalestimate 287 369 2030 62 21 21 2,788

Articles reported in accidents involving electric shock include light fittings, toasters, hair dryers,

electric sockets and plugs, extension leads and cables, strimmers and lawnmowers, washing

machines and dishwashers.

Work Injuries

In Great Britain, work injury statistics are compiled from reports made to HSE and localauthorities under the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations

1995 (RIDDOR 95) which came into force on April 1st 1996.

Any accidental injury which involves a fatality, a major injury or one which results in more than

three days away from normal duties must be reported under the regulations. Included under the

heading of reportable major injuries are those resulting from electric shock or electrical burnleading to unconsciousness or requiring resuscitation or admittance to hospital for more than 24

hours.

Reported workplace injuries involving electricity during the period April 2002- April 2003

(provisional) were:

Reported workplace injuries involving electricity during the period April

2002- April 2003 (provisional) were: Contact with electricity or electrical

discharge

Fatal Major Injury Over 3 day


25/33

Employees 12 124 441

Self employed 3 10 8

Dangerous occurrences

If something happens which does not result in a reportable injury, but which clearly could have

done, then it may be classified as a dangerous occurrence which must also be reported.Dangerous occurrences involving electricity in 2002/2003 were:

Plant or equipment either comes into contact with overhead electric line in which voltage

exceeds 200 volts or causes an electrical discharge - 188

Electrical short circuit which results in stoppage of the plant for more than 24 hours - 287

Home Safety

Every year in the UK almost 4,000 people die in accidents in the home and 2.7 million turn up ataccident and emergency departments seeking treatment. But, because the accidents happen

behind closed doors in isolated incidents they rarely attract public and media attention.

There is the need of campaign for change and provide a large range of resources to inform,

educate and help to prevent accidents in the home and garden.

Electrical FAQs

Which is safer, Alternating Current (AC), or Direct Current (DC)?

Everyone gets a belt from electricity every now and then, dont they?

How do I know if my electrical equipment is safe?

How do I know if my electrical installation is safe?

How do I know if someone is competent to do electrical work?

Can I do my own electrical work?

When should I use a residual current device (RCD)?

How often should I test my electrical equipment?

How often should I get my electrical installation tested?

Who should I talk to about electrical safety?

When should I report an accident to HSE?

What should I do if I think someone is working unsafely?

What should I do to avoid danger from underground cables or wires?

How do I work safely near overhead lines?

What should I do if I touch an overhead power line?
http://www.hse.gov.uk/electricity/faq.htm#acdchttp://www.hse.gov.uk/electricity/faq.htm#acdchttp://www.hse.gov.uk/electricity/faq.htm#a1http://www.hse.gov.uk/electricity/faq.htm#a1http://www.hse.gov.uk/electricity/faq.htm#a1http://www.hse.gov.uk/electricity/faq.htm#a1http://www.hse.gov.uk/electricity/faq.htm#a1http://www.hse.gov.uk/electricity/faq.htm#a1http://www.hse.gov.uk/electricity/faq.htm#a2http://www.hse.gov.uk/electricity/faq.htm#a3http://www.hse.gov.uk/electricity/faq.htm#a3http://www.hse.gov.uk/electricity/faq.htm#a4http://www.hse.gov.uk/electricity/faq.htm#a4http://www.hse.gov.uk/electricity/faq.htm#a5http://www.hse.gov.uk/electricity/faq.htm#a5http://www.hse.gov.uk/electricity/faq.htm#a6http://www.hse.gov.uk/electricity/faq.htm#a6http://www.hse.gov.uk/electricity/faq.htm#a7http://www.hse.gov.uk/electricity/faq.htm#a7http://www.hse.gov.uk/electricity/faq.htm#a8http://www.hse.gov.uk/electricity/faq.htm#a8http://www.hse.gov.uk/electricity/faq.htm#a9http://www.hse.gov.uk/electricity/faq.htm#a10http://www.hse.gov.uk/electricity/faq.htm#a11http://www.hse.gov.uk/electricity/faq.htm#a11http://www.hse.gov.uk/electricity/underground.htmhttp://www.hse.gov.uk/electricity/underground.htmhttp://www.hse.gov.uk/electricity/faq.htm#a13http://www.hse.gov.uk/electricity/faq.htm#a13http://www.hse.gov.uk/electricity/faq.htm#a14http://www.hse.gov.uk/electricity/faq.htm#a14http://www.hse.gov.uk/electricity/faq.htm#a14http://www.hse.gov.uk/electricity/faq.htm#a13http://www.hse.gov.uk/electricity/underground.htmhttp://www.hse.gov.uk/electricity/faq.htm#a11http://www.hse.gov.uk/electricity/faq.htm#a10http://www.hse.gov.uk/electricity/faq.htm#a9http://www.hse.gov.uk/electricity/faq.htm#a8http://www.hse.gov.uk/electricity/faq.htm#a7http://www.hse.gov.uk/electricity/faq.htm#a6http://www.hse.gov.uk/electricity/faq.htm#a5http://www.hse.gov.uk/electricity/faq.htm#a4http://www.hse.gov.uk/electricity/faq.htm#a3http://www.hse.gov.uk/electricity/faq.htm#a2http://www.hse.gov.uk/electricity/faq.htm#a1http://www.hse.gov.uk/electricity/faq.htm#acdc


26/33

What voltages are dangerous?

When is it safe to work on live electrical equipment?

How do I make my electrical equipment safe to work on?

Who has the responsibility to make sure everyone works safely?

What should I do if I think I have seen an unsafe electrical installation or equipment?

Much of the information on these web pages has been summarized to make it suitable for a wideaudience. You should always use thepublished guidance listed on the resources pagewhen

deciding how to work safely and meet the requirements of the law.

Which is safer, Alternating Current (AC), or Direct Current (DC)?

Alternating Current (AC) and Direct Current (DC) have slightly different effects on the human

body, but both are dangerous above a certain voltage. The risk of injury changes according to the

frequency of the AC, and it is common for DC to have an AC component (called ripple).

Someone with special equipment can measure this, but the effect on a particular person is very

difficult to predict as it depends upon a large number of factors. As a consequence you should

always avoid contact with high voltage electrical conductors, regardless of the type of electricalcurrent they are carrying.

More detailed technical information on electrical injury is given in the standard BS PD 6519

"Guide to the effects of current on human beings and livestock - Part 1: General aspects.

Everyone gets a belt from electricity every now and then, dont they?

No, not if they are careful and follow the simple rules to securely isolate electrical equipment,

and check it is dead before they start work. If you have received an electric shock but were not

injured, then you are lucky. Next time a slight change in events may lead to a very different

result. No one is immune to an injury from electricity.

How do I know if my electrical equipment is safe?

You can find out if your electrical equipment is safe by carrying out suitable checks, such as

inspection and/or testing. The level of inspection and/or testing should depend upon the risks. A

simple visual inspectionis likely to be sufficient for equipment used in a clean dry environment.

In addition, equipment that is more likely to become damaged or is operated in a harsh

environment is likely to require more demanding electrical tests.

Checks should be carried out often enough that there is little chance the equipment will become

unsafe before the next check. It is good practice to make a decision on how often each piece of

equipment should be checked, write down the decision, make sure the check is carried out, and

write down the results. You should change how often you carry out checks according to thenumber and severity of faults found.

The best way to find out if specialized equipment is safe, is to have it inspected and tested by a

person with specific competence on the type of equipment. This may be the original

manufacturer or his authorized service and repair agent. A reputable servicing company that

deals with the type of equipment should also be competent to check its safety.
http://www.hse.gov.uk/electricity/faq.htm#a15http://www.hse.gov.uk/electricity/faq.htm#a16http://www.hse.gov.uk/electricity/faq.htm#a16http://www.hse.gov.uk/electricity/faq.htm#a17http://www.hse.gov.uk/electricity/faq.htm#a17http://www.hse.gov.uk/electricity/faq.htm#a18http://www.hse.gov.uk/electricity/faq.htm#a18http://www.hse.gov.uk/electricity/faq.htm#a19http://www.hse.gov.uk/electricity/information.htmhttp://www.hse.gov.uk/electricity/information.htmhttp://www.hse.gov.uk/electricity/information.htmhttp://www.hse.gov.uk/electricity/electricequip.htm#conditionhttp://www.hse.gov.uk/electricity/electricequip.htm#conditionhttp://www.hse.gov.uk/electricity/electricequip.htm#conditionhttp://www.hse.gov.uk/electricity/information.htmhttp://www.hse.gov.uk/electricity/faq.htm#a19http://www.hse.gov.uk/electricity/faq.htm#a18http://www.hse.gov.uk/electricity/faq.htm#a17http://www.hse.gov.uk/electricity/faq.htm#a16http://www.hse.gov.uk/electricity/faq.htm#a15


27/33

How do I know if my electrical installation is safe?

The best way to find out if your electrical installation is safe is to have it inspected and tested by

a person who has the competence to do so, such as anElectrical Contractors Association (ECA)

It is possible to do simple checks on your installation using an electrical socket tester. This is a

device that can be plugged into a socket outlet, and can identify if there is a wiring fault.However, be aware that many types of socket tester cannot detect certain types of fault, and

could indicate the socket is safe when it is not. Read the information provided by onElectricalSocket Testers

How do I know if someone is competent to do electrical work?

A person can demonstrate competence to perform electrical work if he or she has successfully

completed an assessed training course that has included the type of work being considered, run

by an accredited training organization, and has been able to demonstrate an ability to understand

electrical theory and put this into practice.

A successfully completed electrical apprenticeship, with some post apprenticeship experience is

a good way of demonstrating competence for general electrical work. More specialized work

such as maintenance of high voltage switchgear or control system modification is almost

certainly likely to require additional training and experience.

Can I do my own electrical work?

You can do your own electrical work if you are competent to do so. Simple tasks such as wiring

a plug are within the grasp of many people, but more complex tasks such as modifying an

electrical installation may not be.

It is particularly important that anyone who undertakes electrical work is able to satisfy the

requirements of the Health and Safety at Work etc Act 1974 and the Electricity at Work

Regulations 1989.

For work on electrical installations below 1000 volts ac you should be able to work within the

guidelines set out in BS7671 Requirements for electrical installations. IEE Wiring Regulations.

Seventeenth edition. Other work should be carried out according to the guidelines set out in the

relevant industry standard.

Those who wish to undertake electrical testing work would normally be expected to have more

knowledge and to be able to demonstrate competence through the successful completion of asuitable training course.

More complex electrical tasks such as motor repair or maintenance of radio frequency heating

equipment should only be carried out by someone who has been trained to do them.
http://www.eca.co.uk/http://www.eca.co.uk/http://www.eca.co.uk/http://www.hse.gov.uk/electricity/socket1.htmhttp://www.hse.gov.uk/electricity/socket1.htmhttp://www.hse.gov.uk/electricity/socket1.htmhttp://www.hse.gov.uk/electricity/socket1.htmhttp://www.hse.gov.uk/electricity/socket1.htmhttp://www.hse.gov.uk/electricity/socket1.htmhttp://www.eca.co.uk/


28/33

When should I use a residual current device?

It is advisable to use a residual current device (RCD) whenever possible but particularly in wet

or damp locations such as outdoors. An RCD rated at no more than 30mA limits the energy in a

particular type of electric shock and can save your life. However, an RCD cannot protect you

from every type of electric shock, so you should still make sure that circuits are securely isolated

before you work on them.

It is best to use an RCD that is incorporated into the switchboard of your installation. This means

that all circuits fed from that RCD are protected by the RCD. An RCD that is incorporated into

an ordinary mains socket, or plugged into it, will protect anything that is attached to that socket,

but it is possible that equipment may be plugged into another, unprotected, socket.

RCDs should be regularly tested by pressing the test button, and by making sure that the RCD

trips. Faulty or inoperative RCDs should be removed from use.

RCDs rated above 30mA provide very limited protection against harm from an electric shock.

If you are using electrical equipment in particularly harsh conditions it is worthselecting lower

voltage equipmentpowered by a transformer with an output centre tapped to earth, or powered

by a battery. Additional precautions may also be required depending on the specific location,

BS7671:2001 Requirements for electrical installations, IEE Wiring Regulations, Seventeenth

edition, Section 7, offers guidance on this.

How often should I test my electrical equipment?

'Electrical equipment should bevisually checked to spot early signs of damage or deterioration.

Equipment should be more thoroughly tested by a competent person often enough that there is

little chance that the equipment will become dangerous between tests. Equipment that is used ina harsh environment should be tested more frequently than equipment that is less likely to

become damaged or unsafe.

It is good practice to assess how often equipment being used for work purposes should be tested,

write down your findings, make sure the testing is carried out, and write down the results of the

tests.

How often should I get my electrical installation tested?

Electrical installations should be tested often enough that there is little chance of deterioration

leading to danger. Any part of an installation that has become obviously defective between tests

should be de-energized until the fault can be fixed.

You should have your electrical installation inspected and tested by a person who has the

competence to do so, such as an approved electrical contractor. It is possible to do simple checks

on your installation using an electrical socket tester. This is a device that can be plugged into a

socket outlet, and can identify if there is a wiring fault. However, be aware that many types of

socket tester cannot detect certain types of fault, and could indicate the socket is safe when it is

not.
http://www.hse.gov.uk/electricity/electricequip.htm#suitablehttp://www.hse.gov.uk/electricity/electricequip.htm#suitablehttp://www.hse.gov.uk/electricity/electricequip.htm#suitablehttp://www.hse.gov.uk/electricity/electricequip.htm#suitablehttp://www.hse.gov.uk/electricity/electricequip.htm#conditionhttp://www.hse.gov.uk/electricity/electricequip.htm#conditionhttp://www.hse.gov.uk/electricity/electricequip.htm#conditionhttp://www.hse.gov.uk/electricity/electricequip.htm#conditionhttp://www.hse.gov.uk/electricity/electricequip.htm#suitablehttp://www.hse.gov.uk/electricity/electricequip.htm#suitable


29/33

Who should I talk to about electrical safety?

In the first instance a competent electrical contractor should be able to give advice on electrical

safety, and should also be able to direct you to a suitable electrical engineer for advice about

specialist areas.

When should I report an electrical accident ?You should report any work related accident that comes under the requirements of the Reporting

of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR) 1995.

In general, an electrical accident is reportable if:

the person dies as a result of their injuries, OR

the person suffers a major injury, OR

as a result of the injury the person is away from work for more than 3 days, or cannot

undertake their full range of normal duties for more than 3 days, OR

a person receives an electric shock or burn where the person loses consciousness, or requires

resuscitation, or admission to hospital for more than 24 hours, OR

plant or equipment came into contact with overhead power lines, OR

there is an electrical short circuit or overload that causes a fire or explosion.

What should I do if I think someone is working unsafely?

If you think someone is working unsafely you should ask him or her to stop immediately and tell

a manager. If you are still unhappy about how someone is working, you should notify

appropriate authority.

How do I work safely near overhead lines?

It can be difficult toidentify the voltage of overhead linesso you should always assume

overhead lines are dangerous when planning work near them. You can download a free leaflet

What should I do if I touch an overhead power line?

The free leaflet on equipment describes what you should do if you, or another person touches an

overhead power line. Your local electricity distribution company can generally supply stickers

describing emergency procedures and containing contact numbers that can be stuck in the cabs of

vehicles likely to be used near overhead power lines.

What voltages are dangerous?

A wide range of voltages can be dangerous for different reasons. A very low voltage (such asthat produced by a single torch battery) can produce a spark powerful enough to ignite an

explosive atmosphere. Batteries (such as those in motor vehicles) can also overheat or explode if

they are shorted.

If a person comes into contact with a voltage above about 50 volts, they can receive a range of

injuries including those directly resulting from the electrical shock (stopped breathing, heart,

etc), and indirect effects resulting from loss of control (such as falling from a height or coming
http://www.hse.gov.uk/electricity/nearelectric.htm#overheadhttp://www.hse.gov.uk/electricity/nearelectric.htm#overheadhttp://www.hse.gov.uk/electricity/nearelectric.htm#overheadhttp://www.hse.gov.uk/electricity/nearelectric.htm#overhead


30/33

into contact with moving machinery). The chance of being injured by an electric shock increases

where it is damp or where there is a lot of metalwork.

When is it safe to work on live electrical equipment?

It is never absolutely safe to work on live electrical equipment. There are few circumstances

where it is necessary to work live, and this must only be done after it has been determined that itis unreasonable for the work to be done dead. Even if working live can be justified, many

precautions are needed to make sure that the risk is reduced so far as is reasonably practicable.

How do I make my electrical equipment safe to work on?

You can be reasonably sure that your electrical equipment is safe to work on if all sources of

energy (electrical, mechanical, gas, pneumatic, hydraulic, pressure etc) have been securely

isolated and any stored energy has been released from the equipment. You should always follow

the procedure for doing this described in the instructions provided by the manufacturer of the

equipment, and any local safety rules. If you cannot find the instructions, contact the

manufacturer and get them to send you instructions before you start work.

Equipment containing dangerous chemicals or other substances may have to be decontaminated

before it is safe to work on. You should ask a competent person what to do.

It is important that there is no chance that a source of energy can be deliberately or inadvertently

re-connected to the equipment whilst it is being worked on. This can be achieved by applying a

lock to each isolation device, and the person doing the maintenance should have all the keys to

these locks in his or her possession. Warning notices should be posted at the points of isolation.

If work is to be carried out on, or near, exposed conductors, the conductors should be proven

dead, using appropriate test equipment, before work commences.

Who has the responsibility to make sure everyone works safely?

It is the responsibility of everyone to make sure that work is safely undertaken. Managers have a

responsibility to provide the resources, instruction and training necessary to enable their workers

to work safely and so that others are not endangered by the work activity. Workers have a

responsibility to make sure they keep themselves, and others safe.

What should I do if I think I have seen an unsafe electrical installation or equipment?

If you think you have an unsafe electrical installation you should first warn everyone to stay

away from it, and, if it is safe to do so, switch it off. You should then contact a competent person

such as an approved electrical contractor who will be able to advise you how to make your

installation safe.

If the installation you think is unsafe is not owned by you or under your control, you should

attempt to find out who does own it, and contact them. Electrical distribution poles, pylons and

equipment should have a contact telephone number attached to them .


31/33

I. (a) Explain maintenance and state two reasons why it is important in the Hotel Catering and

Institutio~al Management course.

(b )Define the following;

1. Electrons

v!. Energy

(':) (i) A )!()lJng woman purchased at220 volts-in electric heater for use in her office. The heateris rated at 600 watts. How much current will the

(i i) If the power (P) rating of the heater is 600 watts, what will be the energy consumed if it is

used continuously for 3hours?

2. (a) State Ohm's law and give its mathematical representation. 37

(b) Give the symbols for the following components 111 an electrical

system;(i) Diode

(i i) Wattmeter

(i i i) Voltage

(iv) Motor(v) Gal vanometer

(c) Define Engineering and

programmes available.

(d) Define the following;

(vi) Transformer (vii) Battery (viii) Cell

(ix) Earthing

(x) Filament lamp

gIve five examples of engmeenng

(i) Conductor(ii) Insulator

(iii) Fuse

(iv) Load(v) Source

3. Explain the following;


32/33

(i) Reflecting surface

(ii) Diffusing surface

(a) State four requirements of a circuit breaker. (b) Give two sources of lighting available

(c) Enumerate five electrical appliances available in your home. (d) Out! ine lour energy

conservation opportunities available.

4. (a) Indicate the SI unit of each of the following quantities

(i) Current

(ii) Voltage

(iii) Power

(iv) Energy resistance

(b) (i) State one objective of forming and operating an industry. (ii) How would maintenance

affect tile" above objective?

5. Outline four applications of the heating effect of an electric current.

6. Give the five lighting schemes available.

a) Deline engineering and give three examples of engineering programme available.

b) Explain maintenance and state two importance of maintenance III our institutions.

c) Enulllcrate ten electrical appliances available in your institution.

a) Define the following as may be applied electrical eng1l1eenng;

i) Electricity

i i) Electric current

i i i) Electromotive force

iv) Resistancev) Power

vi) Energy

vii) Sourceviii) Load

ix) l' use


33/33

x) A tom

b) Define the following and give five examples of each.

i) Conductor

ii) Insulator

c) i) A man purchased a 120 volt plug-in electric space heater for use in his home. If it is rated at400 watts, how much current will the heater draw? ii)If the power rating of the heater in (i)

above is 400 watts, what will be the energy consumed in three hours of use?

a) give the symbols for the following components an electrical system;

1. filament Lamp

11. capacitor

HI. earthIV. battery

v. cell

VI. windings.. inductor and coil

VII.

Vlll. transformer

IX. wattmeterx. ammeter

a) i) State four requirements of a good circuit breaker. ii) Briefly explain one way to maintain a

fuse.

b) Give two sources of light available

c) Define the following;

i) Reflecting surface

ii) Diffusing surface

d) Give five lighting schemes available for use in our institutions.

engineering & maintenance notes

Documents