Wednesday, April 23, 2014

Electric work 02 -Electrical cables and fittings

Electrical cables 

Electrical cables are used to transmit electricity, and they are made up of two or more wires bonded together (through twisting or braiding). These wires are covered by protective and insulating material. There are many different types of electrical cables, and they are typically categorized depending on such factors as electrical conductivity, type of insulation, type of protector (or covering), weight, cost, and specific uses.

Other factors that determine the type of electrical cables include voltage rating, type of protective covering, fiber core size, cable weight and cable diameter.

A cable is an assembly of one or more conductors (wires) with some flexibility.
A lead is a complete assembly of cable and connectors.
A wire is a single conductor which may have an outer layer of insulation (usually plastic).

Types of cables

Single and multi-strand conductors

Solid wire, also called solid-core or single-strand wire, consists of one piece of metal wire. 

        Multi-strand wire                                                                Single –strand wire

Stranded wire or multi strand conductor is composed of a bundle wires to make a larger conductor.
Stranded wire is more flexible than solid wire of the same total cross-sectional area. Solid wire is cheaper to manufacture than stranded wire and is used where there is little need for flexibility in the wire. Solid wire also provides mechanical ruggedness; and because it has relatively less surface area which is exposed to attack by corrosives, protection against the environment. 
Stranded wire is used when higher resistance to metal fatigue is required. Such situations include connections between circuit boards in multi-printed-circuit-board devices, where the rigidity of solid wire would produce too much stress as a result of movement during assembly or servicing; A.C. line cords for appliances; musical instrument cables; computer mouse cables; welding electrode cables; control cables connecting moving machine parts; mining machine cables; trailing machine cables; and numerous others.

Single-cored and multi-cored cables

Single core

Single core cable is mostly used for industrial applications where it is run in conduits. In domestic wiring it is usually only used for certain situations such as for electric fittings. 

Multi Core

Colours used for the cable insulation 

Electrical wires have markings stamped or printed on the outside sheath of the cable. These markings tell what type and size of wire that you have. And also the color of the wires inside of the sheath reveals that different color wires serve different purposes.

Protective earth (PE)
Green/yellow bi-colour
Neutral (N)
Single phase: Live (L)
Three phase: L1
Three phase: L2
Three phase: L3

Flexible cables colour code
No. of cores
2 core
Brown , Blue
3 core
Brown , Blue , Green and yellow
4 core
Brown , Blue , Green and yellow , Black or grey
5 core
Brown , Blue , Green and yellow , Black or grey , Black or grey

Basic types of electrical accessories used for domestic single phase circuits.

Mounting Box

Mounting boxes protect connections between two or more wires or between wires and switches or fixtures. Mounting boxes are available with different sizes and made of different materials such as ABS, plastic , PVC and etc…


An electrical switch controls the flow of power in an electrical circuit. It provides an open circuit in the off position and acts as a closed circuit in the on position.

Types of switches

Single Pole Switches
This is the simplest type of switch. Most residential switches are single pole switches.

Single pole switch with neon indicator

Single pole switch without neon indicator

·       Double Pole Switches


These types of switches are often used to switch mains electricity because it can isolate both the live and neutral connections at once.

Socket outlet

Socket outlets are used when temporary electrical connections are required. eg : for connecting table lamp , table fan , radio ,etc……There are two types of socket outlets available in the market.
       I.            Two pin type (live, neutral)
    II.            Three pin type ( live , neutral and earth)

As all appliances connected by flexible leads should be earthed, two pin type is outdated today. The 3 pin type is standardized for domestic wiring and use at 2,5,13 and 15 A rating.

Ceiling rose

Ceiling rose is used to connect pendant lamps, ceiling fans and etc… to the supply system. Ceiling rose consist of two main parts called base and cover. Both the parts are made up of Bakelite or porcelain. Terminals are provided on the base and a hole is made in the cover to take out the flexible wire.


Junction box

Junction boxes are used in electrical installation to join some conductor and provide different paths for different conductors. Most of the junction boxes are made of plastic.

Cable clips

Cable clips are used to attach electrical cables to a wall or baseboard. Based on the cables that are used, suitable type of cable clips should be selected.




Sunday, April 13, 2014

Electric work01 -Hand Tools

          Hand tools are the tools which are used by human in a workshop for various electrical installation related works and also for various maintenance works.

Types of hand tools

1. Screw driver
A hand tool used to fix and remove screws. Used in assembling work and maintenance work. Available in three main types:

a) Flat type – Point of the screw driver is flat shape used for straight slot screws.
b) Pozidriv type (Philips type) - Point of the screw driver is special shape (x shape) to match with             the slot in pozidriv slot screw. Used for Pozidriv slot screws.
c) Offset screw driver – Designed for use in confined areas where it is impossible to use a standard         screw driver.

2. Pliers
A hand tool, used to hold smaller components for various activities such filing, drilling etc. We can cut wires pulled out tighten small components by using pliers.

3. Hammer
A hand tool used for delivering blows (force) in chipping using chisel, bending, straightening and other operations. Hammers are forged from high carbon steel. Hammer sizes are specified by their weight. Main types of hammers are:

a) Ball pein hammer – Most commonly used hammer. Consists of flat face for general work and ball         pein for peining or riveting.
b) Cross pein hammer – Used for sheet metal forming
c) Straight pein hammer – Used for sheet metal work

4. Tape measure
 A tape measure is a portable measurement device used to quantify the size of an object or the distance between objects. The tape is marked along the tape edge in inches and fractional inches, typically in quarter-, eight-, and sixteenth-inch increments. Some tape measures are marked in millimeters, centimeters, and meters on one edge.
The most common tape measures are 12 feet, 25 feet, or 100 feet in length.

Portable power tools suitable for drilling walls

Hand drilling machine
 Manually hand operated drilling machine. Used for rough and smaller diameter hole drilling.(Up to about 5mm dia.) Mostly used to drill soft materials.

Portable electric Drilling machine 
 Electrically operated hand drill. Used for rough and small diameter hole drilling (up to about 18mm dia.)Spindle is driven by the electric motor and feeding of drill is done by human hand. Can drill metals also.

Hammer drill
 A hammer drill has a specially designed clutch that allows it to not only spin the drill bit, but also to punch it in and out (along the axis of the bit). Hammer drills are more expensive and more bulky than regular drills, but are preferable for applications where the material to be drilled—concrete block or wood studs—is unknown. For example, an electrician would use a hammer drill for attaching items (such as an electrical box) to either wood studs (if used as a conventional power drill) or masonry walls (if used as a hammer drill).

Drill bit
The cutting tool used on a drilling machine is known as a Drill bit ( Drill). The most common type of drill is Twist Drill.
Twist drill
Twist drill is consists of 2 main parts:
i) Body – A cylindrical part make with 2 helical flutes to provide the cutting lips and cutting point to remove the chips. To  reduce the friction of the body and the point against the walls of the hole and for better guiding of the tool, only a part of the cylindrical surface is left project and form what are called the lands.
ii) Shank – The part of the drill which to the machine. Depend on the method of applied to securing the drill, the shank available as
a) Straight or Cylindrical type – Available as drills which are less than 12.7mm in diameter. When fixing the straight shank drills to a drilling machine a Drill chuck or a Collet chuck is used.
b) Taper Shank – Consists of standard Morse taper shank. Available as drills which are more than 12.7mm in diameter. When fixing the taper shank drills to a drilling machine the Morse tapered spindle hole or Morse tapered sleeve is used.

Types of twist drill

General purpose drill – a drill with standard helix angle or Rake angle of 60°. Used to drill mild steel, cooper alloy etc.
Slow helix drill – A drill with larger helix angle , Used to drill hard materials
Quick helix angle - A drill with smaller helix angle , Used to drill  soft materials
Straight flute drill – Flute which take straight shape. Used to drill very soft material
Flat drill – A drill without a point. Used to drill sheet metal

Monday, April 7, 2014

Plumbing work02 -Basic Types of Pipe and Fittings

                  Pipes are used in water supply systems to deliver water from one place to another. Water flaws through pipes by:
Gravity or
Force pumping

For efficiency, pipes must deliver water with least friction. For this reason pipes are usually circular and the inner surface is made smooth. Man has used many materials for the manufacture of pipes. In the first instance bamboo trunks were used as pipes by boring through the nodes. Then pipes were made by twisting lead sheet around circular timber. Later hot drawn, cold drawn or seam welded pipes were manufactured from metals like copper, steel, stainless steel, aluminum and brass etc. In large water supply installations pipes made out of:-
Cast iron
Black iron
Asbestos were used.

A major disadvantage of these pipes was that they are heavy and joining was complicated. During World War 2 the necessity for a more flexible and convenient pipe type was felt and the result was the synthetic polymer pipe.

Polymer Pipes - The advantages of polymer pipes are:
a) Easily moulded to any shape or size
b) Easy to work with and are light weight
c) High resistance to weathering and corrosion
d) Almost maintenance free
e) Good electrical, sound and heat insulation
f) Withstand moisture, oils and acids.

Plastics (polymers) are mainly divided into 02 groups:-

Thermoplastics - which become soft on heating and returning back to its original form on cooling

Thermosetting plastics - which undergo chemical changes on heating and do not return to original form on cooling

Polymer (plastic) pipes are a petroleum bi-product. Two main plastics are used in the manufacture of pipes namely:-
PVC (Poly Vinyl Chloride)
HDPE (High Density Polyethylene)

PVC is identified as a rigid pipe while HDPE is identified as a flexible pipe. Polymer pipes are manufactured by extrusion or moulding.

Pipe Fittings
Pipes cannot always be installed as straight runs. They need to:-
a) Change direction
b) Branch off
c) Reduce or enlarge in size
d) Connect to appliances

These need special pipe components which are named pipe fittings. There are various pipe fittings used for the different requirements and locations:
Bends (90˚ or oblique), Elbows, Reducers, Tees (equal/unequal), Sockets (Plain/valve/faucet), Union couplings


Union coupling                                               Elbow 

Tee                                                                  Bend

‘Y’ junction

Valves and Taps (or faucets)
Valves and taps (faucets) are required in pipe systems to control flow. Flow control includes - Increase flow, Decrease flow, Stop flow or Open flow.

      Different types of valves are used.

Gate Valve                                                                          Bib Tap


Working mechanism – Bib tap                                                                      Globe valve


Working mechanism – Globe valve                       Working mechanism – Gate valve

Sunday, April 6, 2014

Plumbing works 01-basic and power tools

The delivery of liquids from one place to another is most easily done through pipe lines. In cities or towns the water is supplied and the waste water is disposed through networks of pipes. In many industries various types of chemicals and liquids are conveyed through pipes. Thus pipe work plays an important role in the development process.

This makes the cutting and joining pipes through the use of appropriate special fittings a very important profession. A person engaged in this profession is called a plumber and the plumber requires a special set of tools to do his work properly.

The major tools used in plumbing work are as follows:
Used for cutting pipes. It consists of a frame, handle, prongs, tightening screws and nut. The blade is fixed in position and tightened by means of the tightening screw.
Hacksaw blades should be selected with due consideration to the material to be cut. The No. of teeth per cm, type of steel in the blade are the considerations to be given.

Hammers are required in plumbing for use with tools like chisels, for nailing, riveting and for driving objects into position.
Different types of hammers are used for different types of work.
Claw hammers – for driving and removing nails.
Ball Pein hammers – for driving objects and for riveting.
Cross Pein hammers – For sheet metal work.

Tape measure
Consists of a graduated thin steel tape coiled and spring loaded in a box. A lever operated button automatically retracts the extended tape after measuring. The tape is graduated in cm and inches.
Mostly used tool for measuring in engineering work.
Spirit Level
Used to check true alignment to level (horizontal) and plumb (vertical).

Spirit levels come in various sizes ranging from 150mm to 1200mm.

Aavailable in wood or metal, the metal ones are easier to keep clean as they are easy to wash to remove mortar.

Pipe Reamers.
For steel pipe. Pipe Reamers are used to de-burr steel pipe before threading. The reamer cone is made from tool steel and hardened for maximum life. Unique cutting edge makes this spiral pipe reamer self-feeding and easy to start and operate.

For PVC pipe - Designed to chamfer pipe edges before joining, clean out the old or broken pipe and leftover solvent cement from a fitting so the fitting can be reused. Plastic Pipe Fitting Reamers are available in 4 sizes and fit into standard ½” drills.

A spanner or wrench is a tool used to provide grip and mechanical advantage in applying torque to turn objects—usually rotary fasteners, such as nuts and bolts.

Portable heating equipment
When working with plastic pipes, portable heating equipment are needed to heat the pipes for bending and jointing.
A blow lamp or a blowtorch is a tool for applying heat for various applications.
Earlier the fuel in the blow lamp was pressurized by a syringe or a pump. Present-day the pressurized gas containers have replaced the built-in and often dangerous pump.
Present day the blowtorch is referred to in industry and trade as per the fuel consumed by the tool:
·         Gas: Propane , butane or LPG
·         Liquid fuel – kerosene, gasoline, diesel or biodiesel

Pipe benders
Steel, aluminium, copper or most metal pipes can be bent using the manual pipe bender. It allows users to create sections of piping at the exact angle needed for a particular application.

The pipe is bent by the force exerted by the user onto the small handle of the device.

Pipe bender springs
Pipes are also bent by the use of springs. Springs can be either external or internal, i.e. the spring can be inserted into the pipe or the pipe can be inserted into the spring. The presence of the spring prevents wrinkles when bending.

Power tools are those powered by:
1.      An electric motor
2.      Internal combustion engine
3.      Steam engine
4.      Compressed air or
5.      Natural power sources like wind or moving water.

While power tools can be either stationery or portable, the scope of this lesson is limited to portable power tools only. Power tools are used for driving, drilling, cutting, shaping, sanding, grinding, polishing, painting and heating. Common portable power tools include the drill, hand saws, sanders, grinders and planers etc.

Power drill
Just like the hand drill a power drill too has a chuck to fix the cutting tool or the drill bit, but rotating of the drill is powered. The on/off switch is located on the hand grip enabling emergency stoppages. To drill a hole the cutting tip of the drill bit fixed to the drill chuck is pressed against the target material and rotated by power.  Power drills can be used not only to drill holes, but also to drive or remove screws, countersinking, grinding, brushing and buffing etc.
For drilling into concrete or masonry some drills have a percussion effect in addition to rotation. These are called hammer drills.
For electrical safety it is advisable to use portable power tools rated at low voltages e.g. 110V. Since the supply voltage is 230V a step down transformer has to be connected to the power tool. A better solution to achieve electrical safety is to use battery operated drills. These are usually rechargeable and extremely safe.
Electric drills should be well maintained by:
1.      Cleaning after use
2.      Checking power cable for damages and prompt replacing
3.      Checking electrical contacts regularly
4.      Not allowing the tool to come into contact with water or liquids
5.      Using on regular steady power supply
6.      Proper storage after retracting or rewinding the power cable

Battery operated rechargeable drill

Twist drill bits
Twist drill bits get their name from the twisted pattern of grooves on the bit. Commonly used for drilling wood, plastic or metal. Twist drill bits typically range in size from 1/16 of an inch to 1 inch in diameter (or even larger in commercial applications). Twist drill bits are used at high speed for woodworking, but are turned much more slowly when drilling in metal to keep them from heating excessively.

1.      Bit Shank - The plain stem of the bit with no grooves is the shank which locks into the drill chuck.

Point - The point of a twist drill bit is ground to form two chisel-like cutting edges extending out from the point at the center of the tip. For wood cutting bits, the point is usually at a steeper angle than on metal cutting bits. This allows the bit to cut more aggressively through the wood.

Flutes - Deeply cut grooves that spiral upwards from the tip are flutes. The function of the flutes is to take the cut material out of the bore hole. Without the flutes, the drill bit will get stuck since it cannot eject the cut material.

Masonry drill Bits
Masonry drill bits are a variation of the twist drill bit. The shank is made out of soft steel and the cutting tip has an insert of tungsten carbide brazed into it. Tungsten carbide is an extremely hard substance which can cut through concrete etc.
Hammer drills are mostly used for masonry drilling and the drill bit is both rotated and hammered into the concrete or masonry. The hammer breaks the masonry and the rotating flutes bring out the dust. Masonry drill bits are available from 5mm to 40mm.

Twitter Delicious Facebook Digg Stumbleupon Favorites More