From time immoral the human efforts have always been aimed at utilizing all available resources to de more and more work. Man invented a number of machines to convert the energy available form natural resources into mechanical work for useful purpose. Energy available in nature can be form a large of source the major ones being as under:-
1. FUEL
Among all the source the burning of fuel is the most important source of energy. Heat energy liberated in this case may be converted into mechanical work by heat engines
2. FLOW OF RIVER WATER
When a river flows from a suitable height the potential energy of the river want may be utilized for power generation by means of water turbines
3. ATOM
Atomic power is a new source of energy produced by the fission or fusion of atoms is converted into mechanical work by heat engines.
4. WIND
For many years windmills were built to utilize the power from the wind but still their applications are not very successful. It is for the fact that suitable wind velocities are available only for the part of a year. The wind power is utilized with the help of a wind turbine placed over a suitable steel tower.
5. SEA
There is a change in level of water in the sea between the high and low tides. Water may be stored during the high tides and it may be discharged during low tides through water turbines for power generation. But this type of plant is not yet built due to various difficulties though there are certain possibilities to have from it.
6. SUN
A steam engine consists of a steam generating unit a boiler in which the steam is generated a prime mover in which the energy of steam is converted into mechanical work and a condenser in which the steam is condensed. Prime movers using steam may be classified as reciprocating steam engine and steam turbine. The reciprocating steam engine is a form of heat engine in which the work is done by the ores sure of steam acting on a moving piston. Although it was used as a prime mover successfully for many years it is now replaced by the steam turbine for large powers.
CLASSIFICATION
A reciprocating steam engine engine may be classified as follows
1. Single and double acting :When the steam acts on one side of the piston only it is called a single acting steam engine whereas in the case of a double acting steam engine the steam acts on both sides of the piston alternately.
2. Condensing and non condensing: The exhaust steam of a condensing steam is discharged and condensed into a chamber called condenser so the expansion of steam is carried on to pressure much below the atmospheric pressure/
3. Simple and compound :In a simple steam engine expansion of steam is done in a single cylinder but in compound steam engine total expansion of steam takes place in more than one cylinders.
ENGINE DETAILS
The main components of a steam engine are given below:
1) CYLINDER-it consists of two chambers viz one cylinder chamber and the other valve chamber . the piston moves inside the cylinder
2) PISTON-The piston reciprocates from one end to the other end in the cylinder due to the pressure steam this is filled with piston rings and these rings are used to prevent the leakage of steam from one side of the priston to the other . the movement of the piston from one end to the other is called stroke of the piston and volume swept through by the piston in one stroke is called stroke volume.
3) CONNECTING ROD AND CRANKSHAFT
The connecting rod is connected with the crankshaft by means of a crankpin. The circular motion of the crank shaft through connecting rod. Two strokes of the piston make one revolution of the crank shaft .
4) GOVERNOR
The function of a governor is to regulate the fluctuation of speed of a prime mover due to the variation of the load with in a small limit . in the case of a steam engine the object is to adjust the supply of steam to the cylinder according to the variation of load an to maintain the speed of the crankshaft constant.
INTERNAL COMBUSTION ENGINES
The internal combustion engine is a form of heat engine where combustion of the fuel takes place in a chamber and the heat of combustion is concerted into mechanical work. it may be classified as recuperating reciprocating engine, turbine and jet engine eg.
1. Reciprocating IC engine gas, petrol and diesel engine
2. Turbine type IC engine-gas turbines
3. Jet engine type IC engine-jet engine – rocket
Internal combustion engines have certain difference from steam engines. In a steam engine the combustion of the fuel takes place at the furnace and heat energy is conveyed by the steam from the boiler to the engine. The temperature inside the combustion chamber is much higher in internal combustion engines than in cylinders of steam engines.
COMMON HAZARDS
INTERNAL COMBUSTION ENGINES
These often from overheating caused due to leak of cooling water or failure of the water circulation. Over heating leads water or failure of the water circulation. Excessive wear in bearing produces irregular running and vibration which can cause distortion or breaking of the crankshaft.
STEAM TURBINE
This presents a catastrophe risk in that the speed and weight of the revolving parts can create a complete disruption of the entire turbine due to centrifugal forces. Such a disruption can be likened to a boiler explosion in force and intensity and over is required in respect or damage to surrounding property . vibration brought about by the disturbed balance of the rotor or by gearing becoming defective may result in the stripping of several rows of blades such breakdowns are therefore expensive and repair costs frequently run into several lakhs of rupees.
REFRIGERATING PLANT
Refrigeration is defined as a branch of science that deals with the process of reducing and maintain the temperature of a space or material below the temperature of the surrounding of a space or material below the temperature of the surroundings. The prevention of perishable commodities particularly foodstuffs is one of the most common uses of the mechanical refrigeration. In a mechanical refrigeration system the high pressure liquid refrigerant is made to evaporate in the pipe coils known as evaporators. The compressor, which is really a gas pump raises the pressure of the refrigerant gas and consequently the temperature of the also is raised and sent to the condensed.
AIR CONDITIONONG PLANT
An air conditioning plant consists of a refrigerator unit a hot water heating unit a fan for blowing the air past the hot or cold and ducts through which it is passed to all parts of a building systems also usually include air filters , air purifiers air washes and thermostats and automatic controls the compressors and pumps in the systems mat be either of reciprocating or rotary type.
DUST EXTRACTION PLANT
These are extensile used in laundries and factories and consist of a drum which revolves ata very high speed and caused water to be drawn out of wet material which has been placed in it . the water is thrown out of the drum by centrifugal force and passes through holes to be drained away.
BULK MILK STORAGE PLANT
this equipment consists of a Large stainless steel closed tank encircled by an outer shall forming a jacketed space in which the refrigerant coils are placed. the cooling is provided by an electric driven refrigerator and as the milk must be kept in a constantly stirred state an agitator paddle is mounted on a vertical shaft . the motor and gearbox is situated on the top of the vessel for driving the shaft.
COMMON HAZARDS
All lifts cranes and handling plant and contractors plant are subject to the risk of mechanical and electrical breakdown. Burning out complicated crane or lift motor is expensive and time consuming gearing shafts and bearings can fail and a feature of some types of crane is the abuse from which it can suffer unless a careful control is kept on the maintenance and operation . surrounding property of owner or third party nay be involved and accidents causing injuries to employees and third parties are common.
BOILER AND OTHER PRESSURE PLANTS
A boiler or steam generator is a closed vessel in which by the application of heat steam is generated from water above the atmosphere pressure. The steam pressure varies with the type of requirement and in some cases this high pressure steam is also superheated with the help of a superheater.the steam is utilized for driving prime movers like steam engines and steam turbines or for some other industrial purposes.
ELECTRICAL PLANT AND MACHINERY
Before going into details of equipment , here the direction of current in the circuit reverses in cycles called frequency .commonly used frequency is 50 cycles per second D.C current Is used in industries like electro-planting electro chemistry and battery charging. Current motors are used in railway traction cement plants and steel mills where initial torque requirement are high for which DC motors are more suitable otherwise AC system of current is used mostly all major industries.
COMMON HAZARDS ASSOCITED WITH ELECTRIC PLANT AND MACHINERY
The potential source of damage is deterioration of insulation which can be caused by age and or presence of moisture, dirt , oil and harmful environment condition . the insulation can be damaged by the fusing of wires of coils due to overheating single phasing , excessive unbalanced currents etc. mechanical failure which may arise from damage to shafts , discs, bearings and other metal parts. Motors and other metal parts. The other more common faults are excessive vibrations defective supports, neglect in renewing damaged or frayed parts bursting of binders entry of foreign objects like nuts, bolts, metal pieces , inadequate etc.
