Monday, 20 August 2012
Aims and objectives of maintenance:
The purpose of maintenance is to maintain the steam turbine in order to achieve as high a plant availability as possible at the minimum cost. Maintenance of steam turbines used in power station may be classified broadly in three categories:
Rectification of defects: The defects may or may not be urgent. If immediate repairs are needed, these may be carried out on running limits...
Monday, 20 August 2012 0
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B. Sequence when the turbine is in motion:
Apply the load gradually.
Check up the oil pressure going to the bearings and control gear.
Observe the oil bearing temperature.
Observe the turbine for any noise, vibration by watching the vibration and other indicators.
C. Sequence when shutting the turbine down:
Gradually reduce the load to 0.
Start the auxiliary oil pump and make sure that oil will...
The following are the sequences of turbine operation:
A. Starting Sequence:
Application of controlled power illuminates all of the malfunction lights. This provides a check of the malfunction lights before starting the turbines.
Reset malfunction circuit by operating a reset switch. Malfunction lights go off and all control devices assume the condition for starting.
Inspect the governor mechanism, till all grease cups...
From the theoretical point of view, a turbine rotor is a balanced body but in actual practice, errors of balance are introduced by various causes such as:
Lack of homogeneity of material
Slight error in machining.
Difference in pitch of blades and also in individual masses
Therefore, it is essential to test balance of a complete turbine rotor and make any adjustments necessary to ensure that the balance is as...
Types of Rotors:
There are 5 types of steam turbine rotors:
The built-up rotor
The integral rotor
The hollow drum rotor
The solid drum rotor
The welded disc rotor
1. The Built-up Rotor:
It consists of forged steel shaft on which separate forged steel discs are shrunk and keyed. It is cheaper since the disc and shaft are relatively...
Sunday, 19 August 2012
The attachment of the turbine blades to the rotor is the most critical aspect of steam turbine design. All the forces are transmitted through the attachment to the rotor. Specially, at the low pressure end of turbines of large output, the attachment has to bear a relatively large forces due to high speed, the centrifugal force on the blade is many times its mass. Therefore it becomes necessary to estimate the stresses in the...
Sunday, 19 August 2012 0
Stiffness against vibration and correct guidance to the steam is essential. To meet these conditions the outer ends of the blades are usually tied together by a perforated ribbon of metal known as Shroud. In case where stress consideration is of primary importance, for example, the last row of the low pressure blades, the shroud is omitted. In longer blades of LP turbine, lasing or binding wires are also silver soldered to...
Production of Blades
Blades may be considered to be heart of turbine, and all other members exist for the sake of blades. Without blading, there would be no power and the slightest fault in blading would mean a reduction in efficiency or lengthy and costly repairs.
The following are some of the methods adopted for the production of blades:
Rolling - Sections are rolled to the finished size and used in conjunction...
Hollow blades satisfy the condition for ideal blades ie they give the most efficient control to the steam and are at the same time uniformly stressed . The hollow blades do not impose severe stresses in the rotor, and for that reason increased speed, leading to increased output is possible...
The blades of low pressure stage must be long to cater for the greatly increasing specific volume of steam at the lower pressures. Irrespective of the design of previous stages, the final stage of LP turbine employ little or no reaction at the root and up to about 65% reaction at the tip, this design allows the steam velocity to match...
Design requirements of nozzle:
The design of nozzle should be such as to permit easy manufacturing and finishing and allow accurate channel sections to be obtained specially at the high pressure end of the turbine.
The inlet of the nozzle should be so designed as to utilize the carry over energy from the previous stage to the largest...
(Image credit: sokeo.com)
The aim of engineering science theory is to design and the ultimate aim of any design is to construct as per design so that the product maintains its high quality with minimum cost and requires minimum maintenance. This topic deals with construction of steam turbine components. The construction of rotor will...
Wednesday, 15 August 2012
Filler metal:
It is the material that is added to the weld pool to assist in filling the gap or groove. Filler metal forms an integral part of the weld. Filler metal is usually available in rod form. These rods are called filler rods. Filler rods have the same or nearly the same chemical composition as the base metal. Welding filler...
Wednesday, 15 August 2012 0
Introduction to Gas Welding:
Gas welding is a fusion welding process. It joins metals using the heat of combustion of oxygen/air and fuel gas that is acetylene, hydrogen or butane. The intense heat or flame thus produced melts and fuses together the edges of the parts to be welded with the addition of a filler metal.
Oxy-acetylene welding:
When...
The chosen welding processes of practical significance in underwater welding are:
Manual shielded meal arc welding, that is extensively used as a wet technique but is also suitable for habitate welding.
TIG welding.
MIG welding.
TIG and MIG welding processed have also been used to a limited extend for wet welding as well as more commonly in local enclosed gas shrouds.
1. Shielded metal arc welding:
Manual shielded metal...
International interests to develop and utilize oceans which cover 70% of the earth and its resources such as development of offshore gas and oil field, fisheries multiplication, large offshore construction and mineral resources, mining in the sea bottom,etc; have let to the development of underwater welding. Underwater welding has been used for temporary repair work caused by ships collisions, unexpected accidents, corrosion...
Saturday, 11 August 2012
Cam and follower (Image credit:cnx.org)
A camshaft is simply a shaft on which cams are mounted. The camshaft is mounted in bearings in the lower part of the cylinder block in most inline engine. In few engines, it is located on the cylinder head. A cam is a device that changes rotary motion of the camshaft into linear motion of the...
Saturday, 11 August 2012 0
Valve (Image credit: rexresearch.com)
Valve is a device to close and open a passage in motor vehicle engines. Two valves are used for each cylinder - An inlet or intake valve and an exhaust valve. Fuel is admitted to the cylinder by the inlet valve, and the burnt gases escape from the exhaust valve. When closed, the valve must seal...
Flywheel is a heavy steel wheel attached to the rear end of the crankshaft. The size of the flywheel depends upon the number of cylinders and the general construction of the engine.
Flywheel (Image credit: casting quality.com)
The flow of power from the engine cylinder is not smooth although the power impulses in a multi-cylinder...
Crankshaft is the first part in the power transmission system onto which the reciprocating motion of the piston is converted into rotating motion with the help of connecting rod. A crankshaft consists of crank pin, crank arm, balancing weight and main journals. Big end of the connecting rod is connected to the crank pin of the crankshaft....
Connecting rod (Image credit: race.nangreaves.com)
The connecting rod is the connection between the piston and the crankshaft. It joins the piston pin with the crank pin. Small end of the connecting rod is connected to the piston pin and larger end to the crank pin. The function of the connecting rod is to convert linear motion...
Piston pin (Image credit: gasgoo.com)
Piston pin or wrist pin or gudgeon pin connects the piston and small end of the connecting rod. Piston pin is generally hollow and made from case hardened steel heat treated to produce a hard, wear resisting surface. Piston pin may be selectively fitted and, if supplied with the piston, are not interchangeable....
Piston rings are fitted into the grooves of the piston to maintain good seal between the piston and the cylinder wall. There are three functions of the piston rings.
To provide a pressure seal to prevent blow-by of burnt gases. Blow-by is the name that describes the escape of burnt gases from the combustion chamber, past the piston,...
Piston (Image credit: btechgurus.blogspot.com)
Piston is one of the most important part in a reciprocating engine in which it helps to convert the chemical energy obtained by combustion of fuel into useful mechanical power. The purpose of the engine is to provide a means of conveying the expansion of the gases to the crankshaft via...
There is problem of cylinder wear in I.C. engine and this is solved by use of cylinder liners. Cylinder liners are in the form of barrels made of special alloy iron containing silicon, manganese, nickel and chromium. They are cast centrifugally. It is now customary to fit cylinder liners on engines of cars and commercial vehicles....
The bottom half of the crankcase is called the oil pan or sump. It is bolted or screwed to the lower flange of the main casting of IC engine and usually is made of pressed steel or aluminium. Oil pan serves as the reservoir for the storage, cooling and ventilation of engine lubricating oil.
The plane of the joint between the crankcase...
Crankcase is attached to the bottom face of the cylinder block in I.C.engine. It acts as the base of the engine. It supports the crankshaft an camshaft in suitable bearings and provides the arms for supporting the engine on the frame. The oil pan and the lower part of the cylinder block together are called the crankcase.
Crankcase with...
In an Internal Combustion Engine, the top of the cylinder is covered by a separate cast piece known as the cylinder head. The cylinder head is bolted to the top of the cylinder block. It contains combustion chamber. Spark plug and sometimes valves are mounted in it. It incorporates passages for the flow of cooling water.
Cylinder...
Friday, 10 August 2012
Cylinder block, cylinder head and crankcase are the main stationary bodies of the automobile engine. They serve as support and enclosure for moving parts. Nowadays the cylinder block and crankcase form a single casting which gives a rigid structure. Ribs are cast in the crankcase to give it extra strength and to support the main and camshaft...
Friday, 10 August 2012 0
Internal Combustion Engine (I.C. Engine) is basically heat engine and converts heat energy into mechanical energy. I.C. engines are used mainly in the field of transportation but in many industries, farms; simplicity and low cost of operation are the determining factors in the adoption of I.C. engine. Internal Combustion Engine is that...
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