Mechanical Guru's

COMPLEX MECHANICAL SYSTEMS    ·          Coal handling system    ·          Steam generation system    ·          Power generation system    ·          Feed generation system    ·          Ash water system    ·          Steam condenser system     ·          Draught system    ·          Air distribution system  Ø   Coal handling system The coal handling system is the most important functionary part thermal power plant. The Steps involved in the coal handling system are as follows:    ·          Coal delivery    ·          Unloading    ·          Preliminary coal preparation    ·          Outdoor storage    ·          Covered storage    ·          In plant handling    ·          Dust control system    ·          Palavering    ·          Feeding the coal into furnace  Ø   Steam generation system Coal handling plant sends the prepared coal to steam generation system. In this system, coal is burnt and heat thus produced is transferred to w

THERMAL POWER PLANT WORKING Thermal power plant use raw energy in fossil fuels (coal, oil, or gas) and convert it into mechanical energy through the expansion of steam from a high pressure in a suitable prime mover called steam turbine. Generator coupled with turbine produces electrical energy. Coal received from collieries in the rail wagons is mechanically unloaded by wagon Tippler and carried by Belt Conveyor system to Boiler Raw Coal Bunkers, after crushing in the Coal Crusher. The crushed coal, when not required for raw coal bunkers, is carried to cal storage area through belt conveyor and telescopic chute. The Raw Coal Chain Feeder regulates the quantity of coal from coal bunkers to Coal Mill, where coal is pulverized into the fine powder form. The pulverized coal is then sucked by Vapour Fan and finally stored in the pulverized Coal Bunkers. The pulverized coal is then pushed to the Boiler Furnace, which is comprised of water tube walls all around through which water circul

RELIABILITY Reliability of a system (product) conveys the concept of dependability, successful operation or performance and the absence of failures. Reliability is the probability that a machine (product) can perform its intended function, without failure, for a specified interval of time when operating under standard conditions. It should be observed that the above stated definition stresses four significant factors; probability, intended function, time and operating conditions. These four elements play an important role in characterizing the reliability of an item. Increased reliability implies less failure of the machinery and consequently less downtime and loss of production. Product reliability is affected by usage mode, environment and maintenance actions. Quantitatively reliability may be considered as a measure of the success of an engineering system in meeting its stated objectives. The concept of reliability has been interpreted many different ways in numerous works out

AVAILABILITY  Availability is a performance criterion for repairable systems that accounts for both the reliability and maintainability aspects of a system. It is defined as the probability that the system is operating properly when it is required for use. That is, availability is the probability that a system is not failed or undergoing a repair action when it needs to be used. The numerical value of availability is expressed as a probability from 0 to 1. Availability calculations take into accounts both the failures and repairs of the system. For example, if a lamp has 99.9% availability, there will be one time out of a thousand that someone needs to use the lamp but it is non-operational because the switch is broken, or it is waiting for the replacement of a light bulb etc.    AVAILABILITY CLASSIFICATION The definition of availability is somewhat flexible, depending on what types of  down times  are considered in the analysis. As a result, there are a number of different

FUSIBLE PLUG Function:   Its function is to protect the boiler against damage due to overheating for low water level. It is fitted in the crown of the furnace or firebox at appropriate place. Working:   In the normal working conditions of the boiler, the fusible plug is fully submerged under water. This is so because under normal condition, proper water level is maintained & can be checked by water level indicator. Under the circumstances, the heat from the fusible plug is being conducted to water. This keeps the fusible metal at an almost constant temperature, much below its melting point. When the water level falls below the fusible plug, the plug gets uncovered from water. The upper portion of the plug gets exposed to the steam space. The steam cannot keep the plug cool. This will over heat the fusible metal. The plug falls down along with the fusible metal making a hole. The steam and water, being under pressure immediately reach the firebox and extinguish the fire.

BLOW OFF COCK Functions: ·         To discharge a portion of water when the boiler is in operation to blowout mud, scale or sediment periodically. ·         To empty the boiler, when necessary for cleaning, inspection & repair. ·         It is fitted on the boiler shell directly or to a short branch at the lowest part of the water space. This pipe is known as blow-down pipe. Working:   In order to operate the valve, the rectangular slot is brought in line with the passage of the body. This is possible by rotating the plug with the help of wheel. When the slot is placed in this position, the cock is opened and all the impurities, mud, sediments etc. Start flowing out of the boiler and they are removed. When the slot is brought at right angles to the passage of the body, the cock is closed. Image - Blow Off Cock Fig - Blow Off Cock

FEED CHECK VALVE Function:   It is used to control the supply of water to the boiler & to prevent the escaping of water from the boiler when the pump pressure is less or pump is stopped. Working:   Under normal working condition, the pressure on the feed pump side (connected to elbow) is more than the boiler side pressure. This pressure difference lifts the check valve. To allow the feed water to enter the boiler, the feed valve is lifted manually. Hence, the feed water may enter the boiler. In order to control the supply of feed water to the boiler, the position of the feed valve is controlled. In the event of failure of feed pump, the pressure on the water sump side reduces. The check valve will be closed because of higher I mage - Feed Check Valve

DEAD WEIGHT SAFETY VALVE Function:- A valve is placed upon a valve seat that is fixed upon a long vertical pipe having a flange at the bottom for fixing at the top of the boiler. Suspended at the top of the valve is the weight carrier that carries cast iron rings. The total weight must be sufficient to keep the valve on its seat against the normal working pressure. When the steam pressure exceeds the normal limit, it lifts the valve with its weight & the excess steam escape through the pipe to the outside. This valve is used only with stationary type of boilers. It is the most elementary type of safety valve. The objection to dead weight safety valve is the heavy weight that has to be carried. Image - Dead Weight Safety Valve Figure - Dead Weight Safety Valve

WATER LEVEL INDICATOR Function:   It is indicates the water level inside the boiler to an observer. Working:  The water of the boiler comes into the glass tube through the lower tube and the steam through the upper tube. The water then stands in the glass tube at the same level as in the boiler. Two cocks are used to control the passage of between the boiler and the glass tube while the third cock is in used to discharge some of the water from inside the boiler to see whether the gauge is in proper order or not. The glass tube is protected by means of a cover, made of specially toughened glass, which will prevent any accident that may happen due to breaking of glass tube. It is used for ordinary boilers. Image - Water Level Indicator Figure - Water Level Indicator

STEAM PRESSURE GAUGE Function:   The function of the pressure gauge is to measure the pressure exerted inside the vessel. Working:   The pressure gauge is connected with the boiler’s steam space through a U-tube siphon. The U-shaped pipe contains water, which fills the Bourdon tube. The pressure of the steam acting through the water on the inside of the tube tries to make the tube circular. One end is fixed, the free end moves. Because of pinion & gear arrangement, the slight movement of the Bourdon tube is magnified considerably and the point gives a maximum deflection, which can be read on the scale. Image - Steam Pressure Gauge Fig. - Steam Pressure Gauge

STEAM STOP VALVE Function: The function of the steam stop valve is to regulate the flow of steam from one steam pipe to the other or from the boiler to the steam pipe. The steam stop valve when directly mounted on the steam space of the boiler shell & connected to the steam pipeline which supplies steam to the prime mover is called a junction valve. Working: When the hand wheel is turned in anticlockwise direction, the spindle is raised up. This will raise the valve from its seat. Thus a passage for the steam from the clearance between the valve and the valve seat is formed. In order to lower the valve, the hand wheel is rotated in clockwise direction. This rotation will close the passage for steam. Adjusting the position of the valve based on the requirements can regulate this. Under the normal working condition, the valve is open and the steam flows from the boiler to the steam pipe. Image - Steam Stop Valve Figure - Steam Stop Valve