Power Plant Gyan

Its name from fact from its construction. Labyrinth seals consist of series of thin strips fixed to the casing or other stationary member and arranged so as to maintain the smallest possible clearance with the shaft. The labyrinth seals have small restrictions that increase the velocity of leaking fluid only to have it dissipated in the pockets, thereby throttling the fluid.  The tips of the strips are extremely thin so that if rubbing occurs the tip gets worn away without damaging the shaft.  These labyrinth seals do not prevent complete leakage of fluid. These are effective in only reducing leakage. In it steam in leaking must follow a winding path and change i ts direction many times. It is constructed from thin strip at the outer circumference of shaft of turbine at both end. It is installed at the inner circumferential surface of casing at both end. There are several types of Labyrinth packing is subjected to a throttling action.  This action produced a...

CONDENSATE EXTRACTION PUMP SYSTEM DESCRIPTION Condensate from condenser hot-well is pumped through LP heaters up to deaerator by Condensate Extraction Pumps (3 nos. CEP).  In full load operation two pumps will be in operation and one in standby condition. CEP is of vertical sleeve type multi stage pump.  So it is called as turbine type pump. Each pump is directly driven through an electric motor and is delivering to condensate water. All the CEP are connected to a common header through a non-return valve and motorized discharge valve. From that discharge header condensate passes through Gland Steam Condenser (GSC) and through a Deaerator control station. By modulating this valve Deaerator level is maintained according to the set point given. A recirculation valve is provided before Deaerator level control valve to maintain a minimum condensate flow through the pump & GSC. The main condensate is passed through Condensate Polishing Unit, GSC, LP heater-...

Auxiliary Steam common Header Charging SYSTEM DESCRIPTION : Aux steam system includes four  ways of steam source:  Start-up boiler or aux boiler,(If it is available in plant ) Low-temperature reheated steam supply  Main steam steam supply line Near by unit common header In normal, each unit aux steam is supplied by CRH steam. There is interconnection between aux steam headers of all units and also connected to start-up aux boiler.  Parameters of aux steam are: Aux steam pressure normal range: 8-12 kg/cm2 Aux steam normal temperature: 300-350 deg C. Initial conditions Aux boiler is running hot boxed-up condition station APRDS Pre Checks & Charging Procedure: Ensure that Auxiliary Boiler is ready for Aux Steam header charging from aux. boiler. Generally temperature maintain before charging from  aux boiler between range is 180 to 300 deg C and pressure is 4 to 5 Kg/cm2 All the way from Auxiliary boiler MS...

Drum Level Control in Larger Capacity Boiler In a large capacity boilers feed pump motor is not directly connected to the boiler feed pump. Between motor and feed pump a hydraulic coupling is used in which an arrangement is given for speed increasing and then regulating through the scoop tube. This provide a variable speed operation while motor is running at constant speed. With the help of scoop tube motor is started with no load and pump is running with it on a re-circulation mode. No direct mechanical connection is there between the motor and the pump shafts.  The coupling consists of a radial pump impeller mounted on the motor shaft and a radial flow reaction turbine runner mounted on the pump  shaft. Both the impeller and runner are identical in shape and they together form a casing which  is completely enclosed and filled with oil. When motor shaft is rotated, the oil starts moving from the inner radius to ...

ECONOMIZER Economiser is a pressurized back end equipment because of it is installed at the end of boiler. Where after no heat is added to the water or steam. Heat transfer surface used to increase the temperature of the feed water before it enters to the boiler drum. When flue gases travel across water-walls then latent heat is absorb & super heaters absorb sensible heat from flue gases. The economizer is composed of low-temperature convection pass surface. Economizer is placed in series with the feed water heaters of the regenerative system. The function of the economizer is, to raise the temperature of feed water downstream of the highest pressure feed water heater to the saturation temperature corresponding to the boiler pressure. After absorbing the heat from flue gases to the super heater and reheater by steam some heat is present in flue gas this heat is absorbed by sub cooled feed water which is flow in side economizer before entry of boiler drum. With this typ...

GOVERNING OF STEAM TURBINES Requirement of governing system:- Controlling and regulating of a turbine according to variable demand. The regulation of turbine is done by maintaining control of speed, pressure and flow by the help of governors. Governing of turbine maintains the speed of turbine at constant level irrespective of load. Governing of steam turbine is classified according to the mechanism  (i) Throttle governing (ii) Nozzle control governing (iii) By-pass governing (iv) Combined governing (i.e., Combination of above as throttle and nozzle control governing or ‘throttle and by-pass governing). (i) Throttle Governing:   Throttle governing of steam turbine bases upon the throttling of steam up  to suitable pressure and regulate the mass flow of steam through the turbine so as to control the output  of turbine.  Here in throttle governing, aim is to alter the mass flow rate as for example by reducing it, the  av...

BOILER DRAUGHT Draught refers to the pressure difference created for the flow of gases inside the boiler. Boiler unit has a requirement of the expulsion of combustion products and supply of fresh air inside furnace for continuous combustion. The flues gases or combustion products formed during combustion should be discharged at such a height. A chimney or stack is generally used for carrying these combustion products from inside of boiler to outside , i.e. draught is created by use of chimney. Draught may be c reated naturally or artificially by using some external device.  Draught can be classified as below: In natural draught the pressure difference is created naturally without using any positive displacement device. Artificial draught is created using some external assistance causing forced displacement of gases . It can be created either by using mechanical devices or steam. Artificial draught can be of induced type, forced type or combination...

CIRCULATION SYSTEMS In power plant boiler is used as a steam generator. From boiler high pressure & high temperature steam is generated and used in steam turbine. In power plant boiler may be drum type or without drum. Drum type boilers are called as sub-critical boiler because its working pressure is bellow critical pressure while without drum type boiler is called once through boiler because its pressure is higher than critical pressure. In sub-critical units boiler drum  acts as reservoir for  water & saturated steam and also provides means and arrangements for separation and purification of steam.  The term circulation generally refers that "the movement of fluid from boiler  drum to the combustion zone (furnace water walls) and back to the drum". In boiler drum steam separator equipment are installed. Feed water is supplied to the drum via the economizer in heated condition. when feed water enters in to the boi...

REGENERATIVE FEED WATER HEATING SYSTEM In regenerative feed water system steam is bled from the turbine from various stages and is made to give up its latent or any super-heat to the condensate in a heat exchanger, this system is called regenerative system. What is Regenerative Feed Heating? A small portion of steam expanding through the turbine is bled off from different stages of turbine before reaching condenser and used to heat feed water in the feed water heaters. This is called regenerative feed heating system. Why Regenerative Feed water heating? Loss of work that could have been obtained by expanding the extracted steam in the turbine (because of if we expand more steam from the turbine then after doing work this steam condensed in the condenser due to which its losses latent heat after condensation). Reduction in the energy supplied in the boiler (reduction of coal required in boiler which release energy after burning) to raise the temperature and pressure of the...