Power Plant Guruji

Governor Issues Lead to Turbine Hunting If Turbine does not maintain the load as per set load, then this condition is called load hunting.  Following are the some potential reasons for load hunting 1- Problems associated with actuators: These are related to leakages in actuators, piston stuck up, oil holes elongation etc. Because of these issues there will interruption or fluctuation of secondary oil flow through actuators, this creates the problems of actuator miss- operation & eventually load hunting. 2-Improper calibration of actuators: This results into mismatch of actuator opening & given set point or valve demand 3- Lower control oil pressure than required: Actuators are designed for specific pressure of control oil, if the control oil pressure at actuator inlet becomes less, then there will be more chances of mal function of actuator. 4-Fluctuation of control oil pressure/flow: Fluctuation of control oil pressure or flow due to malfunction of pump or line PRV may lea...

WATER HAMMER The very large CCW flow rate results in huge kinetic energy of the flowing water, and hence it promotes severe water hammer during CCW pump start up, shutdowns and trips. How to Minimize Water Hammer To minimize water hammer the following general operating practices are used during CCW pump start up and shutdown. 1. A sufficient time delay before the next pump Is started up or shut down. This allows the energy of pressure waves in the system to destroy before the system is subjected to another flow surge. Time delay : About 5 minute 2.Proper position and slow opening / closing of the CCW pump discharge valve during pump start up and shutdown a)       Each CCW pump is started against its discharge valve fully closed or slightly pre-opened (depending on the plant) and then the valve opens gradually. b)       During normal pump shutdown first the discharge valve closes gradually and when it is fully closed (or nearly fully cl...

 Q.1  What is the difference between control oil & trip oil? Ans.             Trip Oil -  Oil passes through some of protection relays to open ESV is called Trip oil Turbine Trip Oil Circuit Control Oil  -  Oil goes to for operation of HP, IP & LP valve actuators through I to H converters is called as control oil Turbine Governing System Q.2  Why the control oil temperature is more than lube oil ? Ans.    To maintain low viscosity of the oil.   Because control & governing system internal parts have very low operating clearances.   So in order to maintain that control oil is not cooled & maintained its temperature around 60 deg     Actuators & ESV components are operating at very less clearance need low oil viscosity. Actuators & ESV components are operating at very less clearance up to 50 microns. Turbine Oil System Q.3 Mesh  size for lube oil ...

  Steam Turbine Wet Washing Washing Procedure : Turbine blades wet washing is carried out at condensate temperature around 100 deg C.  After shut down of Turbine, Turbine is allowed to cool to 100 deg C or if it is under shutdown then Turbine is heated up to 100 deg C.  Then Turbine is filled with 100 deg C condensate water through any of the Turbine casing drains or bleed lines. Later, the rotor is rotated slowly with barring gear for 3 to 5 hours & then the water will be drained.  This procedure is repeated for 3 to 4 times till you get clear water from drain. Wet steam is generally generated by injecting cold water in super heated steam.  This wet steam is allowed to enter into Turbine & keep the turbine speed around 500 to 1000 rpm depending on the Turbine speed or may be maintained around 10-20% speed.  Care should be taken for 100% removal of condensate water from wet steam.   Also there should not be variation in quality & tempe...

 1. What is the function of baffle plate in parallel flow type low level jet condenser? a) It keeps cooling water and exhaust steam from mixing b) It ensures proper mixing of cooling water and exhaust steam c) It collects condensate over it for extraction d) It helps condenser wall withstand the inside pressure Ans. b 2. Where is condensate extraction pump provided in case of low level parallel flow type jet condenser? a) At the bottom of the condenser b) At the top of the condenser c) Near the baffle plate d) Near the steam entry point Ans. a 3. Which of the following statements regarding low level counter flow type jet condensers is FALSE? a) Cooling water is broken into jets by perforated trays b) Condensate is collected at the bottom c) Steam is discharged near the bottom and moves upwards d) The air suction pump is placed near the bottom of the condenser Ans. d 4. Which of the following condensers is also called barometric condenser? a) Low level parallel flow type jet condens...

 1.Junction valve is used to ? a) Regulate flow of steam b) Regulate water supply c) Put off fire in the furnace d) Indicate water level in the boiler Ans. a 2. If the value of poisson's ratio is zero, then it means that ? a) The material is rigid b) The material is perfectly plastic c) There is no longitudinal strain in the material d) None of these Ans. a 3. Maximum heat is lost in the boiler due to ? a) Unburnt carbon  b) Flue gases c) Incomplete combustion d) Moisture in fuel Ans. b 4. Latent heat of vaporization at critical point is ? a) Less than zero b) Greater than zero c) Equal to zero d) None of the above Ans. c 5. The specific volume of water when heated at 0 deg. C is ? a) First increase and then decrease b) First decrease and then increase c) Increase steadily d) Decrease steadily Ans. d 6. The draught produced by steel chimney as compared to that produced by brick chimney for the same height ? a) Less b) More c) Same d) Can't determine Ans. b 7. For maximum disch...

 1. Main objective of boiler trial is ? a) To determine the generating capacity of the boiler b) To determine the thermal efficiency of the boiler, when working at a definite pressure c) To prepare heat balance sheet for the boiler d) All of the above Ans. d 2. Device used to put off fire in the furnace of the boiler, when the level of water in the boiler falls to an unsafe limit, is ? a) Safety valve b) Fusible plug c) Blow off cock d) Stop valve Ans. b 3. The shell of the cochran boiler is made hemispherical ? a) To provide maximum strength and space b) To withstand high pressure inside c) Both ( a ) and ( b ) d) None of these Ans. c 4. The dryness fraction of steam within a turbine is not allowed to fall below ? a) 0.5 b) 0.9 c) 0.95 d) 0.99 Ans. b 5. With increase in pressure ? a) Enthalpy of dry saturated steam increase b)  Enthalpy of dry saturated steam remains same c)  Enthalpy of dry saturated steam decreases d)  Enthalpy of dry saturated steam first increas...

 1. Which of the following statements is FALSE about double-pass condensers? a) The water flows in one direction through some tubes and returns through the remainder b) Exhaust steam flows through the tubes, while cooling water passes over the outer surface of the tubes c) It is a type of surface condenser d) Cooling water doesn’t come in contact with the exhaust steam Ans. b 2. Which of the following statements is False about steam condensers? a) Jet condensers are cheaper than surface condensers b) Cooling water comes direct contact with the exhaust steam in jet condensers c) Cooling water does not come in direct contact with exhaust steam in surface condensers d) Jet condensers are further classified into single-pass and double-pass condensers Ans. d 3. Which of the following statements is TRUE about single-pass condenser? a) It is a type of jet Condenser b) The flow of water is in one direction only c) The water flows in one direction through some tubes and returns through the ...

 Q 1. What are the difference between c onvective superheaters and r adiant superheaters? Ans.  Convective superheaters receive heat from flue gases. Radiant superheaters are placed in the furnace. The wall tubes of radiant superheater receive heat from the burning fuel through radiant process. Radiant superheaters are usually used where the steam is to be raised to a high superheat temperature. Q 2. What is the function of  a steam separator? Ans.  The function of a steam separator is to reduce the wetness of the steam by removing the water particles from the steam before it enters the steam turbine or engine. It is installed on the main pipe delivering the steam as close as possible to the engine. Q 3. T ypes of steam separator? Ans.  On the basis of principle of operation steam separators are classified into baffle or impact type, reverse current type and centrifugal type. There is a loss of heat in the steam pipe after the steam leaves the boiler which produ...