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Mechanical Engineering
Mechanical Engineering is a branch of engineering that encompasses the generation and application of heat and mechanical power and the design, production, and use of machines and tools. Mechanical engineering involves application of the principles of dynamics, control, thermodynamics and heat transfer, fluid mechanics, strength of materials, materials science, electronics, and mathematics.
10,989 Questions
Material: 2 litre pop bottle (empty) -- coat hanger wire - 12-15 cm long - straight -- empty film container -- tin can (tomato can) -- masking tape -- string -- aerosol can cap -- copper wire Method: 1) Cut 4 slits in the film container, 1 cm long at equal distances between them. From a tin can cut 4 blades for the water wheel. 2) Push the smaller end into the slits. 3) Make a hole with a nail in the exact center of the lid and the bottom of the film container. 4) Push the coat hanger wire through the holes to make an axle for the wheel. 5) Cut off the top of the pop bottle and make two holes at the opposite ends, about 4 cm from the top. These holes accept the axle - coat hanger wire. 6) Wind a short piece of wire around the end of the axle just outside the bottle so that it will not move out. 7) Make a spool out of the longer end of the axle using two pieces of cardboard glued on it. 8) Tie a string about a metre long to the spool and hang a "bucket", the cap of the aerosol can. 9) Pour a stream of water on the blades of the wheel and the wheel turns. 10) The string winds itself onto the spool and the "bucket" is lifted up.
What is a measuring instrument starting with g?
A graphometer is a surveying instrument. It is used to measure angles.
Describe the specific safety precautions to be taken when carrying out fault diagnosis of the specific piece of equipment
What is the purpose of hidden lines and center lines?
The purpose of hidden lines is to represent edges that are not directly visible. The purpose of center lines is to represent the axes of circular features.
In a rack and pinion system, a bull gear is typically the last reduction gear in the geartrain. It transmits torque to an output pinion which is in contact with a rack.
How do you calculate shot capacity for plastic injection molding?
Production rate of injection molding machine depends upon cycle time (total time that machine takes to produce a product in one cycle) and the number of cavities. For calculating cycle time, you must consider time for each phase that machine takes in one cycle. That phases are:
- Mold closing / clamp
- Filling
- Pack and hold
- Cooling and Recovery (40-60% )
- Mold Open
- Ejection Add time taken by each phase. For example, this time is 15 seconds and the number of cavities are 2. So the production rate is 2 finished product per 15 seconds. You can increase your production by decreasing the cycle time. You can decrease cycle time by following some points:
- Keep wall thickness to minimum required for your product
- Ensure your machine is fine-tuned
- Ensure proper cooling system, injection pressure and injection speed is applied.
What are the dimensions of a 10000 gallon oil tank?
The most common 1000 gallon oil storage tank is a flat-ended cylinder 48 inches in diameter. A gallon is 231 cubic inches. The area of a 48-inch circle (radius = 24") is pi*24² = 1809.56 in². 231,000 / 1809.56 = 127.7", or just under 10'-8". The nominal length is 10.5 feet.
What is the Indian standard of SG 500 7 grade cast iron?
This is Speroidal Graphite iron casting.
Mechanical Properties required are as followed,
Tensile Strength ( MPa ) - Min. 500
Min. 0.2 % Proof Stress ( MPa) - Min. 320
Elongation ( % ) - Min. 7
Brinell Hardness (BHN ) - 160-240
Predominant Constituent of Matrix - Ferrite + Pearlite.
Regards,
Sujit Doijad
09762225010
s.doijad@rediffmail.com
What is eccentricity in steam turbine shaft?
Eccentricity is the deflection in the shaft away from truly straight. The turbine shaft when not turning will settle into a bowed shape (measured in thousandths of an inch), this is the deflection from straight. Large turbines are placed on turning gears as they are cooled or warmed up to minimize this deflection. As a turbine is started this eccentricity produces vibration as the deflection changes rotational position, if the turbine is started up too quickly this deflection will increase as a result of inertia trying to deflect the weight of the deflected shaft outward. Eventually the deflection, as a result of rolling the turbine up slowly, will straighten to the true center of the turbine shaft.
What is the advantage and disadvantage of reciprocating compressors?
The advantages of the reciprocating compressors is that it is easier to install and is very simple to install. The disadvantage of the reciprocating compressor is the high cost of maintaining it because of the many moving parts.
Steam Turbine Turning Gear - Turning gear is utilized on turbines to reduce eccentricity or out of round of the rotor. When a rotor is standing still it has a tendency to sag due to its weight.
While running a turning gear which is a separate motor that turns the rotor slowly 10-50 RPM through a clutching mechanism. This rotation keeps the rotor in balnace.
It is very important to run the turning gear on shutdowns and start ups. The time required to run is dependent on the size of your unit.
Typically the turning gear must be on for 12-36 hours for small to large steam turbins after shutdown and 2-16 hours prior to a turbine start.
If a turning gear is not utilized the rotor will become eccentric and may cause vibration up to wiping rotating parts with the stationary parts causing catastrophic failure.
Steamengineer @ Gmail
What are the advantages of steel tubing?
In some cases, depending on the size and weight of tubular steel pipe vs the same or similar size solid steel bar, the tubular steel might be stronger. The molecular structure of the solid steel have the molecules stacked close together, any shock or stress will compress the molecules closer together with no place to go unless the steel bends or breaks. A steel tube has the hollow area which allows shock or stress to be released, it will be less likely to bend or break. It also depends on what the application is tubular steel will definitely be lighter in weight, can be filled, run wiring or plastic tubing through it. Cost is cheaper.
What is heat transfer coefficient of mild steel and stainless steel?
About 8W/m2K for MS Steel against air convection
That depends on how the glass is fabricated and finished and the environment it is in, and the type of glass. In general, and approximately,
For perfect glass fibers, strength is 500,000 psi (3500 MPa).
For polished glass windows, in air, strength is 7000psi (50MPa)
For scratched glass, 100 micron deep scratch, it is 2500 psi (20 MPa)
For scratched glass in high humidity for several years it is 1000 psi ( 7 Mpa)
How many people in china have cars?
one source put it at 2 per every 1 person, another said what's a car
What qualifications are needed for mechanical engineering?
Maths & physics, that's the two main ones
Length of courses are based on experience and qualifications.
Degree courses are 4 years.
HNC 1 year - gain entry to 1st or 2nd year in a degree course
HND 2 year - gain entry to 2nd or 3rd year of a degree course
Basically looking at a minimum of 4 years study
hope this helps
What are the application of chemistry in civil engineering?
Actually its answer is very easy and very simple where as you know that all things made by soem chemistry formula where you know that a metal is combinations of amny metals and also some chemicals which are used in different technology also made by combinations of different chemicals so the role of chemistry is much more important in each and every technology even in civil technology,,,, i think there will be no more capacity to understand you about it,,,
How governing system of steam turbine is being done?
(pictures insert is not being allowed by wiki. i am sorry)
TOPICS OF DISCUSSION
CONCEPT OF GOVERNING SYSTEM
FEATURES OF KWU GOVERNING SYSTEM
OVERVIEW OF GOVERNING RACK
FUNCTIONING OF EHC CIRCUITS
FREE GOVERNOR MODE OPERATION
BEST PRACTICES IN GOVERNING SYSTEM
EMERGENCIES IN GOVERNING SYSTEM
WHAT IS GOVERNING SYSTEM ?
n Turbine Governing system is meant for regulation of turbine speed under no load and varying load condition.
n It helps in precise control of grid frequency under normal operation and protects the machine as well as grid during emergency situation.
KWU GOVERNING SYSTEM-FEATURES
n ELECTRO-HYDRAULIC GOVERNING SYSTEM WITH HYDRAULIC BACKUP
n OPERATION OF STOP VALVES BY STARTING & LOAD LIMITING DEVICE (HYDRAULIC)
n ROLLING, SYNCHRONIZATION & LOAD OPERATION BY HYDRAULIC / ELECTRO- HYDRAULIC SYSTEM
n ELECTRO- HYDRAULIC SPEED GOVERNOR WITH HYDRAULIC BACK UP
n SAFE SHUTDOWN BY HYDRAULIC / ELECTRO- HYDRAULIC SYSTEM
n ELECTRICAL AND HYDRAULIC PROTECTION SYSTEM ALONG WITH TEST FACILITIES
FEATURES OF EHC
n AUTO ROLLING & SYNCHRONIZATION THROUGH SPEED CONTROLLER UNDER INFLUENCE OF TSE
n CONSTANT LOAD OPERATION BY LOAD CONTR. WITH PRESSURE CONTR. AS BACKUP
n RUNBACK OPERATION THROUGH PRESSURE CONTR.
n EMERGENCY OPERATION THROUGH SPEED CONTR.
n AUTO GRID FREQUENCY CONTROL THROUGH EXTERNAL FREQUENCY INFLUENCE
n AUTO UNLOADING AT HIGH FREQUENCY THROUGH INTERNAL FREQUENCY INFLUENCE
n CONTROL DURING AUTOMATIC TURBINE TESTING,
ISOLATED GRID CONDITION & LSR OPERATION
SPEED CONTROLLER CIRCUIT
L - Raise & Lower command from UCB :
nr - Speed Reference :
nr limit - Delayed Speed Reference :
NLC - No Load Correction (Ensures required Speed controller O/P for Rolling even when Speed reference n r matches n act.)
n act - Actual Speed :
hr nc - Speed Controller O/P with DROOP of + / - 10.0 V for nr lim ~ n act = 150 RPM ( GAIN = 22
LOAD SET POINT GENERATION CIRCUIT
1 - SET POINT FOLLOW UP when Automatic Grid Control or CMC In service
(Other Raise / Lower commands get blocked)
2 -- TSE ENABLING when
A) GCB is closed AND
B) Load controller (L C) not OFF AND
C) Fast calibration signal 6 absent AND
D) I) Load controller (L C) in control
OR ii) Pressure controller with initial pressure in action
OR iii) Turbine follow mode in service
This helps to bring manually adjusted gradient and stress effect in service.
+/- 10 V gradient => +/- 25 MW / MIN for 200 MW units
OR +/- 50 MW / MIN for 500 MW units.
PRESSURE CONTROLLER CIRCUIT
EHC TRANSFER CIRCUIT
FGMO - BACKGROUND
n Unique frequency band of 49.0 Hz to 50.5 Hz, as specified by IEGC
n Scheduling & dispatch by RLDCs/SLDCs is based on day ahead demand & availability
n Frequency control by load-generation balance in every 15 mins time block
n Wide frequency variation during Grid disturbance, Unit outage, change in demand, etc.
n No primary response by generators to maintain frequency under such system contingency
n Emergencies caused due to frequency control only through importing /cutting load by system operator
n
FGMO - GRID CODES
n All generating units should have their speed governors in normal operation at all times to enable Grid frequency control by loading / unloading
n Droop characteristic for primary response should be within 3% to 6%
n Each unit shall be capable of instantaneously picking up at least 5% extra load for a minimum of 5 mins (up to 105%MCR), during fall in frequency
n No dead bands and/or time delays shall be deliberately introduced
n Facilities like load limiters, CMC, etc. shall not be used to suppress the normal governor action
IMPLEMENTATION OF FGMO
In line with clause Clause 1.6 of IEGC and CERC order dated 30-10-99, date of FGMO implementation, as decided by REBs are :-
n Western Region - 19-05-03 ( ABT - 01-07-02 )
n Southern Region - 01-08-03 ( ABT - 01-01-03 )
n Northern Region - 01-10-03 ( ABT - 01-12-02 )
n Nor-East Region - 22-12-03 ( ABT - 01-11-03 )
n Eastern Region - 02-01-04 ( ABT - 01-04-03 )
FGMO CHARACTERISTIC FOR KWU M/C
MAJOR ISSUES WITH FGMO IN 2004
Ø Wide and frequent variation of freq.
Ø Perpetual oscillations in critical parameters due to Boiler response time
Ø M/C subjected to cyclic loading and fatigue stresses
Ø Frequent HP/LP Bypass valve operation
Ø Continuous manual interventions
Ø Self-defeating feature(Unloading when freq. improving towards 50 Hz)
Ø Conflict with ABT(Offsetting freq. correction)
TRANSIENTS IN GOVERNING SYSTEM
n FAILURE OF POWER PACKS OF CONTROLLER RACKS IN EHC PANEL
n POWER SUPPLY FAILURE IN ATRS PANEL
n SIGNAL ACQUISITION PROBLEM
n FAILURE IN TURBINE SYSTEM
n ELECTRICAL SYSTEM FAILURE
n COMPONENT FAILURE IN GOVERNING RACK
n OPERATIONAL EMERGENCY
1 CONTROL RACK SUPPLY FAILURE
n M/C is on EHC. Power supply fails in Load control/Pressure control / transfer circuit rack. Starting device becomes off automatically due to EHC fault.
Observation: EHC output is minimum/zero and load minimum/ zero with EHC fault alarm. Machine on bar with ESV & IV open (Turbine not tripped).
Action: Confirm HP/LP bypass opening, isolate EHC from governing rack and parallely adjust starting device position from UCB. Reduce boiler firing to restrict rise in boiler pressure.
2) SUPPLY FAILURE IN ATRS PANEL(ATRS=Automatic Turbine Rolling & Synchronisation)
n M/C is on EHC. Power supply fails in CCA panels only.
Observation: All indication lamps in ATRS consoles will go off. EHC output and Load will become zero due loss of GCB close feedback. All ATRS drives will become inoperative.
Action: Confirm HP/LP bypass opening , isolate EHC. Reduce boiler firing. Adjust starting device position from local. Normalize power supply in CCA panels at the earliest.
3) SIGNAL ACQUISITION PROBLEM
n Loss of speed signal occurs due to Hall Probe / card failure.
Observation: Speed indication will become zero. M/C will be loaded through speed controller. Subsequently Pressure controller will come in service. AOP & JOP will take auto start & Barring Gear valve Will open on auto.
Action: Isolate EHC and adjust Starting device position. If pressure oil pressure is normal, make SLC of AOP, JOP and Barring Gear vlv OFF and stop AOP, JOP and close Barring Gear vlv.
4)FAILURE IN TURBINE SYSTEM
n Loss of speed signal occurs due to breakage of MOP shaft.
Observation: Speed indication and pressure oil pressure will come down. M/C will be loaded through speed controller and Pressure controller will come in service. Subsequently, AOP & JOP will take auto start &Barring Gear valve. will open on auto.
Action: Safe shutdown of M/C is to be ensured.
5) ELECTRICAL SYSTEM FAILURE
n M/C is on EHC with Tracking on. Starting device becomes inoperative due to Electrical module trouble/motor failure/overload.
Observation: During increase in boiler firing, Boiler pressure will increase due to load restriction by Starting device. EHC output will go to 100%.
Action: Switch off the electrical module of Starting device and increase Starting device position from local so that EHC can take control.
6) FAILURE IN GOVRRNING RACK
n EHC Plunger coil failure
n EHC Pilot valve bearing failure
Observation: EHC starts hunting
Action: Isolate EHC and take Hydraulic mode in service. Replace the failed omponent. Governing characteristic checking should be done before EHC is put in service
n Speeder Gear spring tension gets altered.
Observation: M/C may get unloaded at frequency lower than recommended value.
Action: Speeder Gear spring tension may be adjusted to increase the start of unloading.Testing for proper setting should be checked during suitable opportunity.
LOGICS
A SPEED CONTROLLER LOGICS
1 Command for slow rate at nr > 2850 RPM to facilitate easy synchronisation
2 TSE Influence ON, when min of all the upper stress margins comes into picture to control gradient of nr lim and hence, acceleration of Rolling speed. Upper stress margin = 30 deg C => 10.0 V => 600 RPM ~ (Acceleration < 108 RPM ~ causes dn / dt tripping)
B LOAD SET POINT GENERATION LOGICS
1 Stopping of nr lim when
a) GCB open AND
b) n act is < nr lim by approx. 45 RPM.
This restricts hr nc up to around 30 % during Rolling to avoid wide v/v opening.
2 Stopping speed set point control when,
a) n act > 2850 RPM AND
b) nr raised ( I.e, nr > nr lim) AND
c) I) TSE ON and faulted in GCB open condition
OR ii) Stop command from SGC in SGC ON condition.
3 Tracking in synchronized condition if
a) Frequency within limit (adjustable, say 48.5 to 51.5 Hz.) AND
b) Load controller O/P , hr PC > hr nc AND
c) I) Load controller (L C) in control
OR ii)Pressure controller in action
4 Set Point Follow Up (Fast Calibration) during
a) Tracking condition 5 ( nr = n act + 21 RPM ) OR
b) Turbine Trip ( nr = n act - 120 RPM ). Simultaneously nr lim immediately equals to nr
Condition (a) ensures certain speed controller O/P during emergency to keep machine in rolled condition along with some load.
Condition (b) ensures negative speed controller O/P during Trip condition.
LOAD CONTROLLER (L C) IN CONTROL CONDITIONS -
a) Speed OR Pressure Controller not in action AND
b) Isolated Grid condition absent AND
c) Both Load Controller OFF and Schedule OFF absent (I.e, L C ON)
LOAD CONTROLLER SCHEDULE OFF - L C can be made OFF if Speed controller is in action and hrnc > hr PC. Otherwise, with OFF command OFF lamp blinks - called Schedule OFF
C .LOAD SET POINT GENERATION LOGICS
1TSE ON AND NOT FAULTED
This helps to keep stress effect for gradient control in service.
2-- LOAD GRADIENT ON
This helps to keep manual gradient control in service
3-- STOP POWER SET POINT CONTROL when
a) TSE ON and Faulted OR
b) Stop command from SGC OR
c) Pr raised when Pressure controller is in action with CMC ON OR Limit pressure mode selected OR Boiler follow mode selected
In above conditions Pr lim stops, I.e,Set point can not be increased.
4-- FAST CALIBRATION when
a) Pressure controller is in action OR
b) Follow above (h v0) condition present
Under this condition MW error (ep) is selected and Pr lim immediately equals to Actual load (P act) without any gradient .
5 -- FREQUENCY INFLUENCE ON
This is made ON from ATRS panel to put EXTERNAL FREQUENCY EFFECT in service for
loading / unloading w.r.t. 50 Hz ( with 2.5 % to 8 % Frequency Droop)
6 TSE TEST RELEASE : TSE TEST (For checking healthiness of TSE Margins) can be done when
a) TSE Influence is OFF OR
b) Both Pr, Pr lim and hr, hr lim are balanced, I.e, Speed and Power set point controls are not in action.
D .LOAD CONTROLLER LOGICS
FOLLOW ABOVE ( h v0 ) --
a) GCB closed and load < 10 % (station load) OR
b) GCB open OR
c) Load controller OFF
Absence of these conditions help Load controller output to track above Pressure controller output when Pressure controller is in service.
FOLLOW LOW ( h vu ) - GCB CLOSED AND Speed controller in action.
This helps Load controller output to track below Speed controller output.
8 -- Either a) Initial pressure mode selected OR
b) Turbine follow mode in action OR
c) CMC Runback active
This ensures Load controller output above pressure controller output
9 -- Load controller OFF
This defeats transmission of Load Controller output to Transfer circuit.
R & L - Raise & Lower command from UCB :
nr - Speed Reference :
nr limit - Delayed Speed Reference :
NLC - No Load Correction (Ensures required Speed controller O/P for Rolling even when Speed reference n r matches n act.)
n act - Actual Speed :
hr nc - Speed Controller O/P with DROOP of + / - 10.0 V for nr lim ~ n act = 150 RPM ( GAIN = 22
LOAD SET POINT GENERATION CIRCUIT
1 - SET POINT FOLLOW UP when Automatic Grid Control or CMC In service
(Other Raise / Lower commands get blocked)
2 -- TSE ENABLING when
A) GCB is closed AND
B) Load controller (L C) not OFF AND
C) Fast calibration signal 6 absent AND
D) I) Load controller (L C) in control
OR ii) Pressure controller with initial pressure in action
OR iii) Turbine follow mode in service
This helps to bring manually adjusted gradient and stress effect in service.
+/- 10 V gradient => +/- 25 MW / MIN for 200 MW units
OR +/- 50 MW / MIN for 500 MW units.
PRESSURE CONTROLLER CIRCUIT
EHC TRANSFER CIRCUIT
FGMO - BACKGROUND
n Unique frequency band of 49.0 Hz to 50.5 Hz, as specified by IEGC
n Scheduling & dispatch by RLDCs/SLDCs is based on day ahead demand & availability
n Frequency control by load-generation balance in every 15 mins time block
n Wide frequency variation during Grid disturbance, Unit outage, change in demand, etc.
n No primary response by generators to maintain frequency under such system contingency
n Emergencies caused due to frequency control only through importing /cutting load by system operator
n
FGMO - GRID CODES
n All generating units should have their speed governors in normal operation at all times to enable Grid frequency control by loading / unloading
n Droop characteristic for primary response should be within 3% to 6%
n Each unit shall be capable of instantaneously picking up at least 5% extra load for a minimum of 5 mins (up to 105%MCR), during fall in frequency
n No dead bands and/or time delays shall be deliberately introduced
n Facilities like load limiters, CMC, etc. shall not be used to suppress the normal governor action
IMPLEMENTATION OF FGMO
In line with clause Clause 1.6 of IEGC and CERC order dated 30-10-99, date of FGMO implementation, as decided by REBs are :-
n Western Region - 19-05-03 ( ABT - 01-07-02 )
n Southern Region - 01-08-03 ( ABT - 01-01-03 )
n Northern Region - 01-10-03 ( ABT - 01-12-02 )
n Nor-East Region - 22-12-03 ( ABT - 01-11-03 )
n Eastern Region - 02-01-04 ( ABT - 01-04-03 )
FGMO CHARACTERISTIC FOR KWU M/C
MAJOR ISSUES WITH FGMO IN 2004
Ø Wide and frequent variation of freq.
Ø Perpetual oscillations in critical parameters due to Boiler response time
Ø M/C subjected to cyclic loading and fatigue stresses
Ø Frequent HP/LP Bypass valve operation
Ø Continuous manual interventions
Ø Self-defeating feature(Unloading when freq. improving towards 50 Hz)
Ø Conflict with ABT(Offsetting freq. correction)
TRANSIENTS IN GOVERNING SYSTEM
n FAILURE OF POWER PACKS OF CONTROLLER RACKS IN EHC PANEL
n POWER SUPPLY FAILURE IN ATRS PANEL
n SIGNAL ACQUISITION PROBLEM
n FAILURE IN TURBINE SYSTEM
n ELECTRICAL SYSTEM FAILURE
n COMPONENT FAILURE IN GOVERNING RACK
n OPERATIONAL EMERGENCY
1 CONTROL RACK SUPPLY FAILURE
n M/C is on EHC. Power supply fails in Load control/Pressure control / transfer circuit rack. Starting device becomes off automatically due to EHC fault.
Observation: EHC output is minimum/zero and load minimum/ zero with EHC fault alarm. Machine on bar with ESV & IV open (Turbine not tripped).
Action: Confirm HP/LP bypass opening, isolate EHC from governing rack and parallely adjust starting device position from UCB. Reduce boiler firing to restrict rise in boiler pressure.
2) SUPPLY FAILURE IN ATRS PANEL(ATRS=Automatic Turbine Rolling & Synchronisation)
n M/C is on EHC. Power supply fails in CCA panels only.
Observation: All indication lamps in ATRS consoles will go off. EHC output and Load will become zero due loss of GCB close feedback. All ATRS drives will become inoperative.
Action: Confirm HP/LP bypass opening , isolate EHC. Reduce boiler firing. Adjust starting device position from local. Normalize power supply in CCA panels at the earliest.
3) SIGNAL ACQUISITION PROBLEM
n Loss of speed signal occurs due to Hall Probe / card failure.
Observation: Speed indication will become zero. M/C will be loaded through speed controller. Subsequently Pressure controller will come in service. AOP & JOP will take auto start & Barring Gear valve Will open on auto.
Action: Isolate EHC and adjust Starting device position. If pressure oil pressure is normal, make SLC of AOP, JOP and Barring Gear vlv OFF and stop AOP, JOP and close Barring Gear vlv.
4)FAILURE IN TURBINE SYSTEM
n Loss of speed signal occurs due to breakage of MOP shaft.
Observation: Speed indication and pressure oil pressure will come down. M/C will be loaded through speed controller and Pressure controller will come in service. Subsequently, AOP & JOP will take auto start &Barring Gear valve. will open on auto.
Action: Safe shutdown of M/C is to be ensured.
5) ELECTRICAL SYSTEM FAILURE
n M/C is on EHC with Tracking on. Starting device becomes inoperative due to Electrical module trouble/motor failure/overload.
Observation: During increase in boiler firing, Boiler pressure will increase due to load restriction by Starting device. EHC output will go to 100%.
Action: Switch off the electrical module of Starting device and increase Starting device position from local so that EHC can take control.
6) FAILURE IN GOVRRNING RACK
n EHC Plunger coil failure
n EHC Pilot valve bearing failure
Observation: EHC starts hunting
Action: Isolate EHC and take Hydraulic mode in service. Replace the failed omponent. Governing characteristic checking should be done before EHC is put in service
n Speeder Gear spring tension gets altered.
Observation: M/C may get unloaded at frequency lower than recommended value.
Action: Speeder Gear spring tension may be adjusted to increase the start of unloading.Testing for proper setting should be checked during suitable opportunity.
LOGICS
A SPEED CONTROLLER LOGICS
1 Command for slow rate at nr > 2850 RPM to facilitate easy synchronisation
2 TSE Influence ON, when min of all the upper stress margins comes into picture to control gradient of nr lim and hence, acceleration of Rolling speed. Upper stress margin = 30 deg C => 10.0 V => 600 RPM ~ (Acceleration < 108 RPM ~ causes dn / dt tripping)
B LOAD SET POINT GENERATION LOGICS
1 Stopping of nr lim when
a) GCB open AND
b) n act is < nr lim by approx. 45 RPM.
This restricts hr nc up to around 30 % during Rolling to avoid wide v/v opening.
2 Stopping speed set point control when,
a) n act > 2850 RPM AND
b) nr raised ( I.e, nr > nr lim) AND
c) I) TSE ON and faulted in GCB open condition
OR ii) Stop command from SGC in SGC ON condition.
3 Tracking in synchronized condition if
a) Frequency within limit (adjustable, say 48.5 to 51.5 Hz.) AND
b) Load controller O/P , hr PC > hr nc AND
c) I) Load controller (L C) in control
OR ii)Pressure controller in action
4 Set Point Follow Up (Fast Calibration) during
a) Tracking condition 5 ( nr = n act + 21 RPM ) OR
b) Turbine Trip ( nr = n act - 120 RPM ). Simultaneously nr lim immediately equals to nr
Condition (a) ensures certain speed controller O/P during emergency to keep machine in rolled condition along with some load.
Condition (b) ensures negative speed controller O/P during Trip condition.
LOAD CONTROLLER (L C) IN CONTROL CONDITIONS -
a) Speed OR Pressure Controller not in action AND
b) Isolated Grid condition absent AND
c) Both Load Controller OFF and Schedule OFF absent (I.e, L C ON)
LOAD CONTROLLER SCHEDULE OFF - L C can be made OFF if Speed controller is in action and hrnc > hr PC. Otherwise, with OFF command OFF lamp blinks - called Schedule OFF
C .LOAD SET POINT GENERATION LOGICS
1TSE ON AND NOT FAULTED
This helps to keep stress effect for gradient control in service.
2-- LOAD GRADIENT ON
This helps to keep manual gradient control in service
3-- STOP POWER SET POINT CONTROL when
a) TSE ON and Faulted OR
b) Stop command from SGC OR
c) Pr raised when Pressure controller is in action with CMC ON OR Limit pressure mode selected OR Boiler follow mode selected
In above conditions Pr lim stops, I.e,Set point can not be increased.
4-- FAST CALIBRATION when
a) Pressure controller is in action OR
b) Follow above (h v0) condition present
Under this condition MW error (ep) is selected and Pr lim immediately equals to Actual load (P act) without any gradient .
5 -- FREQUENCY INFLUENCE ON
This is made ON from ATRS panel to put EXTERNAL FREQUENCY EFFECT in service for
loading / unloading w.r.t. 50 Hz ( with 2.5 % to 8 % Frequency Droop)
6 TSE TEST RELEASE : TSE TEST (For checking healthiness of TSE Margins) can be done when
a) TSE Influence is OFF OR
b) Both Pr, Pr lim and hr, hr lim are balanced, I.e, Speed and Power set point controls are not in action.
D .LOAD CONTROLLER LOGICS
FOLLOW ABOVE ( h v0 ) --
a) GCB closed and load < 10 % (station load) OR
b) GCB open OR
c) Load controller OFF
Absence of these conditions help Load controller output to track above Pressure controller output when Pressure controller is in service.
FOLLOW LOW ( h vu ) - GCB CLOSED AND Speed controller in action.
This helps Load controller output to track below Speed controller output.
8 -- Either a) Initial pressure mode selected OR
b) Turbine follow mode in action OR
c) CMC Runback active
This ensures Load controller output above pressure controller output
9 -- Load controller OFF
This defeats transmission of Load Controller output to Transfer circuit.
How does the water kept in earthen pot becomes cool during summer?
Earthen pots are made of mud. Mud structures are porous and have microscopic cracks and crevices. When you pour water on the inside, water enters these cracks and crevices and wets the pot throughout. Now, look what happens to temperature. After about 20 minutes or so, depending on the size of earthen pot, the temperature of water and pot becomes same due to heat transfer. Now, let us look at the outside surface of the pot. This pot is now wetted by water from the inside, and hence the outer surface of the pot naturally contains water exposed to atmosphere. This water evaporate and carries along with it a certain amount of heat. By doing so, the pot is now a little cooler than before. Continued evaporation brings about a stable state, where the heat input to the water inside the pot is lost through the outer layer of the wetted earthen pot due to continued evaporation. If we want to increase the rate of cooling or further reduce the temperature, then cover the outer surface of the pot by thick cotton cloth or rag cloth and pour water on it. Hope this answers your question.
Read more: How_does_the_water_kept_in_earthen_pot_becomes_cool_during_summerEarthen pots are made of mud. Mud structures are porous and have microscopic cracks and crevices. When you pour water on the inside, water enters these cracks and crevices and wets the pot throughout. Now, look what happens to temperature. After about 20 minutes or so, depending on the size of earthen pot, the temperature of water and pot becomes same due to heat transfer. Now, let us look at the outside surface of the pot. This pot is now wetted by water from the inside, and hence the outer surface of the pot naturally contains water exposed to atmosphere. This water evaporate and carries along with it a certain amount of heat. By doing so, the pot is now a little cooler than before. Continued evaporation brings about a stable state, where the heat input to the water inside the pot is lost through the outer layer of the wetted earthen pot due to continued evaporation. If we want to increase the rate of cooling or further reduce the temperature, then cover the outer surface of the pot by thick cotton cloth or rag cloth and pour water on it. Hope this answers your question.
Read more: How_does_the_water_kept_in_earthen_pot_becomes_cool_during_summer
In the centrifugal casting process, molten metal is poured into a spinning die. The die can be spinning either on a vertical or horizontal axis depending on the configuration of the desired part. Ring and cylinder type shapes are cast vertically; tubular shapes are made with the horizontal centrifugal process. Either process may be used to produce multiple parts from just one casting.
Because of the high g-forces applied to the molten metal in the spinning die, less dense material, including impurities, "floats" to the I.D. where it is subsequently removed by machining. Solidification is managed directionally under pressure, from the O.D. to the I.D., avoiding any mid-wall shrinkage, leaving a defect-free structure without cavities or gas pockets.
Below in sources section is a link with a great deal of information on various castings
Depending on gearing selection and coupling selection there is no limit to the angular displacement between a drive shaft and a driven shaft. Belts chains and pulleys, along with gearing and cranks can be used to alter the direction of applied forces to any shafts. Universal direct connected drive joints, or PTO drives usually have an angular drive range of up to 45 degrees off centerline, while angular gearing can be used from 45 to 90 degrees (or more), and bull and pinion gears can reverse directions a full 180 degrees. Worm gears normally are fixed at 90 degrees.
