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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
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.
What is surging in axial compressors?
Surge is defined as the operating point at which the compressor peak head capability and minimum flow limit are reached. The compressor loses the ability to maintain the peak head when surge occurs and the entire system becomes unstable. Under normal conditions, the compressor operates to the right of the surge line. However, as fluctuations in flow rate occur, or under startup / emergency shutdown, the operating point will move towards the surge line because flow is reduced. If conditions are such that the operating point approaches the surge line, the impeller and diffuser begin to operate in stall and flow recirculation occurs. The flow separation will eventually cause a decrease in the discharge pressure and flow from suction to discharge will resume. This is defined as the surge cycle of the compressor.
The surge cycle will repeat itself unless control systems are installed or operational changes are made to bring the compressor out of the surge cycle. The surge cycle may result in a small or large flow reversal period depending on the discharge gas volume and the pressure ratio. Chronic surge is characterized by intermittent periods of small flow reversal that may not cause severe damage to the machine. Acute surge is more pronounced, usually due to a rapid transition across the surge line. Any surge event can cause severe damage to the thrust bearings, seals, and the impeller.
Why is friction an important force?
friction is an important force to have in life because friction helps objects that move or roll stop. Like brakes on a car, when you push down on the brakes the friction is there when the wheels stop,and the car will stop to.
What is the relationship between bending and strain?
From the Hooke law, stress s is proportional to strain e; s = Ee where E is elastic modulus of the material; the stress is the bending stress which varies from plus on one surface to minus on the opposite surface.
How many meters of water is 1 bar?
P=rho*g*h
P= pressure
rho= density = 1000 kg/m^3 at about 20C
g= gravitational constant on earth at sea level = 9.81 m/s^2
h= height
P=1 bar=1x10^5 Pascals = 1x10^5 N/m^2 (based on the definition of the Pascal unit)
since by definition 1 Newton= 1 kg*m/s^2
1x10^5 N/m^2= 1x10^5 kg*m^2/(m^3*s)= 1x10^5 kg/(m^2*s)
1x10^5 kg/(m^2*s) = 1000 kg/m^3 *9.81m/s^2 * h
solving for h yields:
h= 1x10^5/(1000*9.81)= 10.19367 meters
This value might vary slightly due to the affect of temperature on the density of water.
What skills are necessary for mechanical engineering?
Mechanical engineers need to be:
- adaptable
- creative
- practical
- patient and persistent
- accurate, with an eye for detail
- able to work well under pressure
- able to work well independently and in a team.
your answer here...
How many wheelbarrows of cement sand and gravel in a cubic meter of concrete?
35 to 70
It depends on the mix of concrete you are using. A basic 1-2-3 mix is 5 1/2 cubic feet of portland cement (a wheelbarrow, depending on its size, holds 1/2 to 1 cubic feet), 11 cubic feet of sand, and 16 1/2 cubic feet of stone (called aggregate) from 1/2 to 1 inch in size each. To this is added about 12-15 gallons of water.(1 1/2 to 2 cu.ft.). This will make just a little less than 1 cubic meter of concrete.
A weaker mix for basic work not needing structural strength a 1-2-3 mix of 1 part stone, 2 parts cement and 3 parts sand can be used, this would require a bit less than 1 part water.
A stronger mix of 1 part cement, 1 1/2 parts sand and 3 parts stone with about 1/2 part water is good for heavy duty concrete work. Stone will increase the strength of concrete and sand will weaken it. Using too much or too little water in the mix will weaken it as well. Additionally, concrete with too much water or too little cement tends to shrink and crack as it sets. The amount of water to use is mainly dependent on the cement in the mix. There should be at least half as much cement as sand in any mixture. The amount of stone to use should be between 1/4 and 3/4 of the total mixture. Grouts and mortars use no stone and may add limestone as an additional binder. These should not be used for structural concrete, but can be used for foundation pointing, bolt anchoring or mortaring brickwork.
Why we need biomedical engineering?
The application of engineering knowledge to the development of medical products. The engineering disciplines involved range from the traditional engineering fields to software and genetic engineering. The field is broken up into a number of specialty areas as varied as the biological and engineering fields from which they spring.
What is main steam stop valve?
Used in power generation. When steam turbine is on-line the Main Steam Stop Valve is fully open. When offline it is closed. Steam to turbine is controlled thru control valves after Main Steam Stop Valve
it is extruded through a mold. metal pipe is poured semi molten through a mold and forced out the other side. plastic is molten and forced thru a mold as well. there used to be a play-doh machine that would make a play-doh tube. then you could see how it's done.
Difference between reverse engineering and re engineering?
Reverse engineering is when you have an existing item and you strip it down to see how it's made so that you can copy it and make more.
Reengineering is a term applied to altering the practices and/ or methods of a company or a business - it's not something that engineers do. It's, essentially, technobabble talk for "changing the way the company does things".
What is the difference between pipe and tube fittings?
Pipe is identified by NB and thickness is defined by Schedule whereas Tube is
identified by OD.
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What is the main difference between an electric motor and electric generator?
An electric generator converts mechanical energy to electric energy while a motor converts electric energy to mechanical. A generator can actually act as a motor if it losses whatever is making it spin (called "motoring"), which is usually a very bad thing. Motors may be used as generators as well, depending on their design.
What is screw thread micrometer?
This is a tool that is used to measure the pitch diameter of a screw. This tool looks like a standard micrometer except that the anvils are specially configured to reach into the screw thread groove and touch the pitch diameter of the screw thread. The screw thread micrometer does not measure any other aspect of the screw thread. It does not measure the: pitch; threads-per-inch; major diameter; minor diameter; flank angles; lead; helix angle.
How do you find modulus of elasticity from load-displacement curve?
The modulus of elasticity is a property specific to a given material and in practice is derived through laboratory testing.
The modulus of elasticity is defined as stress/strain. One would have to apply a force uniformly over a known cross section of a material and monitor the strain utilising strain gauges. When the results are plotted you will notice that you get elastic behaviour up to a point of yield (this is known as the yield stress in normal carbon steels, however in stainless steel where the yield point is not as defined, we normally accept it to be the 0.2% strain) and the material should behave linearly in this area. If you take the gradient of the stress/strain, this will be your Elastic modulus.
Please note that the plotted curve will begin to flatten off roughly at the 0.2% strain line and this is due to the fact that the material has yielded. even after this point the material will not fail but will act 'plastically' up to a point where the material fractures which we call the ultimate stress.
What is the operation of an air condition?
A window air conditioner is designed to accommodate the compact space of a window frame. It has compressor unit, expansion valve, cold and hot coil, a filter, a control unit, thermostat, a set of fans and refrigerants also known as freons.
The units compressor compresses the refrigerant. It turns into a hot, high pressure gas that goes through a series of coils. This process dissipates the heat, and the refrigerant condenses into liquid form. In this phase, it runs through an expansion valve, evaporating and becoming a cooled low-pressure gas. Now it goes through another series of coils, absorbing heat and causing air to become cool. A window unit has fans to blow air over both sets of coils. The helps them retain heat to outside air and coolness to the indoors.
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What is the difference between fire fighting pump and fire water pump?
Not a lot. A fire fighting pump found on most fire engines is the centrifugal type. Other than the amount of water it may flow and the number of discharges it can supply, there is no difference (although I'm not sure what "ordinary centrifugal pump" refers to unless it is a trash or sump pump). Centrifugal type pumps weren't always used in the fire service, but they are the standard now because they can spin (they can pump or maintain pressure) even when there is no water actually flowing.
