Term
Turbine
Describe the turbine trip signals. |
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Definition
-Moisture seperator high level (927'6") after 10 seconds.
-Turbine thrust bearing wear (30-35 mils).
-Rx high water level (+48").
-Turbine exhaust hood high temp (225F).
-High vibration (15mils).
-Generator negative sequence.
-Generator loss of field.
-Generator lockout (286/G).
-Generator loss of stator cooling.
-Main condenser low vacuum (20"Hg).
-Turbine low bearing lube oil (<19.2 psig) for .9secs.
-Emergency gov overseed set at 110%.
-B/U overspeed set at 112%. |
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Term
Turbine
Describe the turbine. |
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Definition
-One single flow high pressure section with 2 double flow low pressure section.
-Coupled to the generator, driven at 1800rpm to produce roughly 592 megatwatts. |
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Term
Turbine
Describe the flow sequence through the turbine. |
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Definition
-Through teh inlet control valves at generator end of high pressure turbine (6 rows) and exhausts at front of turbine casing.
-Through moisture seperators (water back to feedwater heater drain) and half of steam to A and half to B low pressure sections.
-Through the intermediate stop and intercept valves.
-Middle of each low pressure section to the end and exhausted to condenser.
-At points after high pressures section (5) extractions for feedwater heaters. |
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Term
Turbine
Describe low pressure hood casing protection. |
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Definition
| Relief diaphragm at 5 psig. |
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Term
Turbine
Describe turbine seal. |
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Definition
-Above 50% steam is supplied from the high pressure turbine seal leakoffs and valve stem leakoffs.
-Exhauster blowers maintain a neg press on the annulus to collect air and steam vapors.
-Condensed and discharge to condensate drip tank and off gas system
-Less than 50% regulated supplies 4 psig coming from bypass valve line. |
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Term
Turbine
Describe steam supply pressure at the low pressure turbines. |
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Definition
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Term
Turbine
Describe turbine bearings and cooling. |
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Definition
-10 journal bearings.
-Last 2 insulated to prevent shaft currents.
-Cooled by lube oil at 25psig to maintain 110-112F.
-1 thrust bearing with a bearing wear detector. |
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Term
Turbine
Describe the main stop valves and operation. |
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Definition
-Quick shutoff of steam in emergency or trip.
-Bypass valve to warm (only 1 of 4 has internal bypass).
-Loss of emergency trip oil causes main stops to shut.
-Interlock to prevent opening main stop valves unless bypass is fully open. |
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Term
Turbine
Describe the control valves and operation. |
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Definition
-Regulate the amount of steam to turbine.
-Controlled by turbine control mechanism on cam shaft. |
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Term
Turbine
Describe the intermediate stop and intercept valves and operation. |
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Definition
-Combo valve with 1 on each line supplying low pressure turbines.
-Protects the turbine from overspeed.
-Intercept valve shuts steam off from the crossaround.
-Intercepts tripped close by emergency trip syste.
-Intermediate stop provide second line of defence against stored energy in crossaround and moisture seperators.
-Tripped closed by emergency governor or master trip. |
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Term
Turbine
Describe the pre-emergency device and acceleration device. |
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Definition
-Rejection of full load, teh acceleration device and relay cause control valves to close sooner than norm governor ops.
-Trip mechanism actuates at 190psig and resets at 172.5psig tip oil pressure. |
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Term
Turbine
Describe the vacuum trips. |
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Definition
-Trips at 20"Hg to protect main condenser.
-Second trip at 9.2"Hg to protect turbine exhaust hoods.
-This trips only bypass valves.
-Low vacuum alarm at 24".
-Low vacuum scram at 22.3". |
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Term
Turbine
Describe exhaust hood spray. |
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Definition
-Spray water from condensate sprays when control valve mechanism is less than 15% of rated.
-Exhaust hood high temp alarm is 175F. |
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