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Systems > Moisture Separators Reheaters (MT) > Flashcards

Moisture Separators Reheaters (MT) Flashcards

1
Q

What is the purpose of the MSRs ?

A

-Used to improve quality of HP turbine exhaust before going into LP Turbine
-Improves plant efficiency & longer LP turbine life

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2
Q

How do the MSRs work ?

A

-Mechanically remove moisture & reheats dry steam passing across 1st & 2nd stage reheater tubes
-This minimizes erosion in LP turbine bucket & momentum losses

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3
Q

What steam is used for the MSR 2nd stage reheating ?

A

Main steam provides heating for second stage

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4
Q

What is aux steam used for on the MSRs ?

A

It’s used for steam blanketing of the MSRs

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5
Q

How does the Moisture Separator Section work of the MSR ?

A

Goes through chevron canes that puts wet steam through changes in direction, which causes heavy droplets from steam flow

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6
Q

What happens once dry steam flow exits moisture separator panels ?

A

Steam flow is reheated by tube bucndle s

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7
Q

Where does MSR Drain Tank drain to ?

A

Has level controller that directs tank discharge to either HTR Drain Tank or to Main Condenser on HI-HI Level

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8
Q

What happens if MSR vessel water backs up to within 3 inches ?

A

-Turbine trip initiates to prevent water induction in the turbine
-3level switches for 2/3logic

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9
Q

What does the Reheater Section do inside the MSR ?

A

-Supplied with heating steam that heats dried steam to superheater conditions
-Superheater steam is then directed to LP Turbine

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10
Q

Where is the 1st stage reheater receive its steam from ?

A

Receives steam from 3rd stage extraction line

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11
Q

What does the 2nd stage reheat require ?

A

Requires control system because it taps off upstream of turbine throttle valve & is therefore at main steam temp & pressure

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12
Q

Where does the 1st stage heater condensate drain to ?

A

Drains to 1st stage drain tank that drains to:
- #6 HPFWH
-Main Condenser on HI-HI lvl in tank

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13
Q

Where does the 2nd stage heater condensate drain to ?

A

It drains to the 2nd Stage Drain Tank which then drains to:
-#7HPFWH
-Main Condenser on HI-HI lvl in tank

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14
Q

What is the purpose for the MSR Drain Tank ?

A

-Collection point for moisture that was removed from HP Turbine exhaust
-Each MSR has one MSR Drain Tank

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15
Q

Where do the two MSR Drain Tank level control valves drain to ?

A

-Normal level control valve drains to to HTR Drain Tank
-High level control valve drains to Main condenser

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16
Q

What is the position of the MSR Drain Tank level control valves during start up ?

A

Startup will have Normal level control valve closed, & High level control valve will be opened

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17
Q

When less than 10% power what is the status of the MSR Drain Tank level control valves ? What happens when turbine power is greater than 10%?

A

-High level dump valve is failed open
-High level dump valve will go close & Normal level control valve will maintain level

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18
Q

What happens if MSR Drain Tank level has a continuous rise in level ?

A

-High level dump valve will modulate open to condenser
-If level continues to rise to MSR 3in setpoint, a main turbine trip initiates

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19
Q

What happens to the MSR Drain Tank level control valves on loss of instrument air ?

A

-Normal level control valve will fail closed
-High level dump valve will open

20
Q

What happens to the MSR Drain Tank level control valves on a HI-HI lvl?

A

Normal level control valve will fail closed

21
Q

Why does 3rd stage extraction used for 1st stage steam supply have acceptable rates of temperate changes ?

A

3rd stage extraction, temperature, and pressure of steam supplied 1st stage reheaters varies in turbine load

22
Q

How is the steam supply to 1st stage bundle of the MSR isolated ?

A

Isolated by Motor Operated Reheat Stop Check Valve, operated from Control Room

23
Q

What is the difference between the 1st & 2nd stage reheat steam supplied ?

A

-HP 3rd stage extraction is self regulating for the 1st stage reheat
-Main Steam needs a regulation when being supplied to 2nd stage of MSR

24
Q

How is the steam supply to the 2nd stage bundle isolated ?

A

Isolated by Reheating Steam Source Valves(RSSV)

25
Q

What valves are used to regulate the main steam pressure supplying the 2nd stage reheat steam for MSR ?

A

-Reheat Steam Low Load Valve(RSLLV)
-Motor Operated Reheat Steam High Load Valve (RSHLV)

26
Q

What do the low load valve & high load valves do for the main steam supply to the 2nd stage reheat ?

A

Work together to regulate steam pressure with MSR & LP Turbine operational limits

27
Q

What is the 2nd stage reheater supply pressure adjustments based on ?

A

-Control system adjusted 2nd stage pressure based on Turbine cross around piping
-Varies over desired load range & ensure temperature rate of change limitation are maintained

28
Q

During startup when is the 1st stage reheater bundle placed in service ?

A

When turbine is at rated speed & minimum load 1st stage reheater bundle is placed in service

29
Q

What’s the status of the 1st stage Drain Tank level control valves when there is low steam flow ?

A

-Normal control valve is closed

-High level control valve opened to ensure proper draining & no moisture buildup in reheater tube bundle

30
Q

What happens to the 1st stage drain tank level control valves when turbine load is raised above 10% load ?

A

-High level dumb valve will auto close
-Normal control valve will begin to open

31
Q

Where is turbine load sensed ?

A

Sensed at inlet to the LP ‘A’ Turbine

32
Q

What happens to 2nd stage drain tank high level dump valves when turbine load is less than 20% ?

A

2nd stage drain tank high level dump valve will fail open

33
Q

What happens to 2nd stage drain tank high level dump valve when turbine load rises above 20% ?

A

-High level dump valve will close
-Normal control valve will open to maintain level

34
Q

How does the MSR Steam Scavenging work ?

A

Prevents condensate buildup in the the piping, which could cause thermal expansion in reheater stages

35
Q

How does Steam Scavenging work on the MSR system ?

A

-Orifice lined on vent line is connect to same HPFWH as the associated Drain Tank
-HPFWH is lower pressure than reheater which causes excess steam flow that sweeps condensate from tubes

36
Q

How much additional steam flow does the Steam Scavenging provide ?

A

Provides additional 10% of steam flow on top of flow that performs actual stage heating

37
Q

Why is air purging important for the reheater tube bundles ?

A

-Important to evacuate air from bundles prior to admission of steam
-This ensures uniform heating as bundles pressurize

38
Q

How does the air purging of the reheater bundles work ?

A

Removes air from bundles & places to condenser vacuum

39
Q

Why is it important to prevent sustained steam flows to condenser?

A

Impinges condenser tubes & can cause damage

40
Q

What would happen if steam were admitted to an unpurged reheater bundle ?

A

Top half of bundle would heat up first & then bottom half, which could cause differential expansion causing tube failure

41
Q

When is air purging performed?

A

Performed prior to admitting reheat steam or steam blanketing

42
Q

How does the Drain Tank high level control valve help during the purging process ?

A

High level dump valve will be open draining tank exposing bundles to condenser vacuum

43
Q

Where is MSR Steam Blanketing supplied from ? What is it used for ?

A

Supplied from Aux Steam & used to prevent corrosion of tubes by keeping air out

44
Q

What must be done to MSR drain flow paths during steam blanketing ?

A

-Vent steam scavenging valves are BOTH closed
-Drain Tank Drain Valves are closed

45
Q

What is the blanketing steam temperature maintained at? Where is small amount of condensate directed to during steam blanketing process?

A

Maintained 300F & any condensate during process drain to reheater drain tank

Systems (62 decks)

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