steam path audit of steam turbine

8/10/2019 Steam Path Audit of Steam Turbine

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encotechencotech, Inc .

Steam Path Audit


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Overview

What is a Steam Path Audit (SPA)?Objective & Benefits

Chronology of a Steam Path Audit

DamageA Case study


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What is a Steam Path Audit?

A detailed inspection of the stationary and rotatingsteam path components

An accounting of performance losses on a stage-by-stage basis

An accounting of performance losses on acomponent-by-component basisA presentation of losses in power and heat rate


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Impulse Blading

DIAPHRAGM

TIPSPILL STRIPS

BALANCE HOLE

WHEELPACKING

SHAFT

STEAM FLOW

ROOTSPILL STRIPS

ROTATINGBLADE

STATIONARYBLADE

SHELL

PRESSURE

DOVETAIL

INTERSTAGE PACKING LEAKAGE

BALANCE HOLE

FLOW

ROOT LEAKAGE

TIP

LEAKAGE

COVER OR

SHROUD

TENON

BOWL

PRESSURE


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The specific areas of concern addressedby the audit are:

1) Leakages:- past stationary stage blading- past rotating stage blading- past shaft end packings where

rotors emerge from casings- across poorly fitting joints- other miscellaneous leakages

3) Flow blockages from:- deposits- foreign objects- mechanical damage

2) Surface finish degradation:- deposits- corrosion- solid particle erosion

- mechanical damage

4) Flow path modificationfrom:

- solid particle erosion- water droplet erosion

- mechanical damage


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Objective of a SPA

The objective of the audit is to assessthe condition of the turbine steam pathto identify degradation in thermalperformance of the unit and to point outthe cause and location of power andefficiency losses.


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Benefits of a SPA

Provides detailed inspection of steam path

Quantify heat rate, power and efficiency impact oncomponent-by-component basis

Aid economic decisions during the repair outage

Prioritize maintenance decisions on a benefit-to-cost ratio

Quantify the quality of turbine repairs by performing aclosing steam path audit

Provides excellent record/history of equipment condition forfuture reference


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The Outage Time-Line

TURBINE OUTAGE

Shutdown Startup

Pre-Outage Test Opening SteamPath Audit

Closing SteamPath Audit

Upgrade andMaintenance

Post-OutageTest

Disassembly Reassembly


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Results

Quantification of losses measured in pre-outagetestQuality check on maintenance performed duringthe outagePerformance improvement resulting from individualmaintenance actionsExpected return-to-service performance


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Dec, 2006 STEAG/STEAM PATH AUDIT

Chronologyof aSteam PathAudit


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Computer Model

Create turbine model at STEAGs office using theThermal Kit

Design heat balance (VWO)Turbine cross section

Clearance and steam seal system diagramFirst stage shell pressure curve


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Coordinate Activities

Coordinate activities with ownerPlan around grit blasting schedule

Place upper half of casing w/ horizontal joint up or layon ground w/ trailing edges up

Leave all packing (interstage & shaft end) in place until

measured. This speeds SPA process significantlyAll stages must be inspected prior to grit blasting


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Sequence of Events

Inspect casing horizontal joint for leakage paths

Measure blade geometry

Measure packing teeth, interstage, tip, root, and &shaft end

Create a photographic record of the steam path

Geometric data for the steam path must beobtained to properly model turbine


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Solid Particle Erosion


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Mechanical Damage


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Cover Deposits


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Foreign Object Damage


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Flow Path Damage


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Surface Roughness

encotechencotec h, Inc .


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Surface Roughness


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Root Cracks


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Tip Spill Strip


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Clearance Measurements


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Surface Roughness


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Geometry Measurements


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Dec, 2006 STEAG/STEAM PATH AUDIT

INDIANEXPERIENCE

A Case Study


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TYPICAL 200 MW

Commissioned in the year 1984

Tandem compound two flow LP steam turbine

HP/IP an opposed flow design

Output 206,260 kW at VWO conditionInitial steam conditions

Pressure 14710 kPa, Temp. 535/535 deg C

Exhaust Pressure 10.49 kPa

Shaft speed 3000 rpm

Total thirty three stages, Six Extractions


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Preliminary Observations

HP CasingSevere Flow Path Damage on stages 2, 3, and 4Tip, Root, and Interstage Packings rubbed

IP CasingSevere Flow Path Damage on stages 11, and 12Tip, Root, and Interstage Packings rubbed

LP CasingTip, and Interstage Packings rubbedSlant End Packings severely rubbed


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Change in Power by Category Total All Casings

1447.4

4795.3

2740.42506.6

3477.5

4177.8

0

1000

2000

3000

4000

5000

6000

7000

I n t e r s

t a g e

P a c

k i n g s

T i p

S p

i l l

S t r i p s

E n d

P a c

k i n g s

M i s c e l

l a n e o u s

L e a

k a g e s

F l o w

P a t

h

D a m a g e

F l o w

C h a n g e

I m p a c

t

S u r f a c e

R o u g h n e s s

C o v e r

D e p o s i

t s

H a n

d

c a l c u

l a t i o n s

T r a i l i n g

E d g e

T h i c k n e s s

P o w e r

L o s s

( k W )

CLOSING

AUDIT

260.2

4570

282.4

1975.3 2077.8

6738.2

3241.1

0

1000

2000

3000

4000

5000

6000

7000

I n t e r s

t a g e

P a c

k i n g s

T i p

S p

i l l S t r i p s

E n

d P a c

k i n g s

M i s c e

l l a n e o u s

L

e a

k a g e s

F l o w

P a

t h

D a m a g e

F l o w

C h a n g e

I m p a c

t

S u r f a c e

R o u g

h n e s s

C o v e r

D e p o s

i t s

H a n

d

c a

l c u

l a t i o n s

T r a

i l i n g

E d g e

T h i c k n e s s

R e c o v e r y

P o w e r

L o s s

( k W )

OPENING

AUDIT


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Power Loss by Casing

10499.3

1928.6

1123.61415.8

0

2000

4000

6000

8000

10000

12000

HP IP LP Gov LP Gen

P o w e r

L o s s

( k W )

CLOSING

AUDIT

OPENING

AUDIT

6495.5

1023.9 843.4 802.9

6738.2

0

2000

4000

6000

8000

10000

12000

HP IP LP Gov LP Gen Recovery

P o w e r

L o s s

( k W )


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Change in Power by Category HP Casing

669.8

4270.6

1300.6

1630.7

2627.5

0

1000

2000

3000

4000

5000

I n t e r s

t a g e

P a c

k i n g s

T i p S p

i l l

S t r i p s

E n d

P a c

k i n g s

M i s c e l

l a n e o u s

L e a k a g e s

F l o w

P a t

h

D a m a g e

F l o w

C h a n g e

I m p a c

t

S u r f a c e

R o u g

h n e s s

C o v e r

D e p o s i

t s

H a n

d

c a l c u

l a t i o n s

T r a i l i n g

E d g e

T h i c k n e s s

P o w e r

L o s s

( k W )

120.5

4003.73992.1

1083.81037.0

262.1

0

1000

2000

3000

4000

5000

I n t e r s

t a g e

P a c

k i n g s

E n d

P a c

k i n g s

F l o w

P a t

h

D a m a g e

S u r f a c e

R o u g

h n e s s

H a n

d

c a l c u

l a t i o n s

R e c o v e r y

P o w e r

L o s s

( k W )

CLOSINGAUDIT

OPENINGAUDIT


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355.4

41.8

1206

-639.9

965.3

-1000

-500

0

500

1000

1500

2000

I n t e r s

t a g e

P a c

k i n g s

T i p S p

i l l

S t r i p s

E n

d P a c

k i n g s

M i s c e

l l a n e o u s

L e a k a g e s

F l o w

P a t

h

D a m a g e

F l o w

C h a n g e

I m p a c

t

S u r f a c e

R o u g

h n e s s

C o v e r

D e p o s i

t s

H a n

d

c a l c u

l a t i o n s

T

r a i l i n g

E d g e

T h i c k n e s s

P o w e r

L o s s

( k W )

Change in Power by Category IP Casing

-527.3

904.7

17.0

591.2

938.3

4.6

-1000

-500

0

500

1000

1500

2000

I n t e r s

t a g e

P a c

k i n g s

E n

d P a c

k i n g s

F l o w

P a

t h

D a m a g e

S u r f a c e

R o u g

h n e s s

H a n

d

c a

l c u

l a t i o n s

R e c o v e r y

P o w e r

L o s s

( k W )

CLOSINGAUDIT

OPENINGAUDIT


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Change in Power by Category LP Gen Casing

195.8

751.5

60.60

407.9

0

200

400

600

800

1000

I n

t e r s

t a g e

P

a c k i n g s

T i p S p

i l l

S t r i p s

E n d

P a c

k i n g s

M i s c e l

l a n e o u s

L e a k a g e s

F l o w

P a t

h

D a m a g e

F l o w

C h a n g e

I m p a c

t

S

u r f a c e

R o u g

h n e s s

C o v e r

D e p o s i

t s

H a n

d

c a l c u

l a t i o n s

T r a i

l i n g

E d g e

T h i c k n e s s

P o w e r

L o s s

( k W )

7.0

612.9

153.4

575.2

67.4

0

200

400

600

800

1000

I n

t e r s

t a g e

P a c

k i n g s

E n d

P a c

k i n g s

F l o w

P a t

h

D a m a g e

S u r f a c e

R o u g

h n e s s

H a n

d

c a l c u

l a t i o n s

R e c o v e r y

P o w e r

L o s s

( k W )

CLOSINGAUDIT

OPENINGAUDIT


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Change in Heat rate by Category Total All Casings

CLOSINGAUDIT

OPENINGAUDIT

45.72

116.55

63.03

424.11

32.97

110.56

55.28

0

100

200

300

400

I n t e r s

t a g e

P a c

k i n g s

T i p S p i

l l S t r i p s

E n d

P a c

k i n g s

M i s c e l

l a n e o u s

L e a k a g e s

F l o w

P a t

h D a m a g e

F l o w

C h a n g e

I m p a c t

S u r

f a c e

R o u g h n e s s

C o v e r

D e p o s

i t s

H a n

d c a

l c u l a t

i o n s

T r a

i l i n g

E d g e

T h i c k n e s s

T o t a l

l o s s

R e c o v e r y

G . T . H . R

L o s s

( k J / k W h )

8.17

112.37

6.69

43.45 63.63

245.53

178.58

11.22

0

100

200

300

400

I n t e r s

t a g e

P a c

k i n g s

T i p S p i

l l S t r i p s

E n d

P a c

k i n g s

M i s c e l l a n e o u s

L e a k a g e s

F l o w

P a t

h D a m a g e

F l o w

C h a n g e

I m p a c t

S u r

f a c e

R o u g h n e s s

C o v e r

D e p o s

i t s

H a n

d c a

l c u l a t

i o n s

T r a i l

i n g

E d g e

T h i c k n e s s

T o t a l

l o s s

R e c o v e r y

G . T . H . R

L o s s

( k J / k W h )


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Heat rate loss by Casing

CLOSING

AUDIT

OPENING

AUDIT

241.5

55.4 44.8 56.5

424.1

0

100

200

300

400

HP IP LP Gov LP Gen Total loss Recovery

G . T . H . R L

o s s

( k J / k W h )

146.3

24.0 33.6 31.9

245.5

178.6

0

100

200

300

400

HP IP LP Gov LP Gen Total loss Recovery

G . T . H . R

L o s s

( k J / k W h )


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steam path audit of steam turbine

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