Quantifying Cycle Isolation Losses and Integration with On Line Systems Feedwater System Reliability Users Group 2015 Meeting San Antonio Ken Porter Rich.

Quantifying Cycle Isolation Losses and Integration with On Line Systems

Feedwater System Feedwater System Reliability Users GroupReliability Users Group

2015 Meeting2015 Meeting

San Antonio San Antonio

Ken PorterKen Porter

Rich DugganRich Duggan

Frank ToddFrank Todd

Condenser

Leakage Flow

LeakingValve

High Pressure High Temperature

Agenda Introduction - Why Bother? Approach Calculation Program Process Application of Program Output to Plant Computer Example of Results Case Study

Introduction – Why Bother? Generating plants often suffer

from power losses due to leakages through valves that are faulty and/or do not seat correctly.

Often these losses are significant but have been difficult to quantify.

Many of the existing methods over predict the flow or can only generally predict (high medium or low flow)

High Pressure/High Temperature

Leaking Valve

Condenser

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Value of Leaking Valves

How Much is 1 MW of electricity worth? Revenue

If the plant can’t make it, they can’t sell it (Combined Cycle, Nuclear, Fossil plants operation at their boiler thermal limits)

Hrs/Year * Capacity Factor * Replacement Cost = Cost per Year 8760 MWh/Yr * 0.92 * $50/MWh = $402,960 (not small change)


Data Source: Data Source: US Energy Information AdministrationUS Energy Information Administration

http://www.eia.gov/

$-

$50,000

$100,000

$150,000

$200,000

$250,000

$300,000

$350,000

$400,000

1 2 3 4 5 6 7 8 9 10 11 12

Months with leak in place

Total Additional Fuel Cost Lost Revenue

1 MW lost1 MW lost


Typically plants have between 2-6 MW of lost generation from leaking valves

For a plant that can not make up this loss, this represents $800,000 - $2,400,000 annual lost revenue.

For a plant that can make it up, it represents additional fuel costs of $500,000-$1,500,000

The longer the leak the more extensive the damage It is often difficult to figure out which valves to fix

HP TURBINE

LP TURBINE

MSR

FEEDWATER HEATERS

GENERATOR

COOLING TOWER

CONDENSER

REACTOR COOLANT

PUMP

FEED PUMP

CIRCPUMPBLOW-

DOWN

MAINSTEAM

FEED WATER

COOLING WATER SYSTEMTURBINE CYCLE

NUCLEAR STEAM SUPPLY SYSTEM

STEAM GENERATOR

REACTOR VESSEL

CORE

Qr

Prioritization-Value of Leaking Valves

Source: Source: Evaluating Steam Turbine PerformanceEvaluating Steam Turbine Performance by K.C. Cotton by K.C. Cotton

Data from Ken Cotton Book page 303

A Solution Estimating losses from

these leaking valves can be done with advanced leakage calculations expect accuracy +/- 10%

to +/- 30% depending on conditions.

Every valve is different and needs to be modeled individually


Leaking Valve

Condenser

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Approach

Develop model for each valve Calculate flow rates and heat rate effect using TP-Plus

CIM software Develop equations for leakage and heat rate effects based

on software results.

Implement equations using OSIsoft® PI or other on-line software

Calculation Program Process

Uses temperature downstream of valve to determine pressure. Actual method is based on steam conditions (saturated vs

superheated) Calculates flow based on a series of equations

Grashofs ASME Figure 14 Darcy-Weisbach equation Sonic Flow Equation Choke Flow Equation

(Plant Engineering: Heat Cycle Isolation Valve Leakage Identification and Quantification [1025264 ])

Calculation Program Process Correct for equivalent length (including elbows and other

restrictions)

Account for problematic areas

Valve too close to sink

Valve discharges into a header

Valve has other heat sources downstream Bypass around air, hydraulic motor operated valve

Steam trap bypass

Other valves discharge into downstream of valve

Bound maximum flow based on valve/pipe size


Leaking Valve

Condenser

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TL

P

Difficult Areas to MonitorDifficult Areas to Monitor

Difficult Areas to MonitorDifficult Areas to Monitor

Calculation Program Process Model leakages in thermodynamic modeling software to calculate

Loss Factor (LF) Loss Factor will account for the overall effect of the leakage flow on the

cycle. Convert leak rate to Heat Rate or effect on Electrical Output

Calculate generation lost due to leak:

LFhh

QMW condenserupstreamloss

3412140

The Heat rate effect can be determined by converting the lost generation (LG) to heat rate using the Nominal heat rate and the nominal gross generation.

kwhbtuMWGen

HRHRE loss /

MW / BTU Constant

Plant Computer Process Establish temperature limit based on evaluation of

temperature measurement location. Using TP Plus CIM model the valve leakages across the

range of expected temperatures Condenser saturation temperature through upstream temperature

Develop polynomial equation from temperature to leakage relationship (Q)

Program polynomial in monitoring center or data historian If Td > Tlimit, then Q = A Td

3 + B Td2 + C Td + D

If Q > Qmax, then set Q = Qmax

Plant Computer Process Develop polynomial equation from leakage to heat rate

relationship Or using equations calculate the heat rate effect based on

polynomial results for leakage (more accurate for off load conditions and changes in condenser pressure)

Program polynomial for heat rate or program equations for calculating the effect from the determined leakage

Program special cases, e.g., in the case of two valves discharging to the same pipe - where the calculation is initiated based on a temperature near the valve but is based on a temperature further down stream.

Calculated Main Steam Valve Leakage

0

5000

10000

15000

20000

25000

30000

100 200 300 400 500 600 700 800 900

Downstream Temperature (deg F)

Lea

kag

e F

low

(lb

m/h

r) Method 1

Method 2

Method 3

Method 4

Method 5

y

ExamplesParameter Value Unit

Pipe ID 1.5 in

Limit Temp 200 deg F

Upstream Pressure 2415 psia

Upstream Temp 1000 deg F

Condenser Pressure 3.5 in Hg

Upstream Enthalpy (calculated) 1460.4 btu/lbm

Main Steam Valve

ExamplesPolynomial for Main Steam Valve Leakage

y = 0.00024x3 - 0.26283x2 + 115.02241x - 14947.39271

R2 = 0.99725

0

5000

10000

15000

20000

25000

30000

100 200 300 400 500 600 700 800 900


Lea

kag

e F

low

(lb

m/h

r)

y

Calculated HP Exhaust Valve Leakage

0

1000

2000

3000

4000

5000

6000

100 200 300 400 500 600 700


Lea

kag

e F

low

(lb

m/h

r) Method 1

Method 2

Method 3

Method 4

Method 5

y


Pipe ID 1.5 in


Upstream Pressure 440 Psia




HP Exhaust Valve

Polynomial for HP Exhaust Valve Leakage

y = 0.00006x3 - 0.05040x2 + 26.17907x - 3728.01050

R2 = 0.99992

0

1000

2000

3000

4000

5000

6000

100 150 200 250 300 350 400 450 500 550


Lea

kag

e F

low

(lb

m/h

r)

y

Examples

Calculated IP Exhaust Valve Leakage

0

100

200

300

400

500

600

700

800

100 150 200 250 300 350 400 450 500 550


Lea

kag

e F

low

(lb

m/h

r) Method 1

Method 2

Method 3

Method 4

Method 5

y


Pipe ID 1.5 in


Upstream Pressure 68 Psia




IP Exhaust Valve

ExamplesPolynomial for IP Exhaust Valve Leakage

y = -0.00001x3 + 0.01364x2 - 2.97839x + 188.83734

R2 = 0.99824

0

100

200

300

400

500

600

700

800

100 150 200 250 300 350 400 450 500


Lea

kag

e F

low

(lb

m/h

r)

y

Calculated 1st LP Extraction Valve Leakage

0

50

100

150

200

250

300

350

100 150 200 250 300 350 400 450


Lea

kag

e F

low

(lb

m/h

r) Method 1

Method 2

Method 3

Method 4

Method 5

y


Pipe ID 1.5 in


Upstream Pressure 37.6 Psia

Upstream Temp 462.7 deg F



First LP Extraction Valve

ExamplesPolynomial for 1st LP Extraction Valve Leakage

y = -0.00002x3 + 0.01734x2 - 3.64652x + 217.45892

R2 = 0.99966

0

50

100

150

200

250

300

350

100 150 200 250 300 350 400


Lea

kag

e F

low

(lb

m/h

r)

y

Case Study Conditions

Continuous Blowdown Line to Condenser 4 Inch pipe diameter, 1000 psi, saturated liquid (~ 10%

steam) Temperature decreases along pipe as location moves

away from valve Design Flow is 300,000 lbm/hr; Low Value is 209,000

lbm/hr Goals

Verify that calculation of flow is within the high and low value.

Verify that correction for measurement location is valid.

359°F

351°F

351°F

349°F

342°F

342°F

Flow Resistance Bernoulli:

Solving for V2 (“a” accounts for the other terms in the Bernoulli equation).

The separated term accounts for the flow resistance. Because it is proportional to velocity and flow it can be applied as a correction factor to the velocity and flow results of the basic flow equations which do not account for flow resistance.

5.0

2 21

KaV

g

VKz

g

V

g

Pz

g

V

g

P

222

22

2

222

1

211

5.0

21

K

Distance to Condenser By applying a correction to the calculated flow, a more

accurate estimate for the flow can be calculated “Distance to Condenser” applies this correction in the

TP-Plus software. This value is the equivalent hydraulic distance, based on

actual linear distance and the number of elbows, tees, valves, and other flow disturbances in the leakage path.’

Protects against over-promising the savings to be realized by repairing the leaking valve(s)

Valve Information Sheet

Continuous Blow Down Without Correcting FlowContinuous Blow Down Without Correcting Flow

180000

200000

220000

240000

260000

280000

300000

330

335

340

345

350

355

360

365

17.0 144.3 202.0 229.4 252.1 285.9

lbm

/hr

°F

Distance from Condenser

Comparison of Temperature and Flows

Pipe Temperature Calculated Flow Actual Flow (Design)

Continuous Blow Down With Corrected FlowContinuous Blow Down With Corrected Flow

Conclusion Cycle Isolation Monitoring can provide significant savings

The process can be utilized with an on-line monitoring system

Proper modeling can have a significant effect on reliability of results

Questions

Quantifying Cycle Isolation Losses and Integration with On Line Systems Feedwater System Reliability Users Group 2015 Meeting San Antonio Ken Porter Rich.

Documents

low flow slide

p slide

mw lost slide

online software slide

downstream of valve

leaking valves source

small change slide

header valve