OptimisingOptimisingOptimisingOptimising Power Generation Maintenance using Power Generation Maintenance using Power Generation Maintenance using Power Generation Maintenance using Thermal and CFD modellingThermal and CFD modellingThermal and CFD modellingThermal and CFD modelling

• Warwick Ham

• Boiler Process Engineering Group Leader

• Steinmüller Africa, Bilfinger Power Systems

• South Africa

Summary

• Introduction• Failure statistics• How to improve availability• Using CFD to understand the real causes• Record keeping• Don’t just fix it – Change it!

Introduction

Superheater/Reheater

Feedwater

System

Condenser Cooling Tower

Generator

Stack

Heat- Recovery

System

FGD - Fan

Steam Turbine

Air Preheater

ID - Fan

DeNOx - SCR

Precipitator

De-Ashing

Economizer

Steam Generator

Ash Silo

De-Ashing

Mill

Firing Systems

Coal/Oil/Gas

FD - Fan

FGD

Coal Feeder

HP - Pipes

Introduction

• The Coal Fired Power Generation Cycle

Failure Statistics• The most common types of Failures

– Fatigue– Corrosion Fatigue– Fly Ash Erosion– Falling Object

Damage

0

2

4

6

8

10

12

14

16

18

Num

ber

of B

TF

s

X Power Station - BTF Mechanism

2006

2007

2008

2009

2010

2011

2012

Failure Statistics

• Fly Ash Erosion Failure Locations– Economiser– Reheater– Helical Wall– Division Wall

0

2

4

6

8

10

12

14

16

18

EconomiserDivision wallScrew wallVertical wallSuper heater 1Superheater 2Superheater 3Reheater 1Reheate r 2

Num

ber

of B

TF

s

X Power Station - BTFs per Component

2006200720082009201020112012

Failure Statistics• The most common Fly Ash

Erosion Causes– Operation outside of design

envelope• Excessive startups/shutdown• High ramp rates• Excessively high load

– Operation outside fuel envelope• High Ash• High Moisture• Low CV

– Erosion• High flue gas velocity

Improve Availability – How?• Design

– Realistic specifications

• Operation– Procedures

• Maintenance– Adjust maintenance philosophy to actual

operating conditions

• Understand the mechanisms– System thinking– Detailed CFD investigations

Using CFD – Understanding

• Mill Wear

• Boiler erosion– Pressure Parts – Non Pressure Parts

• Manufacturing Quality

Using CFD – Understanding

• Mill Wear (Video)– Excellent agreement between CFD prediction and actual wear

patterns

Using CFD – Understanding

• Mill Wear– Excellent agreement between CFD prediction and actual wear

patterns

Using CFD – Understanding

• Mill Wear– Improved design

Using CFD – Understanding

• Boiler erosion– Pressure Parts

Using CFD – Understanding• Boiler Pressure Part Erosion

• Localisation• Erosion Rate

Using CFD – Understanding

• Boiler Non Pressure Part ErosionLocalisedRate

Using CFD – Understanding

• Boiler Non Pressure Part Erosion

Using CFD – Understanding• Maintenance Manufacturing Quality

– Spherical header

Using CFD – Understanding

• Manufacturing Quality– Heat treatment

• Spherical header• Heat treatment

procedure

Record keeping – the key• Design records

– Basis• Fuel Range• Operating mode• Lifetime

– Original design assumptions

– Modifications• Maintenance

experience

Record keeping – the key

• Operating records– Procedures

• Maintenance records• Failure RCA

0

2

4

6

8

10

12

14

16

18

Poor workmanship Poor operating Design defect Modifica tion defect Ageing Unknown

Num

ber

of B

TF

s

X Power Station - BTFs Root Cause

2006

2007

2008

2009

2010

2011

2012

Don’t just fix it – Change it!

• Assess original design intent against actual conditions

• Challenge assumptions• Assess operating procedures• Assess maintenance trends• Understand the causes• Develop new design basis

Summary

• Introduction• Failure statistics• How to improve availability• Using CFD to understand the real causes• Record keeping• Don’t just fix it – Change it!