Furnace

PREDICATION OF

RESIDUAL LIFE TIME OF RESIDUAL LIFE TIME OF

STEAM REFORMER TUBES

Prof Bahaa ZaghloulProf. Bahaa ZaghloulEx‐President of Central Metallurgical Research and Development Institute ‐ CAIRO, EGYPT [email protected]

DIFFERENT APPLICATIONS OF DIFFERENT APPLICATIONS OF REFORMER TUBES …REFORMER TUBES …

CMRDI

Limit of tube Metal Applications

40pp

Hg/cm

2 G)

30H2

essu

re (K

g

20NH3

CH3OH

Pre

10Town Gas

D. R.

10

700 800 900 1000

Gas Temperature (OC)

LIMITATION OF OPERATION LIMITATION OF OPERATION TEMPERATURE …TEMPERATURE …

CMRDI

Inlet

Control to Prevent Carbon Formation

Tube

al

yst T

Control the Max. Tube Skin Temperature C

ata

Critical PortionOutlet

DIFFERENT DESIGNS FOR REFORMER DIFFERENT DESIGNS FOR REFORMER FURNACE …FURNACE …

CMRDI

1 3

Radiant UPRadiant Wall Type

UP

Firing Type

Terrace DownTerrace Wall Type Firing Type

2 4

EFFECT OF FIRING SYSTEM ON TEMP. EFFECT OF FIRING SYSTEM ON TEMP. PROFILE …PROFILE …

CMRDI

I UP II D III DOWN & UPI . UP II . Down III . DOWN & UP

PreferablePreferablePreferable Preferable ProfileProfile

V . RADIANT WALL

IV . TERRACE WALL

IDEAL TEMPERATURE PROFILE …IDEAL TEMPERATURE PROFILE … CMRDI

InletInlet

OutletGas Temperature

Heat Flux Tube Skin Temperature

Solid Line : Ideal Profile Dotted line : Preferable Profile

REFORMER TUBES MATERIALS REFORMER TUBES MATERIALS EVALUTION CHARTS …EVALUTION CHARTS …

CMRDI

HK40

HK40‐high Si25Cr‐20Ni-high Si

IN519 IN519‐mod.

Si

Nb Ti

25Cr‐20Ni

HI‐Ka1a25Cr‐20Ni-Ti‐MS

24Cr‐24Ni‐Nb 24Cr‐25Ni-Nb‐TiTi

BST‐Alloy25Cr‐20Ni‐Ti‐Nb

HI‐Ka1b25Cr‐20Ni-Nb‐Ti‐MS

Nb

MS: MishmetalHT

HT‐mod.20Cr‐32Ni‐C

15Cr‐35Ni

HU19Cr‐39Ni

Alloy 80020Cr‐32Ni

Manaurite 900 T52 PG20‐32

Nb Nb

T52,PG20‐32 CR32W,KHR32C

20Cr‐32Ni‐Nb‐Low C

Manaurite 36X Su‐Paralloy H39W

Manaurite 900B Paralloy CW39WLow C

Nb

WHP

25Cr‐35Ni‐Nb 25Cr‐35Ni‐Nb‐Low C

Manaurite 36XM HP‐BST

25Cr‐35Ni‐Nb‐Ti

Ti

WW

Mo

26Cr‐35NiMo‐Re 1

25Cr‐35Ni-WManaurite 36XS25Cr‐35Ni-Nb‐W

Su‐Paralloy H34CTManaurite 900

Nb

Co

25Cr‐35Ni-5W‐2Co

Supertherm28Cr‐35Ni-5W‐15Co

Manaurite 900 T52,PG20‐32

20Cr‐32Ni‐Nb‐Low C Co

REFORMER TUBES MATERIALS REFORMER TUBES MATERIALS EVALUTION TABLES …EVALUTION TABLES …

CMRDI

METALLURGY DEVELOPMENT

RELATIVE Nb Ni Cr COMMON

DEVELOPMENT

RELATIVE STRENGTH

OTHERSNb %

Ni %

Cr %

COMMON NAME

DATE

HK6 1.0‐‐‐‐‐‐2025HK401960s

1.4‐‐‐12425IN5191970s 4455 997

1.7Ti12223BSTEarly 80s

1.9Ti13525HP – BSTMid 80s

2.2Ti, Zr, W, Cs13525HP Micro‐alloyLate 80s

CREEP RAPTURE STRENGTH OF CREEP RAPTURE STRENGTH OF COMMERCIAL MATERIALS …COMMERCIAL MATERIALS …

CMRDI

20

108

6

gf/m

m2)

4

ress

(K

g

BST - M

25 35Ni Nb

2

Str 25 – 35Ni - Nb

IN 519HPHK 40

100 1000 10000 100000

Time to Rupture (h)


CMRDI


CMRDI

Rapture Stress for Generic Tube Materials …

35

25

30

/mm

2 )

20

tres

s (N/

10

15

Rapt

ure St

5

10R

0HK40 IN519 HP ‐

BSTHP Micro‐

alloyBST

FAILURE MODE OF REFORMER TUBE …FAILURE MODE OF REFORMER TUBE … CMRDI

CMRDICROSS SECTION OF FAILED REFORMER CROSS SECTION OF FAILED REFORMER TUBE …TUBE …

PROGRESS OF CREEP FAILURE …PROGRESS OF CREEP FAILURE … CMRDI

START GROWTH FAILURE

Cracks 30% from inner wall

Cracks grow to break inner wall

Cracks progress to outer wall

EFFECT OF MACROSTRUCTURE ON EFFECT OF MACROSTRUCTURE ON CRACK PROPAGATION …CRACK PROPAGATION …

CMRDI

TYPICAL CREEP DAMAGE MECHANISM TYPICAL CREEP DAMAGE MECHANISM IN REFORMER TUBES …IN REFORMER TUBES …

CMRDI

D

FRACTURE

D

rain

C

Breep

Str

A

I II III

C

I, II, III :

Creep Ranges

Exposure Time

Microstructure Evaluation of Cast Steel Tubes During Operation Time in Reformer Furnace … CMRDI

Change In Tube Microstructure During Operation in Reformer

Furnace

PRIMARY AND

Change in primary inner dendriticChemical composition

PRIMARY AND SECONDARY PHASES

MATRIX

Change in primary inner dendritic austenite‐carbides eutectic

Secondary carbides precipitation and

Chemical composition modifications & accompanied heterogenty in solid solution

Secondary carbides precipitation and interactions with primary carbides

Continuous carbides network formation around austenite grains

Changes in dislocation structure and dislocation density growth

Ch i t it i formation around austenite grains

Coalescence of sigma phase inside and around austenite grains

Changes in austenite grain boundary microstructure due to the carbides coalescence and voids formation g

CMRDI

Eff t Of Mi t t lEffects Of Microstructural

Changes In Reformer Tube

Decrees In Creep ResistanceResistance

Microvoids Initiation On Deterioration On

Mechanical Properties Interphase Boundaries

id iVoids Propagation

Voids Coalescence Into Fissures

COMMON DAMAGE MECHANISM IN COMMON DAMAGE MECHANISM IN REFORMER TUBES …REFORMER TUBES …

CMRDI

1. Overheating (Cumulative)

2. Thermal Cycling ( cyclic operation )

T b B di ( i i h b l 3. Tube Bending ( improper counter weight balance

for tube linear will increase stress on tube)for tube linear will increase stress on tube)

4. Thermal shock

5. Stress Corrosion Cracking

OVERHEATING CMRDIOVERHEATING

Temperature Increase To Maintain Yield When Catalyst Becomes Less Active.

1

Feedstock Or Steam Supply Failure 2

The Absence Of Cooling Effect Of The Endothermic Reaction3

Burner Misalignment Can Result In Over Temperature4 Burner Misalignment Can Result In Over Temperature4

Restricted Flow Of Process Due Catalyst Choking5

EFFECT OF OPERATION TEMPERATURE EFFECT OF OPERATION TEMPERATURE AND PRESSURE ON TUBE LIFE …AND PRESSURE ON TUBE LIFE …

CMRDI


CMRDI





4. Thermal shock


THERMAL CYCLES CMRDITHERMAL CYCLES

Through Wall Stresses are Temporarily Increased1

Tube Wall Temperature Gradients Can Be Significant2 Tube Wall Temperature Gradients Can Be Significant2

During Operation , The Stress Produced By Different Expansion Relaxes Through Creep 3

Temperature Changes Up Or Down Will Reintroduce Some4 Temperature Changes Up Or Down Will Reintroduce Some Stress.4

COMPARISON OF STRESS DISTRIBUTION IN CYCLIC OPERATION …

CMRDI

HK40

IN519


CMRDI





4. Thermal shock


THERMAL SHOCK CMRDITHERMAL SHOCK

Creates Extremely High Stresses As The Tube Attempts To C t t U d R t i t1 Contract Under Restraint .1

It Results In Circumferential Tearing Or Shattering Of The Tube.2

Can Occur Through Boiler Water Carry Over On Inside The Tubes3

EFFECT OF OPERATION TEMPERATURE ON EFFECT OF OPERATION TEMPERATURE ON MICROSTRUCTURE OF INMICROSTRUCTURE OF IN519 519 MATERIAL …MATERIAL … CMRDI

MICROSTRUCTURE OF IN519 CAST STEEL TUBE …

N d d d l ft 24000 hNon degraded sample after 24000 h

after 30000 h

Operation in Reformer furnace 86000 h

FAILURE ANALYSIS OF PRIMARY REFORMER TUBE … CMRDI

OPERATION PERIOD = 6 Years

Top Flange

Rapture Zone

Rupture Zonep

Top Flange

CMRDIGENERAL AND ENLARGED VIEWS OF OUTER

AND INNER SURFACES OF RUPTURE ZONE OF

REFORMER TUBE.

NOTE: NON‐UNIFORM WIDTH OF BRANCHED CRACK.

CMRDISUMMARY OF MICROSTRUCTURE CHANGE THROUGH THICKNESS, ALONG REFORMER

GTUBE LENGTH …

S1:30 cm from top flange


1000X

S4:

1000X

S8:Rupture zone320 cm from top flange

1070 cm from top flange

200X 1000x



500X 1000x

FAILURE OFPRIMARY REFORMER TUBE … CMRDI

OPERATION PERIOD S4PERIOD

18 YearsRUPTURE

S1

S2

S3

RUPTURE

S5

A

S1

CB

1000X1000 X1000

X

1000X

1000X

1000X1000X

1000X

Header

200 x 1000XHeader

50x

PRIMARY REFORMER TUBE … CMRDI

Tube: 135.6mm , 12.8mmMaterial: HP‐Nb – 0.4C, 35Ni, 25Cr, 1.24Nb

Pressure : 35.7 bar

OPERATION PERIOD = 9 Years

Pressure : 35.7 bar

Skin Temp.: 917oC Max 860oC Min

100XTest Coupon 5

e e

Su

rface

Su

rface

Inn

er

S

Ou

ter

S

Test Coupon 3

TEST COUPON 5

TUBE WALL CENTER100X 400XTUBE WALL CENTER100X 400X

TEST COUPON 3

RESULTS OF CREEP RUPTURE TEST OF USED PRIMARY REFORMER TUBE …

CMRDI

Creep Rupture Strength Master Curve for Used

& Unused Primary Reformer Tube Materials …CMRDI

y o

LMP = T ( C + tr ) 10‐3

T: Test T (OK),tr : Rup. time (hr)C: Constant

Thi f f d t l t i dThis form of data plot is usedto extrapolate short‐term testdata to rupture stresses up to100 000 hr100,000 hr

Working S is a function of mainly circum., long., and thermal S.

The most critical one is the circum. S & it was assumed to be 1.8kg/mm2

based on the following equation. (ASME ‐ Section VIII ‐ Division 1)

S = ( P R + 0.6 P t ) / E t( ) /

S: Maximum allowable stress value.P I t l d i P ll bl ki PP: Internal design P or max. allowable working PR: Inside radius E: Joint efficiency t: Min. thick

ki d b OSkin T was assumed to be 917 OC,

Remaining life‐time is calculated from data of Larson‐Millar parameter

of used reformer tubeof used reformer tube.

The remaining life was estimated based on S & skin T. to be ~20,000 hr

at 1 8 kg/mm2 working Sat 1.8 kg/mm2 working S.

The life‐time will be increased at lower skin T

ESTIMATED RUPTURE TIME OF USED PRIMARY REFORMER TUBE UNDER CMRDI

DIFFERENT TEMPERATURES & STRESSES

1.8kg/mm2

2.5kg/mm2

917oC

NON DESTRUCTIVE TESTING METHODS NON DESTRUCTIVE TESTING METHODS

FOR DAMAGE EVALUATIONFOR DAMAGE EVALUATIONCMRDI

FOR DAMAGE EVALUATION…FOR DAMAGE EVALUATION…

Dimensional changes; diameter and wall thickness due to creep

R li t l h t h k f i t t l hReplica metalography; spot check for micro structural changes

due to overheating and some times creep damage

Radiography; large voids and micro cracks

Eddy current; chromium migration due overheating andEddy current; chromium migration due overheating and

conductivity changes

Ultrasonic; attenuation and scattering

New techniques such as LOTIS and IESCO ‘H’ SCANNew techniques such as LOTIS and IESCO H SCAN

CREEP DAMAGE EVALUATION METHOD …CREEP DAMAGE EVALUATION METHOD … CMRDI

New Project forNew Project for

P O RPREDICTION OF REMAINING

LIFE OF REFORMER TUBES

&

PARTICIPATING CMRDI Fraunhofer IWM COMPANIES

CMRDI Egypt

Fraunhofer IWM Germany

LIFE TIME PREDICATION FOR STEAM LIFE TIME PREDICATION FOR STEAM REFORMER TUEBS…REFORMER TUEBS… CMRDI

Possible Industrial Partners:

Egyptian Fertilizers Co., Ain El-Sukhna, EFC

ALEXFERT Alexandria Fertilizers Co., Alexandria

D lt F tili C T lkhDelta Fertilizer Co.,Talkha

Apu‐Quir Fertilizer Co.; Alex

Schmidt + Clemens,Centrifugal Casting Div., Kaiserau

UHDE Engineering Egypt, Cairo

LIFE ASSESSMENT REQUIREMENTS…LIFE ASSESSMENT REQUIREMENTS… CMRDI

Requirements Requirements For Analysis

To undertake a furnace life assessment the following input information is required …

Furnace design drawings / material records / Operation history (turn-around and process conditions)

Process temperature and pressure records as available

Tube samples for material specific assessment

A i t NDT t h i d tAppropriate NDT techniques data

LIFE TIME PREDICTION OF

Collection / Selection Of Tube Materials, Geometries, Plant, Connections And Process Conditions

PREDICTION OF REFORMER TUBES

Development Of Test Set Up And Measurement Techniques For Specimens And Model Tubes.

Continued Testing Of Specimens From Used Tubes And Failure Cases

Testing Of Virgin Material Specimens In Tension, Creep And Thermal Fatigue Acc. To Service

NDE Of Used TubesProfilometry

Vi l

Repeated Examination Of Damage ‐ NDE E.G. Eddy Current, UT ‐ Hardness

Visual UT, EC, …

X‐ray

‐Metallography, Microstructure. ‐ Sem & Edx

Material Description for

Evaluation Of Mechanisms And Degree Of Damage In

Used Tubes

Material Description for‐ deformation ‐ damage‐ failure incl. overlapping effects

Model Component Test And Simulation (Short Section Of Tube

Implementation In FE Code

Simulation (Short Section Of Tube Exaggerated Loading, Shorter Times)

Verification – Comparison Of Calculation (Material Degradation Component Behavior)

With Measurement Results

Material / microstructure based life time prediction applied to a specific plant


STEP 1 : COLLECT & SELECT INPUT DATA

- Tube material (properties, behaviour), -dimensions

- Plant design: inlet/outlet pigtails,firing system,welds,…

- Operational conditions: feedstock ratepressurefluid temperaturepskin temperaturethrough wall temperaturestart up/shut down cyclesstart up/shut down cyclesprocess upsets…

- service experience


STEP STEP 22 : DEVELOP TEST SET UP AND MEASUREMENT

TECHNIQUES FOR ROUND BAR SPECIMEN

TESTS ON REFORMER TUBE MATERIALS

Cyclic strain- and temperatures tests


STEP 3 : DEVELOP TEST SET UP AND MEASUREMENT

TECHNIQUES FOR MODEL REFORMER TUBE TESTS

Optical Strain Measurement

HAZ T915‐10mm

HAZ T915‐10mm

NiCr20Nb Austenite55

5 mm10 mm


STEP 4 : TESTING OF VIRGIN AND USED REFORMER TUBE MATERIAL SPECIMENS

‐ LCF‐tests at RT up to service temp. (950°C)

REFORMER TUBE MATERIAL SPECIMENS

Grobkorn-WEZ 625°CGrobkorn-WEZ 550°C

300 p p ( )‐ cyclic hardening/ softening‐ hystereses‐life time

100 interkritischeWEZ 625°C

Grobkorn-WEZ 650°C

Fg in

MPa

‐ TMF with realistic T‐e –cycles‐ in/out of phase‐ hold times‐ heating and cooling times

WEZ 625 Cinterkritische WEZ 650°C

50 WEZ3 GK WEZ2 FK WEZ1 IKGW FZJ

T in °C 550 625

Span

nun

‐ Creep tests10 100 1000 10000

GW MFI 650

Zeit in h


STEP 5 : MEASUREMENT OF DEFORMATION, DAMAGE & FAILURE; EVALUATION OF MECHANISMS IN THE TUBE MATERIALSEVALUATION OF MECHANISMS IN THE TUBE MATERIALS

‐ NDE: dimensional measurements, UT, EC, …

‐ Hardness

‐Metallography, microstructure, replica techniques

‐ SEM & EDX

Cyclic Plastic Deformation

Creep DamageMicro/Macro Cracking Corrosion


STEP 6 : MATERIAL DESCRIPTION FOR DEFORMATION, DAMAGEAND FAILURE INCL OVERLAPPING EFFECTSAND FAILURE INCL. OVERLAPPING EFFECTS

‐Material models for cyclic plastic deformation (Chaboche, Jiang)

- IWM Software FITIT®

950°C

)(4,245122

TFD plIeffI ⎞⎜⎛

∆∆∆ σσ

‐ Damage parameter

),(31

,45,1 , tTFNE

D ple

ecy

I

cy

effITMF ⎟

⎠⎜⎜⎝

∆∆+

+= εσσσ


STEP 7 : IMPLEMENTATION OF NEW MATERIAL STRUCTURAL (FE) MODELSSTRUCTURAL (FE) MODELS(EVALUATION OF SPECIMEN TEST RESULTS)

Application Of Damage Parameter DTMF

To LCF‐ and Tmf‐tests


STEP 8 : VALIDATION BY

‐ Post evaluation of well documented failure cases from fertilizer plants(parameter studies!)

‐Model component tests and FE simulation (short tube section, exaggerated loading, shorter times,…)

Tube Tests

500

600600

Internal pressure: 480 bar T

300

400

500

300

400

500

pera

tur [

°C]

pres

sure

in b

ar,

load

in k

Nes

sure

, bar

oad,

kN

Temperatur

100

200

100

200 Tem

p

Inte

rnal

pax

ial

Axial load41.8 kNIn

tern

. Pre

Axi

al lo

re [°C]

FE - Simulation OfStresses & Strains

01 2 3Cycles

0

Cycles


STEP 9 : APPLICATIONS

Material tests/ microstructural analysis and FEM simulation ‐ based

V lid t d P d t t b h i d t i tValidated Procedure to assess component behavior under transient

severe service conditions

Ready To Be Used For

‐ Life Time Management of catalyst steam reformer tubes

‐ Process Optimisation

‐ Inspection Strategy development

‐ Reconsidering plant Design and Operating Conditions

YOUR KIND PARTICIPATION IN THE PROJECT

WILL BE HIGHLY APPRECIATED

M Th k F EFC Wh I i d M F Thi P i Many Thank For EFC Who Invited Me For This Presentation

&THANKS FOR YOUR ATTENTION

&THANKS FOR YOUR ATTENTION

Furnace

Documents

common damage mechanism

creep rapture strength

develop test set

steam reformer tuebs

life time predication

di tube bending

stress corrosion cracking

primary reformer tube