Application of the metal magnetic memory method for diagnosis · PDF file · 2016-08-23impending failures of power engineering parts ... are the magnetic parameters of testing ...

Application of the metal magnetic

memory method for diagnosis of

impending failures of power

engineering parts

Anatoly Dubov, Sergey Kolokolnikov

Energodiagnostika Co. Ltd., ( Moscow, Russia)

E-mail: [email protected]

METHOD OF METAL MAGNETIC MEMORY


Introduction.

6. Conclusions.

1. General techniques for testing by using

the metal magnetic memory method

2. Inspection of pipelines and pressure vessels

base metal.

4. Inspection of pipelines and pressure vessels

welded joints.

Content:

5. Inspection of steam turbine parts.

3. Inspection of heat surface tubes.

The SCZ’s are the zones with high stress-strained state

inhomogeneity.

The SCZ’s are the main sources of equipment damages.

Corrosion, fatigue, creeping are developed in the SCZ’s

most intensively.

Detection of the SCZ’s is very important for early

diagnostics of fatigue damage and evaluation of

equipment and structure lifetime.

The damages take place

in the stress concentration zones

(SCZ’s) !!!

Microcrack appearance

(or microcracks appearance

and accumulation)

Introduction

Crack appearance

SCZ appearance

Initial material stage

Microdamages of microstructure (dislocations)

displacement and accumulation

Microplastic areas (stable slip bands)

Degradation of

mechanical properties

I

II

H, A/m

10000

L, mm

1000

100

Microstructure Microcrack Crack

variation

Test

object

Level of artificial

magnetization

MPI,

MFL,

MGI,

HE,

FSI, Barkhausen

effect

MMM

Level of self-

magnetization

M. field of the earth

ISO 24497-1:2007(E) Non-Destructive testing –

Metal magnetic memory –

Part 1: Vocabulary.



Part 2: General Requirements.



Part 3: Inspection of welded joints.

THE METHOD OF METAL MAGNETIC MEMORY

ISO 24497- 1:2007(E) Vocabulary

2.1.

metal magnetic memory

MMM

after-effect which occurs as residual magnetization in

components and welded joints formed in the course of

their fabrication and cooled down to ambient

temperatures under interaction with weak magnetic fields

or

due to irreversible change of the local magnetization

state of components in zones of stress concentration and

damage under working


2.3.

method of metal magnetic memory

MMM method

non-destructive testing method based on the analysis

of self-magnetic leakage fields (SMLF) distribution

on component’s surfaces for determination of stress

concentration zones (SCZs), imperfections, and

heterogeneity in the microstructure of the material and in

welded joints


ISO 24497- 1:2007(E) Vocabulary


Physical fundamentals of the MMM method:

The inverse magnetostrictive effect (Villary effect) is

a change of the magnetic susceptibility of a material

when subjected to a mechanical stress.

The magnetoplasticity is an effect of self

magnetization increase in the local zones of anomaly

plastic strain.

The magnetic flux leakage effect, based on magnetic

field scattering by structural and mechanical

heterogeneities at metal natural magnetization.

The scheme of SMLF induction flow

parameters measurement.

Flux-gate

probe

The scheme of measurement of the resulting magnetic

field with artificial magnetization.

The MMM method uses natural magnetization and after-effect displayed

as the magnetic memory of metal to actual strains and structural

changes in products and equipment metal.

www.energodiagnostika.ru

Magnetizing

Coil

The MMM method is the only passive method among the

magnetic NDT methods.

),(p zxfН Y

),(p zxfН Z

),(p zxfН X x

HK

Y

pY

инX

z

HK

Y

pY

инZ

x

HK

X

pX

инX

z

HK

X

pX

инZ

x

HK

Z

pZ

инX

z

HK

Z

pZ

инZ

НL=f()

Scheme of relationship

between the SMLF intensity

(Hp) and the strain tensor

variation

The components of the SMLF intensity

are the magnetic parameters of testing

by using the MMM method

Magnetic criteria –

gradients of the SMLF

components intensity

Designation of coordinate axes

accepted in the MMM method

L

L

L

in

in

in

in

in

in

L

L

L


Magnetic parameters used at MMM method:

Normal and tangential components of the self-

magnetic leakage fields (SMLF) intensity – HL (A/m).

The SMLF gradient dHL/dx or dHL/dz (A/m2).

HL SCZ

dHL/dx Rejection level of dHL/dx

1. General techniques for testing by using the metal

magnetic memory method

MMM method advantages:

Small-sized instruments are used for the MMMМ testing.

Any special test surface preparation is not required.

Special magnetization is not required.

The MMM method allows carrying out quick testing of

components made of carbon, low-alloy and austenitic

steel grades.

The MMM method allows carrying out quick quality

testing in both the manual and automatic modes.

Multi-channel scanning devices for inspection by

using the metal magnetic memory method:


HL HL

Y X

The flux-gate transducers for

registration of the tangential HL and

the normal HL components of SMLF

are combined in one casing.

Y

X

2. Inspection of pipelines and pressure vessels base metal.

THE METHOD OF METAL

MAGNETIC MEMORY

Zone of SC

1-6 – numbers of measurement

channels Distribution of the field HL and the field gradient dHL/dx

along motion path of the flux-gate transducer No.4.

Results of steam pipeline bend (426×18 )

testing by using the MMM method.

Crack was detected in the SCZ.

SCZ

Crack location

3 h 6 h 9 h

Crack location

SCZ

Scheme of steam

pipeline bend testing.

Multichannel SD for pipeline testing

Results of examination of the stretched zone of a steam

crossover pipe bend. (1)–(3) Measurement channels.

Structure of the outer surface metal of

the steam crossover pipe’s bend (500).

40 micrometers

8 micrometers

Результаты контроля методом

500

IIW-1946, Welding in the World, 2010, vol. 54, no. 9/10, pp. R241-R248


b) Stress concentration zones SCZ-1

and SCZ-2 locations on the steam

pipeline bend.

a) Distribution of the field HL and the

field gradient dHL/dx along steam

pipeline bend;

The results of testing of steam pipeline bend (426x18mm, steel 15CrMo1V,

pressure P=140 atm, T=540°C), Unit No.3 of “Konakovskaya” TPS.

Metal structure of the steam

pipeline bend in the SCZ-1 and

SCZ-2.

Results of testing of steam pipeline bend No.112-113

( 245 х 45, steel 15Cr1Mo1V, P=230 atm, t=530C),

Unit No. 4, Konakovskaya TPS (Total working hours - 245 000).

Results of steam pipeline bend testing by

using the MMM method

SCZ-1

Special multichannel scanning

devices location on steam

pipeline bend.

SCZ-2 SCZ-3

Location of the SCZ’s

on the bend surface.

SCZ-2

SCZ-1 SCZ-3

Metal structure in place

of microcrack location

Results of metallographic analysis in the SCZ-2.

500

Results of steam pipeline bend testing

by using the MMM method

SCZ-1 SCZ-2 SCZ-3

100

Microcrack in the SCZ-2

100

Estimation of mechanical properties of metal of the bend No.112-113

in the SCZ’s and outside SCZ’s

SCZ-2

SCZ-1 SCZ-3

The hardness tests were presented in the SCZ-1 and SCZ-3 by using special

technique of indentation hardness measurement and portable static hardness

testing machine.

Yield strength Ultimate strength

(MPa) (MPa)

In the SCZ’s 24 kg/mm2 51 kg/mm2

Outside the SCZ’s 35 kg/mm2 58 kg/mm2

3. Testing of heat surface tubes using

the MMM method

Test performance of heat surface tubes using the

MMM method and TSC-type instrument

b) Super heater coils testing

using SD Type-2M

a) Water wall tubes testing

using SD Type 1-8M

Results of front water wall tube No.37 testing at

level 12-14m at TPS “Nassiriya” (Iraq)

b) Location of developed pitting corrosion

on inner surface after tube cut in the SCZ.

a) Distribution of the field HL and the field gradient

dHL/dx along the outer side of the water wall tube No.37

1

2

Results of testing of the super heater coil No.20 (Ø32х4,5мм,

steel 316 (ASTM)) of stage No.4 of boiler BKZ-420 at the unit

No. 6 of TPS “Dyagilevskaya” (Russia)

Magnification 500

b) Results of metallographic analysis performed in the SCZ

detected by the MMM method. Intergranular corrosion was

detected in the SCZ.

a) Distribution of the field HL and the field gradient dHL/dx along

the outer side of the super heater coil No.20

1 2

4. Testing of pipeline welded joint using

the MMM method

Scheme of welded joint testing by using

special scanning device.

Z


The MMM method allows detecting SC zones and

locations of defects by the pattern of SMLF and its

gradient distribution.

www.energodiagnostika.ru

SCZ

Hp field gradient dH/dz

distribution between channels H2 and H3;

SCZ

Crack location

Crack location


HL,

10

3 A

/m2

HL, A

/m

Laminations

Crack location

SCZ-1 SCZ-2

a)

c)

Results of heat exchanger weld segment inspection

b) SCZ-1

Crack in the

SCZ-2

5. Steam turbine blades inspection

by using the MMM method.


Results of testing presents the inspection results of the blade

No.19 of the stage No.15 of rotors of the turbine S50-90/1,2-I,

Unit No.4 on Beijing TPS-2 (China)

b) Location of the crack on the blade

a) Distribution of the field HL and the field gradient dHL/dx

along the steam outlet edge of the blade

2

Results of steam turbine blade testing No.12 of stage No.38 of LPR.

Steam turbine K-300-240 (LMZ) Unit No.5 of TPS “Konakovskaya”.

Results of metallographic analysis in the SCZ SCZ location on the blade

Area of

replica taken

150 600

SCZ

Distribution of SMLF – HL and its gradient dH/dx along

the blade No.38


Results of the Hp field and its gradient measurements in SCZs on the stage

No.38 blade No.12 of unit No.5 before metal grinding (a), after grinding for

taking a “replica” (c) and after re-grinding (d),

b – results of metallographic analysis with magnification 600.

а)

c)

а)

в)

г)

b)

d)

600


Steam turbine disks testing

by using the MMM method.

Microcracks

Results of K-300-240 turboset MPR stage #29 disk crown

inspection on the steam outlet side of unit No.3 at

“Konakovskaya” TPS:

a – the diagram of the Hp value distribution in SCZs;

b – results of metallographic analisys.

500

SC zone

а)

b)

6. CONCLUSIONS

1. Distribution of the SMLF characteristics, reflecting the

individual features of material, allow to solve more

efficiently the problems of damage prevention, lifetime

estimation, repairs based on the actual state of base

metal, welded joints and steam turbine units of power

engineering.

2. The use of the MMM method during the 100%

inspection of the ageing equipment will allow to detect

crack formation areas in future and to estimate the

speed of their development for various units of power

engineering equipment.

6. CONCLUSIONS

3. During the periodic inspection of individual turbine units

the metal magnetic memory effect provides the possibility

to record all changes in the metal structure, which take

place in the course operation.

4. Comprehensive testing of industrial equipment by

using MMM method and conventional NDT methods allow

to get more precise data about actual material state of

critical part and units of industrial equipment.

5. The grinding the outer surface of the industrial

equipment in SCZs area allows to prevent damage at the

initial stage of its development.

Application of the metal magnetic memory method for diagnosis · PDF file · 2016-08-23impending failures of power engineering parts ... are the magnetic parameters of testing ...

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