ISO 17638 MT in NDT

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INTERNATIONAL STANDARD

ISO 17638 Second edition 2016-10-15

Non-destructive testing of welds — Magnetic particle testing Contrôle non destructif des assemblages soudés — Magnétoscopie

Reference number ISO 17638:2016(E) © ISO 2016

ISO 17638:2016(E)

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© ISO 2016 – All rights reserved

ISO 17638:2016(E)

Contents

Page

Foreword ........................................................................................................................................................................................................................................ iv 1 Scope ................................................................................................................................................................................................................................. 1 2 Normative references ...................................................................................................................................................................................... 1 3 Terms and definitions ..................................................................................................................................................................................... 1 4 Safety precautions .............................................................................................................................................................................................. 1 5 General ............................................................................................................................................................................................................................ 1 5.1 Information required prior to testing ................................................................................................................................. 1 5.2 Additional pre-test information ............................................................................................................................................... 2 .................................................................................................................................................................... 2 5.4 Surface conditions and preparation ..................................................................................................................................... 2 5.5 Magnetizing ............................................................................................................................................................................................... 2 5.5.1 Magnetizing equipment ............................................................................................................................................. 2 f ................................................................................................................................ 3 5.6 Application techniques .................................................................................................................................................................... 3 5.6.1 Field directions and testing area........................................................................................................................ 3 .............................................................................................................. 6 5.7 Detection media ..................................................................................................................................................................................... 9 5.7.1 General...................................................................................................................................................................................... 9 f f ......................................................................................... 9 5.8 Viewing conditions ........................................................................................................................................................................... 10 5.9 Application of detection media .............................................................................................................................................. 10 5.10 Overall performance test............................................................................................................................................................. 10 5.11 False indications ................................................................................................................................................................................. 10 5.12 Recording of indications .............................................................................................................................................................. 10 5.13 Demagnetization ................................................................................................................................................................................ 11 5.14 Test report................................................................................................................................................................................................ 11 Annex A (informative) Variables affecting the sensitivity of magnetic particle testing ............................... 13 Bibliography ............................................................................................................................................................................................................................. 15 5 .3

Pers o nnel qualificatio n

5 .5 .2

Verificatio n o

5 .6.2

Typ ical magnetic tes ting techniques

5 .7.2

Verificatio n o

© ISO 2016 – All rights reserved

magnetizatio n

detectio n media p er o rmance

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ISO 17638:2016(E)

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work o f preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters o f electrotechnical standardization. The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the di fferent types o f ISO documents should be noted. This document was dra fted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the possibility that some o f the elements o f this document may be the subject o f patent rights. ISO shall not be held responsible for identi fying any or all such patent rights. Details o f any patent rights identified during the development o f the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is in formation given for the convenience o f users and does not

constitute an endorsement.

For an explanation on the meaning o f ISO specific terms and expressions related to con formity assessment,

as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html. The committee responsible for this document is ISO/TC 44, Welding and allied processes, Subcommittee SC 5, Testing and inspection of welds. This second edition cancels and replaces the first edition (ISO 17638:2003), which has been technically

revised.

Requests for o fficial interpretations o f any aspect o f this document should be directed to the Secretariat o f ISO/TC 44/SC 5 via your national standards body. A complete listing o f these bodies can be found at

www.iso.org.

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INTERNATIONAL STANDARD

ISO 17638:2016(E)

Non-destructive testing of welds — Magnetic particle testing 1 Scope T h i s do c ument s p e ci fie s te ch nique s

for

de te c tion o f s u r face i mp er fe c tion s i n weld s i n

ferromagne tic

materi a l s , i nclud i ng the he at a ffe c te d z one s , b y me a n s o f magne tic p a r ticle te s ti ng. T he te ch n ique s are s uitable

for

mo s t weld i ng pro ce s s e s and j oi nt con fig uration s . Va ri ation s i n the b a s ic te ch n ique s that

wi l l provide a h igher or lower te s t s en s itivity a re de s crib e d i n

Annex A.

T h i s do c ument do e s no t s p e c i fy accep ta nce level s o f the i nd ic ation s . Fu r ther i n formation on accep ta nce level s

for

i nd ication s may b e

fou nd

i n I S O 2 3 2 78 or i n pro duc t or appl ic ation s tandard s .

2 Normative references T he

fol lowi ng

do c u ments are re ferre d to i n the tex t i n s uch a way th at s ome or a l l o f thei r content

con s titute s re qu i rements o f th i s do c u ment. For date d re ference s , on ly the e d ition cite d appl ie s . For u ndate d re ference s , the late s t e d ition o f the re ference d do c ument (i nclud i ng a ny amend ments) appl ie s .

ISO 3059, Non-destructive testing — Penetrant testing and magnetic particle testing — Viewing conditions ISO 9934-1:2015, Non-destructive testing — Magnetic particle testing — Part 1: General principles ISO 9934-2, Non-destructive testing — Magnetic particle testing — Part 2: Detection media ISO 9934-3, Non-destructive testing — Magnetic particle testing — Part 3: Equipment 3 Terms and definitions For the pu r p o s e s o f th i s do c u ment, the term s and defi nition s given i n I S O 1 2 70 7 and I S O 176 3 5 apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses: — IEC Electropedia: available at http://www.electropedia.org/ — ISO Online browsing platform: available at http://www.iso.org/obp 4 Safety precautions Sp e c ia l con s ideration s ha l l b e given to toxic, i n fl am mable a nd/or volati le materi a l s , ele c tric a l s a fe ty and u n fi ltere d U V rad i ation . M agne tic p ar ticle te s ti ng o ften c re ate s h igh magne tic field s clo s e to the obj e c t under te s t and the magne ti s i ng e qu ipment. I tem s s en s itive to the s e field s shou ld b e e xclude d

from

s uch are as .

5 General 5.1 Information required prior to testing P rior to te s ti ng , the

fol lowi ng

item s s ha l l b e s p e ci fie d (where appl ic ab le) :

a)

s p e c i fic te s t pro ce dure;

b)

cer ti fic ation re qu i rements

© ISO 2016 – All rights reserved

for

N D T p ers on nel;

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ISO 17638:2016(E)

c) extent o f coverage; d) state o f manu facture; e) testing techniques to be used; f

) overall per formance test;

g) any demagnetization; h) acceptance level; i)

action necessary for unacceptable indications.

5.2 Additional pre-test information

Prior to testing, the following additional information can also be required: a) type and designation o f the parent and weld materials; b) welding process; c) location and extent o f welds to be tested; d) joint preparation and dimensions; e) location and extent o f any repairs; f

) post-weld treatment (i f any);

g) surface conditions.

Operators may ask for further in formation that could be help ful in determining the nature o f any

indications detected.

5.3 Personnel qualification

Magnetic particle testing o f welds and the evaluation o f results for final acceptance shall be per formed by qualified and capable personnel. It is recommended that personnel be qualified in accordance with ISO 9712 or an equivalent standard at an appropriate level in the relevant industry sector. 5.4 Surface conditions and preparation

Areas to be tested shall be dry unless appropriate products for wet sur faces are used. It may be necessary to improve the sur face condition, e.g. by use o f abrasive paper or local grinding to permit

accurate interpretation of indications.

Any cleaning or sur face preparation shall not be detrimental to the material, the sur face finish or the magnetic testing media. Detection media shall be used within the temperature range limitations set by

the manufacturer.

5.5 Magnetizing 5.5.1

Magnetizing equipment

General magnetization requirements shall be in accordance with ISO 9934-1:2015, Clause 8. Unless otherwise specified, for example, in an application standard, the following types o f alternating

current-magnetizing equipment shall be used:

a) electromagnetic yokes; 2

© ISO 2016 – All rights reserved

ISO 17638:2016(E)

b) current flow equipment with prods; c) adjacent or threading conductors or coil techniques. DC electromagnets and permanent magnets may only be used by agreement at the time o f enquiry

and order. The magnetizing equipment shall conform to ISO 9934-3. Where prods are used, precautions shall be taken to minimize overheating, burning or arcing at the

contact tips. Removal o f arc burns shall be carried out where necessary. The a ffected area shall be tested by a suitable method to ensure the integrity o f the sur face. 5

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For the verification o f magnetization, see ISO 9934-1:2015, 8.2. For structural steels in welds, a tangential field between 2 kA/m to 6 kA/m (r.m.s.) is recommended. The adequacy o f the sur face flux density shall be established by one or more o f the following methods: a) by testing a representative component containing fine natural or artificial discontinuities in the least favourable locations; b) measurement o f the tangential field strength as close as possible to the sur face using a Hall e ffect probe; the appropriate tangential field strength can be di fficult to measure close to abrupt changes in the shape o f a component or where flux leaves the sur face o f a component; c) calculation o f the approximate current value in order to achieve the recommended tangential field strength; the calculation can be based on the current values specified in Figure 5 and Figure 6 ; d) by the use o f other methods based on established principles. Flux indicators (i.e. shim-type) placed in contact with the sur face under test provide a guide to the magnitude and direction o f the tangential field strength, but should not be used to veri fy that the tangential field strength is acceptable.

NOTE

Information on b) is given in ISO 9934-3.

5.6 Application techniques 5.6.1

Field directions and testing area

The detectability o f an imper fection depends on the angle o f its major axis with respect to the direction o f the magnetic field. This is explained for one direction o f magnetization in Figure 1.

© ISO 2016 – All rights reserved

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ISO 17638:2016(E)

Key

1 2 3 4

magnetic field directio n o p timum s ens itivity reducing s ens itivity

α αmin αi

angle b etween the magnetic field and the directio n o f the imp er fectio n

minimum angle for imperfection detection example of imperfection orientation

ins u fficient s ens itivity

Figure 1 — Directions of detectable imperfections

To ensure detection of imperfections in all orientations, the welds shall be magnetized in two directions f using one or more magnetization methods. approxi mately p erp end icu l ar to e ach o ther with a ma xi mum devi ation o

3 0 °. T h i s ca n b e ach ieve d

Te s ti ng i n on ly one field di re c tion i s no t re com mende d but may b e c a rrie d out i f s p e ci fie d,

in an application standard.

for

exa mp le,

When u s i ng yoke s or pro d s , there wi l l b e an a re a o f the comp onent i n the vic i nity o f e ach p ole pie ce or tip that wi l l b e i mp o s s ible to te s t due to e xce s s ive magne tic field s treng th . T h i s i s u s ua l ly s e en as

furring of particles. Care shall be taken to ensure adequate overlap of the testing areas as shown in Figure 2 and Figure 3.

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© ISO 2016 – All rights reserved

ISO 17638:2016(E)

Dimensions in millimetres

Key d s ep aratio n b etween the p o les (yo ke/p ro d )

Figure 2 — Examples of effective testing area (shaded) for magnetizing with yokes and prods

© ISO 2016 – All rights reserved

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ISO 17638:2016(E)

Key

1 effective area 2 overlap Figure 3 — Overlap of effective areas 5.6.2

Typical magnetic testing techniques

M agne tic p ar ticle te s ti ng te ch nique s

Figure 5 and Figure 6

. Va lue s a re given

for

com mon weld j oi nt con figu ration s are s hown i n

for gu ida nce

o f magne ti z ation and field overlap s shou ld b e u s e d

Figure 4,

pu rp o s e s on ly. Where p o s s ible, the s ame d i re c tion s

for

o ther weld ge ome trie s to b e te s te d . T he width

o f the flu x c u rrent (i n c as e o f flu x c u rrent te ch n ique) or o f the magne tic flow (i n c a s e o f magne tic flow te ch n ique) p ath i n the materi a l,

d, shall be greater than or equal to the width of the weld and the

heat affected zone +50 mm and in all cases, the weld and the heat affected zone shall be included in the effective area. The direction of magnetization with respect to the orientation of the weld shall be s p e c i fie d .

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© ISO 2016 – All rights reserved

ISO 17638:2016(E)

Dimensions in millimetres

d ≥ 75 b ≤ d/2 β ≈ 90º

d1 ≥ 75 b1 ≤ d1 /2 b2 ≤ d2 – 50 d2 ≥ 75

d1 ≥ 75 d2 ≥ 75 b1 ≤ d1 /2 b2 ≤ d2 − 50

d1 ≥ 75 d2 > 75 b1 ≤ d1 /2 b2 ≤ d2 − 50

Key

1 longitudinal cracks 2 transverse cracks Figure 4 — Typical magnetizing techniques for yokes

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ISO 17638:2016(E)

Dimensions in millimetres

d ≥ 75 b ≤ d/2 β ≈ 90º

d ≥ 75 b ≤ d/2

d ≥ 75 b ≤ d/2

d ≥ 75 b ≤ d/2

Figure 5 — Typical magnetizing techniques for prods, using a magnetizing current prod spacing

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© ISO 2016 – All rights reserved

ISO 17638:2016(E)

Dimensions in millimetres

a ≤ 50 N· I ≥ 8 D

a ≤ 50 N· I ≥ 8 D

20 ≤

20 ≤

a ≤ 50 N· I ≥ 8 D

20 ≤

Key

number of turns current (r.m.s) distance between weld and coil or cable

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5.7 Detection media 5.7.1

General

D e te c tion me d i a may b e either i n d r y p owder

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T he de te c tion me d i a u s e d sh a l l

© ISO 2016 – All rights reserved

n



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p

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form

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or magne tic i n ks i n accorda nce with I S O 9 9 3 4 -2 .

a

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c

e

the re qu i rements o f I S O 9 9 3 4 -2 .

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ISO 17638:2016(E)

Indications obtained with the medium to be verified shall be compared against those obtained from a medium having a known and acceptable per formance. For this purpose, the re ference indications may be

— real imperfections, — photograph(s), and — replica(s).

5.8 Viewing conditions

The viewing conditions shall be in accordance with ISO 3059. 5.9 Application of detection media

A fter the object has been prepared for testing, the detection medium shall be applied by spraying, flooding or dusting immediately prior to and during the magnetization. Following this, time shall be allowed for indications to form be fore removal o f the magnetic field. When magnetic suspensions are used, the magnetic field shall be maintained within the object until the majority o f the suspension carrier liquid has drained away from the test sur face. This will prevent any indications being washed away. Depending on the material being tested, its sur face condition and magnetic permeability, indications will normally remain on the sur face even a fter removal o f the magnetic field due to residual magnetism within the part (mainly at the location o f the poles). However, the presence o f residual magnetism shall not be presumed and post evaluation techniques a fter removal o f the prime magnetic field source are only permitted when a component has been proven by an overall per formance test to retain magnetic

indications.

5.10 Overall performance test

When specified, an overall per formance test o f the system sensitivity for each procedure shall be carried

out on site. The performance test shall be designed to ensure a proper functioning of the entire chain of parameters including the equipment, the magnetic field strength and direction, sur face characteristics, detection media and illumination. The most reliable test is to use representative test pieces containing real imper fections o f known type, location, size and size-distribution. Where these are not available, fabricated test pieces with artificial imper fections or flux shunting indicators o f the cross or disc or shim-type may be used.

The test pieces shall be demagnetized and free from indications resulting from previous tests. NOTE

It can be necessary to per form an overall per formance test o f the system sensitivity for each specific

procedure on site.

5.11 False indications

False indications which may mask relevant indications can arise for many reasons, such as changes in magnetic permeability, very important geometry variation in, for example, the heat a ffected zone. Where

masking is suspected, the test surface shall be dressed or alternative test methods should be used. 5.12 Recording of indications

Indications can be recorded in one or more o f the following ways by using: a) description in writing; b) sketches; 10

© ISO 2016 – All rights reserved

ISO 17638:2016(E)

c) photography; d) transparent adhesive tape; e) transparent varnish for “ freezing” the indication on the sur face tested; f

) peelable contrast coating;

g) video recording; h) magnetic particle dispersion in an epoxy curable resin; i)

magnetic tapes;

j)

electronic scanning.

5.13 Demagnetization

A fter testing welds with alternating current, residual magnetization will normally be low and there will generally be no need for demagnetization o f the object under test. I f demagnetization is required, it shall be carried out using a defined method and to a predefined level.

For metal cutting processes, a typical residual field strength value o f H < 0,4 kA/m is recommended. 5.14 Test report

A test report shall be prepared. The report should contain at least the following: a) name o f the company carrying out the test; b) the object tested; c) date o f testing; d) parent and weld materials; e) any post weld heat treatment; f

) type o f joint;

g) material thickness; h) welding process(es); i)

temperature o f the test object and the detection media (when using media in circulation) throughout testing duration;

j)

identity o f the test procedure and description o f the parameters used, including the following: — type o f magnetization; — type o f current; — detection media; — viewing conditions;

k) details and results o f the overall per formance test, where applicable; l)

acceptance levels;

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ISO 1 763 8: 2 01 6(E)

m)

de s crip tion a nd lo c ation o f a l l re cordable i nd ic ation s;

n)

te s t re s u lts with re ference to accep ta nce level s;

o)

name s , relevant qua l i fic ation and s ignature s o f p ers on nel who c arrie d out the te s t.

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© ISO 2016 – All rights reserved

ISO 17638:2016(E)

Annex A

(informative) Variables affecting the sensitivity of magnetic particle testing

A.1 Surface conditions and preparation T he ma xi mu m te s t s en s itivity that ca n b e ach ieve d b y a ny magne tic te s ti ng me tho d i s dep endent on

ma ny va riable s

but c a n

be

s eriou s ly a ffe c te d

b y the

s u r face

rough ne s s

o f the

obj e c t a nd

any

i rre gu l aritie s pre s ent. I n s ome c as e s , it c a n b e ne ce s s a r y to

—

d re s s underc ut a nd s u r face i rre gu l aritie s b y gri nd i ng , a nd

— remove or reduce the weld reinforcement. Su r face s

covere d

with

a

th i n

non- ferromagne tic

co ati ngs

up

to

50

µm

th ickne s s

may

be

te s te d

provided the colour is contrasting with the colour of the detection medium used. Above this thickness, f f f proceeding with the test. the s en s itivity o

the me tho d de cre as e s a nd may b e demon s trate d to b e s u ficiently s en s itive b e ore

A.2 Magnetizing equipment characteristics T he u s e o f a lternati ng c urrent give s the b e s t s en s itivity

for

de te c ti ng s ur face i mp er fe c tion s .

Yoke s pro duce an ade quate magne tic field i n s i mple butt-weld s but where the flu x i s re duce d b y gap s or the p ath i s e xce s s ive th rough the obj e c t, a s i n T-j oi nts a re duc tion o f s en s itivity c an o cc u r. For complex j oi nt con figu ration s , i . e . bra nch con ne c tion s with an i ncl i ne d angle o f le s s than 9 0 °, te s ti ng u s i ng yoke s m ight b e i nade quate . P ro d s or c able wrappi ng with c u rrent flow wi l l, i n the s e c as e s , prove

more suitable.

A.3 Magnetic field strength and permeability T he field s treng th re qu i re d to pro duce an i nd ic ation s trong enough to b e de te c te d du ri ng magne tic p a r ticle te s ti ng i s dep endent mai n ly on the magne tic p erme abi l ity o f the obj e c t. G enera l ly, magne tic p erme abi l ity i s h igh i n s o fter magne tic materi a l s ,

for

exa mple, low a l loy s te el s

and low i n h arder magne tic materi a l s , i . e . mar ten s itic s te el s . B e c au s e p erme abi l ity i s a

func tion

o f the

magne ti z i ng c u rrent, low p erme abi l ity materi a l s u s ua l ly re qu i re appl ic ation o f a h igher magne ti z ation va lue than do s o fter a l loys to pro duce the s a me flu x den s ity. I t i s e s s enti a l, there fore, to e s tabl i sh that flu x den s ity va lue s are ade quate b e fore b e gi n n i ng the magne tic p ar ticle te s ti ng.

A.4 Detection media M agne tic p a r ticle s u s p en s ion s wi l l u s ua l ly give a h igher s en s itivity

for

de te c ti ng s u r face i mp er fe c tion s

tha n d r y p owders .

F luore s cent magne tic de te c tion me d i a u s ua l ly give a h igher te s t s en s itivity tha n colou r contra s t me d ia, b e c au s e o f the h igher contra s t b e twe en the darkene d b ackgrou nd and the fluore s cent i nd ic ation . T he s en s itivity o f the fluore s cent me tho d wi l l , never thele s s , de cre as e i n prop or tion to any i ncre as e i n the

roughness of the surface to which magnetic particles adhere and can cause a disturbing background fluore s cence .

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ISO 1 763 8: 2 01 6(E)

Where the b ackground i l lu m i nation c an no t b e ade quately lowere d or where b ackgrou nd fluore s cence i s d i s tu rbi ng , colou re d de te c tion me d i a i n conj u nc tion with the s mo o th i ng e ffe c t o f a contra s t aid wi l l us ua l ly give b e tter s en s itivity.

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ISO 17638:2016(E)

Bibliography

[1] [2] [3] [4]

ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel ISO 12707, Non-destructive testing — Magnetic particle testing — Vocabulary ISO 17635, Non-destructive testing of welds — General rules for metallic materials ISO 23278, Non-destructive testing of welds — Magnetic particle testing — Acceptance levels

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ISO 1 763 8: 2 01 6(E)

ICS  25.160.40

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