TABLE OF CO~TEi\TS

INTRODUCTION ................................................................................................................................... MTl

Basic principles .............................................................................................................................. MTl-1
MAGNETIC PROPERTIES ................................................................................................................. MT2
Magnetism ...................................................................................................................................... MT2-1
Lines of force .................................................................................................................................. MT2-l
Material characteristics .................................................................................................................. MT2-3
Permeability (!J.) .............................................................................................................................. MT2-4
Retentivity ...................................................................................................................................... MT2-4
Magnetic flux (e) and magnetic flux density (B) ........................................................................... MT2-4
Magnetic field strength (H) ............................................................................................................ MT2-5
Coercive force ................................................................................................................................ MT2-5
Magnetic hysteresis ........................................................................................................................ MT2-5
Penetration of magnetic flux .......................................................................................................... MT2-6
Flux leakage ................................................................................................................................... MT2-6
Electromagnetism ........................................................................................................................... MT2-7
CONSIDERATIONS WHEN USING MPI ......................................................................................... MT3
Limitations of MPI ........................................................................................................................ MT3-1
General considerations ................................................................................................................... MT3-l
Surface conditions .......................................................................................................................... MT3-1
MAGNETIZING METHODS & APPARATUS ................................................................................ MT4
Continuous magnetisation method ................................................................................................. MT4-1
Residual magnetisation method ..................................................................................................... MT4-l
Permanent magnets ........................................................................................................................ MT4-l
Electromagnetic yokes ................................................................................................................... MT4-2
Current flow ................................................................................................................................... MT4-3
Induction methods .......................................................................................................................... MT4-6
THE DETECTING MEDIUM .............................................................................................................. MTS
Dry powders ................................................................................................................................... MTS-1
Inks ................................................................................................................................................. MTS-1
Health and safety considerations .................................................................................................... MTS-2
VIEWING CONDITIONS ..................................................................................................................... MT6
Non-fluorescent inks and powders ................................................................................................. MT6-1
Fluorescent inks and powders ........................................................................................................ MT6-1
Safety .............................................................................................................................................. MT6-2
Electromagnetic spectrum .............................................................................................................. MT6-3
DEMAGNETIZATION .......................................................................................................................... MT7
MAGNETIC FIELD INDICATORS ..................................................................................................... MT8
Portable magnetic field strength meters (magnetometers) ............................................................. MT8-1
Shim type/foil strips (trade name Castro! Strips/Ely Strips) .......................................................... MT8-l
The ASME field indicator .............................................................................................................. MT8-2
The Berthold penetrameter ............................................................................................................. MT8-2
1-Iall effect meters ........................................................................................................................... MT8-3
Performance checks ....................................................................................................................... MTS-3
Alternative test block(s) ................................................................................................................. MTS-4

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 TABLE OF CONTENTS

.REPORTIN"G........................................................................................................................................... MT9
Interpretation definitions ................................................................................................................ MT9-l
Preservation of indications ............................................................................................................. MT9-1
CURRENT TYPES .............................................................................................................................. MTlO
Alternating current ....................................................................................................................... MTI 0-1
Direct current. ............................................................................................................................... MTI 0-1
COS~ REGULATIONS .................................................................................................................... MTll
Scope ............................................................................................................................................ MTll-1
Responsibilities ............................................................................................................................ MTll-1
Occupational Exposure Limits (EH40- January 2002) ............................................................... MTll-1
LIST OF APPLICABLE STANDARDS ............................................................................................ MT12

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(!) Ruant & T P O'Ntlll
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TPO'Nei/1

:'IIOTf.S Magnetic particle inspection (MPI) is an NDT method which may only be used on
ferromagnetic materials to detect surface breaking discontinuities and also, in certain
rerromagnetic materials are cases, slight sub-surface discontinuities up to 2 nun or 3 m.m below the material's
those which may be surface.
magnetized. e.g. iron. cobalf.O
nickel and many oftheir
alloys.
BASIC PRINCIPLES
A magnetic field is introduced into a specimen to be tested, then fine particles of
ferromagnetic powder, or ferromagnetic particles in a liquid suspension, are applied to
20 the area being tested. Any discontinuity in the test area which cuts across the magnetic
The area being tested is field creates a lealmge field. A leakage field has a north and south pole on either side
known as the 'test area. of it, and therefore will attract the ferromagnetic particles in great numbers.
It is common on site work to use black inks as the detecting medium; these are usually
contrasted against a white paint background which has been pre-applied. In
workshops and similar, it is more common to use fluorescent inks which are usually
30
green/yellow. Fluorescent inks or powders are automatically contrasted against a deep
violet background created by the use of an ultraviolet (UV-A) light, this is essential to
cause fluorescence of the particles, although the use of a darkened inspection area is
required. ~...2!!!!~e!1nt is not required with fluorescent inks.
Fluorescent inks or powders are more sensitive at detecting defects compared to non-
40 fluorescent inks or powders, because of the greater contrast achieved between the
detecting medium and the background.
There are many ways to apply a magnetic field, e.g. by the use of permanent magnets,
electromagnetic yokes, coils, prods, cables and other devices.
A basic sequence of operations for the examination of a weld using MPI with a
50 permanent magnet and black ink is shown below:

1. Clean area using a wire brush if required.

2. Apply a thin layer of white contrast paint.
3. When the paint is dry, straddle the magnet over the weld at 90 to the weld axis.
60 4. Apply ink (typicaliy 1.25% to 3.5% ferromagnetic particles to a paraffin base).
5. Interpret the area. Look for indications with their length lying along the same
axis as the weld. Evaluate in accordance with the relevant specification.
6. To look for transverse weld defects, turn magnet approximately 90 and re-apply
the ink.
70 7. Interpret the area. Look for indication with their length perpendicular to the weld
axis. Evaluate in accordance with the relevant specification.

80

90

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MAGNETISM
All materials consist of atoms and molecules which may or may not have a permanent
10 magnetic influence depending on the electron configuration within the material.
Atoms in magnetic materials group together in regions called magnetic domains; each
domain has its own north and south pole. When these domains are randomly
positioned, the material is unmagnetized. If the domains are aligned in a common
direction, then the material will be magnetized and the material itself will have its own
north and south pole.
20

H s N s
H N .s
s s.t1 N ,(f N N
s
30 s
H s N , s N s

Figure 2.1 - Position ofdomains in unmagnetized material

40

s N
N H s
H S
N S

50
N N
*S
N-ti-s
N :s N
*S N-\1- s N

Figure 2.2- Position ofdomains in magnetized material

60

The domains can be aligned by bringing them within an existing magnetic field. If the
A more simple definition
would be 'the properties of domains remain aligned when they are removed from the influence of the magnetic
certain metals to allract or field, then the material is said to be permanently magnetized.
repel certain other metals.
The poles of magnetized materials have an inherent attraction/repulsion effect. If two
70 pieces of magnetized material are placed with their dissimilar poles end to end there is
an attraction, but if the poles are alike then there is a repulsion, therefore:
like poles repel, unlike poles attract.

80 LINES OF FORCE
Faraday used the concept of lines of force to explain what happens in the space
The symbol (Phi) is used co between two magnets. He suggested properties for these lines of force , which he
represent magnetic lines of imagined as spreading out from all magnetic poles into the surrounding space.
force. Magnetic lines offorce
may also be termed magnetic
flux. 90

100

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'\OfE!'>
Magnetic flux

A 'magnetograplz is a
pictorial i/lustrotioll of a 10
magnetic field. )

~ -- ----
--
20
...:-
I
/
/'
r
-
'- ......
.............
\
\
---- - _...._ _ ----- ~/

--- -- - -
- J
'- .,.,..-/
_.,.,._ - ---- -------
Figure 2.3 - Lines offorce around a bar magnet ,)J.J-1
30 By assuming the lines were in tension, like pieces of stretched elastic, he could account
for the attraction of unlike poles, since the lines of force stretch from one pole to
another.

40

50

Figure 2.4 - Lines offorce for unlike poles

But, the tension of the lines of force must increase as they shorten, since the repulsive
force between two like poles increases as the poles approach. With like poles, the lines
60
of force also tend to curve outwards, seemjng to suggest that they repel each other.
Faraday used this hypothesis to account for the repulsion of like poles.

/'/ t //"/"
;/ 1 I I~~-----.
/; / I II
70 // \
N
/
/
I / /
I I /
I I I I I
I I I
..
80 J /
-~,r...J/ /
I I I
/// ~ .,~

Figure 2. 5 - Lines offorce for like poles

The properties of magnetic lines of force are as follows:
90 a. They form closed loops between north and south poles.
b. They do not cross one another.
c. They seek paths of least magnetic resistance.
d. Their density decreases with increasing distance from the poles, i.e. the number of
lines of force in a unit area decreases.
e. They are considered to have direction, that is: from the north pole to south pole
100 external to the magnet, and from the south pole to the north pole within the
magnet.

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1\0TES MATERIAL CHARACTERISTICS

The degree to which materials are capable of being influenced by a magnetic field
varies greatly from material to material, however, they fall into three specific
10 categories defined by their behaviour in the magnetic field.

Diamagnetic materials
These are, to a very slight degree, repelled by a magnetic field and include copper,
titanium and most non-metals.
20
----
---- ---
Examples of permeability
Diamagnetic materials:
Gold - 0.999964!'
---
---
---
-- ---- - -- - --.___--.._--------
-----
------ ---
Silver - 0. 99998ji
Copper - 0. 99999Jp 30
----
-- ---
Lead - 0.999983p
---~~-
--.-.... .__.___ --- -- - - - --
Bismuth - 0.99983p
~ --- -----
----
_.....
_.....-
---------
Figure 2. 6 - Lines offorce for a diamagnetic material
40
Paramagnetic materials Paramagnetic materials
Air = 1.00000036p
Aluminium = /.00002/p These are very weakly attracted by a magnetic field and include oxygen and most
metals including austenitic stainless steel, magnesium, molybdenum, lithium and
tantalum.
50

60
Figure 2. 7- Lines offorce for a paramagnetic material

Ferromagnetic materials
These are strongly attracted by a magnetic field and include iron, cobalt, nickel and
Examples of permeability many of their alloys. They also exhibit permanent magnetism and can themselves be
Ferromagnetic materials: 70 magnetized.
Cobalt- 250p
Nickel - 600p
Annealed iron - 6000p
0. 9% carbon steel- 100
Super malloy- I x I 0 6 80
Cold rolled iron - 2000,u
MU alloy = 80,000p
----",
____

\
\\ \
\" ==
'-

90 Figure 2.8 - Lines offorce for a ferromagnetic material

100

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'iOTF.S PERMEABILITY (J.t)

For magnetic particle inspection, the only materials of interest are those which are
ferromagnetic. Within this group, some materials are more easily magnetized than
10 others, that is to say, more permeable.
To permeate means to spread through. In this context it refers to the ease by which the
magnetic lines of force are spread through the materiaL Soft iron and low carbon steel
have a high permeability, i.e. they are easy to magnetise. Hard iron and high carbon
steel have a low permeability, i.e. they are difficult to magnetise.
20 Permeability (!l) may be calculated by dividing the magnetic force (H) applied, into the
flux density (B) achieved:
B
p=-
H
Magnetic force {H) may also
be termed 'magnetic field The permeability of a material may be given a value based on a ratio when compared
strength. 30
with free space. These values vary depending on alloy composition, heat treatment
Flux density (B) may be and any working applied.
termed 'magnetic induction .

RETENTIVITY
40 When a magnetizing force is removed from a ferromagnetic material the amount of
magnetism remaining will vary between materials and depends upon the permeability
of the material. The remaining magnetism is termed residual magnetism and the
material is said to have retentivity or retained magnetism.
If a material has high permeability it is easily magnetized but it will just as easily give
up the magnetic force, therefore it has a low retentivity.
50
If a material has low permeability it is very difficult to magnetise, that is to say it has
Reluctance is the reciprocal high magnetic reluctance, but once magnetization has been achieved then it does not
ofpermeability, i.e. .!. give up the magnetic force easily, therefore it has high retentivity.
p
High permeability = low retentivity
60 Low permeability= high retentivity

MAGNETIC FLUX(~) AND MAGNETIC FLUX DENSITY {B)

When a specimen is magnetized, lines of force or flux exist within the specimen - the
BS EN ISO 9934-1: 2001
Magnetic particle testing. 70
stronger the magnetizing force applied, the greater the amount of flux produced. The
states a requirement of magnetizing force may be applied by using a permanent magnet or electrically
I testa in the component's operated magnetic flow apparatus, or by passing an electric current through the
swface achieved with a specimen.
tangential field strength of
2 k.Aim (rms). Magnetic flux is measured in webers (Wb).

80 The number of lines of force (or flux) passing transversely through a given cross-
sectional area is known as the flux density (B). Flux density is measured in tesla (T).
BS 6072 - Magnetic particle 2
flaw detection. states that 1 Wb/m = 1 tesla (T).
MPI shall only be carried out
if the magnetic flux density The old (cgs) unit for flux density which is still widely encountered is the gauss:
level at the suiface oft he 2
test area is equal to. or 1 gauss= 1 line offorce/cm .
90
greater than, 0.72T. This 4
level afflux density is 10,000 (10) gauss= 1 testa.
approximately one third of
that required to magnetically 1 gauss= 0.1 mT.
saturate most steels.

100

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i\OTES MAGNETIC FIELD STRENGTH (H)

The magnetic field strength or magnetizing force is that which is needed to induce a
flux in a magnetic circuit and is measured in amperes per metre (A/m), or in old (cgs)
10 units, the oersted (Oe).
1 oersted= 79.58 amperes per metre,

COERCIVE FORCE
20 Coerce means to forcibly control; in this context it relates to the reverse magnetizing
force necessary to remove remnant or residual magnetism for demagnetization of a
part.

30 MAGNETIC HYSTERESIS
Most of the magnetic properties of materials of practical concern in MPI are defmed by
the magnetic hysteresis loop or B&H curve.
When an mm1agnetized piece of ferromagnetic material is exposed to a gradually
increasing positive magnetic force and the strength of the induced flux density (B) is
plotted against the magnetizing force (H), a B&H curve is produced. If the plot
40
continues in the opposite direction a hysteresis loop evolves.

+B +ve
b b
b

50
Residual
Virgin
Curve

H +H

60

e
Coercive
Force I
-B
Vt

70 Fig. 2.9 A typical hysteresis loop generated by an a. c. current.

As the magnettzmg force (H) is increased, the induced magnetic field (B) also
increases until it reaches its saturation point (b), at this point the material is said to be
magnetically saturated, that is the point when the maximum flux density has been
80 reached.
When the magnetic force (H) is reduced, the flux density (B) also reduces but falls
behind the original curve so that when H is back to zero there is still some magnetic
flux in the material (c). This is a measure of the material's retentivity.
If the polarity of the magnetizing force is now reversed, B will return to zero (d). This
90 point represents the coercive force required to remove the residual magnetism from the
material.
By continuing all the previous actions in the opposite direction a complete loop will be
formed.
When a.c. is used for magnetizing a specimen, a complete hysteresis loop is produced
100 with each cycle of current; in the U.K. this is 50 times per second.

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A material which exhibits a hysteresis loop with a wide appearance will have high
retentivity and therefore may be useful for making permanent magnets. A material
which exhibits a hysteresis loop with a narrow appearance will have low retentivity
and therefore may by useful for making magnetic particles.
10
The gradient of the loop also gives information regarding on the usefulness of
materials for use in magnetising apparatus, for making magnetic particles or for
magnetising purposes. For example, a material which exhibits a steep gradient will
attain a high flux density when using a low magnetizing force.

20
PENETRATION OF MAGNETIC FLUX
Magnetic particle inspection is primarily used for the detection of surface breaking
discontinuities and only in ferromagnetic materials. This is because the magnetic
fields induced are concentrated at the surface of the components. However, sub-
surface discontinuities may be detected if using permanent magnets or electrical
30
systems using direct or rectified current, because the magnetic field penetrates much
further into the test specimen in comparison with MPI test methods which use
alternating current. It is unlikely that any form of MPI would be used to detect defects
deeper than 2 mm or 3 mm below the surface.

40
Weak & diffused flux leakage field

50

Fig. 2.10- Flux leakages around discontinuities at different depths using a standard
permanent magnet used in MPJ. (A) will not be detected. (B) may be detected if the
60 appropriate technique is used and (C) should easily be detected.

MPI test equipment using alternating current as an output produces a high density
magnetic flux at the surface of the test component. This phenomena, known as the
skin effect, produces a far stronger flux leakage field on surface breaking, or near
70 surface discontinuities, compared to permanent magnets or direct current test
equipment.
The depth of flux penetration is governed by the wave frequency of the alternating
current, the conductivity of the test material and its permeability. If any of these
variables increase, the depth of penetration will decrease.
80 It is difficult to try and interpret very weak and diffused MPI indications which could
be from sources other than defects, e.g. caused by rough/uneven surfaces or changes in
permeability. Because of this problem, sub-surface, or body defects, would normally
be located by other methods of NDT, assuming the detection of sub-surface defects is
a requirement.

90
FLUX LEAKAGE
When a magnetic field is created within a ferromagnetic specimen, lines of magnetic
flux are developed and flow through and around the material completing a circuit.
Magnetic particle inspection relies on a leakage of flux occurring within this circuit,
100 this may be caused by a break or discontinuity in the material.

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\ OTES Because it is a change in magnetic permeability that causes a leakage field, flux
leakages may also be caused by changes in metallurgy.
Opposite poles attract, therefore any break or discontinuity causing a flux leakage will,
10 because of the magnetic poles, attract a ferromagnetic material such as iron powder.
This would accumulate at the area of the leakage field and give an indication of the
It is a change in magnetic defect's existence.
permeability that causes a
leakage field. Where the flux leaves the circuit a north pole is created.
Wltere the flux re-enters the circuit a south pole is created.
20 For a defect to be detected by MPI it must interrupt the lines of force. Any linear
Cracks may have very defects running parallel with the flux or small non-linear defects do not break the lines
irregular contours. they of force, they bend around these defects taking the path of least resistance; these
therefore may sometimes be defects therefore remain undetected.
detected using MPI when the
lines offorce are parallel, or MPI is most effective in detecting defects with their major axis at 90 to the lines of
close to parallel. to the force, but will usually remain effective down to about 45 of this axis
30
crack's major axis.
(BS EN 1290: 1998 and BS EN ISO 9934 : 2001 quotes 60). Below that it is
urtli.kely that the defect will be found, therefore in order to examine a specimen
A sharp change in contour completely, the lines of force must be applied in different directions.
can also create a flux
leakage creating an MPI
indication known as
furring'. Furring can also 40 ELECTROMAGNETISM
occur on flat surfaces when
there is an excessive amount There is a furtdamental relationship between electricity and magnetism; the movement
ofmagnetic flux. of an electric charge will create a magnetic force field around it, in a plane
perpendicular to the direction of travel of the electric charge.
Electrons that are moving in a current carrying conductor set up a magnetic field, the
50 direction and orientation of which are given by the right hand rule if we assume the
current flow, by convention, is opposite to electron flow; or the left hand rule if we
assume the direction of current flow is the same direction as the electTon flow .

60

70
Fig. 2.11 - Magnetic lines offorce in relation to current flow (I) using the left hand
rule. The symbol! is used to indicate the current flow, symbolises magnetic flux flow.

80

90

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Ruane & II UNIT l\IT3 CO~SIDERATIONS \\'liEN USING 1\IPI

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:\OTES 1. Magnetic particle flaw detection is capable of detecting cracks, non-metallic

inclusions and other discontinuities on or near the surface of ferromagnetic
materials.
10 2. The sensitivity of the inspection is not greatly impaired by the presence of foreign
matter within the flaws, unless the contaminate has magnetic properties similar to
the test piece (which is highly unlikely).

Both BS 6072 and

3. It is possible to inspect components that have been coated, e.g. with cadmium plate
BS EN 1290: 1998 quote or paint, providing the coating is not too thick (usually not greater than 50 Jlm)
a maximum thickness of with only a slight loss of sensitivity.
20
unbroken paint of 50 Jim.

LIMITATIONS OF MPI
1. MPI cannot be used on non-magnetic material.

30
2. The presence of surface coatings may reduce the sensitivity of the test. .x
3. Flaws that do not break the surface give diffused indications; these indications
from flaws become increasingly diffused with an increase in distance below the
surface.
4. Dimensional and/or structural variations, rough surfaces and certain types of
segregation or metallurgical changes associated with test items may give rise to
40
misleading indications. This could include non-relevant indications caused by a
change of section, too high amperage, a drilled hole near the surface or a
difference in hardness.

GENERAL CONSIDERATIONS:
a) BS EN ISO 9934-1 : 50
200/ refers to 1. All persons associated with magnetic flaw detection should be adequately trained
BSEN473for to an agreed level appropriate to their responsibility and have adequate eyesight.
personnel qualifications
and certification. 77Iis 2. It is necessary for operators and supervisors to observe the requirements of the
document requires Health and Safety at Work etc. Act 1974 and the COSHH Regulations; see
personnel to rea.d
UnitMTll.
Jaeger J I or Times 60
Roman N4.5 at a 3. Post cleaning may be necessary in circumstances where the magnetic particles or
distance of not less any background paint used, may be deleterious to the successful use of the
than 0.3m
component.
b) BS 6072 stated a
minimum nUJIIirement
for personnel to read
Jaeger J2 at not less 70 SURFACE CONDITIONS
than 0.5m. The better the surface condition, the more sensitive and reliable the test will be.
Therefore all contaminants such as paint, dirt, grease, oil, scale etc. should be removed,
Contrast paints should normally leaving if possible a smooth surface dressed to bright metaL
be in accordance with:
Where dressing is not possible and when black inks are being used, a coating of a
a) BS EN ISO 9934-2 Non- suitable white background contrast paint should be applied. When testing machined
Destructive testing - 80
parts with black ink, a contrast aid paint is not required due to the bright metal fmish
Magnetic particle
testing. giving a good contrast.
Part 2 : Characterisation Contrast paint should be applied thinly. Thick coats reduce the sensitivity of the
ofproducts. process and take longer to dry.

90 Contrast paints that are water based are not as toxic as those containing volatile
solvents (aerosol cans).

100

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CONTINUOUS MAGNETISATION METHOD

The continuous method is a testing method by which the magnetic ink or powder is
applied and the test area is viewed whilst the magnetising force is applied. This is
10 always considered to be the most sensitive method, whatever apparatus is used to
magnetise, due to the fact that the induced magnetic field is always the strongest whilst
the magnetising force is being applied.

RESIDUAL MAGNETISATION METHOD

20 The residual method is a testing method where the magnetic ink or powder is applied
and the test area is viewed after the magnetisiog force has been removed. The test is
performed using the residual magnetism left in the sample. This method is generally
only used on materials with a high retentivity. When multiple items are being tested
by the residual method, care must be taken to ensure that the components do not come
into contact with each other before the detecting media is applied, otherwise a
30 phenomena known as magnetic writing will occur.

PERMANENT MAGNETS
Permanent magnets are so called because they are able to maintain a magnetic field in
the surrounding space. The field strength can vary considerably, depending on the flux
40
density in the magnet and its shape.
The simplest form of permanent magnet is a bar magnet, which is basically a piece of
ferromagnetic material with a magnetic pole at each end.
If the bar was formed into a closed loop, then the magnetic field would be fully
contained within a closed circuit and no external field would exist. If a defect was
50
present in the loop, a flux leakage would still occur.
Neither bar magnets or ring (looped) magnets have any use in MPI. But, if a bar
magnet is simply formed into a U shape, the magnetic lines of force will be
concentrated in the gap between the magnetic poles; this provides an ideal
configuration for magnetic particle inspection.
60

70

80

90

Fig. 4.1 - Permanent magnets positioned for examining a weld

100

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:\ OTI:S Permanent magnets provide magnetic flow only in the specimen and produce a
longitudinal magnetic field between the poles.
The degree of magnetization in permanent magnets is detennined by the amount of
10
pull required to lift the magnet clear of the workpiece, or by its lifting power.
The pull offforce is the force that has to be applied to one pole to break its attraction to
the surface, whilst leaving the other pole attracted.
The lifting power is the ability of the magnet to lift a piece of ferromagnetic material
by attraction alone.
20
Certain specifications will state the minimum requjrements for the strengths of
permanent magnets. When not in use a permanent magnet should have a keeper placed
across the poles to prevent loss of magnetism.
a) BS EN ISO 9934-1 does
not specifically cover Some permanent magnets may have adjustable arms, others may have rollers attached
permane111 magnets. to the poles; the rollers are set to keep the magnet just clear of the surface and enable it
30 to be moved over the workpiece with relative ease.
b) BS 6072 stared tltat
permanefll magnets
sha/1/tave a power
Advantages of permanent magnets include:
capable of lifting 18 kg
witIt a pole spacing
No power supply required.
75 - 150 m,.z. The Inexpensive.
pull offforce slta/1
have a value equivalent40 No damage to the test piece from arcing.
to at least 9 kg. Relatively lightweight (easily portable).
They cling to vertical and overhead surfaces.
Both hands free after the magnet is placed onto the surface.
Ideal for explosive environments.
50 Disadvantages include:
Deterioration with wear.
Have to be pulled from the test surface.
Magnetic particles attracted to poles.
Limited application on awkward shapes.
60
No control over field strength (unless adjustable arms are used).
Only small areas examined in each position.
Keeper required when not in use.
Not recommended to be used in conjunction with flux indicators. ..:
70 Toxic material when machined.
Very hard.

ELECTROMAGNETIC YOKES {MF)

Electromagnetic yokes or electromagnets require a source of electrical energy which
80
may be a.c. or d.c.. The test method used is sometimes referred to as the magnetic flow
or magnetic flux path method, producing a longitudinal magnetic field.

90

\ I
' ...."t,_
100
- ~-
__ ..-- -- ~ -
-- _4--
....- --- ' ....... _ ~ ..... /
/
~

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 Ruane & II UNIT l\IT4 1\IAGNETIZING l\IETIIODS & APPARATUS
TPO'Ne/11

:"< OTES Fig. 4.2- An electromagnetic yoke

The yoke is made from highly permeable, low retentive steel, which is laminated to
reduce induction caused by eddy current flow (associated only with alternating current)
10 this also helps to prevent the yoke becoming permanently magnetized.
Magnetism is induced into the yoke by encircling it with a coil through which a current
is passed, the strength of the field produced can be varied in one of two ways:
As to BS EN/SO 9934-1. the
field strength available from the 1. By adjusting the current (amperage) flowing through the yoke - only certain
equipment may be determimu/ via electromagnets allow for this.
either: 20
2. By varying the distance between the pole pieces - most electromagnets allow for
a) practically testing an example
this but not all.
object with either a natural or
artificial flaw. Electromagnets may operate direct from the mains supply of 240V but are available at
b) measuring the tangential field 11 OV when required for site use.
strength as close to the surface as
possible. Note: permanent and 30 The field produced from an electromagnetic yoke is longitudinal, travelling from pole
d.c. electromagnets are not to pole as with permanent magnets, however the depth of the field within the test piece
recommended for use in th is will depend upon the type of current used to induce magnetism.
standard
Surface discontinuities will be more readily found using a.c., sub-surface defects will
c) BS EN ISO 9934-3 refiuiles the
llbove or a lift test of 4.5 kg or a
be more easily located using d.c.. The magnet will have a much greater pull on d.c.
500 x 250 x I 0 mm plate using but the flux will be less at the surface of the component being tested.
the tangential field strength 40
meter to measure the field The area of inspection for permanent and electromagnets is a rectangular area between
strength . the poles of the magnet(s).
BS 6072 stated for ac yokes a lift Advantages of electromagnetic yokes include:
tes1 of 4. 5 kg and a pull off tesl
of2.25 kg for a pole spacing of A.c. or rectified d.c. operation.
300 mm or less. de yokes had
the Slime requirements as 50 Controllable field strength (not in all cases).
pennanent magnets. Can be switched on/off as required.
No damage done to test piece.
Relatively lightweight.
A.c. yokes can be used to demagnetise.
BS EN ISO 9934-1 states 60
the area adjacent of the Disadvantages include:
poles (25 mm) to be
ignored. Power supply required.
Only small areas can be examined at each magnet location.
Leaves only one hand free.
70 D.c. yokes are not recommended to be used in conjunction with flux indicators.

CURRENT FLOW (CF)

Current flow techniques produce a circular magnetic field by passing a current through
80 the test piece, i.e. concentric rings of magnetic lines of force radiate at 90 to the
current flow.

ar

90

Fig. 4.3- Current flow method on bar

100

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l'iOTES The current flow is normally obtained from a transformer supplying a.c. or a
transformer rectifier for d. c ..
The output voltage of current flow equipment is so low that there is no risk of
10 electrical shock to the operator from the equipment's specimen contact points or test
specimen.
The choice of power supply depends on the test requirements, i.e. using a.c. will reveal
discontinuities up to approximately l mm below the surface~ using d.c. will reveal
discontinuities typically up to 2 rum to 3 mm below the surface.
20 An ammeter is usually incorporated in the equipment to indicate the amount of current
flowing through the workpiece.
In fixed installations, i.e. bench equipment, the component is flffi1ly clamped between
contact heads. With portable equipment, electrical contact is made by the use of prods
and/or clamps.
30
Prod technique (CFP)
With this technique the current is introduced into the item under test by using electrical
contacts known as prods. Prods induce a circular magnetic field within the specimen
using current values typically in the region of 1000 amps; at this current level arcing
can occur between the electrodes and the test surface causing damage. To prevent this
40 possible damage, the prod contact tips and the test surface must be kept clear of any
contamination and the current must not be switched on until firm contact has been
Because of the risk of arc established, likewise, the current should be switched off before lifting the prods.
strikes, many specifications
do not allow the use of the
prod tec hnique.
Area of inspection

50

60

70
Fig. 4.4 - Current flow using prods.

Precautions when using current flow in respect to prods/clamps shall be taken to

prevent excessive heating, burning or arcing. Certain metals including copper and zinc
(including galvanised prod tips) may, if used as prod material, contaminate and cause
80 metallurgical damage to the component if arcing occurs. For this reason and the fact
that perfect contact is difficult to achieve with prods, ideally they shall be made of steel
or aluminium. Zinc shall not be used and copper or copper-tipped prods shall be used
only in applications where complete assurance can be given that metallurgical damage
will not occur. The cleanliness of both prod contact faces and the component shall be
such to ensure good electrical contact. Prods shall have a minimum dimension of I0
90 mm and shall have as large a contact area as possible. Arcing or excessive heating
shall be regarded as a defect requiring a verdict of acceptability. If further testing is
required on such affected areas, it shall be carried out using a different technique.
Note: Lead contact pads may be used, but only in well ventilated conditions, because
they may generate harmful vapour which may cause headaches and/or dizziness.
100

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:\OTES Since the lines of force radiate from prods, correct positioning is essential to ensure
that all possible defects are located. Ideally the prods should be in a line parallel to,
and on the same axis, as the defects being sought.

10
Prods

f) BS EN ISO 9934-1
quotes two formulas for
prods depending on the 20
required area of inspection,
i.e.: Weld
I= 2.5H x d: or

I= 3Hxd

Where 30
I amps a. c. r.m.s.
d = prod spacing in
mm 's
H = tangential field
strength in kA/m

2) The BS 6072 specifies the

40
minimum amperage for the Flaw
prod technique as 7.5 amps
peak current value per I mm
ofprod spacing, or 5.3 amps Fig. 4.5- Position ofprods should ideally be parallel to defects being sought.
ofa.c. r.m.s.
When using prods the field strength should normally be checked by the use of flux
These apply to flat areas
or slightly curved surfaces. 50 indicators.
i.e. the radius of curvature of
the inspection surface
Advantages of the prod technique include:
exceeds half the prod spacing.
A.c. or d.c. fields.
A.c. energised equipment may be used for demagnetisation operations.
Low voltage output.
60
No poles to attract magnetic particles.
Variable field strength.
Can be used in confmed spaces.
Relatively fast coverage of area under test.
70 Disadvantages include:
Risk of creating arc strikes.
Heavy transformer required.
Classed as a two man operation.
Magnetizing methods Contacts and small test items can overheat.
other than the use ofprods 80
may leave residual fields, Careful positioning and spacing of prods required.
but generally speaking,
these fields are less likely to
Possible to switch on without creating a field.
oppose or destructively May leave residual field which interfere with next prod positions (see side note*).
interfere with the field
introduced by the next Expensive equipment.
magnetizing position.
90

100

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 Ruane & II t.:~IT :\IT4 l\IAG~ETIZI~G :\IETIIODS & APPARATt.:S
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:\OTES
Contact heads (bench equipment technique, alternative name head shot)
BS EN ISO 9934-1 states the Current flow can also be achieved in regularly shaped items, e.g. bar or tube, by
required amperage will be applying contacts to the ends of a test piece and passing a high amperage, low voltage
gtven by: 10 current through it. This sets up a circular field in the ferromagnetic material in a
] -flrp direction at 90 to the current flow, therefore the technique is used for detecting defects
Wh ere parallel to, and up to 45, of the current flow, e.g. longitudinal defects in bar. Copper
amperage r.m.s. gauze is usually placed between the contacts and the test piece to increase the contact
p components area and reduce the possibility of burning.
perimeter in mm 's
H tangential 20 Irregular shaped items may also be tested by contact heads, although, depending on the
field strength in component's shape and dimensions, it may be preferable to use an alternative method.
Wm
BS 6072 stated 7.5 amps peak
per mm ofdiameter or I. 7
Peripheral dimension = n X diameter (equivalent)
amps a. c. r.m.s. per mm of Peripheral dimension
peripheral dimension and 5.3 Therefore, diameter (equivalent) =
a.c. r.m.s. per mm ofdia. 30

Both documents stated if there

was a cross sectional change of Because the current values are dependant only on the test piece perimeter. the kngth of
1.5: I or more. the object will the test piece 1s of no 1mportance, i.e. on a test piece of 25 mrn diameter, the same
be tested sectiott by section. current value would be used whether it was 10 em long or 1 m long, therefore, if two
test pieces of differing diameters were tested using the same current, the magnetic field
40 would be stronger in the smaller diameter test piece

INDUCfiON METHODS
Induction MPI methods do not necessarily require any contact between the
magnetizing apparatus and the test specimen.
50

NB. When using a nonferrous

Threader bar (TB)
threaded bar. the field in a Sometimes known as the central conductor method, although the conductor need not
ferrous cylinder would be always be central.
greater than in the conductor.
The object being examined must be of hollow section and access must be available to
60 both ends, providing these limitations are met, then a conductor - typically made of
BS EN ISO 9934-1 quotes for brass, copper or aluminium - is threaded through the bore, or aperture, and a current
central conductors. the same
values as current flow will be passed through it.
applied, whilst non-central
conductors will be assessed.
This sets up a circular field in the surrounding ferromagnetic material in a direction at
measuring the tangential field 90 to the current flow, therefore the technique is used for detecting defects parallel to,
strength. Separate values will bfo and up to 45, of the current flow, e.g. longitudinal pipe defects.
applied for the inside and
outside surfaces.

BS 6072 stated either to use

the sam e values as current
I I
flow or: R =-or- 80
15 56
Where
R = Radius of inspection
(mm) Fig. 4.6 - Threader bar method.
f = current applied(peak)
15= constant for general
engineering applications 90
56= constamfor The conductor may be located centrally to the specimen, but on larger diameters the
critical inspection conductor is often placed to one side to ensure sufficient flux strength and the test
applications piece rotated to allow for surface inspection. Alternatively, two conductors may be
used on larger diameter test pieces.
NB. W7ten a current is
passed through conductors,
one of which is magnetic 100
the oth er non-magnetic, the
field surrounding them
would be the same.

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'OTf. S The threader bar technique is ideal for the testing of ring like specimens, especially
because numerous samples may be tested at the same time; lengths of pipe may also be
examined by this method. On site work, this technique is not widely encountered, but
could be modified by using a flexible cable instead of rigid conductor.
10
When using a threader bar that is not covered with insulating material, care should be
taken to ensure that components in contact with the threader bar catmot touch any part
of the magnetic equipment at earth potential.
Ara to be inspected

20

30

' ---- .....-/

40

Fig. 4. 7- Threader bar method using non-central conductor

Current values for the rigid
coil technique may be
calculated from BS EN ISO 50 Encircling coils (R.C. = Rigid Coil)
9934-1 using: This technique consists of placing the specimen inside a coil of tubular or solid
construction, through which a low voltage, high amperage current is passed. The
Nl = 0.4Hx K
(UD) magnetic field passing through the centre of the coil - typically three or five turns -
creates longitudinal magnetjzation and is therefore used to detect defects which lie
Where transverse to the components major axis, e.g. good for detecting circumferential
Nl = ampere turns 60 defects in shafts or the bores of tubes.
U D = length to diameter
ratio of the test piece,
min 5:1. max 20:1 ,
ideally between 12
& 15:/
H = tangential field
strength (/cAlm)
10
K - 22,000 a.c. source
(rms) and for FWR
(mean) or I I. 000 for
HWR (mean)
Whereas BS 6072 stated:

I= K
(L/D)x N 80 Fig. 4.8- Encircling coils produce longitudinal magnetism in the specimen which is
Where used to detect transverse flaws. The coil may be flexible or rigid. This may also be
referred to as a 'solenoid'.
I = current required
UD= length to diameter
ratio ofthe test piece, For practical purposes only defects which lie within the confmes of the coil should be
min 5:1, max 20:1, interpreted although the field will extend for 100 to 150 mm beyond either end.
ideally between 12 90
& 15:1 If the specimen being tested has a small diameter in relation to the inside diameter of
N = number ofturns in the coil, it should ideally be positioned close to one side of the coil and rotated to
the coil obtain the best results.
K = 22.000 a.c. source
(rms) and for FWR NB. The strongest magnetic fie ld is on the inside edge of the coiL
(mean) or 11,000 When using any of the current flow or threader bar methods, the field strength is
HWR (mean). 32000
d. c. source and pea/J 00 largely determined by the current (amperes) flowing in the circuit. When using any
value for any form of coil the field strength is determined by the current flowing in the circuit and
waveform. by the number of turns in that coil, thereby obtaining ampere/turns.
Bot" standard$ reference
the object should only
occupy 10% or less of the O Ruue&TPO'Ndii
cross sectional area afthe Issue 7 0.1104106 MT4-7
coil (fill factor).
 Ruane & II UNIT l\IT4 l\IAGNETIZING METHODS & APPARATUS
TPO'Nef/1

'1\0TES The number of ampere/turns can be applied to the specimen length in metres to give
the field strength unit for coils as ampere turns/metre (A Tim) .

10
Flexible cables (FC)
When a single conductor is used, the magnetic field reduces rapidly at increasing
distance from the conductor; this restricts the production of an adequate test area with
a sufficiently constant magnetic field. If the current is made to flow in the same
direction through conductors spaced some distance apart, a relatively constant field is
produced.
20 Flexible cable techniques can be used on a considerable variety of component shapes.
Configurations used are normally obtained with a heavy insulated flexible cable which
is placed through, on, or around the specimen. A current passed through the cable will
then induce a magnetic field into the test piece.
Flaws

30

40

50 Fig. 4.9- Threader cable technique

Defects lying parallel to the cable will be the most readily detected. On complex
shapes the position and method in which the cable is wound may have to be found by
experimentation to ensure an adequate field in all areas.
One method of test utilising flexible cables is the adjacent cable technique. This
60 method of magnetization requires the material being tested to be in close proximity to
a current flowing in one direction.
BS EN LSO 9934-1 quotes d
as half 1he inspection area. The return cable for the electric current must be arranged to be as far removed from
wherefls BS 6072 stated d as the inspection zone as possible and, in all cases, this distance should be greater than
the width of the inspeclion IOd.
area.
70

80

90

1oo Fig. 4.10 - Adjacent cable technique (alternative names include parallel conductors
and the kettle element technique).

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\OTF:S When testing radiused comers on cylindrical components or branch joints, e.g. stub to
header welds, the cable may be wrapped round the surface of the component or the
*BS EN 9934-1 quotes:
branch, and several turns may be bunched up in the form of a closely-wrapped coil. In
this case, the surface inspected shall be within a distance, d, of the winding*.
d=N/147!11 10
Advantages of flexible cable techniques include:
Where
A.c. or d.c. fields.
NI - ampere turns
H = tangential field strength A.c. energised equipment may be used for demagnetisation operations.
Whereas BS 6072 stated Large areas inspected with each set-up.
d = N/130 20 No poles to attract magnetic particles.
Where
Field strength can be altered.
NJ = ampere /!lrns
30 = constant (peak value) Predictable field strengths.
Disadvantages include:
30 Cumbersome long heavy cables required.
Longer setting up times.
Heavy transformers required for large amperages.
Expensive equipment.
40

50

60

70

80

90

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 Ruane & II U:\IT :\ITS THE DETECTING :\IEDIU:\1
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1"1 OT 1: S The detecting media should normally be in accordance with BS EN ISO 9934-2 : 2002
Detection Media. When inks are used for MPI the test may be referred to as a wet
method; when powders are used the test may be referred to as a dty method.
BS EN ISO 9934-2:2002 IO
The basic requirements for magnetic particles are as follows:
for inks states between
1. 5 pm and 40 pm. whereas a. Fine grains to reduce the gravitational effect. However, if the grains are too fme,
powders are generally
~ 40pm.
this could coagulate the particles.
b. Elongated shape for easier polarization. Spherical particles are also needed to
BS 4069 stated a maximum
of 100 pm for inks and
ensure dispersal over the surface.
200 pm for powders. 20 c. High permeability for magnetization in weak flux leakage fields.
d. Low retentivity if particles are to be removed from the test surface after the test.
e. High contrast against the background of the test surface.

DRY POWDERS
30
Dry powders consist of fmely divided ferromagnetic particles available in a variety of
colours, e.g. black, grey, red, orange or yellow, some dry powders may also be
fluorescent.
Dry powders are usually applied to a surface by means of a puffer device
(insuffulator), they should be floated, not blasted, onto the area under test.
40
Dry powders should ideally be used with a.c. or half-wave rectified current (h.w.r.c.)
because of the extra mobility that these current types impart onto the powder.
A maximum of 3/5C Dry powders must be used when MPI is being carried out on hot surfaces*, a situation
(600F). however. at these where inks would obviously not be suitable. Dry powders are also encountered for use
temperatures convection
on rough surfaces and for better indications for slight sub-surface discontinuities.
currents from the test piece
make applicatiOir difficult. 50

INKS
Ferromagnetic particles suspended in a suitable carrier fluid should have the same
basic properties as the dry powders. There are two distinct divisions when dealing
60 with MPI inks, these beingjluorescent inks and non-fluorescent inks. Non-fluorescent
inks are usually black and referred to as black inks.
BS EN ISO 9934-2 : 2002
If water is used as a carrier fluid for the ferrous oxide particles, it should contain
110longer specifies a solid
contetrt range and states tire additives to prevent corrosion of the surface or particles, and improve the wetting
supplier will give this action. Paraffm based products have good wetting action, are odourless, have a
information in g/1. To relative tolerance to oil or grease on the surface and are not corrosive.
check the overall 70
performance there are two A typical method of test for assessing the solid content of magnetic inks:
reference blocks referred to
in Appendix 8 of this 1. Maximum volume of magnetic ink for test should not exceed 5 litres.
standard.
2. Agitate container for not less than 5 minutes.
BS 4069 stated the solid
contents for inks as 3. Pour sample of ink into 100 ml set1lement flask (centrifuge type or Sutherland
1.25-3.5%for non- 80
flask).
fluorescent inks and
0.1-0.3% for fluorescent 4. Allow to settle for 60 minutes.
inks.
5. Read off the solid content to nearest 0.1 ml.
Tire carrier fluid sir all make
the volume up to 100%. The solid content range is very important as too high a concentration will cause
90 excessive background and too low a concentration will cause weak indications to be
missed.

100

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TPO'Nel/1

'\OlFS

Sutherland Centrifuge Tube

Flask or Crow Receiver
10

20

30

Fig. 5.1 - Settlement flasks used to determine the solid content ofMPI inks

An additional test for fluorescent inks after settling is to check the suspension fluid
40
with UV-A light, if a yellow-green fluorescence is observed, the ink should be
discarded and replaced with a fresh solution.

In general it is stated for all inks that:

a. They shall form a uniform suspension when agitated.
50
b. They shall not contain any other ingredients that are likely to cause injury to the
operator either during or after use.
BS EN 9934-2 quotes a c. The inks shall not corrode or otherwise adversely affect the surfaces of the
mtuimum sulphur and work:pieces.
halogen content of d. They may contain small quantities of other ingredients at the manufacturers
200 ppm :1: !Ofor
designated low sulphur discretion providing the solid content remains within the specified proportions.
60
and halogen consumables

IlEALTH AND SAFETY CONSIDERATIONS

The supplier of MPI consumables is obliged to make available to the purchaser, all
relevant health and safety data applicable to the supplied goods. The user also has an
70
obligation to comply with the health and safety requirements. See also the COSHH
Regulations in Unit MTll.

BS EN ISO 9934-2 simply

Specific health and safety considerations are:
states the flash poiIll will be Flammability: Read container labels for flash points.
assessed by a11 open cup
me thod and the flash Asthmatic: Do not use in confined spaces without masks or adequate ventilation.
point reported. 80
Skin hazard: Use protective clothing.
BS 4069 stated for oil based
inks to be assessed in a
closed cup test and should
not be less than 65C

90

100

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' OT ES All areas under test using non-fluorescent i.nks should be adequately illuminated using
artificial light if necessary. For fluorescent inks, a U V-A light with subdued
background lighting should be used, the darker the better, to increase the overall
The darker the ambient
contrast ratio.
lighting conditions, the 10
higher the operator eye
strain becomes. warranting
more regular breaks to
reduce operator fatigue. NON-FLUORESCENT INKS AND POWDERS
The area under inspection should be evenly illuminated. Most commonly used
standards quote a minimum illumination level of 500 lux in daylight or under artificial
20 light.
BS EN ISO 9934-1 refers to
BS EN IS O 3059 f or UV-A
conditions which quotes a
minimum UV-A irradiance
of 1000 pW/cm1 and a
FLUORESCENT INKS AND POWDE.RS
maximum 20 lux ambient The area under inspection should be irradiated with UV-A light. The levels of UV-A
bac kground lighting.
Whereas BS 6072 stated 30
irradiation are quoted in the relevant standards (see side note), together with the
a minimum UV-A maximum permitted background illumination.
irmdiance of800 11 Wlcm:
and a maximum 10 lux
Fluorescence degrades with exposure to ordinary light over a period of several hours,
am bient backgro1md moreover, it can be arrested entirely at high temperatures. As the intensity of the
lighting. ultraviolet light is increased, the amount of fluorescence increases.
40
UV-A light
Ultraviolet light is generated by a 100/125W hand held high pressure mercury vapour
lamp (NB. 400W flood lights are also available). The mercury is vaporised inside a
77ze temperature alters the quartz capsule by a small low current arc from an auxiliary electrode. After about 5
pressure inside the quartz minutes there is sufficient mercury vapour in the capsule to initiate an arc between the
crystal capsule which in main electrodes. The lamp should not be used for approximately 15 minutes to allow
111m alters the spectnml of
50
sufficient time for it to attain full working intensity.
emiued wavelengths.

Only hig h pressure mercury

vapour lamps are used for
irradiating thefluorescent
...----
Medium screw base

dyes. Low pressure

discharge lamps are only 60
used f or ambient lighting
conditions.

BS EN ISO 3059: 2001

Auxilliary starting electrode
quotes tz minimum warm up
period of 10 minutes.

70 Ballast resister

80
U.V. filter
BS EN 9934-3 quotes a
UV-A intensity of Fig. 6. I - Ultraviolet (UV-A) lamp
IOOOpW!cm' at 400mm

Assessment of UV-A intensity

The efficiency of the mercury vapour lamp can deteriorate quickly without any
90
obvious effect, therefore the lamp's intensity should be checked regularly with an
The old British S tandard ultraviolet light monitor, such as that specified in BS EN ISO 3059 : 2001 Non-
(or c hecking UV-A lamps Destructive Testing - Penetrant Testing and Magnetic Particle Testing - Viewing
was BS 4489 : Method
(or Assessing UV-A Light
Conditions.
used inNDT BS EN ISO 3059: 2001 gives information and recommendations for the testing ofUV -
100 A light sources, in particular the assessment of emission from new lamps and the
regular testing of any lamps in service which may produce a drop in output after
approximately three months use. The test is carried out using a radiometer.

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:\OIES

10

20

30
Fig. 6.2 - Analogue style radiometer

40

50

60

Fig. 6.3 -Digital style combined radiometer and photometer

70
SAFETY
UV-A lights operate with wavelengths between 315-400 nm (3 150-4000 A), shorter
wavelengths than this can cause injuries to the eyes. To prevent injury, a filter should
be used which cuts out wavelengths below 315 nm.
80 Looking into a UV -A light will cause temporary clouding of vision due to the fluid in
the eyeball fluorescing, it will normalise with no permanent effects after a few seconds,
although it is important to note that prolonged exposure may cause cataracts.

90

100

Cl Ruant & T P O'Ndll

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ELECTROMAGNETIC SPECTRUM

10

~~~-----U~ltr~a~v~i~ol~e~t~li~g~h~t----~
~ l
I
Visible emissions
I

UV-C UV-B <UV-A ::

....u 0 Q ~
u
00
s::
.,.__________ I
0
00 u II) ..9
~ :~: ~
:0 .a Q)
"'i)
0"'
"0

>
II)

20
I
I
I
I
I
I
.s It) 0 >o 0::
I
I I
100 200 300:I I
I 400 500 I
I 600 700
I I
I I
I I
I I
280 315 I I

-( -(
30 365nm 520-580 run
The 'working' wavelength The dyes fluoresce, i.e. give
used to irradiate the off visible emissions within
fluorescent dyes this bandwidth between the
colours blue/green and
green/yellow. This is
deliberately chosen since the
40
human eye is most sensitive to
the colour green and will
therefore enable a greater
speed of inspection.

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:\O 'It:S Demagnetization of a specimen may be required before testing, between successive
shots/magnetizing positions, and/or after testing in order to remove any residual
magnetism in the specimen.
10 Demagnetization may be carried out for the following reasons:

1. To remove any residual magnetism which may remain from previous MPI
procedures or other sources, which may interfere with the subsequent test.
2. To remove any residual magnetism between successive MPI shots in the test
procedure.
20
3. To remove any residual fields after MPI has been carried out so as not to interfere
with other work processes, e.g. a residual magnetic field may attract cutting swarf
during machining operations and may also interfere with subsequent welding
operations causing arc-blow.

0+
30

40

50

Fig. 7. 1 Hysteresis loop showing demagnetization

60
There are several methods of demagnetization:

a. Aperture coil with a.c..

This is a coil of several hundred turns which is connected to the mains. The
object to be demagnetized is placed inside the coil and slowly withdrawn to a
70 distance of at least 1.5 metres away from the coil, or the object is left stationary in
the coil and the current gradually turned down to zero.

b. Aperture coil with reversing d.c..

This method is similar to the a.c. coil but the demagnetizing field penetrates
further in the test piece. The current direction is reversed periodically, but at
80 decreasing amplitude until the residual magnetism is removed.

c. A.c. electromagnetic yokes. (wiper brush)

These can be used to demagnetize large areas in situ. The yoke is stroked over
the surface, lifting is well clear (450 mm to BS 6072) between strokes.

d. A.c. current flow

90
When using a current flow crack detector, demagnetization can be carried out by
using a.c. current and slowly reducing the current flowing to zero. A variation on
this method is the peak and drop technique where the current is initially
introduced at a higher value than the magnetizing current then reduced to zero,
the peak current is then re-introduced at successively decreased values whilst
returning to zero current after each peak current.
100

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e. Flexible cable (induction system).

If a portable induction type crack detector is available, demagnetization can be
carried out by wrapping 2 or 3 turns of the cable around the object to be
demagnetized and gradually reducing the a.c. current to zero. If magnetization is
10 carried out using the induction coil, the object under test is automatically
demagnetized if the current is reduced to zero before the unit is switched off.

f. Heat treatment.
It is not necessary to demagnetize if a heat treatment process is to follow magnetic
particle inspection and the specimen is to be heated beyond its curie point, which
20 is approximately two thirds of the material's melting point, e.g. 358C for nickel,
These temperatures are 870C for iron and 1127C for cobalt. Above this level ferromagnetic materials
quoted in BS 3683 : Part 2. lose their magnetism, i.e. the magnetic domains become randomly orientated.
however. the curie
temperature ofiron is more When a material is to be demagnetized, by methods other than heat treatment, the
often quoted around 750C. initial demagnetizing fie ld strength must be stronger than the residual field.
30 Demagnetisation may be easy or hard, depending on the test piece material, i.e. is the
material soft or hard? 1
Circular magnetism is generally considered to be harder to demagnetise than
longitudinal magnetism because theore!Jcally the field ts contamed wtthm the test ptcce
with no poles and 11 ts therefore difficult to measure the.. field strength
40 To fully demagnetise a test piece it should be carried out in an east-west direction so
that the earth's magnetic field will not interfere. By laying a test piece north-south, the
earth's magnetic field will weakly magnetise it.
The level to which a specimen must be demagnetized may be laid down in an MPI test
procedure or specification.
50 The amount of residual magnetism remaining may be checked with a calibrated field
strength meter or existence may be confirmed with other types of field indicator.

60

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Ruane & II UNIT l\IT8 1\IAGNF:TIC FIELD INDICATORS
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:\OTES Magnetic field indicators, e.g . .flux indicators and field strength meters are used to
assess the presence, intensity and/or direction of a magnetic flux either before, during,
or after testing. Specific uses of these instruments are as follows:
10 To ensure MPI test machines are functioning correctly.
To ensure that the specified field strength and field direction are apparent.
To check for the presence of residual magnetism before testing.
To check for the presence of residual magnetism after testing.
20
Magnetic field strength meters and portable flux indicators should not be used in
conjunction with permanent magnets or with d.c. electromagnets for determining
adequate flux density. A flux indicator may be used with these magnets but only to
verify the suitability or correct application of an ink or powder.
Circular fields may be contained completely within a specimen, if this is the case, the
30 field will not be detected.
BS 6072 quoted two
techniques for the presence Many terminologies are encountered when referring to types of magnetic field
of a residual field which
were:
indicators, which can be confusing. There are also alternative methods other than
those listed below to check for residual fields.
a. using a compass
b. paperclip on a thread
40
PORTABLE MAGNETIC FIELD STRENGTH METERS
(MAGNETOMETERS)
To measure residual magnetism, calibrated magnetic field strength indicators of the
type which contains a soft iron vane are commonly used. The vane aligns itself with
so the magnetic field, the strength and direction of the field is measured by the meter
calibrated in gauss or tesla's; similar non-calibrated instruments also exist. Neither of
these instruments should be brought into close contact with any strong magnetic fields
as this may cause damage to the instrument.

60

70

80
Fig. 8.1 - Field strength meter

90
SIDM TYPE/FOIL STRIPS (TRADE NAME CASTROL STRIPS/ELY
STRIPS)
These are small brass or silver finish strips containing artificial defects (3 slots) in Mu
metal; Mu metal is a highly permeable material containing nickel, manganese and iron.
The brass finish strips are commonly used in general engineering applications and
indicate low field strengths. The silver finish strips will show higher field strengths
100 and are used in aerospace industries or areas that require a more critical examination.

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 Ruane& II U~IT i\IT8 l\IAGi'iETIC FIELD li'iDICATORS
T P O'Neill

\ OT [S In either case, if the field is strong enough, three linear indications will show on the
strip; they should be rotated on the specimen surface to define field direction.

\~-----------_-_-_-_-_-------------
_-_-_-_-_-_-_-_-_-_-_-_ mD
10

-_-_-_-_-_-_
'--------------------------------------------------~
Fig. 8.2 - Castro/ strip
20
With reference to the brass finish strip (type 1), if no indications are apparent the field
is too weak for inspection and it is below 3 amps a.c. r.m.s./mm (240 Oe). Three
indications show that the field strength is greater than 5 amps a.c. r.m.s./mm (400 Oe).
With reference to the silver finish strip (type 2), if no indications are apparent the field
is below 5 amps a.c. r.m.s./mm (400 Oe). Three indications show that the field
30 strength is greater than 15 amps a.c. r.m.s./mm (1200 Oe) and the field is suitable for
critical inspection.
Note: The above figures are based on a mild steel bar.

40 THE ASME FIELD INDICATOR

This consists of eight sections of mild steel brazed together, the separating lines
between the sections forming artificial defects. One side also has a chromium coating
applied, this has a greater sensitivity than the opposite side which shows surface
breaking defects.
so When the indicator is placed on a magnetized component the magnetic field passes
through the indicator. The separating Jines between the sections become visible when
the detecting media is applied. To determine the direction of the magnetic field the
indicator should be rotated until one of the lines is perfectly visible, at this point the
direction of the field is at 909 to the line.

60
THE BERTHOLD PENETRAMETER
An a/temative collective This field indicator contains two artificial defects at 90 to one another. There is a
tern1 for penetrometers, sensitivity adjustment consisting of a cover plate which can be turned to one of four
e.g. ASME. Berthold, setting which vary the distance of the cover plate and detecting media from the
Castro/ Type 3 is a pie
gauge '. 70
artificial defects; the greater the gap the higher the field strength necessary to render
the lines visible. They are used in a manner similar to the ASME indicator.

80

90

Fig. 8.4- Berthold penetrameter

100

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'011-'S HALL EFFECT METERS

These instruments are usually used in laboratory type environments to measure
tangential. normal, or axial fields depending on the probe design. Hall effect meters
10 use, as their name suggests, the Hall effect principle.
An electric current is passed through a small semi-conducting crystal contained within
a probe. A voltage is generated across the crystal, when the probe is placed in a
magnetic field, the magnitude of this voltage is directly proportional to the magnetic
flux density within the probe. The relative permeability of the semi-conducting crystal
is very close to one, so the voltage generated is proportional to the magnetic field
20
strength at the point where the probe is placed. The voltage generated by the probe is
measured by an electronic circuit and indicated on a meter marked in units of field
strength.
The Hall effect meter is calibrated with a series of standard magnets which provide
known values of field strength within the working range of the instrument.
30 Manufacturers supply a zero-field chamber which is required to set the zero. If the
peak value of a time varying field is required, the meter reading is multiplied by a
conversion factor, the value of which depends upon the shape of the waveform and
upon the measuring principle employed by the instrument.

40 PERFORMANCE CHECKS
Performance checks are used to ensure an MPI test system is functioning correctly, i.e.
a magnetic field is capable of being produced and reproduced so that test results can be
maintained at a consistent level. Typical reference blocks are given below.

so Current flow (headshots)

When current flow techniques are used on bench units, the following test should be
carried out for each wave form available for use:
a. Ensure the test piece is thoroughly demagnetized and pre-cleaned satisfactorily.
b. Position the test piece (see diagram below) between the head and tailstock of the
60 bench equipment.
c. Slowly introduce a current and apply ink until the first hole (closest to the
external surface ) is visible.
d. Note the applied amperage and continue to apply the current progressively until
the second and third holes are noted.

70
1:==== 3 holes of I mm drilled through
ring at 1.5, 2.0 & 2.5 nun helow
surface (offset at25 degrees to
each other)

80

90

100
Fig. 8.5- Test piece for current flow technique

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Ruane & II L"NIT :\ITS l\1:\G~ETIC FIELD INDICATORS
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'OltS

Magnetic flow
10 If magnetic flow is being used, a similar procedure to the above would still apply,
except that the dial readings/switch settings would be taken instead of amperage values
and the following test piece would be used.

J.Smm Diameter

20

30

40 Fig. 8. 6- Test piece for magnetic flow and rigid coil techniques

Rigid coil
If a rigid coil is being used, the procedure in the section above for Current flow
(headshots) would still apply, except that the test piece used would be as shown in
previous section for Magnetic Flow.
50

ALTERNATIVE TEST BLOCK(S)

As to BS EN ISO 9934 : Part 2 for type testing, batch testing and in-service testing of
fluorescent inks, reference block no. I should be used.
60

b
70 ' - - -- ..J/ 10.5:1:0.05

T a - Grinding cracks
b - Stress corrosion cracks

\ I

80
--1 9.7 0.05 1-- 50 0.05
I
All dimensions in mm

90

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\ (J'I ES
INTERPRETATION DEFINITIONS
Discontinuity - an interruption in the normal physical structure or configuration of a
part.
10
Non-relevant - indications from something on the test piece which is expected,
i.e. brazed joints, internal splines or drj))ed holes.
Indication - particles accumulated and held at a site by a leakage field.
Adequate reporting is essential for the transmission of relevant and correct information
20 after the test. Any test report should include the information required by the relevant
specification for the work being performed.

A typical report would require the following:

a. name of the company;
b. work location;
30 c. description and identity of the part tested;
d. stage of test (e.g. before or after heat treatment, before or after fmal machining);
e. reference to the written test procedure and the technique sheets used;
f. description of equipment used;
g. magnetising technique, including (as appropriate) indicated current values,
tangential field strengths, waveform, contact or pole spacing, coil dimensions etc.;
40 h. detecting media used and contrast paint if used;
i. surface preparation;
j. viewing conditions;
k. method of recording or marking of indications;
1. date of test;
m. name, qualification and signature of the person performing the test.
50
The test report shall then contain the test results, including a detailed description of the
indications and a statement as to whether they meet the acceptance criteria.

A common method of recording indications is to reproduce indications on a scaled

diagram. Indications should be drawn with references to a datum on the test piece.
The diagram(s) should not be overloaded with too much information; use two
60
diagrams if necessary. A separate diagram showing m agnetizing techniques should
ideally be included where it is not obvious which technique has been applied.

PRESERVATION OF INDICATIONS
70 Prior to the recording of indications, it is essential to ensure that the test conditions,
and in particular the magnetizing levels, are as near as possible to the level
recommended for the technique.
If dry powder., is used, no preparation is necessary. If any oll based carrier Outd LS
used, the surface should be drained and adequately dried. Another possibility is to
80 retest the workpiece using a magnetic ink made with a volatile carrier fluid.
It is essential that a common datum be established on both the workpiece and the
record and that care be taken not to disturb the indications.
Other methods of recording indications are:

1. Photographs
90
When a photographic record is made, the resulting photograph of the tested surface
should, if possible, be actual size. If the surface of the workpiece is highly polished,
care should be taken to avoid highlights. The use of a matt-contrast medium applied
prior to testing may be desirable.

2. Clear sticky tape

100
This is used to peel the dried magnetic particle indication from the test piece.

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 Ruane& II Ul\'IT :\IT9 REPORTING
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:\OTF.S a. Cover the indications with a transparent adhesive fllm. Carefully peel off the film
and the adhering indications and reapply to either paper or card of contrasting
colour.
b. Degrease the test surface, cover with a white matt adhesive film and retest. After
10 drying, if necessary, cover the indications with a clear film in the manner
described in (a) and transfer together the pair of films to the record card.

3. Proprietary coatings sprayed on wet; when dry, the resultant film is then peeled
away with the indication.
20 a. Spray the tested area with a quick-drying, strippable coating. Strip off this
coating and view the face previously in contact with the workpiece, to which the
indications will be transferred.
b. Heat the workpiece to an approved temperature and, without delay, slowly
immerse in a powdered plastic material and slowly withdraw. Allow it to drain
BS EN 1290 : 1998 also and cure it in accordance with the manufacturers instructions. Strip off the
lists: coating complete with indications from the workpiece and view the face
30
a. Transparent varnish previously in contact with it.
for freezing ' c. Degrease the test surface and coat with a proprietary, strippable, magnetic oxide
indications on the
test surface. paint. Magnetise the part to saturation and peel off the coating. If it is dipped in
b. Video recording. agitated magnetic ink, it will reveal the flaw indications on the oxide film.
c. Epoxy or chemical d. Degrease the test area and coat with a proprietary self curing magnetic silicone-
magnetic particle rubber compound. Magnetise to saturation and allow the compound to cure. The
mixwres. 40
oxide in the compound will migrate to the position of any flaw and, when
d. Magnetic tapes.
e. Electronic scanning. removed from the workpiece, the rubber previously in contact with the surface
will show the flaw.
BS EN ISO 9934-1 : 2001
does not list preservation 4. Magnetic sachets with light sensitive paper backings.
techniques but it states 5. Magneto-graph.
indications should be 50
recorded as linear or
rounded, i.e. Limitations of preservation methods
Lin ear - the length is more Methods I and 2 above are generally restricted to surfaces of simple geometric form
than three times the width. because of the difficulties involved in removing the films. Method 3b does not
Rounded - the length is generally produce satisfactory results from fluorescent magnetic inks as compared with
equal to or less than three black magnetic inks.
times the width. 60

70

80

90

100

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 Ruane & II VNIT l\'ITIO CLRRENT TYPES
TPO'Nei/1

:\OTl:S Magnetic particle inspection using electrical apparatus can use several types of current,
each form has advantages and disadvantages.
The following waveforms/
power supplies are shown 10
as single phase power ALTERNATING CURRENT
supplies. however. MPJ
equipme/11 will often use For all practical purposes alternating current (a.c.) is used to detect surface defects.
three phase power supplies A. c. does not penetrate deeply into the metal but produces a high density tield near the
as: surface of a ferromagnetic conductor, this characteristic is called the skin effect and
i. larger currents are will emphasise surface breaking discontinuities, e.g. fatigue or stress induced cracks.
available. 20 The skin effect is caused by the concentration of eddy currents near the surface of the
ii. swinging fields are also specimen; eddy currents are only produced by an alternating current.
now possible. i.e. the
bench equipment is
automaLically changing
from CF to MF and vice - Peak
versa, allowing the
operawr 10 view in all
30
directions in one
operation.
NB. Also referred to as
sequential field of multi-
directional testing.
iii. longer duty cycles on the
equipmel!l. 40
NB. BS EN ISO 9934 :
Part 3 now quotes current
generators to have a
minimum duty cycle of
~10%. -1 - - - - - - - Peak

50
Fig. 10.1 Alternating current (single phase)

If surface breaking defects are the prime consideration for detection, then an additional
advantage of a.c. is that less relevant indications from sub-surface discontinuities are
not created by the low penetration capabilities of this type of current, which may
otherwise distract the inspector.
60
Other advantages of a.c. include:
Current at required values can normally be obtained directly from the mains
supply, or via simple transformers.
A.c. machines are relatively inexpensive, are easy to maintain and have basic
70 operating characteristics.
Due to the current form fluctuation (negative to positive), magnetic particles will
vibrate and readily align themselves to flux leakages; this enhances the definition
of defect indications.
If after magnetization the current is reduced to zero via a rheostat or step down
80 device the component is automatically demagnetized.
Disadvantages:
The main disadvantage of a.c. is that it will only detect surface defects with any
degree of reliability.

90

DIRECT CURRENT
A major advantage of d.c. for magnetization is its deeper penetration into the metal
thus enabling sub-surface discontinuities to be revealed. D.c. also leaves residual
magnetism which will hold an indication and allow more time for evaluation of the
I 00 indication, however residual magnetism is not always an advantage and may present
problems if complete demagnetization of the component is required.

0 R01ne & T F O'Neill

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 Ruane& II UNIT !\ITt 0 CURRENT TYPES
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:\OTES D.c. current may be obtained in various forms, either from batteries or rectified a.c.,
each having their own advantages and disadvantages.
The technique known as
d .c. surge employs a d. c. 10 Direct current from battery packs
current which initially
starts with a very high value
and rapidly reduces to a
lower value for the majority +I - - - - - - - - - - ----peak
of the shot duration. 17ze
advamage of this is:
L less chance of damaging
20
the object from a
continuous high current.
ii.lmproved particle 0 1 - - - - -- - - - -- - - - - - - -.,...Time
movement.
iii.Jdea/for detection of
deep lying discolllinuities.
30
~ ----- - ------ --~

Fig. I 0.2 Direct current from battery

40 Advantages include:
Does not require mains electrical supply.
Sub-surface defects may be detected.

Disadvantages include:
50
Weight of batteries.
Limited battery life (high current draw).
Continuous current flow does not produce particle vibration and will not therefore
enhance defect detection. Because of this, continuous d. c. should not be used with
60 dry powders which require a pulsating magnetic field to provide mobility to the
powder when it lands on the test surface.

Half-wave rectified current

H.w.r.c. is achieved by removing all the negative current values from a.c. allowing the
positive half cycles to remain, this current may be considered to be a form of d.c. with
70 all the associated characteristics of this current form with the added advantage of a
pulsating wave.

80

90

-1 - - - - - - - - - - - - - - - Peak

100 Fig. 10.3 Half-wave rectified current (single phase)

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\OTES Since h. w.r.c. will leave a component partially magnetized it is usually packaged as an
a. c./h. w.r.c. unit so that the a. c. is available for demagnetization.
Advantages include:
10
Will detect sub-surface defects.
Will detect fme surface breaking defects.
Simple, effective and inexpensive current form to achieve.
Due to pulsating current the magnetic particles will vibrate and provide greater
attraction to flux leakages.
20

Disadvantages:
May leave the part partially magnetized.

Full-wave rectified current

30
F.w.r.c. provides the most efficient conversion of a. c. power to d.c.. With this current
form the negative half cycle of an a.c. waveform is removed from below the zero line
and reversed to make all values positive (or vice versa).

40

50

1 ----~- - ---- -- --

60
Fig. 10.4 Full-wave rectified current (single phase)
Advantages include:
Detection of sub-surface defects.
Simple and efficient means of providing direct current.
70
Disadvantages include:
More expensive than h.w.r.c..
Particle vibration and mobility reduced.
Higher current requirements than a.c. or h.w.r.c..
80
Can produce demagnetization problems.

Three phase full wave rectified current

+

90 - Mean d.c. volts

,
,, / '
., 1
,, \
,, 1 ,, '
,, I '
,, I '
,, I

, , ,. , ., ,, ,, ,, 1\

c:
~ ~--~---
~ --- ~--~--~--~------~--L----Time
::>
u 1 cycle

100
Fig. I 0. 5 Three phase full wave rectified current

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 Ruane & II UNIT MTll COSIIII REGULATIO~S
TPO'Nelll

,, OTF:S
SCOPE
The Control of Substances Hazardous to Health Regulations, referred to as
10 The COSHH Regulations, defme a substance hazardous to health as:
a. a substance listed in part lA of the approved list as dangerous for supply, see
Hazard Information & Packaging for Supply Regulations 1994 (CHIP2) - nature
of risk classified as very toxic, toxic, harmful, corrosive or irritant
b. one which has an MEL in Schedule 1 of COSHH or if the H & S Commission has
20 approved an OES.
c. a micro-organism which creates a hazard to health.
d. dust in air (when substantial).
e. a substance comparable with the above.
The COSHH regulations are not applicable to the control of lead, radioactivity,
30 explosive or flammable properties of materials, high or low temperatures, high
pressures, medical treatment or below ground work (mining).

RESPONSIBILITIES
40 The exposure of an employee to substances hazardous to health is under the control of
the employer. A training organisation is responsible for exposure by trainees.
Employers must prevent exposure to substances hazardous to health, or control
exposure when total prevention is not reasonably practicable. Personal protective
equipment, e.g. masks, are a second choice for controL
so Employees have a duty to report any problems in exposure control procedures or any
defects found in protective equipment.
Employers must keep records of examinations/monitoring tests carried out. These are
kept for 5 years; 30 years for identifiable employees.

60
OCCUPATIONAL EXPOSURE LIMITS (EH40- JANUARY 2002)
The Guidance Note EH40, entitled Occupational Exposure Limits, is a document
published by the Health and Safety Executive which gives occupational exposure
limits for substances hazardous to health.

70
t'A solvent, which is a substance hazardous to health, has its own occupational exposure
limit as given in EH40. -t
The toxicity value of a solvent is expressed in parts per million (ppm), e.g. the short
term occupational exposure limit for xylene is 100 pp.m, this means to say that if the air
T71e occupational exposure contained xylene exceeding 100 ppm, the air would be considered to be a significant
limit for xylene is an hazard to health.
occupational e.xposure 80
standard (OES). therefore There are two types of occupational exposure limit:
the short term OEL is
I 00 ppm over a 15 minute L Maximum exposure limit (MEL): "is the maximum concentration of an airborne
reference period. 17ze long
term OEL is 50 ppm over
substance, averaged over a reference period, to which employees may be exposed
an 8 hour time weighted by inhalation under any circumstances and is specified, together with the
average reference period. appropriate reference period, in Schedule 1 ofCOSHH".
90
2. Occupational exposure standard (OES): "is the concentration of an airborne
substance, averaged over a reference period, at which, according to current
knowledge, there is no evidence that it is likely to be injurious to employees if
they are exposed to inhalation, day after day to that concentration, and which is
specified in a list approved by HSE".
100

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Ruane & II U:\IT 1\ITl I COSIIII REGULATIONS

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:\OTJ:S When a MEL is specified, exposures must be kept as low as is reasonably practicable,
but always below the specified value.
As OES should not be exceeded, but, an exposure over the limit is acceptable,
10 providing the reason for exceeding the OES has been identified and measures are taken
to reduce the exposure below the OES as soon as is reasonably practicable.

20

30

40

50

60

70

80

90

100

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Ruane& II UNIT ;\IT12 LIST OF APPLICABLE STANDARDS
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\ o 1 E S BS EN 1290 : 1998 Non-Destructive Examination of Welds

Magnetic Particle Examination of Welds

10 BS EN 1291 : 1998 Non-Destructive Examination of Welds

Magnetic Particle Testing of Welds - Acceptance
Levels

BS EN 1330-1 : 1998 Non-Destructive Testing - Terminology

Part 1: List of General Terms
20
BS EN 1330-2: 1998 Non-Destructive Testing- Terminology
Part 2: Terms common to Non-Destructive Testing
Methods

BS EN ISO 12707 Non-Destructive Testing- Terminology

30
Terms used in Magnetic Particle Testing

CP 3012 Code of Practice for Cleaning and Preparation of Metal

Surfaces [SUPERSEDED]

40 BS EN ISO 3059 : 2001 Non-Destructive Testing

Penetrant Testing and Magnetic Particle Testing
Viewing Conditions

BS 3683 : Part 2 : 1985 British Standard Glossary of Terms used in Non-

Destructive Testing
50 Part 2: Magnetic Particle Flaw Detection

BS 4069 : 1982 British Standard for Magnetic Flaw Detection Inks and
Powders [SUPERSEDED]

BS 4489 : 1984 British Standard method for Measurement of UV -A

60 Radiation (Black Light) used in Non-Destructive
Testing [SUPERSEDED]

BS 5044: 1973 Specification for Contrast and Paints used in Magnetic

Particle Flaw Detection [SUPERSEDED}

70 BS 6072 : 1981 Method for Magnetic Particle Flaw Detection

[SUPERSEDED}

PD 6513 : 1985 Magnetic Particle Flaw Detection

A Guide to the Principles and Practice of applying
Magnetic Particle Flaw Detection in accordance with
80
BS 6072

BS 7773 : 1995 Code of Practice for Cleaning and Preparation of Metal

Surfaces

BS EN 12062: 1998 Non-Destructive Examination of Welds

90
General rules for Metallic Materials

BS EN ISO 9934-1 : 2001 Non-Destructive Testing- Magnetic Particle Testing

Part 1 : General Principles

100

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Ruane& II UNIT l\IT12 LIST OF APPLICABLE STANDARDS

TPO'Nei/1

BS EN ISO 9934-2: 2001 Non-Destructive Testing - Magnetic Particle Testing

Part 2 : Characterisation of Products

10 BS EN ISO 9934-3 : 2001 Non-Destructive Testing - Magnetic Particle Testing

Part 3 : Equipment

20

30

40

50

60

70

80

90

100

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