Self Study Magnetic Particle Inspection

Magnetic Particle Test : Overview
o Magnetic particle testing (MT) is a nondestructive testing (NDT)
method for detecting discontinuities that are primarily linear
and located at or near the surface of ferromagnetic
components and structures.
o MT is governed by the laws of magnetism and is therefore
restricted to the inspection of materials that can support
magnetic flux lines.
o MPI method can be used for detection of subsurface
discontinuities unlike PT which is confined to surface
discontinuities open to the atmosphere.
o Surface preparation is not very rigorous as in the case of Liquid
Penetrant Testing (PT).
o The method can detect all discontinuities at the surface and
under certain conditions those which lie completely under the
surface.
Compliance to ASME Section V Article 7 and ASTM E-709-95

Phenomenon Discovered Leading
to Inspection Principles
In the late 1800s it was observed that a
compass needle deflected when it passed over
a crack in a magnetized cannon barrel.
In the 1920s it was discovered that iron
filings on parts held in a magnetic machining
chuck produced patterns showing the
magnetic lines of flux. Closer investigation
revealed patterns that corresponded to
discontinuities within the parts.

PRINCIPLE : MPT
 When the workpiece to be inspected is magnetized, magnetic
flux is induced.
 If there is a flaw on the surface, magnetic flux leaks into the air
at the position of the flaw.
 Then magnetic particles (dyed or fluorescent encapsulated) are
applied to the surface.
 These magnetic particles will migrate to the flaw where the
magnetic flux leaks and forms a flaw indication that is several
tens of times of actual flaw width.
 The inspector visually identifies the flaw.

Applications
o The method is used to inspect a variety of product forms
including castings, forgings, and weldments.
o Industries: the structural steel, automotive, petrochemical,
power generation, and aerospace industries.
o Underwater inspection : offshore structures and underwater
pipelines.
Crane hook with service induced stress
Underwater inspection

Advantages :
o It is quick and relatively uncomplicated
o It gives immediate indications of defects
o It shows surface and near surface defects, mainly required for heavy stresses
o The method can be adapted for site or workshop use
o It is inexpensive compared to radiography
o Large or small objects can be examined
o Elaborate pre-cleaning is not necessary
Disadvantages
o It is restricted to ferromagnetic materials - usually iron and steel, and cannot be
used on austenitic stainless steel
o No indication of defects depth
o Only suitable for linear defects
o It is sometimes unclear whether the magnetic field is sufficiently strong to give
good indications
o If a thick paint coating is present, difficult to perform test
o Spurious or non-relevant indications, are probable & interpretation is skilled task
o Some of the paints and particle suspension fluids can give a fume or fire problem,
particularly in a confined space

Limitations of Magnetic Particle Inspection
• Cannot inspect non-ferrous materials such as
aluminum, magnesium or most stainless steels.
• Inspection of large parts may require use of equipment
with special power requirements.
• Some parts may require removal of coating or plating
to achieve desired inspection sensitivity.
• Limited subsurface discontinuity detection capabilities.
Maximum depth sensitivity is approximately 0.6” (under
ideal conditions).
• Post cleaning, and post demagnetization is often
necessary.
• Alignment between magnetic flux and defect is
important

Theory of MPT
o Test specimen create magnetic field in and around the magnet. A pole where a
Magnetic line of force exits from north pole
o Magnetic line of force enters from south pole.
o The magnetic field spreads out when it encounters the small air gap created by
the crack because the air cannot support as much magnetic field per unit volume
as the magnet can.
o When the field spreads out, it appears to leak
out of the material and, thus is called a flux leakage field.
o If iron particles are sprinkled on a cracked magnet, the particles will be attracted
to and cluster not only at the poles at the ends of the magnet, but also at the poles
at the edges of the crack.
o This cluster of particles is much easier to see than the actual crack and this is the
basis for magnetic particle inspection.

Magnetic lines of
force around a bar
magnet
Similar poles
repelling
Opposite poles
attracting
 Magnetism is the ability of matter to attract other matter
to itself.
 Objects that posses the property of magnetism are said to be
magnetic or magnetized and magnetic lines of force can be
found in and around the objects.
 Magnetic poles always occur in pairs, hence named as dipole
 Bar magnet is a dipole with a north pole at one end and
south pole at the other
 A magnetic field is produced whenever an electrical charge is
in motion & strength of this field is called magnetic field
Theory of MPT

Materials can be classified as:
Diamagnetic materials which have a weak, negative susceptibility to magnetic fields.
Diamagnetic materials are slightly repelled by a magnetic field and the material does not
retain the magnetic properties when the external field is removed.
Paramagnetic materials which have a small, positive susceptibility to magnetic fields.
These materials are slightly attracted by a magnetic field and the material does not retain
the magnetic properties when the external field is removed.
Ferromagnetic materials have a large, positive susceptibility to an external
magnetic field.
They exhibit a strong attraction to magnetic fields and are able to retain their
magnetic properties after the external field has been removed.
Ferromagnetic materials have some unpaired electrons so their atoms have a net
magnetic moment.
When a magnetizing force is applied, the domains become aligned to produce a
strong magnetic field within the part. Iron, nickel, and cobalt are examples of
ferromagnetic materials.
Components made of these materials are commonly inspected using the
magnetic particle method.

Magnetic Lines of Force
Magnetic lines of force have a number of important properties, which include:
o They seek the path of least resistance between opposite magnetic poles. In a single
bar magnet as shown to the right, they attempt to form closed loops from pole to
pole.
o They never cross one another.
o They all have the same strength.
o Their density decreases (they spread out) when they move from an area of higher
permeability to an area of lower permeability.
o Their density decreases with increasing distance from the poles.
o They are considered to have direction as if flowing, though no actual movement
occurs.
o They flow from the south pole to the north pole within a material and north pole to
south pole in air.
Quantity
SI Units
(Sommerfeld)
SI Units
(Kennelly)
CGS Units
(Gaussian)
Field Strength H A/m A/m oersteds
Flux Density
(Magnetic Induction)
B tesla tesla gauss
Flux f weber weber maxwell
Magnetization M A/m - erg/Oe-cm 3

Magnetic Field Distribution
Longitudinal Fields
When a long component is magnetized using a solenoid having a
shorter length, only the material within the solenoid and about
the same length on each side of the solenoid will be strongly
magnetized. This occurs because the magnetizing force
diminishes with increasing distance from the solenoid. Therefore,
a long component must be magnetized and inspected at several
locations along its length for complete inspection coverage.
Circular Fields
When a circular magnetic field forms in and around a conductor due to the passage of electric
current through it, the following can be said about the distribution and intensity of the magnetic
field:
o The field strength varies from zero at the center of the component to a maximum at the
surface.
o The field strength at the surface of the conductor decreases as the radius of the conductor
increases (when the current strength is held constant)
o The field strength inside the conductor is dependent on the current strength, magnetic
permeability of the material, and, if ferromagnetic, the location on the B-H curve.
o The field strength outside the conductor is directly proportional to the current strength and it
decreases with distance from the conductor

Magnetization of Ferromagnetic Materials : Direct or Indirect
Magnetization Using Direct Induction (Direct Magnetization)
o With direct magnetization, current is passed directly through the component.
o The flow of current causes a circular magnetic field in and around the conductor.
o Ensure that good electrical contact is established and maintained between the test
equipment and the test component to avoid damage of the component
First Technique involves clamping the component between two
electrical contacts in a special piece of equipment. Current is
passed through the component and a circular magnetic field is
established in and around the component. When the
magnetizing current is stopped, a residual magnetic field will
remain within the component. The strength of the induced
magnetic field is proportional to the amount of current passed
through the component.
A second technique involves using clamps or prods, which are
attached or placed in contact with the component. Electrical
current flows through the component from contact to contact.
The current sets up a circular magnetic field around the path of
the current.

Magnetization Using Indirect Induction (Indirect Magnetization)
External magnetic field to establish a magnetic field within the component.
The use of permanent magnets is a low cost method of establishing a
magnetic field. However, their use is limited due to lack of control of
the field strength and the difficulty of placing and removing strong
permanent magnets from the component.
Longitudinal Magnetization Method (YORK) :
o Electromagnets in the form of an adjustable horseshoe magnet
(called a yoke) eliminate the problems associated with permanent
magnets.
o Electromagnets only exhibit a magnetic flux when electric
current is flowing around the soft iron core.
o When the magnet is placed on the component, a magnetic field
is established between the north and south poles of the magnet.
o Magnet field is inducted in the object between the poles
o A yoke essentially consists of permanent magnets or
electromagnets employing AC or DC

o Second technique of indirectly inducting a magnetic field in
a material is by using the magnetic field of a current carrying
conductor.
o A circular magnetic field can be established in cylindrical
components by using a central conductor.
o Typically, one or more cylindrical components are hung from
a solid copper bar running through the inside diameter.
o Current is passed through the copper bar and the resulting
circular magnetic field establishes a magnetic field within the
test components
o The use of coils and solenoids is a third technique of
indirect magnetization.
o When the length of a component is several times larger
than its diameter, a longitudinal magnetic field can be
established in the component.
o The component is placed longitudinally in the concentrated
magnetic field that fills the center of a coil or solenoid.
o This magnetization technique is often referred to as a "coil
shot".

Types of Magnetizing Current
1) Direct current
o From a storage battery
o Single phase rectifier
o Three phase rectifier
o D.C Currents allow magnet filed to greater depths up to 6 mm.
2) Alternative Current
o Mains supply is used.
o When AC is used to induce a magnetic field in ferromagnetic
materials, the magnetic field will be limited to a thin layer at the
surface of the component which is known as the "skin effect”
o AC be used only when the inspection is limited to surface defects
o AC Current promotes skin effect which give high sensitive to
detect surface cracks

Methods of Demagnetization
Method 1. Heat the part to above Curie temperature.
Method 2. Use mechanical vibrations.
Method 3. Subjecting the part to field continually reversing its direction and at the
same time gradually decreasing its strength to zero.
Remagnent magnetic fields can:
 affect machining by causing cuttings to cling to a component.
 interfere with electronic equipment such as a compass.
 create a condition known as "arc blow" in the welding process. Arc blow may
cause the weld arc to wonder or filler metal to be repelled from the weld.
 cause abrasive particles to cling to bearing or faying surfaces and increase wear.
A field meter is used to verify that the residual flux has been removed from a
component.
Industry standards usually require that the magnetic flux be reduced to less than 3
Gauss (3x10-4 Tesla) after completing a magnetic particle inspection.

Measuring Magnetic Fields
o To determine the direction and intensity of the magnetic field.
o The field intensity must be high enough to cause an indication to form, but not too high to
cause non-relevant indications to mask relevant indications.
o After magnetic inspection it is often needed to measure the level of residual magnetezm.
o Since it is impractical to measure the actual field strength within the material, all the
devices measure the magnetic field that is outside of the material.
The two devices commonly used for quantitative measurement of magnetic fields n magnetic
particle inspection are the field indicator and the Hall-effect meter(gauss meter)
Field indicators are small mechanical devices that utilize a soft iron vane that
is deflected by a magnetic field. The vane is attached to a needle that rotates
and moves the pointer on the scale.
Field indicators can be adjusted and calibrated so that quantitative
information can be obtained.
A Hall-effect meter is an electronic device that provides a digital readout of
the magnetic field strength in Gauss or Tesla units.
The meter uses a very small conductor or semiconductor element at the tip
of the probe.
Electric current is passed through the conductor.
The probe is placed in the magnetic field such that the magnetic lines of
force intersect the major dimensions of the sensing element at a right angle

Magnetization Equipment
o Magnetic field induced in the part must intercept the defect at a 45 to 90 degree angle.
o Flaws that are normal (90 degrees) to the magnetic field will produce the strongest
indications because they disrupt more of the magnet flux.
o It is important to be able to establish a magnetic field in at least two directions.
Portable Equipment:
o Permanent Magnets
o Electromagnetic Yokes
o Prods
o Portable Coils and Conductive Cables
o Portable Power Supplies
Stationery Equipment
o Designed for laboratory use or production environment.
o Common type is Wet horizontal (bench) unit
o Designed to allow for batch inspections
o The units have head and tail stocks (similar to a lathe)
with electrical contact that the part can be clamped between.
o A circular magnetic field is produced with direct magnetization.
o The wet magnetic particle solution is collected and held in a tank.
o A pump and hose system is used to apply the particle solution to the components
being inspected.

Permanent Magnets
o Permanent magnets can be used for magnetic particle inspection
as the source of magnetism (bar magnets or horseshoe magnets)
o Industrial magnets not to be used
o Permanent magnets are for inspection in underwater
environments or other areas, such as explosive environments,
whereas electromagnets cannot be used.
o Permanent magnets made small enough to fit into tight areas
Electromagnetic Yokes
o Used to establish a magnetic field.
o A switch is included in the electrical circuit so that the
current so the magnetic field can be turned on/off.
o They can be powered with AC from a wall socket or by DC
from a battery pack.
o This type of magnet generates a very strong magnetic field
in a local area where the poles of the magnet touch the part
being inspected.
oSome yokes can lift weights in excess of 40 pounds.

Prods are handheld electrodes that are pressed against the
surface of the component being inspected to make contact for
passing electrical current (AC or DC) through the metal.
Prods are made from copper and have an insulated handle to help
protect the operator.
One of the prods has a trigger switch so that current can be
quickly and easily turned on and off.
The two prods are connected by any insulator, as shown in the
image, to facilitate one hand operation. This is referred to as a
dual prod and is commonly used for weld inspections.
Using prods : electrical arcing can occur and cause damage to the
component if proper contact is not maintained between the prods
and the component surface.
Not allowed for inspecting aerospace & other critical components.
Portable Coils and Conductive Cables establish a longitudinal
magnetic field within a component
o Coils typically have three or five turns of a copper cable within the
molded frame. A foot switch is often used to energize the coil
o Ampere-turns is the amperage shown on the amp meter times the
number of turns in the coil

Magnetic Field Indicators:
Determining whether a magnetic field is of adequate strength and in the
proper direction is critical when performing magnetic particle testing
Hall-Effect Meter (Gauss Meter)
Gauss meter is to measure the tangential field strength on the surface of the
part. By placing the probe next to the surface, the meter measures the
intensity of the field in the air adjacent to the component when a magnetic
field is applied.
The advantages of this device are: it provides a quantitative measure of the
strength of magnetizing force tangential to the surface of a test piece,
It can be used for measurement of residual magnetic fields, and it can be
used repetitively.
The main disadvantage is that such devices must be periodically calibrated.
Quantitative Quality Indicator (QQI) or Artificial Flaw Standard
Assuring proper field direction & adequate field strength (used for wet method
only).
The QQI is a thin strip (0.05 or 0.1 mm thick) of AISI 1005 steel with a specific
pattern, such as concentric circles or a plus sign, etched on it.
The QQI is placed directly on the surface, with the itched side facing the surface,
and fixed to the surface using a tape then the component is then magnetized and
particles applied.
When the field strength is adequate, the particles will adhere over the engraved
pattern and provide information about the field direction.

Pie Gage
o The pie gage is a disk of highly permeable material divided into four,
six, or eight sections by non-ferromagnetic material (such as copper). The
divisions serve as artificial defects that radiate out in different directions
from the center. The sections are furnace brazed and copper plated. The
gage is placed on the test piece copper side up and the test piece is
magnetized.
o After particles are applied and the excess removed, the indications
provide the inspector the orientation of the magnetic field.
o Pie gages are mainly used on flat surfaces such as weldments or steel
castings where dry powder is used with a yoke or prods.
o The pie gage is not recommended for precision parts with complex
shapes, for wet-method applications, or for proving field magnitude.
o The gage should be demagnetized between readings
Slotted Strips
Slotted strips are pieces of highly permeable ferromagnetic material with slots of
different widths.
These strips can be used with the wet or dry method.
They are placed on the test object as it is inspected. The indications produced on the
strips give the inspector a general idea of the field strength in a particular area.
Magnetic Field Indicators:

Magnetic Particles comprises of Dry & Wet
The particles are key ingredient as they form the indications that alert the inspector to
the presence of defects.
Particles start out as tiny milled pieces of iron or iron oxide.
A pigment is bonded to their surfaces to give the particles color. The metal used for the
particles has high magnetic permeability and low retentivity.
High magnetic permeability is important because it makes the particles attract easily to
small magnetic leakage fields from discontinuities, such as flaws.
Low retentivity is important because the particles themselves never become strongly
magnetized so they do not stick to each other or the surface of the part.
Particles are available in a dry mix or a wet solution.
Dry magnetic particles
Available in red, black, gray, yellow and several other colors for high level
of contrast between the particles and test specimen
The fine particles have a diameter of about 50 µm while the course
particles have a diameter of 150 µm
This makes fine particles more sensitive to the leakage fields from very
small discontinuities.
A mix of rounded and elongated particles is used since it results in a dry
powder that flows well and maintains good sensitivity.
Most dry particle mixes have particles with L/D ratios between one and
two.

Wet Magnetic Particles applicable for water or oil
Generally more sensitive than dry because the suspension provides the
particles with more mobility
Easy to apply the particles uniformly to a relatively large area.
Fluorescent particles are coated with pigments that fluoresce when
exposed to UV light.
Particles that fluoresce green-yellow are most common to take advantage
of the peak color sensitivity of the eye but other fluorescent colors are
also available.
The carrier solutions can be water or oil-based.
Water-based carriers form quicker indications, are generally less
expensive, present little or no fire hazard, give off no petrochemical
fumes, and are easier to clean from the part. Water-based solutions are
usually formulated with a corrosion inhibitor to offer some corrosion
protection.
Oil-based carrier solutions offer superior corrosion and
hydrogen embrittlement protection to those materials that are
prone to attack by these mechanisms.
Visible and fluorescent wet suspended particles are available in aerosol
spray cans for increased portability and ease of application.

Dry Particle Inspection
Dry particles are dusted onto the surface of the test object
When an electromagnetic yoke is used, the AC current creates a pulsating magnetic field
that provides mobility to the powder.
Dry particle inspection is also used to detect shallow subsurface cracks.
Dry particles with half wave DC is the best approach when inspecting for lack of root
penetration in welds of thin materials.
Steps for performing dry particles inspection:
•Surface preparation
•Applying the magnetizing force
•Applying dry magnetic particles
•Blowing off excess powder
•Terminating the magnetizing force
•Inspection for indications
Wet suspension particle inspection,
All of the surfaces of the component can be quickly and easily covered with a relatively uniform
layer of particles.
The liquid carrier provides mobility to the particles for an extended period of time.
Best for detecting very small discontinuities on smooth surfaces.
Steps for performing wet particle inspection:
•Surface preparation
•Applying suspended magnetic particles
•Applying the magnetizing force
•Inspection for indications

MPT Equipments
Yoke
Bench Type MPI Machine Prods

Magnetic Particle Test Procedure

ADDITIONAL POINTS
Any part made of ferromagnetic material can be inspected by
MT. There are no restrictions as to the shape and size of the
component.
The ability of the method to provide indications depends upon
the ability of magnetic particles to move in response to leakage
magnetic fields.
The parts should be cleaned before they are subjected to
magnetic particle inspection.
Grease etc. will cause the dry powder stick to the surface of
the test object, resulting in poor indications.
The ferromagnetic particle may be suspended in air (dry
method) or in liquids such as oil or water (wet method).
The operator should detect not only discontinuities but also
make sure that all the discontinuities the specific method can
reveal have been located and evaluated.

Primary processes and related defects
a) Melting
b) Pouring
c) Cooling
Processing and related defects
a) Casting
b)Welding
c) Forging
d)Rolling
e) Heat treatment
f) Machining
g) Plating
h)Other processes
Processes and defects
Service and related defects
a) Overload
b) Fatigue
c) Corrosion
d) Brittle fracture
e) Others

AMERICAN SOCIETY OF TESTING AND MATERIALS (ASTM)
S.NO STANDARD NUMBER TITLE
1 ASTM A 275/A 275M Test Method For Magnetic Particle Examination Of Steel Forgings.
2 ASTM A 456 Specification For Magnetic Particle Inspection Of Large Crankshaft Forging.
3 ASTM E 543 Practice Standard Specification For Evaluation Agenice That Performing
Nondestructive Testing.
4 ASTM E 709 Guide For Magnetic Particle Testing Examination
5 ASTM E 1316 Terminology For Non Destructive Examination
6 ASTM E 2297 Standard Guide For Use Of UV-A And Visible Light Source And Meters Used In
Liquid Penetrant And Magnetic Particle Method.
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION (ISO)
S.NO STANDARD TITLE
1 ISO 3059 Non- destructive testing – penetrant testing and magnetic particle testing - viewing
conditions.
2 ISO 9934 Non- destructive testing - magnetic particle testing- part 1: General principles.
3 ISO 9934 Non- destructive testing - magnetic particle testing- part 2: Detection median.
4 ISO 9934 Non- destructive testing - magnetic particle testing- part 3: Equipment.
5 ISO 17638 Non- destructive test of welds- magnetic particle testing
6 ISO 23279 Non- destructive test of welds- magnetic particle testing of weld – Acceptance
levels.

EUROPEAN COMMITTEE FOR STANDARDIZATION (CEN)
S.NO STANDARD
NUMBER
TITLE
1 EN 1330 Non-destructive testing-terminology-part 7:term used in
magnetic particle testing
2 EN 1369 Founding – magnetic particle inspection
3 EN 10228 Non destructive test of steel forging-part 1: magnetic particle
inspection.
4 EN 10246 Non destructive test of steel tube- part 12: magnetic particle
inspection of seamless and welded ferromagnetic steel tubes
for the detection of surface imperfections.
5 EN 10246 Non destructive test of steel tube- part 12: magnetic particle
inspection of the tube ends of seamless and welded
ferromagnetic steel tubes for the detection of laminar
imperfections.

STANDARD PRATICE IN INDUSTRY
ASME Section V, Article 7

SCOPE
General requirements for carrying out the examination of welds in ferric To
meets the requirements of ASME Section V Article 7 and ASTM E-709-95.
DESCRIPTION OF METHOD
o This method involves the magnetisation of an area to be examined and
the application of ferromagnetic particles to the surface. The particles
gather at areas of magnetic flux leakage and form indications characteristic
of the type of discontinuity detected.
o Maximum sensitivity is achieved when linear discontinuities are oriented
perpendicular to the lines of flux.
o The AC electromagnetic yoke technique is restricted to the detection of
surface breaking discontinuities.

EQUIPMENT AND MATERIALS
The following equipment and consumables or their equivalent.
Magnaflux Y6 AC Yoke
Portable ultra violet light
Magnaflux WCP-1 White contrast paint
Magnaflux WCP-2 White contrast paint
Magnaflux 7HE Black Ink
Magnaflux SKC-NF cleaner
Magnaflux SKC-S cleaner
Magnaflux dry powder (red, yellow or grey colour)
Magnaflux 14 HF Fluorescent Ink
Magnaflux 20A Fluorescent Ink concentrate (water based)
Burmah Castrol magnetic field indicators Type 1 Brass finish.
PARTS TO BE EXAMINED
Welds in ferritic materials, whether in the as welded or dressed
condition and the associated heat affected zones and parent material
within at least one inch of the weld on both sides of the weld.

SURFACE PREPARATION
o Prior to the test the area to be inspected and at least one inch either
side shall be free from any features that may inhibit the test or mask
unacceptable discontinuities. These include but are not limited to, slag,
spatter, oil, scale, rough surface and protective coatings.
o Surface preparation by grinding, machining or other methods may be
necessary where surface irregularities could mask indications of
unacceptable discontinuities.
o The temperature of the test surface shall not exceed 135ºF for
magnetic inks and 600ºF for dry powders. (For dry powders, test
surface be clean and dry).
o For parts to be inspected using magnetic inks the area to be
inspected may, if necessary, be precleaned with a cloth lightly
moistened with cleaner.
o Where parts are to be examined using powders or fluorescent inks,
the surface finish as detailed in 5.1 to 5.4 is adequate.
o When using black magnetic inks the surface may be given contrast
enhancement by applying a thin, even coating of white contrast paint.

EQUIPMENT AND CONSUMABLE CONTROL
o The magnetising force of yokes shall be checked at least once a year or
after any damage and/or repair, The yoke shall be able to lift a weight of at
least 10 pounds at the maximum pole spacing that will be used.
o Magnetic powders shall be used on a once only, expendable basis. Care
shall be taken to avoid possible contamination.
o Magnetic inks are also once only, expendable materials and care shall be
taken to thoroughly agitate the ink before use.
o Magnetic inks mixed from concentrates shall be subject to a settlement
test before use. Settlement time shall be 30 minutes and settlement volume
for the solids shall be as below.
Fluorescent ink 0.1 - 0.4%
Non fluorescent ink 1.2 - 2.4%
o The black light intensity at the examination surface(15 in from the face of
the light lens filter) shall be not be less than 1000 µW/cm2. Any increase in
this value to suit clients specific requirements shall be detailed on the
technique sheet. The bulb shall be allowed to warm up for at least 5 minutes
before use.
o The black light intensity shall be checked at least every 8 hours of use in
using a calibrated black light meter.

LIGHTING CONDITIONS
o When conducting an examination under white lighting conditions, the
inspector shall ensure that the level of lighting is adequate at the surface of the
part (recommended minimum 100 foot candles or 1000 lux). 50 foot candles
(500 lux) lighting may be used if agreed with customer, for field inspections.
o Examinations under ultra violet lighting should have a background white light
level of less than 20 lux and an ultra violet intensity at the test surface of not less
than 1000 µ W/cm2. Any increase in these values shall be specified in the
technique sheet.
o The inspector shall allow at least 5 minutes for dark adaptation before
beginning the inspection.
o If the examiner wears glasses or lenses, they shall not be photosensitive.
DIRECTION OF MAGNETISING FIELD
o The magnetising field shall be applied sequentially in two directions
approximately perpendicular to one another.
o The direction of the field may be determined by using the Burmah Castrol
magnetic field indicator. This will give its strongest indications when placed
across the flux direction.
o Determination of field direction shall be carried out for each geometry of weld
to be inspected.

SEQUENCE OF OPERATIONS
o The surface to be inspected
oThe continuous magnetisation technique is to be employed.
o Ensure in all operations that the pole faces remain in maximum contact with the surface.
o Position the poles and turn on the magnetising field.
o For the wet magnetic particle method, apply the ink onto the area under test and allow to
flow over the surface such as to allow maximum exposure of the magnetic particles to any
flux leakage present, excess material may be GENTLY blown across the surface to aid
interpretation.
o Dry magnetic powders should be applied in such a manner that a light, uniform, dust like
coating settles on the surface of the area under inspection. Excess power may be GENTLY
blown across the surface to aid interpretation and increase exposure of magnetic particles to
any flux leakage present.
o Maintain the magnetising field for at least two seconds after above steps and inspect
immediately.
o Repeat the above sequence at approximately 90º to the above.
o Repeat the above steps to cover the complete weld area under inspection ensuring an
overlap between inspected areas of at least 25% of the pole spacing. The area to be inspected
shall be limited to a maximum distance of one fourth of the pole spacing on either side of line
joining the two legs. Pole area to be inspected shall be limited to a maximum distance of one
fourth of the pole spacing on either side of line joining the two legs.
o Pole spacing shall be limited to a maximum value equal to or less than that used when
conducing the lift test of the standard weight but shall be not less than 3 inches.

POST CLEANING
The inspection area shall be cleaned after inspection with solvent
(unless otherwise specified) to remove any excess residues from the
inspection process.
DEMAGNETISATION
Demagnetisation shall be carried out where specifically requested by
the client. The method to be employed shall be subject to agreement
with the client.
REPORTING
A report shall be prepared detailing the results of the examination.
The report shall contain sufficient information to enable a full
assessment of quality and to ensure that any non-acceptable areas
can be accurately located should repair be necessary.
Any datum’s used shall be unambiguous.
Any restrictions to test shall be noted.
A statement of acceptability against the acceptance standard should
be made.

EVALUATION OF INDICATIONS
o An indication may be the evidence of a surface imperfection. All
indications need not be relevant. Relevant indications are those caused by
leakage flux. Relevant indications due to unacceptable mechanical
discontinuities are to be noted, located and sized.
o Any indication which is believed to be non relevant shall be re-examined
again. Only indications having major dimension of greater than one
sixteenth of an inch shall be considered relevant.
o A liner indication is one having a length greater than its width. A
rounded indication is shape with a length equal to or less than three times
its width.
o Unacceptable indications shall be removed by chipping or grinding and
shall be re-tested if the repaired surface is free of sharp notches are
corners / grinding marks. When a defect appears to be fully removed the
area can be repaired and re-examined by the same method. Repaired area
shall be blended into the surrounding surface so as to avoid sharp notches,
crevices or corners.
o If required the repaired area shall also be re-examined by another
suitable NDT method.

MAGNETIC PARTICLE INSPECTION - ACCEPTANCE CRITERIA
ANSI/ASME B31.1, Power Piping
1. Evaluation of Indications
2. Acceptance Standards
The following relevant indications are unacceptable:
o Any cracks or linear indications.
o Rounded indications with dimensions grater than 3/16 in. (5.0 mm)
o Four or more rounded indications in a line separated by 1/16 in. (2.0 mm)
or less, edge to edge.
o Ten or more rounded indications in any 6 sq. in of surface with the major
dimension of this area not to exceed 6 in (150 mm) with the area taken in
the most unfavourable location relative to the indications being evaluated.

ASME Boiler and Pressure Vessel Code, Sec. VIII Div. 1 Pressure Vessels
Evaluation of Indications
Acceptance Standards
All surfaces to be examined shall be free of:
Relevant linear indications
Relevant rounded indications greater than 3/16 in.
Four or more relevant rounded indications in a line separated by 1/16 in. or less,
edge to edge.
AWS D1.1 Structural Welding Code - Steel
Inspections may be performed immediately after the completed welds have cool
ed to ambient temperature.
Magnetic Particle Testing on welds in ASTM steels A514 and A517 shall be performed
no sooner than 48 hours after completion of the weld.
Indications revealed by Magnetic Particle Testing shall be evaluated as per applicable
categories as follows:
Statically Loaded Structures: Acceptance criteria shall be as per 8.15.5 (i.e. 8.15.1) of
AWS D1.1 (1992 Edition)
Dynamically Loaded Structures: Acceptance criteria shall be as per 9.25.2
of AWS D1.1 (1992 Edition).
Tubular Structures: Acceptance criteria shall be as per 10.17.5 (i.e. 10.17.1) of AWS
D1.1.

API Standard 1104 Pipelines and Related Facilities
Classification of Indication
Any indication with a maximum dimension of 1/16 in. (1.59 mm) or less shall be
classified as non relevant.
Relevant indications are those caused by discontinuities. Linear indications are
those in which the length is more than three times the width. Rounded indications
are those in which the length is three times the width or less.
Acceptance Standards
Relevant indications shall be unacceptable when any of the following conditions
exists:
a. Linear indications evaluated as crater cracks or star cracks exceed 5/32 inch (3.96
mm) in length.
b. Linear indications are evaluated as cracks other than crater cracks or star cracks.
c. Linear indications are evaluated as IF and exceed 1 inch (25.4 mm) in total length
in a continuous 12-inch (304.8 mm) length of weld or 8 percent of the weld length.
d. Rounded indications shall be evaluated Individual or scattered porosity (P) and
Cluster porosity (CP)
ANSI/ASME B31.3, Chemical Plant and Petroleum Refinery Piping
Acceptance Criteria:
Any crack or linear indication is unacceptable.

MAGNETIC PARTICLE INSPECTION - PERSONNEL QUALIFICATION
Personnel performing examinations to this procedure shall be
qualified and certified in accordance with the requirements of ASNT
document SNT-TC-1A (1992 edition) ,ISO 9712 ,PCN or Accepted level
equivalent.
Only individuals qualified to NDT Level II or individuals qualified to
NDT Level I and working under the supervision of an NDT Level II may
perform the examinations in accordance with this procedure.
Evaluation of test results shall be by NDT Level II only.
MAGNETIC PARTICLE INSPECTION - REFERENCE DOCUMENTS
ASME SECTION V ARTICLE 7;
ASME SECTION VIII, Division I
ANSI/ASME B31.1
ANSI/ASME B 31.1
ANSI/AWS D1.1
ASTM E 709
API 1104
SNT-TC-1A of ASNT

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