Penetrant Training BAe.pptx

BAE SYSTEMS
PRESTWICK
Non-destructive Testing - Dye
Penetrant Inspection

Introduction
The aircraft industry make heavy use of forming and
machining methods when producing components for
aircraft. When the alloys are formed or machined
stresses are introduced and these can lead to cracks
appearing.
Obviously safety and reliability are paramount to this
industry therefore methods must be employed to
ensure the components are defect free whilst not
compromising the component quality.
One method, offered by Non-Destructive Testing,
which is used to detect surface defects is known as
Dye Penetrant Inspection.

The History of Dye Penetrant
Inspection
With the exception of visual inspection, Penetrant Inspection is
probably the oldest NDT method. Hundreds of years ago
blacksmiths would soak forged parts in oil and wipe the excess from
the surfaces. They would then coat the surfaces with a powder and
any cracks present would show as wet spots on the powder. Used
extensively in the railroad yards, this process was termed the 'oil &
whiting test‘.
In the mid-late 1930's Robert & Joseph Switzer incorporated
coloured dyes in penetrants for better contrast. In 1941 they
introduced penetrants with fluorescent dyes which were viewed
under a black light and gave better contrast than visible dyes.
This method was quickly accepted by the military for aircraft part
inspection and has since been adopted by nearly all fields of
manufacturing. It has been used at Prestwick since the first aircraft
parts were produced.

Definition of Dye Penetrant
Inspection
Dye Penetrant Inspection is a method of Non-
Destructive Testing components for surface defects
using colour or fluorescent dyes to highlight such
defects.
The parts are immersed in the dye and left draining for
a period of time before having the excess removed.
The parts are then coated in developer and again left
for a period of time after which any defects can be
observed.
This happens because dye will have penetrated any
surface defects present, hence the name 'DYE
PENETRANT INSPECTION‘.

Uses of Dye Penetrant
Inspection
1. For inspection of parts without causing
failure of that part.
2. To inspect Non-Ferrous components for
surface defects.
3. For local inspection of critical areas when
damage is suspected on fuselages and
other major assemblies.
- Items 1 & 2 are the main uses of Dye
Penetrant Inspection at Prestwick.

DPI Personnel
Approved Operators
Personnel employed in the Dye Penetrant
Inspection process are Grade - B
operators who hold approvals to carry out
the process.

DPI Personnel
Support Personnel
Manufacturing Engineers translate part and assembly
drawings into manufacturing processes, in the form of job
cards and manufacturing instruction sheets, which show in
detail the preferred sequence and methods of testing.
Quality & Engineering Function provides the Manufacturing
Engineer with specialist help on NDT processes.
Quality Engineer (NDT) is responsible for the control of all
processes and equipment through regular monitoring of the
solutions/equipment to the controlling specifications.

DPI Principle
Capillary Action
Crack Penetrant
Penetrant is applied to the surfaces and is drawn into cracks by
capillary action.

DPI Principle
Removal of Excess
Crack Clean Surface
The excess penetrant is removed from the surfaces but penetrant
drawn into any cracks remains.

DPI Principle
Developer Application
Bleed Out
Crack Developer
The developer is applied and draws the penetrant from the crack, i.e.
blotting paper.

DPI Principle
Methods of DPI
Dye Penetrant Inspection can be split into two main
categories;
1. Fluorescent Dye - this dye requires a black light source
(UV-lamp) but has higher sensitivity than other dyes.
2. Visible Dye - this is less sensitive than fluorescent dye
but does not require a black light source and a
darkened enclosure therefore it is less expensive.
There are four levels of sensitivity, Levels 1 to 4, with 4
being the most sensitive and the most costly. The
penetrant dyes can also be further divided into three
methods of removal;

DPI Principle
1. Water-Washable - this penetrant has an in-built
emulsifier and is removed simply by washing with
water and is the preferred method for detecting deep
discontinuities because the penetrant is washed out of
all the shallow recesses. It is ideal for screw threads,
key-ways and rough surfaces.
2. Post-Emulsifiable - this is removed by applying an
emulsifier and then washing in water. This method is
preferred for shallow discontinuities because this
penetrant does not wash away with water therefore
clings to any shallow recesses.
3. Solvent Removable - this penetrant is removed by
applying a solvent cleaner to the part. This method is
mainly used where washing with water is impractical,
e.g. when inspection is required on an assembled
aircraft.

DPI Principle
When the excess penetrant has been removed
developer must be applied. There are various methods
of applying developer such as dusting, dipping, flow-
over, brushing and spraying. There are three types of
developer available;
1. Dry Developer - the surfaces must be dried
thoroughly before application, generally using heat.
The usual method of application is by dusting. Dusting
can be achieved by either using a powder puff for
application or by putting the parts in a dust storm
cabinet which surrounds the part with swirling dust.

DPI Principle
2. Aqueous Developer - the surfaces are dried after
application, again heating would be involved. The usual method of
application is by dipping.
3. Non-Aqueous Developer - the surfaces must be dried
thoroughly before application when using this developer. The
method of application is usually by spraying. This developer is
normal used when no heating source is available.
 It is important to use penetrant, penetrant remover and
developer all from the same manufacturer for the best results.
Mixing of products from different manufacturers can cause the
results to be marginal.
 DPI is widely used because the materials are relatively
inexpensive and it is a simple and reliable process.
 Limitations of the process are that it is messy, it requires good
ventilation and there is not normally a permanent record
because the part is passed to the next operation if it is
acceptable and scrapped if it has failed. Photographs would
have to be taken if visual evidence was required to

DPI Principle
Processing parameters have to be tightly controlled to
guarantee the integrity of the results. The following
problems may occur with poor process control;
1. High pressure air or water could remove penetrant from
some defects therefore they could go undetected.
2. Processing times must be followed because excessive or
delayed viewing times could lead to false indication due to
penetrant bleed-out.
3. Excessive temperatures could affect the penetrant viscosity
which would mean that the penetrant would not develop
correctly.
4. Incorrect lighting conditions could mean some slight
indications were not visible or were difficult to see.
5. Contamination could affect the ability of the penetrant to
perform as required.

DPI Principle
Approvals
Personnel involved in DPI have to be approved before carrying
out any Dye Penetrant work. There are three levels of approval;
Level 1: This is an in-house approval which will allow the person to
work to documented instructions and pass or fail parts with the
approval of Level 2 personnel. They must also have received a
minimum of 8 hours training and 130 hours practical experience.
Level 2: This is an in-house approval which will allow the person to
perform Level 1 tasks and also make adjustments to the process,
formulate written instructions for Level 1 Personnel and
supervise Level 1 personnel. They must also have received a
minimum of 8 hours training and 270 hours practical experience.
Level 3: this level requires PCN (Personnel Certification in Non-
Destructive Testing) approval which will allow the person to
perform Level 2 tasks and also set-up the system, calibrate

DPI Principle
Cont.
write techniques for Level 2 to follow and
examine and supervise Level 2 personnel. They
must also have attended and passed a training
course approved by a PCN body and must have
relevant work experience.
In addition to these requirements personnel
must also take an eye test for near vision every
year and colour perception before certification or
recertification.

The Prestwick Process
General
The process of Dye Penetrant Inspection can be split into three main
processes at Prestwick.
1. Water-Washable (F1)
2. Post-Emulsifiable (F2)
3. Electrostatic
All three processes use the Fluorescent Dye method at Level 2 sensitivity.
1 & 2 are immersion processes whilst 3 is a spray booth process.
Technique sheets are available for all parts detailing exactly which method
should be used.
Every job processed on the line is logged and has the following details
recorded for traceability purposes: -
 Report No.
 Aircraft Type
 Quantity

Part Description
Part No.
Customer
Start/Finish Date
Condition (Result)
Operator Stamp (ID)
Remarks (if req.)
Control No. (Order No.)
Misc. (Next operation)
 All jobs appearing with Kanban Express cards must
be given priority and processed first.
 A portable process is available for local inspection but
is mainly used on fully or partially assembled aircraft.

The customer process specifications for Dye Penetrant
Inspection are as follows;
CUSTOMER SPECIFICATION
Jetstream PS 54-3-1
Avro AVP 7-500
Raytheon BAEP 2501
Lockheed C-0567
Airbus ABP 6-5230

Water-Washable (F1)
This process is generally used for Aluminium Alloys and
Extrusions. After deciding which job was the highest priority
the operator would work to the following sequence of
operations;
1. Vapour Degrease - The components are degreased to ensure
no surface contamination remains.
 Duration: 2mins
 Temp: 75° C
 Solution: Trichloroethane
The components should be allowed to cool to hand touch
before the next step.
2. Penetrant immersion - The parts are now dipped in the
penetrant and left to drain.
 Duration: 30mins drain
 Temp: Room Temp
 Solution: Ardrox 970P24

3. Water Wash - The excess penetrant is now removed by washing the components
in a water tank.
 Duration: Operator dependant
 Temp: Room Temp
 Solution: Water
4. Hot Water Dip - The components are dipped into a hot water tank to
assist in the drying process and also remove any last remnants of
penetrant.
 Duration: 30secs
 Temp: 70°-80° C
 Solution: Water
5. Air Dry - The parts are blown with air at a maximum pressure of 1 bar.
 Temp: Room Temp
 Solution: Air
6. Oven Dry - The parts are placed in the oven to ensure they are completely dry.
 Duration: 10mins max.
 Temp: 80° C
7. Developer - The components are put into a dust storm cabinet and
dusted with dry developer.
 Duration: 10mins min.
 Temp: Room Temp

8. View - The parts must be inspected
within 30 minutes of developer application
under black light conditions.
 Duration: Specified by Operator
 Background: <10 Lux
 Lamp Output: 0.5 MW/cm sq.
9. Clean - Remove the remaining developer
using blown air.

Post-Emulsifiable (F2)
This process is generally used for Titanium Alloys and Steels
as it is more sensitive. After deciding which job was the
highest priority the operator would work to the following
sequence of operations;
1. Dip Clean - The components are immersed in a cleaning
agent to ensure no surface contamination remains.
 Duration: 30mins
 Temp: 60°-70° C
 Solution: Alumiclean
2. Hot Water Wash - The components are given a wash to
remove any traces of the cleaning agent before the penetrant
is applied.
 Temp: 70°-80° C
 Solution: Water
The components should be allowed to cool to hand touch

3. Penetrant immersion - The parts are now dipped in the penetrant
and left to drain.
 Duration: 30mins drain
 Temp: Room Temp
4. Water Wash - The components are now washed to remove any
heavy amounts of penetrant.
 Temp: Room Temp
 Solution: Water
5. Emulsifier - The components are put into the emulsifying solution
to aid removal of the rest of the excess penetrant.
 Temp: Room Temp
 Solution: Ardrox 9PR12
6. Water Wash - The components are now washed to remove the
remaining excess penetrant.
 Temp: Room Temp

7. Hot Water Dip - The components are dipped into a hot water tank to
assist in the drying process and also remove any last remnants of
penetrant.
 Duration: 30secs
 Temp: 70°-80° C
 Solution: Water
8. Air Dry - The parts are blown with air at a maximum pressure of 1
bar.
 Temp: Room Temp
 Solution: Air
9. Oven Dry - The parts are placed in the oven to ensure they are
completely dry.
 Temp: 80° C
10. Developer - The components are put into a dust storm cabinet
and dusted with dry developer.
 Duration: 10mins min.

11. View - The parts must be inspected within 30 minutes of
developer application under black light conditions.
 Lamp Output: 0.5MW/cm sq.
12. Clean - Remove the remaining developer using blown air.
Electrostatic
This process is used for larger details that will not fit into the
immersion tanks. The components are hung on hooks which
are earthed, thus earthing the components. The solutions /
chemicals are atomised and then negatively charged by the
gun which sprays them in a mist. The mist envelopes the
components and is attracted to the surface which it then flows
over ensuring an uniform coating over the whole surface.

After deciding which job is the highest priority the operator would
work to the following sequence of operations;
1. Vapour Degrease - The components are degreased to ensure no
surface contamination remains.
 Duration: 2-5mins
 Temp: 75° C
 Solution: Trichloroethane
2. Hang on Hooks - The are mounted on hooks on the spray booth in
such a way that the component surfaces can be easily coated.
3. Penetrant Spray - The components are sprayed with penetrant from
a pressurised nozzle. The operator ensures the parts are completely
coated.
 Temp: Room Temp
The components are then left for a maximum of 30 minutes to allow
the penetrant to take effect.

4. Spray Rinse - The parts are now rinsed with water at a
controlled pressure (2 bar max.)
 Temp: Room Temp
 Solution: Air / Water Droplets
5. Air Dry - The operator dries the components using air
and paper towels. He must ensure they are completely
dry before progressing to the next step.
 Temp: Room Temp
6. Spray Developer - The developer is now applied by an
air gun which applies a light dusting to the components.
 Temp: Room Temp
 Solution: Ardrox 9D4A

7. View - The parts must be inspected within 30 minutes of
developer application under black light conditions. A hand
held UV lamp is used.
 Lamp Output: 0.5MW/cm sq.
8. Clean - Remove the remaining developer using blown air.
All Processes
The type of defects looked for are cracks and porosity /
pitting. Cracks would show up under the UV light as sharp,
thin lines. Porosity / pitting would show up as round spots
under UV lighting.
If any parts are found to be defective an MRB report is
completed and the parts are quarantined awaiting disposition.
When the parts have been inspected and are deemed to be
satisfactory, they are placed in the appropriate area awaiting

An important point to remember is that all
thermal treatments should be carried out
prior to DPI and any mechanical finishing
work such as blasting or dressing should
be conducted after DPI.

Testing/Process Checks
Operator Checks
The operator processes a test piece with known defects along with
the first job down the line every day. The known defects must be
visible when viewed after processing. This ensures the processing
parameters are correct.
In addition to this the operator checks the following variables -
temperature of the wash water, hot water dip and oven, the pressure
in the water jets and air dryer, the cleanliness of the wash water and
that the developer is dry.
A record is kept, with the operator's stamp against it, that this has all
been checked.
QA (NDT) Checks
Quality personnel perform weekly checks to ensure the process is
within specification. These checks include the test pieces, working
pressures, working temperatures, UV lamp outputs and the

Testing / Process Checks
cleanliness of the tanks. They also ensure that the
electrostatic process is operating correctly.
All of this information is recorded and kept on file. They
also verify that the operators have been recording their
process checks.
Calibration
The pressure and temperature gauges on the processing
equipment are on the calibration system and are
recalibrated every 6 months. The meter for measuring the
UV lamp outputs is also on the calibration system but this
calibration is externally sourced.
A sample of the penetrant is sent to an external source
every 6 months to ensure it is within specified
requirements.

DPI Process Environmental
Considerations
Waste Chemical Disposal - Tanks containing the
penetrant and the emulsifier are continually topped up
with new chemicals to counter the effects of drag out,
therefore there is no need to dispose of the chemicals.
Wash Water Disposal - Wash water from the tanks is
treated in the effluent plant before being discharged. The
discharge meets public safety standards.
Extraction of Fumes - The Alumiclean and the developer
have extraction fitted directly above the tanks to remove
harmful fumes. There is also a general extraction system
fitted to the dip processes and the electrostatic booth
which remove other fumes.

Alternatives to Dye Penetrant
Inspection
Alternatives to DYE PENETRANT INSPECTION would
be;
1. MPI
 This method makes use of magnetic field behaviour
and therefore can only be used on ferrous metals.
As with DPI, this method does not normally produce
a permanent record because any indications
disappear when the magnetic field is removed. MPI
can also detect sub-surface defects.
2. Visual Inspection
 Parts could be inspected by eye, with or without
magnification, but not all cracks can be easily
identified by eye, especially on rough surfaces.

Inspection
3. X-Ray Inspection
 This process passes x-rays through the parts onto
film. Any denser defects appear as lighter areas on
the film and any cracks / cavities appear as darker
areas on the film. This provides a permanent record
and is also a much cleaner process. This is
outweighed by the high cost of the equipment and the
dangerous nature of X-Rays needing strict safety
requirements. X-Ray inspection is normally used for
detecting voids or inclusions.

Inspection
4. Eddy Current Inspection
 This can be used to detect cracks but can only be
used economically when inspecting very small
areas. There are also problems when using this
method to inspect ferrous components as the
Eddy Currents magnetise the component.

Safety
Legal Obligations
Employees must be aware of the requirements in
the company safety and fire prevention
regulations, copies of which are available from the
Health and Safety Manager.
Technical Regulations
In the DYE PENETRANT INSPECTION process
many strong chemical solutions are used.
Operators and all other personnel must abide by
all safety instructions on plant, equipment and
consumable packaging.

Safety
HARMFUL CORROSIVE
HIGHLY
FLAMMABLE TOXIC
LOOK FOR THESE WARNINGS ON MATERIALS
OBEY THESE INSTRUCTIONS

Process Selection
THE SA. 41. PROCEDURE
A
B
C
D
BRITISH AEROSPACE PROCESS INFORMATION
AEROSTRUCTURES R
EQUEST FORM
PRESTWICK
Process Info. Form Ser. No. _______________________
F
ill in boxes marked *
Part Number:- * Raised by:- *
Customer or Project:- * D
ate:- *
Operations:- *
Background (if any):- *
Op. No. Dept. Operation Description
S
pecial Notes.
Continued Overleaf
Related P.I.F. Nos. C
ompiled:-
O
p Desc. Sht. SA666A D
ate:-
Thermal Treeatment SA27 A
pproved:-
Protective Treatment Sa27 D
ate:-
Procedure Reference SP.45 Network location: T: pal common pirf.doc Form Ref. SA41 Issue 1

Process Selection
THE SA. 41. PROCEDURE
To receive detailed information on Dye Penetrant
Inspection use the SA.41. Form available from
Quality & Engineering.
1. Fill in details requested in Section B. Part C can
be used for further information.
2. Pass to Engineering Support.
3. Receive information in Section C.
4. Check information approval and other details in
Section D.
5. Enter information onto the Job Card.
6. Section A is for office use only.

Conclusions & Observations
1. DYE PENETRANT INSPECTION is a process
carried out by GRADE 'B' APPROVED
OPERATORS working to detailed
manufacturing instructions.
 We must remember that people need ACCURATE
PROCEDURES to carry out such a process if they
are to achieve QUALITY PRODUCTS.
2. PASSENGER SAFETY MUST BE OUR TOP
CONCERN.
3. THERE IS NO LAY-BY IN THE SKY.
4. IF IN DOUBT ASK !

Penetrant Training BAe.pptx

Recommended

Recommended

More Related Content

Similar to Penetrant Training BAe.pptx

Similar to Penetrant Training BAe.pptx (20)

Recently uploaded

Recently uploaded (20)

Penetrant Training BAe.pptx