& WRITTEN INSTRUCTIONS
11. Rotables: rotating engine parts
4.2.7 Process Controls
4.2.7.1 Where magnetic particle is applied using a total loss system the process control checks applicable to that suspension are not required. This exemption does not cancel any other checks that are required for process control.
4.2.7.2 Located Hanoi 4.2.7.2.1 Equipments
1. Magnetic test bench 2. AC & DC magnetic Yoke 3. Demagnetizer equipment 4. Black light lamp
5. Field indicator 6. Gauss/Teslameter 7. UV Light meter 8. White light meter 4.2.7.2.2 Accessories
1. Centrifuge Tube & Stand 2. QQI
3. KETOS Steel Ring 4. Central Conductor 5. Test load 4.5Kg 6. Test load 4.5Kg x 3 7. Magnetic Pie
8. Standard A longitudinal 9. Field Probe
4.2.7.2.3 Ferromagnetic Suspensions : Prepared Bath 14AM
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4.2.7.3 Located HCM 4.2.7.3.1 Equipments
1. Magnetic Bench –Nihon Denji Sokki 2. Magnetic Bench -Magwerks
3. UV Borescope- Olympus 4. Gauss/Teslameter model 5080 5. Field indicator 105645
6. Pocket Magnetometer 25 7. Magnetic Yoke -DC
8. Magnetic Inspection Coil, Model PL-10 9. Ultraviolet Lamp- Nihon Denji Sokki (110V) 10. Radiometer/Photometer
11. Illumination Meter 12. Ultraviolet Meter 13. Digital Radiometer 4.2.7.3.2 Accessories
1. Centrifuge Tube & Stand 2. QQI Type B
3. Magnetic Powder Blower 4. Central Conductor
5. ANSI 01 Series Tool Steel 6. Test piece RPS 700-TP4 4.2.7.3.3 Ferromagnetic Suspensions
1. Sherwin MT Suspension 2. Prepared Bath 14AM
4.2.7.4 Preparation of the testing agent / suspension
4.2.7.4.1 Turn on the machine pump. Pour the concentrate directly into the bath tank of the machine.
4.2.7.4.2 Run agitator pump for several minutes
Table 1: Periodic Inspection of Installation
Nature of the Inspection
Frequency
- Brilliance of fluorescent - Discoloration - White light intensity
- Internal short circuit check - Max and min coil current output - Head shot current output Measuring Device
Visual: minimum tank level As per 4.2.7.5.5 To meet accuracy ±5%
To meet accuracy ±5%
As per 4.2.7.8.1 As per 4.2.7.8.2
4.2.7.5 Examining the testing agent / suspension 4.2.7.5.1 Brilliance of fluorescent
1. Make a comparison between a standard sample of 'used' testing agent and 'unused' testing agent under black (UV) light for brilliance of particle fluorescence.
2. Record the result . 4.2.7.5.2 Discoloration
1. Check the contamination of the suspension for clarity and absence of yellow fluorescence under black light. Check for lint, dirt or scale.
2. Record the result . 4.2.7.5.3 Concentration
1. Run the pump for at least 30 minutes and at the same time thoroughly agitate and mix by hand all suspension which has settled upon the screen and along the bottom of the tank.
2. Fill centrifuge tube to the 100ml mark with suspension directly from the hose.
Demagnetize the suspension and allow the suspension to stand for 60 minutes for oil based or 30 minutes for water based to settle.
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3. Read the volume of the settled suspension in the tube. Settlement flask shall lie within the following:
Fluorescent ink – 0.1 to 0.3ml. Preferred 0.1 to 0.15
4. If the suspension is low in particle content, brush tank bottom to lift particles or add magnetic particle to obtain the required concentration.
5. If the suspension is high in particle content, add fluid to obtain the required concentration.
6. Record the result.
4.2.7.5.4 Contamination
From paragraph 4.2.7.5.3, check for the following:
1. Examine the liquid above the precipitate and compare with fresh suspension under black light. The liquid shall not show a noticeable difference and shall not fluoresce.
2. Examine the precipitate. If two distinct layers can be seen, read the volume of each layer. The top layer volume (contamination) shall not exceed 10% of the bottom layer volume and the contamination layer shall not fluoresce.
3. Record the result . 4.2.7.5.5 Viscosity (Subcontracted)
The viscosity of suspension shall be checked on 6 monthly basis and shall be maintained below 5.0 centistokes at room temperature.
Note: this check is necessary only if the solution remains in the tank more than 6 months.
4.2.7.5.6 All the results for paragraphs 4.2.7.5.1 – 4.2.7.5.4 shall be recorded .
4.2.7.5.7 If any unsatisfactory results are obtained for the test layout in paragraphs 4.2.7.5.1, 4.2.7.5.2, 4.2.7.5.4 or 4.2.7.5.5, then the agent/suspension shall be replaced.
4.2.7.6 Inspection Station 4.2.7.6.1 UV Light Intensity
1. Expose the sensor cell of the UV intensity meter to the black light.
2. Read off the scale.
3. The scale shall be not less than 1500µW/cm2 at the part being examined where the distance between the UV light filter and UV light intensity meter shall be not less than 381mm (15 inches). The wavelength of the black light shall be in the range of 3200 to 4000 Angstrom.
4. Record the results.
4.2.7.6.2 White light Intensity
1. Expose the sensor cell of the light intensity meter to the visible light at the inspection area with all adjacent black lights turned “on” and directly under the black light used for inspection.
2. Read off the scale.
3. The white light intensity shall not exceed 5 lux measured at the inspection surface with black light at 15 inches from the inspection surface.
4. Record the results.
4.2.7.6.3 Visible Light Intensity
1. Visible light shall be used when examining with non fluorescent magnetic particles and for interpretation of indications found with fluorescent magnetic particles. A minimum light intensity of 100fc (1000 lux) shall be available at the surface of the part undergoing examination or evaluation
2. Record the results.
4.2.7.7 MPI Machine
4.2.7.7.1 Maximum and minimum coil current output.
1. Set the controls for the machine to the maximum and minimum current value.
Pulse the current for both values.
2. Record the results.
4.2.7.7.2 Head shot current output (Electrical Capacity)
1. At minimum and maximum shall be determined, with a one (1) inch diameter copper bar, 18 inches long between the head or electrodes. Ensure contact at ends is good.
2. Record the results.
4.2.7.7.3 Internal short circuit check
1. Set for maximum amperage output. Set for “Head Shot”. Any deflection of the ammeter when the current is activated with no conductor between the contacts is an indication of an internal short circuit.
2. Record the results.
4.2.7.7.4 Ammeter Accuracy
1. The equipment meter reading should be compared to those of a calibrated control test meter incorporating a shunt or current transformer connected to monitor the output current.
2. The equipment meter reading shall not deviate by more than ±10% of full scale relative to the actual current values as shown by the test meter in two positions of the meter in each range setting.
4.2.7.8 System Performance Check.
4.2.7.8.1 Current Flow – Ketos Ring with permanently attached QQI.
1. Use a 1" to 1 3/16" diameter copper bar with 16" to 24" length for the Ketos Ring check.
2. Place the conductor through the center of the Ketos ring.
3. Center the Ketos ring on the length of the conductor.
4. Magnetize the Ketos ring circularly by passing the current specified in Annex I through the conductor.
5. Apply the suspension to the Ketos ring using the continuous method.
6. Examine the Ketos ring within 1 min after current application under a black light of not less than 1000 μW/cm2
7. The number of the holes indications shall meet or exceed those specified in table 2 and the indications on the QQI shall be clearly visible
8. Record the results.
9. Any observed deviation of sensitivity day to day shall be investigated
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Table 2: HANOI NDT Shop Amperage and hole indication for KETOS RING mag benches.
Model No: [TBD]. Originating date [TBD]
Type of suspension Amperage (FWDC OR HWDC)
Minimum number of holes indicated
Fluorescent oxide(wet) 1400 [TBD]
2500 [TBD]
3400 [TBD]
Table 3: HCM NDT Shop Amperage and hole indication for TOOL STEEL RING mag benches.
Model No: ND-40TB/ PSAH-545. Originating date 16 May 2011 Type of suspension Amperage
(FWDC OR HWDC)
Minimum number of holes indicated
Fluorescent oxide(wet)
500 3
1000 5
1500 6
2500 7
3500 9
4.2.7.8.2 Coil Magnetization (Test piece as per figure 13 of BS 6072).
1. Place the coil test piece at the bottom of the test coil.
2. Energize the machine with 300A (AC) or 430 A (DC).
3. Observe the strong transverse hole indications shows at the middle of the test piece.
4. The indication shows that the coil magnetization is good condition.
5. Record the results.
4.2.7.9 MPI Machine Operation
1. Local instructions for MT machines at HAN [TBD].
2. Local instructions for MT machines at HCM:
a. User’s care and instructions for Magwerks.
b. Operation manual for Digital Control Unit - Magnetic Bench - Nihon Denji Sokki.
4.2.7.10 Magnetization (As per ASTM E 1444)
The current shall produce a peak tangential-field strength in the range of 30 to 60 gauss (2.4 to 4.8 kAm-1) or in the range of 80 to 160 gauss according to manufacture requirement in all areas to be inspected.
Gauss meter readings shall take precedence over calculated current requirements.
4.2.7.10.1 Circular magnetization
1. Direct Circular Magnetization. The current shall be from 300 to 800 A/in of part diameter (12 to 32 A/mm)
2. Central Conductor Circular Magnetization.
a. Centrally Located Conductor. The current as per para 7.10.1 (1) shall be applied.
b. Offset Central Conductor. The current as per para 7.10.1(2) shall be applied except that the diameter shall be considered the sum of diameter of the central conductor and twice the wall thickness.
4.2.7.10.2 Longitudinal magnetization
Longitudinal magnetization shall be used for those parts that are at least two times as long as they are wide (i.e. L/D ≥ 2)
The peak current for longitudinal inspection shall be calculated as follows:
For parts positioned at the bottom of the coil:
For parts positioned at the center of the coil:
Where: I = Coil peak current to be used (amperes) N = Number of turns in the coil
R = Coil Radius L = Part length D = Part diameter
* NOTE: If a part is longer than 18 inches, L/D shall be calculated using a value of L
= 18, and D = Actual Diameter. If the resulting value of L/D is between 2 and 15, that calculated value will be used in the equations located on the preceding page.
If the resulting value of L/D is greater than 15, a value of 15 shall be used in the equations located on the preceding page.
If the resulting value of L/D is less than 2, the part will be inspected using an alternate approach.
When calculating the L/D ratio for a hollow part, D shall be replaced with an effective diameter,
Deff' calculated using:
Where: At = the total cross-sectional area of the part
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Ah = the cross-sectional area of the hollow portion of the part.
For cylindrical parts, Deff is equivalent to:
Where: OD = the outside diameter of the cylinder ID = the inside diameter of the cylinder
Separate magnetizing operations shall be used for both circular and longitudinal magnetization when parts contain changes in sections that differ by more than 30 percent. In such cases, the sequence of magnetization shall begin with the lowest current level and proceed in the direction of higher currents. For circular magnetization, the peak field strength of each section shall be maintained in the range of 30 to 60 gauss. Proper care shall be taken to avoid damage to smaller sections from overheating.
Residual magnetization shall be used when required by Drawing or program document
4.2.7.11 Magnetization (As per BS 6072) 4.2.7.11.1 Current Flow
The effective value of current in MPI is the peak value. However, it is impractical to use ammeters which are responsive to the peak value, hence it necessary to use instruments which response either to root mean square (rms) or to the mean value, and to calculate the peak from the known or estimated waveform.
The following table shall be used to determine indicated current values for the various methods of magnetism. Each machine in use shall be clearly marked with correction factors allowing conversion from peak to indicated and vice versa.
For Threading Bar application, where the bar is concentric with the part, the current value shall be calculated from the above table, based on the outside diameter of the part. In cases where the Threading Bar cannot be mounted concentric with the part, it shall be positioned away from the axis. The current value shall be calculated from the above table by taking the diameter of the circle centered on the Threading Bar with the outer surface of the part on its circumferences. In such cases the part shall be tested in stages to ensure 360°C coverage.
The central conductor used shall be covered with an insulating material, or non-conductive spacers to ensure that components do not touch the threading bar to avoid a danger of burning.
Current Waveform DC Source (Amp) Current for basically round parts
per mm diameter
28 20 18 9
Current for non-rounded parts per mm circumference
9 6.4 5.7 2.9
To test parts of varying diameters some compromise is necessary regarding the current used. When the largest diameter exceeds the smallest diameter by 50% or less, then the average of the currents normally required may be used to test the whole part (e.g. a part having diameters of 100mm and 75mm could be given are shot to test the whole length) calculated as follows:
100.0 at 20 amps AC per mm = 2,000 amps AC 75.0 at 20 amps AC per mm = 1,500 amps AC
3,500 amps AC Average current = 3,500 = 1,750 amps AC 2
Where the largest diameter exceeds the smallest diameter by more than 50% then more than one shot is required. A higher current than that required for test may be passed through the smaller diameter, in order to test the larger diameter providing due precautions are taken against burning and overheating and that defect indications are evaluated at the correct testing amperage for each diameter (e.g. a part made up of 25mm, 50mm and 100mm diameters would require three separate testing shots of current flow):
Shot 1: 25 at 20 amps AC per mm = 500 amps AC Shot 2: 50 at 20 amps AC per mm = 1,000 amps AC
Shot 3: 100 at 20 amps AC per mm = 2,000 amps AC 4.2.7.11.2 Coil
The peak current shall be calculated from the formula:
Where:
N = Number of turns I = Current
L = Length of part D = Diameter of part
K = 32,000 for DC and peak value of any wave for K = 30,000 for AC (r.m.s value)
Where the part length diameter L/D ratio is less than 5:1, extenders shall be used to extend the length of the flux path. If the L/D ratio is greater then 20 then the value 20 shall be substituted for L/D.
4.2.7.12 Symbols and Abbreviations
The following symbols and abbreviations shall be use in the MPI instruction.
Type of test Abbreviation Symbol
Magnetic Flow MF MF [ ] MF
Current Flow CF CF CF
Central conductor TB TB
Coil COIL COIL
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4.2.7.13 Pre-inspection 4.2.7.13.1 Demagnetization
The part shall be demagnetized before examination if prior operations have produced a residual magnetic field that may interfere with the examination
4.2.7.13.2 Surface Cleanliness and Finish
The surface of the part to be inspected shall be essentially smooth, clean, dry and free of oil, scale, machining marks, or other contamination or conditions that might interfere with the efficiency of the inspection. After cleaning parts shall be inspected as soon as possible to reduce the possibility of corrosion. In all circumstances they shall not remain unprotected for a period exceeding 24 hours"
4.2.7.13.3 Coating
1. Magnetic particle examination shall not be performed with coatings of paint or chrome plated greater than 0.08mm (0.003 in) in thickness and ferromagnetic coatings such as electroplated nickel greater than 0.03mm (0.001 in) in thickness.
2. Nonconductive coatings must be removed when electrical contact is to be made.
4.2.7.14 Inspection Procedure
4.2.7.14.1 The suspension shall be circulated for at least 30 minutes before the testing begin.
4.2.7.14.2 White light shall be no more than 1 foot candles (10 lux) in the inspection booth with the black lights illuminated and warmed up.
4.2.7.14.3 Black light intensity shall be a minimum of 1500 µwatts per cm2 at 15 inches from the face of the light lens filter. Wavelength of the black light shall be in the range of 3200 to 4000 angstroms.
4.2.7.14.4 The UV light shall be allowed to warm up a minimum of 5 minutes before use for inspection.
4.2.7.14.5 Allow 1 minute for dark adaptation of the eyes before beginning the inspection.
4.2.7.14.6 Inspectors shall not wear eyeglasses with light sensitive (photo chromatic) lenses.
4.2.7.14.7 For all positions, suspension shall be applied to the part until all surfaces requiring inspection are thoroughly covered.
4.2.7.14.8 All VAECO originated instructions shall be controlled by gauss meter readings, which shall take precedence over calculated current readings.
4.2.7.14.9 Immediately after diverting the suspension, the part shall be magnetized at the appropriate amperage with two current pulses of approximately ½ second duration.
4.2.7.14.10 Parts shall be inspected for discontinuity indications using a X 5 to X 10 magnifier and the locations of the discontinuities shall be marked on the part.
4.2.7.14.11 Visual aids such as mirrors and borescopes shall be used when geometric configuration prevents surfaces from being visible with ± 30º of the normal (90º) viewing angle.
4.2.7.14.12 Demagnetization Procedure
All parts shall be demagnetized as follows:
1. With the coil energized, the part shall be held about one foot in front of the AC demagnetizing coil and then moved slowly through the coil to a point three feet beyond it when the current will be stopped.
2. Parts of complex configuration shall be rotated and tumbled while passing through the energized coil.
3. This process shall be repeated as necessary until field indicator shows the residue magnetism of the parts is within ± 3 gauss.
4.2.7.14.13 Post Cleaning
Parts shall be thoroughly cleaned before proceeding to the next process. Those parts containing discontinuity indications shall be marked. After cleaning parts shall be inspected as soon as possible to reduce the possibility of corrosion. In all circumstances they shall not remain unprotected for a period exceeding 24 hours"