Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades “Liquid Penetrant Inspection (LPI) and Magnetic Particle Inspection (MPI)” By: Ritesh Pandya Std Id: c0922196 Lambton College of Applied Arts and Technology QEM-1303 Materials and Testing Prof. Ashvinkumar Bulsara Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades Abstract Commented [A1]: at low costs Basic Principles of LPI and MPI Tests (5 paras max. no test method, describe the concept) Commented [A2]: Inspection is usually performed under ultraviolet light but can be performed under white light, depending on the type of dye used and sensitivity required. Liquid penetrant inspection (LPI), also known as fluorescent penetrant inspection, is a widely employed nondestructive testing (NDT) method used to detect surface-breaking defects in nonporous materials. It is used to locate casting, forging, and welding surface defects such as hairline cracks, fatigue cracks, leaks, and porosity that are open to the surface. LPI is widely used in industries like aerospace, automotive, and manufacturing due to its simplicity and effectiveness for identifying surface flaws. The concept behind LPI revolves around the principle of capillary action, where a low viscosity liquid (penetrant) is applied to a clean and dry surface of the material. Because of its low viscosity, the liquid seeps into any surface discontinuities. After some time, the excess liquid is wiped-off and a developer is used to draw out the liquid trapped in defects, forming visible indications. Note that LPI is limited to surface flows, as the liquid penetrant cannot penetrate beneath the surface of the material, which is where MPI comes in handy. Fluorescent vs Visible penetrants Extra Magnetic Particle Inspection (MPI) is another non-destructive testing (NDT) technique, specifically used to detect surface and subsurface defects in ferromagnetic materials. The term Ferromagnetic refers to materials that can be magnetized or strongly attracted by a magnetic field. This method was first used around 1868 to locate cannon barrel defects. Cannon barrels were magnetized, and a magnetic compass was moved down the length of barrel. If any defect was present on or beneath its surface, the magnetic flix would leak and cause the compass needle to move, making it easy to locate defects. The core concept of MPI relies on the magnetic properties of materials. When a defect-free ferrimagnetic material is magnetized, the magnetic field lines will pass through without any interruption. However, any crack or discontinuity on or beneath the surface will disrupt the magnetic field, creating leakage fields. When magnetic particles, typically in powder or liquid form are applied on such surface, they will be attracted to the areas of magnetic field leakage, showing visible indications of the size and location of defects. Unlike LPI which relies solely on capillary action, MPI detects both surface and near-surface defects, making it more versatile for inspecting critical components in automotive, oil & gas, and heave machinery manufacturing industries. Each area needs to be examined twice; second examination needs to be perpendicular to the first. MPI Extra How MPI can be improved? Commented [A3]: One of the primary advantages of LPI is its versatility. It can be applied to a wide range of materials including metals, plastics, ceramics, and glass, as long as the material is non-porous. This method can identify both small and large defects that might be missed by visual inspection alone. Commented [A4]: •The sensitivity of the test can be adjusted by varying the type of penetrant and developer used. Fluorescent penetrants, which glow under ultraviolet light, are often used in high-sensitivity inspections where even the smallest imperfections must be detected. Visible penetrants, which show contrast under normal light, are used for general-purpose inspections. The success of the test depends on surface preparation, as contaminants like oil, paint, or rust can obstruct the penetrant from entering defects. Commented [A5]: This is a simple low-cost method of detecting surface-breaking flaws such as cracks, laps, porosity, etc. To be detected, the flaw must reach the surface to be tested. Penetrant testing is one step up from visual inspection and offers many advantages, such as speed, large-area coverage and cheapness. Fluorescent penetrants are usually used when the maximum flaw sensitivity is required. The principle of liquid penetrant testing is that the liquid penetrant is drawn into the surface-breaking crack by capillary action and excess surface penetrant is then removed; a developer (typically a dry powder) is then applied to the surface, to draw out the penetrant in the crack and produce a surface indication. Cracks as narrow as 150 ... Commented [A6]: However, the magnetic flux will only leak out of the material if the discontinuity is generally perpendicular to its flow. If the discontinuity, such as a crack, is parallel to the lines of magnetic flux, there will be no leakage and therefore no indication observed. To resolve this issue, each area needs to be examined twice. The second ... Commented [A7]: Any surface-breaking or near-surface defects disrupt the magnetic field, creating leakage fields. Magnetic particles, typically in powder or liquid form, are applied to the surface of the material. These particles are attracted to the areas of magnetic flux leakage, thereby forming visible indications of defects. ... Commented [A8]: The sensitivity of the MPI process can be enhanced by using different magnetization techniques, such as longitudinal or circular magnetization, and by employing fluorescent magnetic particles for more precise detection. Additionally, alternating current (AC) or direct ... Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades Safety Equipment Emergency Stop Button (e-stop) First Aid Kit Safety Shoes Safety Glasses, Safety Gloves & Lab Coat Test Equipment and Supplies The procedure of both liquid particle and magnetic particle inspection tests was performed using standardized equipment. Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades Liquid Penetration Inspection Test Equipment Spotcheck® Magnaflux SKC-S Cleaner Spotcheck® Magnaflux SKL-SP2 Penetrant Spotcheck® Magnaflux SKD-S2 Developer Clean Cloth/Paper Towel Vernier Calipers/Steel Ruler Light Meter Bench Protection Sheet Dryer for Developer Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades Magnetic Particle Inspection Test Equipment Spotcheck® Magnaflux SKC-S Cleaner Magnetic Yoke Light Meter Clean Cloth/Paper Towel Magnetic Dusting Powder 10lb Magnet Calibration/Test Bar W-FI-10 Magnetic Field Indicator Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades Sample Information Sample ID: MT 17046 (Cast Steel Pipe) This is a cast steel pipe that failed at a weld, leading to significant and costly downtime for the customer. The failure likely occurred at a critical weld joint, which requires a thorough investigation to determine the cause of the failure and potential weaknesses in the welding process or material. Test Piece: MT 17046 Sample ID: MT 17048 (Cylinder Head) This sample is a cylinder head, suspected of having cracks. Cracks in a cylinder head can lead to severe mechanical failures, potentially compromising engine performance and efficiency. The inspection will focus on identifying any surface or subsurface flaws that could affect the integrity and performance of the part. Test Piece: MT 17048 Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades Acceptance Criteria The acceptance criteria for Liquid Penetration Inspection (LPI) and Magnetic Particle Inspection (MPI) for the given samples will follow ASME Code Section VIII Div. 1 Appendix 7 Paragraph 4C – 2007. Specifically, for castings used in pressure vessels and rotating equipment, any surface indications revealed by the tests will be deemed unacceptable if they exceed the following allowable limits. Any linear indication greater than ¼ inch in length is considered a defect and must be addressed to ensure the integrity of the component. The test also requires a minimum light intensity of 100-foot candles (1000 Lux) at the inspection surface, which was met during our test (refer Fig). Light Meter Reading at Room Lighting Light Meter Reading with External Light Bulb Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades LPI Test Method and Set Up Bench Protection Sheet Developer Test Samples Penetrant Clean Cloth/Paper Towel Cleaner LPI Test Set Up Major Steps of Liquid Penetrant Inspection: ▪ Surface Pre-cleaning: This can include grinding, wire brushing or simply wiping the part with cleaner/remover to remove dirt, oil, or any contaminants that could interfere with the inspection. The cleaner allowed to sit for a few minutes and then wiped with a clean cloth. Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades ▪ Penetrant Application: Next, penetrant is either sprayed from the aerosol can or applied with a brush. The penetrant is allowed to dwell for a specified time and observed as the it seeps into any flaws. This soak time should not be long enough or the penetrant to dry. ▪ Penetrant Removal: The penetrant is then carefully removed from the surface using a clean, dry, lint-free cloth. Next, cleaner/remover is sprayed on another clean cloth and the part is wiped again, leaving penetrant only in the defects. ▪ Developer Application: A thin and even layer of developer is sprayed on the part surface and later dried using a dryer. This draws out the penetrant from any present flaws, making them visible on the surface. Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades ▪ Inspection: The part is visually examined under appropriate lighting (e.g., UV for fluorescent penetrant) to identify deep red indications. Length of indications are measured for evaluation Defects will be highlighted by a deep red indication. ▪ Post-cleaning: Once indications are located and documented, the part is again cleaned to remove the developer and penetrant residue. MPI Test Method and Set Up ▪ Pre-cleaning: The part is first cleaned using cleaner/remover and allowed dry. This removes any dirt, oil, or contaminants that could interfere with testing and inspection. Equipment Verification: Before the test, the light meter readings are verified to ensure there is enough light for visual inspection. The magnetic yoke is tested for electromagnetic strength by determining lifting power of a 10lb steel plate (test bar). First, the workpiece is checked for residual magnetic field with the WFI-10 field indicator. The presence of field is measured at several points. For this test, a residual field of +/- 3 Gauss is considered demagnetized. Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades Any residual magnetic field is removed by demagnetization. This is done by placing the yoke on surface, turning it on and pushing it away from the yoke though external force. This will demagnetize the sample. The magnetic field indicator is again used to verify and ensure that the sample is fully demagnetized. Next, the part is again magnetized by placing the yoke on surface and turning it on. At the same time, magnetic powder is sprinkled on the surface between the legs. Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades The yoke is then turned off and sample is slightly tilted and tapped on the surface to remove extra powder. Next, the legs if the yoke are brought closer. It is turned on and moved across the powdered surface to remove the remaining powder using magnetic field. Finally, the part is observed for any adhering powder left on the surface. This is the indication of possible defects present on or directly below the powdered surface. Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades Calibration and Traceability Certifications Steel Scale (Ruler) Calibration Certificate Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades Light Meter Calibration Certificate Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades MPI Yoke 10 Pound Pull Test Certificate Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades LPI Test Results Indication length: 23mm Max. Allowance: ≤ 6mm Result: FAIL Test Sample: MT 17046 Indication 1 length: 6mm Indication 2 length: 7mm Max. Allowance: ≤ 6mm Max. Allowance: ≤ 6mm PASS FAIL Overall Result: FAIL Test Sample: MT 17048 Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades MPI Test Results Indication 2: 7mm FAIL Indication 1: 6mm PASS Overall Result: FAIL Test Sample: MT 17046 Indication 3 length: 22mm Max. Allowance: ≤ 6mm FAIL Indication 1 length: 5.5mm Max. Allowance: ≤ 6mm Indication 2 length: 7mm Max. Allowance: ≤ 6mm PASS FAIL Overall Result: FAIL Test Sample: MT 17048 Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades Clean Up Developer and Penetrant Removed from Samples Tidy Work Area After the Tests Questions & Discussion Q1) Materials that can and cannot be used with LPI test Liquid penetration inspection cab be used for almost any non-porous material, including steel, iron, aluminum, titanium, copper, brass bronze, as well as rubber, plastics, ceramics and glass. However, LPI is ineffective on porous materials like concrete, wood, paper, porous ceramics and sintered metals. This is because the penetrant would seep into the material, causing false indications and difficulty in detecting actual flaws. Q2) Materials that can and cannot be used with MPI test Typically, ferromagnetic materials are metals, which means all common metallic materials such as iron, cobalt, nickel, steel and alloys of these materials are perfect to conduct magnetic particles inspection. However, the method is not applicable to non-ferromagnetic materials as they cannot be magnetized through current or a permanent magnet. Which means, MPI cannot be used with aluminum, copper, brass, magnesium, and certain stainless steels. Q3) Advantages of LPI and MPI test methods Advantages of LPI ▪ ▪ LPI is highly sensitive, capable of detecting even tiny surface defects like cracks, porosity, leaks, and seams that are not visible to naked eye. LPI is versatile, it is applicable to a wide range of materials including metals (ferromagnetic and nonferromagnetic), plastics, ceramics, rubber and composites. Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades ▪ ▪ LPI utilizes very simple and affordable equipment and offers quick results, making it low-cost nondestructive testing method compared to ultrasonic testing or radiography. LPI is easy to perform compared to other testing methods, requiring minimal training allowing technicians to easily carry out inspections. Advantages of MPI ▪ ▪ ▪ ▪ ▪ Unlike LPI, MPI can detect both surface and near-surface defects including cracks and inclusions. With MPI, there is no strict pre-cleaning requirements. Post-cleaning is also relatively easier compared to other methods. MPI is ideal and quick method for ferromagnetic materials (iron, cobalt, nickel). The inspection provides quick results, making it suitable for high volume productions. MPI makes it easy to inspect complex (irregular) shaped objects, such as, crank shafts, connecting rods and external splines. The equipment used for MPI are portable, allowing easy transportation for on-site inspection of large or complex parts. Q4 Disadvantages of LPI and MPI test methods Disadvantages of LPI ▪ ▪ ▪ ▪ ▪ ▪ LPI is limited to detecting flaws that are open to the surface, it cannot detect internal defects. LPI has strict pre-cleaning requirements. For reliable results, surfaces need to be clean and smooth, free from any dirt, paint, rust, oil or grease. Roughness or poor surface finish of a component can also affect the examination sensitivity. In some cases, surface grinding may be necessary before the test. Materials with porous surfaces (concrete, wood, paper) cannot be examined with LPI. Penetrant and developer need to be compatible with the material being inspected. Post cleaning of parts is necessary, especially if welding operation is to be performed. Proper handling of chemicals is required, fumes produced can be hazardous and flammable without proper ventilation. Disadvantages of MPI ▪ ▪ ▪ MPI only works on ferromagnetic materials. MPI is ineffective on non-ferrous metals like aluminum, copper and brass. Though MPI can reveal near-surface defects, it is ineffective to reveal deeper flaws like ultrasonic testing or radiography. Flaws detection depends on the direction of magnetization. Magnetic field wont leak if discontinuity is parallel to its flow and such flaws won’t be detected. A second examination perpendicular to the first one is necessary, so that flaws in any direction are detected. Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades ▪ ▪ Demagnetizing large components might post challenges after test completion. Paint removal is necessary if the coating is thicker than about 0.005” for MPI to work. Q5) Other international specification that govern LPI and MPI This lab follows ASME Code Section VIII Div. 1 Appendix 7 Paragraph 4C – 2007, to determine defects. Other international standards include, ▪ ▪ ▪ ISO 3059: Non-destructive testing – Penetrant testing and magnetic particle testing – Viewing conditions – 2012 ASTM E165/E165M-18 – Standard practice for liquid penetrant testing – 2018 ASTM E1444/E1444M-22 – Standard practice for magnetic particle testing – 2022 Q6) Level II Canadian Accreditation Requirements for LPI and MPI: Certification Body: Canadian General Standards Board (CGSB) Certification Requirements (Level II): • Education: o • • • • Training Hours: o LPI: Minimum of 40 hours of classroom training. o MPI: Minimum of 40 hours of classroom training. Work Experience: o LPI: 300 hours of practical experience in liquid penetrant testing. o MPI: 400 hours of practical experience in magnetic particle testing. Examination: o Successful completion of a written exam covering both theory and application. o Completion of a practical exam demonstrating proficiency in inspection techniques. Vision Requirements: o • Completion of a relevant technical program or equivalent. Must pass specific vision tests, including color perception. Recertification: o Must recertify every 3 years through continuing education or by retaking exams. Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades Q7) Two other manufacturers/ suppliers of LPI equipment and supplies in addition to Magnaflux ▪ ▪ TED NDT – Chemetall Lambton College of Applied Arts and Technology School of Applied Science Technology and Trades References LPI Intro Better - https://uberspec.com/non-destructive-testing-methods/liquid-penetranttesting/#:~:text=Liquid%20Penetrant%20Inspection%20(LPI)&text=Penetrant%20inspection%20is%20used%20to,cracks %20on%20in%2Dservice%20components. https://www.bindt.org/What-is-NDT/Liquid-penetrantinspection/#:~:text=The%20principle%20of%20liquid%20penetrant,and%20produce%20a%20surface%20indication. MPI Intro, Pros and Cons Q5) https://www.flyability.com/blog/magnetic-particle-inspection https://www.nationalboard.org/index.aspx?pageID=164&ID=377 LPI Steps and Q3) Adv and Dis Adv https://www.nationalboard.org/index.aspx?pageID=164&ID=374 MPI Steps https://www.americanmetaltesting.com/testing-process/magnetic-particle-inspection Q1)https://www.nationalboard.org/index.aspx?pageID=164&ID=374#:~:text=Most%20nonporous%20materials%20(stee l%2C%20stainless,not%20be%20examined%20using%20PT. Q2) https://www.txndt.com/blog/non-destructive-testing-what-materials-can-magnetic-particle-testing-be-usedon#:~:text=Typically%2C%20ferromagnetic%20materials%20are%20metals,candidates%20for%20magnetic%20particle% 20testing. Q3) https://www.onestopndt.com/ndt-articles/liquid-penetrant-testing-advantages-disadvantages https://www.txndt.com/safety-section/magnetic-particle-testing Q5) Penetrant-Testing-and-Magnetic-Particle-Inspection-Specification-Overview.pdf (magnaflux.com) - Martin.pptx (ndtboard.com) https://www.iso.org/standard/56122.html - Best one https://www.astm.org/e1444_e1444m-22a.htm - Best one Q6) https://www.nait.ca/nait/continuing-education/courses/ndtc320-liquid-penetrant-inspection-level-ii https://qcccanada.com/page/liquid-penetrant-level-two Q7) https://www.tedndt.com/products/ndt-equipment/by-method/liquid-penetrant/
