Step-by-Step: Liquid Penetrant Inspection
- Pre-clean surface. The metal surface must be free of all contaminants that could prevent penetrant from seeping into defects.
- Apply penetrant and wait. Whether the penetrant is brushed or sprayed on—or the component is dipped into it—any cracks in the metal surface will “pull” penetrant inside during “dwell time.
- Clean surface of excess penetrant. ...
- Apply developer. ...
- Assess results. ...
Full Answer
What is the liquid penetrant testing procedure?
The liquid penetrant testing procedure works by applying a penetrant to a nonporous surface and using a specific testing method to determine if excess penetrant reveals a defect in the material. The first step in a liquid penetrant inspection is to clean the entire surface of the material you will be testing.
What is dye penetrant testing (DP)?
Dye penetrant testing (DP). The ASNT considers the name as liquid penetrant testing (LPT)ASME B & PVC) and the NBIC ( National Board Inspection Code) call it liquid penetrant examination (LPE) but the term is same as PT in both ASNT and ASME. The dye penetrant solvent removable method is most popular because it is low cost and very versatile.
What types of surfaces can be inspected for liquid penetration?
Only clean, smooth surfaces can be inspected. (Rust, dirt, paint, oil and grease must be removed.) Metal smearing from power wire brushing, shot blasting, or grit blasting must be removed prior to liquid penetrant examination Examiner must have direct access to surface being examined
What is penetrant testing or DPT?
What is Penetrant Testing or DPT? What is Penetrant Testing or DPT? Liquid penetrant testing (LPT) or also known as Dye penetrant test (DPT) is one of the most popular Nondestructive Testing (NDT) methods.
What is liquid penetrant testing?
Liquid penetrant testing is a versatile nondestructive test method used for the detection of OPEN TO SURFACE DISCONTINUITIES in a wide variety of solid, non-porous materials. This method is also known as dye penetration testing. It is economical, versatile, and requires minimal training when compared to other NDE methods. It basically involves the application of Penetrant on the testing surface, allowing it on the test surface for a period of time and application of the developer after cleaning the Penetrant completely from the test surface. The test results indicating the presence of Discontinuities not visible by unaided human eyes.
How long should a penetrant stay on a test surface?
Note: Penetrant should not remain on the test surface for a long period of time such that it dries on the test surface.
What happens when you clean off excess penetrant?
After cleaning off excess Penetrant from the surface, only the Penetrant in the discontinuities remains. Reverse capillary action causes the penetrant to bleed back out from discontinuities’ forming a penetrant indication. In order to aid the reverse capillary action, a contrasting developer is used which makes indications easier to see.
Why is it necessary to post clean a test object?
Once the test indications are interpreted and evaluated it is necessary to post clean the test object immediately because penetrants contain chemicals that can harm test object surface if stays on test surface for a long period of time. Precleaning methods can also be used for post-cleaning.
When should the developer be applied to the test surface?
Once dwell time is completed the excess penetrant should be removed and the developer should be applied on the test surface.
How many candles are needed for a visible test?
The illumination for the visible test method is 100-foot candles (fc).
What materials are used to test discontinuities?
The testing surface must be free from foreign materials like dust, dirt, rust or paints that will block the open discontinuities. Methods: Using solvents, detergents, vapor degreasing, ultrasounds, chemical and paint strippers.
What Is Liquid Penetrant Testing?
Liquid or Dye penetrant testing is an NDT method used when discontinuities are indetectable to the naked eye. In cases like these, visual testing is not enough to detect a flaw and more extensive measures must be taken.
How to Use LPT
There are a number of different circumstances in which liquid penetrant testing is the best choice.
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To identify a flaw quickly and efficiently, an NDT technician must be skilled and experienced. A great technician starts with a great school. Regardless of what method is used, all forms of nondestructive testing are useless in the hands of an unskilled or inexperienced technician.
What is liquid penetrant test?
Liquid penetrant examination is one of the most popular Nondestructive Examination (NDE) methods in the industry. It is economical, versatile, and requires minimal training when compared to other NDE methods. Liquid penetrant exams check for material flaws open to the surface by flowing very thin liquid into the flaw and then drawing the liquid out with a chalk-like developer. Welds are the most common item inspected, but plate, bars, pipes, castings, and forgings are also commonly inspected using liquid penetrant examination.
What are the advantages and disadvantages of liquid penetrant examination?
Few material limitations (metallic and nonmetallic, magnetic and nonmagnetic, and conductive and nonconductive can all be inspected) A visual representation of the flaw are indicated directly on the part surface.
How many steps are there in the dye penetrant method?
There are six basic steps to follow when using the dye penetrant solvent removable method.
How much does a dye penetrant solvent cost?
The cans can be purchased from welding supply distributors for typically $5 to $15 a can.
How long does it take for a penetrant to dry?
This is typically 5 to 30 minutes but should never be long enough for the penetrant to dry. The penetrant manufacturer’s recommendations and written procedure should be followed. Remove penetrant. All penetrant should be removed with clean, dry, lint-free rags until thoroughly clean.
What is PT testing?
The American Society for Nondestructive Testing (ASNT) uses the name liquid penetrant testing (PT). The American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME B & PVC) and the National Board Inspection Code (NBIC) use the name liquid penetrant examination (PT). The first documented use of PT was in the railroad industry.
What are the two types of penetrants?
The two penetrant types are either fluorescent or color contrast (dye) penetrant. They can then be used with any of the three methods of cleaning – water washable, post-emulsifying, and solvent removable. The most popular is dye penetrant that is solvent removable. This method is referenced throughout the article.
When was liquid penetrant testing first used?
The liquid penetrant method of nondestructive testing has been used since the 1940’s. But even after being used by generations of NDT professionals, there are still some common areas of confusion or misunderstanding.
What is required for a penetrant inspection?
Tanks and an inspection booth are required for penetrant inspection. Penetrant inspection is easy to adapt to different environments and job sites. Penetrant inspection systems with stationary tanks and booths are commonly seen in production environments.
What is a water washable penetrant?
Water-washable penetrants contain surfactants which allow the penetrant to be easily removed from the part surface with water rinsing, regardless of if they are water-based or oil-based. 4. Penetrants are only used on nonferrous metals. Penetrants can be used to inspect ferrous and nonferrous metals.
What can penetrants be used for?
Penetrants can be used to inspect ferrous and nonferrous metals.
What is the best penetrant for an application?
The best penetrant for an application is the one that finds the right indications with the least amount of money and time. Sometimes this means not using the highest sensitivity penetrant.
When should penetrant inspection be done?
Penetrant inspection should take place before machining operations like shot blasting, peening or grinding unless chemical etching can be used between these operations and the penetrant testing to reliably expose the discontinuities.
Why do we need a penetration inspection?
Penetrant inspection is useful immediately after any manufacturing process which is known to cause discontinuities. This allows parts to be reworked or discarded earlier in the manufacturing process, which saves time and cost.
What is the most important step in liquid penetrant inspection?
Surface Preparation: One of the most critical steps of a liquid penetrant inspection is the surface preparation . The surface must be free of oil, grease, water, or other contaminants that may prevent penetrant from entering flaws. The sample may also require etching if mechanical operations such as machining, sanding, or grit blasting have been performed. These and other mechanical operations can smear metal over the flaw opening and prevent the penetrant from entering.
How to apply penetrant material?
Penetrant Application: Once the surface has been thoroughly cleaned and dried, the penetrant material is applied by spraying, brushing, or immersing the part in a penetrant bath.
What is the most delicate part of inspection?
Excess Penetrant Removal: This is the most delicate part of the inspection procedure because the excess penetrant must be removed from the surface of the sample while removing as little penetrant as possible from defects. Depending on the penetrant system used, this step may involve cleaning with a solvent, direct rinsing with water, or first treating the part with an emulsifier and then rinsing with water.
What is a bath penetrant?
Penetrant - A fluid (usually a liquid but can be a gas) which possesses unique properties that render it highly capable of entering small openings, a characteristic which makes this fluid especially suitable for use in the detection of surface discontinuities which may be present . Dwell: The penetrant.
What is the minimum dwell time for a material inspection?
being inspected for. Minimum dwell times typically range from five to 60 minutes.
