Introduction & Basic Principle

When magnetism applied through ferromagnetic materials by using electrically or by using permanent magnet, magnetic poles of leakage field will occur at discontinuities. Magnetic powders applied throughout the object to see such leakage field as discontinuity indication.

Application

Magnetic particle testing is a relatively simple test method that can be applied to finished articles, billets, hot rolled bars, castings, and forgings. It can also be used to check that the processing operations such as heat treat, machining, and grinding did not uncover or cause discontinuities. Magnetic particle consists of magnetization of the article, application of the particles, and interpretation of the patterns formed by the particles as they are attracted by magnetic leakage fields.

Advantages

Magnetic Particle Testing is one of most economical method to find out surface cracks in ferromagnetic materials. It is portable and easy for application.

Limitation

It is limited application to only on ferromagnetic materials. Further it is limited to disclosing only those discontinues that are at or near the surface.

Introduction & Basic Principle

LPI is based upon capillary action, where low surface tension fluid penetrates into clean and dry surface-breaking discontinuities. Penetrant may be applied to the test component by dipping, spraying, or brushing. After adequate penetration time has been allowed, the excess penetrant is removed, and a developer is applied. The developer helps to draw penetrant out of the flaw where a visible indication becomes visible to the inspector. Inspection is performed under ultraviolet or white light, depending upon the type of dye used – fluorescent or nonfluorescent (visible).

Liquid penetrant inspection is a widely applied and low-cost inspection method used to locate surface-breaking defects in all non-porous materials (metals, plastics, or ceramics). Penetrant may be applied to all non-ferrous materials, but for inspection of ferrous components magnetic particle inspection is preferred for its subsurface detection capability. LPI is used to detect casting and forging defects, cracks, and leaks in new products, and fatigue cracks on in-service components.

Application

Liquid penetrant inspection (LPI) is one of the most widely used nondestructive evaluation (NDE) methods. Its popularity can be attributed to two main factors: its relative ease of use and its flexibility. LPI can be used to inspect almost any material provided that its surface is not extremely rough or porous. Materials that are commonly inspected using LPI include the following:

1. Metals (aluminum, copper, steel, titanium, etc.)
2. Glass
3. Many ceramic materials
4. Rubber
5. Plastics

LPI offers flexibility in performing inspections because it can be applied in a large variety of applications ranging from automotive spark plugs to critical aircraft components. Penetrant material can be applied with a spray can or a cotton swab to inspect for flaws known to occur in a specific area or it can be applied by dipping or spraying to quickly inspect large areas. Above, visible dye penetrant being locally applied to a highly loaded connecting point to check for fatigue cracking.

Penetrant inspection systems have been developed to inspect some very large components. In the image shown right, DC-10 banjo fittings are being moved into a penetrant inspection system at what used to be the Douglas Aircraft Company’s Long Beach, California facility. These large machined aluminum forgings are used to support the number three engine in the tail of a DC-10 aircraft.

Liquid penetrant inspection is used to inspect for flaws that break the surface of the sample. Some of these flaws are listed below:

1. Fatigue cracks
2. Quench cracks
3. Grinding cracks
4. Overload and impact fractures
5. Porosity
6. Laps
7. Seams
8. Pin holes in welds
9. Lack of fusion or braising along the edge of the bond line

As mentioned above, one of the major limitations of a penetrant inspection is that flaws must be open to the surface. To learn more about the advantages and disadvantages of LPI, proceed to the next page.

Primary Advantages

1. The method has high sensitivity to small surface discontinuities.
2. The method has few material limitations, i.e. metallic and nonmetallic, magnetic and nonmagnetic, and conductive and nonconductive materials may be inspected.
3. Large areas and large volumes of parts/materials can be inspected rapidly and at low cost.
4. Parts with complex geometric shapes are routinely inspected.
5. Indications are produced directly on the surface of the part and constitute a visual representation of the flaw.
6. Aerosol spray cans make penetrant materials very portable.
7. Penetrant materials and associated equipment are relatively inexpensive.

Primary Disadvantages

1. Only surface breaking defects can be detected.
2. Only materials with a relatively nonporous surface can be inspected.
3. Precleaning is critical since contaminants can mask defects.
4. Metal smearing from machining, grinding, and grit or vapor blasting must be removed prior to LPI.
5. The inspector must have direct access to the surface being inspected.
6. Surface finish and roughness can affect inspection sensitivity.
7. Multiple process operations must be performed and controlled.
8. Post cleaning of acceptable parts or materials is required.
9. Chemical handling and proper disposal is required.

Introduction & Basic Principle

Ultrasonics is the name given to the study and application of sound waves having frequencies higher than those which the human ear can hear. Adults with normal hearing can hear frequencies up to a range of 16,000 cycles per second (16 kHz) to 20,000 cycles per second (20 kHz). Ultrasonic nondestruc­tive testing is the use of ultrasonics to examine, or test, material without destroying the material.

Application

An ultrasonic test may be used to measure the thick­ness of a material or to examine the internal structure of a material for possi­ble discontinuities such as voids and/or cracks. Because of the basic characteristics of ultrasonic testing, it is used to test a variety of both metallic and nonmetallic products such as welds, forgings, castings, sheet, tubing, plastics, and ceramics etc. since ultrasonic testing is capable of economically revealing subsurface discontinuities (variations in material composition) in a variety of dissimilar materials, it is one of the most effective tools available to quality assurance personnel.

Introduction & Basic Principle

Radiographic testing is working on the principle of penetration and absorption capabilities of X and gamma radiation. Radiography is used to test a variety of non-metallic products and metallic products such as welds, castings, forgings, and fabrications. Since it is capable of revealing discontinuities (variations in material composition, or density) in a variety of dissimilar materials, radiographic testing is one of the primary nondestructive test methods in use today. Radiographic testing usually requires exposing film to X rays or gamma rays that have penetrated a specimen, processing the exposed film, and interpreting the resultant radiograph.

For radiographic testing there are two electromagnetic radiation sources are available. One is X ray and another one is gamma ray. Throughout the spectrum, X rays and gamma rays have the same characteristics, and X rays and gamma rays of the same wavelength have identical properties.

Advanages

Radiographic Testing is most often used for process control during manufacturing, to detect subsurface discontinues in end products such as castings, welds, ceramics and composite materials and electronic components. RT is applied in building and bridge construction, aircraft aviation and aerospace, automotive and space components manufacturing, and aircraft overhaul, maintenance and repair. It is also used for inspecting piping and pipelines, refinery vessels, steel pressure vessels and storage tanks.

Limitations

The major limitations of RT are that the opposing sides of the test object must be accessible, precautions to prevent personnel exposure to radiation are required and configuration of the object must allow for satisfactory formation of shadows of its internal structure.

Introduction & Basic Principle

Closed Proximity (or) Small Controlled Area Radiography is the concept of controlling the radiation utilized for RT allowing for radiographic inspection without restrictive shooting windows (24/7 radiography concept) enhancing radiation safety for the Radiographer and public from exposure to harmful Radiation levels. Radiography can be performed in Close Proximity to other trades such as welders, fitters etc, rather than clearing the area for Radiography.

Applications

• Offshore Platforms, Onshore plants.
• During Plant Shutdown and Turnarounds
• Locations where RT inspections must not affect nuclear gauges and plant safety systems

Introduction & Basic Principle

Positive Material Identification (PMI) testing is the analysis of materials to determine the chemical composition of a metal. It is intended to ensure that the nominal composition of the alloy components and associated welds have been correctly supplied and installed as per the specification, thus minimizing the risk of component failure and release of hazardous/toxic liquids and vapors

ITC offers PMI Services by using of :

1. Handheld XRF PMI Analyzer
2. Portable Optical Emission Spectrograph : SpectroTEST
3. Light weight Portable PMI SMRT of OXFORD
4. Handheld Laser Induced Breakdown Spectroscopy (LIBS) alloy Analyzer; SciAps

Applications

Pressure-retaining alloy material components, flange bolting, welds, pipes, structural steel works, fittings, weld overlays and cladding etc

Introduction & Basic Principle

Ferrite (iron) content analysis is a testing method to determine the FE % (or) FE number of Austenitic Stainless Steel and Duplex materials. Ferrite content provides a balance between ductility, toughness, corrosion resistance and crack prevention. When ferrite content is too high, stainless steel can lose ductility, toughness, and corrosion resistance – especially at high temperatures. If ferrite content is too low, stainless steel welds become susceptible to hot cracking or solidification cracks

ITC offers on-site ferrite measurement by using of FMP 30 of Ferritscope to ensure the Ferrite contents are within the acceptable range of Standards and Specifications.

Applications

Pressure-retaining alloy material components, flange bolting, welds, pipes, structural steel works, fittings, weld overlays and cladding etc

Introduction & Basic Principle

Hardness is a characteristic of a solid material expressing its resistance to permanent deformation, penetration, bending, cutting, scratching or other physical force. Hardness testing enables to evaluate a material’s properties, such as strength, ductility and wear resistance and helps to determine whether a material is suitable for the purpose required.

ITC offers on-site Hardness Testing by Portable Hardness Testes : a) Telebrinnel Hardness Tester, b) MIC 10 (UCI Method) of Krautkramer, GE &,c) Equotip of Proceq to ensure the Hardness Values are within the acceptable range of Standards and Specifications.

Applications

Introduction & Basic Principle

PWHT reduces or redistributes the residual stress introduced by the welding process with a technique that involves heating, soaking and cooling the weldment/machined surface to controlled temperatures. This improves the properties of the weldment/machined surface.

Benefits of PWHT