Industrial Radiography (RT) involves volumetric testing of various metallic and non-metallic components. RT is able to determine surface and subsurface discontinuities, such as cracks, porosities, lack of weld penetration, lack of weld fusion and so on. It can be used for welding, casting as well as forging. A variety of different items can be inspected with RT. It requires a source of radiation, usually gamma rays or X-ray, films or detectors, and developing media, such as chemicals or scanners. It provides a permanent record of the test, and can be evaluated as per the requirements of various codes and customer specifications. RT can be done both, at site as well as in a designated laboratory.
RT can be carried out using the following processes: Iridium (Ir-192), Cobalt (Co-60), Selenium (Se-75), X-Ray, Close Proximity Radiography (CPR), Computerized Radiography (CR), Digital Radiography (DR).
Castings, welding, forgings in aerospace, manufacturing, packaging, military and defence sectors.
Ultrasonic Testing (UT) involves volumetric testing of various metallic and non-metallic components, using Ultrasonic sound waves. UT is able to determine various surface and subsurface discontinuities. It is also able to detect certain defects that cannot be determined by RT, such as laminations. It involves sending ultrasonic waves through the specimen being tested, generating an echo, and determining the location, size and orientation of any discontinuity based on the time required for the detection of the echo. It is a portable means of detection. It may not, however, provide a permanent record of the test.
UT can be further divided into the following methods: conventional UT, Phased Array Ultrasonic Testing (PAUT), Time of Flight Diffraction (TOFD). It is also possible to carry out oxide layer measurement using UT. UT can also be divided into contact UT and immersion UT.
Thickness measurement and defect detection in metals, plastics, ceramics and composites. It can also be used for wood and paper products, but is not accurate.
Magnetic Particle Testing
Magnetic Particle Testing (MT) involves detection of surface and subsurface (upto 5 mm deep) defects in ferromagnetic materials. MT involves magnetization of ferromagnetic components. Once the component is magnetized, magnetic particles can be sprinkled on the component. They align themselves along any defects that may be present on the surface. An important thing to note is that, unless heat treatment is to be carried out after MT, or if any machining work is to be done, the parts must be thoroughly demagnetized. Also, note that testing has to be carried out in two (2) directions 90 o apart so as to have complete coverage of the specimen. MT can be further divided into the following methods: Visible and Fluorescent
Location of surface-breaking and slight subsurface (upto 5 mm) defects in ferromagnetic materials. Extremely useful for defect detection in welded fabrications, castings and parts subjected to fatigue loading.
Liquid Penetrant Testing
Liquid Penetrant Testing (PT) involves detection of surface discontinuities only. It is the preferred method of testing for detection of surface discontinuities, as against RT or UT. PT involves cleaning the component to be examined thoroughly, applying the penetrant, letting the penetrant soak for an amount of time known as dwell time, cleaning the excess penetrant, applying the developer, and looking at any indications that may arise. PT works on the principle of capillary action, and can be done for all types of non-porous materials. PT cannot be done on porous materials such as ceramics.
PT can be further divided into different methods, depending upon the type of penetrant and cleaning agent used. Based on type of penetrant, they are: Fluorescent, colour contrast (visible). Based on cleaning agent, they are: Solvent Removable, Post-Emulsifiable Hydrophilic, Post-Emulsifiable Lipophilic, Water Washable.
Used on any non-porous materials for detection of surface-breaking discontinuities. Materials include glass, all metals, ceramics, plastic, rubber etc. as long as the material is not porous and has good surface finish.
Remote Visual Inspection
Remote Visual Inspection (RVI), involves visual inspection of the components. No special tests are carried out, as the inspection consists of observation by the naked eye. Certain accessories can be used for carrying out inspection, such as flashlights, mirrors, lenses, magnifying glasses, etc.
RVI includes use of remote visual aids such as borescopes and videoscopes. These scopes consist of probes at the ends of optical or digital cables. The probes are inserted into areas which are otherwise inaccessible. They can be scanned and articulated as per requirements. The images seen by the probes are replicated on screens that are held by the operator, which enables the operator to remotely inspect all sorts of components. Additionally facilities for capturing images and recording videos are also available. In some cases, it is possible to livestream the borescope images via Bluetooth or WiFi connectivity to remote locations such as offices.
Useful as a predictive or scheduled maintenance tool to assess the health and operability of assets. Typical uses include aerospace components, oil and gas process piping, power stations and any locations where physical entry is not possible or feasible.
Helium Leak Testing
Helium Leak Testing (LT), involves use of Helium Gas to check for any small leaks or porosities in components. Usually, LT is carried out for pressure vessels and other critical components that contain liquids or gases for storage or use. Helium, being the lightest inert gas, can easily be handled, and be detected in cases of leaks.
LT can be further divided into different methods. They are Vacuum Test (sniffer), Pressure Test (tracer), Bubble Test etc. The testing involves either placing the component inside a vacuum chamber, pressurizing it with helium gas and checking for gas leakage outside the component (inside the chamber). Conversely, it can also involve pressurizing the component, and measuring the pressure drop over time. A detector can be placed so as to detect any leakage of gas. Bubble tests are similar to those used for detecting punctures in vehicle tires, in the sense that they consist of pressurizing the components, applying soap solutions at the seams, and determining any bubbles that may be formed.
Production and manufacturing industries such as refrigeration and air conditioning, automotive parts, aerosols, packaging, valves, steam products, gas bottles, pressure vessels, flange connections, welded seams, seals and heat exchangers.
Positive Material Identification
Positive Material Identification (PMI) involves detection of material composition of various components. Different composition of various alloys and components can be determined by use of radiation guns.
PMI is usually carried out by means of a PMI gun. The laser is focused on the point where the composition is to be checked. It consists of radiation waves (X-Rays) that are bombarded onto the sample. This causes X-Ray fluorescence in the sample being tested. The resulting X-Ray waves that return to the gun are then indicative of the composition of the sample. Since different materials have different fluorescence and spectra, it is possible to determine the material composition of the sample.
Identification of materials used, alloy content, determining material conformity to requirements and standards.
Spark Optical Emission Spectroscopy
Spark Optical Emission Spectroscopy (SOES) is a special type of PMI testing, whereby the carbon content of a sample can also be detected, along with the presence of other elements.
SOES involves applying electrical energy in the form of a spark generated between an electrode and a metal sample. Vapourized atoms are brought into a high energy state within a discharge plasma. These atoms create a unique spectrum specific to each element. The light generated by the discharge is a collection of the spectral lines generated by the elements in the sample. This light is split to extract the emission spectrum of the target elements. The intensity of each spectrum depends upon the concentration of each element in the sample. Detectors measure the intensities of these spectrum to evaluate the composition of the sample.
Identification of materials used, alloy content, determining material conformity to requirements and standards. SOES has the added benefit of being able to determine Carbon content accurately.
Infrared Thermography (IR) involves temperature and gradient detection of components, mostly in the in-service condition. Temperatures of inaccessible and in-service components can be easily and conveniently checked. It also provides a colour-coded gradient indication of the temperatures of various locations of the components, thereby enabling detection of hot spots and high or low temperature areas.
IR involves the use of a temperature gun that sends out infrared rays. These rays are reflected back from the component at frequencies that depend upon the temperatures of the respective areas. These reflected waves are depicted in the form of areas of various colours depending on the temperatures, enabling temperature detection of the component remotely.
Machine condition monitoring, chemical imaging, electrical system monitoring, fluid system monitoring, bearing monitoring, refractory monitoring etc.
Holidays are areas or patches on coated pipelines and components where the coating has been removed due to some reason. Due to the lack of coating, anodic area are formed at those places. This leads to accelerated corrosion and can result in complete loss of material and formation of holes. These holidays may be microscopic in nature, thereby making them difficult and sometimes impossible to spot by the naked eyes. Holidays include discontinuities such as pinholes and voids.
Holiday test, also known as Continuity test, involves checking of an electric circuit to see if current flows to complete the circuit. If an electric flow is detected, the area is termed as conductive, indicating the presence of discontinuities. Holiday tests are performed by the use of holiday detectors, which is an electrical device. Testing can either be a low voltage holiday test, which is carried out for coating thicknesses less than 500 microns, or a high voltage holiday test, which is carried out for thicker coatings. Holiday testing is commonly used in offshore industries and other areas where piping and structures are coated with non-conductive coatings.
Tank interiors, chemical vessels, buried structures and corrosive environments.
Eddy Current Testing
Eddy Current (ET) testing involves use of Eddy Currents to determine flaws in electrically conductive materials. When a coil carrying a current is brought in proximity to a conductive material, eddy currents are set up in the material due to electromagnetic induction. As the coil approaches the component, the magnitude of eddy currents generated in the component increases. Similarly, as the coil moves away, the magnitude reduces. Moving the coil along the component being tested causes eddy currents to be induced along the component. Any defects that may be present, cause the magnitude of eddy currents generated to vary. This variation in magnitude can be checked in order to determine the type, size and orientation of the defects. Eddy currents are developed in a direction perpendicular to the direction of the coil.
Different types of probes can be used for different applications. These include straight probes or surface probes, which are used to detect flat surfaces, or components of geometrical shapes, encircling probes, which consist of coils that completely encircle the component, central conductors, which consists of probes that are inserted inside the tubes, and so on. Each of these probes can be used for a variety of applications, provided sufficient fill factors are achieved.
Heat exchanger tubes, condenser tubes, wires, material sorting, weld inspection, coating thickness measurement.
Internal Rotary Inspection System
Internal Rotary Inspection System (IRIS) is a special type of Ultrasonic Testing technique used for inspection of pipes and tubes. Water is used as a couplant. The tube to be inspected is flooded with water. A transducer generates an electronic pulse parallel to the axis of the tube being tested. A rotating mirror directs the ultrasonic wave into the tube wall. The mirror is powered by a water-driven turbine, with the water being pumped into the tube for flooding.
Parts of the waves are reflected by the ID and OD. Knowing the velocity of ultrasonic waves in the material of the tubes, the wall thickness can be calculated by determining the time required for both waves to be reflected from the corresponding walls. As the probe is pulled, the rotating mirror develops a helical scan path. IRIS can be used for boiler, shell-and-tube and fin-fan heat exchangers.
Metal pipes and tubes in boilers, heat exchangers and fin-fan tubes. It can also be used as a backup for remote field examination.
Remote Field Eddy-Current Testing
Remote Field Eddy-Current Testing (RFET) is a special type of Eddy Current Testing that uses low-frequency Alternating Current to determine both internal and external defects on pipes and tubes with equal sensitivity. It is, however, unable to distinguish between the two.
An RFET probe consists of an exciter or transmitter coil that sends a signal to the detector or receiver coil. The exciter coil is pumped with an AC current and emits a magnetic field. The field travels outwards from the exciter coil, through the pipe wall, and along the pipe. The detector is placed inside the pipe two to three pipe diameters away from the exciter and detects the magnetic field that has travelled back in from the outside of the pipe wall (for a total of two through-wall transits). In areas of metal loss, the field arrives at the detector with a faster travel time (greater phase) and greater signal strength (amplitude) due to the reduced path through the steel. Hence the dominant mechanism of RFT is through-transmission.
Examination of boilers, heat exchangers, cast iron pipes and pipelines.
Computerized and Digital Radiography
Computerized (CR) and Digital (DR) are modern types of Radiographic Testing. CR makes the use of a Phosphor Imaging Plate to obtain a digital image. CR uses a cassette based system like conventional film radiography, and can be considered to be a bridge between conventional film radiography and digital radiography. Certain advantages include low initial investment and the availability of various sizes enabling flexibility.
DR uses a Digital X-ray detector to automatically acquire images and transfer them to a computer for viewing. It is capable of fixed or mobile use. Certain advantages include faster image capture, better quality images and high volume capacity.
Useful where digital images of components are required, especially to save storage space and ease of handling. Also useful where ease of processing and viewing is necessary.
Film Digitization involves the use of high resolution digitization systems for handling of radiographic films. Digitization converts conventional films into digital images that can then be handled on laptops and computers for viewing and storage. Films are scanned through the digitiser and images are obtained on the computer screen.
Different types of scanners are available, making use of different principles. The system works similar to document scanning in office use digital scanners.
Useful where digital images of components are required, especially to save storage space and ease of handling. Differs from CR and DR in that images can only be scanned and digitized, but cannot be processed after digitization.
Pre and Post-Weld Heat Treatment and Stress Relieving
Pre-welding heat treatment involves heating the joints to be welded to specified temperatures before welding can be carried out. Likewise, post-welding heat treatment involves heating the weldment to specified temperatures to allow for gradual cooling and minimization of stresses. Stress relieving is based on the same principle, to relieve any external and internal inherent stresses before a component is put into service
Heat treatment and stress relieving can be carried out in a variety of ways. Electrical Resistance Treatment makes use of the principle that as current is passed through a metal, the resistance of the metal to the current flow causes an increase in its temperature. This increase further causes an increase in resistance, thereby requiring more current for penetration. Various temperatures can be achieved by gradually increasing the currents and based on the material being treated. Electrical Resistance Treatment can be done by using 80V, which is safer but more expensive, or 220V, which is comparatively cheaper. It consists of electrical coils that are wound around the parts to be treated. Current is passed through the coils, which causes the corresponding increase in temperature.
Another type of treatment is the Induction Treatment. This is based upon mutual induction, where electric currents are induced in metals via induction coils. These induced currents cause an increase in temperature.
A third type of heat treatment makes use of high velocity, oil-fired burners. These burners can be placed on the outside or inside the components, and fired at high velocities. The flame and resultant exhaust gases cause heating of the component, thereby enabling heat treatment. Damper and flow control can be used to ensure even and proper heating of the entire components.
Pre- and post-welding treatment for control of properties, stresses and distortion. Also used for stress relieving after welding to reduce internal stresses.
Hardness Testing involves measurement of surface hardness of a component. Surface hardness is the resistance to surface penetration. Hardness of a component depends upon the material composition, process it has undergone and heat treatment.
Hardness testing can be carried out to measure the Brinell and Rockwell hardness numbers. Brinell hardness testing is used for materials that are too coarse or too rough for other methods. A predetermined test load is applied to a carbide ball of a known diameter for a predetermined period of time. The size of the indentation is measured, which is compared with a Brinell chart to get the corresponding Brinell Hardness number (BHN). Rockwell hardness testing is used for almost all materials, except where too much variation may be introduced or size and shape of the component prevents the use. A pre-load is applied to the sample using a diamond or ball indenter. This breaks through any surface film that may be present. A baseline indentation depth is then measured. A main load is then applied, and held for a predetermined dwell time before being released. The pre-load is continued to be held for a further dwell time, and the depth of the indentation is measured again. The difference between the two depths is then converted to the Rockwell Hardness number (HR). The load and indenter are then removed.
To ensure surface hardness of given materials/components is as per requirements, so as to ensure required properties are achieved and that proper heat treatment is carried out. Can also be used to determine future heat treatment and processes that may need to be carried out.
Welding inspection involves inspection of various aspects of a weld. Inspection can be carried out before, during and after the completion of the weld. Such inspections include joint preparation, procedure verification, settings, methods used, inter-pass inspection, depth of penetration, inter-pass and base metal fusion and so on.
Welding inspection can be carried out visually, as well as using NDE techniques of RT and UT. Welding inspection is usually carried out based on procedures and methods as per the requirements of various standards such as ISO, ASME and AWS.
Examination of welds and weld quality to ensure welds conform to required standards. Inspection of weld before, during and after welding process is completed, so as to ensure properties and quality of weld is maintained throughout.
Residual Life Assessment
Residual Life Assessment (RLA) involves determination of the remaining time during which the fit-for-service characteristics of the plant or equipment will be maintained. It determines the time up to which the component will work successfully without breakdowns, faults or leaks, from the present.
RLA is important in order to maintain efficient operation of a process plant unit and avoid failures of critical equipment which would lead to increased downtime and may cause a safety hazard. RLA can be carried out on pressure vessels, piping, storage tanks, valves, pumps, compressors, boilers, turbines and other such equipment that operates under harsh conditions of high temperatures and pressures.
Power plant components such as boilers, heat exchangers, headers, condensers, feed water heaters, turbines and steam lines.
Fugitive Emission Testing
Fugitive Emissions are emissions of gases or vapours from pressurized equipment due to leaks, and other unintended or irregular leaks of gases, mostly from industrial activities. Along with the economic costs, fugitive emissions contribute to air pollution and also pose health and safety hazards.
Fugitive Emission testing is a special type of Helium Leak testing that is carried out for valves, flanges, gaskets and fittings. These components can be tested at different temperatures or over a range of temperatures, with helium or methane gas, using the sniffer or vacuum method. Any leaks present at different temperatures can be detected.
Valves and associated components such as gaskets, seats, fittings and flanges, especially those used in critical applications where any leaks may be detrimental.
In-situ metallography is used to determine in-service degradation of critical components of process and plants operating under high temperature, high-pressure and corrosive atmospheres. This technique enables real-time component condition monitoring and health assessments.
In-situ Metallography and replication is used for microstructural analysis while examining large components that cannot be easily moved or when destructive sample preparation is difficult or not permissible. The testing allows quick on-site evaluation of a component’s metallurgical and heat treatment condition and assists investigators in carrying out a remaining life assessment study or a failure analysis project.
Critical components of process plants operating under high temperature, pressure and corrosive atmospheres. Undertake microstructure surveys for critical components such as boilers, pipelines, reactors and vessels for condition monitoring and health assessment. Checking the quality of components before putting into use and conducting a damage assessment.
Corrosion Under Insulation
Corrosion Under Insulation (CUI) is any type of corrosion that occurs due to moisture present on the external surface of insulated equipment. The damage/attack can be caused by one of multiple factors, and can occur in equipment operating at ambient, low, and heated services, depending upon conditions. Moreover, CUI can occur in equipment that is in service, out of service, or in cyclic service. The corrosion itself is most commonly galvanic, chloride, acidic, or alkaline corrosion. If undetected, the results of CUI can lead to leaks and the shutdown of a process unit or an entire facility.
CUI can be inspected by means of special equipment making use of Eddy Current Testing, using the LYFT technique. It enables detection of, and determination of extent of, corrosion under insulations without removing any insulation.
In-service pipelines, piping, pressure vessels, all insulated components.
Grain Size Measurement
Grain Size Measurement is useful in metallurgy, to determine the grain sizes in various materials. Grain sizes depend upon a lot of factors such as heat treatment, alloy conditions, working conditions etc. Grain size measurement is useful mostly during and after manufacturing and heat treatment, so as to ensure proper working and treatment has been carried out.
Grain sizes can be measured by means of Ultrasonic Testing. Sound waves are reflected off the various grain boundaries. Depending upon the number and size of grains, the reflections and diffractions of the sound waves can be measured, thereby giving an indication of the number and size of grains present in the material. Grain size is then calculated as per various standards.
Microstructure measurement, quality of heat treatment, both desired and attained, thermal stress determination, temperature variation measurement.
Velocity Measurement is a special application of Ultrasonic Testing, which is used to determine the acoustic velocity of various materials. Different materials have different acoustic velocities, depending upon their constitution. As the constituents, and their individual concentration within a material varies, its acoustic velocity also varies. Measurement of acoustic velocity provides ideas about the elastic properties and thermodynamic properties such as density, isothermal compressibility and heat capacity.
The equipment is first calibrated by measuring the thickness of a material of known thickness and velocity, such as standard steel calibration blocks. The corresponding measurements are noted and echoes are calibrated. Once calibration is completed, a material of known thickness, whose velocity is to be determined is scanned. This thickness should preferably be equal to the calibration block thickness. The system would then provide echoes based on the thickness and velocity of the material, in terms of steel equivalent (or equivalent to that of the material used for calibration). If the thicknesses are same, the velocity of the material would be inversely proportional to the difference in thicknesses indicated. For a material with a lower velocity, a higher thickness would be indicated since the sound waves have to travel for a greater amount of time before generating an echo. Similarly, if the velocity is higher, a lower thickness would be indicated. The ratio of the indicated thickness and the actual thickness would be inversely proportional to the ratio of the sample and the calibrated thicknesses. Thus, velocity of the sample can be found out. If the sample thickness is not same as the calibration block, additional factor depending on the thickness would have to be considered.
While this technique may be used to determine velocity of all materials, solid and liquid, any liquid with a specific gravity greater than that of water may require an additional liquid, with a known velocity, having a specific gravity greater than that of the liquid to be measured, so as to generate a good echo
Determination of acoustic velocities of solids such as metals and non-metals, and liquids such as organic oils, in order to determine elastic and thermodynamic properties.
Carbon in the form of graphite is often used as an additive in the production of cast iron, amounting to 2 to 4 percent by weight or 6 to 10 percent by volume in typical castings. The microstructure of graphite within cast iron has major effects on the casting’s mechanical properties. When graphite arranges itself as thin flakes the result is grey iron, which is hard and brittle. When graphite takes the form of spherical nodules the result is nodular iron, which is soft and malleable.
Both grey and nodular iron are made by mixing carbon, silicon, and other additives into molten iron, and often part of the mixing is done in the final mold. If the mixing is non-uniform or the casting process is otherwise imperfect, it is possible to make a casting with variations in nodularity, or pockets of grey iron within a nodular iron casting. Because this will significantly change the mechanical properties of the metal, foundries need to check nodular iron for uniformity. It is important that both the distribution of graphite in the casting be uniform, and that graphite inclusions be of the right form (nodules rather than flakes).
Microscopic examination and tensile strength tests are effective for checking nodularity, but for quick and non-destructive evaluation of a casting the preferred method is ultrasonic testing based on the fact that nodular iron and grey iron have different sound velocities.
Measuring the degree of nodularity in cast iron, or distinguishing nodular iron from grey iron.
Pressure Distribution Measurement
Pressure Distribution Measurement involves measurement of pressure applied by a component over an area, and determination of whether the pressure is as required. Pressure application is important in various press-fit and other such components. It is also important in various assemblies. Pressure applied by each component, and its distribution over the surface can be determined.
Measurement is carried out by use of a special film – PRESCALE. A pressure inspection sensor on the entirety of the film allows confirmation of pressure distribution of the entire surface at a glance. The colour appears red where pressure is applied, and the colour density varies according to the amount of pressure. The microcapsules in the colour-forming layer are broken by pressure, and the colourless dye is absorbed into the developer, causing a chemical reaction to produce a red colour. The microcapsules containing the colour-forming material are adjusted to varying sizes and strengths, and is coated uniformly, producing a colour density that corresponds to the amount of pressure.
Nip pressure, lamination pressure, winding pressure, contact pressure, tightening pressure, compression pressure, support pressure, impact pressure, contact conditions.
- Trainings for various NDT and Inspection methods is also provided by us. Trainings provided include:
- ASNT Level III (RT, UT, MT, PT, VT, LT, ET, IR)
- EN 473 / ISO 9712 Level III (RT, UT, MT, PT, VT)
- CSWIP 3.1 – Welding Inspector
- API 653 – Authorized Tank Inspector
- API 510 – Authorized Pressure Vessel Inspector
- API 570 – Authorized Process Piping Inspector
- API 571 – Degradation Mechanisms in Refining Industry
- API 580 – Risk Based Inspection
- API SI – Source Inspector
- Atomic Energy Regulatory Board (AERB), India – eLORA platform consultation for approval and training