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INCOS primarily performs the classical non-destructive material tests. This includes X-ray, ultrasonic, penetrant, leakage and magnetic powder testing together with visual inspections. Technical modifications of these processes are employed for the testing of special user problems. Mechanised test procedures are thereby used just as much as high-resolution imaging processes.

At this time INCOS performs non-destructive testing mainly in the areas of plant engineering and metal construction as well as in the aviation industry. We provide the following solutions:

Tank inspection
The poor accessibility and the large scope of testing with storage tank inspections require special test methods. INCOS, in cooperation with an accredited testing agency, offers both nearly 100% tank bottom testing with electromagnetic leakage flux method (FIT – Floor Inspection Tool) and also tank wall and tank top testing using a mechanised ultrasonic test system. A test robot equipped with magnetic wheels is used to follow test tracks on the tank wall with a local resolution down to a millimetre. The strong magnetic adherence of the wheels makes additional safeguards unnecessary. Water is used in the coupling process and therefore no residues are left on the surface.

Tank floor scanning permits the quick inspection of the entire tank bottom. Damaged areas are thereby clearly detected even through the coating. A coupling medium is not required.


With both test methods the data is stored digitally, thus allowing the exact determination of progressing corrosion through repeat testing.

Tube-to-tube welding
The weld seam testing of pipes or sheets welded to the pipe plate cannot be satisfactorily accomplished with the customary non-destructive test methods. To still permit arriving at an assessment of this type of welding joint a radiographic test image can be created with the help of a return beam microfocus tube. A rod anode is introduced into the pipe opening and the film to be exposed is applied from the outside on the weld seam. The small focal spot of the microfocus tube (0.2 mm) projects a rather detailed image onto the film. A 160 kV / 0.1 mA microfocus system by Viscom is used for this procedure.

Weld seam inspection
The inspection of weld seams, especially with pressurized components, represents one of the most sensitive tasks of non-destructive testing. Depending on the type and characteristics of the weld joint different test methods, test scopes and assessment standards are used. Radiographic testing, for example, is preferred for thin-walled components whereas ultrasonic testing is often required for thick-walled parts.
Whether radiographic, ultrasonic, magnetic or penetrant testing or visual inspections; whether based on German, European or international rules and regulation, INCOS with its qualified and certified testers covers the entire scope of the test methods required in each case.
A mechanised ultrasonic test system can also be used for the recurrent testing of polished weld seams.

Onstream (testing on plants in operation)
“Onstream” testing refers to the repeated testing of objects (lines, fittings) during the operation of a plant. Critical areas are systematically inspected here for wall thickness losses or corrosion using shadowgraphs (RT), wall thickness measurement (UT) or penetration testing (PT). Potential weak spots or changes between plant stoppages can thus be detected in advance and corrective measures applied accordingly.

Hydrogen damage
The causes for the appearance of HIC (Hydrogen Induced Cracking) are meanwhile largely known. The contact with acid hydrogen sulfide media leads to electrochemical corrosion reactions on the insides of steel tanks. Atomic hydrogen is released in the process and can then penetrate the crystal lattices of the steel and deposit itself on local lattice defects and non-metallic inclusions. There the hydrogen atoms can recombine into molecular gaseous hydrogen. The developing gas pressure is able to burst the structural bond already weakened at these spots. This results in microcracks, which will grow under the operating stresses of the plant over time until one day they reach a critical size. The plant must then be quickly shut down to prevent a forceful rupture.
INCOS offers a manual search with ultrasonic vertical measuring probe for the efficient detection and characterisation of such locations. Areas with discontinuities can then be measured with ultrasound and accurate to the millimetre, using a mechanised procedure. Spots with possible crack formation can then be verified manually with an ultrasonic angle probe.

Corrosion mapping
Especially lines containing hazardous materials buried unsecured in the ground require large surface corrosion testing for reasons of environmental protection. Even small corrosion areas can be reliably detected at a given test grid (e.g. of 5 x 1mm). The uniformity achieved here through mechanised testing cannot be accomplished with manual tests. According to the requirements, only the vulnerable bottom area or the complete line is inspected applying a dense test grid. This approach is practical in areas that cannot be inspected from the inside with the help of a test pig (too angled, sections too short, test diameters too small).
Corrosion mapping is an interesting option of gaining a comprehensive picture of the inside surface also on tanks or lines (prone to pitting) in operation.

Material analyses / PMI (Positive Material Identification)
Material analyses and positive material identification via spectroscopy (refer to the metallography section for more information).

Ultrasonic testing (UT)
Basic principle: Ultrasonic testing represents an acoustic method for the detection of material discontinuities. With this method, a sound pulse is thereby generated by a suitable modulator, and this pulse is transferred into the component via a coupling means. Boundary layers with different acoustic impedances in the test specimen (cracks, doubling, rear wall, etc.) reflect the acoustic pulse and return it to the modulator. It now acts as receiver. The path travelled is calculated through the transit time between sending and receiving (pulse-echo method).
Application: Ultrasonic testing has become a suitable means of testing – for the monitoring of materials capable of conducting sound – for internal and external flaws and inhomogeneities of all kinds. The possible applications range from the monitoring of forging steels and cast pieces, rolled material and semi-finished products and on to weld seam and pipeline testing as well as lamination tests with composite materials. Ultrasound can register almost all sudden transitions of the acoustic impedance. This includes inclusions, cracks, boundary layers, boundary layers between two structural states and pores. Depending on the length and type of wave flaw sizes up to 0.5 mm can still be detected (in classical US testing with test frequencies up to 10 MHz. With ultrasonic microscopy (SAM,)even resolutions up to 0.005 mm are possible.

Radiographic testing (RT)
Basic principle: Radiographic testing is an imaging method for the mapping of material density differences. With this method, the density of the components is imaged onto an X-ray film with the help of a suitable emitter (X-ray tube, isotope). The projected image appears with different densities due to the varying density or thickness of the component. The denser or thicker a part the less radiation can penetrate it. This results in a lesser density of the film.


Application: Radiographic testing is mainly suitable for detecting volume flaws. The greater the difference in density between flaw and basic material the better the detectability. Even fine cracks can be located with suitable incoming beam angles. However, they must largely run parallel to the direction of the incoming beam. The degree of detail detection is hereby affected by contrast and resolution (defocusing, graininess). The contrast, in turn, depends on the thickness of the test specimen, the quality of the beam and the leakage radiation as well as the film type, developing level and density. In practice, the detail detectability is determined with the help of so-called image quality indicators (IQI). They normally consist of wires with different thicknesses. The image quality thereby corresponds to the number of the thinnest wire that can still be recognised on the radiation exposure.

Penetrant testing (PT)
Basic principle: With penetrant testing the capillary forces of fine surface cracks are utilised to exhibit them clearly. A penetrating agent is applied to the part. This penetrating agent has high creeping characteristics and a strong colour contrast to the developer. After a short time the component surface is cleaned temporarily and a developer is applied. The developer is a fine powder, which through the capillary effect of its own cavities draws the penetrating agent from the flaws. The high colour contrast between developer and penetrating agent makes these points very easy to recognize.

Application: Penetrant testing is used to quickly locate surface cracks. Colour and fluorescent penetrating agents are used here. The colour systems (usually red on a white background) require adequate lighting for analysis. With the fluorescent systems the fluorescent effect on a dark background at low ambient brightness can easily be detected using UV light.

Leak testing and leak detection (LT)
Basic principle: Different methods and principles are available for leak testing. On the one hand, the pressure drop of a pressurised system is measured (water pressure test), on the other hand, gases escaping in the process are detected (bubble method, test gas method). Depending on the type of the test medium, detection sensitivities between 0,5 mbar * l * s-1 (water pressure test) and  10-6 mbar * l * s-1 (helium mass spectrometer, vacuum method) can be achieved.


Application: The leak integrity of closed systems must always be seen relatively. The achievable test sensitivity is thus always related to the task and the requirements on leak integrity. The test method itself is limited by the maximum pressure or vacuum that can be applied, the possible physical or chemical detectability of the test gas or the test fluid in the ppm range as well as the available test time. The temperature dependency of some methods is significant; some procedures are quite costly. Surface contamination may significantly affect the test method.  

Magnetic testing (MT)
Basic principle: This method is suitable only for ferromagnetic materials. With this method, Macro-flaws in and immediately below the surface can be made directly visible. The course of the magnetic lines of a magnetic field is interfered with through flaws causing the lines to exit at the surface of the workpiece and aligning applied magnetic powder along the field lines. In order to obtain a good flaw detection probability it is necessary that the longitudinal direction of the flaw lies as perpendicular as possible to the magnetic field lines.

Visual testing (VT)
Visual testing as integral part of non-destructive methods is often required as the first step of NDT. Preliminary inspections can thereby be performed with little technical effort, however, they are always aligned with the subsequent NDT procedures.

Magnetic stray field
Basic principle: The theoretic basis is identical with magnetic powder testing except that in this case an electronic detector is used to locate the exiting field lines. This allows further digital processing of the data.

Mechanised ultrasonic testing
Basic principle: In regard to the ultrasonic principles, mechanised ultrasonic testing does not differ from conventional ultrasonic testing. With this method the test probe is moved through a jig-type apparatus. This allows defined test probe movements to be performed. The ultrasonic data thus produced can be stored locally and utilised for subsequent analysis. Reproducible results are achieved because of the uniform guidance of the test probes. This is particularly important for the repeat testing of defects that are still acceptable.

Microfocus X-ray testing
The microfocus X-ray system is an imaging method for the detailed examination of small structures. A superb resolution is achieved with the small focal spot (approx. 0.2 mm).

X-ray films are used when utilising the microfocus tube for the testing of welded-in pipes.

Otherwise, image intensifiers and digital analysis are used especially with the online radiation of electronic components. The images provide a small overview of the crisp details that can be achieved with this X-ray method.

Eddy current testing (ET)
Basic principle: Time-adjustable magnetic fields are created in an exciting system generating eddy currents in the peripheral zone of an electrically conducting test object. These eddy currents, in turn, create a magnetic field overlaying the energising field. A different overlay is produced in faulty workpieces than in flawless workpieces. As a consequence, flaws can be detected when the overall system was calibrated on a flawless workpiece.

Application: Eddy current testing is widely used for the testing of heat exchanger coils. Different test techniques can be employed according to the material and the flaw expected. Normal eddy current testing (ECT) is best used with non-ferritic materials for the detection of cracks, wall thickness losses and holes. Travel speeds up to 2 m/s can be achieved. With thicker-walled, ferritic components the Remote Field Technique (RFT) is used, which can primarily be used to detect wall thickness losses. The max. operating speed is approx. 0.25 m/s).

Spectral analysis
Basic principle: Spectral analysis is based on the principle that the electrons of a single atom are stable only at certain energy levels. The electrons can be raised to a higher energy level by supplying energy; however, this means an unstable state. When the electrons jump back to the stable state, energy is released again in the form of light or X-ray quantum. The wavelengths of this radiation are characteristic for the respective nucleus and can therefore be used for its determination.


Application: Spectral analysis can be used for the quick material identification in the area of goods receipt as well as after machining for the final control (PMI = Positive Material Identification) of the materials / filler metals used. With this procedure the use of the required materials can be assured, especially with components subject to higher loads/stresses (mainly from alloyed steel). INCOS primarily uses devices by
Spectro (Spectrotest).

Hardness test (HT)
Basic principle: Hardness is the resistance of a material against the penetration of another body. Because the penetration characteristics depend on the type and size of the load, the test method must always be specified when listing hardness values. The hardness value provides an easily verifiable reference value on the static strength and the wear characteristics of the material. The Brinell method uses a ball, the Vickers method a pyramid, the Rockwell-B method a ball and the Rockwell-C method a diamond cone as penetrating body.


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