Radiography is the most common and well-known method of non-destructive methods (control without destruction). It can be used to obtain a permanent image of surface and sub-surface (embedded) discontinuities (errors) in welded elements, castings and forgings, wall thickness measurement, corrosion mapping, detection of clogging in closed equipment, detection of reinforcement in concrete slabs, measurement of material densities, measurement of porosity in concrete, etc.
Radiography is the most sensitive test method in non-destructive testing, and radiographic images can be stored and compared to monitor the condition of the test object.
Ultrasonic control of materials is a control that obtains the characteristics of the material without destroying it. The test is based on the fact that solid materials are good conductors of sound waves. When they pass through, sound waves are reflected at the material boundary, and this phenomenon was used to test the material. Reflection occurs not only at the outer boundaries of the material, but also when the sound wave encounters internal irregularities in the material.
Thanks to such properties, it is possible to test for defects in the interior of the material.
CONTROL WITH MAGNETIC PARTICLES
The magnetic quality control method is used to detect surface and sub-surface defects (up to a depth of approximately 6 mm) in ferromagnetic materials.
This quality control method is cheap and fast, but has limitations with respect to non-ferromagnetic materials, defects deep below the surface, and the inability to determine the depth of a crack that is detected in ferromagnetic materials.
CONTROL WITH LIQUID PENETRANTS
Inspection with liquid penetrants is used to detect surface and sub-surface defects, in order to determine the dimensions and other characteristics of the defects. Liquid penetrant testing is not applied to welded joints of welded products for the food industry, as well as to welded joints where there is a tendency to corrosion (especially stress corrosion). The disadvantages of this method are the high dependence of the quality of the error finding on the method of preparation and the condition of the tested surface, its usability only in a limited temperature range, and its unsuitability for outdoor application without protection from the atmosphere.
Visual inspection is applied before any other method of welding inspection.
This method of control is relatively cheap, does not take much time, and can provide very useful information both about the quality of welded joints and about the need for control by another method.
To help with visual control in narrow and inaccessible parts of the structure, various magnifiers - magnifiers with lighting are used.
CONTROL OF ANTI-CORROSION PROTECTION
Controlling the thickness of the dry layer of each coating is a very important parameter for determining the quality of protection of metal surfaces. The corrosion resistance of most coatings increases with an increase in coating thickness, but production costs also increase, so reliable knowledge of the minimum coating thickness value is necessary for economic reasons.
Leakage controlwelded joints. One of the controls for the tightness of welded joints is the vacuum technique, which is based on the change in pressure in the area of the tested weld. The procedure consists in soaking the tested area with the appropriate chemical, and by creating a vacuum in the test chambers, bubbles appear in the permeable places.
ADVANTAGES OF THE VACUUM METHOD:
– precise location of the leakage point
- technical simplicity of application and accessibility to the tested objects
Application of the vacuum method is possible in refineries (reservoirs), shipyards, ind. drives etc.
CONTROL OF ELECTRICAL BREAKTHROUGH OF INSULATION
By checking the electrical penetration of the insulation, it is established whether the insulation adheres well to the fuel tanks, gas or fuel pipelines, so that sparks do not occur due to static electricity of the soil.
MEASUREMENT OF THE HARDNESS OF MATERIALS USING THE ULTRASOUND METHOD
The hardness test damages the surface, as an impression remains after the test. The print is not large and does not destroy the product, but remains visible. That is why we can see hardness testing as a destructive-non-destructive method.
– simple surface preparation
– simple surface preparation
– hardnesses ≥650 HB cannot be measured
– depending on the hardness of the material, it is necessary to choose the appropriate force
– after testing, the print leaves a visible mark
DESTRUCTIVE TEST METHODS
CHEMICAL ANALYSIS AND PMI
Chemical analysis is used to determine the chemical composition of the material, especially if there are no supporting certificates or the authenticity of the certificate is to be proven.
PMI (Positive Material Identification) uses x-rays for spectrometric analysis of materials and comparison of content and quantity in the tested material with respect to a known standard. The method is also used to test the content of heavy metals in paints used in the shipbuilding industry.
Metallography deals with the investigation of the structure of metals and alloys using light metallographic and electron microscopes.
Macrostructure – visible with the naked eye or with low magnification
Microstructure – requires the help of a microscope
Metallographic analysis can provide information about the composition of the material in the previous processing and properties, in particular:
• grain size
• present phases
• chemical homogeneity
• distribution of phases
• deformations of the structure resulting from plastic deformation of the material
• thickness and structure of surface coatings
• determining the crack and mode of failure
When the cause of a break or other unexpected structural damage needs to be determined, the condition is first photographed. All possible information about the material, function, operation and how the damage occurred is written down. Then the part to be cut for metallographic analysis is determined.
Care must be taken to select the part that, through chemical and metallographic analysis, will provide the most answers about the cause of the damage. Also, samples of undamaged material should be taken for comparison.
In addition, the method of cutting the samples should be determined so that the structure is not changed by heat input (heating).
CERTIFICATION OF WELDERS
With certification, welders obtain a certificate for certain welding procedures (REL, MIG/MAG, EPP, AT, etc.) depending on the basic material, in accordance with Euro norms.
CERTIFICATION OF WELDING AND/OR CUTTING PROCEDURES (WPQR AND CPQR).
By certifying the welding and/or cutting process, the company obtains the right to manufacture steel structures (EXC2, EXC3 and EXC4) in accordance with Euro standards.
SUPERVISION AND COORDINATION OF WELDING
Supervision and coordination is carried out before, during and after the production of the steel structure in order to meet the requirements of Euro standards.
The work of our International Welding Inspector (IWIP-C) includes:
- interpretation of plans and specifications
- verification of specifications of welding technologies (WPSs), qualifications of welders
- verification of the use of qualified welding technologies
- overview of selected production test samples
- interpretation of test results
- preparing reports and keeping records
- preparation of inspection procedures
- checking the correct use of NDT methods
The work of our International Welding Technologist (IWT) includes:
- overview of technical requirements related to welding
- supervision of subcontractors
- care for the qualification of welders, solderers and welding operators
- care of welding equipment (welding sources and auxiliary equipment)
- planning of welding production
- care for the qualification and approval of the technology of welding procedures - welding technology (WPQR)
- creation of the welding technology specification (WPS)
- creation of work instructions
- care for the selection, procurement, storage and traceability of additional materials
- quality control before the start of welding works
- quality control during welding
- quality control at the end of welding works
- post weld heat treatment (PWHT) care
- control of non-compliance and corrective measures
- care for calibration and validation of measuring and test equipment
- Identification and traceability of all elements that affect the quality of the welding work
- quality records (production of the Welding Work Quality Manual).
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