In a large amount of manufacturing processes, the discovery of subsurface discontinuities is a challenge. Volumetric discontinuities are a threat to the integrity of parts. Finding pores, voids and other fusion related discontinuities is essential. One way of finding these discontinuities is the imaging of the weld and cast items through ionizing radiation.
Radiographic Testing is regularly used for process control throughout manufacturing. This form of testing aims to detect subsurface discontinues in the final product; ceramics, welds, composite materials and electronic components.
This testing can be used for the inspection of piping, storage tanks, refinery vessels and steel pressure vessels.
Conventional radiography systems need intricate arrangements to protect humans from ionizing radiation, which comes from the radio isotopes involved.
Several major infrastructural challenges arise from this process. Moreover, a large area must be cordoned off for the duration of radiography work. This process results in a significant cost from the loss of man-hours.
Close-proximity low radiation radiography is a development from the pre-existing radiographic equipment after the incorporation of additional radiation-shielding methods, and is used with the Selenium 75 source as opposed to LR192. The radiation beam is focused on the required area of inspection and shielding is used to avoid unnecessary radiation.
The close-proximity system requires the cordoning off of a very small area (as small as a radius of 3 metres). Therefore, the system eliminates the need to stop other fabrication work during this process, and can be operated 24 hours a day at any given location.
Ultrasonic Testing is used effectively in locating discontinuities as well as in the accurate sizing of subsurface discontinuities in welded objects. The detection of non-metallic inclusions, segregation of elements, and measurement of thickness are other areas where UT is frequently utilized.
An ultrasonic test can also measure the thickness and mechanical properties of a material, or to inspect the inner structure of a material for cracks and/or voids. Due to its simple characteristics, UT is used to assess a multitude of metallic, non-metallic and composite goods, such as the following: welds, joints, forgings, castings, sheets, tubing, plastics, ceramics and structural components.
Because UT is able to accurately detect surface and subsurface problems in a range of different materials it is one of the most useful methods available to quality assurance personnel.
Surface abnormalities come in a variety of forms, sizes and shapes. Visual inspection might not detect subtle discontinuities so special techniques and methods are needed for the detection of said abnormalities.
For this reason, liquid penetrant testing is aptly suited for detecting discontinuities such as cracks and porosity.
LPT is a commonly utilized NDT technique, popular for two main reasons: it is simple and flexible. LPT can inspect almost any given material, provided that its surface is not exceedingly uneven or porous.
Magnetic Particle Inspection is a non-destructive testing method, under the principle of Magnetic Flux Induction.
MPI is an NDT method applied under the principle of Magnetic Flux Induction.
MPI seeks to locate surface & near surface irregularities, rendering them visible to the naked eye by producing a magnetic field on ferromagnetic material using several sources (such as permanent magnetic or electro-magnetic using AC or DC currents).
Magnetic particles (either visible under a white light or fluorescent under a ultra-violet light) are used and the ensuing indications generated due to discontinuities in the material are analysed under the relevant standards and codes.
Traceability of proper material is very important in the determination of compatibility issues, design, corrosion resistance, and compliance to codes and standards, for example ASME Boiler and Pressure Vessel Code.
PMI is used to verify the composition of a material or when the material testing certificate is not available. PMI is a key testing tool, and can be used in construction projects.
Hardness testing is widely used to characterize materials and establish whether they are fit for their planned use. Testing is performed by pressing an indenter that is harder than the test sample using a specific force to determine the hardness value by measuring the depth or size of the dent.
Hardness testing is generally used to verify the appropriate heat treating method and a correlation between the test result and the desired material property allows for proper resource utilization and practical R&D applications.
Because moderate ferrite levels shield stainless steel and duplex steel weld metals from hot-cracking related weld defects, testing ferrite levels allows engineers to quantify the amount of weld metal ferrite to ensure fabrications are free of cracks. All magnetizable structure sections are measured according to the magnetic induction method (deltaferrite, martensite, and other phases).
Areas of application are onsite measurements such as austenitic plating as well as weld seams in stainless steel pipes, containers, boilers or other products made of austenitic or duplex steel.