Traditional NDT solutions
With technicians based around the UK, we offer a comprehensive range of industry proven Traditional NDT techniques to BS / EN / ASNT code and standards.
MISTRAS has offered the broadest range of Traditional NDT (Non-Destructive testing) services for more than 40 years. With a network of UK-wide regional offices, our staff is fully equipped and capable to provide whatever monitoring and testing solutions your industry requires. Our never-ending commitment to continuous improvement equals enhanced safety, increased productivity and reduced costs for customers. These extensive service capabilities make MISTRAS the ideal one-source provider for monitoring and inspection solutions, eliminating the ancillary costs multiple vendors entail and allowing customers to be as streamlined and efficient as possible. Simply put, MISTRAS saves you money while ensuring the standards are met.
Services at our Rotherham facility include:
LIQUID PENETRANT INSPECTION
This Traditional NDT method is used to locate surface-breaking discontinuities in non-porous materials. The principle is based on capillary action where penetrant is applied to the surface under inspection which will be drawn into surface breaking discontinuities, excess surface penetrant is then removed, a developer is applied to the dry surface which will draw out penetrant from any discontinuities to produce an indication. This can then be evaluated to determine what action should be taken. There are two main types of Penetrant, Fluorescent or Visible. Within each method there are several methods including water washable, postemulsifiable-lipophilic, solvent removal and postemulsifiable-hyperdrophilic. The type and penetrant method are chosen based on sensitivity levels 1-4 and are based on job site conditions and other variables.
Benefits of LPI:
- Used on a wide range of materials
- Large areas or large volumes can be inspected rapidly
- Parts with complex geometries can be inspected easily
- Visual of the anomaly on material
- Aerosol spray cans can make equipment very portable
MAGNETIC PARTICLE Inspection
Used for finding surface/near surface defects in ferromagnetic material, Magnetic Particle Inspection (MPI) is a versatile Traditional NDT inspection method used for field and shop applications. Magnetic particle testing works by magnetising a ferromagnetic specimen using a magnet or special magnetising equipment. If the specimen has discontinuity, the magnetic field flowing through the specimen is interrupted and leakage field occurs. Finely milled iron particles coated with a dye pigment are applied to the specimen. These are attracted to leakage fields and cluster to form an indication directly over the discontinuity. The indication is visually detected under proper lighting conditions. The basic procedure that is followed to perform magnetic particle testing consist of the following:
- Pre-cleaning of component
- Introduction of Magnetic field
- Application of magnetic media
- Interpretation of magnetic particle indications
It is essential for the particles to have an unimpeded path for migration to both strong and weak leakage fields. Therefore, the component in question should be clean and dry before beginning the inspection process. The presence of oil, grease or scale may compromise the inspection.
Benefits of MPI:
- Detect surface and near subsurface indications
- Can inspect parts with irregular shapes easily
- Pre-cleaning is not as critical
- Indications are visible directly on the specimen surface
- Low cost compared to many other NDT techniques
- Very portable inspection
Industrial radiography is used for a variety of applications but is commonly performed using two different sources of radiation, X-Ray and Gamma ray sources. The choice of radiation sources and their strength depends on a variety of factors including size of the component and the material thickness. Within the broad group of X-Ray and Gamma ray sources are a variety of camera choices with varying radiation strengths.
MISTRAS Services X-Ray capabilities run the gamut from 4 MEV units utilised to radiograph extremely large and thick castings and forgings, to portable X-Ray cameras used for field weld applications and thin wall material inspection. Gamma sources vary from very low level fluoroscopic units to perform real time corrosion under insulation surveys, to Iridium (Ir192) and Selenium (Se 75) sources used for a variety of weld inspections, to Cobalt (Co 60) inspections for thick component testing.
There are many advantages to radiography including: inspection of a wide variety of material types with varying density, ability to inspect assembled components, minimum surface preparation required, sensitivity to changes in thickness corrosion, voids, cracks and material density changes, the ability to detect both surface and subsurface defects and the ability to provide a permanent record of the inspection. The disadvantages of radiography are: safety precautions are required for the safe use of radiation, access to both sides of the specimen are required, orientation of the sample is critical, and determining flaw depth is impossible without additional angled exposures.
Traditional NDT using Ultrasonic inspection – high frequency sound energy to conduct examinations and perform measurements. Considerable information may be gathered during ultrasonic testing such as the presence of discontinuities, material or coating thickness. The detection and location of discontinuities is enabled by the interpretation of ultrasonic wave reflections generated by a transducer. These waves are introduced into a material and travel in a straight line and at a constant speed until they encounter a surface. The surface interface causes some of the wave energy to be reflected and the rest of it to be transmitted. The amount of reflected vs. transmitted energy is detected and provides information on the size of the reflector, & therefore the discontinuity encountered. Three basic ultrasonic techniques are commonly used: 1. Pulse-echo and through transmission – In pulse-echo testing a transducer sends out a pulse of energy and the same or a second transducer listens for reflected energy, also known as an echo. Pulse echo is especially effective when only one side of a material is accessible. 2. Normal/Angle Beam – Normal beam testing uses a sound beam that is introduced at 90 degrees to the surface, while angle beam utilizes a beam that is introduced into the specimen at some angle other than 90 degrees. 3. Contact and Immersion – To get useful levels of sound energy into the material, the air between the transducer and the specimen must be removed. This is referred to as coupling.
Benefits of UT:
- Detects surface and subsurface defects
- Depth of penetration vs. other test methods is superior
- Only single sided access is required with a pulse-echo technique
- High accuracy regarding estimating discontinuity size and shape
- Minimal specimen preparation is required
- Instantaneous results produced by using electronic equipment
- Detailed images can be produced with automated systems