Non-Destructive Testing (NDT)

Liquid Penetrant Testing is normally applied to all non-ferromagnetic metals.

It is based on the ability of certain liquids to easily penetrate internal surface discontinuities.

It serves to detect the presence of surface damage which must necessarily be open to the surface.

The defects typically detected by Liquid Penetrant Testing are: corrosion craters, pitting, and cracks.

The inspection can be performed in the visible field using the color contrast method or in the ultraviolet field using fluorescent products and a UV lamp (WOOD’S lamp).

Magnetic Particle Testing (MT) is applied exclusively to ferromagnetic materials.

It is based on the principle that when a magnetic field is applied to the test piece, the presence of a discontinuity orthogonal to the generated magnetic field produces a secondary (distorted) magnetic field. This distorted field has the ability to "trap" the magnetic particles used in the inspection.

It serves to detect the presence of surface/sub-surface damage that is not necessarily open to the surface.

The defects typically detected by Magnetic Particle Testing are: cracks and discontinuities within the material.

The inspection can be performed in the visible spectrum using the color contrast method, or under ultraviolet light using fluorescent products and a UV lamp (WOOD’S lamp).

It is based on the reception of sound waves that develop and propagate both on the liquid surface and on the metallic surface of a vessel. These sound waves are generated by the metal when subjected to stress/strain.

Using this technique, it is possible to verify the condition of the bottom of an atmospheric flat-bottom tank, searching for active corrosion and potential product leaks.

This technique can also be applied to pressure vessels to detect damage such as corrosion and/or cracks during hydraulic pressure testing.

Carbon steel, stainless steel, and fiberglass tanks can be subjected to Acoustic Emission Testing. Furthermore, investigations can be performed on metallic structures and concrete.

The Eddy Current Testing method and all its various application techniques are based on the application of a magnetic field, generated by a probe and applied to the part under examination. The presence of a defect will create a distorted magnetic field which will be converted into an electro-instrumental signal. The physical characteristics of each metal or alloy (magnetic permeability, conductivity, etc.), in association with the specific part under examination and the type of damage to be detected, will indicate the most appropriate technique to adopt. This method can be used for the detection of surface or sub-surface damage in mechanical components, heat exchanger tubes, and more.

It allows for the definition of functional groups and fingerprints present in the molecule through the formation of signals. It is essential for the characterization of plastic materials.

The inspection of a plant allows for the identification of critical points that require further investigation or maintenance interventions. Focusing specifically on a single piece of equipment, the internal and external visual inspection can highlight macro defects such as: damage to paint and/or insulation, supports, structures, etc., or indications of damage typical of the service or environment such as: corrosion, formation of oxide scale, or cracks.

The inspection can be performed directly by the technician/inspector using their eyesight with the aid of manual tools such as: calipers, scrapers, hammers, and torches; or indirectly with the aid of video endoscopes, video cameras, or drones.

The method is based on the possibility of magnetizing a specific portion of a pipe or plate. The instrument calculates the demagnetization time of a specific component made of material X, with thickness Y and insulation thickness Z.

It verifies the presence of Corrosion Under Insulation (CUI) and measures the residual thickness of pipes and plates without the need to remove the insulation, coating, fireproofing, etc.

Besides providing a preliminary screening for the presence of CUI and FAC (Flow Accelerated Corrosion), it is also possible to perform accurate metal thickness measurements.

Phased Array is an advanced ultrasonic technique used for defect detection, sizing, and the creation of images/maps.

Phased Array is a type of Ultrasonic Inspection that can be employed as an alternative to Radiographic Testing and is one of the most distinctive methods for Ultrasonic Inspection on welds.

Unlike classic manual Ultrasonic Non-Destructive Testing methods, Phased Array Ultrasonics allows for the electrical manipulation of the probe's characteristics, applying time delays to the transmitted and received signals.

This type of non-destructive instrumental investigation utilizes multi-element (array) probes for greater scanning capability compared to conventional ultrasonics.

The addition of scanners and encoders for data recording provides digital inspection data.

The ultrasonic test is repeatable and verifiable over time using the dedicated instrument or software.

Metallographic replication is applicable to all metallic materials.

The technique is based on highlighting the structure of the metal to be analyzed and generating a replica of that structure onto a suitable substrate for subsequent microscopic analysis in a laboratory.

It is used to verify the structural and morphological characteristics of the alloy/metal, as well as any variations due to malfunctions/incidents, or damage resulting from service operation (e.g., CREEP).

The use of specific video cameras that operate in the ultraviolet and infrared spectrums makes it possible to highlight temperature differences in various components and verify the presence of damage.

It is possible to check for the presence of damage and perform preventive maintenance on electrical panels, motors, electrical components, refractory-lined plant equipment, lines carrying fluids with suspended materials, etc.

The ultrasonic method and its various applications are utilized across a wide range of materials: from metals and alloys to concrete, composite materials, etc.

It is based on the principle of ultrasound propagation within specific materials (for which the ultrasonic propagation velocities are known) and the use of trigonometric calculations. The ultrasounds (used for this type of inspection) do not propagate in vacuum or air but do so in liquids and gels.

It is a volumetric method because it allows for the analysis/verification of the conditions/characteristics of a specific volume portion of the material.

The classic applications include:

• Measuring the wall thickness of pipes/plates, commonly called thickness measurement (or ultrasonics thickness gauging).
• Searching for internal or surface defects within a metal, commonly called flaw detection (or ultrasonic flaw detection).

More or less complex instruments are used, combined with probes employing longitudinal or angled beams. The use of traditional probes of various frequencies (usually between 2 and 10 MHz), either single or dual crystal, is referred to as thickness gauging and flaw detection. The use of probes consisting of multiple crystals managed by software is referred to as the PHASED ARRAY technique.

The use of different types of ultrasonic waves, which can be generated instrumentally or selected through mechanical means (angled wedges) and managed by software, allows for specific inspections using techniques such as: TOFD (Time Of Flight Diffraction), GW (Guided Waves), and EMAT.