Advanced inspection services
In the competitive market today, the trend is to reduce maintenance costs and maintenance costs. In addition, the limitations of the NDT procedures should be understood, and therefore advanced inspection procedures are applied in cases where normal procedures are restricted and require less repair time. In new industrial environments, materials are used that require other methods than usual NDT methods, in which case, advanced inspections will be applied.
Tobat Tak Consulting and Technical Inspectorate has been one of the leading providers of these services in Iran since 1998 by providing new inspection methods. The company has implemented many projects in the field of new inspections for oil, gas and petrochemical complexes.
Tubitak provides the following services in the field of new inspections:
Mag-wave electromagnetic Technique (DC-Saturation Eddy Current)
Mag Wave was developed to utilize eddy current technique on ferrous material. The benefits of this inspection method are that small pitting and cracking and large volume flaws can be detected and OD and ID flaws can be differentiated. The saturation can also be adjusted to eliminate signal noise due to finned tubes.
Ultrasonic Internal Rotating inspection system (IRIS)
IRIS is a method for examining tubes with high frequency ultrasonic immersion testing in order to find internal/external corrosion or erosion damage. It can measure wall thickness of tubes with highly acceptable accuracy. It is commonly used in inspection of boilers, heat exchangers and fin fan tubes.
Remote Field Testing (RFT)
Remote Field Testing is utilization of electromagnetic field in finding defects in steel pipes and tubes. RFT is preferably used in ferromagnetic materials such as boilers, heat exchangers, cast iron pipes and pipelines. RFT has widely spaced coils to pick up through transmission field signals.
Digital Radiography Testing (DRT)
Utilizing the state-of art electronic technology and sensors instead of films and revealing processes, digital radiography is able to accelerate conventional radiography and lower the costs by omitting the need for films and dark rooms. The films are displayed and saved on a computer. Some advantages of digital radiography are the possibility of reusing sensors instead of radiography films which are usable only once, omitting the need for dark rooms and other related equipment and reducing exposure time from minutes to seconds therefore saving X-ray equipment useful life up to 60%.
Saturated Low Frequency Eddy Current (SLOFEC)
The SLOFEC inspection technique uses the eddy current principle in combination with a magnetic field. Utilizing superimposed DC-magnetization, the depth of penetration of the eddy current field lines in the ferromagnetic material is increased. The SLOFEC technique is regarded as a fully acceptable NDT method in an increasing number of industries special for oil, gas and petrochemical industries. Some of the advantages of this method are high inspection speed, high inspection temperature range, high defect detection sensitivity and reliability and distinction between external and internal defects.
Due to the possibilities of adapting the eddy current frequency and reacting on the magnetic field line changes inside the material, SLOFEC can be used for the inspection of materials from low to high (Up to 33 mm) wall thicknesses as well as the inspection on top of the coatings (up to 15 mm).
Acoustic Emission (AE)
Acoustic emission is a method for examining material behavior under stress. When a solid material undergoes mechanical loading, structural changes will cause local sources of elastic waves and acoustic waves are radiated. Major applications of acoustic emission are source location, material mechanical performance evaluation and safety monitoring of structures. With acoustic emission, one “listens” to the sounds of active damages when the material “talks”.
Low Frequency Eddy Current Testing (LFET)
Low frequency eddy current testing is used to inspect storage tanks, convex or concave surfaces as well as ferrous and non-ferrous metal tubing/piping surfaces. LFET scanners can be used in setting where competing technologies fail or inconvenient including water walls, re-heaters and super-heaters, storage tanks, pipelines, service water pipes, fire protection pipes, coal mill pipes, general pipes, pressure vessels and heat exchanger shells.
Guided Wave/Long Range Ultrasonic Testing (LRUT)
Guided wave testing is one of the newest ways for inspection utilizing mechanical stress waves. It is widely used in inspection of metallic pipelines, rail tracks, rods and metal plate structures. Guided wave inspection benefit from very low frequencies compared to conventional ultrasonics. It can be utilized in several different pipeline geometries using torsional, longitudal and flexural waves.
Phased Array Ultrasonic Testing
Phased Array is an advanced method of ultrasonic testing that has applications in medical imaging and industrial testing. When applied to metals, the PAUT image shows a slice view that may reveal defects hidden inside a structure or weld. Phased array uses an array of elements, all individually wired, pulsed and time shifted.
PAUT permits optimizing defect detection while minimizing inspection time. Phased array offer significant advantages over conventional radiography such as no safety hazards, inspection as soon as the weld in cool, better detection and sizing and great flexibility in parameter range.
Time of flight diffraction (TOFD) is an advanced automated computerized UT based NDT technique, used for in-service inspection of welds for heavy walled pressure vessels. TOFD system is capable to scan, store and evaluate flaw indications in terms of height, length and position with greater accuracy and is suitablefor weld thickness ranging from 13 mm to 300 mm.
TOFD has some inherent issues (e.g. dead zone at the surface, beam spread) and is usually pair with PAUT in order becme relible, versatile, rapid and effective.
Eddy Current Testing (ET)
Eddy current testing is a method of non-destructive testing which utilizes electromagnetic induction to detect defects in a material. It is widely used in testing of tubes (non-magnetic, e.g. stainless steel, brass, Cu-Ni, etc.) in different types of heat exchangers. It’s a fast method capable of detecting different flaws like cracks, various types of corrosion and discontinuities.