Services

Advantages & Capabilities:

• Sensitivity to detecting very fine surface cracks and near surface discontinuities in ferrous materials
• Portability for field use
• Relatively simple and inexpensive to perform
• Can be performed on thinly coated, painted or plated parts

Disadvantages & Limitations:

• Can be used only on ferrous materials
• Magnetic field and discontinuity orientation is critical
• Demagnetization may be required
• Multiple shots may be required depending on complexity of the part
• Presence of surface coatings may reduce the sensitivity of the test.

Advantages & Capabilities

• Quickly examines all accessible surfaces
• Detects very small surface discontinuities
• Capable of examining the entire exterior surface in one operation even though object may have complex shape.
• Used on wide variety of materials including ferrous and nonferrous metals and alloys and fired ceramics.
• Relatively inexpensive and non-sophisticated equipment
• Sensitivity magnifies the size and location of discontinuities
• Sensitivity can be adjusted by selection of penetrant, removal technique and type of developer.
• Technicians can visually detect indications

Disadvantages & Limitations

• Detects Surface Discontinuities Only
• Discontinuities Must Be Open to the Surface
• Extensive Surface Preparation is Required
• Requires Good Ventilation
• Time Consuming if Reprocessing is Required

Advantages & Capabilities:

• High penetrating power
• High sensitivity
• Usually only one surface needs to be accessible
• Insight in size, orientation, shape and nature of defects
• Non-hazardous to operations or nearby personnel
• Portable equipment
• Can be used in automated setup
• Immediate test results

Disadvantages & Limitations:

• Surface must be accessible to transmit ultrasound
• Usually a couplant (gel or oil) is needed to enable interference-free transfer of the ultrasound
• Objects that have a rough surface or are very small, thin or not homogenous are difficult to inspect
• Cast iron and other coarse grained materials are difficult to inspect due to low sound transmission and high signal noise
• Linear flaws oriented parallel to the direction of the sound beam may go undetected
• Reference standards are required for equipment calibration and for the characterization of flaws

Advantages & Capabilities:

• Can be used with most materials.
• Provides a permanent visual image record of the test object
• Reveals the discontinuities of a material.
• Discloses fabrication errors and often indicates necessary corrective actions
• Reveals assembly errors.
• Detects both surface and subsurface defects.
• Sensitive to changes in thickness, corrosion, flaws and material density changes

Disadvantages & Limitations:

• High risk of radiation hazard
• Can be sensitive to defect orientation and could miss planar flaws
• Has limited ability to detect fine cracks
• Access is required to both sides of the object
• Thickness limitation of the materials can be penetrated
• Skilled radiographic interpretation is required
• Relatively slow process
• Require high capital cost

How to Identify NORM?

• Conducting NORM monitoring/survey by using appropriate equipment
• This must be carried out by qualified and certified Radiation Protection Officer (RPO).

Exposure Routes

• Inhalation of contaminated dust.
• Ingestion of contaminated material.
• Absorption of contaminated material through open cuts and wounds
• Main route of exposure is inhalation.

NORM Survey Equipment’s

• TRACERCO NORM MONITOR

Phased Array UT vs Conventional UT

Common between Phased Array UT and Conventional UT

• Both techniques are ultrasonic testing
• PAUT can be deployed anywhere where conventional UT can but used.

Advantage of Phased Array UT over Conventional UT

• Faster
• More Accurate
• Capability of doing more with ultrasonic waves with single probe
• Beam Steering (Change of Angles)
• Beam Focusing
• Electronic Scan
• Permanent Digital Record
• Various software analysis options
• Ability to create recordable images
• Ability to plot images in various display format
• Ability to create desired ultrasonic beams by using various types of set up files
• Ability to create a beam group with a range of angle (s scan)
• Ability to create a beam group with dynamic focus
• Ability to accommodate multiple probes

Limitation of Phased Array UT over Conventional UT

• High Sensitivity when combined with TOFD
• Higher equipment cost resulting higher initial investment

Advantage of TOFD

• It is more sensitive
• Best Available NDT technique for flaw sizing and height
• Higher POD
• Exact height measurement
• Detection is not dependent of the orientation of the discontinuity.
• Faster and most accurate technique.

Limitation of TOFD

• Higher Sensitivity for our application
• Both Side access
• Any supplementary technique is to be used with the combination of TOFD for accurate characterization (in our case we are having PAUT as supplementary technique with TOFD).

Eddy Current Testing (ECT)

Eddy Current Testing (ECT) is a technique that is extremely suitable for the inspection of non-ferritic pipes.

Eddy Current is a test in which a coil generates an alternating magnetic field. This creates Eddy Currents in the pipe wall. Defects in the pipe influence the course of these Eddy Currents. The Eddy Currents in the pipe wall also causes a magnetic field. A comparison of the changes between these two magnetic fields provides information about the status of the pipe wall at that point.

EC detects and quantifies both local defects such as pitting and the formation of cracks, and a general reduction in wall thickness. Internal and external defects can be detected and distinguished. The filling factor is essential for the sensitivity and reliability of the inspection. That is why the pipes have to be clean so that the largest possible measurement probe can be used. All of the magnetic particles of the pipe also need to be removed in order to minimize any possible interruptions of the signal.

Characteristics :

• Suitable for Non Ferrous Tubing such as SS304 /316, Brass, Titanium / Inconel / Copper / Copper Nickel etc
• Can Detect Pits / Corrosion / Erosion / Axial Cracking
• Uses Multiple Frequencies for Better Analysis and Flaw Sizing
• The Probe needs a good fill factor to remain sensitive
• Probe centering is important for uniform sensitivity
• Very Fast Technique

Remote Field Eddy Current Testing (RFET)

The Remote Field Testing (RFT) is extremely suitable for the inspection of ferrite pipes. RFT is particularly suitable for the detection and quantification of wall thickness reductions. Internal and external defects can be detected but not distinguished. The filling factor is much less important for the sensitivity and reliability of the inspection than the other applicable techniques. RFT testing is not suitable for testing finned pipes.

The measurement probe is positioned in the pipe. The probe contains a transmission and reception coil. The transmission coil generates a magnetic field that penetrates through the pipe wall to the outside. This field then penetrates back in through the pipe wall at the height of the reception coil. Because the magnetic field penetrates the pipe wall twice, it is slowed and weakened to a certain extent. The slowing and weakening that occur depend on the local pipe thickness and are measured.

Because the RFT technique is equally sensitive to ID and OD defects, it cannot be used to determine if wall loss occurs inside or outside the tube wall. RFT is a through-wall transmission technique where the magnetic field passes through the tube wall twice: once at the exciter location and once at the receiver location. Whether a defect is aligned with the exciter or the receivers, an effect will be felt by the receivers. The measurement is relative to the total material thickness crossed by the indirect magnetic field.

Characteristics :

• Suitable for Ferromagnetic Pipes and Tubes such as those found in boilers and Heat Exchangers
• Same Sensitivity is achieved for internal and External flaws
• Technique is relatively insensitive to probe lift off or wobble
• Can be used to examine very thick tube wall (up to 12mm)
• A low lill factor enables the inspection of partially scaled tubes and boiler tubes with swages and bends
• Centralization of the probe is not as critical as it is for ECT inspections
• Typical pulling speed is between 0.10 m/s and 0.3 m/s

Near Field Testing (NFT)

Near field testing (NFT) is used for the inspection of  fin fan carbon steel tubing in heat exchangers tubes it was first developed as an alternative to magnetic flux leakage (MFL). Specifically designed to detect internal corrosion, erosion, or pitting on the inside of carbon steel tubing.  Because the eddy current penetration is limited to the inner surface of the tube, NFT probes are not affected by the fin geometry on the outside of the tubes.

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NFT is a technology that uses two coils — a transmitter and a receiver. Typically the receiver coil is close to the transmitter coil, taking advantage of the transmitter’s near-field zone — that is, the zone where the magnetic field from the transmitter coil induces strong eddy currents, axially and radially, in the tube wall. NFT is also much more sensitive to defects close to structures such as support plates and tubesheets.

Benefits of NFT

• Fast inspection
• No need for external reference coil
• Easy to use
• Unaffected by external structures

Internal Rotating Inspection System (IRIS)

Rotating ultrasonic pulses scan the entire pipe wall from the inside. The probe head is rotated by means of water. The water also conducts the ultrasonic signal. The reflected ultrasonic signal is translated into an associated internal diameter, external diameter and consequently the wall thickness.

The Internal Rotary Inspection System (IRIS) is a technique that is extremely suitable for inspecting both ferrite and non- ferrite pipes. IRIS makes it possible to measure wall thicknesses very accurately. However, the method is far slower than eddy current inspection for example. Internal and external defects can be detected and distinguished, not only the depth but also the geometry.

Because the method is based on reflecting ultrasonic pulses, it is important that the pipes are very clean inside. Soiling in the pipe can adversely influence the accuracy of the measurement.

The internal rotary inspection system (IRIS) is an ultrasound technique used to measure thickness of ferrous and nonferrous tubing. This method allows the detection of general thinning such as corrosion and erosion, and of localized defects such as wear tear, scars, inside diameter (ID) and outside diameter (OD) pits. However, it cannot be used to detect pinholes and tight cracks. As long as tubes are clean enough to avoid ultrasound diffraction and attenuation losses, IRIS can accommodate a wide range of tube diameters and wall thicknesses. Typically, the pulling speed is quite slow, about 50 mm/s.

The IRIS probe consists of a rotating 45-degree mirror that redirects the ultrasonic beam into the tube wall. The mirror is driven by a small turbine that rotates at about 50 rev/s. The turbine is set in motion by the pressure of water pumped inside the probe. As the probe is pulled, the spinning motion of the mirror results in a helical scan path, so from one revolution to the next, the complete surface of the tube is covered.

The ultrasound beam is generated by the transducer; the beam hits the mirror and is reflected at a 45-degree angle. Because no mirror is perfect, a small echo is reflected back to the transducer. Other than that, ultrasound waves are partially reflected by the tube internal wall (ID) but also transmitted through the wall, and finally reflected by the tube external wall (OD). Using the speed of propagation of ultrasound in the tube material, the wall thickness can be calculated by using the time-of-flight difference between OD and ID echoes.

This series of reflections (echoes) would appear as shown beside on a time base A-scan view.

 The target pin echo (yellow) is generated by a pin attached inside the probe which produces an ultrasonic reflection each time the mirror passes it. This echo is used to synchronize the screen display.

Characteristics:

• Suitable for Ferrous and Non Ferrous materials
• Detects General thinning such as corrosion, erosion and localized defects such as pitting and wear scars
• Measures the absolute wall thickness value as well as the internal and external diameters of the tube
• Accommodates a wide range of tube diameters and wall thickness
• Tube cleaning is very important to avoid attenuation losses
• Typical pulling speed of 50mm/s or 2in/s

Magnetic Flux Leakage Testing

Magnetic Flux Leakage (MFL) Testing is an NDT technique used to detect pitting, circumferential cracks, and wall losses in ferromagnetic tubes such carbon steel, nickel, and ferrous stainless steel. This technique is typically used for the inspection of air cooler and heat exchanger tubes.

 The defect sizing capacity of MFL has some limitations; the signal amplitude is affected by pulling speed variations and the signal has no phase component. This makes MFL more of a detection method than a sizing one. Inspection is quite fast; the pulling speed can go up to 1 m/s. As for ECT, this technique requires a good fill factor as well as a good probe centering position to maintain a fair sensitivity to small volume defects. 

The principle of operation is based on magnetization. Two permanent magnets coupled to a steel core are used to magnetize the tube wall until complete saturation is reach. To that, three coils are added; each one being sensitive to specific defects.

For wall loss detection, we use the coil operating in the absolute mode. That coil is wound around the steel core between the two magnets. It measures the strength of the magnetic field produced by the magnets. So where there is general thinning such as erosion, even if no flux leakage occurs, the strength of the magnetic field decreases and this variation is detected.

To detect pitting, we use the lead coil. That coil is wound over the absolute coil, between the two magnets. When the magnetic field comes across pitting, the flux lines are diverted and theses distortions cannot be contained in the tube wall. Then flux leakage occurs on the inside or outside surface of the tube depending on the pitting location. The lead coil will detect this leakage but it is not possible to deduce the location (ID or OD) of the defect. To find the pitting location, you need the response from a third coil, the trail one.