EDDY CURRENT TUBE INSPECTION

NDT is a basic need for Industries like Power Plants & Refineries to ensure safety and reliability. Components like Heat Exchangers & Condensers need to be checked periodically from inside in these plants since leak of any kind can lead to productivity loss and more importantly serious environment hazards.Heat Exchanger & Steam Generators tubes in power plants, especially Nuclear power plants, needs to be inspected for leaks periodically to prevent hazards. Hence, identifying and replacing damaged and weak parts is very important task and ensures safe process and reliability.

Eddy Current Tube inspection is the High Speed & Fastest way to check for damages like ID Wall loss, OD wall loss, ID & OD Pitting, ID & OD Corrosion due to stress cracking etc., in metals.
MATRIX has in time, developed the Team and possesses the equipment to perform Tube Inspection works Reliably & Efficiently
Benefit
A benefit of eddy current testing is that detection of defects is instant, and can be reported immediately to site or operation managers

INFRARED THERMOGRAPHY

The Objective
Enormous losses in the industrial sector are caused by malfunctions which could be prevented. Although damages and degradation of isolation materials and other materials are not visible, in most cases they can be solved through preventive measures. The temperature of an object is often a sufficient indicator of the performance of the installation.

The Solution
Matrix can offer you inspection technology to make temperature differences visible.Infrared Thermography is a fast NDT inspection method which does not influence the process and maps the temperature differences of any object in a range from -50ºC to 1500ºC.

Our Services for Infrared Thermography
Infrared Thermography is an excellent help in monitoring or optimizing processes. Matrix brings the equipment needed during the inspection. All images will be saved digitally and after the analysis you will receive a comprehensive full color report.
Our Non-Destructive Testing Services also offer the necessary guarantees when quality, cost savings, business security and safety is needed, for both existing and new installations

MAGNETIC FLUX LEAKAGE

Matrix provides a complete tank floor Map MFL inspection; Hand Scan MFL and Pipe scan MFL inspection service with our Floor Map VS2i and Pipe scan PS 200.

MFL Technique
When a magnet is in close proximity to a steel plate magnetic lines of force (flux) are created within the plate. These lines of flux prefer to travel within the plate than the air. If the magnet is of suitable power it can create a near saturated flux in the plate.
A Corrosion pit and wall thinning will force the magnetic flux ‘out’ of the material and thus be detected using a Hall Effect sensor. The scanner has 36 no. of Hall Effect sensor; these 36 sensors are arranged in pairs forming 18 numbers.
A Hall Effect sensor is solid-state device, which when placed within an appropriate electrical circuit generates a voltage signal dependent on flux density. MFL system is designed to detect and size under floor corrosion for above ground level storage tank.

MFL floor map report – tank floor layout

Individual Plate Report Representation

RFET TUBE INSPECTION

Remote field testing (RFT) is an electromagnetic method of non-destructive testing whose main application is finding defects in steel pipes and tubes. RFT may also be referred to as RFEC (remote field eddy current) or RFET (remote field eddy current technique). An RFET probe is moved through the pipeline and able to detect inside and outside defects with approximately equal sensitivity. The RFET technique works with conductive materials such as copper, brass, stainless steel, etc.
RFT is primarily used to inspect ferromagnetic tubing since conventional eddy current techniques have difficulty inspecting the full thickness of the tube wall due to the strong skin effect in ferromagnetic materials.
The difficulties encountered in the testing of ferromagnetic tubes can be greatly alleviated with the use of the remote field testing method. The RFT method has the advantage of allowing nearly equal sensitivities of detection at both the inner and outer surfaces of a ferromagnetic tube. The method is highly sensitive to variations in wall thickness and tends to be less sensitive to fill-factor changes between the coil and tube. RFT can be used to inspect any conducting tubular product, but it is generally considered to be less sensitive than conventional eddy current techniques when inspecting non ferromagnetic materials.

INSITU OXIDE SCALE THICKNESS MEASUREMENT

The ID oxide scale is produced by oxidation in the re heater and super heater. The scale build up occurs when the tubes have experienced high temperatures for extended periods of time. The formation of ID scale reduces heat transfer and results in a further increase of tube metal temperature. Higher temperatures promote further growth of ID scale. The result is the ID scale feeds on itself and increases in thickness as it continues to grow.
The increase in ID scale and the associated tube metal temperature promotes creep in the tube metal. Formation of creep results in a loss of strength at high temperature and therefore a loss in remaining life. The final outcome of excessive scale is a thick lipped, long term overheats failure.
Ultrasonic technique
The ultrasonic method for measuring scale thickness is based on transmitting a wave through the tube thickness. The thickness is calculated by measuring the time difference between the signals reflected from the steel/scale interface and the tube ID surface. With advanced signal interpretation techniques, we can achieve Oxide scale Thickness measurements up to the resolution of 0.15 Microns.
At MATRIX. we use Advanced Ultrasonic Equipment’s and recommended accessories to perform Internal Oxide Scale Thickness measurements to ensure accuracy and repeatability.
Theory
The very high temperatures found inside steam boilers (in excess of 1500 degrees Fahrenheit or 800 degrees Celsius) can cause the formation of a specific type of hard, brittle iron oxide called magnetite on the inside and outside surfaces of steel boiler tubing. At very high temperatures, water vapor will react with the iron in the steel to form magnetite and hydrogen.
The speed of this reaction increases with temperature. Oxygen atoms will diffuse inward through the magnetite layer, and iron atoms will diffuse outward, so the scale continues to grow even after the tube surface is completely covered.
Magnetite scale acts as thermal insulation on the pipe, since the thermal conductivity of scale is only about 5% that of steel. When heat can no longer transfer efficiently from the flame through the tube into the steam inside, the tube wall will heat up to temperatures beyond the intended operating range. Long term exposure to overly high temperatures, combined with the very high pressure inside the tube, leads to intergranular micro-cracking in the metal and to creep deformation (a slow swelling or bulging of the metal), which in turn eventually leads to tube failure by bursting.
A secondary issue is oxide exfoliation, in which pieces of oxide scale break off (usually due to thermal stresses during boiler startup or shutdown). These hard pieces will be carried by the steam flow into the turbine, where over time they will cause erosion damage.
The growth of magnetite scale and the associated metal damage are primary limiting factors with respect to boiler tube service life. The process begins slowly and then accelerates, for as the scale grows thicker the tube wall becomes hotter, and that in turn increases the rate of both scale growth and metal damage. Studies in the power generation industry have indicated that the effect of scale is relatively insignificant up to thicknesses of approximately 0.012 in. or 0.3 mm, but that beyond that thickness the negative effects of scale increase rapidly. Periodic measurement of scale thickness allows a plant operator to estimate remaining tube service life and to identify and replace tubes that are approaching the failure point. Ultrasonic testing provides a quick and nondestructive method for measuring scale. In all cases the coupling surface must be smooth and in some cases surface preparation will be required.

VACCUM BOX TESTING

Vacuum Box testing is used to check for any leaks or fault in the welding of bottom & annular plates of the storage tank.

The objective of the vacuum box technique of bubble leak testing is to locate leaks in a pressure boundary that cannot be directly pressurized. This is accomplished by applying a solution to a local area of the pressure boundary surface and creating a differential pressure across that local area of the boundary causing the formation of bubbles as leakage gas passes through the solution