There can be fewer more risky industries and environments than those involving petrochemicals and power generation.Harsh, challenging and in constant danger of cataclysmic incidents, the focus on health and safety is understandablyhigh. Harmonious working between man and materials is essential and, whilst much humanendeavour can be observed and regulated, inert equipment is always prone to theunexpected. Minimising risk is very much a way of life.
Both industries rely heavily on arterial infrastructure; tubes of all dimensions and uses, being especially dependent on heat exchangers and boilers. Often tubes are bundled together making even visual inspection difficult or hazardous; in many cases normal ultrasonic and radiographic inspections fail to achieve results to an acceptable standard. Allied to these safety issues are economic factors relating to downtime costs and production shutdowns, frequently measured in weeks. Risky reliance on visual inspection and destructive testing of many small-bore tubes has led to past uncertainty and potentially expensive decisions as to whether and when to repair or replace.
These high levels of uncertainty over managing risk can now be significantly reduced with advanced techniques providing accurate test and inspection results. ITCL now uses portable inspection systems to thoroughly inspect small-bore tubing. These systems are nondestructive and as such, ITCL is at the forefront of service provision, utilising an arsenal of techniques appropriate to your specific circumstances.
Which services do ITCL provide?
Remote Field Eddy Current Technique (RFT)
This process is well adapted to the inspection of small-bore ferromagnetic tubes such as carbonsteel. Using electromagnetic techniques this is now the industry standard inspection for boilersand heat exchangers due to its low frequency (typically 50-1000Hz). The probe consists of twocoils in a send-receive configuration which are inserted into the tube. The energised exciter coiltransmits a signal to the detector coil located some distance away. This signal passes throughto the outside tube wall returning to arrive at the detector coil. With wall thinning thereis less shielding hence the return time (greater phase) and attenuation (greateramplitude) is shorter. Phase and amplitude traces are generated as the probe ispulled through the tube as recorded data identifies the metal loss. Flaw sizingis also possible with RFT enabling depth, length and circumference to beaccurately calibrated.
Another electromagnetic technique which has been adaptedfor small-bore tubing manufactured from non-ferrous metalssuch as stainless steel, titanium, copper, brass, coppernickelalloys and inconel. ECT is based on the principlesof electromagnetic induction and uses a test coilthrough which is passed an alternating or varyingcurrent known as the primary field. This induces avarying secondary electromagnetic field in the testobject, known as an eddy current. In this waycharacteristic changes in the test object such asconductivity, permeability and geometry causethe eddy current to change which is reflectedto the test coil. A number of frequenciesin differential and absolute modes detectgradual wall loss. Multi-frequency is essentialto differentiate between defects and metallicdeposits and also enables defects undersupport plates to be detected.
Magnetic Flux Leakage Technique (MFL)
Another electromagnetic technique that is applied to small-bore ferromagnetic heat exchangers made from carbon steel. An MFL probe consists of a magnet with a coil type and Hall element pickups. Coil type identifies the rate of change of flux and detects small defects that cause perturbations; the rate of change inducing an output voltage read by the probe. The Hall element picks up absolute flux with its sensor detecting gradual wall loss. Additionally it can be used for sizing wall loss flaws.
Ultrasonic Iris Technique (IRIS)
This internal rotary inspection system measures thickness using ultrasonic waves. The probe consists of an ultrasonic transducer that is lined up to the centreline of the tube and to a rotating mirror. The mirror reflects the beam in the radial direction as it rotates in the tube. As the probe is pulled along the tube it scans the entire internal circumference. Frequently used for carbon steel tubes IRIS is sometimes used with nonferromagnetic tubes for defect verification. A highly accurate technique for thickness measurement, IRIS will not identify pinholes and cracks.
How do I know which technique is appropriate to my needs?
ITCL only employs highly trained technicians conversant with the latest techniques. Many years experience working with diverse companies in the UK and abroad have given us both depth and breadth to our competency. Investment in training and high awareness of environmental and health & safety issues enables us to deploy our multi-skilled workforce effectively; both at the operational level and for those times when specialised consultation is appropriate.
With ITCL you get the full package: Immaculate attention to effective, high quality test and inspection routines and access to professional cutting-edge knowledge.
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