A introduction to Immersion Transducers
2008-08-04

                                                                                          A introduction to  Immersion Transducers           A transducer is an electronic device that converts energy from one form to another.          Transducers are generally classified into groups according to the application£ºContact transducers and Immersion transducers.           Immersion transducers are designed to test parts partially or wholly immersed in water, which allows a uniform and fast coupling technique for rapid scanning of parts. It is specifically designed to transmit ultrasound in applications where the test part is partially or wholly immersed.           Immersion Transducers have several advantages over contact-type transducers. First, their uniform coupling reduces variations in sensitivity. Second, immersion transducers offer increased speed from the ability to perform automated scanning. Third, the focusing of immersion transducers increases the sensitivity to small defects. Immersion transducers are available in unfocused, spherically focused, and cylindrically focused configurations. An unfocused immersion transducer is used for general applications in the measurement of thick materials. A spherically focused transducer will improve the sensitivity to small flaws and defects. A cylindrically focused transducer is typically used in the measurement of tubing raw stock.           The immersion transducers' design allows them to operate in situations where the part to be tested is partially or fully submerged in fresh water. Immersion Transducers are also used inside water tanks for scanning purposes. Thus, scanning parts with irregular or complex geometries is possible because of the conforming water path between the probe and the material to be inspected. Superior near-surface resolution can be achieved when compared to contact transducers. Typical applications for immersion transducers are defect detection, on-line thickness gauging, corrosion monitoring, velocity measurements and dimensional analysis.           There are mainly three style models of the immersion transducers. Flanged Style Models      'F' Style Immersion Transducers are designed for exceptional performance in applications requiring higher beam energy and relatively lower frequencies. They are often used to examine products with mill-finish surfaces, such as pipe, forgings, billets, plates, shapes and extrusions. Larger diameter elements permit greater scan indexes for faster coverage of large test objects. D Style Models       D Style Immersion Transducers combine large elements with low frequencies for optimum results on rough-surfaced and/or extenuative test objects. Larger element sizes reduce beam-spreading and allow wider scan intervals. This series is often selected for testing inherently "noisy" materials. The right combination of element side and frequency can reduce noise reflections from coarse grain structure, or acceptable, small or scattered inclusions. In such cases, larger reject able flaws can be more easily detected. E Style Models      E-Style Immersion Transducers are the perfect choice for direct right angle beam applications, including through transmission, inside diameters, bore holes and other limited access conditions, Available in a wide range of frequencies and sizes.           In choosing the frequency and element diameter of an Immersion Transducer, you must consider the type of material being inspected, the section thickness, the type of discontinuities you need to detect and other inspection requirements. Moreover, if you require a transducer with high sensitivity and penetration, we recommend the medium damped transducer. On the other hand, if you need high resolution and/or thickness gauging, then the highly damped transducer should be your choice.       Immersion Transducers have mainly the following several applications: Automated scanning On-line thickness gagging High speed flaw detection in pipe, bar, tube, plate, and other similar components Time-of-flight and amplitude based imaging Through transmission testing Material analysis and velocity measurements        When using Immersion Transducers, you should also know the Usage Note: Transducers should not be submerged for periods exceeding 8 hours. Allow 16 hours of dry time to ensure the life of the unit.