Equipment
Phased array acoustic interfaces, standoffs & delay lines

FlawInspecta Standoff Options Standard 0 degree standoff with solid front face This standoff provides a mechanism for the standard tapered array to be coupled with the inspection surface to achieve 0 degree compression wave inspection. The contact area means that the assembly is easy to maintain normal to the scanning surface even for manual inspections. It is therefore well-suited to inspecting large relatively flat surfaces. Coupling is usually via a thin surface film of water that can be dispensed as a mist before scanning. Position sensor options include: Standard C-scan trolley Standard cable sensor (needs guide) Compatible with stitch jig Compatible with ANDSCANŽ Compatible with KitScanner Reduced size 0 degree standoff with couplant feed This 0 degree standoff is smaller than the standard head but is still easy to maintain normal to the surface. It has an integral water feed for continuous couplant provision whilst scanning and so is suitable for large areas. However the feed means that it is not possible to scan as close to surface obstructions as either the standard or the reduced contact area standoff (see below). Position sensor options include: Standard C-scan trolley (needs attachment) Standard cable sensor (needs wheel attachment) Compatible with ANDSCANŽ Compatible with KitScanner (needs attachment) Reduced contact 0 degree standoff with solid front face This 0 degree standoff has a contact area closely matched to the acoustic window at the scan interface. It is therefore well-suited to providing good acoustic contact on structures with gently curving surfaces and on operating right up to the edge of surface obstructions. The minimisd contact area makes it less easy to maintain normal to the surface but can be used in conjunction with the sprung mounting assembly (see below). Coupling can be provided by the same water film as the standard 0 degree standoff but an alternative is to use the integral water feed into foam strips. These strips ensure that the surface is wetted in advance of the array yet leave minimum water behind and so also reduce the amount of water required. Position sensor options include: Standard C-scan trolley (needs attachment) Standard cable sensor (needs wheel attachment) Compatible with ANDSCANŽ Compatible with KitScanner (needs attachment) Sprung body 0 degree standoff with solid front face This core of this 0 degree standoff is the same as the reduced contact area standoff and so offers the same acoustic benefits. The key difference is that it can be inserted into a sprung carriage that maintains the array normal to the scanning surface - even of surfaces with changing curvature. The carriage comes complete with wheels to act as guides when used with the cable sensor but these can be removed for full free movement in the ANDSCANŽ position sensing arm. Position sensor options include: Standard cable sensor Compatible with ANDSCANŽ Water-coupled 0 degree standoff with membrane The condition of the inspection surface can present considerable challenges. Rough interfaces (e.g. when the material is corroded or when paint has been removed in parts) or the presence of fasteners protruding above the surface, can cause the array head to rise off the surface. Even if couplant is able to fill the gap, there can be significant acoustic reverberations that would mask any detail inside the material. The conventional approach to inspecting these is an immersion technique but this is not feasible for most in-service inspections. A solution often adopted for single element automated systems is a bubbler to maintain a continuous water path but this can involve significant volumes of water, especially for the large contact areas of arrays. DSL is able to offer a solution that makes use of a proprietary membrane that is acoustically matched to water. This membrane retains the water column in front of the array and so minimises the water requirement to the gap between membrane an target material. Since the material has the same acosutic properties as water, it produces no echoes at the interface even in the event of significant lift-off from the surface. The ride height of the membrane can be adjusted so as match the requirements of the inspection - to give complete clearance where the surface irregularity is extreme or a low height with minimum water requirement when there are just fasteners slightly proud of the surface. A further advantage of this approach is that the water provides minimum attenuation even above 10MHz and so broadband inspection (and ultrasonic spectroscopic analysis) are all possible Position sensor options include: Standard cable sensor Compatible with ANDSCANŽ Angled standoff with membrane The angled standoff uses the same proprietary membrane technology as the water-coupled standoff above but with the array positioned to generate the refracted beams at the required angles. A variety of configurations are available - the photo showing the format to generate a swathe of 45 degree shear waves in aluminium at right-angles to the array axis. This configuration is well-suited to inspection of airframe fasteners for cracking even on 2nd or 3rd layer skins. The standoff has attachments for the standard C-scan trolley and a set of removable wheels for use with the cable position sensor. Position sensor options include: Standard C-scan trolley Standard cable sensor Compatible with ANDSCANŽ Compatible with KitScanner

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