Application of high power ultrasonics for fouling removal in submerged structures

Abstract

Fouling build up is a known problem in the industry. Accumulation of fouling can occur in different structures e.g. offshore pipes, ship hulls, floating production platforms. The type of fouling that is being accumulated is dependent on environmental conditions surrounding the structure itself. Current methods that are deployed for fouling removal spans over hydraulic, chemical and manual means. Current technologies such as DynaJet (cavitating water jets) and Hydrex's underwater ship hull cleaner have both advantages and disadvantages, where one common disadvantage is to put the operation of the structure to a halt in order to commence the fouling removal process. Currently, ultrasonic baths are used for cleaning by generating cavitation bubbles which implode on the surface of fouling, particularly in Reverse Osmosis applications. Conventionally, components that have accumulated fouling are placed into an ultrasonic bath which yet again, requires to stop the operation of the structure for fouling removal process to commence. Application of high power ultrasonic transducers are proposed in this work as a means to remove fouling on a structure whilst in operation. The work presented in this paper consists of the designing of bespoke high power transducers, transducer array design and development of bespoke power amplifiers to drive the high power transducers. The Polytec 3D Laser Doppler Vibrometer has been incorporated into this investigation to study the fouling removal process. Results shows the potential of using high power ultrasonic transducers for fouling removal in marine structures due to the wave propagation across the structure that is under excitation.