The effects from biological growth can be seen as a decrease in the recieved amplitude, like an SNR problem that gradually gets worse. The fouling will in most cases not affect the current velocities, but it will reduce the range of the instrument.
Update, January 2019: Biofouling - the problem and the solution.
Cleaning: We do not have a standard recommended transducer cleaning procedure. The typical answer however is that we realise barnacle has to be removed mechanically, but that we strongly advice against (of course) using sharp objects capable of harming the polyurethane surface. We also recommend to stay away from strong organic solvents such as acetone. Lime dissolving liquids can be used. Avoid scrubbing and high pressure washers. For soft bodied marine growth it is recommended to use soap and water. Although realising that barnacle can offer tough resistance we would also like to stress the importance of a patient and careful approach, keeping the use of mechanical force and sharp objects/tools to a minimum.
Prevent growth: Regarding antifouling paint, the important thing is that the paint is not too thick, otherwise the signal strength will decrease. We really do not know much about antifouling paints, but you can probably use most anti-fouling paints as long as it is not too (chemically) aggressive and contains no solids (metal flakes, etc) that could interfere with acoustic beams. Customers should be careful not to paint any anodes (if present) and to make sure pressure ports are not blocked. Also, when painting transducers, make sure to put just one smooth coat to make sure it doesn't affect the acoustic signal. There cannot be any air bubbles trapped between the paint and the face of the transducers.
We have heard from users that use the Trilux and they report that it is a great paint and it works well on both the Delrin plastic as well as Aluminium. It also works well for epoxy transducers.
The polyurethane transducers should not be coated with regular antifouling paint. One paint that can be mentioned for these transducers is this one from Seahawk: http://www.seahawkpaints.com/O...
Upon request, Jotuns tips is to paint the VM profiler (with bronze alloy head) the following way:
- 100 um of Penguard base
- 100 um of Safeguard
- 300 um of Seaquantum Ultra
As antifouling paint is not our speciality it is difficult to give a more accurate answer, but hopefully the above is of some help. If you suspect that your instrument has been cleaned to heavily, please contact Nortek for an evaluation.
A couple of instruments subject to biofouling