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NORTEK
9 Maintenance
9.1 Signature Sensor
We recommend a regularly scheduled procedure which will act as a preventative measure to ensure your
instrument continues functioning as intended. The following sections can be used as a maintenance
guideline for the components that may be exposed to wear and tear.
•
When cleaning the external surfaces use a mild detergent and be extra careful with the
transducers.
•
Check the pressure sensor and remove any dirt from the holes in the lid. Be careful when
opening the pressure sensor cap as it is easy to dent and damage the sensor.
•
Be careful when cleaning and lubricating the connectors.
•
When opening the instrument, great care should be taken to keep the sealing surfaces clean and
protected from mechanical damage. Always keep water out of the open housing. The grounding
point should always be free from biofouling.
9.2 Biofouling
Current profilers used in long term monitoring projects will become covered with biological material.
Eventually, the growth can become strong enough that the transducers are blocked, and the profiling range
is reduced. To know when to maintain the instrument it is best to monitor the long-term variation in the
amplitude data. This parameter varies with short time scales (depending on suspended sediment
concentration, zoo plankton, bubbles, etc.), but biological growth (especially barnacles) adds a long-term
downward trend that can be monitored. The profiling range gradually goes down as the growth on the
sensor increases. At some point, the signal strength will be too low to get the desired profiling range.
Through experience you will gain knowledge about how long it takes before the transducers are covered
and this information can later be used to set regular maintenance intervals where the transducers are
cleaned.
When the instrument leaves the factory, the surfaces are quite smooth, and it will take some time before any
growth starts. After the first cleaning, the surface is rougher, and it becomes easier for new material to grow.
Typical maintenance intervals are 6-12 month, but the growth rates vary a lot with the geographical location,
water temperature, season, and deployment depth. In general, heavy growth is seen in hot and shallow
areas. Cold- and deep-water areas see very little growth so maintenance can be less frequent.
To clean the transducer we recommend not to use strong organic solvents such as acetone. Barnacles have
to be removed mechanically, but we strongly advise against using sharp objects capable of harming the
surface.
9.2.1 Antifouling Paint and patches
The important thing regarding painting transducers is that the paint is not too thick, otherwise the signal
strength will decrease. 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. Anodes and
pressure ports should not be painted. For permanent hull mountings on vessels with a low maintenance
interval, Nortek advices to use antifouling patches. These consumables can be purchased via the
Nortekgroup web shop. The patches double the standard cleaning interval and a diver can quickly clean the
patches from marine growth.
9.3 Instrument Care
All Nortek instruments are intended for use in water. Other fluids may have an adverse effect on the plastic
materials used. For prolonged storage at elevated temperatures close to the specified limit, or when
temperature variation is uncertain, it is recommended that the screws securing the end cap be loosened in
order to minimize the risk of any deformation due to temperature/stress over time.
