Maintaining our autonomous Aids to Navigation systems

Even though autonomous skids like the above, typically are a temporary Aids to Navigation (AtoN) solution, often our systems are deployed for more than a year. In general, unless specified differently by our clients, we design systems for which we advise a once-a-year maintenance visit.

Based on our experience, the key equipment of an AtoN system (lanterns, fog signal, fog detector and Aviation Obstruction Light (AOL)), actually do not need any maintenance. Although it does not hurt to clean the lenses of the lanterns, to get rid of salt and possible bird droppings. After 3-4 years it is also recommended to re-calibrate the fog detector.

As far as the batteries are concerned, typically they do not require any maintenance at all, but they might need to be replaced after 6-7 years, provided that the charge controller is working properly and the batteries are not over-charged or depleted too much.

The components we use in the control panels are of high quality and do not require maintenance. Don’t expect to replace any broken items over the first 8-10 years or so, unless glass fuses are used (which we normally don’t). It is advisable to keep some components in stock, just in case, such as circuit breakers and relays. On the other hand, these are off the shelve items, so order them today online and you’ll have them delivered the next day.

Remote monitoring equipment is very reliable and the firmware can be updated remotely. Normally, this equipment does not require any maintenance. As we have experienced, a tripped circuit breaker may prevent remote updating and rebooting, in which case the circuit breaker needs to be closed manually during the next scheduled visit.

So, why do you need to schedule a maintenance trip then? Easy: the PV modules. Depending on the circumstances, PV modules might require a good cleaning in order to perform well. Furthermore, the PV modules are exposed to wind and in fact the most vulnerable part of the skid. I have seen PV modules being hit by birds and consequently being severely damaged. Very strong winds may also damage the PV modules and can cause vibrations, which may cause slack in the fixings.

Whether or not the PV modules need to be cleaned, primarily depends on three factors: the presence of birds on the platform, exposure of the PV modules to salty spray and the amount and interval of rain.

Obviously, if the platform is visited by many birds, the odds of the PV modules getting covered in bird droppings is rather high. However, if there is sufficient and regular rain fall, the modules will actually be cleaned. The same applies if the PV modules are exposed to spray (when installed on lower decks of the platform for example), rain will clean the PV modules.

When using PV modules, keep in mind that a small patch of dirt on the “wrong” place on a PV module, may severely reduce the performance of the panel. During an FAT we put an A4 sheet of paper on various locations on a PV module. There are spots on the PV module, which when covered, results in losing the entire capacity of the PV module. This is also the reason why shading is a very important factor to keep in mind when chosing a location for the skids. Cleaning PV modules therefor is something to take seriously. It does not necessarily matter how much dirt build-up there is, it is important where on the PV module the dirt has built-up.

Skids with clean PV modules after 4 months in deployment – September 2017. Rain has cleaned the PV modules, despite presence of birds (see droppings on helideck)
The same skids 8 months later, in the middle of the dry summer in 2018 (July). Lack of rain prevented the PV modules from self-cleaning. A helping hand is required.

In the Netherlands, there is typically sufficient rain in wintertime to clean the PV modules properly. However, in a very dry summer, like we have seen in 2018, it is very likely that the PV modules need to be cleaned once a year. A soft broom, fresh water and around 15 minutes per skid is all it takes. And while you’re at it, check the fixings of the panels as well.

Cleaning PV modules – not the nicest job in the world. Use water to prevent creating dust…

Obviously, as you are already on the platform, perform a full system test, just to check everything is indeed working as it should. And should a diode, relay or circuit breaker – against all odds – show odd behaviour, just replace it. It’ll take only a few minutes to do so.

Most of our clients are very experienced in working with fixed AtoN equipment, since this kind of equipment is present on all offshore structures and they have worked with them for decades. Autonomous AtoN systems are different though and we always recommend to have them commissioned and maintained by us. And once they have brought back to shore? We’ll prepare them for stocking, so they are ready for use whenever required for the next job.

About robinjansen

MD of PC Jansen Marine Agencies BV, agents for several international manufacturers of equipment to the offshore and marine industry.
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