Environmental Engineering Reference
In-Depth Information
14.3 OPERATIONS AND MAINTENANCE OF
OFFSHORE SYSTEMS
No matter what monitoring systems and platforms are used, confidence in the data col-
lected in a resource assessment campaign depends on having an effective operations
and maintenance program. The fundamentals of such programs are the same for off-
shore and onshore applications. However, the offshore environment makes operations
and maintenance a more challenging and costly task. The following section focuses on
how the operations and maintenance of offshore stations differ from typical practices
for land-based stations.
14.3.1 Site Visits
Visits to offshore monitoring stations are usually conducted in small- to medium-sized
workboats, depending on the scope of the activity to be performed. During the winter,
in cold climates, it may be necessary to use an ice-breaking vessel. When visiting large
stations, and especially far offshore, it may be wise to use a helicopter (assuming the
station is equipped with a suitable helicopter landing pad). Helicopters reduce travel
time and can therefore increase the time on site.
Whatever method is used, the weather is always a concern, and it is essential that
weather and sea-state forecasts be consulted when planning offshore site visits. In
general, the maximum sea state for accessing offshore platforms from a workboat
is about 1.5 m; the wave tolerance can be even less when personnel or equipment
need to be transferred between the vessel and a platform or other offshore structure.
Helicopters fly above the waves but are susceptible to high winds. For these reasons,
it can be difficult to find a window of opportunity for an extended visit during those
times of year that have the strongest winds and greatest storm activity (winter, in most
offshore wind development areas). If possible, major maintenance activities should be
scheduled during the months when the wind and sea state are normally calmer.
14.3.2 Operations and Maintenance Procedures
Many of the maintenance procedures for offshore monitoring stations are the same as
those for onshore stations, although they can be more complicated and expensive to
carry out. For one thing, most offshore towers cannot be tilted down like the guyed,
tilt-up towers commonly used on land. This means that certified tower climbers must
perform all the up-tower work. Their ability to do this safely and effectively depends
on the site conditions.
The amount of routine on-site maintenance that is needed depends on the mon-
itoring equipment. Self-supporting masts with standard meteorological sensors and
data loggers generally require the least maintenance. As is the case on land, it is
recommended that wind vanes and cup anemometers be replaced on a regular basis
(no less often than every 24 months), as part of a preventive maintenance program.
Both lidars and sodars typically require more frequent maintenance and repair visits
than do towers, although it can be expected that as manufacturers deploy systems
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