Planning a Medium-Deep Water Mooring for Small Data Buoys
Note: NexSens Technology supplies mooring hardware to support user-designed systems but
does not endorse any particular mooring strategy for any specific application and does not take
responsibility for mooring performance or damage resulting from mooring failure.
While many medium-deep water (>100m depth up to approx. 1000m depth) monitoring projects require
large buoy platforms due to sensor loads and corresponding power requirements, there may be some
cases where a smaller buoy platform is desirable. This can facilitate measurements from a small
package of power-efficient sensors where only near-surface (<50m) measurements are required and
provide a solution that is easier to lift and handle by project personnel.
By small data buoys, we are generally referring to CB-Series buoys up to and including the CB-450
model. While these are small and light enough to lift manually by 1-2 persons depending on the model, a
medium-deep water mooring system will generally have a sizable anchor weight. As such, a suitable
vessel equipped with winch and crane is strongly recommended for lifting and controlled release of
equipment to avoid injury to personnel or damage to equipment.
Whereas two-point moorings with suspended sensor lines are often a viable option for shallower
applications, medium-deep water moorings will typically be single-point due to the required mooring line
length. This means that suspended sensors will be mounted along the primary mooring line, and special
care must be taken in the design to ensure that twisting or stretching of data cables does not take place,
as this can lead to failure even within a short timeframe.
Some general suggestions and points for consideration when planning this type of deployment are
described in the following sections:
Mooring Line Length Calculation
Chains for Controlled Movement vs. Ballast Weight
System Maintenance
Mooring Line Length Calculation
In order to determine the appropriate mooring line length, it is first necessary to have a fairly accurate
water depth measurement at the deployment site and overview of the expected water level changes.
The length of the mooring line determines the potential drift radius of the buoy. The maximum drift radius
can be theoretically calculated using Pythagorean theorem as illustrated in the diagram below and using
the following formula:
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Summary of Contents for CB-450
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