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Monitoring Kelp with Custom Subsea Shackles and Data Loggers

Posted on 10 February 2022

Monitoring Kelp with Custom Subsea Shackles and Data Loggers

Dynamic Load Monitoring (UK) Ltd (DLM) has designed and manufactured specialised load monitoring and data logging equipment for an R&D project by sustainable organisation, Kelp Blue, whose aim is to grow and manage large-scale kelp forests. Kelp is a type of large algae seaweed with many sustainable capabilities such as: feed for livestock which helps to reduce greenhouse gas emissions, medicine and textile fibres which support the need for sustainable products. DLM’s innovative custom designed equipment will be an integral part of Kelp Blue’s floating forest and sustainable vision.

Kelp Blue is managing a kelp forest off the coast of Namibia and came to DLM, who frequently design and manufacture specialised equipment for various subsea and offshore applications, with a proposition to construct equipment for structural monitoring purposes. In the initial design stages, spokesperson Ferdi Knoester, Project Engineer at Kelp Blue requested subsea load monitoring devices to monitor the load tension on mooring lines on a floating structure which is tethered to the sea bed.

The devices sent to Namibia include six of DLM’s DL-3.0 Subsea Data Loggers mounted onto three cabled Subsea Shackle Load Cells, which are some of DLM’s specialised equipment. The Subsea Shackle Load Cell is used on applications such as subsea moorings, subsea vehicle tension monitoring and anchoring tension monitoring. The Subsea Data logger is a proprietary data logger design for use on applications such as array cable monitoring, monitoring of subsea acceleration and measurement on offshore structures, including wind turbines. The DL-3.0 is used for long or short term deployments on offshore and subsea structures; a key feature of this Data Logger is its ability to monitor the weather conditions, specifically the acceleration of waves, which is helpful for matching computer modelling scenarios against real world conditions.

Kelp Blue created a pilot trial via a computer generated model of the mooring lines to investigate the tension loads on their floating structure. In order to confirm the tension loads on the computer model, DLM were employed to custom build subsea load cells and data loggers. The requirements for the monitoring equipment were as follows: to have a 25 year lifetime, a deployment depth of 20 metres and the capability to observe data for long periods of time. Due to DLM’s unique ability to custom design specialised equipment, these requirements, as well as the environmental challenges that were indicated with the project were carefully understood and designed accordingly.

Chris Scrutton, Technical Manager at DLM said: “We were really interested when the quote came in for this job as it was our first R&D project for the aquaculture industry, specifically a Kelp farm. We were able to use our standard subsea equipment with modification to fit the structural monitoring brief. Kelp Blue needed specialised equipment in order to prove the tension load on the mooring lines of their floating structure, therefore, we custom built data loggers to monitor the load.

Some of the challenges that came with the project were the requirement for the data logger to be simple enough for divers to collect the data on a short dive time. Therefore, we designed the data logger with the application in mind, specifically using wing nuts, making sure they were easy to undo in a short amount of time and more accessible to take off if the diver had gloves on.

During the design stage, the packaging of the data logger and mounting it onto the subsea shackles was challenging, our design engineers overcame this problem by specific designs of the subsea pod and 3D printing internal parts of the housing, making sure it is secure.”

DLM are leading the way in the design and manufacture of custom equipment for the offshore and subsea industries, with aquaculture a first, sustainable projects seem to be no stranger to them. With past projects in the renewable energy industry including the monitoring of array cables for an offshore wind farm and future projects including solar array.