Undersea cables are critically important to small and isolated islands unable to generate their own energy needs. Places like the Isles of Arran, Mull, and Coll off the west coast of Scotland rely on undersea cables to keep their population connected. Two Rotrex Winches engineers journeyed to these Hebridean Islands to accompany two winches on a project. They were replacing power cables that had reached the end of their service life between Mull and Coll. Before taking part in a similar pull to connect mainland Carradale on the Mull of Kintyre to Arran.
The main challenges the engineers faced were weather and time. The longer the vessel is in the water the higher the costs incurred. Poor weather meant the cable laying vessel would be unable to do its job. It was important to use the brief fair-weather windows to pull the cables across the water quickly.
The winches for the Mull to Coll pull needed to be positioned close to the shoreline to ensure minimal disturbance to the surrounding area. The lack of access with no roads leading directly to the location meant that towing the winches into position wasn’t possible. The sensitive beach environment and nearby fields and scrubland made appropriate anchoring for the winches particularly important.
It was the job of the Rotrex engineers to deploy and operate the winches safely and efficiently. The winch wires needed to be securely attached to the cables and careful monitoring of the pulls was necessary to ensure that the cables were not damaged either by the environment or by excessive pulling forces.
The pulls on the Isles of Mull and Coll used two winches with a 10t WLL (Working Load Limit). Equipped with rubber-tracks and a remote control, the engineers used remote controls to negotiate the winches across the difficult terrain. They were able o get to where they needed to be with minimal difficulty and little disruption to local wildlife.
They also inserted Ground anchors into the soft earth immediately behind the machines to secure each winch into position using substantial chains.
The cable laying vessel was geo-positioned approximately 300m off the shoreline and each tracked winch was located around 200m up the beach.
At first light our engineers paid the winch rope out to the vessel and connected to the new power cable. Floats were attached to the cable as it came off the vessel and was pulled ashore using the winch. When the cable arrived at the beach the floats were removed, and the cable was winched the remaining 200m.
The team required a larger 15 tonne capacity winch on the Isle of Arran as the pull was more complex and the distance over the water to Carradale was further than the Mull project. The Rotrex engineers used the brief windows of time they had, to do everything quickly and safely Keeping within the schedule and budget.
1x 15t Winch