Mammoet performs load-in, transpooling of subsea cable offshore Saudi Arabia

UTRECHT, The Netherlands —Subsea cables provide critical communications and power links for offshore assets, but handling and installing these giant lifelines can be anything but simple, as in the case of a new subsea cable for an offshore project in Saudi Arabia. This in particular with marine engineering challenges to load in the 1,300-t cable basket for transpooling of the cable onto the offshore service vessel required specialist support from Mammoet if it was to be ready in time for installation.

The cable basket arrived on a barge to Jubail Commercial Port, where it then needed to be loaded in for transpooling and the empty basket loaded back out on the barge. However, the height difference between the barge and the quay meant thorough engineering across disciplines (e.g., marine engineering and transport) was needed to ensure a smooth, efficient load in operation.

Mammoet Project Manager Munawar Khan explained, “The cable basket needed to be loaded in for transpooling from the quay, as it could not be done safely from the barge. The spooling then is performed by rotating the cable basket on SPMTs in a circular motion.

“However, we were presented with a task to overcome the height difference between the deck of the barge and the quay for load-in and loadout operations. Our experience in handling large and heavy components—often weighing in excess of 1,000 t—proved critical in doing this effectively.” 

Mammoet engineers created a detailed load-in plan, which included a bespoke 50-m ramp, designed to accommodate the elevation difference while bearing a total load of more than 1,500 t (including the weight of SPMTs). The result was a pathway for 18 lines of SPMT to roll onto the barge, lift the basket and roll off onto the jetty. The spooling operation was then performed with the basket being rotated by the SPMTs, while typical spooling auxiliary equipment was used to manage the cable between the basket and the installation carousel.

With time of the essence, the Mammoet team worked in day and night shifts as the SPMTs were rotated during transpooling. The transpooling operation was completed in less than 48 hours, ready for transportation offshore.

This then allowed loadout to happen sooner, moving the empty cable basket by SPMTs back onto the barge via the ramp. In total, load in, transpooling and loadout was undertaken in far fewer days than the original timeframe given.

09.06.2022