GANGWAY & ACCESS SYSTEMS
FEATURE SPONSOR BRIDGING A GAP
“If you are good at building bridges, you will never fall into the abyss!” - Mehmet Murat Ildan, Turkish Novelist & Playwright
Accessing offshore wind turbine foundations during construction and operations has traditionally been achieved using fast, small and light ships (dubbed ‘CTV’ for Crew Transfer Vessel) coming from port to the foundation (sometimes multiple times a day), then pushing up against the boat landing fenders on the superstructure while the technicians and engineers step across to climb up the outside ladder. This has been termed ‘Bump & Jump’ and involves skill, both of the vessel master who needs to constantly monitor wind, wave and currents to determine when it is safe or not to make the jump, and of the technician or engineer who needs to make the transfer quickly when given the go ahead.
WHY JUMP WHEN YOU CAN WALK?
Recent years have seen the rise of a new foundation access approach. In particular on those projects further from shore (such as UK Round 3 or German North Sea) where prevalent weather conditions make ‘Bump & Jump’ access solutions unsafe and where return trips to port are not economically feasible due to the amount of time lost in transiting to and from shore, there has arisen a demand for high personnel capacity, offshore vessels with the ability to directly access foundations in high sea states.
This has heralded a new type of
offshore service vessel, known as the W2W (‘Walk-to-Work’) SOV (Service Operations Vessel). These high capacity vessels utilise advanced motion compensated gangways to create temporary ‘bridges’ between the vessel and the foundation, reducing the need to climb ladders before commencing their critical work. Siem Offshore Contractors’ 2011 concept of the “Siem Duo” of the cable lay vessel Siem Aimery and its installation support and W2W vessel Siem Moxie (see Issue 31), was addressing a need Siem Offshore Contractors had identified within the specific world of subsea cable installation: How to safely increase the windows of opportunity for getting personnel and equipment on and off the
foundations during the cable installation segment of the offshore windfarm construction as well as operation and maintenance processes (seen above in 2016 on the Nordsee One project). Since then Siem Offshore Contractors have transferred over 60,000 personnel across more than 15,000 connections using W2W gangways from four in- group owned and operated vessels (three of which are featured here) and learnt many lessons.
ONE SIZE DOES NOT FIT ALL
Lesson No. 1: not all foundation access requirements are the same. One project might only be accessible with a tall gangway, such as the Amrumbank West offshore windfarm was for the Siem Moxie (pictured above left). Whereas another
project may have a shorter foundation, meaning using a low access gangway, such as Siem Offshore Contractors had to with their Siem Garnet (pictured above right) during the construction of the Baltic 2 project.
Then of course there are those special cases, where the foundation fall into neither category, however requires special consideration due to e.g. the specific access point location, or the offset required between the vessel and the foundation such as can be seen in this picture of the Siem Marlin on duty at the BARD Offshore 1 windfarm.
GANGWAY TO SUCCESS?
Lesson 2: Gangways differ in capability. In the offshore oil & gas market, similar gangways have been utilised for many
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