Apr 27 | 2021
Engineering Challenges of Pile Installation Frame
By Malcom Ramsay
As offshore windfarms have grown in size in recent years, the scale of foundation pieces and complexity of installation has steadily increased, resulting in many new challenges in the transport of components and ever-greater engineering skill from breakbulk operators.
Multipurpose shipping line dship Carriers demonstrated its prowess in this field with the transport of a 750-tonne pile installation frame, or PIF, on behalf of specialist offshore services company Seaway 7.
The giant PIF unit measured 33.5 meters in diameter and 29 meters long and was shipped alongside other offshore and subsea equipment from Rotterdam in the Netherlands to Anping, Taiwan.
“Constant communication with all parties involved was the key,” Lars Feller, global vice president, dship Carriers, told Breakbulk. “We demonstrated our ability to handle projects like this during all stages of transport, while delivering safety and defining logistics by offering solutions to fully comply with very high offshore standards and requirements given by our clients.”
Headquartered in Hamburg, dship Carriers is an independent business unit within the family-owned deugro group. The firm operates a fleet of multipurpose vessels providing specialized breakbulk, heavy-lift, dry bulk and project cargo services for the oil and gas, wind energy and floating cargo industries. The group also operates offices in Houston, Tokyo, Mumbai, Shanghai and Singapore.
Having secured the project, the first challenge was selecting a suitable vessel for loading and unloading of the cargo, stowage and transport to Taiwan. Given the size and weight of the PIF unit, dship utilized its newly acquired F-500 multipurpose heavy-lift vessel Bruce for the project due to its extensive lifting capacity and storage.
“Bruce is one of three eco F-500 class vessels in dship’s current fleet. In addition to their huge versatility, low consumption and crane capacity of 500 tonnes, they also feature a designated heavy-lift area on deck with reinforced hatch cover pontoons,” Feller said.
Featuring a 75-meter-long main cargo hold, adjustable ’tween decks and various stowage options, the vessel proved perfectly suited for the cargo. However the size of the PIF still necessitated intensive engineering work prior to loading.
Small Footprint, Heavy Load
In total, the offshore renewables installation units had a volume of 36,964 cubic meters and an overall weight of 3,328 tonnes, making it difficult to load and store in one operation. To complicate matters further, the PIF had a small footprint and heavy weight, which required collaboration with a specialist engineering partner to plan the move.
“The development of the overall stowing and sea-fastening concept took several months and was conducted with the support of LOC Germany. We express our special thanks at this point,” said Hauke Bindemann, supercargo port captain for dship Carriers.
Based in Hamburg, LOC Germany is part of London-headquartered AqualisBraemar LOC Group, which provides engineering consultancy and derisking advisory for the renewable, maritime, oil and gas and power sectors.
The first step in this process was to design a special load-spreading concept with heavy load platforms for the hatch covers, and a team from LOC began detailed analysis of the units and stowage position to ensure success.
“The stowing and sea-fastening needed to be analyzed carefully beforehand in this challenging project,” said Jonas Schwebe, chartering manager for dship Carriers. Due to the enormous size of the PIF on the one hand and its limited footprint on the other hand, the stowage position had to be precisely chosen. We needed to eliminate any potential clash with vessel cranes as well as ensure the integrity of the vessel structure under motion-induced loads.”
To meet the challenges of stowing such a heavy cargo with such a small footprint, the partners additionally focused on preparing the ship’s decks to stow the cargo safely and to ensure a safe voyage of the cargo.
Adapt and Reuse
To be able to counteract the small footprint of the PIF’s legs, a grillage concept was developed to better distribute the load onto the main members of the hatch covers. To save costs, the plan was to utilize heavy-load platforms already available for load spreading. However, the existing platforms had to be reinforced locally to make them fit for purpose. “The heavy-load platforms will continue to be used after the completion of this project, making for more sustainable operations in the long run,” said Emek Ersin Takmaz, general manager and naval architect at LOC.
“The slotted shapes of the hatch covers were another restriction that had to be taken into consideration. For this reason, the heavy-load platforms also needed to be supported underneath by pre-shaped hardwood packs,” Takman added.
With a robust plan in place to support the weight of the cargo and prevent any damage to either the PIF or the ancillary cargo, the partners next studied the proposed route to ensure there were no additional risks. Detailed meteorological and oceanographic analysis was carried out to forecast the environment the cargo was likely to encounter.
“A detailed metocean study was conducted for the intended route and the season, and a motion response analysis was carried out to determine the motion-induced accelerations acting on the cargo. The calculated accelerations were then used for the structural calculations and sea fastening design,” Takmaz said.
This study provided extensive data on the forces likely to act on the cargo and resulted in additional preparatory work to protect the structure.
“Hook-over brackets (steel plates, designed as clip stoppers) were utilized as sea fastening devices. As a result of the structural integrity checks carried out by the aid of finite element analysis software, local reinforcements were required for the hatch covers and the vessel hatch coaming,” Takmaz said.
With a journey of more than 5,000 nautical miles from the Netherlands to Taiwan, the teams from dship and LOC next studied methods to avoid damage during the long voyage to Taiwan.
“Due to the size of the PIF, stowage with an overhang on port and starboard side was unavoidable. Therefore, in order to eliminate the wave-slamming forces acting on the skirts, the voyage had to be weather-restricted, which was achieved by a carefully conducted motion response analysis using hydrodynamic software,” Takmaz said.
As the plan was to use the PIF more than once during construction of the project, the team had to consider the effect of marine transportation on fatigue.
“Fatigue scatter tables were generated in order to conduct the related checks. To monitor the actual accelerations during the voyage, additional measurement devices (motion response units) were installed on the vessel so that the calculated values could be verified,” Takmaz said.
The final challenge for the move was to ensure safety of all crew and participants in light of Covid-19. As part of dship’s global Covid-19 strategy, measures were put in place well ahead of the move to ensure that risks for all employees were minimized.
“dship’s main challenge in connection with Covid-19 was to ensure attendance of all port operations with highly skilled personnel. dship managed this task with the help of our global network of own offices as well as our long-term partnerships,” Feller said.
Alongside the pre-planning engineering activities for the project, the team from dship also arranged approval from the classification society and on-board supervision of the whole reinforcement works to ensure a seamless preparation process prior to start of the loadout.
Following successful delivery of the cargo to Anping, in the south of Taiwan, at the end of last year, the final installation of the pin piles was executed by Seaway 7’s vessel Seaway Yudin. The Seaway Yudin is engaged on several offshore renewable projects in Taiwan, including the upcoming Formosa 2 wind farm, which will be one of the largest wind farms in the Straits of Taiwan, generating 376 megawatts and involving pre-piling and installation of 47 jacket foundations.