Delicate drum dance

15 April 2008

Jumbo Javelin is one of the largest vessels the Jumbo fleet

Jumbo Javelin is one of the largest vessels the Jumbo fleet

Specialist contractor Jumbo has transportedcomponents of a new petrochemical plant some of the biggest and most challenging Son the Red Sea near Rabigh in Saudi Arabia. The challenge began in May 2005 when Japanese Gas Corp (JGC) contacted the office of Jumbo Japan. JGC was the engineering contractor engaged by plant owners Saudi Aramco and Sumitomo Chemical.

A transport solution was needed for components of a catalytic cracker used in the production of propylene. The cargo consisted of an 860 tonne reactor, 37 m long and 17 m tall, and a 1,054 tonne regenerator of about the same dimensions. In addition there was a 175 tonne reactor riser and a 190 tonne withdrawal well.

Jumbo Javelin, one of the biggest ships in the Jumbo fleet, was chosen for the job. Load weight meant that the reactor and regenerator had to be tandem-lifted between the ship lift mast cranes. To make space for the regenerator, the reactor had to be skidded at Antwerp from the landing position in between the cranes to the ocean transport position on the front weather decks.

From the beginning it was clear that the lifting and the skidding processes were going to be a challenging operation. Considering the size of the reactor its shell was very thin (30 mm on a diameter of 15 m) and, therefore, fragile and vulnerable to damage. During lifting, the clearances between the reactor, cranes and ship were minimal compared to its dimensions. Concerns were expressed regarding possible movements of the reactor saddles during skidding, which could cause unacceptable forces on the thin reactor shell.

Securing the contract

At Jumbo headquarters in Rotterdam, the Netherlands, the commercial department was appointed to make JGC a competitive offer and land the order. Together with the inquiry engineer for this project, they investigated the grade of difficulty and estimated the manpower and hardware the job would take. This resulted in a combination of calculations, estimations and puzzling with the vessel schedules. The time windows of transportation jobs like this narrow through time like chutes, which have to converge perfectly in the end.

A final price was determined based on this information, together with other demands of the potential client, for example, the desired planning flexibility. JGC also asked other heavy lift shipping companies to quote the job, but Jumbo was chosen for several reasons. First, Jumbo was one of a few companies capable of handling the huge components at all. Jumbo even had two vessels capable of transporting the two big components together, allowing them planning flexibility. Second, Jumbo had expertise in the seagoing and landside preparations for this kind of project.

Voyage preparations

After the inquiry was approved and the contract signed, the project engineer started with the technical preparations. The first thing to look at in the project engineering was the stowage plan. Where would the cargo be positioned, what would be the loading and unloading sequence? The next step was the stability analysis and, after that, the strength calculations. The final stage in the engineering process was the sea-fastening plan, based on the expected maximum accelerations in North Atlantic winter conditions.

When the technical preparations where finished the operations department and the port captain worked out the project planning and organisation. Agents and stevedores were appointed, preparations of the vessel, the quay and the loads were planned, documents were a rran g ed, and all involved parties were informed about the final schedule and time window of the vessel. It is essential for the success of a project like this that every party involved has the right information at the right moment and that everythin g is planned very accurately.

The reactor was brought on a barge from the factory in Willebroek alongside Jumbo Javelin. This was a challenge in itself because the combination had to fit through a narrow bridge with such small horizontal tolerances that steel slide guides had to be installed on deck for a safe passage.

On site the port captain was responsible on behalf of Jumbo for the loading operations. After the barge arrived alongside, the reactor was loaded using the two ship cranes, directly on the skid shoes. The strong and unsteady wind in combination with the small clearances made this a challenging operation.

Skidding

The skiddistanceon thedeck of the Jumbo Javelin was 31 m and it was done within the planned three hours. The system consisted of skid tracks with Teflon pads, skid beams with a stainless steel bottom to reduce friction on the Teflon pads and hydraulic push-pull systems.

After the skidding operation was completed, the flat jacks were fully retracted to retrieve the skid shoes and install the remaining load supports. Finally, the deck was cleared for the regenerator and work started on the heavy sea fastenings Next for loading was the slightly larger and 200 tonnes heavier regenerator. It was also loaded using the ship cranes in tandem and secured on deck. Afterwards the same was done with the riser and withdrawal well components. When the sea fastenings had been checked and double-checked, Jumbo Javelin departed for the voyage to Rabigh, where she arrived on schedule twelve days later.

In Rabigh, on the coast at the edge of the Saudi Arabian desert, the same procedures were followed in reverse order. A challenging job was completed another demanding client was satisfied. The first propylene will leave the Petrorabigh plant in the second half of 2008.

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