Norsk Hydro said that a 120-meter-long prefabrication facility at the yard is filled with the subsea production equipment, which will be remotely controlled at a sea depth of 850 meters. Supplier FMC Kongsberg and its subcontractors have been carrying out the operations that the equipment will need to perform when it is deployed over the next few months.
"Many people ask if such extensive testing is necessary, but we have found that the thorough preparations have revealed surprises, which we will now avoid encountering out at sea, said Per Magne Almdahl, an engineer with Grenland. "In that way, the costs of testing have already paid off many times over."
The production facility--called Hall C--is dominated by a 35-meter-long and 30-meter-wide terminal that is used to connect the production pipes running into the land-based facility at Nyhamna with two templates on the sea bed. The terminal is a so-called PLET--Pipeline End Termination. The PLET system in Hall C is a replica, which will only be used during testing. The PLET that will actually connect the 30-inch pipes from Nyhamna to the production equipment on the sea bed was already installed in the field last August.
"The replica is identical to the system on the sea bed, and here we are able to test that all the modules really can be assembled correctly," said engineer Øivind Leon Eriksen. Together with Almdahl, he has followed up the testing on Hydro's behalf.
During the testing, the task is to evaluate what can happen in a worst case scenario when installing the equipment on the sea bed. Everything from base frames to valves has been thoroughly tested. This includes, for instance, two huge valve modules that each weigh 130 metric tons and are to be mounted on the PLET system.
"In this work, it's actually important to have a negative attitude--all the time you have to base your work on what's the worst thing that can happen, and prepare the processes accordingly," said Eriksen. "When equipment is to be installed at a depth of 850 meters, you only get one chance. Here we get to test that all the parts really do fit together."
The production equipment will be installed on the field from the end of April until the end of the summer. Helge Hagen, an engineer who is in charge of this subsea operation, pointed out that the pull-in of the production pipes towards the terminal is one of the most important processes to be tested in the hall.
"This will be a critical moment during installation on the sea bed, and among other things we are testing how different degrees of incline for the pipes affect the operations we are to carry out at sea," Hagen said. "We also simulate as much as we can of other processes, such as so-called pigging, which is carried out during gas pipeline maintenance operations."
Hydro said this year's testing in Tønsberg supplements the work that was carried out last year, before the two sea-bed templates were installed on the sea floor.
"We are now approaching the end of an intensive test phase, and are looking forward to the equipment being installed on the field," concluded the head of Hydro's testing process in Hall C.
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