Meeting lifting standards

The Heidrun FSU crane in Protea’s yard, Poland. Photo from Protea.

Protea has designed its largest crane to date for Statoil’s Heidrun FSU, a project that will aid the life extension of the Heidrun field.

Statoil is investing in the infrastructure of its Heidrun field in the North Sea, hoping the return will be an extension in life of the field until at least 2045.

One key expenditure has been in a new floating storage unit (FSU) for the field, currently being built by Samsung Heavy Industries in Korea. It will replace an existing two-buoy loading system on the field, from which purpose-built shuttle takers were used for offtake.

The new permanently-manned FSU will have a 30-year expected design life and is scheduled to be on location from early 2015. It will be permanently moored to a buoy, with oil offtake via shuttle tankers.

The FSU includes a new 55ton safe working load (SWL) crane, designed and built by Poland’s Protea, which has offices in Norway and fabrication facilities and offices in Poland.

“Statoil required a weight-efficient, high-performance offshore pedestal crane, that complied fully with EN13852-1, Crane N Notation and NORSOK regulations,” Tomasz Paszkiewicz, Protea’s CEO, says.

Cranes of this capacity and outreach are typically of a lattice boom construction, but for this application, Statoil specified a box boom type to ensure the crane was as compact as possible with the shortest luffing range.

The Heidrun FSU, schematic. Image from Protea.

As box boom cranes are generally heavier than a lattice boom equivalent, one of the key technical challenges was to optimize its overall weight. This required detailed analysis of the crane’s structure, using software developed by Protea, together with shell element analysis and bar element analysis. This process allowed Protea’s design to comply with code and meet the overall weight target, coming in at 165ton, including the pedestal and the staircase, or 125ton without.Two high capacity hydraulic rams are used for luffing the boom, reducing the overall height of the crane and making it suitable for use on offshore platforms where there are height limitations.

Statoil's Heidrun platform. Photo from Statoil by Harald Pettersen.

The crane’s total hoist height is 80m, with hoist speed in four-fall configuration being 18m/min (SWL 50ton), and 42m/min in one fall configuration (SWL 10ton). The outreach is up to 40m, with an unlimited 360° slewing range at 0.72rpm. Full boom luffing can be achieved in 80 seconds.

The crane met EN 13852-1 Offshore Cranes standard; DNV GL N Class standard; the latest NORSOK regulations, and Statoil’s internal requirements, Paszkiewicz says, making it “probably the highest specification offshore crane that has been delivered to date.”

While Protea has already designed a number of Ram luffing cranes, including 22ton SWL cranes for a pipelay vessel and a 33ton SWL riser handling knuckle boom crane for a semisubmersible drilling rig, this is the largest capacity ram luffing crane the firm has built.

Protea was founded in 2001 by Paszkiewicz and subsequently merged with engineering firm NTD Olesno in 2004, before opening a manufacturing and assembly facility in Ligota Gorna, Poland in 2008. The production facility was expanded in 2013, with the addition of a 26m-high assembly hall.

Heidrun was discovered in 1985 by ConocoPhillips in the Norwegian North Sea and has been producing oil and gas since October 1995 from a floating ten- sion leg platform with a concrete hull.

A total of 76 wells are planned on the main field, including 51 producers, 24 water injectors and one gas injector. The north flank of Heidrun was brought onstream in August 2000.

Samsung Heavy Industries is building the new FSO on Geoje Island, Republic of Korea. The unit is expected to be on location at the Heidrun field 1H 2015.