Turboexpander-compressor modifications at the Kollsnes plant in Norway

The challenge

In 1993, Rotoflow supplied three turboexpander-compressor trains with active magnetic bearing (AMB)-dry gas seal-purged bearing housings, per Statoil's request, for use in the Troll Project at the Kollsnes plant in Bergen, Norway. At the time, those machines (with a power-speed map of 5,000 KW at 7,000 rpm) were the largest turboexpander-compressor units with AMB available to the industry. Over the years, the nitrogen losses, which are typical for this seal arrangement, caused problems for the flare system.

The solution

In May 2000, Rotoflow was acquired by GE’s Oil & Gas business and commenced development of a high power turboexpander-compressor unit with active magnetic bearings. That same year, Statoil awarded expansion of the Kollsnes plant to Linde AG. In 2002, Linde contracted with GE to supply the Rotoflow high power turboexpander-compressor with AMB for this project. The specifications for the expansion project called for 14,000 KW at 9,000 rpm with labyrinth seal and pressurized bearing housings – a totally closed system. The main advantage of this design is that it does not require nitrogen purge, thereby avoiding the difficulties associated with the buffer nitrogen flow of the first three trains, and eliminating the problem of nitrogen consumption. Once again, this machine represented the largest turboexpander-compressor with Active Magnetic Bearings on the market.

The result

The turboexpander-compressor package was commissioned in late-2004/early-2005 and has been in continuous operation since March 2005. Statoil is completely satisfied with the system’s performance and operation without nitrogen purges. In fact, they are so pleased with the results they are now considering retrofitting the original three trains with a similar sealing system.

For more information, please contact:

Reza Agahi
reza.agahi@ge.com

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