Subsea compressor passes latest tests

Siemens has completed the factory test program for its STC-ECO seal-less compressor system for subsea and “dirty” gas applications.

Offshore staff

ERLANGEN, Germany -- Siemens has completed the factory test program for its STC-ECO seal-less compressor system for subsea and “dirty” gas applications.

The company says this was a major milestone in the qualification program and for marinization of the equipment, in preparation for planned subsea processing applications in water depths of 3,000 m (9,842 ft).

The test covered thermodynamic performance including internal cooling, rotor dynamic behavior, motor performance, and stability of the bearing system. Siemens says the next-phase qualification program will focus on reliability testing of performance and mechanical robustness.

A future phase will take in wet gas such as liquid injection into the main gas stream to further endurance and robustness tests.

Repairs to subsea compressors cannot be performed in situ on the seabed, Siemens points out, as access to the equipment is both difficult and costly. Therefore, the units must be reliable and robust to ensure long service intervals.

The STC-ECO system incorporates a high-speed induction motor and multi-stage centrifugal compressor on one shaft in a single casing. Siemens claims equipment such as a seal gas system, lube oil system, or gearbox would only introduce reliability so has kept the number of components to a minimum.

In 1999, Siemens and Shell jointly developed the ECO-II (economic and ecological) compressor. During the fall of 2006, the prototype was deployed at the NAM Vires-4 gas field in the Netherlands. It was tested for over 20 months in onshore applications with dirty process gas, and a wide range of contaminants, including sand and water.

Following the field tests, the compressor has been re-designated STC-ECO and now operates as a standard machine for dirty-gas applications, with over 16,000 operating hours in the field.

08/30/2010

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