Active Magnetic Bearings Provide Harsh Conditions Solution
Russian oil & gas company produces a compressor station to maximize pipeline capacity
By Richard Shultz, Waukesha Magnetic Bearings
Published in Pumps & Systems, April 2014
With more than 20 years of experience in the oil and gas industry, Lukoil, a Russian oil and gas business, aspired to expand its oil and gas fields. For the expansion, Lukoil selected the Bolshekhetskaya depression in West Siberia, where large deposits of cenomanian gas lay.
Developing and constructing a compressor station to connect the fields would increase the total capacity of the pipeline. The compressor design had to produce a high discharge pressure. In addition to the pressure gain required to compensate for the piping frictional losses, the discharge pressure of the compressor also supports a refrigeration process applied to the gas at the plant outlet.
This refrigeration process, based on a throttling principle, is required to cool the gas sufficiently to keep the buried piping temperatures from thawing the permafrost. The permafrost helps maintain a stable support for the buried piping.
Lukoil partnered with Sumy Frunze, an oil and gas equipment manufacturer, to develop centrifugal compressors that could withstand the frigid Siberian conditions. The compressors would allow the station to pump 12 billion cubic meters of gas per year to another station, furthering the central gas pipeline of Russia. Providing such high compressor discharge pressures with reasonable drive power requires compressors with high efficiency.
The high efficiency was achieved with a compressor rotor shaft with a high slenderness ratio. This high slenderness ratio allows high efficiencies but results in a flexible compressor rotor shaft. The Lukoil compressors have the most flexible rotors ever equipped with magnetic bearings. The processing power and advanced control algorithms provided by the bearing manufacturer’s electronic controller were required to make these machines a success.
The bearing manufacturer provided its multiple coordinate control (MCC) algorithm to stabilize all compressor rotor natural frequencies, with robust stability margins.
After installation, the technology performed successfully. Within the centrifugal compressor, the magnetic bearing technology provided savings in energy, ecology and the total cost of ownership for Lukoil.
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