Qatar: Siemens Completes Qatargas LNG Mega-Train

Siemens Industry, Inc. announced the successful completion of the world’s largest onshore liquefied natural gas (LNG) compressor “mega-train” for Qatargas in the Middle Eastern country of Qatar. The last of the 72 Siemens ROBICON Perfect Harmony Variable Frequency Drives (VFD) was installed and brought online.

Qatar sits atop the world’s third largest gas reserves, and these new LNG projects have allowed the country to raise its overall LNG production capacity to 77 million tonnes annually thereby meeting the demands of global LNG buyers.

In addition to the 72 ROBICON Perfect Harmony Variable Frequency Drives, the Siemens’ scope of supply also included 72 VFD control houses and four 33KV switchgear. The first order for the initial 12 drives was placed in 2004.

The project, located in Ras Laffan Industrial City, some 50 miles north of Qatar’s capital, Doha, was five years in the making. “The culmination of this project is monumental, as it has involved the hard work and dedication from hundreds of Siemens’ team members across dozens of countries,” says Doug Keith, president of the Drive Technologies Division, Siemens Industry, Inc.

According to Agnes Armstrong, Team Leader and Manager of the Qatar LNG projects, the massive scale of the series of projects, in addition to the number of partners that worked toward its completion, demonstrated a true teamwork approach to showcasing Siemens products, applications and solutions.

“Our team continually worked with Qatargas to meet the customer quality and safety requirements, resulting in a job well done,” says Armstrong

The Siemens ROBICON Perfect Harmony 45-megawatt VFDs, manufactured in New Kensington, Pennsylvania, are being used on the main refrigerant compressors (MR, C3 & N2 strings) in the mega LNG train. These drives play a key role in the gas liquefaction process, allowing natural gas to be liquefied then transported to waiting tankers in the Persian Gulf.

The variable frequency drives control the speed/torque of large 45Megawatt motors/Generators used for starting the gas turbines and gas compressors strings. In addition to starting the gas turbines, Siemens ROBICON Perfect Harmony variable frequency drives also help the gas turbines run more efficiently while the train is operating during high ambient temperatures. The quantity of power generated by the gas turbines is dependent on the air temperature.

During the winter when the air is cool, the gas turbine can, at times, generate more power than the compressors need. The Siemens ROBICON Perfect Harmony variable frequency drives are able to direct this excess energy via the motor (acting as a generator) back to the electrical grid to improve overall energy use. To counter hot temperatures during the summer, these variable frequency drives can provide up to 45 megawatts of additional power to the compressor train to keep operations running smoothly.

Siemens ROBICON Perfect Harmony variable frequency drives were also selected for the project because of their high reliability. These drives also have the best electrical waveforms on the market, providing superior smooth rotational performance of the compressor and the highest waveform quality into the Qatar electrical grid system. This greatly reduces the harmonic distortion that can negatively affect electrical grid performance.

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Source: Siemens, May 12, 2011;