The 2013 Middle East Turbomachinery Symposium (METS) exceeded our expectations, said Abdulaziz Al-Naimi co-chairman of the METS Advisory Committee with co-chairman, Dr. Dara Childs, Leland T. Jordan professor of Mechanical Engineering at Texas A&M University.

“With METS we are establishing a platform of knowledge in this region to support the dynamic oil & gas industry,” said Al- Naimi, Manager of the Operations Business Department, RasGas Company, Ltd.

Indeed, Qatar has witnessed the rapid development of its natural gas industry and is now one of the world’s leading producers and exporters. Converting natural gas to liquid fuels has required the development of some of the world’s largest turbomachinery facilities. And today, observers agree, the Middle East is the center of installed and operating turbomachinery.

“The organizers are planning another METS event in two years,” said Al-Naimi. “High officials would like the show to continue.”

“This symposium upholds the nation’s commitment to research education and knowledge sharing in alignment with the vision of both his highness Sheikh Hamad Bin Khalifa Al-Thani, Emir of the State of Qatar, and her Highness Sheikha Moza Bint Nasser,” said Dr. Mohammed bin Saleh Al-Sada, Minister of Energy and Industry Chairman & Managing Director of Qatar Petroleum.

Among the many lectures presented at METS 2 were: Inlet Fogging and Overspray Impact on Industrial Gas Turbine Life and Performance; The Influence of Thermal Loading on the Leak Tightness Behavior of Horizontally Split Centrifugal Compressors; and Impact of Degradation on the Operations Behavior of a Stationary Gas Turbine and the Associated Compressor.

The first lecture, presented by Klaus Brun, Manager at Southwest Research Institute and a contributor to Myth Busters in Turbomachinry International, focused on the use of fogging and overspray on a GE Frame 5002, 35,000 hp industrial gas turbines.

Operating experience has shown lessthan- anticipated power increase and almost no efficiency change and rapid degradation, he said.

The paper, co-authored by Rainer Kurz, System Analysis Manager, Solar Turbines, Inc., also a contributor to Myth Busters, Marybeth Nored, Apache Corp. and Joseph Thorp, Aramco Services, showed that total power and efficiency degradation exceeded 10% at the time of rotor overhaul.

Turbine performance los

s The largest loss of performance (about 70%) was due to blade erosion and rotor clearance widening. Both these effects were attributed to the water overspray operations of the gas turbines. Surface fouling and pitting also contributed about 20% to the total performance degradation.

For the given site conditions, the fogging and overspray system provided a gas turbine performance boost of about 2% to 5% in power and less than 0.5% in efficiency. Of this performance gain, fogging accounted for about 85%, while overspray only provided 15%. The principal findings of this study showed that, while the fogging worked, the performance degradation due to water overspray negated most performance gains after only about 24,000 hours of operation.

The presentation also covered the fact that the on-line and off-line compressor washing program was not fully effective, as hardened deposits of salts, carbon and sulfur were found on the compressor rotors. Also, infrequently performed solid washing of the gas turbine compressors caused significant blade leading- and trailing-edge erosion throughout the compressors, opened blade clearance gaps and removed corrosion protective coatings from the compressor blades. The detrimental effects from overspray and water washing can be mitigated by more frequent inlet filter cleaning and water quality improvement.

The second paper, by Yves Bidaut, Manager Mechanical Development, MAN Diesel & Turbo Schweiz AG, addressed centrifugal compressor applications in the chemical process industries. Beyond the decision about the type of manufacturing (cast or welded) or about material selection, one of the utmost issues regarding compressor design lies in the leak tightness of the flanges.

To ensure proper design with respect to integrity of stress and tightness under test and operating conditions, several finite element analyses (FEA) and resulting criteria have been developed by OEMs.

Furthermore, to demonstrate leak tightness, the casing is subjected to a hydrostatic test (1.5 times maximum design pressure) prior to the assembly of inner parts and rotor. This procedure is considered sufficient for demonstrating casing integrity, tightness of operation and accuracy of the FEA.

The third paper by Wolgang Kappis, Compressor Expert, Alstom, addressed the causes impacting degradation rates for industrial gas turbines. The paper focused on compressor and gas turbine performance parameters for degraded engines with varying ambient conditions. A simplified computational fluid dynamics (CFD) model was applied, capable of simulating certain degradation rates for every individual compressor blade row.

Two basic case studies were shown: the first addressed filter clogging; the second focused on compressor blading degradation, while assessing different fouling distribution rates. The case studies were substantiated and supported by field measurements.

An empirical model was developed to simulate degradation effects for clogged filters and fouled compressor blading. It was concluded that fouling rates, and even compressor design, have a significant impact on gas turbine degradation. Fouling rates are site- and engine-specific due to local ambient and applied operating.