As the reputation of its gas turbine cleaning system spreads, Gas Turbine Efficiency (GTE) is expanding its worldwide business. Recently it established an office in Houston, its first outside Sweden. Its main market in the US currently is the power sector, but the company's offshore business is also growing steadily. Its most recent deliveries to this sector were two systems for Statoil's Statfjord and Gullfaks fields in the Norwegian North Sea.
Regular cleaning of turbines can significantly improve their performance. In offshore turbines, dirt deposits consisting mainly of salt and hydrocarbons build up quickly. This causes inefficient use of the fuel, so that more is required to achieve the necessary power output, in turn adding to costs and increasing CO2 emissions.
GTE has developed a high-pressure or direct injection system. Compared with conventional low-pressure systems, high pressure creates finer droplets in a very dense spray. As a greater volume of water passes through each nozzle, fewer nozzles are required to transmit the same water volume. As applied to a GE LM2500 turbine, for example, the GTE system has five nozzles compared with 22 nozzles for a low-pressure system. Accordingly, the GTE system is easier to install and maintain, including flexible hoses for connecting the water supply to the nozzles.
The technique is also well suited to online washing. As contamination builds up quickly, operators are encouraged to clean their machines by means of an online wash at frequent intervals – in some cases every 24 hours. Online washing is not as efficient as offline washing, but the latter has the drawback of involving several hours' downtime while the turbine is switched off and allowed to cool.
GTE's system produces droplets with a uniform size of around 100 microns. They are neither big enough to cause erosion damage to the turbine blades during online washing nor so small as to get blown away in the air flow instead of impacting the deposits. One operator was able to put back the offline wash by 4,000 hours through regular online washing, the company says.
The system has undergone a series of tests by Statoil using a turbine from a North Sea platform. These verified that the washing process does not merely move the dirt at the front to the rear section of the turbine, but also removes it completely from the machine. Statoil was satisfied by visual inspection carried out with a boroscope that salt and hydrocarbon deposits visible prior to the cleaning had been removed.
For more information contact Carl-Johan Hjerpe, Gas Turbine Efficiency. Tel: +46 8 760 8550, Fax: +46 8 760 8560, [email protected], www.gtefficiency.com
