Integrating Fuel Injection Colfax develops, installs integrated fuel oil system in power plant

Colfax developed an integrated fuel oil injection system that includes the motor, filter and pumps for Mitsubishi Heavy Industries’ M501 dual-fuel gas turbines installed at the McDonough Plant in Smyrna, Georgia, U.S.A. The McDonough Power Plant in Smyrna, Georgia, U.S.A., recently underwent an update, converting units 4 and 5 from a coal-fired plant to a gas turbine combined-cycle plant with the intent to reduce the plant’s overall emissions.

While the plant will run primarily in natural gas, the three 840 MW M501G gas turbines from Mitsubishi Heavy Industries (MHI) are dual-fuel capable, offering the ability to operate on a secondary liquid fuel oil supply  and to utilize a main fuel pump injection system in lieu of gas in the event of an interrupted natural gas supply. As part of its renovation, MHI was seeking a way to consolidate the installation of the plant’s fuel oil system by utilizing a single source supplier.

The turbine manufacturer turned to Colfax, which develops integrated fuel oil systems for power plants. By developing a packaged module for the system, the plant developer can forgo separate installations and packages for each section of the fuel handling system. “The supply and integration of the filter, the pump, the relief valve and all the other components were often done on-site with various suppliers. If you were looking to minimize the fabrication costs at those interfaces, then you would look to combine them to one large skid with a single point contact,” said Jim Healey, project engineer at Colfax.

For the heart of the system, a rotary positive displacement three-screw pump was chosen for the main fuel oil injection pump, which works well in lower viscosity applications, as well as higher viscosities like some crude oils and residual fuels, said Colfax. Colfax’s system is driven by a 373 kW electric motor built to customer specifications. It features two customer inlet connections, one for the operational conditions and the smaller for flushing activities with isolation valves to direct flow. The flow passes through a Hilco duplex filter, and from the filter enters the pump. The system provides connections for fuel oil discharge, relief valve discharge and drain discharge to customer specifications.

The pump has a normal discharge pressure of 100 bar and delivers a flow of approximately 1362 L/min. The system is protected by a Crosby relief valve with a setting at 120 bar. The pump inlets are supercharged to allow operation at faster two-pole motor speeds, said Colfax. Colfax’s package is equipped with instrumentation including suction and discharge pressure gauges and pressure switches to ensure adequate flow is provided and the pump is protected from cavitation. The filter is also outfitted with a differential pressure indicator transmitter to measure the cleanliness of the filter.

The fuel system sits on a 6.1 m base and uses less than 4.6 m of stainlesssteel piping to connect the components. Because the unit is installed outdoors, it was constructed using various stainless-steel components and weatherized instruments and motor.

Source: Diesel & Gas Turbine Worldwide

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