Method for detecting leaks in a fuel circuit of a gas turbine fuel supply system

A method of testing a fuel supply system of a gas turbine, comprising:

• isolating the fuel supply system from a liquid fuel source with a flow control valve positioned upstream of a compressed gas supply;
• pressurizing the fuel supply system from a downstream side of the flow control valve to an upstream side of a check valve with a compressed gas from the compressed gas supply to a target pressure, wherein the target pressure is less than an opening pressure of the check valve, whereby the check valve does not open at the target pressure, the check valve disposed downstream from the compressed gas supply and upstream from a combustor of the gas turbine;
• aiming a receiver portion of an ultrasonic detection device proximate to at least one fluid coupling of the fuel supply system between the flow control valve and the combustor, wherein detection of an increase in sound level or a popping sound at the fluid coupling is indicative of a leak at the fluid coupling and wherein not detecting the increase in sound level or the popping sound at the fluid coupling while the fuel supply system is pressurized with the compressed gas at the target pressure indicates that the fluid coupling is liquid-tight with respect to a liquid fuel flowing through the fuel supply system from the liquid fuel source at a working pressure, the working pressure greater than the opening pressure of the check valve.