Method and apparatus for automatic pump shutoff

A method of detecting a fluid leak in a hydraulic circuit having a hydraulic machine and a variable displacement pump (VDP) with an adjustable swash plate, the method comprising:

• determining a requested outlet flow rate required for energizing the hydraulic machine;
• measuring a position of the adjustable swash plate;
• determining an actual outlet flow rate from the VDP using the measured position of the adjustable swash plate;
• comparing said actual outlet flow rate to said requested outlet flow rate;
• and
• selectively blocking an outlet port of the VDP when said actual outlet flow rate is positive while said requested outlet flow rate is zero.

A hydraulic fluid circuit comprising:

• a hydraulic machine operable for generating a requested flow rate;
• a pump having an outlet port, said pump being operable for providing an outlet flow of fluid to said hydraulic machine for energizing said hydraulic machine;
• a valve positioned at an outlet port of said pump;
• and
• a controller configured for determining an actual outlet flow rate of said fluid from said pump;
• wherein said controller is operable for determining said requested flow rate, and for selectively actuating said valve to thereby prevent said fluid from entering the hydraulic fluid circuit whenever said actual outlet flow rate is positive while said requested flow rate is zero.