Patent ID: 8162619
Filing Date: 2012-04-24
Classification: F02D,F04B,Y10T

Abstract:
1. A method for controlling the discharge pressure of an engine-driven centrifugal pump in a system including the engine having an idle speed Si, the pump being driven by the engine, an intake line coupled to the pump for receiving a liquid, a discharge line coupled to the pump for discharging the liquid, a pencil strainer mounted on the discharge line, a pilot control line connected to the discharge line at the pencil strainer, the pencil strainer directing liquid from the discharge line into the pilot control line, an internal pressure sensor in the pilot control line sensing an actual internal pressure Pa in the discharge line, a conduit downstream of the internal pressure sensor, a relief valve in the discharge line and coupled to the conduit, the relief valve being actuatable in a first direction away from a fully closed initial condition, the internal pressure sensor being located upstream of the relief valve, and a controller operatively connected to the engine, the internal pressure sensor and the relief valve, for varying a speed of the engine, and a condition of the relief valve, the method comprising the steps of: a) selecting a desired internal pressure Pd for the discharge line; b) operating the engine to drive the pump and generate pressure in the discharge line, c) increasing engine speed if Pa<Pd while maintaining the relief valve in the fully closed initial condition; d) decreasing engine speed if Pa>Pd and the engine speed is greater than Si, while maintaining the relief valve in the fully closed condition; e) opening the relief valve if Pa>Pd and the engine speed is equal to or less than Si without adjusting the engine speed; and f) closing the relief valve if Pa<Pd and the engine speed is less than or equal to Si; and g) repeating steps c) through f).