Abstract: A system for and a method of establishing and maintaining fluid at desired cleanliness, viscosity and temperature levels in a flow system. The system includes a driven pump that circulates fluid from a fluid source through a hydraulic loading system that includes an unloading valve. As fluid flows through the valve, a pressure drop is created across the valve operator, which restricts flow through the valve. This pressure drop across the valve operator results in the dissipation of heat, increasing the temperature of the fluid flowing through the valve. During operation of the system, if a low temperature condition is sensed in the system, power will be supplied to the pump, which pumps fluid through the valve at a controlled low pressure drop to result in a controlled heating of the fluid. When the fluid is restored to a desired temperature level, power to the pump is discontinued to terminate flow through the valve.

Abstract: A flow loading unloader valve wherein the operating force for moving the valve from the unloaded condition to the loaded condition is supplied by the flow through the valve itself. The valve, which may be interposed between a fluid supply and a high pressure load, comprises a valve body, having an inlet, a working outlet, a bypass outlet, and a valve operator, which may include a spool, that controls the direction of flow through the body. Movement of the valve operator to change the valve from the unloaded condition to the loaded condition is accomplished by applying the differential pressure created by the flow of fluid from the inlet to the bypass outlet to the piston ends. As the pressure increases as a result of increased flow resistance through the valve, the valve operator moves from an unloaded to a loaded position, terminating flow to the bypass port and resulting in high pressure flow to the working outlet.

Abstract: A system for and a method of establishing and maintaining fluid at desired viscosity and temperature levels in a flow system. The system includes a driven pump that circulates fluid from a fluid source through a hydraulic loading system that includes an unloading valve. As fluid flows through the valve, a pressure drop is created across the valve operator, which restricts flow through the valve. This pressure drop across the valve operator results in the dissipation of heat, increasing the temperature of the fluid flowing through the valve. During operation of the system, if a low temperature condition is sensed in the system, power will be supplied to the pump, which pumps fluid through the valve at a controlled low pressure drop to result in a controlled heating of the fluid. When the fluid is restored to a desired temperature level, power to the pump is discontinued to terminate flow through the valve.