Patent ID: 7493969

Claim:
A system for conveying material from a vessel, the system comprising a vessel for receiving material to be conveyed, a first conduit for conveying air, a second conduit for receiving air from the first conduit and for conveying air into the vessel, a metering screw for receiving material from the vessel and for moving the material from the vessel, a discharge line for receiving the material from the metering screw, the discharge line having an exit end, pressure sensor apparatus for sensing pressure in the discharge line, control apparatus for automatically controlling the metering screw in response to a pressure sensed by the pressure sensor apparatus, an outlet valve for selectively opening and closing the discharge line, a third conduit for receiving air from the first conduit and for conveying said air to the discharge line, the third conduit between the metering screw and the outlet valve, a fourth conduit for receiving air from the first conduit and for conveying air to the discharge line, the fourth conduit between the outlet valve and the exit end of the discharge line, a first valve for selectively controlling flow in the first conduit, a second valve for selectively controlling flow in the second conduit, a third valve for selectively controlling flow in the third conduit, the control apparatus including selection apparatus for selecting a first air flow or a second air flow to flow to the third conduit, flow apparatus for flowing the first air flow or the second air flow into the third conduit, the first air flow at a velocity different from a velocity of the second air flow, wherein the control apparatus includes a first line with a first orifice member, a second line with a second orifice member, the first line having flow opening area lass than an opening area of the second line so that air at a velocity greater than a velocity of air in the first line is flowable from the second line, and valve apparatus for controlling flow in the first line and the second line so that flow from either line may be selected, the flow opening area of the first line is sized for facilitating the flow of wet material through the discharge line, the flow opening area of the second line is sized for facilitating the flow of dry material through the discharge line, with the first and third valves open, air pressure equalized across the metering screw, and wherein the material is drilling cuttings material.