Abstract: A system and method for mixing cement slurries at an oil or gas well site and for pumping such slurries into the well provide automatic combined and interrelated density and pumping control and selectable sequential control of predetermined mixing and pumping stages. Specific conditions automatically controlled include water rate, water pressure, slurry density, recirculating slurry pressure and downhole pump rate. Each of these conditions is the subject of a respective control loop that operates independently, but under control from a central controller. The central controller generates interrelated inlet water, inlet dry cement and outlet downhole pumping control signals responsive to operated-entered desired operating characteristics.

Abstract: A double poppet area relief valve for use in a well treatment pumping system. The relief valve includes a housing comprising a cylinder and a body. A piston is disposed in the cylinder and has a push rod extending therefrom into the body. A double poppet assembly is attached to an end of the push rod. In one embodiment, the double poppet assembly includes a sealing poppet assembly for sealing with a poppet seat when in a closed position and an orificing poppet assembly for providing throttled fluid flow through the body when in an open position. In a second embodiment, a ring holder is attached to the push rod and has a sealing poppet ring and an orificing poppet ring disposed thereon. The sealing poppet ring and the orificing poppet ring function in a manner similar to the sealing poppet assembly and orificing poppet assembly, respectively, of the first embodiment. With both embodiments, wear is minimized on the sealing poppet so that the valve will reseal on the poppet seat when closed after usage.