Process control system using remote computer and local site control computers for mixing a proppant with a fluid

Claim 1

A process control system for controlling the concentration of a proppant slurry to be pumped down a well bore for stimulating production thereof, said system comprising: a remote control computer spaced from a location where the process is performed, said remote control computer including means for entering control information, and for computing at least one set point therefrom; a monitor computer disposed at the location where the process is performed, said monitor computer including: means for providing real time information about monitored operating characteristics of the process; and means for transmitting said real time information; a local control computer disposed at the location where the process is performed, said local control computer including: means for receiving said real time information from said monitor computer; means for receiving feedback information from a controlled characteristic of the process; and means for providing, in response to the real time information, to the set point and to the feedback information, a control signal to control the controlled characteristic of the process; and cable means for connecting said remote control computer to both said monitor computer and said local control computer, said cable means including two, and only two, communication channels defined between said remote control computer and said monitor computer and said local control computer so that each of said monitor computer and said local control computer communicates with said remote control computer through the same two channels.