On-line rheological measurement for process control

Apparatus for conducting on-line rheological measurements in a process flowing material carried in a process main stream so as to provide process control information based upon the viscosity of the process flowing material, utilizing a rheometer in which diverted material from a first conduit communicating with the process main stream is delivered downstream to an entrance of a capillary passage having a predetermined volumetric flow capacity, and passes from an exit of the capillary passage to a second conduit, while measuring means measures the viscosity of the diverted material in the capillary passage, the apparatus comprising:

• an inlet site located in close proximity to the entrance of the capillary passage;
• an inlet pump having an entrance communicating with the first conduit, and an exit communicating with the inlet site for delivering a volumetric flow of diverted material to the inlet site;
• a metering pump having an entrance communicating with the exit of the capillary passage, and an exit communicating with the second conduit for drawing a portion of the volumetric flow of diverted material from the inlet site through the capillary passage;
• a parallel flow passage having an inlet located at the inlet site, between the exit of the inlet pump and the entrance of the capillary passage, in close proximity to the entrance of the capillary passage, and an outlet communicating with the second conduit at a location downstream of the exit of the metering pump;
• and
• a parallel passage pump for moving a balance of the volumetric flow of the diverted material from the inlet site through the parallel flow passage to the second conduit so as to assure that a continuous supply of fresh diverted material is available at the inlet site, in close proximity to the entrance of the capillary passage.