Abstract: Automated objective crosslink time and crosslink temperature determinations are provided in a method of testing for chemical crosslinking of a fluid. A fluid having a crosslinking agent is placed in a vessel and a paddle is rotated through the fluid in the vessel at substantially a constant rotational speed. A paddle torque parameter is sensed at sequential times and digital signals are encoded to define digital torque data representing values of the sensed torque parameter. In response to stored digital torque data and digital time data, a baseline torque parameter value and a change in the digital torque data representing increasing torque of the paddle are determined. In response to the baseline torque parameter value and the change in the digital torque data, a crosslink time for the fluid is determined. A crosslink temperature can also be determined. This is determined in response to the crosslink time and stored digital temperature data that has been obtained at sequential times.

Abstract: A method of unsticking a material delivery apparatus comprises automatically generating and applying to the material delivery apparatus a cyclical drive signal that causes at least two levels of torque to be applied to the material delivery apparatus.