Paddle placement

Installation of propeller-type mixers varies greatly, depending on the specific application. Top-entering mixers utilize either a clamp- or flange-type mounting. It is important that the mixer be installed so the propeller or paddle placement is at a point within the tank, vessel, or piping that assures proper mixing. Vendor recommendations found in O M manuals should be followed to ensure proper operation of the mixer. 

Stirring Paddle Devices. In an attempt to overcome these problems as well as the temperature limitation (85 °C) of standard oil field equipment, other devices, similar to the equipment used to measure the thickening time, have been developed (20). The cement slurry contained in a cylindrical cup is usually stirred with a paddle under pressure and temperature. This allows the simulation of the shear history encountered by the fluid during placement. Then, the rotational speed is reduced to a very low value—typically 0.003 rpm—and the torque on the paddle is measured as a function of time. The main advantages of such a technique is that measurements are performed under realistic conditions of pressure, temperature, and shear history. On the other hand, the analysis of the data is not straightforward as the stress distribution in these devices is not known, and it is not clear whether or not measurements are affected by wall slip layers. 

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