An Overhead Stirrer is a laboratory device used for mixing, homogenizing, suspending, and recirculating large volumes or high-viscosity substances, which typically can't be handled by a magnetic stirrer. The device is considered the next generation of laboratory stirrers for stirring/ mixing pharmaceutical, food and cosmetic products. The equipment consists of a body, chuck, stainless steel blade propeller and a U-type stand. It is easy to use, general-purpose overhead stirrer, suitable for day-to-day laboratory use with aqueous and low viscosity liquids such as light oils, up to 5 litres with good speed control and overload protection.
The principal consideration in acquiring an overhead stirrer is a typical sample size and viscosity. But sizing an overhead stirrer for a specific application is part of art and science. The machines have power ratings that are somehow related to the volumes they can handle or to what volume of an aqueous solution they can stir. You can buy a 50-watt motor that says it can mix two litres, but if your material is viscous it may only handle 500 mL.
Overhead stirrers are specified often when either reaction or mixing volumes are very large, typically above two litres, but even more frequently when the operation is initially viscous or expected to develop significant viscosity. The choice comes down to volume and viscosity, as well as the materials you are stirring. In this situation, an overhead stirrer is the better alternative. These quiet, economical overhead stirrers are suitable for simple laboratory mixing, in applications such as processing media with substantial temporary viscosity changes. Speed controls are infinitely adjustable, and safety circuits ensure automatic cut-off in anti-stall or overload conditions.
Stirrer controls should be clear and intuitive to operate, especially with multiple users. Is the stirrer designed for continuous use? Is the stirrer maintenance-free, or does it require scheduling for service? Some facilities require verification of the speed and torque readings by calibration. Stirrers with overload or overheat protection automatically shut down to protect the electronics if mixing conditions are outside of an operational range.
Numerous features may be important to your facility and application. Stirrer chucks offer a range of diameters so ensure your impeller shafts will fit into the chuck. Stirrers with through shafts make adjusting the impeller to an optimal height in the vessel easy and even provide an easy way to move the impeller up out of the way for quick changes to mixing vessels.
The Stirring speed is controlled by a microprocessor that can compensate for any sudden speed change caused by overload changes or voltage fluctuations. Steeples regulation of the speed enables the user to modify the speed accordingly.