Overhead Stirrer Selection Guide
Our selection guide will help you answer some common
questions so you can choose the appropriate overhead stirrer
for your needs.
Key Factors to Select An Overhead Stirrer
In contrast to magnetic stirrers, overhead stirrers are more robust and are mostly used for stirring larger quantities and liquids with higher viscosity. They consist not only of stirrers and stands, but also of rods and paddles. If you are looking for an overhead stirrer and don't know which one to choose from the overwhelming selection, this guide will help you find the best stirrer for your lab and applications. Here are some factors to consider before you buy.
1. Viscosity
It is important to know the viscosity (the "thickness") of the liquids to be processed, especially if you intend to mix batches with a higher viscosity than water or a viscosity that increases as the stirring progresses, such as lotions or polymerisations. Mixing liquids with higher viscosity requires a higher torque from the stirrer motor. To avoid overheating and reduction in the lifespan of the device, choose a stirrer that can handle the maximum viscosity of your solution and maintain its speed under changing viscosity conditions.
2. Maximum Volume
Overhead stirrers are designed for stirring larger quantities. The maximum capacity of overhead stirrers available on the market is between 2L and 200L. The capacity of the stirrer should not exceed the maximum batch size. The maximum volumes are usually based on the viscosity of the liquid, unless specified by the manufacturer.
3. Stirring Speed
Most overhead stirrers offer a wide speed range, such as 30-2000rpm or 40-6000rpm, but there are also some models with single speed options. The speed range is related to the viscosity and quantity of the sample. For light stirring tasks in small quantities up to 10L, a speed of up to 2000rpm is sufficient. Stirrers for highly viscous applications in larger quantities up to 100L have a lower speed range, such as 0-300rpm or 0-530rpm. High-speed laboratory stirrers are designed for intensive stirring tasks in quantities up to 20L. Check which speeds are required for your process and stirring task.
4. Torque
Torque is the rotational force used to turn the impeller. The higher the torque the better the stirrer can sustain impeller rotation in higher viscosity mixtures and when using larger diameter impellers. A small increase in impeller diameter and speed will result in a great increase in the power required for mixing, as shown in a simplified version of the power equation: Power = rpm3 x Diameter5. High-torque stirrers with forces >300N•cm are powerful models for high viscosity applications and intensive mixing of quantities up to 150L.
5. Other Features
Other features that may be important to your application and lab include stirrer chucks, digital or mechanical controls, timers, torque and speed displays.
Use our interactive selection tool to find the best fit overhead stirrer with ease.
Check our impeller selection guide to choose the right impeller for your overhead stirrer.