Laboratory Equipment

Stirring is an important process that takes place in a lab. It is used for the homogenization of liquids and the breakdown of solid particles in liquids. It’s also an efficient way to balance out the temperature and concentration of the liquid. Stirring liquids speeds up the chemical reaction and the dissolution process.

There are a variety of stirrers for lab use. They each have their own features that make them more efficient for certain applications. In this guide we’re going to cover overhead stirrers.

What is an Overhead Stirrer?

An overhead stirrer is a device found in labs and is used for homogenizing, mixing, suspending, and recirculating high viscosity substances or large volumes. Overhead stirrers are typically used when a magnetic stirrer can not be used. With overhead stirrers, you can monitor the progress of a reaction during viscosity change.

Parts of an Overhead Stirrer

Overhead stirrers consist of the stirrer itself, paddles, rods, and stands. The paddle is one of its most important features. The different types of paddles are used for different applications depending on the stirring motion, speed, turbulence, and flow they create.

The different types of paddles include the following:

Paddle

A paddle is used for low to medium speeds, minimal turbulence, and a tangential flow.

Anchor

An anchor is used for low speeds, high viscosity liquids, and a tangential flow.

Centrifugal

A centrifugal is used for medium to high speeds, round vessels with narrow necks, and an axial flow.

Propeller

A propeller is used for medium to high speeds, minimal shearing forces, and an axial flow.

Turbine

A turbine is used for medium to high speeds, a minimum shearing force, and an axial flow.

Dissolver

A dissolver is used for medium to high speeds, high shearing forces, high turbulence, particle reduction, and radial flow.

6 Criteria to Choose an Overhead Stirrer

There are 6 criteria that you should consider when choosing an overhead stirrer. These include the following:

1. Viscosity

Viscosity refers to the fluid's thickness when stirring. Higher viscosity requires greater torque from the motor of the stirrer when mixing. The stirrer must be able to maintain its speed during the changing conditions of the viscosity. Therefore, you want to make sure the overhead stirrer can handle the maximum viscosity of your batches.

To determine this, you must know the viscosity ranges that you will be stirring in. Will it be aqueous, low viscosity, average viscosity, or high viscosity?

   2. Stirring Speed

Stirring speeds vary by model. Most stirrers provide either a single speed or a range of speed. Consider what speeds are needed for the mixing you typically perform. An overhead stirrer with a digital display of speed is very helpful.

   3. Volume

Consider an overhead stirrer that will meet or exceed your typical maximum batch size. Volumes can range anywhere from 2L, 25L, or 200L.

  4. Torque

Torque refers to the rotational force to turn the rotor that is used to increase the pressure and flow of the fluid. The higher the torque, the more efficient the stirrer is able to maintain rotation in mixtures with high viscosity. Any increase in the diameter and speed will need extra power and impact your torque.

5. Interface

Do you need an interface to connect to a PC? There are overhead stirrers with programmable mixing and data logging that can be controlled by an external source such as a computer.

6. Overhead Stirrer Accessories and Options

Do you need any accessories, options, or extra features? There are reversible models for stirring in clockwise and counterclockwise directions. Other features to consider are automatic shutdown, programmable mixing, a stand, a light, timer, zero torque, speed display, and digital torque display.

Where to Buy Overhead Stirrers

Lab Pro offers a large variety of chemicals and laboratory supplies. For over 40 years, Lab Pro Inc. has been committed to delivering the highest quality overhead stirrers, microscopes, chemicals, tweezers, hard-wire cutters, lab supplies, and cleanroom PPE apparel to medical device and electronic manufacturing companies and laboratories worldwide. To learn more, visit the biggest Lab Supply showroom in California, or contact us online at 888-452-2776.