The Material's thickness, surface finish and any air gap caused by dirt, paint finish, oil, water, slag etc. are very critical factors when selecting the correct lift magnet.

The formula for calculating the lifting strength is:

T x F x M x G x Capacity

T = Thickness
F = Surface Finish
M = Material
G = Air Gap
C = Capacity

For example:

The material you want to lift is a 300kg high carbon steel with a thickness of 40mm and rough machined surface. Lets say you have decided that a QZQ300 magnet is the right model for your application. For flat steel( air gap=0mm), the rated lifting strength is 300kgs.

Apply Formula For Model QZQ300 Application

T = 40mm, G = 0mm (According to the safety capability curve of model QZQ300, you can find T=100% and G=100%), F = F2, M = M3, C = 300

Using the above table and formula, we can determine the lifting strength of the chosen model to lift your material:

100% x 100% x 75% x 100% x 300 = 225kg

With a lifting strength of 225 kgs, for this application, the formula indicates the model chosen is wrong and will not safely lift the high carbon steel weighing 300 kgs.

The correct lifting magnet for this lift application is the Model QZQ600
100% x 100% x 75% x 100% x 600 =450kgs �� 300kgs

Note: This formula also applies to cylindrical materials, such as round steel, pipe, tube, bar etc. But your result needs to be reduced in value by 30%-50%.

Any help you need when selecting a correct lifting magnet for your applications, please don't hesitate to call us or send us an email, our experienced technical staffs will provide you with our professional and prompt services. Thank you.