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Determine the Most Suitable Lifting Magnets Model

Posted on July 13, 2017

Armstrong Lifting Magnets NL-B series

Some customers have the misconception of magnetic lifting capacity and wrongly think that the rated lifting capacity would always be true for each load at different working conditions, such as its thickness, surface roughness, etc. There are a few factors that can de-rate lifting magnets maximum rated holding powers – see more detailed guild lines here.

If it’s the first time you use magnetic lifting devices, all these rules may be overwhelming and difficult to grasp. Here’s an example for you to better understand:

Loads need to be lifted: 6’x3’x½“ low Carbon steel plates with rough and dirty surface in 90oF

Calculation:

  1. Weight of plate = (6’)(12”/1’)x(3’)(12”/1’)x(0.5”)x(0.29 lb/in3)= 378 lbs
  2. The length is 6’ and the thickness of ½” is greater than ¼”. The plate should be stiff enough and not bend.
  3. Verify if NL-660B lifting magnet would work:
    Lifting capacity of NL-660B = 660 lbs x 60% [de-rated for 0.5” thickness] x 80% [de-rated for the rough surface condition] x 100% [low Carbon content] x 90% [elevated working temperature] = 285 lbs, which is less than 378 lbs.
    Even though it can lift the plate off ground, the 3:1 safety factor cannot be reached. Thus, NL-660B cannot safely lift this plate.
  4. Let’s take a look at NL-1320B:
    Lifting capacity of NL-1320B = 1320 lbs x 50% [de-rated for 0.5” thickness] x 80% [de-rated for the rough surface condition] x 100% [low Carbon content] x 90% [elevated working temperature] = 475 lbs, which is greater than 378 lbs.
    NL-1320B would be the smallest model to be used for hoisting this plate safely with 3:1 safety factor guaranteed.
If you have any questions regarding how to determine the lifting magnets model, feel free to contact us.