Permanent lifting magnets or magnet lifters are a very useful piece of lifting equipment, they are designed to lift metals using only magnetic forces and are particularly useful within areas where steel is handled; they are frequently use in ship yards, scrap yards and steel workshops, and are great accompaniments to jib cranes and mobile gantries. The lifting magnet is best for lifting and handling steel sheets yet can also lift cylindrical steel. However the lifting capacity for cylindrical objects will be much reduced due to the fact that it will have a much smaller contact area with the magnet.
A lifting magnet or magnet lifter as they are sometimes referred to as is a piece of lifting equipment that is designed for lifting ferro-magnetic (metals with a high susceptibility to magnetization) materials such as iron, nickel, cobalt & alloy compounds. Steel is produced from a mix of several metals, producing an alloy; the main ones being iron, nickel and manganese, these substances and their compounds are ferro-magnetic. However some types of stainless steel are not magnetic because of their makeup. Metals with different make-ups have differing abilities to hold magnetism, so for materials other than mild steel such as; high carbon steels, cast iron and ferrous alloys a reduction in the lifting capacity must be applied, this varies between the materials, so always refer to the lifting magnet manual.
Key Features of lifting magnets
Lifting magnets are available in a variety of models with varying lifting capacities, all of which will have a minimum thickness of steel which they are able to lift safely; using a magnet to lift steel with less than the stated minimum will have a great impact on the safety of the lift. Different models are capable of lifting varying lengths of sheet steel, however more than one lifting magnet can be used on the same piece allowing for longer lengths to be lifted, this is a very common practice in steel plants, however if more than one magnet is to be used then you should use a spreader beam with a magnet at each end, these enable both magnets to be raised at the same time to keep the load stable.
How they work
Lifting magnets work manually, requiring no power supply and are easily operated by a single person. The magnet is usually attached to a crane of some type, or high beam through the use of a lifting hoist which allows the magnet to be raised and lowered as needed. The magnet is placed onto the steel sheet, centrally in line with the centre of gravity if just 1 magnet is being used, and the lever is then locked down, this applies the strong magnetic force required to lift the steel sheet.
Lifting magnets require little maintenance but keeping it very clean is imperative to ensure the magnetic forces are kept at the optimum level; You should regularly check for signs of wear and any defects that could affect the safe use of the magnet including the locking lever and top hook; you should have them tested and inspected by an authorised person at least every 6 months to ensure their continued safety.
Important Safety Factors
It is extremely important to be aware of factors that will have an impact on the lifting capacity and therefore safety of the lifting magnet. Air gaps are the most common problem; these are usually caused by badly machined steel surfaces, dust or dirt and paint; the surface should be as level and clean as possible to avoid these air gaps because the more air gaps present the lower the safe lifting capacity of the magnet and therefore could cause the magnet to drop the load. The magnet needs to have full and total contact with the steel to achieve maximum lifting capacity. Trial lifts should always be undertaken to assess the hold and stability of the load, this allows for re-positioning if necessary.
There are many important guidelines for the safe use of a lifting magnet, a couple of the key points will be 1; never use a magnet around medical equipment, people with pacemakers or insulin pumps as the magnetic force may cause failure of these devices. 2; never magnetise the magnet (by locking the lever down) without a load. 3; never de-magnetise the lifter (by raising the lever) until the load is completely lowered safely.