27.11 SAFE USE OF VACUUM LIFTERS
In addition to any specific instructions relating to safe use issued by the manufacturer, the following points should be observed:
Do not use to lift people.
Do not lift loads over people who are in the danger zone unless the vacuum lifter has the features needed to address this situation. These features can include a redundancy of critical components and controls or a secondary mechanical means of securing the load. When establishing the danger zone, take account of the nature of the load. For example, sheet material can fly a considerable distance to the side. If necessary establish a ‘no go’ area.
Only use the vacuum lifter for applications for which it has been specified or is otherwise suitable.
Ensure that the surface of the load to which the vacuum lifter is to be attached is clean and dry. Light oil or other liquid coverings may be acceptable and may indeed make the vacuum lifter more efficient but see section 27.6 INFORMATION WHICH SHOULD BE EXCHANGED BETWEEN THE USER AND THE DESIGNER OR SUPPLIER (12).
Do not actuate the lifter before setting it on the load.
Do not attempt to hoist the load until you are satisfied that the vacuum lifter is capable of doing so. Methods of ensuring this will vary from one manufacturer to another and it is essential that the manufacturer’s instructions relevant to the particular type of vacuum lifter are consulted.
Ensure the load is balanced. An unbalanced load will tilt and may become detached by slipping.
Figure 27.11-1 Balanced and unbalanced loads
Be aware that flexible loads can peel off the vacuum pad. Do not attempt to lift a load if this is likely to happen.
Figure 27.11-2 Beware of load peeling
To overcome this problem, use a vacuum lifter with two or more vacuum pads in conjunction with a suitable lifting beam or spreader, ensuring that the share of the load taken by each vacuum pad does not exceed its capacity.
Figure 27.11-3 Use of multi-headed vacuum lifter to avoid load peeling
Vacuum lifters can be used to remove one plate or sheet of material from a stack. If used in this way, care should be taken to ensure that the top plate or sheet is free to move, i.e. not attached to the stack by strap banding, etc. Also be aware that smooth finished plates and sheets can adhere to each other particularly if a liquid is present, e.g. oiled steel sheet or wet glass.
Figure 27.11-4 Vacuum lifter used to remove one plate or sheet from a stack
Porous objects will have a lower density than solid objects made from the same material and will thus be lighter in weight. Their porosity will however allow the vacuum within the lifting pad to be dissipated through the load. This does not necessarily mean that the use of a vacuum lifter is out of the question. It does however mean that the vacuum dissipation must be taken into account.
Ideally, the surface of the load to be lifted should be flat such that intimate contact with the lifting pads of the vacuum lifter is made. Air gaps may however be present due to irregular shapes and in this situation the advice of the manufacturer should be sought. Surface texture and the presence of a non-adherent coating on the material may have an adverse effect on the vacuum lifter’s capacity. Air gaps may be tolerable within the limits laid down by the manufacturer.
It is possible to lift loads with other than flat surfaces using vacuum lifters. Round sections for instance can be handled provided that the vacuum lifter has suitably profiled lifting pads.
Figure 27.11-5 Lifting a round section with suitably profiled lifting pad
Always use the entire lifting pad surface. Air leaks will catastrophically affect the safe use of a vacuum lifter
Ensure that, once hoisted, the load is transported gently to avoid swaying and is not subjected to shock loads.
Do not attempt to release the vacuum lifter until the load has been set down in its final resting place.
Remember to include the self weight of the vacuum lifter when calculating the total load on the lifting machine.