Sizing a vacuum lifter – suction force, safety and the limits of the technique

Enough for the permissible holding force to exceed the load with reserve – and laid out so the part does not sag. With large, thin parts the layout usually decides rather than the force: four cups at the corners carry enough but let the panel sag in the middle.

Yes, if suction capacity is designed for it. Porous material draws air continuously; what matters is not the vacuum achievable but the volume flow the generator keeps supplying. For such cases we use pumps rather than ejectors and calculate with reserve.

Nothing – if the device is properly built. Check valve and reserve volume hold the load for a defined time, and the vacuum monitor warns visually and audibly. That is mandatory for vacuum lifting devices and is checked at every recurring inspection.

On porous, damp or oily surfaces, on strongly curved or perforated parts, and always where the load is to be tipped or turned and a failure could not be managed. Vacuum is the fastest pick-up but not the most universal.

Very safe, provided they are correctly sized and equipped. The holding force must exceed the load by a safety factor – 2 for vertical lifting, 4 for tilting – and the device needs a non-return valve, a reserve volume and a vacuum monitor that warns before the force is no longer sufficient. The most common causes of a dropped load are not device faults but unsuitable surfaces and worn sealing lips; both belong in the inspection.

As heavy as the rated capacity of the vacuum lifter and of the hoist it hangs from allow – there is no general upper limit. Hand-guided tube lifters for sacks and cartons typically carry a few tens up to a few hundred kilograms, plate lifters on a crane considerably more. What decides is the calculation: suction area times vacuum, divided by the safety factor, against the weight.

For smooth, airtight parts they are the fastest way to pick up a load: place, evacuate, lift – no slinging, no clamping and no access from below. With porous, oily or strongly curved parts this reverses, because the generator has to keep supplying or the grip becomes uncertain; a mechanical gripper is often the better choice there. An ejector also consumes compressed air continuously, which matters with long holding times.

Weight and dimensions of the load, its surface – airtight, porous, oily, textured –, the movement – lifting only, or tilting and rotating as well –, the cycle rate and the working area. These determine the number, size and layout of the cups, the choice between ejector and pump, and the carrier the lifter is guided on.

Yes, sheets and plates are a classic application. Points to watch are oil films that reduce friction under the cup – there are cups with a friction texture for this –, perforated or embossed sheets that offer no airtight contact, and thin large panels that sag. For ferromagnetic parts a magnetic gripper can be the simpler alternative.

Anything with a sufficiently airtight and flat surface: glass, sheet metal, plastic panels, coated wood-based panels, stone and tiles, packed goods such as cartons and sacks. Porous materials such as raw chipboard or concrete work as well but need a generator with a large flow rate. Unsuitable are open grids, parts with openings at the suction point and strongly textured surfaces without adapted cups.

Indefinitely while the generator runs – it continuously compensates for leakage. If the power fails, the non-return valve and the reserve volume hold the load for a defined time that is sufficient to set it down in a controlled way; the vacuum monitor gives a visual and audible warning. How long exactly depends on reserve volume, tightness and surface and is stated by the manufacturer. A load is therefore never left hanging unattended.

Yes – the cup itself only needs room on the surface, not beside or beneath it. The limiting factor is usually the carrier: a tube lifter on an articulated arm or a compact jib crane needs little headroom and floor space. Where the load is guided between racks or into a machine, we design the working area together with the device.