Suction cup lifter guide

How a cup holds

The UK safety regulator's guidance on vacuum lifting describes the principle plainly: push an inverted rubber cup onto a suitable surface, pump the air out from under it, and the atmospheric pressure on the outside holds the cup in place against a considerable vertical load. Pumping is the only thing that differs between the Bluebow lifters. The 8 inch manual cups are pumped by the valve on top and show the vacuum on a gauge; the 10 inch electric cup pumps itself with a motor, shows the pressure on a screen and refills the vacuum when it drops.

What the pound rating means

The manual pair is rated 440 lb per cup and 880 lb together; the electric cup is rated 662 lb, with a refill that cuts in below 573. These are figures on a clean, smooth, non-porous surface with the pad in good condition. The same guidance says the load at which a lifting attachment will not fail should be at least twice its safe working load, which is a way of saying the rating is not a target. Weigh the sheet, keep well under the rating, and use two cups on anything wide enough to flex.

Ratings are the ones each lifter states for itself.

Surfaces that hold and surfaces that leak

Glass, mirror, glazed tile, polished granite and marble, stainless steel and painted sheet metal seal. Honed or textured stone, concrete, raw wood and anything dusty or wet do not: air finds its way under the pad through the pores and the grit. The guidance we read says porous materials impair the lifting capacity and that loose material has caused loads to drop. The electric cup's own instructions add curved, holed and unfinished boards to the list of what not to lift.

Checks before the lift

Inspect the pad for nicks and embedded grit at the start of every day, as the guidance asks. Wipe the surface where the pad will sit. Pump down and watch the gauge or the screen for a few seconds before you take the weight; a reading that drifts is a leak. Lift with your legs, keep the sheet close, and set it down on blocks so the cups release with the sheet supported, not in your arms.

The ratings and the surface rules on this page are the ones the Bluebow lineup prints on both lifters; both are on the suction cups shelf.