Hydraulic lifts

A hydraulic lift makes more sense for a low travel height - up to 5-6 floors - and a high rated load. It needs no machine room at the top, and the load is transferred to the pit floor rather than the top of the shaft, which simplifies the building structure.

The maximum pipe length is set by the manufacturer for each model: as the length increases, efficiency drops and pressure losses rise, so the figure is taken from the technical data sheet, not from someone else's experience. The room must be heated, accessible for maintenance and fitted with a drip tray in case of an oil leak. Most often it is a storeroom, a utility room or a corner of the plant floor next to the shaft.

The car will descend to the lowest stop under its own weight - the oil flows back into the tank through a valve. If the power unit has a battery-powered emergency lowering device, the lift will do this by itself and open the doors within seconds. Without such a device a technician opens the valve, so for sites with an unreliable power supply this option is included in the order from the outset.

It depends on the layout. A direct-acting cylinder under the car needs a borehole for the full travel height - this means separate works involving ground investigation and waterproofing. The alternative is side-mounted cylinders with rope multiplication: they stand to one side in the shaft, the car travels twice as far as the ram, no borehole is needed and the pit is standard. The layout is chosen based on the travel height and ground conditions.

Far fewer than a traction lift: the limit is set by oil heating, and the manufacturer states it in the technical data sheet together with the permissible duty cycle. Exceed it and the thermal protection trips, and the lift stops to cool down. That is why hydraulics are not suitable for a residential building with heavy traffic, but in a warehouse with a few dozen pallet lifts per shift they run for years without complaint.

The ram seal wears over time, and a leak in the pit is a typical sign of a neglected lift. With proper maintenance the seals are replaced on schedule, a drip tray is placed under the cylinder and the tank level is checked according to the scheduled maintenance plan. The problem is not the drive itself but whether the site has any maintenance at all.