Elevator Wiki
Hydraulic 01

Conventional roped hydraulic diagram (but missing the govenor)

Hydraulic elevators are elevators which are powered by a piston that travels inside a cylinder. An electric motor pumps hydraulic oil into the cylinder to move the piston. The piston smoothly lifts the elevator cab. Electrical valves control the release of the oil for a gentle descent.

Hydraulic elevators are used extensively in buildings up to five or six stories high. Sometimes, but rarely, up to 8 stories high. These elevators, which can operate at speeds up to 61 meters (200 ft) per minute, do not use the large overhead hoisting machinery the way geared and gearless traction systems do.

All modern hydraulic pumps are either equipped with a Solid-State Contactor or a mechanical Y-Delta starter. Solid-State Contactor statrers are better for the motor and the building's power supply, as the windings last longer and there are no voltage drops across the line of the building's power supply. Y-Delta starters use two contactors to start the motor on a reduced speed, then kick on full speed. Old hydraulic elevators just started up abruptly, sending mains power at full blast right into the motor. This puts a lot of strain on the motor which, in turn, makes it burn out faster than motors on Y-Delta or Solid-State Contactor starters.

There are three types of hydraulic elevator; holed hydraulic, holeless hydraulic and roped hydraulic.

Holed hydraulic

With holed hydraulic systems (also known as direct acting lift[1]), the elevator car is mounted on a piston that travels inside a cylinder. The cylinder extends into the ground to a depth equal to the height the elevator will rise. As hydraulic fluid is pumped into the cylinder through a valve, the car rises. As the fluid returns to the reservoir, the car descends. This system is often called Inground hydraulic.

Holeless hydraulic

Holeless hydraulic elevators (also known as direct side acting lift) were invented in the late 1970's or a little earlier. Holeless hydraulic elevators of pistons mounted inside the hoistway to raise and lower the car. This is especially a solution for buildings built in bedrock, a high water table or unstable soil conditions locations that can make digging the hole required for a conventional hydraulic elevator impractical. Holeless hydraulic systems use a direct-acting piston to raise the car.

Roped hydraulic

Roped hydraulic elevator (also known as indirect acting lift[1]) extends the rise of the holeless elevator to 18 meters (60 ft), without the need for a belowground cylinder. As the higher power of the hydraulic cylinder and the power unit, The 1:2 ratio (power from the hydraulic power unit: elevator actual moving distance)[2][3] can be provided. Roped hydraulic elevator systems have the piston attached to a sheave which has a rope passing through it. One end is attached to the car while the other is secured at the bottom of the hoistway. Also, roped hydraulic systems require a governor because the rope is holding the car up, and there is a risk of the car freefalling when the rope breaks.

Machine room less hydraulic

Further information: Machine room less elevator

This hydraulic elevator does not require a fixed room to house the hydraulic machinery, instead, the machinery itself is usually installed on the elevator pit and the controller is installed behind a locked cabinet on the wall near the elevator. The benefit of machine room less hydraulic elevator is that it saves construction time and cost. Examples of machine room less hydraulic elevator is Otis HydroFit and thyssenkrupp Endura MRL.

Benefits of Hydraulic Elevators

  • No need for reinforcement. The cylinder that lifts the elevator cab is supported by the ground underneath (for holed hydraulic only).
  • Are usually cheaper than traction units.
  • If the line breaks, the elevator will fall no faster than oil can escape.

Detriments of Hydraulic Elevators

Older hydraulic elevators may have a risk of leaking hydraulic oil into an aquifer and causing potential environmental contamination. This has led to the introduction of PVC liners (casings) around hydraulic cylinders which can be monitored for integrity. Additionally, older hydraulic elevator systems usually have a motor outside of the tank and cause noise when the motor is running (this layout is no longer used in the hydraulic elevators installed in mid-1990's or later, when the submersible hydraulic power unit was introduced. The motor is placed inside the tank and the motor sound is isolated by the oil in the tank).

In 2007, Kone announced that the company would stop manufacturing and producing hydraulic elevators due to environmental concern, therefore replacing them with the eco-friendly machine room less MonoSpace and EcoSpace elevators. This makes Kone the first elevator company to only produce traction elevators. Also, some other elevator manufacturers have stopped producing hydraulic elevators due to the same reason.

Notable hydraulic elevator models

Notable hydraulic component suppliers

  • Bucher Hydraulics (also known as Beringer Hydraulik GmbH)
  • ALGI Alfred Giehl GmbH & Co. KG.


==Notes and references==

External links

Drive systems: Traction • Winding Drum • Hydraulic

Types of elevators: Double DeckDumbwaiterFireman'sFreightIncline • PassengerResidentialWheelchair lift

Concept: CapacityDestination dispatchElevator algorithm • Elevator control systemElevator machine room • Elevator maintenance • Elevator monitoring systemElevator modernizationACOP & UCMPMachine room less elevatorMajor alterationsRated speed

Elevator systems, controllers and equipments: Elevator emergency automatic rescue device • Elevator fixtures • Elevator keys • Elevator special modesElevator doorsDoor camDoor interlocks (Interlock wiring communication system) • Door restrictorElevator Inspection CertificateEmergency stop buttonFloor designatorsGate switch • Old Deadman controls • Overspeed governorMotor-generator set & Silicon-controlled rectifier (for DC-powered elevators) • Insulated-gate bipolar transistor (for AC-VVVF-powered elevators) • SelectorTape headRegenerative converter (for AC-VVVF-powered elevators)

See also: List of elevator fixtures guide • List of elevator and escalator companies • Elevator door sill guide (Non-proprietary elevator component door sill guide) • Floor numbering (Unlucky floor numbers) • Elevator incidents and accidents

Elevator drive systems
TractionM.R.L.Winding DrumHydraulic (Oildraulic)
Reference: hkelev - Elevator drive systems

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