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Hyundai MRL hoistway

Steel structure of a scenic M.R.L. traction elevator in Indonesia. As you can see, there is no fixed machine room above, side or bottom the hoistway.

Machine room less elevators (usually shortened to as M.R.L. or MRL) are a type of either traction or hydraulic elevator which do not require a machine room for the elevator.

Design

Traction elevators

Machine room less elevators do not have a fixed machine room on the top of the hoistway, instead the traction hoisting machine is installed either on the top side wall of the hoistway or on the bottom of the hoistway. The motor is installed using a permanent magnet which "sticks" the motor permanently and work with Variable Voltage Variable Frequency (VVVF) drive. Some of the hoisting machines are using gearless synchronous motors instead conventional induction motors. This design eliminates the need of a fixed machine room and thus saves much building's space. Almost all the traction MRL elevators are gearless traction.

While the hoisting motor is installed on the hoistway side wall, the main controller is installed on the top floor next to the landing doors. This controller is situated behind a locked cabinet which have to be unlocked using a key for maintenance, repair or emergency purposes. Most elevators have their controller installed on the top floor but fewer elevators have their controller installed on the bottom-most floor. Some elevators (like those in Japan) may have the hoisting motor located on the bottom of the elevator shaft put, thus it is called as "bottom drive MRL" elevator. Some elevators (like Otis and Schindler) have the controller cabinet installed within the door frame instead on the wall to save space.

Like normal traction elevators, machine room less elevators uses the conventional steel cord ropes used as the hoisting cables. Some elevator brands (such as Otis and Schindler) are using flat steel rope belts instead of conventional ropes. Manufacturers using these technology claimed that with flat steel belt ropes, it saves much space on the hoistway and to allow a minimum size of the hoisting sheave. With flat steel belts also allows 30% lighter than conventional steel ropes.

Most machine room less elevators are used for low to mid rise buildings. Machine room less elevators in mid-rise buildings usually serves up to 20 floors.

There is a very rare design in which the traction machine is positioned under the elevator cab. An example of this design was used on the SchindlerMobile elevators introduced by Schindler in the late 1990s.

Hydraulic elevators

Like the traction version, machine room less hydraulic elevators do not have a fixed room to house the hydraulic machinery. The machinery, which includes the pump, is installed on the elevator pit. The controller is located on a wall near the elevator and usually on the bottom floor. A benefit of machine room less hydraulic elevators is saves construction time, space, and cost.

Examples of machine room less hydraulic elevators are Otis HydroFit and thyssenkrupp Endura MRL. In California MRL Hydraulic elevators are not sold.

History

In possibly the 1950s, Pickerings invented the first machine room less elevator, the Pickerings Econolift. Possibly in the mid-1970s, the Pickerings Econolift was discontinued. In 1996, Kone launched the world's first MRL elevator system "Kone MonoSpace" along with its signature hoisting machine "EcoDisc". The EcoDisc machine is shaped like a big green round disk. Soon, many rival companies began to make their own MRL products due to the popularity of Kone's MonoSpace elevator.


Toshiba (under strategic alliance with Kone) marketed their first MRL products in 1998 called SPACEL (another product was called Order SPACEL) which is based on the Kone MonoSpace elevator system. In 1999, Mitsubishi launched their bottom drive MRL elevator called "GPQ", in which the hosting motor is located on the elevator pit.[1] Nowadays they make Elenessa, NEXIEZ-MRL and DiamondTrac (for United States only), which the hosting motor location is adjustable in the shaft.

Schindler started their MRL elevator system in 1997 by introducing SchindlerMobile, which is a direct drive elevator system where the motor is installed under the car. Later, Schindler introduce another MRL elevator in 1998 called SchindlerSmart MRL.

Otis launched their first MRL elevator product called Gen2 in 2000. Unlike other manufacturers, the Gen2 elevator uses flat steel rope belts instead of conventional steel ropes. In 2004, ThyssenKrupp introduced their first MRL elevators in the United States, named ISIS, which uses Kevlar belts. However, this product was discontinued after the Seattle children's hospital incident and was replaced by Synergy in 2008. In 2011, Otis launched their first hydraulic MRL system called HydroFit which is only sold in the U.S.

Benefits and detriments of MRL elevators

Benefits

  • Saves building space, as it doesn't require space for a machine room.
  • Saves building electricity for up to 70%.
  • Uses no oil (thus eliminating the risk of fire).
  • Slightly lower cost than other types of elevators (because the Variable Voltage Variable Frequency (VVVF) drive).[2]

Detriments

  • No code has been approved for the installation of MRLs as residential elevators.
  • Loud, high frequency sound when the elevator is running (because of the Variable Voltage Variable Frequency (VVVF) drive).[2]
  • Life expectancy of MRL elevators is lower compared to other types of elevators.
  • Equipment may be comparitively harder to maintain.
  • Motor can be damaged in bottom drive MRLs in the event of pit flooding.

Notable MRL models

Main article: List of machine room less elevator models

Incidents

In 2006, one of the ThyssenKrupp ISIS elevators in Seattle's children hospital had its Kevlar ropes snap due to overheating. The elevator car fell from the 7th floor to the 3rd floor and came to a complete stop after the emergency brake engaged. No one was injured. The elevators were taken out of service a few days later for an inspection by the police.

Trivia

  • The U.S. was slow to accept MRL elevators because of elevator codes.
  • In the United States, most MRL elevators have their controller located at a small fixed room which houses the controller (rather than installed next to either the top or bottom floor landing doors).
  • In California, MRL elevators are only allowed to travel a maximum of 290 ft. (instead of 300 ft. elsewhere). This regulation is probably due to California's elevator safety codes.
  • After the machine room less elevator products was launched, a mini machine room elevator (or sometimes called "compact machine room elevator") products has been launched and just simply to put the machine room less elevator hoisting motor and equipments into a small machine room[3] (like EcoDisc).
  • It is possible for a destination dispatch system to be implemented on MRL elevators, normally for low to mid-rise installations.
  • One of the highest machine room less elevators are in Ming Wah Dai Ha Block G and the lift tower in Choi Hei Road Park, which both shaft can serve 15 floors (the lift tower in Choi Hei Road Park serve only 3 floors but the height of the shaft make them can serve like 15 story of the Public Housing Estate Blocks just beside the lift tower). Both are Kone MonoSpace installed in Hong Kong, China.

Gallery

MRL controller cabinets

Signs

Hoisting Motors

References

  1. GPQ series MRL elevator overview
  2. 2.0 2.1 hkelev - Elevator work with Variable Voltage Variable Frequency (VVVF) drive
  3. hkelev - Machine Room Less Elevator
Elevator 

Drive systems: Traction • Winding Drum • Hydraulic


Types of elevators: Double DeckDumbwaiterFireman'sFreightIncline • PassengerResidentialWheelchair lift


Concept: Destination dispatchElevator algorithm • Elevator control systemElevator machine room • Elevator maintenanceElevator major alterationsElevator modernizationMachine room less elevator


Elevator systems, controllers and equipments: 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) • Regenerative converter (for AC-VVVF-powered elevators)


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

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