Читать книгу Elevator Troubleshooting & Repair - David Herres - Страница 9
ОглавлениеVirtually all modern elevators fall into one of three categories, with some exceptions, variations, and models that combine elements of two or even all three types. These types are traction elevators, hydraulic elevators, and machine room-less elevators.
Traction elevators are the most common type. They are characterized by multi-strand steel “ropes” that in a typical design are attached to a hitch plate at the top of the car. There may be six or more of these cables, each capable of lifting the car and occupants. The cables pass over and are driven by a deeply slotted sheave, two or more feet in diameter, at the top of the shaft, with the other ends attached to a counterweight. (In one design, two cars move synchronously in opposite directions, each functioning as the other’s counterweight.)
Instead of traditional ropes, some manufacturers, notably Otis, Schindler, and Kone, have introduced very light steel belts, with carbon fiber cores and high-grip coating. Lubricant is not necessary, and energy consumption is reduced, especially in high-rise applications.
Traction elevators, shown in Figure 2-1, may be geared or gearless. In the geared design, a higher-speed electric motor is coupled to the hoisting sheave by means of a worm-and-gear speed reduction unit, which turns the hoisting sheave. This arrangement has the advantage of requiring a smaller motor. The car travels at speeds of 125 to 500 feet per minute, with lifting capacity of up to 30,000 pounds. An electric brake stops the car as required and holds it at floor level.
The gearless traction elevator design permits car speeds in excess of 500 feet per minute. The counterweight, sized to equal the weight of the car plus half the weight of a car full of passengers, reduces the load on the motor. Car speed is a function of motor RPM and sheave size, typically two to four feet in diameter. To achieve proper car speed, this huge sheave turns at 50 to 200 RPM.
FIGURE 2-1 Traction elevator motor and drive. (Judith Howcroft)
In addition to the multiple lifting cables shown in Figure 2-2, safety is provided by car brakes that are engaged if the car were to begin falling at greater than a specified speed or if for any reason tension is lost on the hoisting ropes. A clamp closes on the steel governor cable and this causes brakes to engage the guide rails, stopping the car not too abruptly, but quickly enough so that it does not gain excessive momentum.
If the maximum vertical travel is greater than 100 feet, a system known as compensation is used. This consists of an additional set of cables or a steel chain, one end of which is attached to the bottom of the car and the other end is attached to the bottom of the counterweight. As the car rises, more of this chain or cable is lifted to balance the shorter amount of hoist rope between the car and sheave, and as it descends and the counterweight rises, this weight is added to the counterweight. This equalizes the amount of work required of the motor.
When compensation cables are used, an additional sheave at the bottom of the shaft keeps them in place. If they take the form of chains, they are guided by a horizontal bar.
FIGURE 2-2 In a traction elevator, steel ropes engage deep grooves in the sheaves. (Renown Electric)
In traction elevators there are several possible roping configurations. Suspension ropes attach to a hitch plate above the car, or they are underslung below, loop over the sheave, and pass down to the counterweight. Depending on the size of the car, there may be as many as eight, sometimes more, of these hoisting ropes, typically ⅝ inch diameter.
Low-speed elevators with geared motors generally have a single-wrap arrangement, where the rope passes over the sheave once and connects to the counterweight. Double-wrap is used with higher speed elevators having gearless motors.
1:1 roping consists of rope that is connected to the counterweight and travels as far as the car travels, in the opposite direction. It is used with geared traction systems and high-speed elevators. 2:1 roping consists of a sheave attached to the top of the counterweight. The rope moves twice as far as the car. This configuration is used on machine room-less, bottom-drive traction, gearless traction, and freight elevators. When higher capacity is required, 4:1 roping is used. The rope moves four times as far as the car.
In all cases guide rails are necessary. Otherwise the car, suspended at the end of the cable, would swing from side to side, hitting the walls of the shaft. In a new installation or making changes, wiring (in conduit), junction boxes and the like can be mounted on the shaft walls. It is important that they do not protrude beyond the guide rails, so they are not in the path of the car. There may be very little clearance in this area.
In today’s world, saving energy is a focus in building services. In an elevator installation, a regenerative drive accomplishes this by using the electric motor as a generator to return electrical energy to the facility and/or utility when a full elevator, which is heavier than the counterweight, descends or when an empty elevator ascends.
A traction elevator consists of steel ropes that raise and lower the car at a measured rate. The steel ropes lie in grooves milled into the sheave. These grooves serve two purposes—they keep the ropes separate and in place so that they don’t bunch up and tangle, and they provide much greater traction than if the ropes were to wrap about an ungrooved cylinder, in which case there would be only a single line of contact.
Naturally, with all the fast starts and stops, heavy loading, and continuous use, the steel ropes have to be replaced and the sheaves need to be regrooved periodically. How often depends upon various factors. In a group installation, you may be able to take one car at a time out of service in order to have the regrooving done and/or ropes changed. If the building has only a single car, you’ll need to do some careful planning and scheduling. For maximum rope and sheave life, it is important that all ropes have equal tension. Ropes should be checked frequently for signs of wear. All ropes should protrude an equal amount from their respective grooves. Worn sheaves cause premature wear on ropes, which then accelerates sheave wear, creating a mutual destruction scenario. Frequent inspection and maintenance as required are essential. An advantage of the traction elevator is its very safe and efficient braking system. The brake, as in automobiles, may consist of a large drum with brake shoes or a smaller disc with pads. The brake assembly is located close to the motor and/or gearbox. It is electrically actuated. Power is required to keep the brake disengaged, and when power is interrupted, the brake is applied. Thus, in a power outage, the brake is applied so the car cannot move.
Power is applied and interrupted simultaneously at the motor and at the brake. Power is interrupted in an outage when the motion controller senses a serious fault or shuts down for some other reason, when a human shuts off the disconnect, or when the car is intended to stop at a landing. If the motor were to stop without the brake being applied, the net weight of the car and counterweight would probably, depending on the gearing and loading, cause the motor to spin, allowing the car to move. Conversely, if power were to be interrupted at the brake but not the motor, the brake would rapidly heat with all that would entail.
In limited applications, the simplicity and user-friendly nature of hydraulic elevators makes them the preferred choice.
The most common installation, shown in Figure 2-3, involves a large hydraulic piston that extends underground beneath the building to a depth equal to the amount of car travel, measured at the bottom of the car floor. In practice, this type of installation is limited to not much over four floors, so it is never seen in high-rise buildings. That being said, they are often preferred in low-rise buildings where there is no bedrock. There are boring techniques that permit a hydraulic cylinder to be installed in a retrofit situation under an existing building.
An underground oil leak, particularly where there is a nearby aquifer, is a major environmental catastrophe. For this reason, some manufacturers have discontinued hydraulic elevators, while others have developed high-performance cylinder liners to contain any oil that could otherwise escape.
FIGURE 2-3 A below-grade hydraulic piston drives the car to a maximum height of about four stories.
In low-rise applications, hydraulic elevators are widely used and there are a great many currently in service. Some have above-ground cylinders, which solves a few problems but gives rise to others, such as dedicated space that is required, and greater complexity due to the nature of the hybrid traction and hydraulic design. Some hydraulic designs have telescoping pistons, which reduce the amount of excavation and permit greater vertical travel, at the expense of greater complexity. An advantage in the conventional single-cylinder, below-grade design is an intrinsic added degree of safety because in the event of rupture, the car can fall no faster than permitted by the escaping oil.
In a typical installation, submersible motor/pump units are bolted together and located in a 50- to 100-gallon oil reservoir, which is located in the machine room adjacent to the motion controller. The small motors are very reliable and long-lasting, because immersed in oil there is excellent heat dissipation and the windings, encapsulated in epoxy, are exceptionally well insulated and protected from grounding out.
There are a number of conditions that will cause an elevator to cease operation. One of these, in the hydraulic elevator, is elevated oil temperature in the reservoir. High oil temperature can have many causes, including among others aged and inefficient oil, low oil level (a leak!), inefficient pump operation, continuous operation of the elevator especially with heavy loading, high ambient temperature in the machine room, and so on. All these factors work together. You can have some idea where you stand by attaching a thermometer to the outside of the tank. The top of the tank should never be used as a catch-all, especially for cloth or similar objects that could impede heat dissipation. The machine room should have adequate ventilation, and if this depends upon a fan, failure of the fan motor could be an issue.
ASME A17.3, Safety Code for Existing Elevators and Escalators, Part IV, contains design and installation requirements specifically relating to hydraulic elevators. It opens with a declaration of scope, stating that Part IV is applicable to both direct plunger and roped-hydraulic elevators. Section 4-1 notes that hoistways, hoisting enclosures, and related construction are to comply with ASME A17.3, Part II.
Section 4.2, Mechanical Equipment, contains four provisions:
■ 4.2.1 states that buffers and bumpers are to be provided. Solid bumpers are acceptable instead of spring bumpers where the rated speed is 50 feet per minute or less.
■ 4.2.2 states that car frames and platforms shall conform to the requirements of Section 3.3.
■ 4.2.3 states that car enclosures are to comply with Section 3.4.
■ 4.2.4 states that capacity and loading are to comply with Section 3.7.
Section 4.3 pertains to driving machines:
■ 4.3.1, Connection to Driving Machine, states that the driving member of a direct plunger driving machine is to be attached to the car frame or car platform with fastenings of sufficient strength to support that member.
It is further stated that the connection to the driving machine is to be capable of withstanding without damage any forces resulting from a plunger stop.
■ 4.3.2, Plunger Stops, states that plungers are to be provided with solid metal stops and/or other means to prevent the plunger from traveling beyond the limits of the cylinder. Stops are to be designed and constructed to stop the plunger from maximum speed in the up direction under full pressure without damage to the connection to the driving machine, plunger, plunger connection, couplings, plunger joints, cylinder, cylinder connecting couplings, or any other part of the hydraulic system. For rated speeds exceeding 100 feet per minute where a solid metal stop is provided, means other than the normal terminal stopping device (i.e., emergency terminal speed limiting device) are to be provided to retard the car to 100 feet per minute with a retardation not greater than gravity, before striking the stop.
■ 4.3.3, Hydraulic Elevators, provides that hydraulic elevators that have any portion of the cylinder buried in the ground and that do not have a double cylinder or a cylinder with a safety bulkhead are to:
(a) Have the cylinder replaced with a double cylinder or a cylinder with a safety bulkhead protected from corrosion by one or more of the following methods:
(1) Monitored cathodic protection
(2) A coating to protect the cylinder from corrosion that will withstand the installation process
(3) A protective plastic casing immune to galvanic or electrolytic action, salt water, and other known underground conditions; or
(b) Be provided with a device meeting the requirements of Section 3.5 or a device arranged to operate in the down direction at an overspeed not exceeding 125 percent of rated speed. The device is to mechanically act to limit the maximum car speed to the buffer striking speed, or to stop the elevator car with rated load with a deceleration not to exceed 32.2 feet per second, and is not to automatically reset. Actuation of the device is to cause power to be removed from the pump motor and control valves until manually reset; or
(c) Have other means acceptable to the authority having jurisdiction to protect against unintended movement of the car as a result of uncontrolled fluid loss.
■ Section 4.4, Valves, Supply Piping and Fittings, provides in 4.4.1, Pump Relief Valve:
(a) Pump Relief Valves Required: Each pump or group of pumps is to be equipped with a relief valve corresponding to the following requirements, except as covered by (b):
(1) Type and Location: The relief valve is to be located between the pump and the check valve and is to be of such a type and so installed in the bypass connection that the valve cannot be shut off from the hydraulic system.
(2) Size: The size of the relief valve and bypass is to be sufficient to pass the maximum rated capacity of the pump without raising the pressure more than 50 percent above the working pressure. Two or more relief valves are permitted to obtain the required capacity.
(3) Sealing: Relief valves having exposed pressure adjustments, if used, are to have their means of adjustment sealed after being set to the correct pressure.
(b) Pump Relief Valve Not Required: No relief valve is required for centrifugal pumps driven by induction motors, provided the shutoff, or maximum pressure which the pump can develop, is not greater than 135 percent of the working pressure at the pump.
■ 4.4.2, Check Valve, states that a check valve is to be provided and so installed that it will hold the elevator car with rated load at any point when the pump stops or the maintained pressure drops below the minimum operating pressure.
■ 4.4.3, Mechanically Controlled Operating Valves, provides that they are not to be used. Existing terminal stopping devices consisting of an automatic stop valve independent of the normal control valve and operated by the movement of the car as it approaches the terminals, where provided, may be retained.
■ 4.4.4, Supply Piping and Fittings, states that they are to be in sound condition and secured in place.
■ Section 4.5, Tanks, contains in 4.5.1, General Requirements:
(a) Capacity: All tanks are to be of sufficient capacity to provide for an adequate liquid reserve to prevent the entrance of air or other gas into the system.
(b) Minimum Liquid Level Indicator: The permissible minimum liquid level is to be clearly indicated.
■ 4.5.2, Pressure Tanks, provides:
(a) Vacuum Relief Valves: Tanks subject to vacuum sufficient to cause collapse are to be provided with one or more vacuum relief valves with openings of sufficient size to prevent collapse of the tank.
(b) Gage Glasses: Tanks are to be provided with one or more gage glasses attached directly to the tank and equipped to shut off the liquid automatically in case of failure of the glass. The gage glass or glasses are to be located to indicate any level of the liquid between permissible minimum and maximum levels, and are to be equipped with a manual cock at the bottom of the lowest glass.
(c) Pressure Gage: Tanks are to be provided with a pressure gage that will indicate the pressure correctly to not less than 1.5 times the pressure setting of the relief valve. The gage is to be connected to the tank or water column by pipe and fittings with a stop cock in such a manner that it cannot be shut off from the tank except by the stop cock. The stop cock is to have a T or lever handle set in line with the direction of flow through the valve when open.
(d) Inspector’s Gage Connection: Tanks are to be provided with .25 inch pipe size valve connection for attaching an inspector’s pressure gage while the tank is in service.
(e) Liquid Level Detector: Tanks are to be provided with a means to render the elevator inoperative if for any reason the liquid level in the tanks falls below the permissible minimum.
(f) Handholes and Manholes: Tanks are to be provided with a means for internal inspection.
(g) Piping and Fittings for Gages: Piping and fittings for gage glasses, relief valves, and pressure gages are to be of a material that will not be corroded by the liquid used in the tank.
■ Section 4.6, Terminal Stopping Devices, provides that terminal stopping devices are to conform to the requirements of 3.9.1.
■ Section 4.7, Operating Devices and Control Equipment, provides in 4.7.1, Operating Devices, that operating devices are to conform to the requirements of 3.10.1 and 3.10.2, Top-of-Car Operating Devices, which state that top-of-car operating devices are to be provided and are to conform to the requirements of 3.10.3, except for un-counterweighted elevators having a rise of not more than 15 feet. The bottom normal terminal stopping device is permitted to be made ineffective while the elevator is under the control of the top-of-car operating device.
■ 4.7.3, Anti-creep Leveling Devices, states that each elevator is to be provided with an anti-creep leveling device conforming to the following provisions:
(a) It is to maintain the car within three inches of the landing irrespective of the position of the hoistway door.
(b) For electrohydraulic elevators, it is required to operate the car only in the up direction.
(c) For maintained pressure hydraulic elevators, it is required to operate the car in both directions.
(d) Its operation is permitted to depend on the availability of the electric power supply provided that:
(1) the power supply line disconnecting means required by 3.10.5 is kept in the closed position at all times except during maintenance, repairs, and inspections; and
(2) the electrical protective devices required by 4.7.4(b) do not cause the power to be removed from the device.
■ 4.7.4, Electrical Protective Devices, states that electrical protective devices, conforming to the requirements of 3.10.4, where they apply to hydraulic elevators, are to be provided and operate as follows:
(a) The following devices are to prevent operation of the elevator by the normal operating devices and also the movement of the car in response to the anti-creep leveling device:
(1) Stop switches in the pit
(2) Stop switches on top of the car
(3) Car side emergency exit door electric contacts, where such doors are provided
(b) The following devices are to prevent the operation of the elevator by the normal operating device, but the anti-creep leveling device required by 4.7.3 is to remain operative:
(1) Emergency stop switches in the car
(2) Broken rope, tape, or chain switches on normal terminal stopping devices when such devices are located in the machine room or overhead space
(3) Hoistway-door interlocks or hoistway-door electric contacts
(4) Car door or gate electric contacts
(5) Hinged car platform sill electric contacts
(6) In-car stop switch, where permitted by 3.10.4(t)
■ 4.7.5, Power Supply Line Disconnecting Means, states that they are to conform to the requirements of 3.10.5.
■ 4.7.6, Devices for Making Hoistway-Door Interlocks or Electric Contacts, or Car Door or Gate Electric Contact Inoperative, states that they are to conform to the requirements of 3.10.7.
■ 4.7.7, Control and Operating Circuit Requirements, states that they are to conform to the requirements of 3.10.9 and 3.10.12.
■ 4.7.8, Emergency Operation and Signaling Devices, states that they are to conform to the requirements of Section 3.1.1.
■ Section 4.8, Additional Requirements for Counterweighted Hydraulic Elevators, provides that they are to be roped so that the counterweight will not strike the overhead work when the car is resting on its fully compressed buffer. Counterweighted hydraulic elevators are to conform to the requirements of Section 3.2 where applicable. Where counterweights are provided, counterweight buffers are not to be provided.
■ Section 4.9, Additional Requirements for Roped-Hydraulic Elevators:
■ 4.9.1, Top Car Clearance, states that roped-hydraulic driving machines, whether of the vertical or horizontal type, are to be so constructed and so roped that the piston will be stopped before the car can be drawn into the overhead work. The top car clearance is to meet the requirements of 2.4.4.
■ 4.9.2, Top Counterweight Clearance and Bottom Counterweight Runby, states that where a counterweight is provided, the top clearance and the bottom runby are to conform to the following:
(a) Top Clearance is not to be less than the sum of the following:
(1) The bottom car runby
(2) The stroke of the car buffers used
(3) Six inches
The minimum runby specified is not to be reduced by rope stretch.
■ 4.9.3, Protection of Spaces Below Hoistway, states that where the hoistway does not extend to the lowest floor, the space below the pit is to be enclosed with permanent walls or partitions to prevent access.
■ 4.9.4, Piston Stops, states that piston stops are to be provided to bring the piston to rest at either end of the piston travel from maximum speed in the up direction, under full pressure without damage to the driving machine, piston, piston joints, cylinder, cylinder couplings, or any other part of the hydraulic system.
For rated speeds exceeding 100 feet per minute where a solid metal stop is provided, means other than the normal terminal stopping device are to be provided to retard the car to 100 feet per minute with a retardation not greater than gravity, before striking the stop.
■ 4.9.5, Piston Connections, states that:
(a) Equalizing Crosshead: Where more than one piston is used on the puller-type roped hydraulic elevators, an equalizing crosshead is to be provided for the attachment of the rods to the traveling sheave frame to ensure an equal distribution of the load to each rod.
(b) Equalizing or Cup Washers are to be provided under piston rod nuts to ensure a true bearing.
(c) Piston rods of the puller-type hydraulic elevators are to have a factor of safety of not less than eight based on the cross-sectional area at the root of the thread of the material used. A true bearing is to be maintained under the nuts of both ends of the piston rod to prevent eccentric loadings on the rod.
■ 4.9.6, Car Safety Devices, states that car safety devices conforming to the requirements of Section 3.5, except 3.5.2 are to be provided. Counterweight safeties are not to be provided.
■ 4.9.7, Car Speed Governors, states that car speed governors conforming to the requirements of Section 3.6 are to be provided.
■ 4.9.8, Sheaves, states that sheaves are to be cast iron or steel and are to have finished grooves for ropes.
The traveling sheaves are to be guided by means of metal guides and guide shoes. The guide shoes are permitted to be equipped with nonmetallic inserts. Sheave frames, where used, are to be constructed of structural or forged steel and are to be designed and constructed with a factor of safety not less than eight for the material used. Single continuous straps (known as U-strap connection) are not to be used for frames or as connections between piston rods and traveling sheaves.
■ 4.9.9, Slack-Rope Device: Roped-hydraulic elevators are to be provided with a slack-rope device and switch of the enclosed, manually reset type that will cause the electric power to be removed from the pump motor and the valves if the hoisting ropes become slack or are broken.
■ 4.9.10, Suspension Ropes and Their Connections: All elevators, except freight elevators that do not carry passengers or freight handlers and have no means of operation in the car, are to conform to the following requirements:
(a) Suspension ropes are to conform to the requirements of 3.12.1 through 3.12.3, 3.12.5, 3.12.8, and 3.12.9.
(b) The minimum number of hoisting or counterweight ropes used for roped hydraulic elevators is not to be less than two.
(c) The minimum diameter is to be 0.375 inches and the outer wires of the rope are to be not less than 0.024 inches in diameter. The term “diameter” where used in this section refers to the nominal diameter as given by the rope manufacturer.
The most common hydraulic elevator has a conventional configuration with a single below-grade cylinder directly below the car. Because of required excavation depth, height is generally restricted to four or five stories. A telescoping piston permits higher rises, at the cost of greater complexity. Combination roped-hydraulic systems allow the car to move farther than piston travel.
Hole-less hydraulic elevators, with two above-ground cylinders, are an option where high water table or bedrock preclude a conventional design. Where the site permits, the less complex conventional hydraulic elevator has been well-suited for low-rise, low-traffic installation. A downside is that they are less energy efficient than purely traction designs. High current draw when the pump starts under load places a greater demand on facility electrical resources, so for a new installation, alternatives should be weighed. The latest low-cost machine room-less traction elevators (see below) are strongly competitive in areas where previously hydraulic elevators were the clear choice.
Because of high startup current draw, in an outage emergency power may not be used to operate a hydraulic elevator, unless it is designed to do so. Typically, emergency power is used to lower the car to the next landing, and to open the doors. There the car rests until normal power is restored. In a low-rise building, occupants can use the stairs. In healthcare facilities, the emergency power system must be sized out to run the elevators throughout an outage.
Traditional elevator configurations include a machine room located at or below the lowest landing or above the top of the hoist. The machine room typically includes, for a traction elevator, separate electrical feeders for the motor (via VFD) and motion controller and for lighting, receptacles, and outlets in the machine room. For the motor, a dedicated disconnect must be located within sight in the machine room. Also in the machine room are the motion controller, VFD, motor with gearbox and related mechanism, and the drive sheave with pulleys and wire ropes. There may be a telephone, work table, and file cabinet for documentation. For a hydraulic elevator, the machine room consists of many of the same components. The difference is that rather than the type of motor and drive mechanism unique in a traction elevator machine room, the hydraulic elevator machine room houses an oil reservoir with submersible pump/motor and associated wiring and piping.
The machine room brings together many elevator components so they can be readily accessed for maintenance and servicing. The only downside is that valuable space within the building is not available for other essential services. To confront this problem, manufacturers developed the machine room-less (MRL) elevator, shown in Figure 2-4.
The MRL design was made possible by a new generation of smaller, lighter permanent magnet motors that permit installations consisting of the motor and associated components to be located in the hoistway without benefit of a machine room.
MRL hoisting methods allow a reduced sheave-to-rope ratio of 16:1 as opposed to the 40:1 ratio in the conventional traction elevator configuration. At the smaller ratio, a more flexible, higher-strength wire rope is used.
The MRL design incorporates motor, drive sheave, counterweight, and wire ropes as in both the geared and gearless traction elevators. In MRL elevators, the gear-less drive is preferred although either is possible. The MRL components are located in a space above the hoistway except for the motion controller, which may be located in a locked cabinet in the top floor hallway adjacent to the shaft door. MRL elevators may be either traction or hydraulic. MRL elevators do not have a fixed machine room at 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 permanent magnet motor works in conjunction with a VFD. This design eliminates the need for a machine room and saves space. 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. Most elevators have their controller installed on the top floor, but some are installed on the bottom floor. Some elevators have the hoisting motor located at the bottom of the elevator shaft pit. This is called a bottom drive MRL elevator. The controller cabinet may be installed in the door frame. MRL elevators sometimes use flat steel belts instead of wire ropes, permitting a smaller hoisting sheave. Machine room-less elevators in mid-rise buildings usually serve less than 20 floors. The traction mechanism may be located under the elevator cab as in some Schindler designs. Like the traction version, machine room-less hydraulic elevators do not have a fixed room to house the hydraulic machinery. In the MRL design, hydraulic machinery is located in the elevator pit. The controller is located on a wall near the elevator on the bottom floor. MRL hydraulic elevators like the traction models require less space.
FIGURE 2-4 The machine room-less motor is located on top of the car or elsewhere in the hoistway. (Wikipedia)
Rather than in a machine room, most components in MRL designs are in the shaft. The motor and drive mechanism may be on top of the car, under the car, at the top of the shaft, or at the bottom of the shaft. The motion controller is frequently located in a locked cabinet in the top-floor hallway adjacent to the hoistway door. Except for their compact size and unusual locations, components are similar to those in conventional traction or hole-less hydraulic elevators. Kone introduced the MRL design in 1996 and it is currently offered by many manufacturers.
In addition to freeing up valuable space, the MRL design uses less energy and initial cost is significantly lower. A significant disadvantage is that maintenance and servicing are more difficult, and workers have been injured. (Imagine doing dynamic vibration testing on the motor on top of a moving car!)
In a double-deck elevator, there are two attached cars, one on top of the other. They move together in the same shaft. The great advantage in a many-story building is that two adjacent floors can be served simultaneously, with half as many stops. The capacity of each shaft is doubled, cutting down on dedicated floor space on each story.
In some designs, one of the cabs serves as a freight elevator. During peak traffic periods, it becomes a second passenger car.
Worldwide, many double-deck elevators have been built, as many in Asia as in Europe and North America combined.
In densely populated areas where space is limited, multi-level parking lots have inclined ramps so that users can drive to the desired level. Some of these facilities have automotive elevators that carry cars and passengers to their destinations. Most of these are hydraulic elevators, and they must be rated for large loads to safely accommodate a heavy vehicle loaded with passengers and luggage.
Closely related are aeronautic elevators on aircraft carriers. Here considerable space is needed on deck for the runway plus nautical equipment, and that leaves room for only a few aircraft. Most of the 100 or so jets are stored in below-deck hangars, which is convenient for servicing and general maintenance. But how are they moved back and forth? Early aircraft carriers experimented with various methods such as moving the aircraft up and down inclined ramps, and using cranes to lift them. In the end, a nineteenth-century solution was adapted for this twentieth-century need, the hydraulic elevator.
In a typical aircraft carrier, most of the jets that are not in use are stored in the hangar bay, which is located two decks below the flight deck, directly under the galley deck. The hangar bay may be 110 feet wide, 25 feet high, and close to 700 feet long, over two thirds the length of the aircraft carrier. Besides aircraft, there is a large maintenance area with spare engines, extensive tools, and areas open to the outside for testing engines. Various sections are separated by sliding fire doors. There may be four gigantic aluminum hydraulic elevators, each capable of lifting two 30-ton jets simultaneously.
Stage elevators are essential for large theatrical productions. They permit elaborate settings to be assembled in advance, ready for action, and raised into place between scenes. Similarly, large orchestras complete with musicians and heavy pianos can be instantly deployed. These elevators are invariably hydraulic, with heavy steel-framed floors supported by massive pistons. Radio City Music Hall has four large stage lifts behind which are three smaller ones, so that sections of the set and orchestra can be moved as needed.
Residential elevators are used to transport elderly and handicapped persons between floors in their own homes, often permitting partially disabled persons to live at home for many years without relocating to a ranch-style building. These home lifts are permitted to be less complex, and they are generally slower and less powerful than commercial elevators, so the cost is far less. Safety systems such as shaft and car door interlocks, safeties, and emergency phones are required. ASME A17.l, Section 5.3 covers residential elevators. This category does not include elevators in multi-family occupancies.
Dumbwaiters are intended to carry light freight between floors, never human passengers. They are frequently installed in restaurants and hotels, to connect kitchens to dining rooms on higher levels. Because of the lighter, inanimate loads, some of the usual safety features are not required. The platforms are much smaller than those in passenger and conventional freight cars, with three-foot door heights. At each landing there is a control panel, permitting calling, door control, and choice of destination.
The Paternoster consists of a series of moving compartments. It resembles the humanlift, found in multi-story industrial buildings, where the rider stands on a small platform, gripping a handhold.
The scissors lift is a mobile work platform that allows maintenance workers and painters to easily access outside walls and inside walls in industrial building that have high ceilings. Scissors lifts are used extensively by electricians in servicing light fixtures in high-bay areas. They can also be used as long-term fixed elevators where there is no space for pit, machine room, counterweight, or hydraulic cylinder.
Rack and pinion elevators are powered by a motor-driven pinion gear. They are often installed on the outside of a building under construction, and can easily be moved to the next work site.
Belt elevators are used extensively to move loose material such as grain and coal. Typically the loads are moved up inclined planes. Pit mines make extensive use of these elevators. Vertical elevators in underground mines, used to transport materials, equipment, and workers, are often large, powerful, and challenging in terms of design, installation, and maintenance. Electrical systems are sometimes in areas classified as hazardous.
A survey of elevator types should include a description of the major elevator manufacturers. There are relatively few compared to the number of household appliance or automobile manufacturers. This is because elevator systems are very complex. They vary widely in height, with shafts, traveling cables, and steel ropes sometimes thousands of feet long. Often there are group installations of multiple powerful high-voltage electric motors and elaborate control and communication systems. The entire assembly has to conform to detailed safety codes, which vary depending on the location and elevator type.
Here is Wikipedia’s list of current elevator manufacturers. We will focus on a few of them:
■ Acorn Stairlifts
■ Aichi
■ Anlev Elex
■ Anton Freissler
■ Canton Elevator Incorporated
■ Cibes Lift
■ Delaware Elevator Manufacturing
■ Delta Elevator
■ FUJIHD
■ Fujitec
■ GEDA USA
■ Hitachi
■ Hosting Elevator
■ Hyundai Elevator
■ KLEEMANN
■ Kone
■ LG Elevator
■ Liftech SA
■ Marshall Elevator
■ MEI-Total Elevator Solutions
■ Mitsubishi Electric
■ Orona Group
■ Otis Elevator Company
■ Schindler Group
■ Servas ascensores
■ Sicher elevator
■ Sigma Elevator
■ Symax Lift
■ Stannah Lifts
■ ThyssenKrupp
■ Toshiba
■ Ulift
Hitachi is moving forward with its UAG Series SN1 and OUG Series ON1 machine room-less elevator systems. Hitachi offers advanced functions, some standard and some optional, including simplex, duplex, and group control, automatic return function, independent and attendant parking and rush-hour schedule operation, interphone system, floor lockout and door nudging, abnormal speed protection, and out of door-open zone alarm.
Additionally, when the car stops out of the door-open zone, it will move at slow speed to the nearest floor to release passengers. In the event of door overload, such as when passengers get their fingers, hands, or personal belongings caught in the door, the system automatically senses this and either recloses or reopens the doors to prevent injury.
Micro-leveling automatically corrects the car level when there is a difference between the car and the landing floor. In the event of a power failure, an emergency light inside the car is automatically activated. A battery-powered emergency supply allows the operation of light and alarm bell. A multi-beam door sensor installed at the edge of doors, in the event that beam paths are obstructed, will keep the doors open.
As of 2018, Hyundai has produced over 28,000 elevators. The company states that safety, ride quality, and space efficiency are combined in optimal elevator systems that will enhance the value of buildings. Speeds are up to 18 meters per second and maximum passenger capacity is 30. Hyundai manufactures observation, hospital, and freight/automobile elevators with a maximum rated load of 5,000 kg. All products can be custom-made to suit each building.
Kone, a Finnish elevator manufacturer founded in 1910, conceived the machine room-less elevator in 1996. Over the years throughout the world Kone has bought and sold many corporations. At various times it has invested heavily in forest machines, cargo handling, and tractors. Currently, it has narrowed its focus and expanded its elevator business. Due to environmental and energy efficiency concerns, Kone announced in 2007 that it would no longer manufacture hydraulic elevators.
In 2011, Kone built a new headquarters building named the Kone Center in Moline, Illinois.
In 2013, the firm introduced Kone UltraRope, designed to replace steel rope in traction elevator systems. It will permit building heights up to one kilometer. UltraRope is lightweight, with a high-friction coating and consequently reduces energy consumption in high-rise applications. With a higher resonant frequency than steel rope, cable sway is reduced in long runs, with less possibility of cable and shaft damage.
Mitsubishi Electric also offers machine room-less elevator systems. Elevator Group Control System ΣAI-2200C incorporates fuzzy logic to provide comfortable elevator operation and ride under changing usage conditions. The system incorporates intuitive control to provide smooth operation. When a hall call button is pressed, the optimum car responds based on waiting time, travel time, current car occupancy, and projected energy consumption.
Otis is the world’s largest elevator manufacturer. We told the story in Chapter One of Elisha Otis’s invention in 1852 of safeties, which lock the car to guides fastened to the hoistway walls so that it can’t fall into the pit if the steel ropes fail.
The Otis brand is well-known throughout the world. The firm maintains extensive research and testing facilities, and watches its competitors, who in turn watch Otis for industry-changing innovations, such as Kone’s machine room-less systems.
Schindler Group, like many of its competitors, has enthusiastically embraced the MRL concept. The company currently employs over 58,000 people in the United States, Switzerland, India, Spain, Slovakia, Brazil, and China. Schindler was founded in 1874 in Switzerland and soon began manufacturing many types of machines including elevators. It rapidly expanded throughout Europe, the United States, South America, and China.
Schindler has introduced Miconic 10, a proprietary control system. Passengers enter their destinations in a wall-mounted keypad while waiting for a car. The system groups riders with the same destination to a specific car, vastly increasing efficiency and reducing waiting time.
ThyssenKrupp has continuously embraced new technologies such as double-decker cars, rope-less horizontally-moving cars, moving walks, heavy-machinery freight, and vehicle elevators. The company has 670 subsidiaries.
1. The most common type of elevator is:
A. machine room-less
B. hydraulic
C. traction
D. aeronautic
2. Traction elevators are characterized by:
A. water power
B. freight only
C. an operator
D. steel ropes
3. The gearless design permits car speeds in excess of:
A. 100 fpm
B. 500 fpm
C. 1000 fpm
D. 2000 fpm
4. Compensation is needed when vertical travel is greater than:
A. 100 feet
B. 250 feet
C. 500 feet
D. 1000 feet
5. Compensation consists of:
A. a greater amount of insurance
B. hanging chain to add weight
C. good judgment on the part of technicians
D. higher speed for a smoother ride
6. Steel belts can be used rather than steel rope. They require:
A. frequent lubrication
B. more power to run
C. less material weight
D. a skilled operator
7. Traction elevator motors with gearless drives:
A. are smaller
B. operate at lower RPM
C. require more maintenance
D. can be noisy
8. Roping configurations in a traction elevator:
A. consist of suspension ropes attached to the top of the car
B. may be underslung
C. pass down to the counterweight
D. any of these
9. The gearless design requires:
A. higher car speed
B. a smaller sheave
C. frequent lubrication
D. frequent rebuilding
10. In a regenerative drive system, energy is returned to the grid:
A. when a full car is ascending
B. when an empty car is descending
C. when a full car is descending
D. when the car is stopped
For answers, go to Appendix A.
