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HomeMy WebLinkAbout202.005 - Elevator Operation and Design STANDARD OPERATING PROCEDURES MANUAL TACTICAL OPERATIONS 202.005 ELEVATOR OPERATION AND DESIGN EFFECTIVE: OCTOBER 2007 Current Revision Date: 5/29/19 Next Revision Date: 5/29/22 Author’s Name/Rank: Christian Palmer, Fire Captain Review Level: 1 Administrative Support: Sherrie L. Badertscher Management Analyst II PURPOSE The purpose of this policy is to provide information on the operation and design of common elevators found in the city of Fresno. APPLICATION Personnel should consider this information when using elevators during emergency operations or performing rescue of those using elevators. OPERATIONAL POLICY This section intentionally left blank. OPERATIONAL GUIDELINE This section intentionally left blank. PROCESS This section intentionally left blank. INFORMATION Elevator Operation and Design Although all high-rise elevators are electrically powered and perform the same basic function, there are a variety of different elevator designs. A presentation on all the different types of elevator systems and individual items unique to each one would fill an entire volume. Because elevator systems are so different and can be very Section 202.005 Page 1 of 7 complex, first-hand knowledge of each particular elevator system should be developed through effective pre-fire planning with pertinent elevator operation cards, which are placed in a building lock box. This section will cover basic elevator design and operation. The various parts of the elevator are depicted on the following pages. Hoistways Elevator hoistways are the enclosed vertical shafts in which elevator cars travel. In buildings with multiple banks of elevators, cars in close proximity to each other utilize a common hoistway. Many of the newer high-rise buildings are equipped with multiple-bank elevator systems in which elevator cars service only a certain number of floors. Example: 20-story building--the low-rise bank serves floors 1 through 10 and the high-rise bank serves floor 1 and floors 11 through 20. Generally, the only location where transfer between split-bank elevators is possible is at ground level. Hoistways contain vertical rails that guide and stabilize each individual elevator car during travel. Final limit switches are mounted on the rails, which act to limit the maximum upward and downward travel of each car. Elevator counterweights are found in the hoistway, generally at the rear of the shaft. Elevator Door Arrangements Buildings over three stories in height are required to have mechanical ventilation provided to the hoistway. Hoistway doors at each floor served by an elevator car are opened and closed by movement of the elevator car door when the car is level with the floor landing. There are four (4) basic types of doors used on elevator hoistways and cars. 1. Center-opening doors. 2. Two-speed doors. 3. Single-slide doors. 4. Swing-hall doors. Hoistway and elevator car doors may be of the same type or may be any dual combination of the basic types listed, dependent upon the age and manufacture of the elevator system. Power System High-rise elevators are almost universally driven by electric motors located in a machinery room above the hoistway. Section 202.005 Page 2 of 7 Power to the drive motor may range from 220 volts to 660 volts and up to 150 amps. Voltage from the machinery room through cables to the elevator car will usually not exceed 220 volts and 5 amps. Some older installations utilize alternating current (AC) to power the elevator drive system; however, the majority of high-rise elevators are equipped with motor generators, which convert alternating current to direct current (DC) to power the drive motor. The direct current motor generator system provides smoother, more positive movement of elevator cars and operates more efficiently than other designs. Elevator drive motors are connected through a brake mechanism to a drive sheave, which controls the cables (referred to as hoisting ropes) that move the elevator car in the hoistway. The drive motor, brake mechanism, and drive sheave are often built into one assembly, referred to as an elevator machine. The brake mechanism is a safety device, preventing movement of the elevator car anytime power is not being applied to the drive motor. Located in the machinery room, usually separate from the drive system, is a governor device connected by cable to the elevator car. The governor device acts to engage safety mechanisms, which slow or stop the elevator whenever its vertical travel exceeds a predetermined speed in feet per minute. If the elevator car is traveling too fast in a downward direction, the governor cable will automatically cause the safety devices on the elevator car to grip the hoistway guide rails and stop the car. If the upward travel speed becomes excessive, the governor device will cause a shutdown of electrical power to the drive motor and actuate the brakes on the motor. Electrical shutoff switches that control the power to the drive motors are normally located in the machinery room. A separate switch is required for each individual elevator drive motor and should be numbered to correspond with the numbering of individual elevator units. Some of the newer high-rise buildings are equipped with emergency power systems, which may be used to perform selective elevator functions if the normal power supply should fail. Because of modifications and revisions made to applicable codes during recent years, the existence of a standby emergency power system in a building does not automatically ensure emergency operation of elevators. This information should be obtained from building management personnel and confirmed by actual field testing. Elevator Cars Elevator cars are constructed of a cage of light metal or metal-backed decorative panels supported by a heavy steel vertical sling or upright frame. The steel double beam forming the top cross member of the sling is referred to as the crosshead and to this are fastened the hoisting ropes and upper, guide shoes. The bottom cross member, of equally heavy construction, is called the safety plank and supports the Section 202.005 Page 3 of 7 car floor or platform. Attached to the safety plank are the car safety mechanisms and, the lower guide shoes. The car floor is usually constructed of an angle iron or channel iron frame on top of which are two levels of wood flooring and a finished surface of linoleum, rubber, asphalt tile, or carpeting. Often a sheet of light-gauge steel encloses the under surface of the car floor. Freight elevators may be equipped with heavy steel, diamond-plate flooring. The guide shoes, bolted to the upper and lower cross members, keep the elevator car in sliding contact with the hoistway guide rails to prevent sway or lateral movement. The safety mechanisms attached to the lower cross member are activated by the governor device and are designed to stop the car by clamping the guide rails if the car descends too fast or falls due to broken hoisting ropes. On lower speed cars, safety mechanisms are of an instantaneous type and will stop the car in a very short distance. On high speed cars to prevent injuries to passengers, the safety mechanisms are applied gradually to stop the car within a specified distance. The dead weight of an average elevator car may vary from 1,500 to 3,000 pounds, with large capacity or industrial elevator cars weighing as much as 5,000 pounds. The live weight (passenger load) permitted in elevator cars are normally computed at 150 pounds per square foot of floor area. Counterweights are used on elevator cars to permit a balanced operation at all levels and to allow the use of smaller driving machinery. Normally, the counterweight equals 40 percent more than the total weight of the car. The hoisting ropes (cables) fastened to the top cross member of the elevator car support the total weight of the elevator car and provide vertical movement. The total number of hoisting ropes attached to an elevator car will vary according to the weight of the car (usually numbering between two and six). The governor rope, which activates the safety mechanisms, is also attached to the car. Other ropes that may be attached to the car include counterweight ropes, compensating ropes or chains to balance the weight of hoisting ropes, and electric cables to supply electrical power to the car. Current building code provisions require elevator cars be equipped with emergency exits. Most elevators will have an emergency exit at the top of the car. On older elevator cars top exits are required to be openable from both inside and outside the car without the use of special tools. On new cars the top exit may be opened only from the outside. Section 202.005 Page 4 of 7 Controls Electric elevators in high-rise buildings are all designed to operate under the same basic control method. However, total control systems will vary from simple automatic self-service controls found in older buildings to the sophisticated computerized multi-unit control systems in the newest, high-rise buildings. Elevator controls are covered under the following categories: 1. Lobby control panels. 2. Call switches. 3. Car control panels. 4. Photo-detector devices. Lobby Control Panels Lobby control panels vary in appearance and total function. These panels are generally equipped with special emergency service or bypass switches. Activation of this switch to the on position will cause the elevator controlled by the switch to immediately disregard all activated call buttons, return the elevator car to ground level, and open the elevator door. The system will stay in this mode unless a selective mechanical control override is used on the individual car or the system is restored to automatic operation. Emergency recall of all elevator cars to the lobby under fire conditions is required for four (4) very important reasons: 1. To prevent smoke or fire from entering cars or hoistways through open car and hoistway doors. 2. To reduce the possibility of occupants becoming trapped in cars at dangerous locations. 3. To make it easier to account for all elevator cars. 4. To provide access to elevators for Department members. Some new elevator installations are equipped with control panels with displays indicating floor location of individual cars and the direction in which they are traveling. Many lobby panels provide key switches that will shut off the motor generators supplying electric power to the elevator drive motors. Section 202.005 Page 5 of 7 Call Switches Elevator call switches are located at each landing served by an elevator as a means of summoning an elevator car to the floor. These switches, or buttons as they are more commonly referred to, are either mechanical switches activated by a slight pressure or electronic switches activated by completion of a circuit to ground through the person touching the button. Activation of a call button causes relay equipment in selector apparatus at the machinery room or computer to move an elevator car to the requested floor location. Laboratory tests and actual experiences have shown some mechanical and electronic touch buttons can be activated by moderate heat sources that are present under fire conditions (4500 F to 5000 F) or by moisture in call switches or relay and selector equipment. The possibility of malfunction of such systems reinforces the need for emergency service features, which will provide a method of placing elevator cars out of service at ground level, allowing manual operation by firefighting members. Car Control Panels Individual panels inside each elevator car provide control over the car allowing movement to a desired location and provide various other features. Floor selector switches or buttons are, in most cases, identical in design and operation to call switches and are subject to the same possible malfunction under fire conditions. All electrically operated elevators are required to have an emergency stop switch incorporated into the car control panel. Activation of the emergency stop switch will cause a shutdown of power to the elevator drive motor and bring the car to a safe stop regardless of its position in the hoistway. Elevators utilizing power operated doors are required to have a close-door switch which, when activated, will cause the car door to close and remain closed until the door opening mechanism is engaged by activation of another switch or movement of the elevator car to another floor. Alarm buttons located on car control panels are required to sound an audible alarm within the building and may be supplemented with, or used in lieu of, telephones installed in the elevator car. Elevator telephones may terminate within the building or be connected to an outside central telephone exchange or security service. Car control panels in most high-rise elevators are equipped with switches that will override the automatic control features placing the individual car on manual operation. New elevator installations provide a key switch sometimes referred to as a firefighters' service switch, which allows manual operation of the elevator and provides certain added safety features. The additional safety features include the requirement of depressing the door-open button to open elevator doors on arrival at Section 202.005 Page 6 of 7 the selected floor. In this mode, the door-open button must be depressed until the doors are in a fully opened position. If released prior to full opening, the doors will automatically close. Photo-Detector Devices Many new elevators are equipped with photo-detector (electric-eye) devices, which cause elevator doors to reopen whenever the light beam is broken during the door- close cycle. Some elevators with this feature have a force-close mechanism, which will override the photo-detector device if the light beam is broken for a preset time (usually 30 seconds). Elevators equipped with the photo-detector device, but lacking the force-close mechanism, may remain open indefinitely at a fire floor if the smoke reaches a density sufficient to obscure the light beam. Doors equipped with photo detector devices are required to have a push-type switch for use by elevator occupants who will override the photo-detector device and cause the doors to close immediately. This switch is usually labeled “TO BE USED IN CASE OF FIRE ONLY”. Miscellaneous controls included in elevator car panels are usually installed for maintenance or service functions. These functions include items such as convenience lighting, car ventilation, etc., and will vary with the age and manufacture of the elevator. In certain buildings service to one or more floors by elevator may be restricted for security reasons. In order to gain access to these floors, a special key switch, located next to the floor selector button, must be activated. Normally, the emergency service switch key may be used to activate a floor selector lock-out switch. DEFINITIONS This section intentionally left blank. CROSS-REFERENCES No cross-references recognized. Section 202.005 Page 7 of 7