When large number of persons must be moved between a limited numbers of building levels, escalators are extremely effective and greatly reduce the number of elevator cars.
Elevators and stairwells are still required. Elevators are required for handicapped persons and freight movement between levels. Stairwells are required by fire codes. Escalators can be operated as a one-way system for quick egress from one level to the lower levels, and if the system is not operating, they can be used as stairways.
One has to stand in a step & it takes him/her up/down horizontal destination.
Escalators are elevator meant for vertical transportation of people.
These are power driven stairs.
These stairs have continuous operation without the help of any operator.
The escalator is in the form of an inclined bridge spanning between floors. Two precision made roller hauling chains travels over the sprocket pulling. The endless belt of steps. Slope of stairs 30° horizontal, entry stage of 0.8 to 1.2 m.
Standard Escalators are classified as standard or modular. The components of escalator include –
(i) The structural assembly is a welded steel frame that may require only infrequent inspections once the unit is installed.
(ii) The drive apparatus includes the electric driving motor, sprockets, and a drive chain. The major maintenance requirements for the drive apparatus are periodic lubrication and drive-chain, breaks or fails.
(iii) Emergency breaker the controller consists of the electrical circuitry of contacts, relays, and circuit breaker. Normal electrical inspections of the controller are scheduled as preventive maintenance.
The main control for the escalator is located near the drive apparatus, and key-operated switches are located at both ends of the escalator. These switches will start, stop, or reverse step movements.
(v) Handrails used by the handrails are driven from the top sprocket of the escalator. The normal maintenance requirement is to synchronize the speed of the handrail to the steps. The comb-plate assemblies at the top and bottom must be cleared of all debris, normally a housekeeping function unless an object is lodged in the assembly.
(vii) The balustrade assembly requires minor maintenance-just keeping the assembly intact and free of clothing catches. Its major requirement is a house keeping task-keeping it polished and clean. The drive assembly of the standard escalator drives the top sprocket, which in turn pulls the steps upward.
Modular escalators are used if the total rise is in excess of 7.5 m. The energy requirements to pull the steps upward become excessive for rises greater than 750 cm. These units have additional drive machines mounted at various points on the truss. This eliminates the need for a separate drive apparatus area.
All driving machines are of the same size; hence each is smaller, which increases the overall efficiency of the total system. As drive units are spaced throughout the truss assembly, chain tension maintenance is greatly reduced, and component wear characteristics are lower, which reduces major maintenance and replacement requirements. Drive units are spaced 600 to 750 Cm. apart, depending on the step width.
All escalators must be equipped with a governor speed control system. If the steps are moving too fast or too slow, the governor stops the system and prevents step reversal by setting the service brake.
Design of escalator:
The standard speed of escalators is 27 m/min. but most codes allow a top speed of 37.5 m/min. two widths measured between balustrades. Are available. 80 cm. with a passenger capacity of 5000 persons per hour; and 120 cm with a capacity of 8000 persons per hour.
The 80 cm size has a step width of 60 cm and will accommodate one adult and one child side by side. The 120 cm size has a step width of 90 cm and will accommodate two adults.
The entire stairway mechanism is built around a bridge-type truss which is supported at top and bottom from beams incorporated in the building structure.
An electric drive motor is located in the top and section of the stairway, driving through worm gear, sprocket, and chain. Two motor sizes are standard: 10 horsepower for the 80 cm stair; and 15 horsepower for the 120 cm stair.
Escalators may be situated (i) criss-cross, (ii) parallel, (i) criss-cross arrangement is preferred in as much as it requires minimum space. For department stores, however, the plan should provide the most expansive view of the floors and encourage cross-circulation.
Safety of escalator:
The electric stairway is extremely safe. All side surfaces are smooth; handrails are so designed that fingers cannot be caught under them, and the top and bottom comb-plates are trip-proof, providing safe transfer to and from the moving steps.
A service brake is mounted on the motor shaft. This is applied whenever a stop button, overload relay, speed governor, or step chain tension which is opened.
For additional protection an emergency brake is mounted on the top sprocket assembly and is mechanically applied if the main drive chain breaker, escalator becomes motionless. People may then walk or down as on any stairway.
If required by a local code, speed governor is mounted on the motor. This cuts of power and applies the service brake in case of either over-or under speed
Well way protection- Local fire code will govern well way protection to be provided. There are general methods in use –
1. Smoke Guard:
An 45 cm deep fireproof apron is placed around the well way at each ceiling opening. Sprinkler head are placed 112 cm around the guard each head protected from its neighbor by a shield. This shield will prevent cooling spray from any head making an adjacent one in operative spray nozzle- High violating spray nozzles are use.
This produces deep fine. The door at each landing are normally open but will closed by means of the operation of fusible links. The doors are not locked after the functioning of the links but can be opened as any normal hinged door.
Good lighting is essential. This is not furnished as a part of the escalator. Usually, light sources are placed in the underside of the stairway above, either in covers or individual down lights. Light should be evenly distributed and free of shadows. A continuous luminous strip in the balustrade is very effective.
A considerable amount of work must be performed by others to complete an electric-stairway installation. This will include stairway truss supports, floor-opening framing and enclosure, stairway enclosure, power for driving motors, lighting, fire protection, and a pit for basement stairways.
Selection Consideration for Hotel –
(i) Expected population persons per sleeping room Normal 1.3
(ii) An interval of 30 sec and is desirable.
(iii) A 5 mm capacity of 13% of building population is safe.
(iv) Automatic electronic supervising count.
(v) Car capacity is 2500, 3000
(vi) One service car per 10 passenger cars. One car for 0.2787 Sqm.
(vii) Service car 4000 cm
(viii) Doors 135 cm
(ix) Service elevator should have a shaftway door at every level plus easy access to the truck down or other freight entrance & well as the lobby.
Maintenance of Escalators –
Maintenance of escalators shall be done on the same lines as those of the lifts through a service contract with the installation contractor during the guarantee period.
After the expiry of the guarantee period arrangement shall be made for receiving regular servicing including regular repairs and replacement of defective parts, by competent persons at such intervals as may be required for the type of equipment and intensity of the operation demand.
The escalators are installed in spaces not enclosed as in the case of lifts, hence require more attention for protection against possible misuse, overloading and again probable damage, Protection against these shall be ensured.