Vertical Transportation Flashcards
Vertical transportation includes
passenger & freight elevators, escalators, dumbwaiters, vertcial conveyors, moving ramps, wheelchair lifts, platform lifts, stairs, ramps, ladders
Hydraulic elevators
car is lifted by a plunger/ram set directly below the car in the shaft
ram operates in an oil-filled cylinder the same height as the car must travel (shaft goes into ground)
limited to 2-6 stories, lower speed
in holeless or roller chain version, the shaft stands alongside next to car in shaft
Electric elevators
all operate by using counterweight over a sheave on cables (called ropes), driven by motor, traction of ropes on sheaves drives car (so called traction elevators)
gearless traction: motor directly connected to sheave, higher speed
geared traction: slower, but more flexible config., where ropes are pulled more remotely
ropes can be in double or single wrap, indicating loops over the sheave; double is faster, but shortens life span of ropes
1:1 roping: rope is attached to counterweight, 2:1 roping is when rope loops around counterweight on a second sheave, makes counterweight travel twice as far, but doesn’t require as much weight to lift - smaller motor needed
Elevator operations
operations means user interface
types: single automatic - single call button on each floor, single button for each floor in car, car can only be called if no one’s using it, person using it gets exclusive control
selective collective operation: car remembers and answers calls in one direction, when done, switches to other direction, not in use defaults to lobby (ok for light use)
group automatic operation: many elevators in one bank, deploys mult. cars in most efficient manner
destination floor guidance system: AI who puts people going to same/near floor in same car, riders select floor at central kiosk
Elevator controls
controls means motor/machine interface
unit multivoltage or Ward-Leonard: old school, three motors (AC motor drives DC generator, drives DC motor), noisey, low efficiency, one one avail. til 1980s
silicon-controlled rectifier (SCR) or thyristor: just variable DC generator to DC motor, lower power output, still inefficient
variable-voltage, variable frequency (VVVF): AC uses rectifier and inverter to make DC power, that drives an AC motor able to make 3-phase AC currents, is solid state, fast, dependable
Elevator safety devices
main brake on sheave comes on when power is cut off
a governor tracks car speed, applies brake if too fast
safety rail clamps also brake in an emergency
car buffers stop a car if it travels too low (but not from a dead-fall)
hoistway door interlocks prevents elevator from operating if hoistway doors aren’t closed/locked
safety edges on auto doors activate a switch to reopen if something touches them
proximity detectors (maybe photoelectric) do the same when obj. is present in door path
weight sensors prevent overloading
telephones, alarm buttons, escape hatches & ropes for emergency exiting
backup power sometimes required so at least one car can operate at a time, return all to lobby
firefighters can override emergency mode with a key
all must be ADA compliant
Elevator design considerations
capacity, speed, number of cars, roping method, machine room layout, control system
based on handling capacity of 5 min. peak period
speed determined by number of floors served + capacity
car capacity + speed determines number of cars, along with max. wait times (for offices, 30-35 sec., for hotels, 70 sec.+)
doors speed counts: center opening, single speed is commonest, side opening doors move telescopically to make faster; bigger clear space means faster entry/exit times
Very tall buildings + elevators
not economical or wait time efficient to have all cars serve all floors
max = 15 floors for a car to serve
can have separate shafts for elevators serving different floor levels (space inefficient)
sky lobby: high-speed elevators go to intermediate floor lobby, then to floor-serving elevators; shafts do not extend full height of building
stacked or double stacked cabs: two cars attached, go to upper floor for odds, stay on main level for evens
Elevator hoistway/pit
hoistway allows car travel, has guiderails, control machines, is a dedicated, fire-rated, enclosed space (1-3 floors, 1 hr; 4+ floor, 2 hr)
emergency illumination required throughout
can’t have more than 4 cars in shared hoistway & if they serve the same floors, must be divided further
pit for controls, car buffer, needs lighting, ladder, poss. sump
Machine rooms
best place = ab. hoistway, usu deeper than hoistway bc of all the machine clearances
must be held off from top floor alot, and be tall, so they poke out of roof a lot
machine-roomless elevators have controllers in hoistway itself, not separate room, only work in low/midrise, are more efficient, quieter
Freight elevators
five classification groups: A (general), B (motor vehicles), C1 (trucks), C2 (load of truck only), C3 (smaller increments of truck loads)
Non-public stairs
Winders (tapering must be equal), circular (inside arc cannot be less than twice width of stair), spiral (greater allowable riser ht, so you get a 6’6” headspace, but not more than 9.5”)
Stair minimums
min width = 36”, or if > than 50 occupants, 44”
handrails max project 4.5” both sides (9” total)
