Limit Switches, Buffers, Counterweights, Guide Rails, Deflector Sheaves Flashcards
Limit Switches
-located at the ends of the shaftway
-slowdown, normal and final limits
-normally closed and will open when activated by the car cam
Up normal limit switch
-forces elevator to change direction to down
-positioned 2” past top terminal landing
Down normal limit switch
-forces the elevator to change direction to up
-usually positioned 2” past bottom terminal landing
Up final limit switch
-uppermost switch in the shaftway
-removes all power from safety circuits
-1” above Up Normal Limit switch
-should never be activated under normal operation
Down final limit switch
-lowermost switch in the shaftway
-removes all power from safety circuits
-located 1” below the Down Normal Limit switch
-should never be activated under normal operation
Slowdown limit switches
-amount of switches will vary based on elevator speed
-slow moving elevators will have one before the Up Normal and one before the Down Normal
-located 5-7 feet before normal switches
High speed limit switch
-on high speed elevators exceeding 250fpm
-added safety to slow the elevator down in emergency conditions
-the faster the car, the more high speed limits are added
2 configurations of limit switches
-side facing
-front facing
Where are normal limit switches located
2” past terminal landings
Where are final limit switches located
Normally 1” past normal limit switches
Limit switch cam
-Cam on the side of the elevator that extends to the height of the cab
-aligned to be able to hit every limits switch if necessary
How much how much does the counterweight weigh
40% more than the elevator
What are test weights
-Used for weight testing the elevator and brake weight testing
-carts are 500lbs (100lbs cart and 8 50lbs weights inside)
Purpose of the counterweight
-Gives balance to the elevator system
-makes it easier for the motor to move the car
Purpose of the guide rails
-provide surface for the safeties to deploy
-guide the elevator while it travels up and down
Guide rail sizes
-8lbs x 16’ typically used for counterweights
-12lbs x 16’ used for elevators (standard)
-16lbs x 16’ used for freight elevators
Main purpose of the deflector sheave
To align the ropes to the hitch plates of the elevator and the counterweight
What is a sling
The car frame
Where is the deflector sheave
-overhead traction: in the motor room or attached to the hoisting beam
-basement traction: in the secondary
2 types of buffers
-Spring buffer(200fpm or less)
-oil buffers(200fpm or more)
What is a buffer
A device designed to stop descending car or counterweight beyond its normal limit
Once compressed, oil buffers must decompress in ______ or must be replaced
90 seconds
Buffer switch
-part of the safety circuit
-if switch is hit, it cuts power to the safety circuit and shuts down the car
How are buffers installed
-buffers are mounted to buffer stand
-buffer stand is mounted to the pit channel
-pit channel is mounted to the guide rails
