Limit Switches, Buffers, Counterweights, Guide Rails, Deflector Sheaves

Question 1

Limit Switches

Answer 1

-located at the ends of the shaftway
-slowdown, normal and final limits
-normally closed and will open when activated by the car cam

Question 2

Up normal limit switch

Answer 2

-forces elevator to change direction to down
-positioned 2” past top terminal landing

Question 3

Down normal limit switch

Answer 3

-forces the elevator to change direction to up
-usually positioned 2” past bottom terminal landing

Question 4

Up final limit switch

Answer 4

-uppermost switch in the shaftway
-removes all power from safety circuits
-1” above Up Normal Limit switch
-should never be activated under normal operation

Question 5

Down final limit switch

Answer 5

-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

Question 6

Slowdown limit switches

Answer 6

-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

Question 7

High speed limit switch

Answer 7

-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

Question 8

2 configurations of limit switches

Answer 8

-side facing
-front facing

Question 9

Where are normal limit switches located

Answer 9

2” past terminal landings

Question 10

Where are final limit switches located

Answer 10

Normally 1” past normal limit switches

Question 11

Limit switch cam

Answer 11

-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

Question 12

How much how much does the counterweight weigh

Answer 12

40% more than the elevator

Question 13

What are test weights

Answer 13

-Used for weight testing the elevator and brake weight testing
-carts are 500lbs (100lbs cart and 8 50lbs weights inside)

Question 14

Purpose of the counterweight

Answer 14

-Gives balance to the elevator system
-makes it easier for the motor to move the car

Question 15

Purpose of the guide rails

Answer 15

-provide surface for the safeties to deploy
-guide the elevator while it travels up and down

Question 16

Guide rail sizes

Answer 16

-8lbs x 16’ typically used for counterweights
-12lbs x 16’ used for elevators (standard)
-16lbs x 16’ used for freight elevators

Question 17

Main purpose of the deflector sheave

Answer 17

To align the ropes to the hitch plates of the elevator and the counterweight

Question 18

What is a sling

Answer 18

The car frame

Question 19

Where is the deflector sheave

Answer 19

-overhead traction: in the motor room or attached to the hoisting beam
-basement traction: in the secondary

Question 20

2 types of buffers

Answer 20

-Spring buffer(200fpm or less)
-oil buffers(200fpm or more)

Question 21

What is a buffer

Answer 21

A device designed to stop descending car or counterweight beyond its normal limit

Question 22

Once compressed, oil buffers must decompress in ______ or must be replaced

Answer 22

90 seconds

Question 23

Buffer switch

Answer 23

-part of the safety circuit
-if switch is hit, it cuts power to the safety circuit and shuts down the car

Question 24

How are buffers installed

Answer 24

-buffers are mounted to buffer stand
-buffer stand is mounted to the pit channel
-pit channel is mounted to the guide rails