Why elevators break

Almost all pulley elevators have multiple cables -- between four and eight total. Even if one cable snapped, the remaining cables would hold the elevator car up. In fact, just one cable is usually enough. But let's say all the cables did snap. Then the elevator's safeties would kick in.

Safeties are braking systems on the elevator car that grab onto the rails running up and down the elevator shaft. Some safeties clamp the rails, while others drive a wedge into notches in the rails.

Typically, safeties are activated by a mechanical speed governor. The governor is a pulley that rotates when the elevator moves. When the governor spins too fast, the centrifugal force activates the braking system. If the safeties failed, you would be plummeting rapidly, but you wouldn't quite be in a free fall.

Friction from the rails along the shaft and pressure from the air underneath the car would slow the car down considerably you would feel lighter than normal though. On impact, the car would stop and you would keep going, slamming you into the floor.

But two things would cushion the blow. First, the elevator car would compress the air at the bottom of the shaft as it fell, just as a piston compresses air in a bicycle pump.

The air pressure would slow the elevator car down. Second, most cable elevators have a built-in shock absorber at the bottom of the shaft — typically a piston in an oil-filled cylinder. That would cushion the impact too. With all these features in place, you would have an excellent chance of surviving any elevator mishap. In the case of the Chicago elevator incident, once the firefighters figured out where the passengers were, the crew put up struts to make sure the elevator did not drop any further.

Then they broke a wall, forced the elevator door open and put a ladder into the elevator to help people up and out. We don't come down like Batman so we must go through the wall. Elevators and escalators in an office building run about 10 hours per day. In offices with 5 working days per week, elevators operate about working days per year, or hours per year. If you use an elevator 8 times per day in your office and you work days per year, you will take trips per year.

If an installed lift experiences an average of 0. If you travel times up and down to your office in a year, your chance of getting trapped in an elevator is thus 0. Although the probability of personally being a trapped in a lift car is very low, most do however know someone who has been in an elevator mantrap. The elevator car is a small claustrophobic and confined space, where one is cut off from the rest of the world. The sudden unexpected stop or jerk, often associated with a breakdown, makes the experience even more unpleasant — especially when the elevator is traveling in up-direction.

Many equipment failures can be prevented with proper inspection and preventative maintenance. Long wait times and frequent breakdowns are inconvenient and a sign of wear. Overheating, high energy use, and low power factor may not be obvious problems, but they incur hidden costs. Implementing simple elevator motor maintenance practices can help decrease expenses and downtime.

Below, we examined some of the most common elevator problems and provided solutions to preventing elevator downtime:. Worn sheaves place extra wear on ropes, which in turn increases the level of wear on sheaves. This creates a cycle of destruction for both key components.

Sheaves can be regrooved or replaced to prevent premature hoist rope failure, so be sure to check groove profiles to verify the fit between the ropes and the sheave. Simple tools are available with magnetic standards and a straight edge to visually check if the grooves on the sheave a wearing evenly. Elevators with any history of motor failures or operation issues should undergo a power quality survey.

Infrared thermography measures drastic temperature changes and can identify possible trouble spots before they cause costly system failures. When wear occurs, small metal particles are released in the oil and can interfere with the proper functioning of an elevator system. Similarly, improper lubrication or worn seals can cause contamination.