Are hydraulic freight elevators completely safe?

Question

The reason I ask is because several times a day, I use a hyrdraulic freight elevator. I have always wondered, what are the chances of that single piston failing that lowers and raises the elevator? If it failed, would the car plunge to the bottom? Is there any backup mechanism if the piston suddenly lost pressure? Also, what would happen if the power went out, would it automatically descend to the first floor, or would you need to be "rescued" if the power stayed out???

Answer 1

They are very safe.  Otherwise mechanics would not stand under them with a car on top as all car lifts in mechanic shop use hydraulic elevators to raise the car.

Answer 2

Hydraulic elevators are safe, however they can fail and drop uncontrolled.  When pistons fail they tend to drift down very slowly and loose fluid such that it cannot raise back up, at that point the elevator would cease to run and would require repair.  Most hydraulic elevators have no back up safety system to prevent a free fall however more manufacturers are adding them to new installations as well as retrofitting them to older installations.  There are backup battery systems which lower the elevator and open the door in the case of a power outage, however they are most always optional.