Hydraulic elevator failuregreenspun.com : LUSENET : Elevator Problem Discussion : One Thread
I recently replaced an elevator in a job that had a rather eyeopening failure and want to know if this has occured elsewhere. This happened on a five stop in-ground hydraulic. The power went off in the building and the elevator seeped down and rested on the buffers, the packing relaxed and the oil siphoned into the pit. When the power came back on the elevator attempted to go to the fourth floor. It made it to within a few feet of it's destination (on air) before the pump seized and tripped the overload. The mechanic reset the overload, the car started down with the cylinder full of only air. The air came out so fast the lid blew off the tank and the car CRASHED into the pit. If it had made it to the floor and a person pushed a down call they probably would have been seriosly injured. It is not known if the low oil timer failed or if the car made it to each floor in time. Has anyone seen or heard of similar failures ?
-- Jerry Rexer (firstname.lastname@example.org), April 12, 1999
It seems unlikely that the elevator ascended on air. The basic idea of the low oil timer is that the car will stall if it runs out of oil and damage the pump, motor,etc. Why would a seal that didn't hold oil hold air?
I'm not saying anyone is lying; I'm sure the story is the true perception, but from a scientific standpoint, doesn't make sense. The pumps used on elevators, to the best of my knowledge won't pump air. They are designed for a much more viscous substance.
-- John Brannon (email@example.com), April 12, 1999.
Your response is the one I would have given a year ago. One of the explainations I have for this is that the tank must not have been totally dry. The unit was a v-belt drive type. There must have been enough oil in the tank to pressurize the packing and just enough to lubricate the pump. With the tank just above the pump, a small trickle would have kept it going.
-- Jerry Rexer (firstname.lastname@example.org), April 13, 1999.
I will accept the car siphoning oil out on the buffers this is not uncommon some do it. now how do you fill a cylinder with air and keep it just shy of a floor with a 2 inch opening and a rotary or screw pump? take some air pressure to keep it there wouldnt it. after all there is a 2000 pound car up there,and the tolerances on a oil pump are not designed to pump air.im not sayin the pump didnt lock up some old cars never had low oil timers or this didnt happen but the physics of it seem a lil exagerated..
-- jag (email@example.com), April 14, 1999.
I have to agree with John Brannon, IMO pumps (or any other kind of oil impeller pump) typically cannot pressurize less viscous fluids than oil, however I have heard of a similar problem that occurred in Chicago. The car actually was caught in the hatch stuck in the rails and on the callback the mechanic jumped into the car and unknown to him, the packing had relaxed and the tank drained and the car fell about three floors. The mechanics name is Ken Garst, he sufferred tremendous damage to bones from the waist down, broken ankles, pelvis and years of Physical Therapy...
As a plug for a product, the LifeJacket would have prevented the accident you describe here. The car would not have been damaged nor would anyone potentially riding have been injured.
-- John Koshak (John_Koshak@AdamsElevator.com), June 03, 1999.