Traction, Emergency stop rope slide
| Author | Post |
|---|---|
| Jack S Day |
I am a private member, and I am having trouble finding something in the code. I believe there is a section somewhere that talks about allowable slip of the elevator ropes on the drive sheave but I cannot for the life of me find anything. Specifically, I have some elevators that, when an emergency stop is initiated, the ropes slide on the sheave 70”. I am trying to find where I can know if this is acceptable or not. Any way you could point me in the right direction? |
| Posted Oct 17, 2023 | |
| Matthew A Pike |
Jack, In the definitions there is Creep: creep: slight incremental, natural movement of the suspension means over their arc of contact with the driving sheave due to tractive force. The tractive force is a result of unequal tensile loads in the suspension means at points of entry and exit from the driving sheave, the tensile elasticity of the suspension member, and the frictional work occurring in the direction of the greater tension. Creep is independent of the motion status or direction of rotation of the driving sheave. NOTE: Creep exists in all traction systems and is not loss of traction, and can occur while the drive sheave is stationary or rotating. I have seen the same thing during testing. There does not seem to be a specific measurement for that loss of traction. It just seem to say in 2.24.2.3.1 that is shall be sufficient to stop and hold the car with up to 125% load for passenger elevators in the down direction. |
| Posted Oct 17, 2023 | |
| Jack S Day | 8.6.4.20.10 outlines the test in question. It will reference 2.24.2.3.1, as Mr. Pike stated, to stop and hold, but no indication of how far the ropes will slide over the drive sheave. With everything being proper, rope examination, sheave groove, equal tension, etc. The manufacturer designed the equipment to maintain a specified traction window. Has anyone seen the expectations written within the testing procedure? |
| Posted Oct 18, 2023 | |
| Matthew A Pike |
Jack, That is a great point I forgot to mention that test. There is another test where traction can become an issue. When the terminal stopping devices are tested, if the brake(s) or the braking forces imposed by the drive cause the machine to stop rotating too quickly, the ropes may slip on the sheave affecting the stop "at or near the landing (unlocking Zone)." |
| Posted Oct 18, 2023 | |
| Jason D Callaway | Mr. Pike, do you have a reference that I can look to for your most recent statement about the terminal stopping device testing. That is another time when this rope slip issue comes into play for me with a particular triplex of elevators. Thank you, |
| Posted Oct 27, 2023 | |
| Matthew A Pike |
Jason, I would use 2.25 for the "at or near the landing" requirement and 8.6.4.1 for cable maintenance needs, 8.6.4.19.5 for normal and final terminal stopping devices testing, and 8.6.4.19.12 for traction loss detection. |
| Posted Oct 30, 2023 |