Terminal Limits
| Author | Post |
|---|---|
| Matthew A Pike |
What is meant by "at or near the top and bottom terminal landing" in rule 2.902a 1955 or the more recent 2.25.2.1.1? In 1937 the distance was given as "within the top clearance and the bottom overtravel" which suggests that in reaction to the device the car or counter weight can fully compress the buffer. In newer codes (1955 to today) it is "at or near the terminal landing." With today's newer control systems, it seems to me that there is a progression of safety devices to stop the car "at or near the landing" should there be a failure of the preceding device. The normal stopping means brings the car to a stop within 1/2 inch of the landing. If that means fails, the Normal Terminal stopping device will then bring the car to stop at or near the terminal landing. Many of these devices utilize two levels of detection. On the first level, they insert dynamic braking into the motor to slow the car more rapidly than normal and usually the normal leveling device is allowed to take over and bring the car to rest at the landing. On the second level of detection, the device removes power from the driving motor and brake causing what I call an "emergency stop," code uses dynamic braking test. Does this stop need to bring the car to rest before the final? Does this stop need to be within the leveling zone? Does this stop need to be within the door zone? Does this stop need to be within the unlocking zone? Is it OK for this stop to fully compress the buffer? Can you see my dilemma? The Emergency Terminal Limit Switch (ETS) will remove power from the motor and brake. Where should a successful stop bring the car to rest? (Same questions as NTS). Without a definition of "at or near the terminal landing" I can't tell what is acceptable during a test. Some manufacturers will tell you where the acceptable stop is, but most do not. Can I get some help from you? What do you think "at or near the terminal landing" means? Inquiring minds want to know. |
| Posted Jan 25, 2023 | Last updated Feb 5, 2023 |