Page 8 - Elevator-series-brochure-USA

ELEVATOR SAFETY
ELEVATOR SWITCHES
Oleo elevator buffers are designed to withstand many more maximum load impacts than elevators are likely to experience in their service life. Despite this, elevator buffers remain an emergency only device. It is never a desirable outcome in the real world to have to rely on buffers to bring your elevator to a stop – that said, it is absolutely essential that you can rely on the buffers in the event that they are required.
It is for this reason that many elevator buffers are fitted with a switch. The switch is positioned to detect that the buffer is fully extended and therefore ready for impact in the case of an emergency. If for any reason the switch does not detect full buffer extension, the entire elevator system is shut down.
MODELING AND ANALYSIS
Oleo employs computer modelling and analysis to refine elevator buffers performance. Simulations are compared directly with test results obtained on Oleo’s own in-house dynamic test facility. The ability to both simulate and test, has allowed increased optimization of elevator buffer performance, providing benefits in terms of cost, safety and reliability.
Oleo provide elevator impact simulation to validate test results
BUFFER TYPE TESTING
Elevator buffers are subjected to a type test before they can be sold to the market. Type test requirements vary depending on country but most follow the guidelines of the European specification EN81.1 or ASME A17.1.
To comply with the requirements of EN81.1 the buffer must perform to the criteria detailed earlier. To establish this, the buffers are subject to drop tests. This is where a mass is dropped in freefall. The drop tests must take place at a temperature between 30 degrees F and 77 degrees F. Tests are conducted with masses at either extreme of the stated mass range of the buffer. Subsequent to the maximum mass drop, the mass must remain on the buffer for a minimum of 5 minutes, after which the buffer must fully re-extend within a time period of 90 seconds. Measurements must be made of the displacement, velocity and acceleration of the freefalling masses at a sample rate of at least 100Hz.
In order to eliminate erroneous noise and high frequency vibration from accelerometer traces, low pass filtering is usually applied to a signal sampled at a higher than required sampling frequency.
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