April 01, 1998
by Teresa Acklin
Safety monitors for elevators
In 1981, Agromatic A.G., Laupen, Switzerland, introduced the first safety monitoring units for elevators of the series ALS600 up to ALS1300. According to the rising demands upon safety, a totally new series with the name ALS197 was developed.
These units mainly consist of the following three components: the electronic unit ALS197, alignment sensors and rotary speed sensors.
The electronic unit ALS197, driven by a microcontroller, is very easily mounted and very easily set to operation. These units are deliberately developed and manufactured for practical operation and especially for the application of safety monitoring of elevators. Up to five different sensors can be connected to the electronic unit. It can be used as a:
single rotary speed monitor
single motion detector
difference rotary speed monitor
single alignment monitor
combined unit rotary speed/alignment monitor or
combined unit 2x alignment (on the top and at the bottom) plus rotary speed monitor.
There is a choice of different sensors. The optomagnetically operating sensor ALS2000, with no mechanical wearing parts like contacts, springs, etc., for alignment monitoring can be used for single elevators as well as for double- or triple-elevators. The fiberglass rod reaching into zone 20 (into the elevator casing) is equipped with a crack safety device. It is held in its position by permanent magnets to avoid possible wear of the sensor by mechanical wear of springs, tensioning rings, etc.
If the sensor rod is pushed aside by the off-track running elevator belt, the according distance is optically measured in the sensor and transmitted as a positively switching signal for evaluation. The sensors operate with a voltage of 10-55V and are supplied with a positively switching signal output (PNP/NC) with a maximum power load of 200mA. They correspond with IP65 and are tested and certified for zone 10 (20).
These sensors can be easily mounted on the left and the right side of the elevator belt by two M4-screws. Because of the sensor's slotted holes, it can be moved sideways with no difficulty.
Alternatively, for alignment monitoring, the inductive sensors of the series ASIQ80 are available. Those sensors are supplied with a setting of sensibility for setting the switching distance between 10 millimeters and 60 mm.
The inductive sensors are mounted outside of the elevator casing by a separation glass made of Plexiglas. But they can only be used for elevators with metallic buckets in contrast to the above described sensor ALS2000, which can be used for all kinds of elevators or chain conveyors.
For monitoring the rotary speed, the sensors ASI12 with a switching distance of 4 mm or the sensors ASI30 with a switching distance of 15 mm are available.
Both sensors operate within a voltage range of 10-55V. Sensing the rotary speed is preferably done via a keynut mounted in the shaft, a drilled recess with the sensor's diameter plus 2 mm or a projecting screw head.
Contributed by suppliers, technical profiles feature new technology, products, specific applications or proprietary concepts. This material was prepared by Buhler A.G., Uzwil, Switzerland.Safety Monitoring for Elevators.
Example A: Difference rotary speed monitoring (slippage detection).
For elevators not operating in dust-explosion endangered zones like gravel plants, etc., it is often sufficient to just detect a possible overload in time. Additionally, the difference rotary speed can be monitored.
The unit ALS197 can be easily adjusted after its mounting. The elevator is set to operation, and as soon as its rated rotary speed is reached, the “speed adjust” key is pressed and the effective rotary speed is automatically registered and stored by the unit.
With the “speed tolerance” key, the allowed tolerance or the slippage of sensor 1 (nadir shaft) can be set. The unit additionally allows delaying the alarm caused by the slippage. This option can be necessary in case the elevator is exposed to various demands such as being directly fed by a dump weigher.
Example B: Combined rotary speed/alignment monitoring.
Two inductive sensors of the series ASIQ80 or two optomagnetical sensors of the series ALS2000 are connected as alignment sensors to the evaluation unit plus one additional rotary speed sensor of the nadir shaft.
Also in this version, adjusting the unit is most simple. The monitoring of the rotary speed is set in the same way as described in the above example.
An additional alarm delay is available for the alignment monitoring in order to suppress short-term deviations of the elevator belt. The units are supplied with a mass-produced run-up delay of 15 seconds. Only after this time is the unit switched to “active.”
The alarms for rotary speed and alignment can be given separately or in parallel. An additional data interface RS485 is available for the units to enable a transfer of data to an S.P.S. or a P.C. For elevators with an inclining height of 25 meters and higher, a double alignment plus rotary speed version of the unit is available.
Adjusting and setting to operation are effected in the same way as described in the above example. Also, with this configuration of units, both kinds of alignment sensors can be used.
The microcontroller-driven monitoring electronics built into the unit ALS197 are developed for permanent supervision of all connected sensors and their supplies. Eventual cracks or damage of a cable done by mice are detected and trigger the alarm accordingly.
Contributed by suppliers, technical profiles feature new technology, products, specific applications or proprietary concepts. This material was prepared by Agromatic A.G., Laupen, Switzerland.