Experience with SIL3 safe shaft copying system
What are the advantages of using the SIL3 SAFE shaft copying system and David D613 lift controller? Practical experiences.
KW-Aufzugstechnik GmbH has been supplying its David D613 controllers as standard with a SIL3 safe ANTS safe shaft copying system from Variotech and the LIMAX 33CP from ELGO since the middle of last year. What advantages do the latest versions of the proven shaft copying systems now provide in assembly, start-up and maintenance?
The systems of both manufacturers are distinguished by their compactness and easy mounting in the shaft. Both systems meet the requirements for high-rise lifts in terms of conveyance height and nominal speed.
What is a SIL3 safe shaft copying system?
Using a SIL3 safe shaft copying system is an adjustment both for fitters as well as for testing institutes: unlike conventional shaft copying, no shaft switches of any kind are needed in a SIL3 safe shaft copying system. Neither emergency limit switches, nor pre-limit switches nor zone switches.
All of this information is generated via redundant absolute value information. SIL3 certification of the safe shaft copying system ensures that any failure in the absolute shaft position always results in a safe condition of the lift (normally through opening of the safety circuit).
The system consists of a reading head, an evaluation circuit, a steel or magnetic strip and an attachment set. The limit switch positions and landing positions must be learnt during the start-up of the lift by prescribed learning sequences in the safe shaft copying system.
After this, the SIL3 safe shaft copying system is capable of carrying out various safety-relevant monitoring activities.
► Monitoring limit switch positions
► Monitoring door zone areas incl. door bridging, for any premature door opening, repetition and fast start
► Monitoring the nominal speed
► Monitoring the inspection speed during inspection mode
► UCM monitoring during door bridging in the door zone area
► Deceleration control in fast lifts with shortened lift head/lift pit
► Safety area monitoring during inspection mode in lifts with shortened shaft head/shaft pit.
How does the start-up work?
To permit all these functions, highly complex communication between the SIL3 safe shaft copying and David D613 controller is needed on the basis of the CANopen lift standard protocol. To achieve convenient start-up by the user without special knowledge,
KW-Aufzugstechnik implemented step-by-step user-guided parameter assignment in the D613 controller. This guarantees that start-up of SIL3 safe shaft copying is possible for everyone in next to no time.
Three steps are needed for this:
1. Basic configuration of the SIL3 safe shaft copying (e.g. definition of the door zone length), determination of monitoring functions (e.g. lift speed, monitoring functions such as delay control in the case of shortened shaft end, etc.).
After this, both limit switch positions in the shaft head and shaft pit must be travelled to and programmed with parameters.
2. After learning both the limit switches, the relays of SIL3 safe shaft copying integrated in the safety circuit are closed if the car is within both positions in the shaft. The landing positions now have to be learnt in the lift controller, irrespective of the SIL3 safe shaft copying system.
This can either occur in advance via synchronisation at the lowest level of a flush-level table or optionally by manually travelling to each floor and programming by the push of a button. After this, normal trips can already be made subject to the restriction that no door bridging is yet possible. After adjusting the flush levels of all floors, comes the final step:
3. Now the learning sequence for fixed learning of the floors/flush levels in the SIL3 safe shaft copying systems is launched. For this purpose, the controller travels to all of the floors several times as part of an automatic learning sequence. After this learning sequence has been completed, the lift is fully operational. Since the SIL3 safe shaft copying system now knows all of the floors, the zone areas can also be emulated and door bridging activated on request of the lift controller.
All of the safety-relevant functions can only be activated once all of the necessary conditions have been met. For example, a lift controller command via the CANopen lift protocol to the SIL3 safe shaft copying to activate the door bridging would only be carried out if the car were within the zone area and the travel speed below the limits required for this.
What does experience show since the first use and acceptances of the authorised inspection bodies?
After KW-Aufzugstechnik had delivered the first controllers to all kinds of customers in the middle of last year, it emerged that all customers were able to carry out the start-ups on their own, in the beginning in part with telephone support. The gains in assembly time, especially in the case of time-critical modernisations, were outstanding. Expensive mechanical assembly work was unnecessary. The time advantage doubled in the case of lifts with reduced shaft heads and/or shaft pits.
The first inspections by the licensed inspection bodes were as a rule also unproblematic. Isolated difficulties that initially occurred during the acceptance (where are the zone magnets / safety circuits?) have now been clarified. The increased safety level is of course an advantage for the licensed inspection bodies. Sub-optimal assembly work does not result in the lift under construction not being completed, the room for manipulation has been restricted.
As the controller builder, KW-Aufzugstechnik naturally includes and provides as part of delivery the certificates and inspection instructions of the safe shaft copying systems supplied.
Use of a safe shaft copying system has clear advantages in assembly and start-up by saving time compared to conventional systems. During maintenance, this will pay off through the reduced storage of spare parts and the reduced need for components for these lifts in the future.
Design advantages also arise due to the absence of shaft switches, especially in lifts with visible (glass) shafts in aesthetic terms.
During preventive maintenance as part of Industry 4.0, SIL3 shaft copying systems have the advantage that they generate both status and wear data as well as error messages, which can be retrieved and transmitted. Intelligent systems report information, which permits variable maintenance deployments to guarantee a fair cost structure for the operator of lifts.