Questions & Answers on EN 81-77:2013 N 1390 October 2014

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1 During the first months of harmonization of the standard EN 81-77, some questions have been raised to the CEN TC10 WG1 about the proper interpretation and application of certain clauses of the standard. To allow everyone to benefit from the knowledge gained from the answers to these questions, CEN TC10 WG1 decided to collect the questions and answers in this document which has to be considered as a guideline for better understanding of the questions raised on EN It is the intension of CEN TC10 WG1 that this document is freely distributed by CEN TC10 in order to give all interested parties guidance on some Frequently Asked Questions associated with the implementation of EN General Is it possible for one lift in one building to have more than one No, the acceleration design is one and has to be calculated with the hardest (Lift category) Acceleration design connected with different level of service (different and more conservative conditions (i.e. the maximum height of the building travel)? served and the maximum travel of the lift). General (Scope) Is EN also applicable for lifts which are used temporarily during erection of the building? I don t mean construction hoists. What I No, because these temporary lifts are installed in not complete buildings not in compliance to EN 1998 mean are such lifts which are used during construction as goods passenger lift and which are slightly modified after finalization of the building and then used as normal passenger lifts. In specific cases such lifts could also have increasing number of floor and a machine room which is moved up with the growing building, sometimes called jump lift Does the retainer allowed to be fixed no more than 15 each direction from the points where the ropes enter and leave the grooves? If yes, does it make disadvantageous influence of the function of the retainer? No, the devices for preventing the ropes from leaving the grooves of traction sheaves and pulleys shall include one retainer no more than 15 from the points where the ropes enter and leave the grooves in the direction of the wrap. 1 / 8

2 5.9 Overturning and displacement as a result of the forces imposed on them including forces generated by the design acceleration. Q1: Do we have to consider slack rope on the traction sheave so that the lift machine is not tensioned by the ropes? Q2: Do we have to consider dynamic effects due to the design acceleration which may create larger amplitudes due to resonance? If yes, which frequencies should be considered? 5.9 Internal components of controls Due to the design acceleration internal components of controls may get loose which may lead to a break down. Do we have to consider such failures which are not directly addressed in the standard? For info, A17 states: Machinery and Sheave Beams, Supports, and Foundations Beams and Supports. Overhead beams and supports including hitch-plate blocking beams shall be anchored to prevent overturning and displacement as a result of a seismic force acting in a horizontal direction A1: Calculations shall be done in favour of safety, so tension on ropes shall not be considered A2: Dynamic effects shall not be considered: also in EN , calculations for "Non-structural elements" are made without take into account dynamic effects. We have not directly covered this type of failures because statistical data we have consulted do not show particular problems about this issue, the major problem we have seen is the overturning of the control cabinet. Considering that control cabinet shall be designed and anchored to prevent overturning and displacement due to the design acceleration, the probability that internal components of controls get loose can be considered sufficient low and corrective actions can be neglected. 2 / 8

3 5.9 Possible suppliers of seismic detection systems told us that the triggering level for the primary wave detection is too low and not feasible. Any shaking in the building due to other reasons (e.g. metro passing by) would initiate the system. This value was introduced taking into account the document coming from Japan describing P wave sensor in the Jea Guide [10 GAL = 0,1 m/s2] The value introduced in the standard is in line with the sensors available on the market. This value may be updated at the next revision of the standard. [collect other official information from the suppliers] Q1: Furthermore they didn t understand how the functional and interface test according to should be done. A1: All these electronic devices shall have self-testing functions which result in a shout down of the seismic switch and the shout down of the seismic switch shall put the lift into the seismic mode. Q2: Could you please let me know if these requirements have been discussed with suppliers of seismic detection systems? A2: Our driving documents for this value were: Suppl. A ; Suppl. B and Japan guide (see P-wave sensor) It is possible to evaluate to modify this value in the next revision of the standard 5.9 In case of cantilever car slings (rucksack slings) due to the eccentric centre of gravity of masses of the car and load (see sketch below) additional forces will be applied on the guide rails which seem not to be taken into consideration in the formula in Annex D.8. This will create higher stresses but especially movements of the car which could lead to collisions. Did WT5 by purpose not consider such arrangements? Annex D in EN is informative and gives example of calculation taking into account only G.7.2 Centrally guided and suspended car of the EN 81-1/2; if there is a cantilever car slings is necessary to take into account horizontal acceleration for the formulas of G.7.3 Eccentrically guided and suspended car of EN 81-1/2 in the same way as above. It is possible evaluate to add also this example in the next revision of the standard 3 / 8

4 In seismic risk zone 2 and greater, failure of mains power supply (5.10.2) requires to move the car to the next landing in up or down direction. In seismic risk zone 2 we don't have a seismic switch. This means we cannot distinguish between an ordinary power cut off and a power cut off due to seismic activity. In seismic risk zone 3 we have a seismic switch. The signal of the seismic switch requires us to move away from the counterweight (5.10.4). Is it correct that after failure of the mains power supply, the car can be moved in emergency power in any direction with any speed as long as we don't have a seismic signal from the seismic detection system? Is it correct that after failure of the mains power supply, the car can be moved in emergency power in any direction with any speed? Yes; to understand better this point, delete the words In case of seismic events at the beginning of point Behaviour of the lift in case of failure of the mains power supply - at the next revision of the standard. 1) if there is no activation of the seismic switch, after failure of the mains power supply, the behaviour of the lift has to comply (so ever for lifts in seismic category 2 for those is not required the seismic switch): the car can be moved in emergency power in any direction with any speed; 2) if there is activation the seismic switch, after failure of the mains power supply the behaviour of the lift has to comply : the car shall reduce the speed or stop and proceed to the next possible landing away from the counterweight or balancing weight with maximum 0,3 m/s car speed 4 / 8

5 says The seismic detection function, including interface between seismic detector system and lift controller, shall be tested every 24 h. If a failure is detected during the test or the interface between the seismic detection system and the lift controller is interrupted, the lift shall remove itself from normal operation on its next stop at a landing and park with its doors open. Q1: If the interface is interrupted and it is just not during the test, shall the lift switch into seismic mode (see ) or into failure mode (see )? Q2: Does the interface that need automatic system test every 24 h refer to the interface that sends seismic signal and makes the lift switch into seismic mode(see ), or the interface that sends failure signal and makes the lift switch into failure mode (see )? The lift shall reduce the speed to 0,30 m/s or stop and proceed at this reduced speed to the next landing. Q1: Is it acceptable if the next landing is close to continue for some time with full speed and than approach this landing with normal deceleration instead of reaching the landing with immediately reduced speed much later? Would a delay for speed reduction of 3 s be acceptable according to reaction time specified in ? A1: As is written in point , if the interface is interrupted and it is just not during the test, the lift shall remove itself from normal operation on its next stop at a landing and park with its doors open. A2: The interface that need automatic system test every 24 h refers to the interface that sends seismic signal and makes the lift switch into seismic mode A1: describes the System reaction time. The system reaction time describes the maximum allowed time period between the point in time when the seismic wave exceeds the selected seismic trigger level for the first time and the point in time when the lift switches into the seismic mode described in The system reaction time shall not exceed 3 s. So, is possible to have 3 s of delay from the point in time when the seismic wave exceeds the selected seismic trigger level for the first time and the point in time when the lift will reduce the speed to 0,30 m/s. 5 / 8

6 (continued) Table B.1 Annex B.1 & EN Q2: Is it acceptable for reducing the speed to initiate an emergency stop? Some controls are not designed for a controlled speed reduction. Q3: In case of lifts with an express zone travelling with reduced speed of 0,3 m/s could take a very long time until a next landing is reached. Is this requirement also applicable to such lifts or would it be better to continue for some time in full speed? For Ta in table B.1, Maximum among fundamental periods of vibration of the parts of the lift is difficult to be understood. Does it mean the maximum fundamental periods of vibration of the parts of the lift? The formulae for calculation of the design acceleration in EN as well as EN , include the importance factor of the lift γ a. EN includes an additional importance factor for the building γ 1 (see 2.1 ) which may be considered by national authorities in case of specific buildings which should be designed with higher resistance to earthquakes. According to clause the reference peak ground acceleration a gr has to be multiplied with this importance factor for calculation of the design ground acceleration a g (a g = γ 1 a gr ). This approach has been implemented in Germany and may be in other countries which leads to the situation that for a safety related lift (e.g. firefighting lift) in a building with an increased importance factor (e.g. A2: Yes. After the car is stopped it has to proceed to the next possible landing away from the counterweight or balancing weight with maximum 0,3 m/s car speed A3: This situation was not taken into account by the standard. Due to the fact that in the standard there aren t controls of the guides and ropes, the WT5 considered that the risk to the achievement of the nearest floor was acceptable only moving the car at low speed. As defined, Ta is the fundamental vibration period, expressed in seconds, of the non-structural element (Ta = 0 if the lift does not affect the fundamental vibration period of the building. In other cases this value shall be increased according to calculation. 6 / 8

7 Annex B.1 & EN (continued) hospital) both importance factors may need to be considered. The consequence is that a higher design acceleration and in some cases a higher seismic lift category is applicable as if only one of these importance factors would have to be considered. Q1: Is it the intention of EN to consider both important factors or would it be sufficient just to consider one? A1: EN considers both: γa (directly in the formula in EN 81-77) and γ I (indirectly, in the formula of α; α is the ratio of the design ground acceleration on type A ground, ag, to the acceleration of gravity g (α = a g /g is non dimensional). a g is equal to agr times the importance factor γ I (a g =γ I.a gr ) (EN , point (3)). In the Introduction of EN is clearly descript that It is assumed that negotiations have been made for each contract between the customer and the supplier/installer about the design acceleration (a d ) to be considered The building designer or the lift owner should provide the design acceleration (a d.) which will be documented in the information for the owner provided by the installer. Q2: In case of only one importance factor need to be considered which one has to be taken? Q3: For which kind of lifts should γ a be considered (all lifts in a hospital of only those with a safety related operation, e.g. fire fighting lifts)? A2: Not applicable A3: See the definition of γ a in EN 1998 where is written: Importance factors (1) P For the following non-structural elements the importance factor γa shall not be less than 1,5: - anchorage elements of machinery and equipment required for life safety 7 / 8

8 Annex B.1 & EN (continued) systems; - tanks and vessels containing toxic or explosive substances considered to be hazardous to the safety of the general public. (2) In all other cases the importance factor γa of non-structural elements may be assumed to be γa = 1,0. EN has not defined which kind of lifts have to be considered as life safety systems : it depends from National Regulations. Where National Regulations are not provided, should be considered as safety related lifts for example those for firefighters, those used for evacuation of people and those installed in hospitals or other buildings defined for use in emergency circumstances. Q4: Which value should be taken for γ a in case of safety related lifts? EN doesn t specify a value for such lifts and just mentions a minimum value of 1,5 for other safety related applications? A4: EN doesn t define which value has to be considered for γ a in case of safety related lifts. We think that is not our task but it may be taken into account in the next revision of the standard, if necessary. Annex D.2 What is the load distribution of Q SE? Is it on ¾ of the car area as in load case for normal operation or is it evenly distributed? It is evenly distributed according with the fact that for the rated load is evenly distributed. Annex D.7 In addition the question on the height of the centre of gravity of passengers and loads has not been finally answered at the last WG1 meeting. Is there any new conclusion of WT5? The position of gravity centre was a point still open last year. At the beginning we proposed 1,1 m but taking into account anthropometrical information we can reduce it and assume 0,80 m. 8 / 8