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Post by superteacher on May 31, 2018 7:43:17 GMT
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Post by trt on May 31, 2018 13:32:43 GMT
Single width escalators, isn't it? I wonder if escalators wear out quicker if they are predominantly fully loaded, half-loaded or unloaded?
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Chris M
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Post by Chris M on May 31, 2018 14:09:23 GMT
I wonder if escalators wear out quicker if they are predominantly fully loaded, half-loaded or unloaded? I've just spend a good half hour googling this question, and I've not found a definitive answer, but escalators that are built to carry more people and/or heavier loads are sturdier than those designed for lighter duties, and the trial to use cheaper, lighter escalators at Bank DLR was not a success (they had to be replaced after a significantly shorter service life than the Underground standard ones). Together these suggest that an fully loaded escalator would wear out quicker than an unloaded one. Where half-loading comes in to this I don't know. I found much uninformed speculation that escalators where people stand on one side only would wear out quicker (due to uneven wear) than ones where people stand on both, that people walking on escalators cause more wear than people standing on them, and that down escalators last longer than up escalators, but no confirmation of any of these from people who actually know what they are talking about. I did find that in 2008 Tube Lines started (or were planning to start?) a trial to get more information about how escalators wear, but the details were paywalled and I haven't managed to find any followup articles. |
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Post by trt on May 31, 2018 14:35:22 GMT
I do know that they reverse escalator direction, frequently at weekends, in order to balance out wear, but it's a fascinating topic for a considerably costly asset.
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class411
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Post by class411 on May 31, 2018 16:16:55 GMT
I wonder if escalators wear out quicker if they are predominantly fully loaded, half-loaded or unloaded? I've just spend a good half hour googling this question, and I've not found a definitive answer, but escalators that are built to carry more people and/or heavier loads are sturdier than those designed for lighter duties, and the trial to use cheaper, lighter escalators at Bank DLR was not a success (they had to be replaced after a significantly shorter service life than the Underground standard ones). Together these suggest that an fully loaded escalator would wear out quicker than an unloaded one. Where half-loading comes in to this I don't know. I found much uninformed speculation that escalators where people stand on one side only would wear out quicker (due to uneven wear) than ones where people stand on both, that people walking on escalators cause more wear than people standing on them, and that down escalators last longer than up escalators, but no confirmation of any of these f rom people who actually know what they are talking about. This is the thing. When I saw the question I speculated a lot but as I don't know for certain, and as some of these questions have counter-intuitive answers I refrained from posting. However, I think there are some things you can say that might help people form their own opinions: 1) Unless the mechanism is entirely frictionless (which it isn't), a more heavily loaded escalator will wear faster than a less heavily loaded one. So fully loaded will wear fastest, unloaded slowest, and half loaded somewhere in the middle. As far as I'm aware the relationship of force to wear by friction is linear, but I wouldn't bet money on it! 2) Unless the supporting mechanism involves a cantilever (which would be absurd unless you were going for some high art installation that would be wildly inappropriate in an underground station) the total wear will not be greater because of people standing (predominantly) on one side. However, the wear will be uneven, so the time between the whole thing having to be taken apart would be less, and as this is likely to be costlier than the worn parts, it should be a consideration, which makes reversing the escalator from time to time an attractive proposition if it is practical, taking into account other factors of passenger flow. 3) Up escalators will wear very slightly faster because they have to accelerate each person using them to the vertical speed of the unit. It's as if each person weighed a bit more for a second or two. However, the difference will be small compared to the overall wear. (Similarly, on a down escalator, each person will effectively weigh a little less as gravity will do the job of accelerating them to the downward speed of the unit. 4) People walking on the escalator is a very tricky one as their weight will momentarily increase each time the push down to step (obviously more so if they are going up), but they will be on the unit for a shorter period of time. As I said, these are just factors to consider - although I'm pretty confident that (1) is rock solid. For (2) to (4) all sorts of complexities could yield a counter intuitive result. |
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class411
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Post by class411 on May 31, 2018 16:18:42 GMT
I do know that they reverse escalator direction, frequently at weekends, in order to balance out wear, . It's not going to be very effective if you compare five heavily loaded days with two lightly loaded ones, but as Tesco tell us: Every little bit helps. |
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North End
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Post by North End on May 31, 2018 16:43:39 GMT
I do know that they reverse escalator direction, frequently at weekends, in order to balance out wear, but it's a fascinating topic for a considerably costly asset. Not so sure about reversing (some escalators have restrictions placed on their use mandating they can only be used in one direction), however it’s common for escalators to be “rested” on a rotating basis when not all are required to be in use. Not sure if it’s mandated anywhere, but it seems some supervisors are keener to do this than others. |
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Post by MoreToJack on May 31, 2018 17:55:03 GMT
I do know that they reverse escalator direction, frequently at weekends, in order to balance out wear, but it's a fascinating topic for a considerably costly asset. Not so sure about reversing (some escalators have restrictions placed on their use mandating they can only be used in one direction), however it’s common for escalators to be “rested” on a rotating basis when not all are required to be in use. Not sure if it’s mandated anywhere, but it seems some supervisors are keener to do this than others. Indeed. It rarely happens in traffic hours as most stations are 'set up' to operate either right-handed or left-handed (in terms of signage) and reversing escalators on a whim can cause major crowd congestion issues. It should happen overnight whilst the station is closed, as it means that the escalators don't 'wear' in the same pattern all the time and retain the ability to run both ways. A lot of those with the one way restriction are because of a lack of regular reversals. |
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North End
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Post by North End on May 31, 2018 18:30:54 GMT
Not so sure about reversing (some escalators have restrictions placed on their use mandating they can only be used in one direction), however it’s common for escalators to be “rested” on a rotating basis when not all are required to be in use. Not sure if it’s mandated anywhere, but it seems some supervisors are keener to do this than others. Indeed. It rarely happens in traffic hours as most stations are 'set up' to operate either right-handed or left-handed (in terms of signage) and reversing escalators on a whim can cause major crowd congestion issues. It should happen overnight whilst the station is closed, as it means that the escalators don't 'wear' in the same pattern all the time and retain the ability to run both ways. A lot of those with the one way restriction are because of a lack of regular reversals. From my experience, some (by no means) all Supervisors are terrified of even stopping an escalator, let alone reversing one! |
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class411
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Post by class411 on May 31, 2018 18:41:25 GMT
It should happen overnight whilst the station is closed, as it means that the escalators don't 'wear' in the same pattern all the time and retain the ability to run both ways. A lot of those with the one way restriction are because of a lack of regular reversals. There may be some point in doing it from the point of view of maintaining an ability to run in both directions (although that sounds slightly unlikely, and if it was necessary at all it would surely only be necessary for a couple of minutes at a time.) However, that method would do virtually nothing to balance wear, because the reason to reverse escalators for wear balancing is to cause people standing on the right to be standing on the other side from when it is in normal operation. Clearly this will not happen when the station is unoccupied. Similarly there is not a great deal of point in doing it when the station is very lightly loaded - unless, perhaps, you could have, say, one direction for four hours a day when the load is heavy and the other direction for the rest of the day when the load is lighter but still significant. |
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Post by MoreToJack on May 31, 2018 19:15:59 GMT
Indeed. It rarely happens in traffic hours as most stations are 'set up' to operate either right-handed or left-handed (in terms of signage) and reversing escalators on a whim can cause major crowd congestion issues. It should happen overnight whilst the station is closed, as it means that the escalators don't 'wear' in the same pattern all the time and retain the ability to run both ways. A lot of those with the one way restriction are because of a lack of regular reversals. From my experience, some (by no means) all Supervisors are terrified of even stopping an escalator, let alone reversing one! +1! It should happen overnight whilst the station is closed, as it means that the escalators don't 'wear' in the same pattern all the time and retain the ability to run both ways. A lot of those with the one way restriction are because of a lack of regular reversals. There may be some point in doing it from the point of view of maintaining an ability to run in both directions (although that sounds slightly unlikely, and if it was necessary at all it would surely only be necessary for a couple of minutes at a time.) However, that method would do virtually nothing to balance wear, because the reason to reverse escalators for wear balancing is to cause people standing on the right to be standing on the other side from when it is in normal operation. Clearly this will not happen when the station is unoccupied. Similarly there is not a great deal of point in doing it when the station is very lightly loaded - unless, perhaps, you could have, say, one direction for four hours a day when the load is heavy and the other direction for the rest of the day when the load is lighter but still significant. Maybe not the wear being spoken about here, but running things continuously in one direction will create wear and cause problems when something is then run in the opposite direction. There are plenty of case studies here of uni-directional rail systems, for example. Escalators have failed catastrophically after being started in the 'wrong' direction. Running a reversible escalator in the opposite direction to usual does happen regularly under failure conditions. If an 'up' escalator has failed then the 'down' escalator will sometimes be commandeered to ensure that the station can remain open. Similarly, a higher passenger flow than usual could require additional escalators in a particular direction to alleviate overcrowding and, again, keep the station open. We had more than a few creative solutions during my time at King's Cross. |
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