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Five common problems with lifts (and how to fix them) by Tek Hussein, Head of Technical at WeMaintain However well-designed, however well-maintained, lifts can—and do—go wrong. But when a lift does go wrong, it is almost always for the same reason: someone is misusing it. Maybe there are more people in the lift than there should be. Maybe someone is trying to squeeze a sofa inside it to avoid carrying it down five flights of stairs. Whatever it is that causes the break down, you can confidently predict it involves a person using the lift in a way that it wasn’t really designed for. Even when a lift malfunctions for a reason that has nothing to do with misuse, it usually involves human interaction. The doors, because they are the parts of the lift with which people interact the most, contain a number of safety devices that trip out easily. This means that 70 percent of all faults with lifts relate to the doors. Problem: There are position faults. In order for a lift to work correctly, its components, including its magnets and proximities, need to be aligned perfectly. If they are not aligned, breakdowns happen, and over time, these components tend to loosen or become dislodged in another way. Pencil switches and magnets, for example, have a set-up tolerance of between 8 and 12mm. If the gap is any wider or narrower, there are problems with the magnetic field, such as double pulsing or no pulsing at all. Problem: The landing’s door locks fail to align with the lift as it reaches the floor. The solution to this is simple: check all the locks and make sure everything aligns. Lift 4
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doors have so many moving parts that any number of things can go wrong. These parts are necessary, because they make sure the door runs seamlessly and closest with a minimum of noise and space between one another. But pick up, hanging or kicking rollers can all go wrong, and this means a breakdown. Problem: There are problems with the drive. Drive problems tend to come about with age. As lifts get older, the equipment deteriorates and discrepancies appear. The brakes wear down and the motor contacts become high resistance. The motor fields get weaker, and there’s a loss of traction, often due to a wearing down of the ropes or sheaves. Agerelated deterioration is hard to avoid, but it can be hastened if maintenance teams do not keep the load weighingdevice calibrated or if they do not fill up the oil pots that lubricate the guides. Problem: The safety circuit switch feathers. When a lift recognises that something is off, and any users are potentially at risk, it stops. This is because of the safety circuit. It’s therefore a very important part of the lift installation, and those maintaining the lift must make sure that everything is as it
should be. Certain parts of the lift—the ropes, for example— may need replacing or adjusting over time due to wear and tear. Problem: The contactors or relays deteriorate, creating high resistance. You can normally tell if a contactor is pulling in correctly, but it isn’t unusual for a lift motor room to be filled with the sound of chattering relays. It’s worth checking whether terminal screws have become loose after thousands of operations, since loose screws can cause a contact to burn up, resulting in high resistance. If dust or dirt is allowed to get onto an open contact it can cause an arc which can also wear down the contact and produce high resistance. This is why it is hard to determine the life-cycle of a contractor: on-site conditions will vary in cleanliness, as well as temperature. In order for a lift to do what it does—run at high speed, safely, without taking up more space than it needs—then the equipment and components need to be understood and maintained. The smallest anomaly can put a lift out of service, inconveniencing an enormous number of people, especially in tall buildings or ones with only a small number of lifts.
Building & Facilities Management – December 2020
