Subject Area: Passenger Lifts
When the passenger lift mechanisms were due for replacement at Dun Laoghaire Shopping Centre, the centre management initially viewed this as an inconvenient and expensive maintenance requirement.
However, instead of just seeking a like-for-like replacement they took the time to research what was available on the market. Obviously passenger lift technology has advanced considerably since the original lift installation in 1976.
The main choice was between a modernisation of the existing units or a completely new installation. The cost was similar for both options but as 50% plus of materials could be reused (guide rails, counterweight system and car frame) the decision was taken to modernise and hence minimise the environmental impact.
After evaluating various quotes the contract was given to the original lift installer, Otis.
The original lifts were operated by means of heavy duty electric motors driving a series of four steel ropes mounted on a drive pulley, shown in the photograph below. These ropes can be expected to be changed on average every 5 to 7 years.
The new installation is quite different. A much smaller electronically controlled motor drives four lightweight (but very strong!) belts. The belts are constantly monitored by a pulse system and their life expectancy is a minimum of 10 years.
The lower inertia of the new mechanism means that the power required to move the lift from a standing start is hugely reduced. The smaller motor combined with the ‘smart’ electronic controls can therefore operate each lift with a much reduced electricity requirement.
They are known as the “regen” series and actually feed power back into the system when the units are operating under their own weight and the control system is used as a brake. This can be observed on the check meter when the meter actually runs backwards at these times.
The table below shows the original amperages required to move the lift from a standing start, and then to run the lift between floors in three different loading conditions. It can be seen that it required a considerable spike in electrical input to get the lift moving, and then a rather lower load to keep it moving to the next floor.
By comparison, the table below shows the electrical load requirement for the new arrangement under the same three load conditions. It can be seen that the spike required to get the lift moving has almost disappeared, and the steady state load to keep it moving between floors is much lower than the old arrangement.
Overall, the electrical requirement for running the lifts each day will probably have reduced by about half. The peak load has reduced by 79%.
When equipment of any type reaches its end of life, the obvious choice of buying an equivalent replacement isn’t always best. It makes sense to stand back and take the opportunity to explore other options. An unwelcome need for capital spend may also be an opportunity for a significant improvement in environmental performance, and a significant reduction in operating costs.