DeSeM Lifts Ltd. - Hydraulic or Traction Drive Information
There are two main types of lift drives available in Europe, the most common being Hydraulic and secondly the Electric (Traction).
Both have their position in the market place, the hydraulic lift is a more common heavy duty work horse, while the traction is more suited to high rise, high frequency use.
The hydraulic lift in the standard design will be a direct acting hydraulic system without the need for ropes, the need for ropes is decided by the length of travel.
In the direct acting system the lift travel is directly related to the hydraulic ram length, basically the travel the hydraulic ram can do is the travel the lift will do.
When the travel exceeds the design length of the longest hydraulic ram, ropes are used in what is commonly known as a 2:1 indirect acting design, this means that the lift travel can be twice the length of the hydraulic ram.
This feature becomes more relevant after 20 metres of lift travel.
The hydraulic system is generally regarded as a cost effective, efficient means of driving the lift.
One of the main advantages being, that all down travels are allowed and governed by gravity, although the hydraulic restrictor valve will regulate the speed in the down direction.
This restrictor valve is also regarded as the lifts main safety device only allowing the controlled descent of the lift within the design parameters.
In the event of a catastrophic failure such as a hose rupture, the restrictor valve ensures controlled and safe descent of the lift without any passenger being exposed to any dangerous events.
Hydraulic direct acting lifts are normally more cost effective in buildings where the travel is no more than 20 metres whilst moving heavy loads, above that height the 2:1 design would be employed.
The initial capital outlay is usually between 15 and 20% less than a comparable traction option.
Traction lifts are more often than not used for rapid passenger movements, the lift is driven both up and down, with the aid of a counter balance weight.
The counterbalance weight reduces the motive power requirements of the traction lift, but will require a larger lift shaft to accommodate both the lift car and the counterbalance weight.
Ropes are an essential part of the lift design being attached to the lift car travelling frame, wrapped around the drive pulley and back to a fixed position within the lift shaft.
These lifts are designed either as top drive with a motor room above or as bottom drive with the motor room on the lowest floor.
There are derivatives of these basic systems top side drive or bottom side drives this just means the motor room is at the side of the lift shaft at the top or the bottom.
In high rise situations the electric traction lift becomes the only sensible option and on extremely long travels there maybe a lift lobby on an upper floor, where passengers transfer into another lift so that they can continue their journey to the very highest levels.
A more recent development has been the motor room less (MRL) lift, this is to some degree a false description as a motor room is still required, but instead of creating a motor room space as previously described, the motor room is design to be in the lift shaft at the top or bottom.
These lifts are again best used in high rise, high use applications.
De/S/eM’s design preferences are for hydraulic systems which are ideally suited to 95% of our customers needs, we supply heavy duty hydraulic lifts into warehousing, distribution and storage applications.
By far our largest area of operation is self storage, where the facilities are usually 7 floors or less with modest inter-floor travel distances.
The quality of the lift travel is excellent and we have devised our own quality parameters, ask to see the “pound coin test”, the coin is placed on it’s edge whilst the lift is travelling and remains in that position during a complete lift travel cycle.
All our lifts feature a levelling system (+/- 5mm) which ensures the lift re-levels at the floor as it is being loaded so counteracting the natural compression of the air in the hydraulic system as the load is applied to the lift car.