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SEFAC screw/nut system vs hydraulic systems
The advantages of SEFAC screw/nut system in comparison to hydraulic systems are numerous.
SEFAC screw/nut columns are naturally safe
The SEFAC «screw/nut» principle is intrinsically safe and irreversible. This irreversibility has an effect on every millimeter on account of the inclination of the screw thread. This inclination is too weak for the fork to go down without mechanical activation of the engine. Consequently, there is no risk for the vehicle to go down without the voluntary mechanical activation of the engine.
Besides, we ensure the safety of our equipment by testing every column with our test bench before shipping them. During these tests, every column is overloaded with up to 50% overload (+50% of the nominal lifting capacity).
By comparison, the hydraulic technology is not intrinsically safe. It is necessary to add a safety system: the ratchet. To work safely, this ratchet has to be activated and locked onto a notch, +/- every 5 cm. Therefore, it is not safe at every height.
With SEFAC columns, you really choose your lifting height
When in the raised position, hydraulic columns can reach over 4 meters and unless the vehicle is perfectly level the column and safety rack can be dangerously close to the body. This may result in damage to the body of the vehicle. If a vehicle is lifted with deflated or damaged tires, defective suspension, etc. it may also result in damage to the safety racks.
These safety racks must insure the «mechanical» irreversibility of the hydraulic cylinder with a ratchet. However, to keep the load in a safe condition, this ratchet has to be activated and locked onto a notch, every +/- 5 cm, it is not safe at every height. As a consequence, you need to lift up or down the fork to lock the ratchet and work safely!
With SEFAC columns, it is simply enough to loosen the finger of the (up/down) button to be totally safe. No additional maintain system, no ratchet, thanks to the natural irreversibility of heavy duty screw/nut column lifts!
The technology used by SEFAC removes the risk of buckling
There is no risk of buckling with SEFAC mobile column lifts because the screw is suspended.
In hydraulic installations, the hydraulic cylinder is fixed at the top and the bottom and exerts a force upwards whereas the load exerts a force downwards. So, there is a risk of buckling as soon as guiding plates and guiding seals are used causing premature wear of the cylinders.
With SEFAC system, the screw is suspended. Efforts are only exerted vertically from the top to the bottom. Therefore, the screw works in pure traction.
Simplified design = simplified maintenance
Mechanical technology results in a simplified design with less components and thus less maintenance:
- on SEFAC screw/bronze nut mobile columns, it is just necessary to grease the nut manually or thanks to automatic greasers (to be replaced once a year). This nut should be changed on average every 5,000 cycles (i.e. every 10 years considering 2 lifting cycles a day). This operation requires only 15 minutes for the assembly and the reassembly. The top bearing of the screw must be greased once a year;
- with ball-screw system, the mechanical maintenance is even more reduced: the top bearing of the screw must be greased once a year but the nut itself only once every 5 years.
Hydraulic equipment require more maintenance: the cylinders are exposed and as seals are not 100% waterproof, you will need to:
- Purge regularly (once or twice a year);
- Change oil of the four containers (every year or two years);
- Grease regularly wipers;
- Check the cylinder itself: as soon as the cylinder has been damaged, it needs to be replaced, since the seal is not guaranteed anymore;
- Replace regularly seals and guide blocks to avoid buckling.
In fact, the declaration: «hydraulic = no maintenance» is clearly wrong.