BUCKET ELEVATORS

Bucket elevators are machines where explosions are very likely to occur. This is due to their speed (always exceeding 1 m/s) and to the possible persistence of dusts.  In order to avoid explosions, sources of ignitions must be prevented: belt slipping can be avoided by applying speed control systems to the tail. Belt alignment control systems can also be applied to prevent the belt itself and the bucket to rub against the equipment cage.These devices are not always a guarantee against explosions hazards. In this case the possibilities of explosion must be taken into account. According to the EU ATEX Directive, appropriate devices must be adopted to safeguard people’s health. PTM has sponsored researchers to test the pressure resistance of the bucket elevators at the FSA firing-ground in Germany. According to the research, when bucket elevators are built with the giv en criteria, they withstand the overpressure that is generated by a possible explosion. PTM bucket elevators have consequently been designed to withstand to the pressure generated by the explosion of the main transported dusts.
Consequently, venting panels on the ducts are not required, so the choice of the elevators position is no more related to the risk of fire and pressure generated by those panels.
In order to relieve the pressure generated by the explosion, upwards venting panels are placed on the driving head that is usually located in a safe area.
At any rate, flames and pressure will be conveyed into the product load and unload ducts, so the partitioning between all the connections and the other components of the plant must be implemented.
The partitioning can be both active and passive. In the case of regular dimensions and capacities, in larger equipments an active partitioning made by inert dust chemical suppression is more likely to be adopted.
In smaller equipments a passive partitioning made with rotary valves may prove more suitable.