System for screening ballast with two screens

A ballast sieving system capable of moving parallel to a working direction, comprising:

• a sieving installation comprising at least a first sieve having a first soiled ballast inlet, a first clean ballast outlet which is located in front of the first soiled ballast inlet in a first direction parallel to the working direction and a first discarded ballast outlet, and at least one second sieve having a second soiled ballast inlet which is located behind the first soiled ballast inlet in the first direction, a second clean ballast outlet which is located behind the first clean ballast outlet and in front of the second soiled ballast inlet in the first direction and a second discarded ballast outlet,
• a set of one or more rerouting conveyors capable of collecting and conveying, in the first direction, a flow leaving the second clean ballast outlet and a flow leaving the first clean ballast outlet, the set of one or more rerouting conveyors comprising one or more rerouting collection conveyors for directly collecting the flow leaving the second clean ballast outlet and conveying it in the first direction,
• a set of one or more discharge conveyors capable of collecting and conveying, in a second direction parallel to the working direction and opposite the first direction, a flow of discarded ballast from the first discarded ballast outlet and a flow of discarded ballast from the second discarded ballast outlet, the set of one or more discharge conveyors comprising one or more first discharge collection conveyors, located directly below the first discarded ballast outlet to collect a flow of discarded ballast from the first sieve and to convey it in the second direction,
• an excavation assembly, and a set of one or more excavation conveyors, capable of transferring soiled ballast from the excavation assembly to a first distributor while constituting an incident soiled ballast flow,
• wherein
• the one or more rerouting collection conveyors extend under the first sieve at a lower height than the first discharge collection conveyor(s), and
• the second sieve comprises a discarded ballast inlet suitable for being supplied by the first discharge collection conveyor(s), and a spout for passing the flow of discarded ballast coming from the first sieve from the discarded ballast inlet to the second discarded ballast outlet, and
• the first soiled ballast inlet is positioned between the excavation assembly and the second soiled ballast inlet, and the first sieve is positioned between the excavation assembly and the second soiled ballast inlet.

A ballast sieving system capable of moving parallel to a working direction, comprising

• a sieving installation comprising at least a first sieve having a first soiled ballast inlet, a first clean ballast outlet which is located in front of the first soiled ballast inlet in a first direction parallel to the working direction and a first discarded ballast outlet, and at least one second sieve having a second soiled ballast inlet which is located behind the first soiled ballast inlet in the first direction, a second clean ballast outlet which is located behind the first clean ballast outlet and in front of the second soiled ballast inlet in the first direction and a second discarded ballast outlet,
• a set of one or more rerouting conveyors capable of collecting and conveying, in the first direction, a flow leaving the second clean ballast outlet and a flow leaving the first clean ballast outlet, the set of one or more rerouting conveyors comprising one or more rerouting collection conveyors for directly collecting the flow leaving the second clean ballast outlet and conveying it in the first direction,
• a set of one or more discharge conveyors capable of collecting and conveying, in a second direction parallel to the working direction and opposite the first direction, a flow of discarded ballast from the first discarded ballast outlet and a flow of discarded ballast from the second discarded ballast outlet, the set of one or more discharge conveyors comprising one or more first discharge collection conveyors, located directly below the first discarded ballast outlet to collect a flow of discarded ballast from the first sieve and to convey it in the second direction,
• at least one first distributor,
• wherein
• the one or more rerouting collection conveyors extend under the first sieve at a lower height than the first discharge collection conveyor(s), and
• the second sieve comprises a discarded ballast inlet suitable for being supplied by the first discharge collection conveyor(s), and a spout for passing the flow of discarded ballast coming from the first sieve from the discarded ballast inlet to the second discarded ballast outlet, and
• the first distributor is able to distribute an incident soiled ballast flow between the first soiled ballast inlet and the second soiled ballast inlet, according to one, two or three of the following operating modes:
• a distribution operating mode, in which the first distributor is able to distribute the incident soiled ballast flow between the first soiled ballast inlet and the second soiled ballast inlet;
• a return operating mode to the second sieve, in which the first distributor is able to direct the incident soiled ballast flow entirely toward the second soiled ballast inlet;
• a return operating mode to the first sieve, in which the first distributor is able to direct the incident soiled ballast flow entirely toward the first soiled ballast inlet.