A Case Study By Stag Ag, Switzerland - Page 2 -
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The General Layout
Cements and additives are delivered to the Sedrun tunnel portal via railroad lines operated by Rhaetian Railways. Six silos with a storage capacity of 200m3 (7,062 cu. ft.) each are installed next to the tunnel portal. Via conveying lines, the transport freight wagons are pneumatically unloaded into the storage silos.
The main job is to feed the silos of the concrete unit at the bottom of the shaft.
To do so, cements and additives are discharged from the silos and filled into transporters. Via the transporters and a special dense phase pneumatic conveying system, the products are transported horizontally over a distance of 1,100 m (3,610 ft) to the intermediate station in the cavern in the shaft head. From the shaft head onwards, the material is then pneumatically conveyed in vertical direction via the lift shaft straight into the silos of the concrete unit at the bottom of the shaft. Diverters make sure that each of the silos is fed with the right type of material.
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A Case Study By Stag Ag, Switzerland - Page 3 -
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Concept Details
Rail unloading and silo feeding
Technical data
Number of transport freight wagons
which can be unloaded at a time 6
Unloading rate [t/h] 60
Conveying distance [m] 120
Conveying distance [ft.] 395
Conveying air volume [m3/h] 1,800
Conveying air volume [cu. ft./h] 63,558
The material is fed pneumatically from the transport freight wagons into the silos.
The cement is delivered in units of six cement silo wagons, holding 15 tons each. They stop right next and in parallel to the silos. The pneumatic conveying system, which is attached to the silo roof, is made up of a special steel conveying line featuring six tie-in points for the silo wagons and the required diverters.
The compressed air needed to unload the silo wagons is supplied by the central air compressor, which is located in the sheltered area of the silo unit. All instruments and measuring devices required for the supply of compressed air are installed on-site.
During the silo feeding process, the dust is separated from the conveying air stream by pneumatically cleaned waste air filters (one per silo). This guarantees the highest level of purity for the various products involved.
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A Case Study By Stag Ag, Switzerland - Page 4 -
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The silos at the tunnel portal
Technical data
Number of storage silos 6
Storage capacity per silo [m3] 200
Storage capacity per silo [cu. ft.] 7,062
Six steel silos with a rated capacity of 200 m3 each are used for storing cement and additives.
The silos are supported by a single large steel construction. The steel sub-structure is covered with metal façade panels to protect the free space underneath against the effects of weather. Thus, this space may be used for the installation of the compressed air supply unit, all the other required appliances and machines as well as the system control unit.
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A Case Study By Stag Ag, Switzerland - Page 5 -
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Cement discharge from the silos
Technical data
Number of silos 6
Discharge rate [t/h] 200
Conveying distance [m] 30
Conveying distance [ft.] 98
Air slide conveyors and the required slide diverters have been fitted to handle the discharge of the various cement types from the silos into the two downstream transporters. Special aeration jets which are fitted to the silo cones guarantee a continuous discharging of cement from the silos. The silos are closed by pneumatic slide gates.
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A Case Study By Stag Ag, Switzerland - Page 6 -
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Pneumatic conveyance from the silos to the intermediate station in the shaft head (1,100 m)
Technical data
Number of transporters 2
Capacity per transporter [m3] 6
Capacity per transporter [cu. ft.] 212
Conveying rate [t/h] 30
Conveying distance [m] 1,100
Conveying distance [ft.] 3,610
Two transporters pneumatically convey the bulk material from the silos to the intermediate station of the cavern at the shaft head. The transporters operate in tandem. The material is transported through a special steel conveying line (dense-phase pneumatic conveying technology) to the intermediate station.
Wherever a change of direction is required in the conveying line, special tube elbow fittings and basalt-reinforced elbow fittings are installed. At the end of the conveying line in the lowest shaft head section, the cement may be fed in either one of two transporters with a capacity of 12m3 each.
Pneumatic conveyance from the shaft head to the concrete unit at the bottom of the shaft (950 m)
Technical data
Number of transporters 2
Capacity per transporter [m3] 12
Capacity per transporter [cu. ft.] 424
Conveying rate [t/h] 35
Conveying distance [m] 950
Conveying distance [ft.] 3,115
Two transporters pneumatically convey the bulk material from the shaft head to the concrete unit. The transporters operate in tandem. The conveying air is supplied by a separate air compression unit, which is located near the conveying line in the shaft head.
At the end of the conveying line at the bottom of the shaft, the material is then fed directly into the five silos of the concrete unit. The correct filling of the silos is guaranteed by special STAG diverters.
The vertical conveying line in the shaft is suspended in the shaft head and is merely guided through the shaft.
Compressed air supply unit
Technical data
Total number of compressors 5
Installed capacity [kW]
silo unit 4 x 160
shaft head cavern 2 x 75
The compressed air for the entire conveying facility is supplied by two systems. The compressed air systems comprise all components required for the operation of the facility (working air, conveying air, controlling air), and include the required measuring devices, instruments as well as the air treatment unit with the refrigerated air dryer.
The system installed next to the silos at the tunnel portal supplies compressed air to the following sections of the facility:
• rail unloading area
• silo unit
• silo discharge unit
• pneumatic conveying line to the intermediate station in the cavern
Three screw compressors are needed to supply the required amount of compressed air. A fourth compressor is fitted as a back-up unit.
The unit located at the intermediate station in the cavern at the shaft head supplies pneumatic conveying air for the section down to the concrete unit at the bottom of the shaft.
At the intermediate station, one compressor is required. A second compressor is fitted as a back-up unit.
System control and electric installation engineering
The main control cabinet is positioned in the control room located at the silo unit near the tunnel portal. The entire system, including the pneumatic cement conveying system, may be monitored and controlled using the graphics display and the keyboard which are part of the main control cabinet. All status reports and malfunctions of any system component are visualised individually. All sub-control functions of the system are connected to the main control cabinet by a bus system. A separate I/O cabinet is located on the silo roof of the silo unit near the tunnel portal for the diverter sensors and actuators on the silo roof.
The rail unloading section is equipped with a cabinet with an electronic text display of its own. All functions and system messages such as silo selection, air supply (start, stop), silo filling levels and malfunctions are displayed / selected via the electronic text display and the keyboard (OP).
Another control cabinet is fitted in the cavern at the shaft head for the further transfer of the material into the silos of the concrete unit at the bottom of the shaft. All malfunctions and status reports of this section of the system are displayed one by one on an electronic text display whereas malfunctions in other sections are only visualised as general faults. For fault elimination purposes, this section of the system may be operated manually using the keyboard once it has been enabled by the main control unit. The section is connected to the main control unit near the tunnel portal by a bus system.
Next to the silos of the concrete unit, yet another control cabinet may be found. All malfunctions, status reports and troubleshooting processes are visualised in the same way as in the shaft head cavern control cabinet. This cabinet is also linked by the bus system to the main control unit near the tunnel portal.
Cement and additives are requested via the electronic text display, the commands are entered via the keyboard. The material is automatically supplied / conveyed from the tunnel portal silo unit via the intermediate station to the selected target silo at the bottom of the shaft.
For more information on STAG AG, please visit:
https://edir.bulk-online.com/profile/2478-stag.htm
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Pneumatic Conveying Technology: A Case Study by STAG AG, Switzerland
A Prime Example of Pneumatic Conveying Technology and
Bulk Material Logistics
The companies involved in the Swiss NEAT (or New Alps Transversal Route) project, Europe’s largest tunnel building project, have to excel themselves every day. Just now, STAG AG Bulk Material Technology of Maienfeld, the Grisons, Switzerland, handed over the longest pneumatic conveying system to the customer. This is not only the longest pneumatic conveying system within this project but the longest ever in the company’s history. The system conveys several additives such as cement and fly ash over a total distance of 2,190 m (7,185 ft) to supply the central concrete unit in the cavern at the bottom of the shaft, next to the multi-function station.
Some six years ago, the first feasibility studies for this complex project were commissioned. Not least the sophisticated system layout, the wealth of experience in the area of bulk material handling and related areas and the knowledge transfer with STAG Ltd., which is based in South Africa, helped STAG win the supply contract for this project in the late autumn of 2002.
The concept covers the full range of bulk material logistics, from the unloading of RhB freight wagons to the feeding of the central concrete unit at the bottom of the shaft. The material is first discharged from the silo unit, which is located at the tunnel portal, and then pneumatically conveyed to the intermediate station of the cavern at the shaft head (1,100 m or 3,610 ft). From the cavern onwards, additives are conveyed into the St Gotthard Massif via a vertical shaft (some 800 m or 2,625 ft deep). Afterwards, they are fed into the central concrete unit, which is another 150 m or 490 ft away. The entire conveying system stretches over some 2,190 m or 7,185 ft in length.
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