In a precast element plant, the capacity of the facilities for concrete transport need to meet the requirements of the element production. Most precast plants use a bucket conveyor system.
What must be taken into account when designing a bucket conveyor transportation system?
What kind of equipment does a bucket conveyor concrete transportation system include?
A bucket conveyor system for a precast plant consists of one or more rail lines and one or more conveyor buckets with additional equipment.
The construction of the bucket conveyor system already should be taken into account when the design of a new precast plant starts.
Photo 1. Rotating conveying bucket which moves on two rails
Photo 2. Conveying bucket with bottom hatch discharge
Conveyor buckets operate from rails, driven by an electric motor. Usually the conductor rails are placed next to one of the conveyor rails. With very short transport distances, other solutions of the power supply also are possible. Buckets move along on the rail system, which either is attached to the pillars of the production hall or supported by a separate steel construction. A separate steel construction often is required with the installation of a rail line in an old precast element factory, if the existing structures are not designed to bear the additional load.
A conveyor bucket moves either on one or two rails. When there is just one rail, the bucket may swing laterally. The two-rail version is more robust and more commonly used. A rail system may include curves, upward and downward slopes and crossings.
The concrete bucket plays ab essential role in the transportation system.
The bucket gets discharged either by rotating or by opening of the bottom hatch. Discharging through the bottom hatch is optimal for short transport distances, especially with smaller buckets.
A rotating bucket is well suited for long transport distances and larger volumes.
Photo 3. Conveying bucket on two rails, 90° curv
How is the system controlled? How is the ordering of concrete done?
A very important part of the bucket conveyor system in a precast element plant is the control system. The control system handles the concrete orders from the concrete order points and controls the bucket transport to the desired discharge points. The control system must work reliably to ensure a continuous production without unnecessary downtimes.
A concrete order is made from an order point, which can be installed stationary or portable. There may even be several order points. Nowadays orders are mainly handled wirelessly from portable devices.
A modern control system works almost completely automatically. It can properly adjust the moisture of the concrete as well as other necessary parameters. Orders received will be placed in the order queue.
Orders in the order queue, if necessary, can be prioritized, which means that orders with a higher priority will be handled first. Higher priority orders e. g. may concern casting machines that are producing continuously, which means that production interruptions must be avoided.
An order can also be sent automatically. In this case the control system follows the casting process, taking into account the concrete consumption and, automatically ensures that there always is a sufficient amount of concrete in the casting machine hopper, for example hollow core casting machine.
How does the concrete transport system get dimensioned?
At first it must be calculated, how much concrete is needed at different casting points in what frequency. Once these requirements have been clarified, it is possible to calculate how big the bucket and what the conveying speed need to be, in order to always in time provide the required amount of concrete to each discharge point.
In the case of a larger plant, it is worth simulating the concrete production and transport in advance, to ensure sufficient dimensioning. An under dimensioned concrete transport system may slow down the casting process or even stop the operation of casting machines. The control system also has a major influence in the prevention of such "bottlenecks". In addition, the capacity of the concrete mixing plant must be taken into account. If the plant’s capacity is too low, the bucket conveyor system cannot compensate for this.
What costs need to be taken into account when investing?
Well planned is half finished. When investing in a concrete transport system for a precast element factory, the planning costs are very low compared to the purchase price for equipment. Therefore, planning should be done very carefully.
Investments in equipment for a new plant include the rail and power supply system, buckets, control system, order system, receiving hoppers and a bucket washing system.
Installation costs include the costs of mechanical and electrical installation and eventually construction works. Installation can be done with own personnel under supervision of the supplier or as turn-key installation.
Photo 4. Bucket conveyor line to serve a casting machine
When the concrete transport is finished, the bucket gets moved to a cleaning station, where the washing system operates. Washing can be done with a high-pressure washer, either manually or automatically. A rotating bucket gets turned in the discharging position, the high-pressure washer starts and automatically washes the bucket from underneath. A bottom discharge bucket gets washed from above.
The cleaning station can be equipped with a washing water recycling system, separating aggregates and slurry water and pumping slurry water back to the concrete mixing plant for concrete production, which reduces the amount of clean water required.
Photo 5. Automatic cleaner in operation
Summary
The bucket conveyor system for concrete transport in a precast element factory needs to be planned carefully and possible future extensions should be considered. Eventually the mixer needs to be equipped with several discharge hatches, so that the rails can be placed in a flexible way and discharge can be done to buckets on several rail lines.
The structures of an old plant may limit the use of the system. Also, an existing concrete mixing plant with low capacity or inconsistent concrete quality due to, for example, inaccurate dosing or poor mixing, may cause problems or lead to bottlenecks in production.
Tecwill concrete transfer systems
Tecwill delivers bucket conveyor systems for both, small and large new and existing precast concrete element plants. Deliveries each include a modern control system, order systems and a bucket washing system.
For answering of any questions or further information, please feel free to contact us.
