The HAG is a fully automatic system for fusion, measurement of moisture, and thermogravimetric analysis (TGA)/ loss of ignition (LOI) determination. The system has following components which can be flexibly and individually combined:
- Input tray magazine
- Dosing module
- Fusion module
- Cleaning module
- TGA module
Plastic vials with 20 to 50g of sample materials are manually or automatically placed into the tray of the input magazine. All following steps are fully automated: Sample dosing for fusion and TGA, flux weighing, fusion and transport of fusion beads to the XRF, cleaning of crucibles and casting dish, measurement of moisture and TGA. The remaining sample and vial is returned to its original position in the tray.
Input tray magazine
Several options of the sample input magazine are available including 62 position sample magazine and a 200, 300 or 400 vial position tray magazine. The magazine can be connected to the preceding preparation cell or can be manually loaded. There is also a 10 position manual sample input magazine in the weighing unit where samples can be registered.
The tray magazine has a xy gripper transporting the vial inside the unit and into a barcode reading position where the sample ID can be established. The vial is placed on a transport system and transported to the fusion machine. Priorities can be set and changed on the fly. The PrepMaster control system visually indicates the status of each vial like, e.g., ‘to be analyzed’, ‘already analyzed’, ‘in fusion machine’, ‘high priority’ etc. In case that a bead is rejected within the system, the sample is collected from the magazine and automatically re-run on the system.
The dosing unit consists of up to three dosing stations, a sample mixing station, buffer position for TGA and Platinum crucible, and a release agent dosing station. All stations are operated by a small robot.
Samples in vials are placed into one of the three dosing units. For the fusion process, flux and sample are alternately weighed into the crucible to achieve an optimal dilution of both substances. Subsequently, the crucible is transferred to the mixing station, where flux and sample are mixed together. Optionally, a release agent can be added. Finally, the crucible is placed on a turntable ready to go to fusion.
For TGA, the sample will be weighed into a TGA crucible and transported to the TGA module for moisture and LOI determination.
In every case, the control system allows titrating of different types of flux as well as different sample and flux volume.
According to the sample load, the fusion module consists of 4, 6 or 8 heating stations. Each heating station has two heating positions for the crucible and the casting dish. A linear system transports the sample from the turntable to the heating station, fused bead to the XRF belt, and dirty crucibles and casting dishes to the cleaning station.
The crucible is heated by induction. During this process, the sample can be swirled to aid the mixing. In parallel, the casting dish is heated to a predefined temperature. When the heating cycle is complete, the sample is automatically poured into the casting dish. The bead is allowed to cool within the casting dish. Depending on the sample type different cooling regimes can be used such as fast cooling with compressed air.
The heating station is under control of a pyrometer. Therefore, it is possible to setup individual heating profiles for every sample type like, e.g., 500°C for 2 min, 1000 °C for 3 min and 1100 °C for 1 min.
Before transported to the XRF, a special detector confirms that the fused bead is not cracked or moon shaped. Optionally, a camera system can be used to exclude that the bead is crystalline.
The automated cleaning module for dirty crucibles and casting dishes consists of one or two ultrasonic baths, a washing station and a drying station. 14 crucibles and casting dishes can be cleaned simultaneously in the ultrasonic cleaning station. Crucibles and casting dishes are placed in the ultrasonic bath at elevated temperature in citric acid. Afterwards, they are transported to the washing station where they are washed with normal tap and demineralized water. Before being returned to the dosing module they are dried with hot air blowers. All cleaning parameters can be adjusted with the PrepMaster system.
Automatic TGA Module
The TGA module consist of 2 to 4 TGA furnaces each running with a predefined temperature, a cooling station and a cleaning station. The number of furnaces depends from the number of temperatures at which the LOI needs to be reported. Inside the TGA module, a multi arm transports the sample from each furnace to the next as well as to the cooling and cleaning station.
Main Advantages of the Automatic Fusion Process
- Increased precision: Every sample is processed identically and is not subject to human error. Since TGA can be simultaneously measured in all samples, moisture can be determined and corrected for in the analysis. This eliminates the need for keeping soils at 100°C.
- Improved health and safety: Automation totally eliminates manual handling of hot crucibles for fusion and TGA. Some manually operated systems also have open flames and require the use of highly flammable gasses which might potentially cause health damage.
- Reduced mix up: Using automation drastically reduces the risk of sample mix up especially if the automation is connected directly to the XRF. The manual process includes many stages where the samples can be mixed up such as weighing, labeling, fusion, bead labeling, loading and registering into the XRF. As these functions are completely taken over by the automation, the need for human intervention is significantly reduced.
- Reduced mundane tasks and labour saving: Mundane and physical tasks can result in fatigue of the operator and careless weighing and sample handling. Automation significantly reduces these risks and releases the operator’s workforce for more efficient and responsible tasks.