The dust extractor extracts a large part of the dust in processes in which particles are generated and dust formed. Similar to the function of a cyclone, certain particle sizes are separated in the bottom section. A filter can protect the remaining piping from dust and soiling.

All standard process gases can be used for thermal processes. In the case of combustible gases, corresponding safety assemblies are added to secure operation of the plant automatically and ensure that it complies with existing regulations.
The gas supply consists either of a gas flow sensor with manually adjustable valves for the throughput quantity or of electronic mass-flow controllers. In the event of toxic and combustible gases, corresponding safeguard measures are taken. The gases are removed by evacuation and combustion or by directing them out of the workspace.
The design of the gas supply depends on the respective process desired. For example, gases can be rinsed directly into the retort or also metered outside the retort. It can also be the case that a process gas is metered in the retort and a protective gas outside.

The safety devices for combustible or toxic gases consist as a rule of gas paucity devices which regulate both the pre-pressure as well as the gas flow of the working gas. In the case of a lack of gas the processes are automatically interrupted and a rinsing process initiated. In order that sufficient rinsing gas is available for the safety rinsing and that a gas paucity alarm prevents a hot plant from being rinsed free, the protective gas must be stored in tanks. These tanks contain the entire rinsing amount and are part of the safety system.
The toxic or combustible gases are burnt at the gas outlet in suitable combustion devices insofar as the gases in question are not halogenated gases.

The chamber furnaces are heated from four sides in the standard version. A heating cage heats the floor, roof and the side walls. This ensures that a good temperature distribution is achieved. For particularly demanding applications the door and rear wall can also be additionally heated. The appropriate heater is required on the interior side for this. Power feed lines, temperature sensor (pyrometer or thermo-sensor) and the flange must be present on the outside. The ancillary heating elements are regulated via a low voltage transformer and upstream thyristor.

Every plant that is not run on air must have an atmosphere change. For lower quality demands on the residual gas composition this can be achieved with rinsing. However, this would cause perceptible wear in a high temperature furnace because the porous insulation can hardly be rinsed so that it is completely free of oxygen. The residual oxygen would react with the insulation when the furnace is heated up and cause wear.
For this reason a simple vacuum pump should at least be employed in these furnaces for atmosphere change. Simple evacuation and filling with protective gas leads to a residual oxygen portion of about 200 – 500 ppm oxygen. This figure can be significantly reduced by performing evacuation and flooding several times.

Vacuum processes generally require lower end pressures and are also frequently dependent on higher vacuuming. In this instance backing pumps are combined with straight lobe pumps. This reduces the final pressure to a figure which is about 10% of the final pressure of the backing pump. This is achieved with significantly higher vacuuming. The combinations depend on the furnace size and customer requirements.

For high vacuum operation, additional oil diffusion pumps or turbo pumps need to be employed. Also the dimensioning of this assembly group is greatly dependent on the application. Graphite furnaces can work with well dimensioned oil diffusion pumps in the range of 10-5 mbar. Furnaces that have no fibre insulation in the vacuum chamber achieve figures in the range of 10-6 mbar or better.

The thermal debinding or pyrolyse releases gaseous hydrocarbons that sooner or later condense. In order that this does not happen in the pipes to the condensation trap or combustion apparatuses, the pipes are heated. The debinding can be effected in one of two ways. The simpler method involves the generation of a slight overpressure in the furnace and a fall of pressure towards the gas outlet so that the gaseous components flow in the direction of the gas outlet. For special applications or if the debinding is to be carried out at a certain process pressure, this effect can also be achieved with a special vacuum pump. The vacuum pump removes the gases and a pressure regulator value maintains the furnace pressure at a stable figure. This enables debinding at, for example, 800 mbar and with a constant gas flow.

The binder gases are either condensed, or preferably actively burnt. The combustion device must be configured to accept the corresponding binder quantity and vacuum devices must be installed in the manufacturing plant.

High temperatures are generally regulated using pyrometers. These pyrometers have a pre-defined measuring range. We employ pyrometers with a standard 350-2500°C.
When the process starts the furnace is at room temperature and must be initially heated undefined in the pyrometer measuring range. With sensitive batches this is unacceptable and the temperature must be increased from room ambient temperature in a regulated manner. To do this a so-called sliding thermocouple is installed in the high temperature furnaces. The thermocouple runs automatically after charging in the furnace and registers the current temperature during heating up. In the case of an adjustable switching temperature the pyrometer carries out the regulation and the thermo sensor leaves the hot zone because it would not withstand the following high temperatures without sustaining damage. During cooling the thermocouple returns automatically into the furnace and regulates the automatic processes at low temperatures.

Pyrometers are visual radiation measuring devices. In a vacuum furnace the pyrometers must measure through a vacuum-tight disc. This disc can become dirty and thus influence the recorded measurement. To check the regulating pyrometer a second reference pyrometer can be supplied as a group. The window of this pyrometer is protected against soling by a valve. The valve opens, e.g. every 30 minutes for 30 seconds. The recorded result can be documented in the data recording system. If the measuring result in the reference pyrometer suddenly jumps, the disc of the regulating pyrometer is probably soiled and must be cleaned before the next run.

When operating with a partial pressure of a gas, the gas can be passed at a constant flow through the mass-flow controller in the furnace. At the defined furnace pressure in the programme table, e.g. 80 mbar, the regulating valve would open and the gases be siphoned off from the furnace until the target pressure is achieved. The valve would then slowly close and only allow the removal of gas quantities that the mass-flow controller allows into the furnace so that the pressure remains constant. Additional pressure alterations due to heating up and cooling down can be cleanly regulated by this group. It can also regulate a defined overpressure.

The graphite furnaces are generally configured for temperatures up to 2200°C. Higher temperatures are possible, however greatly rising performances need to be installed. A temperature increase of 2200 to 2500°C already makes, for example, an increase in performance of 25% necessary. It is also important to ensure that the cooling water performance is also correspondingly adapted.

The plant can be regulated manually or automatically via an SPC. In this event a touch panel is used as standard for operation. The WIN CC process visualisation, which runs on the plant’s PC, provides substantial advantages over the use of a touch panel for process documentation, and it is easier to handle. All relevant process parameters including power, voltage and performance at a particular point in time are documented. It enables precise process analysis. Batch data, special features, times and all important parameters can be stored along with the process.
The plant can be started at any point in time via data and time.

If there is insufficient cooling water installed, we can also supply cooling machines for our plant as standard. Special equipment means that our plant is also suitable for set-up outdoors and can be provided with roofing for this purpose.
Greater performance can be configured separately on a case to case basis.