From controllers, observation windows and sample holders to HTM software

How well and purposefully high-temperature furnaces can be used depends not only on which temperatures are reached in which room. It is largely determined by how conveniently and accurately temperatures can be set, how the heat treatment process is recorded, or how the samples enter the furnace and are held there. Also decisive is how the gas composition can be adjusted on the sample, which process parameters of the heat treatment can be measured, which observations can be made on the samples and much more.

HTM Reetz GmbH provides a wide range of accessories that extend the application possibilities of the furnaces and facilitate the work of the operator.

Control units

HTM Reetz GmbH offers the appropriate control units for all its furnaces and high temperature devices. The control units are usually separate devices that can also be used for third-party products with corresponding performance parameters.

Temperature controllers, power controllers and PC interfaces

The temperature controller can be selected from a large list of well-known manufacturers. 
PLC devices are used for more complex control tasks. Roughly one can always choose between:

  • Simple setpoint control
  • Program control with 8 to … segments
  • Media connection to the heating program
  • etcetera

The power controllers used are selected according to the heating module used. 
Thus, for purely ohmic heating modules, the low-cost semiconductor relays are used, while for heating modules made of e.g. SiC or MoSi2, thyristor controllers with current limitation are used.

To meet the requirements of documentation, visualization and simplified operation as well as parameterization, our control units can be equipped with PC interfaces of different types:

  • RS- 232/485
  • Ethernet
  • Etc.

Software „HTMCTRL+”

Our range of accessories includes PC interfaces as well as our easy to use software “HTMCTRL+”.

The software has been continuously developed by us over many years and adapted to more and more temperature controllers and measuring devices.

The software enables the monitoring, programming, visualisation and storage of essential parameters, e.g. the following temperature controllers and devices:

  • Eurotherm 2xxx, 3xxx, 818, 902
  • PMA KS98
  • Pfeiffer vacuum gauge TPG 261/361
  • PICO TC-08
  • Siemens SPS S7-1200
  • MFC Vögtlin, Bronkhorst
  • Oriental motor, Stepper motors
  • Etc.

Sample holders and sample holder systems

For samples whose material is expected to react with the wall of the furnace chamber or which have to be held in a precise position, we offer appropriate sample holders. We manufacture crucibles and boats as well as other vessels from the following materials:

  • Oxide ceramics such as aluminium oxide, aluminium nitride, zirconium oxide
  • Quartz glass
  • Graphite
  • Refractory metals such as tungsten and molybdenum

Rotating sample holders for completion

They complement e.g. rheometers for viscosity measurements of melts or facilitate the all-round observation of objects.

For furnaces with vertical alignment of the tube axis, we recommend the use of rack structures that allow stacking of the samples.

Insert pipes and end insulation

Use of the insert tube as working tube

With the HTM tube furnaces LOSA, LOBA and LORA, the heat conductor support tube can be used as a working space for work in the air. For work in other environments, we offer vacuum-tight sealable insert tubes. Depending on temperature, type of gas and pressure, we use tubes made of quartz glass, heat-resistant steels and ceramic materials such as densely sintered aluminum oxide.

For the sealing of these tubes we provide metal flanges with elastomer seals, whose material is matched to working gases.

Additional equipment such as special sample holders, sample thermocouples, charging systems are adapted to the insert tubes.

Fibre-free end insulation

In order to keep the temperature in tube furnaces as constant as possible in all directions, it is advisable to equip the tube ends with special thermal insulation. As a rule, these are end plugs made of insulating material. If the working chamber is to be kept free of fibres, we can offer radiation shield packages made of metal or ceramic, which are also provided with feed-throughs for the thermocouples.

Charging systems

In the case of long tubes, complicated access conditions or strong temperature differences in the working chamber, precise positioning of the samples in the working chamber is facilitated by the use of charging systems.

For this purpose, sample tables are moved in the sample chamber with simple linear guides or, in the case of crystal growing systems, with motorized, time-controlled linear drives.

Additional thermocouple in the working chamber / Sample thermocouple

Thermocouple in the working chamber

To keep the furnace chamber free for samples, the thermocouple is often placed outside, near the heater. This ensures a faster response of the heater to setpoint changes, but also leads to systematic deviations between the displayed temperature and the sample temperature.

Additional thermocouple for accurate measurements

However, if exact maintenance of the sample temperature is desired, we recommend the use of a second sample thermocouple adapted to the sample position. 
Our control units can regulate the heating according to the signal of both variants.

Swivel frame / Racks

The swivel frames from HTM Reetz GmbH allow the LOBA and LORA type tube furnaces to be used in all working positions and to change the working position during heat treatment.

Equipment for heat treatment

Weighing of samples

During heat treatment, the sample material often reacts with the working gas. In other situations the samples release gas, for example during drying. Another aim of the heat treatment is the release of material from the samples, an example is debinding.

In all these cases, the course and success of the heat treatment can be made visible by weighing the samples. For this purpose, HTM Reetz has developed various solutions with which mass changes can be observed with a resolution < 10-4 at application weights of 100 g to 600 kg.

Dropping and collecting devices for thermal shock experiments

A large number of experiments aim to find out how materials react to sudden changes in temperature. For this purpose, HTM Reetz has developed equipment for vertical tube furnaces with which the samples can be dropped from the hot area into prepared baths or chutes. The atmosphere of the working chamber does not have to be left.

Gas supply

For work in defined atmospheres we provide gas supply units based on rotameters or mass flow controllers.

With rotameters the gas flow is adjusted manually, with mass flow controllers gas quantities and compositions synchronized with the temperature are possible. Our software HTMCtrl+ is used for this purpose.

Observation windows and transport lock

Mirrors and viewing windows

In many cases the direct observation of the sample during heat treatment is of great interest. Therefore, different solutions for observation windows and mirrors have been developed by HTM Reetz GmbH. They allow the observation of samples in tube furnaces either parallel to the tube axis or perpendicular to the tube axis.

Mirror systems allow the simultaneous connection of the samples with thermocouples, the setup of a backlight e.g. with blue light or even the injection of particles into the sample chamber. For gas chromatographic investigations, windows are available that do not disturb the temperature field.

Transport containers and locks

Under the condition that it is not possible to connect the furnaces to gloveboxes, we offer transport containers that can be flanged to the furnace under suitable conditions (e.g. filled in a glovebox) and emptied into the furnace. Small knife gate valves turn these systems into lock chambers.

Dosing systems

With continuously operating continuous furnaces, the problem of how to organise a defined material flow from the storage vessel into the furnace or from the furnace into the collecting vessel must be solved. HTM Reetz summarises the technical equipment required for this under the term “dosing system”. Our speciality are dosing systems which guarantee a continuous material flow under exclusion of air.

As a rule, it is essential to match the storage container and transport systems to the bulk material properties of the specific material. Screw conveyors, vibrating chutes and conveyor belts or combinations of these elements are used for transport.

Special weighing devices in combination with our “HTMCtrl+” software allow gravimetric dosing depending on other process parameters.

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