Nabertherm GmbH

VHT 8/18-GR - VHT 500/18-KE
The compact furnaces of the VHT product line are available as electrically heated chamber furnaces with graphite, molybdenum, tungsten or MoSi₂ heating. A wide variety of heating designs as well as a complete range of accessories provide for optimal furnace configurations even for sophisticated applications.

The vacuum-tight retort allows heat treatment processes either in protective and reaction gas atmospheres or in a vacuum, subject to the individual furnace specs to 10⁻⁵ mbar. The basic furnace is suited for operation with non-flammable protective or reactive gases or under vacuum. The H₂ version provides for operation under hydrogen or other flammable gases. Key of the specification up is a certified safety package providing for a safe operation at all times and triggers an appropriate emergency program in case of failure.

Alternative Heating Specifications
The following heating systems are available for the different application temperatures:

VHT ../GR with Graphite Insulation and Heating

• „„Suitable for processes under protective and reaction gases or under vacuum
• „„Tmax 1800 °C or 2200 °C (2400 °C as additional equipment)
• „„Max. vacuum up to 10⁻⁴ mbar depending on pump type used
• „„Graphite felt insulation

VHT ../MO or ../W with Molybdenum or Tungsten Heating

• „„Suitable for high-purity processes under protective and reaction gases or under high vacuum
• „„Tmax 1200 °C, 1600 °C or 1800 °C
• „„Max. vacuum up to 5 x 10⁻⁵ mbar depending on pump type used
• „„Insulation made of molybdenum rsp. tungsten radiation sheets

VHT ../KE with Fiber Insulation and Heating through Molybdenum Disilicide Heating Elements

• „„Suitable for processes under protective and reaction gases, in air or under vacuum
• „„Tmax 1800 °C
• „„Max. vacuum up to 10⁻² mbar (up to 1300 °C) depending on pump type
• „„Insulation made of high purity aluminum oxide fiber

Standard Equipment for all Models
Basic version

• „„Standard furnace sizes 8 - 500 liters
• „„A water-cooled stainless steel process reactor sealed with temperature-resistant o-rings
• „„Frame made of stable steel profiles, easy to service due to easily removable stainless steel panels
• „„Housing of the VHT 8 model on castors for easy repositioning of furnace
• „„Cooling water manifold with manual stopcocks in supply and return lines, automatic flowmeter monitoring, openloop cooling water system
• „„Adjustable cooling water circuits with flowmeter and temperature indicator and overtemperature fuses
• „„Switchgear and controller integrated in furnace housing
• „„H 700 PLC control with clearly laid out 5.7“ touchpanel control for program entry and display, 10 programs each with 20 segments
• „„Over-temperature limiter with manual reset for thermal protection class in accordance with EN 60519-2
• „„Manual operation of the process gas and vacuum functions
• „„Manual gas supply for one process gas (N₂ or Ar) with adjustable flow
• „„Bypass with manual valve for rapid filling or flooding of furnace chamber
• „„Manual gas outlet with overflow valve (20 mbar relative)
• „„Single-stage rotary vane pump with ball valve for pre-evacuating and heat treatment in a rough vacuum to 5 mbar
• „„Pressure gauge for visual pressure monitoring
• „„Applications only allowed within constraints of operating instructions
• Cold-Wall Retort Furnaces up to 2400 °C

Additional equipment

• „„Tmax 2400 °C
• „„Housing, optionally divisible, for passing through narrow door frames (VHT 08)
• „„Manual gas supply for second process gas (N₂ or Ar) with adjustable flow and bypass
• „„Inner process box made of molybdenum, tungsten or CFC, especially recommended for debinding processes. The box is installed in the furnace with direct
• gas inlet and outlet and provides for better temperature uniformity. Due to a change in gas supply direction after debinding a clean process atmosphere for
• sintering is achieved.
• „„Charge thermocouple with display
• „„Temperature measurement at 2200 °C models with pyrometer and thermocouple, type S with automatic pull-out device for precise control results in the low
• temperature range (VHT 40 and larger)
• „„Two-stage rotary vane pump with ball valve for pre-evacuating and heat-treating in a vacuum to 10⁻² mbar
• „„Turbo molecular pump with slide valve for pre-evacuation and for heat treatment in a vacuum to 10⁻⁵ mbar including electric pressure transducer and
• booster pump (only VHT…/MO)
• „„Other pumps on request
• „„Heat exchanger with closed-loop cooling water circuit
• „„Automation package with graphic touch panel H 3700
  • 12" graphic touch panel H 3700
  • Input of all process data like temperatures, heating rates, gas injection, vacuum at the touch panel
  • Display of all process-relevant data on a process control diagram
  • Automatic gas supply for one process gas (N₂ , argon or forming gas) with adjustable flow
  • Bypass for flooding and filling the chamber with process gas controlled by the program
  • Automatic pre- and post programs, including leak test for safe furnace operation
  • Automatic gas outlet with bellows valve and overflow valve (20 mbar)
  • Transducer for absolute and relative pressure
• „„MFC flow controller for alternating volume flow and generation of gas mixtures with second process gas (only with automation package)
• „„Partial pressure operation: protective gas flushing at controlled underpressure (only with automation package)
• „„PC control via NCC with corresponding optional documentation and connection to customer PC networks

H₂ Version for Operation with Hydrogen or other Reaction Gases
In the H₂ version the furnaces can be operated under hydrogen or other reaction gases. For these applications, the systems are additionally equipped with the required safety technology. Only certified and industry proven safety sensors are used. The furnaces are controlled by a fail-safe PLC control system (S7- 300F/safety controller).

• „„Certified safety concept
• „„Automation package (see additional equipment above)
• „„Redundant gas inlet valves for hydrogen
• „„Monitored pre-pressures of all process gases
• „„Bypass for safe purging of furnace chamber with inert gas
• „„Pressure-monitored emergency flooding with automated solenoid valve opening
• „„Electric or gas-heated exhaust gas torch for H₂ post-combustion
• „„Atmospheric operation: H₂-purging of process reactor starting from room temperature at controlled over pressure (50 mbar relative)

The high­temperature furnaces HT 04/16 ­ HT 450/18 have proven reliability over many years in laboratory and production. Whether for quartz glass or glass ceramics, for sintering CIM components or for other processes up to a maximum temperature of 1800 °C, these furnaces afford the optimal solution for the sintering process.

High­temperature furnaces can either be insulated with fiber material or lightweight refractory bricks. Furnaces with fiber insulation achieve significantly shorter heating up times because of the low thermal mass. An insulation made of lightweight refractory bricks, on the other hand, has the advantage of better chemical stability.

These furnaces can also be tailored to specific processes by means of a wide range of additional equipment. The addition of a debinding package, for example, allows the use of these models as combi furnace for debinding and sintering in one process. Thermal or catalytic exhaust cleaning equipment rounds­off the system.

These gas tight retort furnaces are equipped with direct or indirect heating depending on temperature. They are perfectly suited for various heat treatment processes requiring a defined protective or a reaction gas atmosphere. These compact models can also be laid out for heat treatment under vacuum up to 600 °C. The furnace chamber consists of a gas tight retort with water cooling around the door to protect the special sealing. Equipped with the corresponding safety technology, retort furnaces are also suitable for applications under reaction gases, such as hydrogen or, in combination with the IDB package, for inert debin-ding or for pyrolysis processes.

Different model versions are available depending on the temperature range required for the process:

Models NRA ../06 with Tmax 650 °C

• Heating elements located inside the retort
• Temperature uniformity up to +/­ 5 °C inside the work space
• Retort made of 1.4571
• Gas circulation fan in the back of the retort provides for optimal temperature uniformity

Models NRA ../09 with Tmax 950 °C

• Outside heating with heating elements around the retort
• Temperature uniformity up to +/­ 5 °C inside the work space
• Retort made of 1.4841
• Fan in the back of the retort provides for optimal temperature uniformity

Models NR ../11 with Tmax 1100 °C

• Outside heating with heating elements around the retort
• Temperature uniformity up to +/­ 5 °C inside the work space
• Retort made of 1.4841

The RSRC rotary tube furnaces are particularly suitable for processes where continuously running batch material is heated for a short time.

The rotary tube furnace is positioned slightly inclined heated­up to the target temperature. The material is then continuously supplied at the upper end of the tube. It passes through the heated area of the tube and falls on the lower end out of the tube. The time of heat treatment results from the inclination angle, the rotational speed and the length of the working tube, as well as from the flow properties of the batch material.

Equipped with the optional closed loading system for 5 liter charge material incl. receptacle, the rotary tube furnace can also be used for processes under protective gas or vacuum.

Depending on process, charge and required maximum temperature, different working tubes made of quartz glass, ceramics or metal to be used. This rotary tube furnace is therefore highly adaptable for different processes.