The compact furnaces of the VHT line are available as electrically heated chamber furnaces with graphite, molybdenum or MoSi2 heating. A wide variety of heating designs as well as a complete range of accessories allow optimal furnace configuration for technically demanding customer processes. The vacuum-tight retort enables heat treatment processes either in protective and reaction gas atmospheres or in a vacuum, depending on the application, all the way to 10-5 mbar. With the appropriate safety technology, the furnaces are also suitable for operation with hydrogen.

Graphite – VHT ../GR

• Suitable for processes under protective and reaction gases or under vacuum
• Tmax 1800 °C and 2200 °C
• Graphite felt insulation
• Temperature measurement using type B thermocouple (version to 1800 °C)
• Temperature measurement using optical pyrometer (version to 2200 °C)

Molybdenum – VHT ../MO

• Suitable for processes under highly pure protective and reaction gases or under a high vacuum up as much as 10-5 mbar
• Tmax 1600 °C
• Insulation made of Molybdenum steel sheets

MoSi2 – VHT ../KE

• Suitable for processes under protective and reaction gases or in air or under vacuum
• Tmax 1800 °C
• Insulation made of high purity aluminum oxide fiber

Basic Version VHT (All Heating Concepts)

• Standard furnace sizes 8, 40 and 100 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
• Casing 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, open-loop 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 limit controller with manual reset for thermal protection class 2 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

Additional equipment

• Housing, optionally separable, for passing through narrow door openings
• Manual gas supply for second process gas (N2 or Ar) with adjustable flow and bypass
• Molybdenum or carbon-fiber-carbon retort with direct gas supply for clean atmosphere and improved temperature uniformity in the furnace chamber
• Charge thermocouple with display
• Two-stage rotary vane pump with ball valve for pre-evacuating and heat-treating in a vacuum to 10-2 mbar
• Cooling unit with closed-loop cooling water circuit

The use of automatic valves for process gas or exhaust air management and the powerful H 3700 controller allow the entire heat treatment process to be run fully automatically. The entry of all process data (temperatures, ramps, gas supply and vacuum) is easily controllable from a large, 12" graphic control panel. System status with all process-related data are clearly shown on a process control diagram. All valves and the vacuum pump can also be operated manually from here as well. The system has an automatic pre-program and post-program for purging the furnace chamber and also features automated leak testing.

• Features the same as basic version of VHT, plus:
• Automatic gas supply for one process gas (N2 or Ar) with adjustable flow
• Bypass for rapid filling or flooding of furnace chamber
• Automatic gas outlet with check valve and pressure relief valve (20 mbar)
• Single-stage rotary vane pump with check valve for pre-evacuating and heat treatment in a rough vacuum to 20 mbar
• Transducer for absolute and relative pressure measurements
• H3700 controller (10 programs with 20 segments each)
• Operation with 12" graphical control panel (touchpanel)

Additional equipment

• Mass flow controller for varying flow volumes and generating gas mixtures (with second process gas)
• Furnace pressure control with position-controlled exhaust valve (partial pressure control)
• Electric or gas-heated exhaust gas torch for process gas post-combustion
• Water-cooled exhaust gas cooler
• Condensate traps for separation of large amounts of binder
• Two-stage rotary vane pump with check valve for pre-evacuating and heat treatment in a vacuum to 10-2 mbar
• Pump stand with turbo-molecular pump and slide valve for pre-evacuating and for heat treatment in a vacuum to 10-5 mbar (only for molybdenum model) including electric pressure transducer and booster pump
• PC control via NCC with enhanced optional documentation and possible connection to customer LAN

When hydrogen is used as a process gas, our systems come equipped with additional safety technology. Only certified and industry proven safety sensors are used. The furnaces are always controlled using a fail-safe controller (S7-300F/safety controller). The controller and documentation are carried out using Nabertherm Control Center NCC (see page 42).

Two Temperature-Dependent Concepts Available for Safe Operation with Hydrogen:

• Partial pressure operation: H2 infeed under controlled negative pressure (partial pressure) in the process reactor starting from 750 °C furnace chamber temperature
• Atmospheric operation: H2-purging of process reactor starting from room temperature at controlled over pressure (50 mbar relative)

Automatic Version VHT for Operation with Hydrogen

• Features as found with automatic version of the VHT without hydrogen operation, plus
• Redundant process gas 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