These gastight 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 gastight 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 debinding 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 ΔT 6 K inside the working chamber from 100 °C - 600 °C
• 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 surrounding the retort as well as an additional door heater
• Temperature uniformity up to ΔT 6 K inside the working chamber from 200 °C - 900 °C
• Retort made of 1.4841
• Gas circulation fan in the back of the retort provides for optimal temperature uniformity

Models NR …/11 with Tmax 1100 °C

• Outside heating with heating elements surrounding the retort as well as an additional door heater
• Temperature uniformity up to ΔT 20 K inside the working chamber from 200 °C - 1050 °C
• Retort made of 1.4841

Standard Equipment for all models

Basic version

• Compact housing in frame design with removable stainless steel sheets
• Controls and gas supply integrated in the furnace housing
• Welded charging supports in the retort
• Swivel door hinged on right side with open cooling water system
• Multi-zone control, divided between furnace chamber and door. Depending on furnace dimensions, chamber also divided into one or more heating zones
• Gas supply system for one nonflammable protective gas with flow meter and solenoid valve, switchable via the control system
• Operation under vacuum up to 600 °C with optional single-stage rotary vane pump (not for models NRA ../06)
• Port for vacuum pump for cold evacuation
• PLC controls with touch panel H 700 for data input

Additional equipment

• Upgrade for other nonflammable gases
• Automatic gas injection, including MFC flow controller for alternating volume flow, PLC controlled with touch panel H 3700
• Temperature control as charge control with temperature measurement inside and outside the retort
• Vacuum pump for evacuating of the retort up to 600 °C, attainable vacuum up to 10-5 mbar subject to selected pump
• Cooling system for shortening process times
• Heat exchanger with closed-loop cooling water circuit for door cooling

When hydrogen is used as a process gas, the furnace is additionally equipped with the required safety technology. Only certified and industry proven safety sensors are used. The furnace is controlled by a fail-safe PLC control system (S7- 300F/safety controller).

• H2 supply at controlled overpressure of 50 mbar relative
• Certified safety concept
• PLC controls with graphic touch panel H 3700 for data input
• Redundant gas inlet valves for hydrogen
• Monitored pre-pressures of all process gases
• Bypass for safe flushing of furnace chamber with inert gas
• Exhaust gas torch for H2 afterburning
• Emergency flood container for purging the furnace in case of failore

• Process control under monitored and controlled overpressure of 50 mbar relative
• Certified safety concept
• PLC controls with graphic touch panel H 1700 for data input
• Monitored gas pre-pressure of the process gas
• Bypass for safe flushing of furnace chamber with inert gas
• Exhaust gas torch for H2 afterburning

Certain debinding processes under protective gas can also be realized in a chamber or bogie hearth furnace with inserted gas box as a cost-effective alternative. In our state-of-the-art test center we would be glad to make tests in order to select the most suitable furnace model.

The pit-type retort furnaces SR and SRA (with gas circulation) are designed for operation with protective or reaction gases. The furnace is loaded from above by crane or other lifting equipment provided by the customer. In this way, even large charge weights can be loaded into the furnace chamber. The SR furnaces are available in different versions.

Depending on the temperature range in which the furnace be used, the following models are available:

Models SR .../11 with Tmax 1100 °C

• Four-side heating outside the retort
• Temperature uniformity up to ΔT 14K within the working chamber of 500 °C - 1100 °C
• Retort made of 1.4841
• Top down multi-zone control of the furnace heating

Models SRA ../09 with Tmax 950 °C

• Design like models SR…/11 with following differences:
  • Atmosphere circulation with powerful fan in the furnace lid provides for perfect temperature uniformity of up to ΔT 8 K within the working chamber of 200 C - 900 C

Standard Equipment (all models)

• Design like standard equipment of models NR and NRA with following differences:
  • Charging from above with crane or other lifting equipment from customer
  • Hinged lid with opening to the side and with cooling water
  • Multi-zone control of the furnace heating from the top down

• Additional equipment, see models NR and NRA
• H2 version for operation under hydrogen, see models NR and NRA
• IDB version for debinding under protective gas or for pyrolysis processes, see models NR and NRA

The compact furnaces of the VHT product line are available as electrically heated chamber furnaces with graphite, molybdenum or MoSi 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 nonflammable protective 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.

For debinding applications under vacuum, we recommend the VDB version, which besides the corresponding safety technology has an additional debinding retort in the heating chamber and prevents the exhaust gases from contaminating the furnace chamber. The exhaust gases are channelled from the debinding retort into the exhaust gas torch.

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
• Max. vacuum up to 10-2 mbar depending on pump type used
• Graphite felt insulation
• Temperature measurement using type B thermocouple (version to 1800 °C)
• Temperature measurement using optical pyrometer (version to 2200 °C)

VHT ../MO with Molybdenum Insulation and Heating

• Suitable for high-purity processes under protective and reaction gases or under high vacuum
• Tmax 1600 °C
• Max. vacuum up to 5 x10-5 mbar depending on pump type used
• Insulation made of Molybdenum steel sheets
• Temperature measurement by thermocouple type B

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
• Temperature measurement by thermocouple type B

Basic version

• 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
• 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 limit controller 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

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
• 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
• Temperature measurement at 2200 °C with pyrometer and thermocouple, type S with automatic pull-out device for precise control results in the low temperature range
• 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)
• 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 or argon) 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

In the H2 version the furnaces of the VHT…/MO or VHT…/GR product line 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)

Additional equipment

• Partial pressure operation: H2 flushing at underpressure in the process reactor starting from 750 °C furnace chamber temperature
• Retort in the process chamber for debinding under hydrogen

Certain processes require debinding under protective gases or in vacuum. For these processes the models VHT…/MO-VDB or VHT…/GR-VDB are perfectly suited. They are equipped with the necessary safety technology for debinding. The furnace chamber has an additional debinding retort with a direct discharge into the exhaust gas torch. This system ensures that exhaust gases during debinding do not get into and contaminate the furnace chamber.

• Adapted safety concept for debinding
• Automation package (see additional equipment above)
• Exhaust gas torch for burning the exhaust gases
• Debinding retort in the furnace chamber with direct discharge of the exhaust gases into the exhaust gas torch
• Bypass for safe flushing of furnace chamber with inert gas
• Dry-running vacuum pump

Additional equipment

• Condensate trap for separation of large binder volumes during vacuum debinding
• Heated exhaust gas discharge to prevent condensate deposits in the exhaust gas section
• Exhaust gas treatment depending on the process with binder trap, washer or exhaust gas torch

The chamber ovens NRA 40/02 CDB and NRA 150/02 CDB are specially developed for debinding of ceramics and metallic powder injection molded parts according to the BASF CATAMOLD®-method. They are equipped with a gastight retort with inside heating and air circulation. During catalytic debinding, the polyacetal-containing (POM) binder chemically decomposes in the oven under nitric acid and is carried out of the oven by a nitrogen carrier gas and burned in an exhaust gas torch. Both furnaces have a comprehensive safety package to protect the operator and the surrounding. Model NRA 40/02 CDB is very compact and excels with its excellent cost-performance ratio. This model is pefectly suited for repeating lab processes and in production. As a professional production furnace, model NRA 150/02 CDB is also designed for frequent charge changes. The furnace has an automatic torch control that detects the end of the process measuring the torch temperature.

• Tmax 200 °C
• Process retort made of acid-resistant stainless steel 1.4571 with large swiveling door
• Four-side heating inside the retort through chromium steel tube heating elements for good temperature uniformity
• Horizontal air circulation for uniform distribution of the process gas
• Acid pump and acid vessel (to be provided by the customer) accommodated in the furnace frame
• Gas-heated exhaust gas torch with flame monitoring
• Non-wearing ceramic cup for uniform evaporation of the nitric acid

Version NRA 40/02 CDB

• Gas supply system with fixed values
• Safety package provides for safe shut-down and floods of the furnace with nitrogen in case of a failure
• Controller P 300 for setting the temperature curve

Version NRA 150/02 CDB

• Extensive safety package with redundantly operating safety PLC for safe operation with nitric acid
• Automatic gas supply system for nitrogen with mass flow controller
• Large, graphic touch panel H 3700 for entering data and for process visualization
• Adjustable acid volume and correspondingly adjusted gas spply volumes

Additional equipment

• Scale for the nitric acid vessel, connected to the PLC monitors the acid consumption and visualizes the fill level of the acid vessel (NRA 150/02 CDB)
• NCC software package for visualization, control and charge documentation of the process (NRA 150/02 CDB)
• Lift truck for easy loading of the furnace