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. 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:

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
• Insulation made of mineral wool

Models NRA ../09 with Tmax 950 °C

• Design like models NRA ../06 with following differences:
  • Outside heating with heating elements around the retort
  • Retort made of 1.4828
  • Only fiber materials are used which are not classified as carcinogenic according to TRGS 905, class 1 or 2

Models NR ../11 with Tmax 1100 °C

• Design like models NRA ../09 with following differences:
  • Retort made of 1.4841
  • Without gas-circulation

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 resp. air-baffle box in the furnaces with atmosphere circulation
• Swivel door hinged on right side
• Open cooling water system
• Depending on furnace volume for 950 °C- and 1100 °C-models the control system is divided in one or more heating zones
• Furnace temperature control with measurement outside the retort
• Gas supply system for one non-flammable protective or reaction gas with flow meter and magnetic valve
• Port for vacuum pump for cold evacuation
• Operation under vacuum up to 600 °C with optional single-stage rotary vane pump
• Defined application within the constraints of the operating instructions
• NTLog Basic for Nabertherm controller: recording of process data with USB-flash drive

Additional equipment

• Upgrade for other non-flammable gases, H₂ version for flammable gases
• Automatic gas injection, including MFC flow controller for alternating volume flow, controlled with process control H3700, H1700
• Vacuum pump for evacuating of the retort up to 600 °C, attainable vacuum up to 10^-5 mbar subject to selected pump
• Indirect cooling
• Direct cooling
• Heat exchanger with closed-loop cooling water circuit for door cooling
• Measuring device for residual oxygen content
• Door heating
• Temperature control as charge control with temperature measurement inside and outside the retort
• Retort, made of 2.4633 for Tmax 1150 °C
• Process control and documentation via VCD software package or Nabertherm Control Center (NCC) for monitoring, documentation and control

IDB Version for Debinding under Non-flammable Protective Gases or for Pyrolysis Processes

The retort furnaces of the NR and NRA product line are perfectly suited for debinding under non-flammable protective gases or for pyrolysis processes. The IDB version of the retort furnaces implements a safety concept by controlled inerting the furnace chamber with a protective gas. Exhaust gases are burned in a termal post combustion. Both the purging and the torch function are monitored to ensure a safe operation.

• Process control under monitored overpressure
• Process control H1700 with PLC controls and graphic touch panel for data input
• Monitored gas pre-pressure of the process gas
• Bypass for safe flushing of furnace chamber with inert gas
• Thermal post combustion of exhaust gases

H₂ Version for Operation with Flammable Process Gases

When a flammable process gas like hydrogen is used, the retort 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).

• Supply of flammable process gas at controlled overpressure of 50 mbar relative
• Certified safety concept
• Process control H3700 with PLC controls and graphic touch panel 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
• Torch for thermal post combustion of exhaust gases
• Emergency flood container for purging the furnace in case of failore