Laboratory

Hot-Wall Retort Furnaces up to 1100 °C

Retort furnace NRA 150/09 with automatic gas injection and process control H3700 Retort furnace NRA 25/06 with gas supply system

Inside heating in retort furnaces NRA ../06

Bayonet quick-lock for the retort, also with electric drive as additional equipment

Parallel guided door to open the hot retort furnace as additional equipment

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 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 +/- 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
 

Retort furnace NRA 25/09 Retort furnace NRA 50/09 H2

Vacuum pump for cold evacuation of the retort

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 or air-baffle box in the furnace with atmosphere circulation
  • Swivel door hinged on right side with open cooling water system
  • Depending on furnace volume for 950 °C- and 1100 °C-version the control system is divided in one or more heating zones
  • Temperature control as furnace control with temperature measurement outside the retort
  • Gas supply system for one non-flammable protective or reaction gas with flow meter and manual 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 nonflammable 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
  • Cooling system for shortening process times
  • 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
  • Gas inlet with solenoid valve, controlled by the program
  • Process control and documentation via VCD software package or Nabertherm Control Center (NCC) for monitoring, documentation and control
 

Retort furnace NRA 300/09 H2 for heat treatment under hydrogen Charging of the retort furnace NRA 300/06 with a pallet truck
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
 

Retort furnace NR 150/11 IDB with thermal post combustion system

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 purging the furnace chamber with a protective gas. Exhaust gases are burned in an exhaust torch. Both the purging and the torch function are monitored to ensure a safe operation.

  • Process control under monitored and controlled overpressure of 50 mbar relative
  • 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
  • Torch for thermal post combustion of exhaust gases
ModelTmaxModelTmaxWork space dimensions in mmUseful volumeElectrical
 °C °Cwdhin lconnection*
NRA 17/..650 or 950NR 17/111100225350225173-phase
NRA 25/..650 or 950NR 25/111100225500225253-phase
NRA 50/..650 or 950NR 50/111100325475325503-phase
NRA 75/..650 or 950NR 75/111100325700325753-phase
NRA 150/..650 or 950NR 150/1111004507504501503-phase
NRA 200/..650 or 950NR 200/11110045010004502003-phase
NRA 300/..650 or 950NR 300/1111005909005903003-phase
NRA 400/..650 or 950NR 400/11110059012505904003-phase
NRA 500/..650 or 950NR 500/11110072010007205003-phase
NRA 700/..650 or 950NR 700/11110072013507207003-phase
NRA 1000/..650 or 950NR 1000/111100870135087010003-phase
*Please see page 60 for more information about supply voltage
 

Cold-Wall Retort Furnaces up to 2400 °C or up to 3000 °C

Retort furnace SVHT 9/24-W with tungsten heating

Graphite heating module

Cylindrical retort with tungsten heating

Cooling water distribution

Compared with the VHT models (page 54 ff), the retort furnaces of the SVHT product line offer improved performance data with regard to achievable vacuum and maximum temperature. Due to the design as pit-type furnace with tungsten heating, processes up to max. 2400 °C even in high vacuum can be implemented with retort furnaces of the SVHT..-W product line. Retort furnaces of the SVHT..-GR product line with graphite heating, also in pit-type design, can be operated in an inert gas atmosphere even up to max. 3000 °C.

  • Standard sizes with a furnace chamber of 2 or 9 liters
  • Designed as pit-type furnace, charged from above
  • Frame construction with inserted sheets of textured stainless steel
  • Dual shell water-cooled stainless steel container
  • Manual operation of process gas and vacuum functions
  • Manual gas supply for non-combustible process gas
  • A step in front of the retort furnace for an ergonomic charging height
  • Retort lid with gas-charged shock absorbers
  • Controls and switchgear as well as gas supply integrated in furnace housing
  • Defined application within the constraints of the operating instructions
  • NTLog Basic for Nabertherm controller: recording of process data with USB-flash drive
  • Further standard product characteristics see description for standard design of VHT models

Heating Options

SVHT ..-GR

  • Applicable for processes:
    • Under protective or reaction gases or in the vacuum up to 2200 C under consideration of relevant max. temperature limits
    • Under inert gas argon up to 3000 C
  • Max. vacuum up to 10-4 mbar depending on the type of pump used
  • Heating: graphite heating elements in cylindrical arrangement
  • Insulation: graphite felt insulation
  • Temperature measurement by means of an optical pyrometer

SVHT ..-W

  • Applicable for processes under protective or reaction gases or in vacuum up to 2400 °C
  • Max. vacuum up to 10-5 mbar depending on the type of pump used
  • Heating: cylindrical tungsten heating module
  • Insulation: tungsten and molybdenum radiant plates
  • Temperature measurement with thermocouple type C
  • Additional equipment such as automatic process gas control or design for the operation with flammable gases incl. safety system see VHT models
ModelTmaxWork space dimensionsUseful volumeOuter dimensions in mmHeating powerElectrical
 °CØ x h in mmin lWDHin KW1connection*
SVHT 2/24-W2400150 x 1502.5130025002000553-phase
SVHT 9/24-W2400230 x 2309.5140029002100953-phase
         
SVHT 2/30-GR3000150 x 1502.5140025002100653-phase
SVHT 9/30-GR3000230 x 2309.51500290021001153-phase
1Depending on furnace design connected load might be higher *Please see page 60 for more information about supply voltage
 

Cold-Wall Retort Furnaces up to 2400 °C

Retort furnace VHT 500/22-GR H2 with CFC-process box and extension package for operation under hydrogen Retort furnace VHT 100/15-KE H2 with fiber insulation and extension package for operation under hydrogen, 1500 °C

Heat treatment of copper bars under hydrogen in a retort furnace VHT 8/16-MO

The compact retort 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 retort 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

In general the following variants are available wit respect to the process requirements:

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 VHT ../..-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 (see table)
  • Max. vacuum up to 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

Graphite heating chamber

Molybdenum heating chamber

Tungsten heating chamber

Ceramic fiber insulation

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
  • H700 process control with clearly laid out 7“ touchpanel control for program entry and display, 10 programs each with 20 segments
  • Over-temperature limiter with adjustable cutout temperature 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 , Ar or non-flammable forming gas) with adjustable flow
  • Bypass with manual valve for rapid filling or flooding of furnace chamber
  • Manual gas outlet with overflow valve (20 mbar relative) for over-pressure operation
  • 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
  • Defined application within the constraints of the operating instructions
  • NTLog Basic for Nabertherm controller: recording of process data with USB-flash drive

Additional equipment

  • Tmax 2400  °C for VHT 40/..-GR and larger
  • Housing, optionally divisible, for passing through narrow door frames (VHT 8)
  • Manual gas supply for second process gas (N2 , Ar or non-flammable forming gas) with adjustable flow and bypass
  • Inner process box made of molybdenum, tungsten, graphite 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. Generated exhaust gases will be directly lead out the inner process chamber during debinding. The change of gas inlet pathes after debinding results in a cleaned process gas atmosphere during sintering.
  • 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/..-GR and larger)
  • Two-stage rotary vane pump with ball valve for pre-evacuating and heat-treating in a fine vacuum (up to 10 2 mbar)
  • Turbo molecular pump with slide valve for pre-evacuation and for heat treatment in a high vacuum (up to 10 5 mbar) including electric pressure transducer and booster pump
  • Other vacuum pumps on request
  • Heat exchanger with closed-loop cooling water circuit
  • Automation package with process control H3700
    • 12" graphic touch panel
    • 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, Ar or non-flammable 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 relative) for over-pressure operation
    • Transducer for absolute and relative pressure
  • Mass 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)
  • Process control and documentation via VCD software package or Nabertherm Control Center (NCC) for monitoring, documentation and control
 

Retort furnace VHT 8/16‑MO with automation package Retort furnace VHT 40/22-GR with motor-driven lift door and front frame for connection to a glovebox

Single-stage rotary vane pump for heat treatment in a rough vacuum to 5 mbar

Two-stage rotary vane pump for heat treatment in a vacuum to 10-2 mbar

Turbo-molecular pump with booster pump for heat treatment in a vacuum to 10-5 mbar

H2 Version for Operation with Hydrogen or other Reaction Gases

In the H2 version the retort 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 retort furnaces are controlled by a fail-safe PLC control system (S7-300F/safety controller).

  • Certified safety concept
  • Automation package
  • 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
  • Electrically heated or gas-fired 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
  • Inner process hood in the process chamber for debinding under hydrogen
  • Process control and documentation via Nabertherm Control Center (NCC) for monitoring, documentation and control
 

Retort furnace VHT 40/16-MO H2 with hydrogen extension package and process box
Process Box for Debinding in Inert Gas

Certain processes require charges to be debinded in non-flammable protective or reactive gases. For these processes we fundamentally recommend a hot-wall retort furnace (see models NR… or SR…). These retort furnaces can ensure that the formation of condensation will be avoided as throughly as possible.

If there is no way to avoid the escape of small amounts of residual binder during the process, even in the VHT furnace, the retort furnace should be designed to meet this contingency.

The furnace chamber is equipped with an additional process box that has a direct outlet to the exhaust gas torch through which the exhaust gas can be directly vented. This system enables a substantial reduction in the amount of furnace chamber contamination caused by the exhaust gases generated during debinding.

Depending on the exhaust gas composition the exhaust gas line can be designed to include various options.

  • Exhaust gas torch for burning off the exhaust gas
  • Condensation trap for separating out binding agents
  • Exhaust gas post-treatment, depending on the process, via exhaust gas washer
  • Heated exhaust gas outlet to avoid condensation deposits in the exhaust gas line
 VHT .../..-GRVHT .../..-MOVHT .../18-WVHT .../18-KE
Tmax1800 °C or 2200 °C1200 °C or 1600 °C1800 °C1800 °C
Inert gas
Air/Oxygen---
Hydrogen3,4331,3
Rough vacuum and fine vacuum (>10-3 mbar)2
High vacuum (<10-3 mbar)42
Material of heaterGraphiteMolybdenumTungstenMoSi2
Material of insulationGraphite feltMolybdenumTungsten/MolybdenumCeramic fiber
1Tmax reduces to 1400 °C 3Only with safety package for flammable gases
2Depending on Tmax 4Up to 1800 °C
ModelInner dimensions of process box in mmVolume
 wdhin l
VHT 8/..1202101503,5
VHT 40/..25043025025,0
VHT 70/..32547532550,0
VHT 100/..42550042590,0
VHT 250/..575700575230,0
VHT 500/..725850725445,0
ModelInner dimensions in mmVolumeMax. chargeOuter dimensions in mmHeating power in kW4
 wdhin lweight/kgWDHGraphiteMolybdenumTungstenCeramic fiber
VHT 8/..170240200851250 (800)1110020002719/3435012
VHT 40/..300450300403016002100230083/103254/60313030
VHT 70/..3755003757050170025002400105/125270/100315055
VHT 100/..45055045010075190026002500131/155290/1403on request85
VHT 250/..6007506002501753000143003100180/2102on requeston requeston request
VHT 500/..7509007505003503200145003300220/2602on requeston requeston request
1With separated switching system unit 31200 °C/1600 °C
21800 °C/2200 °C 4Depending on furnace design connected load might be higher