Pit type sealed retort furnaces are of a cylindrical design vertically erected with a positive sealing mechanism on top in order to contain and preserve heat and atmosphere during a process cycle. The job or charge is loaded into a retort which functions as the chamber of the furnace and the retort is heated externally electrically. Pit furnaces like these are used in process industries like coal tar processing, separation of titanium and magnesium from ore, and in general engineering and metallurgical applications for carburizing, nitriding, carbonitriding and nitrocarburizing as well as hardening, tempering, annealing etc. . Special processes such as aluminium and titanium heat treatment can also be done. In process industries these furnaces can also be used in high pressure applications with temperatures from 800°C to 1200°C and pressure ranging from 400mm water column to 9 bar. These are often laid in a pit to make most of the space available and charges can be loaded and unloaded easily. These are manufactured considering working controlled atmospheres with inlets for diffusion and distribution of cracked ammonia, hydrogen, LPG, methanol, argon, nitrogen and other process fluids. Thermal Technologies manufactures and sets up complete automated process plants also. Temperature control, fluid dissociation, gas penetration and dosing can all be taken up for automated operation.

Temperature Range :
Upto 1100°C

Standard Applications :
Carburizing, Carbo-Nitriding, Nitriding, Nitro-Carburizing, Annealing

Retort MOC :
AISI 304 / AISI 310 / AISI 316 / AISI 330 / Inconel 600

Insulation :
Vacuum Formed Ceramic Fibre Modules / Ceramic Fibre Blanket & Module / Brick Lining

Heating Media Options :
Electric / Gas Fired / Oil Fired

Heating Elements :
Nichrome Wire / Special Alloy Resistance Heating Wire

Furnace Classification :
Class 2 / Class 3

Instrumentation :
Process Automation Equipment, Thyristor, Programmable Temperature Controller, Temperature Recorder, PLC, SCADA, HMI

pit type annealing

Gas nitriding furnaces or pit type gas nitriding furnaces operate up to a temperature of 650°C are used for surface hardening of components by nitrogen impregnation. Fitted with an atmosphere circulation system and provision for purging ammonia to be cracked for nitriding. Suitable charge fixtures for holding the job / charge can be supplied made of stainless steel. Depending on the furnace capacity ammonia dissociation meter and gas panel with suitable flow control and gas manifolds are fitted. Automatic ammonia dissociation system with real time controls can be given optionally.


Pit type carburizing furnaces operate at ranges up to 1000°C, and are prominently used for layered surface hardening by carbon enrichment. Electric motor driven axial or centrifugal fan is provided for atmosphere agitation. A cracking plate is provided above the fan to facilitate cracking of fluids essential for carburizing. An electro-hydraulic swivelling mechanism is employed to open up the retort chamber for loading and unloading. The atmosphere created can be single fluid based (isopropyl alcohol) or dual fluid based (methanol and acetone) with drip feeding or peristaltic pump / dosing pump for fluid feeding. Heating is generally by indirect electric resistance heating method (the retort is heated directly, externally) or optionally via combustion (gas fired). Process control is by carbon potential (CP) control method. Generally K – Type thermocouple is used for temperature sensing and oxyprobe for CP control.

pit type annealing

Our company has been dedicatedly providing Pit Type Annealing Furnace. This furnace is fitted with its own separate heavy duty oil cooled step down double copper wound transformer manufactured with high grade silicon stamping sheets provided with suitable steps for heat adjustment, fitted in rigid steel body with cooling fins mounted on four wheels with attractive color.



  • Adjustable auxiliary electrodes
  • Internally heated chamber
  • Hassle free installation




  • Metal industry
  • Chemical industry
  • Industrial and commercial use



  • Capacity: 2 Tons

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