Common optional special atmospheres and ultra-high vacuum (details as follows):

1. Inert atmosphere control system for vacuum box furnace
2. Optional reaction atmospheres (H2, CO, CO2, H2S, H2O, CH4&C2H4, and other atmospheres)
3. vacuum pump
4. Voltage division options
5. Tail gas combustion torch (pyrolysis, catalysis or supported by propane gas) optional
6. Metal atmosphere box in standard furnace for controlled atmosphere environment
7. Silicon carbide lining plate used to protect heating elements in standard box furnaces

1. Inert atmosphere control system for vacuum box furnace

GLO, LHT, HTK, HBO, HTBL, and V-L vacuum furnaces come standard with a fully inert atmosphere control system. Based on size and maximum operating temperature, semi-automatic control systems with flow meters and fully automatic PLC control systems with touch screens and mass flow meters can be provided.

All vacuum furnaces come standard with an inert atmosphere control device. More atmosphere control devices can be configured.

All vacuum furnaces are available with a full range of vacuum pumps such as rotary vane pumps, Roots pumps, diffusion pumps, and turbo pumps. In some cases, a vacuum pump must be configured for safe use of the furnace.

2. Optional reaction atmospheres (H2, CO, CO2, H2S, H2O, CH4&C2H4, and other atmospheres)

All vacuum furnaces can be safely configured with atmospheres such as H₂、 CO、CO₂、 H₂S、H₂O、CH₄、 C₂H₄.

In principle, a vacuum furnace with a reaction atmosphere needs to be equipped with a fully automatic control system, and the relevant configurations are as follows:

• Siemens S7-300 control system with optional TP1900 or WinCC panel
• The installation of inert atmospheres such as nitrogen and argon can be controlled by a mass flow meter
• The installation of the reaction atmosphere can be controlled by a mass flow meter
• Reaction atmosphere sensor
• Catalytic tail gas combustion torch ensures safe combustion
• Safe flushing tank
• Safety components meet SIL 2 standards

For safety reasons, the muffle furnace gas path system using inert and reactive atmospheres needs to be designed according to the EN 746-3 standard. This standard requires that oxygen in the furnace be purged before heating and introducing combustible gases. In addition, all security status can be monitored. In emergency situations, it is necessary to use inert gas in the flushing tank to blow the furnace.

3. Vacuum pump

There are 4 different vacuum pumps to choose from, achieving different levels of vacuum. The final vacuum degree can be certified through the PNEUROP standard testing method; At the same time, the pressure of the flange in the closed state of the pump can be measured. After configuring the vacuum pump, the final vacuum level reached by the muffle furnace system, as well as the time to reach the corresponding vacuum level, are influenced by multiple factors, including the customer's sample material, cleanliness, desorption rate of the furnace surface, exhaust of samples or other materials placed in the furnace, and leakage rate of the vacuum furnace and oven.
Before leaving the factory, Cabolet Gallo will measure the leakage rate of the vacuum box furnace. Carefully select seals to ensure the lowest possible desorption rate. Vacuum equipment needs to be cleaned before assembly. Uncontrollable factors include sample exhaust, laboratory cleanliness, and air humidity. However, the vacuum system we designed can achieve the required working vacuum level within the time specified by the customer in a clean, dry, cooled, and empty furnace. In addition, an inert atmosphere is required to blow the high vacuum furnace chamber. Try to shorten the opening time of the furnace door as much as possible to prevent air from entering the furnace and causing pollution.

A turbo molecular pump consists of rapidly rotating blades and a stator. The rotational speed can exceed 90000 revolutions per minute. By using a high-speed rotating impeller to transfer momentum to gas molecules, the gas is directed to flow and extract air. Combined with a pre vacuum pump, a higher vacuum degree or high vacuum degree can be achieved. For achieving high or ultra-high vacuum, turbo molecular pumps are currently the most convenient vacuum pumps to use. Slow moving heavy particles or molecules will be pulled out of the furnace faster than faster moving light particles.
There are no moving parts inside the oil diffusion pump. Oil diffusion pump uses high-speed oil vapor flow to remove gas and achieve the purpose of extracting air molecules. At the bottom of the pump, the oil is heated into steam and sprayed out from the gaps of the pump nozzle at a very high speed. After condensation, the oil can be reheated and vaporized. The oil diffusion pump can quickly achieve high vacuum, although some oil molecules may remain in the furnace.

Roots pumps are suitable for heat treatment in precision vacuum environments. The suction chamber does not require oil lubrication. The two wheels move relative to each other, and the wheel structure is precise, with almost no gap before the cavity. It needs to be used in conjunction with a pre vacuum pump.

Rotary vane pump is a pre vacuum pump. This is the most commonly used vacuum pump. Can be used individually or together with two. Can be used in an air atmosphere, with a speed of approximately 1500 revolutions per minute. The suction chamber requires oil lubrication. Bipolar pumps can achieve rough vacuum.

Provide special vacuum systems according to user requirements. For example, if it is necessary to evacuate the reaction atmosphere, these applications require that the vacuum system should not contain lubricating oil or special lubricating oil. Some special vacuum pumps, such as diaphragm pumps, cryogenic pumps, and ion aspiration pumps, can be provided.

4. Voltage division options

The definition of partial pressure is the stable pressure inside the furnace that is lower than atmospheric pressure and there is a continuous airflow. For partial pressure, a mass flow controller, Siemens PLC, and adjustable outlet valve must be equipped. The operator can set the gas flow rate and pressure through the PLC. The mass flow controller controls the gas flow rate. The pneumatic valve in front of the secondary rotary vane pump is used to maintain the required vacuum pressure inside the furnace. The pressure can be set between 10 and 1000 mbar. According to the requirements, other types of vacuum pumps can be used for partial pressure control to obtain lower partial pressure values. Generally, single-stage or two-stage rotary vane pumps are used for gas partial pressure control.

Schematic diagram of voltage divider device with automatic control system. This software can adjust the opening angle of the pneumatic ball valve to maintain a constant vacuum pressure during the heat treatment process. The operator can set the pressure and gas flow rate separately through the PLC.

5. Tail gas combustion torch (pyrolysis, catalysis, or supported by propane gas) optional

Most furnaces can choose from multiple types of exhaust burner solutions. The safest exhaust gas treatment for vacuum chamber furnaces is a combustion torch with methane or propane flames. We suggest using a heated exhaust pipe between the furnace and the torch to prevent organic waste gas from condensing in the pipeline. It can reduce the maintenance time of exhaust gas pipelines and improve production efficiency.

6. The metal atmosphere box inside the standard furnace is used for controlled atmosphere environment

For non airtight chamber furnaces, if an inert atmosphere is required, an air inlet can be provided to introduce inert gas into the furnace, but it will not reach low oxygen levels. On a standard HTMA oven with a maximum temperature of 700 ° C, the oxygen content can be reduced to 50 ppm.

The oven has an airtight fully welded inner cavity, two float flow meters, and a one-way exhaust valve. At atmospheric pressure, the maximum temperature can reach 1150 ° C, providing a gas tight metal atmosphere box for standard CWF and GPC chamber furnaces. Seal the hot spot through the front opening, and the gas inlet and outlet are located on the front of the atmosphere box. The oxygen content can be as low as 30 ppm. The atmosphere box must be ordered together with the box furnace, as the box furnace needs to be modified and can also be used separately without venting the atmosphere box.

Another type of metal atmosphere box has a shallow movable top cover located in a sand seal at the top of the deep base, which can be used for standard CWF and GPC furnaces. The gas inlet/outlet connection for front-end installation passes through the slot on the furnace door. The atmosphere box must be ordered together with the box furnace, as the box furnace needs to be modified and can also be used separately without venting the atmosphere box.

7. Silicon carbide lining plate used to protect heating elements in standard box furnaces

The following figure shows the silicon carbide lining plate in a standard furnace to protect the heating element from volatile atmosphere contamination in the sample.