Under normal circumstances, operators can master the operation of a vacuum brazing furnace without much experience or training, as long as they strictly follow the operating procedures and properly use the buttons and switches. Accidents usually occur due to equipment malfunctions or component failures. Therefore, it is essential to strengthen the management and maintenance of vacuum brazing furnaces to extend their service life and prevent failures during use.
The main goal of safety management is to ensure that safety measures are functioning properly through correct usage and maintenance. The following safety management of vacuum brazing furnace are proposed for four stages: before, during, after use, and during maintenance.
1. Before Using the Furnace
1.1 Precautions Before Opening the Furnace Door:
Before opening the furnace door, check the internal pressure. The vacuum seal’s integrity can be assessed by the pressure reading. If the pressure inside is lower than atmospheric pressure (105Pa), first release the lock ring and then open the vent valve. Wait until the pressure inside reaches atmospheric pressure before opening the door. If the internal pressure is higher than atmospheric pressure (105Pa), first vent the furnace (dangerous), and wait until the pressure reaches atmospheric pressure before opening the door. When opening the furnace door, place your hand on the handle to prevent the door from opening suddenly and causing injury.
1.2 Pre-operation Check:
Operators should inspect key parts, such as the metal heating tape, vacuum pump, furnace walls, and vacuum pipelines, according to the “Self-Maintenance Checklist.” Special attention should be given to the cooling water circulation system, checking water pressure, flow rate, and the condition of each branch. Periodically check the pressure rise rate of the vacuum system and record the results. While the cooling water system is running, inspect the furnace walls for any moisture, rust, or cracks. Any issues found should be addressed immediately to prevent further damage.
1.3 Effectiveness of Measuring Instruments:
Check that auxiliary measuring instruments, such as temperature controllers, vacuum gauges, pressure gauges, thermocouples, and safety valves, are within the calibration period, connected correctly, and functioning properly.
1.4 Cleanliness of the Furnace and Workpieces:
Before placing workpieces in the furnace, ensure that the furnace’s internal heating tape and insulation screens are clean, free of debris, dust, oil, and water. Workpieces should also be clean, as surface oils and impurities can vaporize at high temperatures, contaminating the furnace and blocking necessary pipes, potentially damaging the equipment. If there is a risk of flux splashing or dripping during the process, place collection plates beneath the materials to prevent flux from falling directly onto the heating tape.
2. During Use
2.1 Operator Responsibilities:
All operators must be certified and trained in the proper operation of the vacuum furnace, including understanding the function of each button and following the operation instructions. Operators should set the process parameters according to the technical requirements, especially the over-temperature alarm threshold. During operation, the operator must monitor the status of valves, water pressure, vacuum level, and furnace temperature, ensuring that there are no abnormalities. Check the vacuum pressure gauge and pressure transmitter data, and ensure that the control cabinet’s indicator lights are normal. Any alarms should be handled promptly.
2.2 Manual Valve Operation Sequence:
When manually operating the system, operators should pay attention to the correct sequence of valve operations. The roots pump can only start when the pressure in the system reaches the allowed starting pressure. Otherwise, it could overload and overheat, causing damage. Before starting the diffusion pump heater, the mechanical pump and pre-valve must first create a vacuum in the diffusion pump chamber. After heating, the furnace’s vent valve cannot be opened until the main valve is closed.
2.3 Monitoring Cooling Water Flow:
During operation, operators should monitor the flow of cooling water through all pipes, particularly the temperature of the diffusion pump cooling water. If the water circuit becomes blocked, the diffusion pump will overheat and lose its functionality, potentially burning out the diffusion pump heater. Normally, the water pressure should fluctuate within the set range; any blockages should be addressed immediately.
3. After Use for safety management of vacuum brazing furnace
3.1 Workpiece Removal:
During cooling, wait until the furnace temperature drops below 200°C before stopping the water and opening the furnace door. The workpieces should then be removed and placed on a loading rack to cool or transported to a storage area using a furnace outside cart. Operators should wear thick gloves to prevent burns. After the workpieces are removed, quickly close the furnace door, re-establish the vacuum, and close the valves, vacuum pump, and control power switches in sequence. Carefully check that all valves, control buttons, and switches are in the correct positions before leaving.
3.2 Long-term Inactivity:
When the furnace is not in use for extended periods, evacuate the gas from the furnace. If the furnace will be unused for a long time, fill it with a protective gas that has a purity of no less than 99.99%. Do not use flammable, explosive, or corrosive gases. Drain the circulating water from the cooling system and periodically change the oil in the mechanical pump and roots pump.
4. Maintenance for safety management of vacuum brazing furnace
Special maintenance and repair work on the vacuum furnace should only be done by experienced personnel or the manufacturer’s service provider to identify and fix faults.
4.1 Replacing Parts:
Be cautious when replacing parts, especially when replacing different model components. Some internal switches of the furnace have interlocking functions, and replacing parts may cause these interlocks to fail.
4.2 Checking Air Tightness:
Air tightness is essential for maintaining the vacuum. When dismantling and reassembling parts, replace seals at the connection points, apply vacuum grease, ensure clean contact surfaces, and check the pressure rise rate of the equipment.
4.3 Installing Thermocouples:
After calibrating thermocouples, check that the model matches the corresponding instrument. The thermocouple should be undamaged, clean, and dry, with securely connected wires. Avoid short-circuiting the thermocouple’s connection or the thermocouple itself. During installation, ensure proper depth and position, and verify the sealing of connections. After installation, closely monitor the thermocouple’s performance during its first use.
To prevent overheating and overpressure accidents in the vacuum brazing furnace, effective daily management and maintenance are essential. Management personnel should first understand the working principles of the equipment, identify safety risks in the structure, analyze abnormal phenomena, and learn from past safety incidents with vacuum equipment. safety management of vacuum brazing furnace should be proposed from both a technical and safety management perspective to prevent equipment failures and ensure the reliability and safety of the furnace.
Vacuum Brazing Furnace
A molybdenum strip vacuum brazing furnace is a specially designed equipment used for brazing in high-temperature vacuum environments, utilizing molybdenum as the main heating element or structural material. This equipment is widely used for welding high-melting-point materials, high-temperature alloys, and dissimilar materials due to its excellent high-temperature performance and vacuum compatibility.
For more details on the vacuum brazing furnace, please click on the image link for the molybdenum strip vacuum brazing furnace.
