Cautions for Daily Use of Vacuum Furnace

After repairing the vacuum oven, vacuum leak detection must be carried out for oven drying. Before drying the vacuum oven, the insulation of the vacuum oven can be checked with 1000V rocker gauge, which is not less than 2MOhm normally. Vacuum oven drying can be divided into three stages: 1. Water discharging period (O-200 C) is the period of water discharging from insulation layer of vacuum oven and moisture discharging from vacuum oven body. Vacuum degree of vacuum oven must be checked, while holding time is long. (2) Temperature zone with large bleeding capacity of vacuum furnace body is generally around 500 (?) C. Because of large bleeding capacity of vacuum furnace, the temperature rise will not exceed 50 (?) C/h at this time. Insulation time is generally more than 60 minutes. (3) Insulation period is about 1200 C. When heating is increased by 100-200 C, it is necessary to keep the insulation for a period of time. Insulation layer is easily damaged if heating is too fast and exhaust of vacuum furnace is incomplete. (1) Prepare operation regulations for use and maintenance of vacuum furnaces, establish operation records and repair files of vacuum furnaces, count accumulated operation time, strengthen routine maintenance of vacuum furnaces, master change trend of technical status of equipment, find fault and damage early, avoid repair which belongs to emergency repair, and prepare parts for repair of vacuum furnaces in advance according to work load and operation conditions of vacuum furnaces. Prepare operation and maintenance plan of vacuum furnace. For example, the service life of heating elements in vacuum furnace is related to many factors, such as operating temperature, product medium in vacuum furnace, product quantity and operation condition. Under the condition of 24 hours processing and production every day, the replacement of heating elements and heat shield in vacuum furnace is carried out every two or three years. This depends on the type and use times of brazing work. Vacuum furnace leaks frequently in spring and autumn. Vacuum furnace leaks easily when long-term idle vacuum furnace is only used again. Vacuum leak detection must be carried out at this time. Vacuum leak detection usually takes the pressure rise rate once a month (at normal temperature, close all vacuum valves, stop the operation of vacuum system, read one value after 1Omin and one value after 1h, the difference between the two numbers is the value of pressure rise rate). To master the trend of equipment leak change, such as vacuum equipment shutdown continuously for one week, run empty once (oven drying). In vacuum system leak detection, in addition to vacuum paste plugging for temporary emergency maintenance, helium mass spectrometer can be used for vacuum leak detection by helium mass spectrometer. If there is no helium mass spectrometer, acetone or ether can be sucked into suspected leak point by medical needle tube, and the reading of vacuum meter can be observed for any change. It is also possible to fabricate blind plates with holes for vacuum silicon tubes and block vacuum pipelines in stages for leakage detection. After finding the leak point, repair it (generally the seal ring is aging more). Check the sliding valve pump, Roots pump, maintenance pump and diffusion pump oil of vacuum furnace regularly. If the oil meets water emulsification and the vacuum drops, the above four pump oils must be replaced. The oil level and quality should be checked once a week. The diffuser pump oil diffuser pump has carbon deposits which can be cleaned by chemical pickling. (2) After repairing the vacuum furnace, check the temperature of the vacuum furnace gauge and the actual temperature of the furnace regularly (check and calibrate the vacuum meter, temperature controller, thermocouple, voltmeter and ammeter regularly) and check whether the three-phase heater is damaged by overheating, uneven temperature or white. For three-phase high-temperature vacuum furnaces and vacuum resistance furnaces with capacity exceeding 100kW, ammeters should be installed in each phase and each heating area. If the temperature of vacuum furnaces and meters indicate abnormal, analysis and treatment should be carried out in time.