vacuum brazing furnace maintenance plan

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The helium mass spectrometer leak detector is used to carry out the leak detection process with the following maintenance plan:

(1) check whether the vacuum instrument of vacuum brazing furnace is within the scope of validity, and check whether there is air leakage in the installation of vacuum gauge.

(2) maintenance plan of slide valve pump in vacuum system of vacuum brazing furnace: check the internal parts of slide valve pump for wear, whether the seal ring of shaft head of slide valve pump leaks oil, whether the exhaust valve plate of exhaust device is sealed, whether the vacuum oil pipeline is polluted, and test the limit vacuum degree of slide valve pump.

(3) maintenance plan of roots pump for vacuum system of vacuum brazing furnace: check the gap between rotor and rotor, between rotor and inner wall of pump chamber, check wear condition of gear and bearing, seal ring of shaft head of roots pump, whether lubricating oil at both ends of roots pump is polluted, and test limit vacuum degree of roots pump.

(4) leak detection shall be carried out for the pipeline seal connecting the slide valve pump, roots pump and diffusion pump, for the seal of the front stage valve stem, and for the sealing of the explosion-proof device, so as to ensure that there is no air leakage at the above sealing points.

(5) maintenance plan of diffusion pump in vacuum system of vacuum brazing furnace: check whether the position and clearance of nozzles at all levels of pump core are correct, whether the heating power of pump and cooling effect of pump are normal, whether diffusion pump oil is oxidized and whether oil quantity of diffusion pump meets requirements. Leak detection shall be carried out on the diffusion pump and its connecting pipes and valves, vacuum measuring points, cold well and other sealing positions. Leak detection for diffusion pump is carried out because after the diffusion pump oil is heated to the working temperature, the diffusion pump oil will decompose into hydrogen (H2) and hydrocarbons (CH4, C2H6), etc. when the amount of air infiltrated through the leakage hole reaches a certain amount, these decomposition products will react with oxygen in the air, which will produce deflagration, which will not only hurt people but also damage equipment. Test the limiting vacuum degree of diffusion pump. Check the temperature and flow of inlet and outlet water of diffusion pump of vacuum brazing furnace. In many units, the cooling effect of diffusion pump is not good due to the scale of cooling water, and the vacuum degree can not meet the requirements of technical indicators. Water chillers can also be added.

(6) maintenance scheme for external leakage parts of furnace body: leak detection shall be carried out for furnace door seal, main valve stem seal, pneumatic ball valve stem seal, vent valve spool seal, explosion-proof valve core seal, pre extraction valve stem seal, thermocouple seal and heating electrode seal.

(7) maintenance plan for internal outgassing of vacuum brazing furnace body:
① The gas adsorbed in the furnace is released by heating properly inside the furnace body.
② At the same time, argon and nitrogen are filled into the furnace body to make part of volatile matter and adsorption gas be pumped away along with argon and nitrogen.
③ Then the inner wall of the furnace body is scrubbed with alcohol to remove the adsorbate and reduce the amount of outgassing.
④ Vacuum the furnace chamber for a long time to minimize the outgassing on the furnace surface.

(8) inspection scheme for water leakage in the interlayer of furnace chamber (including the interlayer of furnace door) and the pipeline of gas cooling system: during the long-term use of cooling circulating water, impurities in the water are adsorbed on the inner surface of interlayer and water pipe, and the welding joints of interlayer and water pipe are corroded and prone to water leakage. In the absence of water, these impurities will block the micro leakage. When the vacuum brazing furnace is working, under the double effects of high temperature and pressure difference (there is water pressure in the interlayer and water pipe of the furnace body, and the furnace body is in a vacuum state), the micro leakage will produce micro water seepage. The inspection scheme is as follows: blow the water in the furnace interlayer and water pipe with compressed air, connect it to the water inlet or outlet of the furnace interlayer and cooling water pipe with a vacuum pump, and vacuum the furnace interlayer and water cooling pipe, so as to detect the leakage of the furnace interlayer and water pipe.

(9) inspection scheme for internal leakage of pre extraction valve and inflation group valve body:
① Leak detection was carried out on the inside of the pre extraction valve body.
② The charging group valve is composed of charging valve, make-up valve and partial pressure group valve (pressure reducing valve, fine-tuning valve and solenoid valve). Check the connection structure of charging group valve and manual ball valve. Inspection scheme for internal leakage of charging valve: close the manual ball valve on the charging gas path, and pump out the argon between the manual ball valve and the charging group valve with a vacuum pump to form a vacuum state, that is, no argon leaks into the furnace through the internal parts of the pressure divider valve, make-up valve or charging valve. Then vacuum the furnace and test whether the leakage rate of the vacuum brazing furnace is qualified, which can show whether there is a valve leakage problem among the partial pressure valve, the make-up valve and the charging valve. The judgment scheme is as follows: seal two valves of the partial pressure valve, the make-up valve and the inflation valve, and test whether the other valve leaks by testing whether the leakage rate of the vacuum brazing furnace is qualified. The partial pressure valve, the make-up valve and the inflation valve are detected one by one, and the specific valve leakage is determined finally.

(10) the purity (oxygen content and water content) of argon and nitrogen is more than 5ppm, which is unqualified, which will also affect the quality of vacuum brazing products. The purity of bottled argon was detected by special dew point meter and micro oxygen analyzer. Leak detection shall be carried out for the storage tank, pipeline and valve of argon gas to ensure that these parts do not leak. The special dew point meter and micro oxygen meter are used to detect the purity of argon in the gas tank at all times, so that the purity of argon filled into the furnace chamber can meet the technical requirements of oxygen content and water content not exceeding 5ppm.