Air leakage detection method of vacuum furnace

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The atmosphere in the vacuum furnace will directly affect the surface treatment effect of the product. The atmosphere in the furnace is determined by the air tightness of the vacuum furnace. Therefore, to ensure the quality of the workpiece, the first thing to do is to keep the good air tightness of the vacuum furnace. The difficulty in the air tightness inspection of the vacuum annealing furnace lies in the large area of the furnace body, the complex pipeline, and various parts easy to leak. The inspection of the air tightness should be routine and systematic To change. Next, Luoyang Sigma will introduce the air leakage detection method of vacuum sintering furnace in detail.

1. Determine the key parts of air tightness inspection
These key parts generally include:
1) Replace the parts of the equipment during maintenance. The furnace body and pipe parts that have been moved during maintenance should be taken as the key parts of inspection.
2) Open top cover, bottom cover, threading hole and access door.
3) Inlet seal roll gap.
4) Expansion joints on furnace shell and circulating pipeline, furnace roll flange, heat exchanger flange, instrument flange and welding joint, etc.
5) Water cooled pyrometer, camera, water-cooled heat exchanger, etc.
6) Sampling pipe joint of analyzer, etc.

2. Inspection of positive pressure part
In the normal production process, the annealing furnace should be kept at a micro positive pressure of 150-300pa.

1) Leakage judgment. Observing the data measured by the online oxygen ppm analyzer, when the residual oxygen in a certain section suddenly increases significantly, it may be the furnace shell or circulating pipe leakage.

2) Inspection methods and tools for leakage points. Tool room hydrogen detector. The method is to ensure that the hydrogen in the furnace is more than 3%, and the air tightness of the furnace section is checked by portable hydrogen detector, and the key parts are the top maintenance weld. When the leakage point is detected, the hydrogen detector will alarm.

3. Inspection of negative pressure part
The suction end of the circulating fan is negative pressure. If the negative pressure part leaks, the air will be sucked into the furnace.
1) Leakage judgment. By observing the changes of the data measured by the on-line analyzer, we can judge whether the fan has leakage.

2) Inspection methods and tools for leakage points. The negative pressure leakage point can be checked by changing the negative pressure into positive pressure through the above method, and then the hydrogen detector can be used for inspection, or the helium leak detector, which is specially used for negative pressure leak detection.

4. Leakage point treatment
Annealing furnace is always in working state. For some leakage points, high temperature sealant can be applied for temporary treatment, and thorough treatment shall be conducted after the opportunity of furnace shutdown.

Repair welding shall be carried out on the cracked parts; the aged or damaged sealing gasket and ring shall be replaced; the parts with leakage, such as expansion joint, shall be replaced; the loose bolts shall be tightened; high temperature sealant shall be applied.