How to Detect Gas Leakage in Ion Nitriding Furnace

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Generally, after a long period of wear and tear of the ion nitriding furnace, a certain amount of air leakage will occur. A slight air leak will not affect the normal nitriding quality of the workpiece, and a serious air leak will inevitably affect the quality of the nitriding treatment of the workpiece, and we need to detect the leak location and repair it. The following is the detection method for the leakage of the ion nitriding furnace compiled by the editor.

The leak detection of vacuum equipment generally adopts the method of “segment” inspection, that is, inspections section by section.

Step 1: The ion nitriding furnace body is separated from the gas supply system, the purpose is to distinguish whether the leakage is caused by the furnace body or the gas supply system. Separate the air inlet pipe from the bell, and then seal the air inlet joint (you can use the special plug or vacuum sealing mud provided by me). Start the vacuum pump to evacuate. After pumping to a higher vacuum (such as about 30Pa or higher), close the butterfly valve, pause for a period of time (15-30 minutes), and observe the air leakage of the equipment.

Step 2: After completing the work of the first step, if the ion nitriding furnace body leaks, check each sealing part (including the observation window, gas filling device, sealing flange surface of the lower part of the bell, and the chassis) that may cause leakage one by one The large sealing ring on the upper part, the sealing part of the pressure measurement part, the sealing part of the cathode part, the connecting flange surface between the butterfly valve and the exhaust pipe, etc.), until the ion nitriding furnace body basically does not leak. Note: When implementing the following inspection steps, the principle of “segmented” inspection should be followed, that is, one step is performed one step at a time. After each inspection step is completed, vacuum is used to observe the inspection effect. If the air leakage problem is solved, no more Perform other checks. Otherwise, do the inspections one by one (the inspection steps can be performed out of order)

1. Check whether the glass sight glass of the observation window is broken, if it breaks, it should be replaced.

2. Check whether the hexagon socket screws that fasten the glass sight glass on the observation window are loose. If there is any looseness, they should be tightened, but they must be tightened symmetrically and evenly, and the force should not be excessive to avoid crushing the glass.

3. Check whether the inner and outer sealing rings (white) of the observation window are aging. If they are aging, they need to be replaced with new ones.

4. Remove the automatic inflation device on the base of the ion nitriding furnace body, use a clean rag dipped in gasoline to remove the seal rubber and the ash on the inflatable sealing surface, and reinstall it as it is.

5. Check the sealing condition of the pressure measuring place on the furnace body chassis, tighten the tightening nut if it is loose, and replace the sealing ring if it is damaged.

6. Check the sealing condition of the cathode part. If the tightening nut is loose, tighten it, and replace the sealing ring if it is damaged.

7. Check the sealing flange surface at the bottom of the bell jar of the ion nitriding furnace. If there are rust marks, pits and other damages, they should be dealt with in time. (Note: Every time the bell jar is lifted, it should be placed on a rubber plate, wooden square or other soft support to prevent damage to the sealing flange surface.)

8. Check the large sealing ring on the chassis of the ion nitriding furnace body. If it is damaged, it should be repaired or replaced in time. (Note: Every time after lifting the bell, before putting it on again, use a clean brush to remove the ash on the chassis and the large sealing ring, and then wipe off the sealing flange surface and the sealing flange with a clean rag moistened with gasoline. The ash on the large sealing ring to prevent the ash from being embedded in the large sealing ring and causing air leakage.)

9. Check the tightness of each connecting flange surface of the exhaust hard elbow. If there is looseness, it should be evenly tightened. If the sealing ring is damaged, it should be replaced in time.

10. Check whether there is ash and slag on the inner sealing ring of the butterfly valve. If there is ash and slag, the butterfly valve tube may not die and leak air. If such a situation is found, it should be cleaned up with a clean rag moistened with gasoline in time, and then coated with vacuum grease. Note: When cleaning the butterfly valve sealing ring, do not soak the sealing ring with gasoline, otherwise the sealing ring will expand and the butterfly valve will not be able to switch.

Step 3: After completing the first step, if the ion nitriding furnace body does not leak, it indicates that the sealing parts of the furnace body are intact. Then slowly open the butterfly valve. At this time, the following two situations may occur.

1. The vacuum level drops slightly at the moment of opening the butterfly valve, but does not continue to drop thereafter (that is, the pressure rise rate is within the range specified by the equipment or the pressure rise rate is within the range permitted by the process), which indicates that the stainless steel exhaust gas is soft The pipe, solenoid valve and its connecting parts are intact.

2. If the vacuum continues to drop after opening the butterfly valve, it means that the electromagnetic vacuum is equipped with an inflation valve, the stainless steel corrugated hose or the connection seal at both ends of the hose may be leaking. In this case, you can check for leaks according to the following procedures:

(1) First check the sealing parts at both ends of the bellows. If the sealing flange is loose, it should be evenly tightened. If the sealing ring is damaged, it should be replaced in time.

(2) Then check whether the sealing ring in the solenoid valve is stuck with ash, if there is ash, it may cause air leakage. If such a situation is found, a clean rag dampened with gasoline can be used to clean up the ash.

(3) Finally, check the corrugated hose. The inspection can be carried out by means of sealing and pressurization (pressure is 0.1MPa). After pressurization, the pipe body shall be immersed in water section by section, and the leaking part shall be observed. (Avoid extending the bellows when pressurizing).

Step 4: After completing the first three steps, after solving the gas leakage problem of the ion nitriding furnace body or confirming that the gas leakage is not caused by the furnace body, reconnect the air inlet pipe separated from the ion nitriding furnace body in the first step to On the bell jar of the furnace body (and ensure that the joints are well sealed), turn off the flow meters first, and then start the vacuum pump to vacuum the furnace body. The purpose of this step is to check the gas supply system for leaks. If it is found that the equipment is leaking again, check the air-intake joints, air pipes, and the sealing conditions of each connection of the three-way confluence of various air sources until the air leakage problem is eliminated.

1. Check the sealing condition of the air inlet pipe and the air inlet joint and the outlet joint of the flow meter. If air leakage is suspected, the joint can be sealed with vacuum sealing mud.

2. Check whether the flow meter can be shut down. The solution is to block the inlet end of the flowmeter, and compare the difference between blocking and only closing the flowmeter. If the flowmeter cannot be shut down, it needs to be repaired or replaced.

3. Check whether the ammonia delivery hose is leaking. If it is found to be aging and leaking, it should be replaced. Usually, after completing the above steps of inspection, the gas leakage problem of the ion nitriding furnace body can be solved.

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