Customer said, vacuum drying box vacuum pulled to the required degree of vacuum, after a while the degree of vacuum reduced, replaced the vacuum valve and vacuum tube, or this status quo, how is it?

This indicates that the vacuum drying box is leaking.

The most difficult to detect is the leakage of the tank, need to pour some water inside the box, then shut the door to vacuum, and then flip the box if there are bubbles in a certain position is the leakage point, if conditions with argon arc welding. There are other ways to get rid of the nitrogen in a vacuum furnace, where it is possible to leak. If the foam continues to swell, there will be a gap. The other way is to prepare barrels of washing powder water and syringe, and syringe to wash the laundry powder water where you think it might leak. Observe carefully if there is a bubble point at the injection site. Point is a leak point.

If the door seal is slightly tighter, the vacuum drying chamber as long as the negative pressure to a certain extent is not a problem. First vacuum, see if the negative pressure meter can reach a standard atmospheric pressure, if the needle changes slowly in the process of pumping, try to push the door inside to see if the vacuum can be pumped, if you can vacuum, just rotate the door a few times. If you push the door with your hand, it won't work. It is very likely that the screw that holds the heater on the inner liner is loose and needs to be removed from the back baffle (wear gloves and masks during the removal process, which is uncomfortable when the insulating surface is exposed to the skin with silicate substances) and then find the heating element and tighten the fixing screw again.