With the help from Chub, we opened the vacuum chamber. The procedures are not complicated. Here are some notes, both about the opening procedures and some other things I learned from Chub.
1) Vent the chamber by opening the venting valve slightly. The venting process needs to be slow - we cover it with a wipe, as shown in the photo 1. We stop opening the valve when we hear the air wheezing.
2) The thing with a screen is a gauge, which gives the pressure inside, but it is not quite working - always showing atmosphere pressure. Chub left me a document on it; I should be able to get it working.
3) We removed the screws of the top chamber. Correct hex keys is necessary - I was going to use one that loosely fits but Chub said it is not good.
4) We lifted the cover of the chamber with the crane and put it besides the chamber. We should release the break of the crane first and then break it again when we land the weight.
5) The pump connection is not very good - leaking oil both into the chamber and onto the floor.
6) The surface under the chamber (shown in photo 2) cover can only be cleaned by dry wipe or alcohol.
Next I am going to set up the optics, electronics and whatever inside before we close it and pump it down.