I'm new in the vacuum infusion so I have a few questions.
I want to make a composite part and for the female mold I'm gonna use a fire scale diam. 80 cm. depth 14 cm. I had the idea to make a box around in formica so I have a flange to attach the vacuum bag. Can you give me some advice about the position for installing the vacuum and infusion line. Do I place the infusion connector (with or without spiral tube) in the middle of the part or on the flange? For the vacuum line, is a connector enough or better in combination with a spiral tube?

Depends on the shape and size of your part, so pictures would help. But your part is small enough that it isn't really going to matter hugely which way you do it, so don't overthink it. Rough rule of thumb if youre using 6mm feed lines is to try not to feed further than 500mm, otherwise the friction slows the resin down dramatically and your infusion can take a long time and you're more likely to get pinholes.

Easy Composites cover this quite well in their tutorial video:

https://youtu.be/qMPSIKfkdtQ

Hanaldo is spot on (as usual!).  Keeping the distance to a sensible level will help.  The shape is also a big factor in terms of where the resin is likely to flow.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

That was my idea about installing the lines, but I don't know if that make sense...

I would increase the amount of spiral around the resin feed to make a nice U shape going at least half way across the mould. You don't normally need spiral on the vacuum side as long as the vacuum port is on the edge of the cloth and peel ply.  As per the video you could even make a resin break. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

I would probably feed from the centre on this part and use spiral tubing around the complete diameter of the mould as your vacuum manifold (with a good 2" resin break). This will be the fastest way to infuse, and give you the best chance of getting a 100% pinhole free surface.

The catch is that if your layup is going to be very thin (ie, under 1.5mm thick), then you will get print through of the resin inlet onto the surface of the part.