Go to Kurt J. Lesker Company's Web page http://www.lesker.com They have all sorts of vacuum hardware, materials, etc. along with pricing, drawings and so forth. The brass inline valves are at http://www.lesker.com/CFDOCS/newweb/FrameSets/Frameset_Vacuum_Valves.cfm
Note that there are two types, marked "disk" and "o-ring." The former use a disk of viton as the elastomer. The latter have an o-ring that is captured in a groove. The only real difference is the amount of elastomer that is exposed to vacuum.
KJL sells internationally and you may have someone in Italy.
Vacuum surplus companies often have these valves for 1/2 to 1/3 or the new list. If they are cutouts, you'll have to use an oxy torch to remove the (usually) silver brazed tubing. As I said before, I like the low melting Sn-Ag solder as it's easy to use and rework.
Brass valves come in in-line and right angle versions.
On elastomers and vacuum, all elastomers are permeable to gases and they do absorb moisture. In all cases you should try to minimize the amount of elastomer that is exposed to the vacuum environment. Another difference is whether the elastomer separates the vacuum from the outside world (external seal) or whether they are completely contained within the vacuum environment. In the latter case, they will outgas for a while but eventually they will be as good as anything else, assuming the vapor pressure properties are acceptable for your pressure/temperature range.
Teflon is a great material: low water uptake, good temp capabilities and low vapor pressure. Teflon is often used in UHV applications.
Nylon and delrin both take up a fair amount of water so you have to outgas a long time.
Polycarbonates are good but also take up a reasonable amount of water. Polyimides are real water sponges but outgas well and have extremely low vapor pressures. You will often see polyimides in UHV.
Steve
Created on Saturday, March 03, 2001 8:35 AM EDT by Steve Hansen