This is my prototype version of a vacuum wood drying kiln as described in Joshua Salesin's book Vacuum Kiln Drying for Woodworkers.
I used a 28" long piece of 8" water pipe for the vacuum chamber. The ends of the pipe were cut very square and smoothed. The end cap with the penetrations is 5/16" aluminum tread plate. I made it large enough to be used for a 16" pipe chamber. The "door" is 5/8" cast acrylic. The gaskets are cut from 12' wide neoprene shelf liner from HD. The penetration fittings are all 1/4" NPT threaded and sealed with Teflon tape. The vacuum pump is connected with 1/4"IDx3/8"OD PEC plactic pipe with 3/8" compression fittings with Teflon seals. Hand tightening is all that is necessary. I stripped the outter #14 wire cover, drilled individual 3/32" holes for each wire and silicone caulked them to the aluminum tread plate. I drilled the little holes close enough together so later I can drill and tap for a plastic plug and drill the wire holes in the plastic plug. Inside is wired a regular 2 plug receptacle for the heating pad and whatever. I built a standoff ladder to keep the heat pad from contacting the pipe chamber walls. The pipe chamber sits on a wooden cross rack. This vacuum kiln has held a vaccum of 28" Hg for as much as two days.
Be aware that all vacuum pumps will not pump to a 30" Hg vacuum. Many have specified capabilities less than the 27" Hg necessary for water vaporization at 120 degrees that we are striving to maintain inside the chamber.