The plug door, pictured at left and directly below, was manufactured by Comecer SpA of Castel Bolonese, Italy. The door was shipped from the manufactured as the door and the rails, controls, and inner and outer frames. The door was shipped hollow and weighed 4 tons. It was backfilled with 3 cubic yards of concrete during the Cyclotron Facility construction achieving a final weight of 16 tons. The door is approximately 2.2 meters (7’ 2.6”) thick. The door travels on stainless steel rails that are set into the concrete. The rails were placed before the floor outside of the vault was poured.
The picture at the left shows the rails set in the floor of the vault. It can also be seen the re-bar that was used in the walls. The formwork is set on the outside of the vault but not yet on the inside. The frame included four 25 mm diameter conduits that provided pathways for the wiring to go from the inside of the vault to the outside and the control cabinet.
The plug door followed the same vertical insertion path through the tunnels as the cyclotron itself. Door heights and widths were repeatedly checked but as can be seen in the photograph on the left, the plug door fit through the double doors when placed on the door’s “face.” While clearance was tight, careful maneuvering by the riggers allow the door to enter the construction site.
Once the plug door was inside the construction site, an A-frame and block and tackles were used to set the door upright and place it on its rails. The photograph shows the front and rear wheels at the bottom edge of the picture. One of the rear wheels has a toothed cog attached to it. That cog is connected to a motorized gear drive. The motor, gears, and chains are all covered by a stainless steel housing. Electrical connections are provided by the articulated cable way up near the ceiling. In the event of an emergency, such as a loss of power, a hand crank can be placed onto the motor shaft and the door can be cranked open (albeit at a slow pace and with a lot of cranking).
This final picture is the view of the plug door on its rails after being set upright. The white nylon frame fits into a stainless steel frame that is bolted to the inside wall of the vault. When the door closes and reaches its final “in” position, a gasket inflates and seals against the white frame. This allows the vault to become very negatively pressurized as a safety measure.