It is generally locked because it is a controlled work area. Only specifically trained personnel are allowed to operate the vessel. The vessel operates between 0 and 10,000 psig. It is hydraulically controlled. Items are placed inside the tank and a 3600 pound lid is secured to the top.
Pressure is increased by pumping water into the vessel.
There are 3 levels of use for the vessel. These pressures can be attained any time without any complications. These pressures require that warning be broadcast through the building indicating that the PTV is in use up to 6000 psig. These pressures require a complete evacuation of the building except the PTV controllers. There are red flashing lights at the entrances, and the building is locked down.