Quiet Protocol ( $p < 3500~\textrm{psi}$)

Quiet protocol applies to pressures up to 3500  psi. Within this protocol, the pressure vessel can be operated in a normal manner without a building-wide notification. A pressure of 3500  psi was selected on the basis of results derived in Sec 1.2 (illustrated in Fig 2) together with considerations of typical PTV usage patterns.

• This pressure range will accommodate most of the work that is done in the PTV. A major use of the PTV in the next several years will be to ballast profiling drifters for neutral buoyancy at 2 Km depth (2900 psi). A pressure of 3500  psi will allow the collection of data that brackets the target pressure.

• This pressure is approximately $\frac{1}{3}$ the maximum working pressure of the vessel and $\frac{1}{6}$ of the maximum pressure for which the vessel was designed. The probability of a catastrophic containment failure at these pressures is accordingly unlikely.

• Fig 2 shows that even if the PTV is configured for full volume then the potential energy stored in the compressed water is 18 cap-feet which is approximately $\frac{1}{8}$ of that at 10 kpsi. A pressure of 3500  psi was selected because the ceiling is 18 feet above the top of the PTV.

The PTV operations room should be cleared of people not directly involved. In addition, access to the basement should be restricted by locking the doors to the PTV pit and the test-tank observation room.