(a) NAVSEA S9086-DA-STM-000 - NSTM Chapter 100 (Hull Structures)



(d) NAVSEAINST C9094.2 - Submarine Valve Operation Requirements for Builders and Post Overhaul Sea Trial Test Dives

9.1 PURPOSE. To provide TYCOM policy with respect to the maximum allowable operating depths during trials, evolutions to be performed at the various depths, and the prescribed maximum water depth applicable in each case.

9.1.1 Background. Some deep diving submarines are limited to depths less than designed test depth pending accomplishment of certain hull and system modifications prescribed by NAVSEA as necessary to permit certification to design test depth. As these modifications are accomplished during the availability, the integrity of the ships will be certified and they will be permitted to operate down to their design test depth either periodically or without restriction.

a. The sequence of events leading to authorization for operations at the maximum operating depth during post industrial availability or new construction trials for SUBSAFE ships is as follows:

(1) Upon completion of the authorized industrial facility work, NAVSEA reviews the scope, degree and manner of accomplishment and recommends to the TYCOM that the submarine be authorized to test hull strength and integrity at an appropriate maximum keel depth during trials. This depth may be the designed test depth or a lesser depth.

(2) Based on this recommendation the TYCOM will normally authorize operation to the NAVSEA recommended keel depth by message to the ship, information to the applicable ISIC, Supervising Authority/Industrial Activity (as applicable), NAVSEA, Fleet Commander In Chief and CNO.

b. In every instance where the maximum authorized operating depth is exceeded, a report shall be made in accordance with reference (a). In addition to those addressees listed in reference (a), an information copy shall be provided to the applicable TYCOM and ISIC.

9.2 INITIAL TIGHTNESS DIVE. The initial tightness dive following an industrial availability or new construction will be conducted in accordance with carefully planned procedures.

a. The initial tightness dive will be an especially deliberate, planned, step-by-step evolution using conservative angles and moderate speed, or slower, in accordance with the approved Sea Trial Agenda. Caution is required not only because the material condition of the ship is untested at design test depth following major industrial facility work, but also because of the crew's lack of recent submerged operational experience. Reference (b) or (c) applies.

b. The maximum water depth allowable during the initial tightness dive will be 400 feet as specified by reference (b) or (c), as applicable. The approved Sea Trial Agenda and reference (d) describe those events to be conducted during the initial tightness dive and provide the requirements of the initial tightness dive. The approved Sea Trial Agenda also describes those events immediately following the initial tightness dive. The maximum operating keel depth will be 200 feet.

9.3 DEEP DIVE/CONTROLLED DIVE. After demonstrating satisfactory hull strength and integrity during the initial tightness dive, the requirement exists to test the hull at submerged depths down to the maximum operating depth. The first approach to these depths subsequent to the repair of major hull or sea connected systems work will be made in accordance with the following paragraphs.

9.3.1 Depth Limitations. The Deep Dive/Controlled Dive shall be made to the maximum operating depth in water specifically designated for such trials and under specific water depth restrictions in accordance with reference (b) or (c), as applicable, and as promulgated in the appropriate TYCOM/ISIC Operation Order.

9.3.2 Conduct of Deep Dives/Controlled Dives. Deep Dive/Controlled Dive depth changes should be conducted in no greater than 200 foot increments when above one-half the maximum operating depth and in no greater than 100 foot increments when below one-half the maximum operating keel depth. Moderate speeds (within the limits of the submerged operating envelope) and angles must be used. Trim must be continually adjusted to provide neutral buoyancy.

9.3.3 Deep Submergence Bill. The Deep Submergence Bill shall be in effect with systems in the maximum secure condition and all unnecessary sea connected systems isolated. The main ballast tank blow system shall be lined up with all banks within 200 psi of full pressure. Cycling of the rudder and planes through full travel should be limited to the maximum authorized operating depth minus 100 feet at a moderate speed.

9.3.4 Valve Operation. Seawater system valve operations during post industrial availability and new construction Sea Trials will be in accordance with reference (d).