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Section 2 Principles of Design and Construction
201. General Principles
1. Diving, buoyancy and trimming tanks are to be so designed and arranged to be stable in any operation.
2. It is to be possible to operate the submersible safely on the surface under the maximum permis- sible seaway conditions.
3. When submerged, it is to be possible to balance and trim the submersible at any depth less than or equal to its nominal diving depth.
4. The submersible is to at all times be capable of returning safely to the surface.
5. In the event of failure of the buoyancy tank system the submersible is to be capable of surfacing by jettisoning of ballast and/or emergency blowing of the diving tanks and is to float on the sur- face in an upright stable position.
202. Diving tanks
1. Diving tanks are to be designed and fabricated to withstand the impact of waves and their own in- ternal static pressure.
2. Diving tanks are to be provided with vents enabling them to be completely flooded with water.
The venting system is to be provided with a separate shut off device for each individual tank. The vent valves are to be designed such as to prevent unintentional opening.
3. Where diving tanks have flooding holes without means of closure, double shut off devices may be stipulated for the vent pipe.
4. Where diving tanks are evacuated by compressed air, it is necessary to ensure that blowing the tanks cannot cause an excessive overpressure.
5. Where the diving tanks are to be pumped out, the flooding holes are to be fitted with means of
closure and steps shall be taken to ensure that the freeing under pressure.
of the tanks cannot cause an excessive
203. Buoyancy tanks
1. Buoyancy tanks are to be designed for a working pressure diving pressure subject to a minimum of ĀÀ Ğ Ë ba r. The against excessive over and under pressures.
corresponding to 1.2 times the nominal buoyancy tanks are to be safeguarded
2. Buoyancy tanks located within the pressure hull may be designed as gravity tanks provided that freeing is effected by pumps only.
3. The capacity of buoyancy tanks is to be sufficient to compensate for all the changes in buoyancy expected to arise during the planned diving duties plus a reserve capacity of at least 10 %.
4. Buoyancy tanks may be freed by compressed air or by pumping. The quantity of water admitted during flooding and expelled during freeing must be indicated. For that purpose buoyancy tanks are to be fitted with contents gauges giving a continuous reading.
5. The vent pipes of buoyancy tanks are to be designed and arranged in such a way that water can- not penetrate inside the vehicle unnoticed.
204. Trimming devices
1. To achieve maximum leverage, trimming tanks are to be located as far forward and aft on the ve- hicle as possible.
2. The transfer of water may be effected by pumping or by compressed air. An automatic control de- vice shall ensure that the transfer always takes place in the desired direction. The quantities of wa- ter used for trimming are to be indicated.
3. Trimming tanks which are located inside the pressure hull and which are freed by pumping may be designed as gravity tanks. If the trimming tanks are freed by compressed air, they are to be de- signed as pressure vessels according to the pressure of the compressed air system. Trimming tanks located on the outside of the submersible are to be designed to withstand an external pressure equivalent to 1.2 times the nominal diving depth.
4. If longitudinally movable weights are provided for trimming, steps are to be taken to ensure that the weights can not accidentally slip out of position.