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Section 2 Principles of Design and Construction
201. Pipes, valves, fittings and pumps
1. All pipes, valves, fittings and pumps liable to be loaded with the diving pressure are to be de- signed for the test depth.
2. Pipes which are led through the pressure hull wall are to be fitted with two shutoff devices, one of which is to be located immediately next to the hull wall.
3. Oxygen pipes are not to be routed close to oil pipes.
4. Gas pipes and electric cable conduits are to be routed separately wherever possible.
5. Shutoff devices are to be approved by the Society. Valves and fittings with screw-down covers or spindles are to be safeguarded against accidental unscrewing.
6. Manual shutoff devices are to be closed by turning in the clockwise direction.
7. The open and closed positions of all sea valves and essential shutoff valves are to be clearly indicated.
8. All valves acting as sea connections are to be so designed that the tapered plug opens against the external pressure.
9. Only screw-down valves are permitted in pipes carrying oxygen. Ball valves may, however, be used as emergency shutoff devices.
202. Bilge pumping and ballast equipment
1. Autonomous submersibles are to be equipped with a bilge system capable of freeing all the spaces inside the vehicle from water due to condensation and leakage.
2. To prevent ballast water and seawater from penetrating inside the vehicle through the bilge system, two check valves are to be mounted in front of the freeing connections. One of these check valves is to be placed in the pipe in front of each suction.
3. Where the bilge, seawater and ballast water systems are interconnected, the connecting pipes are to be fitted with valves in such a way that seawater is reliably prevented from penetrating inside the vehicle through the bilge system even in the event of faulty switching of the valves or when the valves are in intermediate positions.
4. Bilge pumps are to be of the self priming type.
5. The bilge and ballast system are to be provided with at least one stand-by pump.
6. Where diving tanks are freed only by pumps, the standby pump is to be connected to the emer- gency power supply.
203. Compressed air systems
1. Where air is used to blow diving, buoyancy and trimming tanks, the supply of air carried on board shall be sufficient to blow the diving tanks at least 4 times on surface and the buoyancy tanks at least 3 times at the nominal diving depth. In normal operation, the compressed air receivers provid- ing this supply may not be used for other purposes.
2. A compressor should be provided for charging the compressed air receivers.
3. The compressed air supply is to be carried in at least 2 separate tanks of receivers.
4. The compressed air systems are to be fitted with valves in such a way that no unintentional pres- sure equalization can occur between different systems.
5. Where pressure reducing valves are fitted, provision is to be made for bypassing and disconnecting these in the event of a fault. In addition, a safety valve is to be fitted on the low pressure side of the pressure reducing valve.
6. Compressed air systems are to be equipped with a sufficient number of pressure indicators.
7. Compressed air systems which come into contact with seawater are to be designed accordingly and are to be separated from other systems. In addition, measures are to be taken which as far as pos- sible rule out the possibility of seawater penetrating into the compressed air system.
204. Hydraulic systems
1. All piping belonging to hydraulic systems which are led through the pressure hull and which are necessary to the safety of the vehicle are to be designed for the maximum allowable working pres- sure of the system. Wherever necessary, allowance is to be made for the possibility of a pressure rise due to the penetration of seawater into the system.
2. Hydraulic systems essential to the safety of the vehicle are to be equipped with at least one power driven pump and one hand operated emergency pump. Autonomous submersibles are to be equipped with two power driven pumps.
3. In individual cases, hydraulic systems not designed for continuous operation may also be equipped with hand operated pumps.
4. All valves and fittings, including hydraulic accumulators, which are fitted in submersibles are to be designed in accordance with Par 1. Valves and fittings are to be placed in easily accessible positions.
5. Hydraulic systems are to be fitted with filters to keep hydraulic fluid clean. In addition, provision
is to be made for venting and dewatering the system.
level indicators. Wherever necessary, hydraulic systems
the hydraulic fluid.
Hydraulic fluid tanks are to be fitted with are to be equipped with means of cooling
6. Hydraulic lines should not be routed close to oxygen systems.
7. When selecting the hydraulic oil, allowance is to be made not only for the service conditions but also for the temperatures occurring during the commissioning or repair of the submersible.
8. Hydraulic systems are to be equipped with all the indicating devices necessary to the operation of the system.