[PSUBS-MAILIST] G.L. Rules Piping systems, Pumps & Compressors

[Alan James]

Hi people,
I have omitted the summary on Vessels & Apparatus Under Pressure
as there wasn't much of consequence that hadn't previously been covered,
and are now on to Piping Systems, Pumps & Compressors.
Some good stuff here.
   Pipes which go through the pressure hull are to be fitted with two shut off
devices. One of which is located at the hull wall.
   Pipes passing through spaces inadequate for maintenance are to be one piece.
   Manual shut off devices are to be closed by turning in the clockwise direction.
   All sea valves & essential shut off valves are to be clearly indicated.
   Each hose is to be designed for the burst pressure, which is for liquids, 4x &
for gases, 5x the maximum allowable working pressure.
   Generally submersibles are to be equipped with a bilge system capable of 
removing water from condensation or leakage from all spaces in the sub.
   In the bilge system, two non return valves are required. The wording for their placement is "two non return valves are to be mounted in front of the freeing connections. One of these non-return valves is to be placed in the pipe in front of each suction." (not sure what they mean).
   Bilge pumps are to be of self priming type.
   If you are using the bilge pump to also operate your trimming & compensating
systems, valves have to be fitted so that from the event of wrongly operating valves
or partially opened valves, no seawater can get in the submersible. The bilge system has to have a back up pump, & with an interconnected bilge / trim / compensating system; the back up pump  must be able to service all systems.
Where diving tanks are emptied by pumps, the back up pump has to be connected to the 
emergency power supply.
The air supply for the diving ballast tanks has to be sufficient to blow the tanks 4x at the surface & 1.5x at the nominated diving depth. And enough to blow the compensating tanks
3 times completely at nominated diving depth. (I'm not sure if this is additional to the ballast tank requirements)
The compressed air supply is to be carried in two separate banks of receivers with the same total volume & fitted with valves so that no unintentional pressure equalization can occur between different systems.
Where pressure reducing valves are fitted these are to be redundant. In single cases provision can be made for bypassing with manual control. In addition, a safety valve is to be fitted on the low pressure side of the pressure reducing valve, or equally safe alternative.
Alan
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