Don.
Skizzenbuch fueloil watercompensating.
The simple yet ingenious system of selfregulating seawatercompensating fueltanks might be a bit hard to understand. Basically the system works in the same manner for the internal as the external watercompensated tanks. There are several reasons for using watercompensating. 1. The compensating of weight loss due to the fuelconsumption although the seawater has a higher specific gravity, the weightcompensating being plus or minus is less. 2. The free surface effect is reduced which is important particularly to a submarine. 3. It gives a simple way of transferring the fuel in the system.
The use of the saddle ballasttanks 2 and 4 port and starboard as fueloil tanks require special precautions. The mainventing system has to be blocked and secured shut. This is done by shutting gatevalves and not cumbersome blindflanges in the ventduct between the tanks. The ventduct between the gatevalve and the mainvent has a drain/ventvalve which has to be open. The gatevalve and the drain/ventvalve are operated from the casingdeck. When diving the mainvents for 2 and 4 are open permanently and not shut while being submerged as ordinary ballastventing so you let the seawater fill the ventpipe to the gatevalve, hence the open vent/drainvalve, and the ventduct is compensated and pressure equalized.
As the tanks have a HP blowing, the hullvalves for the blowing are shut and secured to prevent structure damages.
The compensating water pipes goes from the headertank to a small chamber ( about 1,5 % of the tankvolume) at the bottom of the tank., from this chamber goes a short pipe into the tank bottom and an equalizing pipe direct to the sea. The two connections are controlled by a double seated selectorvalve operated from the casing. The valve has only two positions, either to the fueltank or direct to the sea. When in fueltank configuration the Kingstons are shut and the selectorvalve open to the fueltank and thus shut to the sea.
In the ballastank configuration the gatevalves are open, the drainvalve shut and the main ventvalve operated as an ordinary mainvent valve. The compensating selectorvalve is put in direct connection with the sea and shut to the tank thereby the headertank is equalized when diving and submerged. The HP hull blowingvalves are opened and secured. In this way when blowing the tank air or pressureized water cannot enter into the compensating system via the selector valve. The compensatingpipes ends appr 10 cm lower than the fuel venting pipe intake, acting as a waterdischarge pipe by fueling described by you. This allows time to stop fueling and thus prevent any fuel entering the compensating watersystem.
I know it became a long story and may be a bit complicated so I tried to make some sketches as shown below.
Tore
