Simon
The valvechest shown is indeed the seawater chest and has branch off to stb and port luboilcooler. I am posting a brushed up version of the seawater coolingsystem.
The blue line is the suction from sea. First the conventional hull seavalve (seen on your U historia picture 13) same has an air blow connection for seaweedcleaning, then as always on the seavalves, a second valve (sluicevalve to be shut for depthcharges) also seen on your picture, 14, and a filter. The pipes ends up at the engine attached pistonpump fwd end of engine.
Then the colour changes to green(pressureside) passes an airvessel ( to compensate for the pistonpump pressurevariations) and continues as previously explained.
Tore