22 Chapman Valve

My retired merchant marine friend Steve Maisch offered the following comments about this page:

The Chapman Valve from what I see looks to be on the main circulation system salt water piping. Circulators normally have a high and low suction for in-port or at sea use with one overboard. The seawater cools and condenses the low pressure turbine's exhaust in the main condenser, returning it as condensate to the system.