This secondary suction pipe is provided with a valve because it must be shut off before the engine is started.
All the drain pipes from the cylinder pass into the condenser so as to save the fresh water.
The air pump is usually worked by a beam, receiving motion from the cross head of the low pressure cylinder.
The circulating pump is usually worked by the same beam as the air pump, or receives its motion from some other part of the main engine. In some cases, however, an independent circulating pump is employed.
It receives its water from a pipe leading to the sea, which is provided with an injection cock or Kingston valve, placed close to the side of the ship and well below the sea level. This valve is used to shut off the circulating water and prevent its flooding the ship in case of accident to the condenser or circulating pump.
The circulating water, after passing through the condenser, discharges overboard through the circulator discharge pipe.
This pipe is also provided with a valve placed close to the ship’s side, at or above the water level, so that the opening at the ship’s side may be closed, and sea water prevented from entering the ship in case of breakage to the condenser, etc.
To enable a surface condenser to be used as a jet condenser in case of accident to the circulating pump, a pipe leads from the injection cock of the circulating supply pump into the bottom of the exhaust pipe or column, where it enters the condenser.
This pipe is supplied with a spray or rose nozzle, which divides up the injection water and causes it to condense the steam as it enters the condenser.
An additional pipe is sometimes added to the suction side of the circulating pump, for use in pumping out the bilge by means of the circulating pump in case of emergency, and also for pumping out ballast tanks when the vessel is provided with such tanks.