10.1.2 Continuous drains
In regimes such as the LP cylinder, where the steam is wet during normal operation, drain lines are necessary to provide continuous drainage. Such lines have orifice plates to restrict the flow. In places where there is likely to be a large collection of condensate during start-up, the line incorporates a valved by-pass in addition to the orifice.
All clean drain lines lead to the drains receivers, located near the condenser. On entering this vessel some of the drains water flashes into steam which is vented to the main condenser. Sometimes the vents are fitted with desuperheating sprays. The coolant for the spray is supplied by the condensate extraction pump and a temperature sensor regulates the amount of water supplied to the sprays.
The remaining condensate drains to the bottom of the condenser. On some units, pumps are required to lift the condensate from the drains receiver to the condenser. A sight glass gives local indication of the level in the drains vessel.