Steam plant and method of controlling same

A steam plant comprising

• a feed water line for conveying a flow of feed water;
• a feed water pump in said line for pumping feed water therethrough;
• an evaporator in said line downstream of said pump for heating the flow of feed water to steam;
• a water separator downstream of said evaporator for separating water from steam flowing therethrough;
• control means for controlling the feed water quantity in said line;
• first means for generating a first signal in response to the level of water in said separator;
• second means for generating a second signal in response to the steam temperature downstream of said separator;
• a changeover element connected to said control means and selectively connected to said first means and said second means to selectively deliver one of said signals to said control means for controlling said control means in response thereto;
• means for determining a temperature difference between the steam temperature upstream of said separator and the saturation temperature of the steam in said separator;
• and
• a comparator for comparing said temperature difference with a selected critical value to deliver a control signal to said changeover element in response thereto whereby said changeover element is actuated to deliver said first signal to said control means when said temperature difference is less than or equal to zero, said changeover element is actuated to deliver said second signal to said control means when said temperature difference is greater than said critical value, and said changeover element is retained in a previously activated state when said temperature difference is greater than zero and less than said critical value.