Bias bellows for thermohydraulic feedwater regulator

A water level regulator for a steam drum having a steam space, a water space, a feed water line and a feed water regulating valve in the feed water line with a movable control element, comprising:

• an inclined inner tube having an upper end adapted for connection to the steam space and a lower end adapted for connection to the water space;
• an inclined outer tube connected around said inner tube and defining a control space therewith extending across upper and lower limits of water level in the steam drum, said control space adapted to receive a volume of fluid which is pressurizable upon an increase of water level in the drum;
• a connecting tube connected to said control space adapted to connect said control space to the regulating valve control element for passing fluid to move the control element;
• a bias bellows defining a variable space connected to said connecting tube;
• and
• biasing means connected to said bias bellows for changing the volume of said variable space to change an overall setting relationship between the regulating valve control element and the steam drum water level.