Power Magazine, Feb. 2014, by S. Zaheer Akhtar, PE.
http://www.powermag.com/establishing-proper-pressure-drop-for-feedwater-flow-control-valves/

"Feedwater control valves play a critical role in boiler operation. One important parameter of their design is the pressure drop at the rated condition as well as off-design conditions. However, conventional methods used for establishing control valve pressure drop cannot be used at face value without reviewing all plant operating scenarios."