Drum Level Control in Larger Capacity Boiler
Drum Level Control in Larger Capacity Boiler In a large capacity boilers feed pump motor is not directly connected to the boiler feed pump. Between motor and feed pump a hydraulic coupling is used in which an arrangement is given for speed increasing and then regulating through the scoop tube. This provide a variable speed operation while motor is running at constant speed. With the help of scoop tube motor is started with no load and pump is running with it on a re-circulation mode. No direct mechanical connection is there between the motor and the pump shafts. The coupling consists of a radial pump impeller mounted on the motor shaft and a radial flow reaction turbine runner mounted on the pump shaft. Both the impeller and runner are identical in shape and they together form a casing which is completely enclosed and filled with oil. When motor shaft is rotated, the oil starts moving from the inner radius to the outer radius of the pump impeller. This oil enters