Boilers and Related Equipment

STEAM DRUM INTERNALS The steam drum contains steam separating equipment and internal piping for distribution of chemicals to the water, for distribution of feedwater and for blowdown of the water to reduce solids concentration.           Typical drum internal components are noted below: Steam Horizontal Separators Standard horizontal, in-line. Driers Integral Chevron, non-drainable. Feed Pipe Perforated, tee'd inlets. Continuous Blowdown Pipe A single outlet perforated, tee'd from centerline of drum. Chemical Feed Pipe A single inlet perforated, tee'd from centerline of drum. Downcomer Pipes Pipes, equidistant across the drum. An internal (girth) baffle extending almost the full length of the shell forms an annulus along the bottom half of the steam drum. The steam-water mixture from the furnace waterwall risers enters the drum in this annulus and then passes through the horizontal steam separators. The first stage of separation of steam from the water is accomplished here. As the mixture follows the curved contour of the separator, the heavier water particles are forced to the outside, discharging through the primary drain and then through wire mesh into the bottom of the drum. The wire mesh dissipates the discharging water velocity and allows any entrained steam to escape. The separated steam flows out of the openings on the outboard sides of the separators and into the Chevron driers. The final separation of moisture in the steam is accomplished as the steam comes into contact with the W-shaped Chevron elements forming the drier assemblies. Steam enters the driers at a low velocity and makes several abrupt changes in flow direction. This causes the entrained moisture to adhere to the large surface area presented by the Chevrons. The water film then drains by gravity to the lower part of the drum. The separated steam flows into the dry box and leaves the drum through the steam tubes at the top. These tubes supply steam to the superheater sections. The water separated from the steam falls to the water space of the drum and through the radial vortex eliminators to downcomer pipes. The downcomer pipes carry the water to the bottom of the unit for distribution to the furnace waterwalls