|Fig.1: Water Drum of Steam Boiler|
If the surface heat transfer in steam boiler may not be enough to produce steam saturation for specific end use, so require additional tubes to increase heat transfer surface. These additional tubes connecting between steam drum and water drum were called steam boiler bank. This is necessary for industrial steam boiler that has low pressure. Steam boiler bank usually consist of steam drum which be typically located on the top, a series of bent connecting tubes on the middle, and water drum on the bottom.
Water drum is a pressure chamber of a drum type located at the lower extremity of a watertube-steam boiler convection bank. The steam drum internals and tube sizes are arranged so that subcooled water travels down the tubes into water drum. From water drum, water is distributed by downcomer to lower drum and then distributed again to the tubes of furnace wall where water is partially converted to steam and returned to the steam drum
Water drum is present only in the bidrum steam boilers and play a less important role such as: a water drum acts like a large header connecting the riser and downcomer tubes of the bank, and it feeds the downcomers to the various evaporator sections. The water drum is always smaller than the steam drum as there are no important internals.