CHAPTER XII THE GRATE Q. What should be aimed at in grate designing? A. To get the greatest possible percentage of air space between the bars without letting unconsumed or partly consumed fuel fall through. FFFFFEE Fig. 67. Rocking Grate. Fig. 68. Rocking Grate. Q. How can the action of the fire on cast-iron bars be lessened? A. By making the upper surface of each bar slightly concave or "guttered"; a film of ashes lies in the gutter and protects the iron. Q. What is the best section for grate-bars? A. They should be wider at the top than below, to lessen the liability of clogging with ashes or cinders the spaces between them. Figs. 69, 70 and 71. Water-grate for Bituminous Coal. Q. What sort of a grate is required for burning anthracite coal? A. One consisting of water tubes and pull bars. Q. What class of grates are used for wood? A. Stationary bars, ordinarily placed close together. 100000:0 Front THE GRATE Figs. 72 and 73. Rocking-grate Work. 3. Connecting-bar. 4. Lever. 5. Lever-rod. 6. Lever-handle. 7. Drop-plite. 1. Bar. 2. Frame. plate Rod. 9. Drop-plate Crank. 10. Drop-plate Crank-handle. 8. Drop 11. Drop-plate Crank-bearing. Q. What difference is there between grates for coal and those for wood? A. Those for coal are often made so that they may be shaken. Q. Which takes the larger grate, hard or soft coal? A. Hard, because the fire must be shallower. Q. What grate is usually employed for anthracite or hard coal? A. It is usually long, and has, instead of ordinary grate-bars, tubes in water-connection with the waterspace so as to permit a circulation in them to keep them from melting or burning, and to lessen the liability of mud settling in the lower part at that end. Q. Was the wide grate first used for anthracite or for bituminous coal; and why? A. For anthracite, because it really needed it. Q. What is the advantage of width over length in a fire-box? A. (1) Easier on the fireman; (2) lower temperature and less deterioration of sheets; (3) improved stay-bolt service. Q. How may the fire be drawn where a water grate is used? A. By removing some solid bars which replace every fourth or fifth tube and project clear through both walls of the back end of the fire-box, through tubes provided for that purpose, and have on their back ends rings by which to draw them out. In front they rest on a bearingbar. Figs. 29 and 31 show the type used on the Philadelphia & Reading road. Q. How are water-grate tubes made tight? A. By being calked into the inside plate at the front and back end of the fire-box. Q. How large a grate is needed to burn one ton of coal per hour? A. About eight square feet. This of course depends |