CHAPTER II

BOILER SETTINGS AND APPURTENANCES

Foundations-Brick work, etc.-Grate surface-Insulation-Water columns-Steam gages-Safety valves-Rules for finding areas of Fusible plugs and where to place them-Domes and mud drums-Feed pipes-A good arch for the back connection-Blow off pipes and cocks-Surface blow off and circulating system-Feed pumps and feed water heaters-Injectors— Saving effected by heating the feed water with exhaust steam-Apparatus for making coal tests--Heating surface— Rules for figuring the same.

Settings. In the case of internally fired boilers the matter of setting resolves itself into the simple point of securing a sufficiently solid foundation, either of stone or brick laid in cement, for the boiler to rest upon.

But with horizontal tubular or water tube boilers the matter of brick work becomes important, and particular attention should be paid to securing a good foundation for the walls and great care exercised in building them in such manner that the expansion of the inner wall or lining will not seriously affect the outer walls. This can be done be leaving an air space of two inches in the rear and side walls, beginning at or near the level of the grate-bars and extending as high as the fire line, or about the center line of the boiler. Above this height the wall should be solid. Fig. 4 shows a plan and an end elevation illustrating this idea. The ends of some of the bricks should be allowed to project at intervals from the outer walls across the air space, so as to come in touch with the inner walls.

Where boilers are set in batteries of two or more the middle or party walls should be built up solid from the foundation. All parts of the walls with which the

FIGURE 4.

fire comes in contact should be lined with fire brick, every fifth course being a header to tie the lining to the main wall.

Bridge walls should be built straight across from wall to wall of the setting, and should not be curved to conform to the circle of the boiler shell. The proper

distance from the top of the bridge wall to the bottom of the boiler varies from eight to ten inches, depending upon the size of the boiler. The space back of the

bridge wall, called the combustion chamber, can be filled in with earth or sand, and should slope gradually downward from the back of the bridge wall to the floor level at the rear wall, and should be paved with hard burned brick. The ashes and soot can then be easily cleaned out by means of a long-handled hoe or scraper inserted through the cleaning out door, which should always be placed in the back wall of every boiler setting.

Back Arches. A good and durable arch can be made

for the back connection, extending from the back wall to the boiler head, by taking flat bars of iron 5% × 4 in., cutting them to the proper length and bending them in the shape of an arch, turning four inches of each end back at right angles, as shown in Fig. 5. The distance O-B should equal that from the rear wall to the boiler head, and the height, O-A, should be about equal to O-B, and should bring the point A about two inches above the top row of tubes. The clamp thus formed is filled with a course of side arch fire brick,

Fig. 6, and will form a complete and self-sustaining arch, the bottom, B, resting on the back wall, and the top, A, supported by an angle iron riveted across the boiler head about three inches above the top row of tubes. See Figs. 7 and 8.

Enough of these arches should be made so that when laid side by side they will cover the distance from one side wall to the other across the rear end of the boiler. A fifty-four-inch boiler would thus require six clamps,

FIGURE 7.

a sixty-inch boiler seven clamps, and a seventy-twoinch boiler would require eight clamps; the length of a fire brick being about nine inches. In case of needed repairs to the back end of the boiler the sections can be lifted off, thus giving free access to all parts, and when the repairs are completed the arches can be reset with very little trouble and much less expense than the building of a solid arch would necessitate. This form of segmental arch allows ample freedom for expansion

of the boiler, in the direction of its length, without ieaving an opening when the boiler contracts.

The crosswise construction of arch bars, while affording equal facility in repair work, is necessarily more expensive than the form here described, and is also open to the objection that it cannot follow the contracting boiler and maintain a tight joint or connection

FIGURE 8.

B

between the back arch and the rear head above the tubes.

Boiler walls should always be well secured in both directions by tie rods extending throughout the entire length and breadth of the setting, whether there be one boiler or a battery of several. The bottom rods.

should be laid in place at the floor level when starting the brick work, and the top rods extending transversely across the boilers can be laid on top of the boilers.