DEFECTS AND NECESSARY REPAIRS.
Fig. 68.
[Fig. 68] represents a patch called a “spectacle piece.” This is used to repair a crack situated between the tube ends. These are usually caused (if the metal is not of bad quality) by allowing incrustation to collect on the plate inside the boiler, or by opening the furnace and smoke doors, thus allowing a current of cold air to contract the metal of the plates round the heated and expanded tubes.
The “spectacle piece” is bored out to encircle the tubes adjacent to the crack, or in other words, to be a duplicate of a portion of the tube plate cracked. These plates are then pinned on to the tube covering the crack.
Steam generators, as they are exposed to more or less of trying service in steam production, develop almost an unending number and variety of defects.
When a boiler is new and first set up it is supposed to be clean, inside and out, but even one day’s service changes its condition; sediment has collected within and soot and ashes without.
Unlike animals and plants they have no recuperative powers of their own—whenever they become weakened at any point the natural course of the defect is to become continually worse.
In nothing can an engineer better show his true fitness than in the treatment of the beginnings of defects as they show themselves by well-known signs of distress, such as leaks of water about the tube ends, and in the boiler below the water line, or escaping steam above it. In more serious cases, the professional services of a skillful and honest boiler maker is the best for the occasion.
In a recent report given in by the Inspectors the following list of defects in boilers coming under their observation was reported. The items indicate the nature of the natural decay to which steam boilers in active use are exposed. The added column under the heading of “dangerous” carries its own lesson, urging the importance of vigilance and skill on the part of the engineer in charge.
| Nature of Defects. | Whole Number. | Dangerous. | ||
|---|---|---|---|---|
Cases of deposit of sediment | 419 | 36 | ||
Cases of incrustation and scale | 596 | 44 | ||
Cases of internal grooving | 25 | 16 | ||
Cases of internal corrosion | 139 | 21 | ||
Cases of external corrosion | 347 | 114 | ||
Broken and loose braces and stays | 83 | 50 | ||
Settings defective | 129 | 14 | ||
Furnaces out of shape | 171 | 14 | ||
Fractured plates | 181 | 84 | ||
Burned plates | 93 | 31 | ||
Blistered plates | 232 | 22 | ||
Cases of defective riveting | 306 | 34 | ||
Defective heads | 36 | 20 | ||
Serious leakage around tube ends | 549 | 57 | ||
Serious leakage at seams | 214 | 53 | ||
Defective water gauges | 128 | 14 | ||
Defective blow-offs | 45 | 9 | ||
Cases of deficiency of water | 9 | 4 | ||
Safety-valves overloaded | 22 | 7 | ||
Safety-valves defective in construction | 41 | 16 | ||
Pressure-gauges defective | 211 | 29 | ||
Boiler without pressure-gauges | 3 | 0 | ||
This list covers nearly, if not all, the points of danger against which the vigilance of both engineer and fireman should be continually on guard; and is worth constant study until thoroughly memorized.