Brushes, formed of stiff bristles or wire, are used as a retarding device for circular or rectilinear motion.
Section 6.—TYPES OF BOILERS.
Vessels or containers of every conceivable shape have been used as boilers. Many of the older types are now obsolete, but the following are these most commonly used:—
VERTICAL BOILERS.
61. Ordinary centre flue boiler. Sometimes the centre flue is surrounded with tubes, as No. 65.
62. Vertical multitubular.
63. Vertical boiler, with diagonal tubes and smoke boxes.
64. Vertical return-flue.
65. “Pot” boiler.
66. “Field” boiler; with suspended tubes and internal circulating tubes.
67. Vertical egg-end boiler; with spiral flue. Large vertical boilers sometimes have cross flues, or large tubes.
HORIZONTAL BOILERS.
68. Portable “loco-type” multitubular.
69. Fixed return-tube.
Larger plate.
70. Fixed “loco-type” multitubular; a favorite and useful form, giving good results, and easily cleaned.
71. Fixed “loco-type,” with underneath fire-box; sometimes used to economise space, is self-contained, and usually stands on cast-iron feet.
72. Multitubular-horizontal; self contained; on cast-iron feet.
73. Egg-end boiler; not much used except where the coal burnt per h.p. per hour is not an important consideration.
74. “Cornish”; one flue, with enlarged fire-box tube. This type is often made with a parallel flue with cross tubes fixed at intervals throughout its length.
75. “Lancashire”; two flues; sometimes has enlarged fire-box tubes, as No. 74.
76. Oval flue boiler, with “Galloway” tubes. The Lancashire type is frequently combined with this form by arranging the two circular flues to open into one oval one.
77 & 78. “Elephant” boilers; employed in connection with coke ovens and other sources of waste heat.
MARINE BOILERS.
79. Ordinary box form, with internal fire-box and return flue.
80. Same type, but with two fire-boxes and multitubular return tubes.
81. Underneath fire-boxes and multitubular return tubes above the fire-boxes, sometimes duplicated, as No. 82.
Larger plate.
83. Has two central fire-boxes and side return-tubes.
The foregoing box patterns are rapidly going out of use, as unsuitable for the higher pressures prevailing with compound engines.
84. Cylindrical boiler, with three fire tubes and three sets of return tubes. This form is much used, the surfaces requiring stays being very limited. It is made with double fire-boxes as shown, or with single fire-box, as No. 81.
85. Cylindrical single flue and return-tube.
86. Cylindrical single flue and multitubular.
87. Cylindrical double flue and multitubular, longitudinal section similar to No. 86.
88. Cylindrical saddle boiler, multitubular, used for shallow vessels, launches; &c.
HOUSEHOLD BOILERS.
89. Kitchen “ell” boiler.
90. Kitchen or back boiler, for ordinary grates.
91. “Saddle” boiler. The varieties of this type are legion. Every conceivable cross-bridge, water-way, tube, and flue has been added to it by various makers. See Messrs. Graham and Fleming, and other makers’ Lists.
92. Annular cylindrical greenhouse boiler.
93. Annular conoidal greenhouse boiler.
94. Vertical cylindrical, closed top greenhouse boiler.
The last four are types of the greenhouse boilers most in use. They are usually of wrought iron, and all seams welded.
95. Back boiler for ordinary register grate.
96. “Boot” boiler.
97. Scullery, or wash-house boiler.
98. Scullery, or wash-house boiler, heated by steam. In public laundries these are usually rectangular in plan.
99. Coil boiler, used for small greenhouses, &c.
100. Sectional, or “Tubulous” boiler. Root’s, and others, are on this principle. They are constructed of simple pipes and T or L pieces, usually bolted together.
Section 7.—BLOWING AND EXHAUSTING.
Some of the mechanical blowers are too well known to need illustration here; such are the ordinary Beam Blowing Engine, as in use for blast furnaces, Vertical Blowing Engine, and Horizontal Blowing Engine. In all these a cylinder and piston form the blowing device. Nearly every form of rotary engine (see Section 75) may, by reversal, be converted into a blowing machine. See Root’s patent, No. 1307; Baker’s, 1325, and others in common use. Fans, centrifugal, (see No. 1337) are still the commonest blowing machines, and are especially suited for light pressures and large volumes of air; but for pressures of from 1⁄2 lb. per square inch and upwards, the rotary or cylinder types are best. The following are devices not so well known, but sometimes useful:—
101. The “Trompe,” or water-jet blower. Water under pressure is discharged through a rose into a funnel-shaped inlet, carrying with it a quantity of air (see Section 45); the water runs off at an overflow, and the air is led away by a pipe.
102. Steam-jet blower. (See Section 45.)