Table of Contents; Page 36; Page 43; Index
LOCOMOTIVE BOILERS
Before entering into the details of the various elements comprising a locomotive, it is thought advisable to give them some study in order to become familiar with the names of the various parts and their relation to each other. Fig. 32.(See page 27 for figure and associated index) is given for this purpose and represents a longitudinal section of a 440 type locomotive with all parts numbered and named. This figure should be carefully studied in order that the future work of the text may be clearly understood.
A locomotive boiler may be defined as a steel shell containing water which is converted into steam, by the heat of the fire in the firebox, to furnish energy to move the locomotive.
Locomotive boilers are of the internal fire-box, straight fire-tube type having a cylindrical shell containing the flues and an enlarged back-end for the fire-box, and an extension front-end or smoke-box leading out from which is the stack.
Classification of Boilers as to Form. Locomotive boilers are classified as to form as follows:
Straight top, Fig. 33, which has a cylindrical shell of uniform diameter from the fire-box to the smoke-box.
Wagon top. Fig. 34, which has a conical or sloping course of plates next to the fire-box and tapering down to the circular courses.
Extended wagon top, Fig. 35, which has one or more circular courses between the fire-box and the sloping courses which taper to the diameter of the main shell.Classification of Boilers as to Fire-Box Used. Boilers are frequantly referred to also and designated by the type of fire-box contained, such as Belpaire, Wooten, and Vanderbilt. This designation does not in any way conflict with the classification of different types of boilers already given but refers to the general character of the fire-box; that is, the boiler may be classified as a straight top boiler and at the same time a Wooten fire-box. Since this is true it is necessary to know the distinction between the Belpaire, the Wooten, and the Vanderbilt types of fire-box.
The Belpaire boiler, as illustrated in Fig. 36, has a fire-box with a flat crown sheet A jointed to the side sheets B by a curve of short radius. The outside sheet C and the upper part of the outside sheets D are flat and parallel to those of the fire-box. These flat parallel plates are stayed by vertical and transverse stays and obviate the necessity of crown bars to support and strengthen the crown sheet. The advantage gained is that the stay bolts holding the crown and side sheets can be placed at right angles to the sheets into which they are screwed.
The Vanderbilt fire-box is built of corrugated forms, as illustrated in Fig. 37. The principal object in the design of this fire-box is to eliminate stay bolts which are a source of much trouble and expense in keeping up repairs. Only a few locomotives fitted with this type of fire-box have been used.
The Wooten fire-box, socalled, obtained its name from the designer. This form of fire-box extends out over the frames and driving wheels, as may be seen from Fig. 38. It was designed for the purpose of burning fine anthracite coal but soon after its introduction it found favor with a few railroads using bituminous coal. The drawing shown in Fig. 39 illustrates its general construction. It has rendered good service in certain localities but has never been very extensively used. In addition to the designations given the various boilers already mentioned, they are frequently spoken of as narrow or wide fire-box locomotives. A narrow fire-box is one which is placed between the frames or may rest on the frames between the driving wheels. These conditions limited the width of the fire-box from 34 to 42 inches. Wide fireboxes are those which extend out over the wheels, as is the case in the Wooten, their width only being limited by road clearances. The dimensions commonly used are as follows: width 66, 76, 85, 103, and 109 inches; length 85, 97, 103, 115, and 121 inches, all dimensions being taken inside of the fire-box ring. Variations above and below these figures are often found which are made necessary by existing conditions.
In locomotives where the fire-box is placed between the axles, the length of the fire-box is limited by the distance between the axles and is rarely more than 6 or 9 feet, from which the front and back legs must be deducted. Placing the fire-box on top of the frames makes any length possible, the length being governed by the capability of the fireman to throw the coal to the front end of the fire-box.
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