This section is from the book "A Treatise On Architecture And Building Construction Vol4: Plumbing And Gas-Fitting, Heating And Ventilation, Painting And Decorating, Estimating And Calculating Quantities", by The Colliery Engineer Co. Also available from Amazon: A Treatise On Architecture And Building Construction.
131. The walls which constitute a boiler setting have several duties to perform: first, in many cases, to sustain the weight of the boiler and maintain it in position; second, to confine the fire and properly direct the hot gases; third, to prevent loss of heat as much as possible.
In setting a boiler the following points should be carefully-observed:
1. Brick walls are always subject to distortion when exposed to heat, and, if not carefully confined, will become cracked and bulged so much out of shape that they will not properly support the boiler. Therefore, they must be well bound by means of buclrstays and tie-rods, as in Fig. 47.
2. The best practice is to suspend all large boilers from horizontal wrought-iron girders by adjustable hangers, and to support the girders upon wrought-iron posts which are practically independent of the brick walls. When the shell is supported by brackets, as in Figs. 46 and 47, the brackets should rest upon rollers, so that the shell may expand and contract freely. The rollers should bear upon stiff iron plates which are firmly embedded in the brickwork.
3. No part of the boiler which is not covered with water at all times should ever be exposed to the hot gases. In other words, the fire line should always be below the lowest water level.
4. All parts of the walls which are exposed to fire or hot gases should be faced with firebrick of good quality. The lining should be not less than 4 1/2 inches, thick, and should be so laid that it can be easily renewed without destroying the main walls.
5. The walls enclosing a boiler must be made independent of all other walls, so that they can expand and contract freely. They must never be bonded into the walls of a building, nor into a brick smokestack.
6. The exposed parts of a boiler should always be covered with some good non-conducting material, to prevent loss of heat. Cylindrical boilers may be arched over with brick if desired. The brick should not touch the shell, but should stand off about 1 inch.
7. Cylindrical boilers which are not provided with good feedwater purifiers should be set on an inclination of about 1 inch in 10 or 12 feet, the end over the fire being highest. The mud and sediment will then gravitate towards the rear end, and the tendency to form scale on the plates over the fire will be reduced.
8. Cleaning doors should be provided, which will give easy access to all the heating surfaces of the boiler that are liable to become covered with soot or dust, and to all parts of the flues which may accumulate soot or ashes. If the spent gases are conveyed to the stack through iron pipes, manholes with tight covers should be provided at intervals, so that the entire length of pipes may be easily brushed out.