This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1918 Excerpt: ...w = weight of steam flowing in pounds per minute. L--length of pipe in feet. di = diameter of pipe in inches. D = average density of steam in pounds per cubic foot. The value of the coefficient / given above has been found to be correct for small pipes and comparatively low velocities. For large pipes and high velocities the value of / is considerably lower.1 119. Factors Affecting the Size of Pipes.--The sizes of pipes to be used in a heating system depend upon several factors. The fundamental requirement as regards the supply pipes is that they must be of sufficient capacity to transmit the required quantities of steam with the pressure differential which is available. The latter depends somewhat upon the source of the steam supply. When exhaust steam from an engine or turbine is used for heating, it is best, from the standpoint of economy, to make possible the carrying of a low back-pressure by designing the heating system to operate with an initial pressure of not over 2 pounds per square inch. The same practice should usually be followed when steam is taken direct from a boiler, as it may be desired at some future time to use exhaust steam. The circulation will also be much better and the system more satisfactory if the pipe sizes are ample. When a vacuum pump is used the greater pressure differential thus set up makes possible the use of smaller pipes but, it is well, nevertheless, to design the supply piping to operate as a gravity system with a moderate pressure drop so that the pump can be shut down at times if desired. The return pipes, however, can be made somewhat smaller if a vacuum pump is to be used. Another factor which makes an extreme reduction in the size of the supply pipes undesirable is the noise caused by the resulting high velocity of..