Document 0gjzdnRakpQjnG9oK6XXoGGqO

HEATING VENTILATING AIR CONDITIONING GUIDE 1943 Fig. 2. Connections foe Reducing'.Valves of Size Less than 4 In. PIPE TUNNELS - Where steam heating lines , are installed in tunnels large enough to provide walking space, the pipes are supported by means of hangers or roller frames on brackets or frame racks at the side or sides of the tunnel. The pipes are insulated with sectional pipe insulation over which is placed a sewed-on, painted canvas jacket or a jacket of asphalt-saturated asbestos water-proofing felt. The tunnel itself is usually built of concrete or brick and water-proofed on the outside with membrane water-proofing. On account of their relatively high' first cost as compared with smaller conduits, walking tunnels are sometimes not installed where provision for the heating lines is the only consideration, but only where they are required to. accommodate miscellaneous other services or provide underground passage between buildings.. `. OVERHEAD DISTRIBUTION In some industrial and institutional applications, the distribution piping may be installed, entirely or in part, above ground. This method of construction has the advantage of requiring no excavation arid being easily maintained. ' ... CHAPTER 17. DISTRICT HEATING Pressure reducing valve Service valve Customer's pressure reducing valve .Fig. 4. valve to be at least equal to American Standard 175 lb S. S. P. Pipe to be standard weight Continuous-flow type float trap Steam Supply Connection when Using Two Reducing Valves INSIDE PIPING Figs. 2 and 3 show typical service connections used for low pressure steam service. As shown in Fig. 2, no by-pass is used around the reducing valve on sizes less than 4 in. Fig. 3 illustrates the use of a by-pass:around reducing valves 4 in. and larger, This latter construction permits the operation of the line in case of failure in the reducing valve. In the smaller sizes, the reducing valve can be removed, a filler installed, and the house valve used to throttle the flow of steam until repairs are made. Fig. 4 shows a typical installation used for high pressure steam service. The first reducing valve effects the initial pressure reduction. The second reducing valve reduces the steam pressure to that required. Most district heating companies enforce certain regulations regarding the consumer's installation, partly to safeguard their own interests but principally to insure satisfactory and economical service'to the consumer. There are certain fundamental, principles that should be followed in the design of a building heating system which is to be supplied from street mains. Although some of these apply to any building, they have been demonstrated to be especially important when steam is purchased. Return main Fig: 3. Connections for Reducing Valves of Size 4 In. and Larger, and for Expanded Valves 334 Fig. 5. Return Piping for Condensation Meter 335 X