Document KjEgZOo92aG1vx3eOkJGXKdr

American Society of Heating and Ventilating Engineers Guide, 1937 tJiis type of corrosion than the ferrous metals, and considerable attention is now being given to corrosion-resistant' linings for ferrous pipe. Castiron pipe, sometimes alloyed with other metals, also deserves con sideration. PROBLEMS IN PRACTICE 1 What is the meaning of IPS brass pipe? It means that the brass pipe has the same external diameter as steel pipe in the same nominal pipe size and that the wall thickness is sufficient to allow cutting of threads for use with standard size threaded fittings. 2 Why is thin-walled copper pipe made up with sweated joints? If the pipe were threaded it would be necessary to use at least standard-weight wall thickness on account of the metal removed in threading. Flared ends with coupling nuts may be used, but this construction is expensive and hard to keep tight: 3 9 How are pipes designated in diameters of 12 in. and less? By weight and nominal size, referring to the approximate inside diameter. 4 How are pipe sizes designated in diameters of 14 in. and more? By wall thickness and outside diameter. 5 9 Why are expansion joints required in steam pipes? To care for the change in length of the line brought about by a change in temperature. 6 What devices are used for taking up expansion? Expansion joints, swivel joints, and the inherent flexibility of the pipe itself. 7 Where are swivel joints principally used? In branch connections to radiators, and in the risers of multi-story buildings where they are installed between the floor joists. 8 9 Name three grades of American Standard screwed pipe fittings. 125-lb cast-iron, 150-lb malleable iron, and 250-lb cast-iron. 9 9 In what sizes are American Standard cast-iron flanges and flanged fittings for 25-lb saturated steam pressure made? In nominal sizes from 4 in. to 72 in., inclusive. 10 9 What fittings are generally used for threaded connections in low pressure heating systems? Cast-iron. 644 Chapter 35 WATER SUPPLY PIPING AND WATER HEATING Maximum Possible Flow, Maximum Probable Flow, Average Probable Flow, Factor of Usage, Kind of Pipe Used9 Sizing of Risers, Sizing of Mains, Sizing of Systems, Hot Water Supply, Hot Water Heating, Hot Water Storage, Swimming Pool Heating Requirements DOMESTIC water supply systems present the engineer with a design problem that requires combining the somewhat empirical rules and formulae in use with the more or less exact hydraulic principles involved. Unlike heating and ventilating layouts, there are practically no definite data for estimating the quantity of water likely to be consumed or the probable rate of water flow at any particular moment. Metered results in one building often show two or three times the metered amount in another building of the same size and with the same type of tenants. In hotels, one riser will often have an almost constant flow that may never be reached by another at peak load. In office buildings, the women's toilets show a far greater daily consumption than those of the men, yet at no time will they approach the hourly consump tion of the men's toilet during the first hour of the day. This condition has led to a multiplicity of rules of practice which vary as much as the data used. All must of necessity be based on an assumed rate of con sumption and on an assumed probability of simultaneous use, and while the formulae employed may have been derived on sound technical basis the assumptions are often in error. To arrive at a safe standard, the approximate rate of flow of each fixture to be supplied must be known and the probable number of fixtures in use at any one time must be assumed. Obviously, the maximum number of fixtures assumed to be in use must be taken at the peak of demand and the lines must be made adequate to supply such a peak regardless of the riser or branch on which the demand may occur. This means that all water piping under the usual conditions will be over-sized. In tall buildings it is customary to divide the water supply systems, both hot and cold, into sections of 10 to 20 stories. Such zoning1 or lIt is impractical to attempt to size piping so as to produce the proper pressure on fixtures at different levels by employing friction, owing to the fact that this friction will be built.up to the amount desired only Ain times of maximum demand and at all .other times the friction will be only a fraction of the maximum friction so that the fixtures by this.method are subjected to a varying pressure on the water supply line. much more practical method is to throttle the flow at the fixture, or to use flow regulators, so that the Quantity of water delivered will approximate the fixture demands and so' that this is accomplished without splashing or noise. 645