Document 3egrzQMoaYdgb3q8QZ6Nz4jQ3

1016 CHAPTER 48 1952 Guide FRICTION LOSS IN HEAD IN LBS. PER SQ. IN PER IOO FT. LENCTH Water Services FRICTION LOSS IN HEAD IN LBS. PER SQ. IN. PER IOO FT. LENCTH 1017 . Fig. 3. Flow Chart for Copper Tubing pressure required for the operation of the topmost fixture. (A pressure of 15 psi is ample for flush valves, but reference should be made to the maniifacturers' requirements. A minimum of 8 psi should be allowed for other, fixtures.) The pressure differential thus obtained will be available for.'overcoming pressure losses in the distributing system, and in'tovercoining the difference in elevation between the water main and the highest fixture. . Hie:pressure loss, in pounds per square inch, caused by the difference in elevation between the street main and the highest fixture, may be ob tained .by multiplying the difference in elevation in feet by the conversion factor 0.43. When water flows through a pipe, friction occurs as the result of the sliding of water particles past one another. If the pipe wall' is rough, the roughness projections cause additional friction, owing to the develop ment of increased turbulence in the flowing water. As the water flows along a uniform pipe, the pressure decreases as a result of a dissipation of Fig. 4. Flow Chart for Fairly Rough Pipe energy arising from the internal friction set up by viscosity of the water. This loss in energy is shown by the loss of pressure. The pressure loss is proportional to the length of straight .uniform pipes, and varies greatly with flow velocity, pipe diameter, and roughness of pipe. On the basis of inside surface conditions, pipes may be classified^ as smooth, fairly rough and rough, as follows: Smooth. The pipe surface shows no perceptible roughness. Pipes' made*'of . copper, brass, or lead may usually be classified as smooth. 15 Fairly Rough. All ordinary pipes, such as wrought iron, galvanized iron, steel and.cast-iron', after a few years of usage, may be called fairly rough. .. - Rough. Pipes that have deteriorated fairly rapidly for some 10 or 15 years after being laid, are classified as rough. 'f . ' I Figs. 3, 4 and 5 give the pipe friction losses corresponding to these three types of pipes for various nominal diameters.1 Example 1: A 2J in. fairly rough pipe supplies 100 gpm of water. Find the fric tion loss in head if the pipe length is 200 ft.