Effect of Fittings. - The reduction of pressure produced by elbows, tees and globe valves may also be stated in an equivalent length of straight pipe. The following table (National Tube Co.) gives the additional length required to equal the friction due to globe valves. For elbows and tees, take two-thirds of the length given in the table. I 12 2 3 4 5 6 8 ΤΟ 12 15 18 24 2 4 7 13 20 28 36 53 70 88 115 143 Loss of Pressure in Pounds per Square Inch of Air at 80 Pounds Gage Size of Pipe (Ingersoll-Rand Co.) Delivery in Cubic Feet of Compressed Air per Minute at 80 Pounds Gage 200 7.74 11.3 15.2 19.4 23.2 27.2 31.0 38.7 46.5 62.0 Equivalent Delivery in Cubic Feet of Free Air per Minute Delivery in Cubic Feet of Compressed Air per Minute at 80 Pounds Gage 3.83 5.61 9.86 1000 1500 2000 2500 3000 4000 5000 15.41 Ο. ΟΙ Ο. ΟΙ 0.02 0.04 0.07 0.02 0.03 0.01 Care of Pneumatic Hammers. The life of pneumatic hammers can be greatly prolonged, and the necessity for making repairs largely eliminated, by keeping the working parts clean and well lubricated. It is a good plan to occasionally submerge the hammer in a bath of benzine for a few hours, and then blow it out under pressure to dislodge any foreign matter that may have entered. Before using the hammer, the working parts should be lubricated with a good quality of light machine oil. The source of pneumatic hammer troubles is sometimes in the pipe line. The moisture in the air rusts the pipes, and if a hammer is connected without first blowing out the pipes, the sediment is liable to enter the working parts and cause the valve or piston to stick. Rubber also deteriorates rapidly, and particles of the hose may blow into the valve box and interfere with the operation of the hammer. The use of a poor grade of heavy-bodied oil will also cause the ports to become clogged and render the hammer inoperative. In such cases, it is a good plan to clean the working parts by injecting a liberal quantity of benzine through the throttle handle, as this dislodges the foreign matter and "cuts" the thick oil, which can then be removed by blowing air through the hammer. The use of strainers or filters attached to the hammer or placed in the supply pipe are to be recommended. Perhaps the most serious abuse to which riveting hammers are subjected is the use of short pistons. When the length of the piston is reduced, the hammer delivers a more rapid blow and, for a time, facilitates the work; hence workmen sometimes substitute short pistons to increase their output, especially when working on a piece-work basis. Short pistons are objectionable as they tend to crumble, and the broken parts will cut the inner casing of the cylinder. If the latter is not damaged beyond repair from this cause, it is soon cracked or the hammer is otherwise broken. Pneumatic Hammer Capacity and Air Consumption * * Chicago Pneumatic Tool Co. † Air consumption based upon an air pressure of 80 pounds per square inch. PRESSURES AND FLOW OF WATER Water Pressures. - Water is composed of two gases, hydrogen and oxygen, in the ratio of two volumes of the former to one of the latter. Water boils under atmospheric pressure at 212 degrees F. and freezes at 32 degrees F. Its greatest density is at 39.1 degrees F., when it weighs 62.425 pounds per cubic foot. The pressure in pounds per square inch of water that is not moving, against the sides of any pipe, vessel, container or dam, is due solely to the "head," or height of the surface of the water above the point at which the pressure is considered. The pressure is equal to 0.433 pound per square inch for every foot of the head, at a temperature of 62 degrees F. For higher temperatures, the pressure slightly decreases in the proportion indicated by the table "Weight of Water per Cubic Foot at Different Temperatures." The pressure per square inch is equal in all directions, downwards, upwards and sideways. Water can be compressed only in a very slight degree, the compressibility being so slight that even at the depth of a mile, a cubic foot of water weighs only about one-half pound more than at the surface. Pressure in Pounds per Square Inch for Different Heads of Water 20 1.30 1.73 2.16 2.60 3.03 3.46 3.90 30 40 50 0.43 0.87 4-33 4.76 5.20 8.66 9.09 9.53 12.99 13.42 13.86 14.29 14.72 15.15 15.59 16.02 16.45 16.89 17.32 17.75 18.19 18.62 19.05 19.48 19.92 20.35 20.78 21.22 21.65 22.08 22.52 22.95 23.38 23.81 24.25 24.68 25.11 25.55 60 25.98 26.41 26.85 27.28 27.71 28.14 28.58 29.01 29.44 29.85 30.31 30.74 31.18 31.61 32.04 32.47 32.91 33.34 33-77 34.21 80 34.64 35.07 35.51 35.94 36.37 36.80 37.24 37.67 38.10 38.54 38.97 39.40 39.84 40.27 40.70 41.13 41.57 42.00 42.43 42.87 9 9 9 9 98 P 8 9 70 90 Heads of Water in Feet Corresponding to Certain Pressures in Pounds per Square Inch 23. I 20 46.2 30 40 92.4 94.7 2.3 4.6 6.9 9.2 11.5 13.9 25.4 27.7 30.0 32.3 34.6 36.9 39.3 41.6 43.9 48.5 50.8 55.4 57.7 60.0 62.4 64.7 67.0 69.3 71.6 73.9 78.5 80.8 83.1 85.4 87.8 90. I 97.0 50 115.5 117.8 120. I 53. I 76.2 99.3 101.6 103.9 106.2 108.5 110.8 113.2 122.4 124.7 127.0 129.3 131.6 133.9 136.3 60 138.6 140.9 143.2 145.5 147.8 150.1 152.4 154.7 157.0 159.3 70 161.7 164.0 166.3 168.6 170.9 173.2 175.5 177.8 180. 1 80 90 182.4 184.8 187.1 189.4 191.7 194.0 196.3 198.6 200.9 203.2 205.5 207.9 210.2 212.5 214.8 217.1 219.4 221.7 224.0 226.3 228.6 |