Document J3mm2jKNQojDMrOGa61O8k6VZ

f ; American Society of Heating and Ventilating Engineers Guide, 1925-26 RESULTS OF LABORATORY EXPERIMENTS The Research Laboratory of the American Society Heating and Ventilating Engineers has investigated this subject1, and has found the critical velocity for quiet operation to be about .22 in. per second for the sizes of pipe investigated and apparently increasing with the size of pipe. The maximum velocity, however, with counter flow of condensate where noise is not objectionable is considerably higher and increases rapidly with size of pipe. In the case of horizontal runs both the critical velocity for quiet operation and the maximum velocity where noise is not objectionable, depend upon the pitch of the pipe. The maximum capacity and velocity where noise is not objectionable for horizontal pipes with various pitches are given in Table 44. N u m Bcr ^o+ Rise r 4 ______ a_______ Dianv +ci^< fr^PlD o+ Point bottofnj Too Bottom | Too & p 3!Sqwored Errtnne 5 % 2 A f A 6 c A i iA lit it! g 3 in AA Too AA ftarod & i i i& A ti iA A i iA iA A A &A til A A A A A & Bbundd iA A1s A A w A kl Tbrr* r iA 7 | h----- ^oimred Cktramcc Eeamcd Entrance I*1' Qounco Entrance ^ 5&X-UI.IWWM iM OurftnCAnuworiMninmes. pATr.scrttfc-'u pgVift to. sFig. 22. Effect of Reaming Entrance to One-Pipe Risers Where the velocity of steam is the limiting factor of the capacity of a pipe, care must be taken that this velocity is not exceeded in any part of the pipe or fittings by a constriction, since the velocity at any one con striction will limit the whole system. For this reason, particular care must be taken to ream such pipe and guard against dope constricting it at joints. Iron pipe should also be examined for constricting blisters, Fig. 22 and Table 46, from the Laboratory reports already mentioned show the importance of these factors. t Reports by Houghten & Ehin, Journal Ambrican Society of Heating and Ventilating Engineers, September, 1922; March, 1923; February, 1924; June, 1924; February. 1925. 68 - American Society of Heating and Ventilating Engineers Guide, 1925-26 Table 44. Maximum Capacity of One-Pipe Lines at Various Pitches Pitch of Pipe in Inches per 10 Ft. Pitch of Ptf--in. X IN. 1 IN. IX in. 2 IN. 3 in. . 4 IN. 5 IN. Pipe' Sue' Sq. Ft Rad. Based on 240 B.tu. t 3 2 Sq. Ft Rad. Based on 240 B.to. Sq. Ft i- Rad. 1 2 Based on 240 B.tu. 1 3 2 Sq. Ft Rad. Based on 240B.tu. 3 2 Sq. Ft. Sq. Ft Rad.. S' Rad. Baaed on 240. MS3 Based on 240 B.tu. 2 . B.tu. *< 0 2 Sq. Ft Rad. on 240 B.tu. > 3 2 Sq. Ft Rad. on 240 B.tu. :> 3 2 y*' \r . l x0 \w 2" 25.0 45.8 104.9 142.6 236.0 12 12 18 18 19 30.3 14 52.6 15 117.2 20 159.0 21 263.5 .20 37.3 63.0 133.0 181.0 299.5 18 17 23 23 23 40.4 70.0 144.5 196.5 325.5 19 20 25 25 25 42.5 75.2 154.0 209.3 346.5 20 22 27 27 27 46.1 83.0 165.0 224.0 371.5 21 23 28 28 28 47.5 87.9 172.6 234.8 388.4 22 25 29 30 29 49.3 90.2 178.2 242.6 401.1 23 26 31 31 30 Table 45. Results of Tests on Angle and Globe Valves Nominal Size op Pipe In. . Vi 1 Hi IK Area of Pipe Sq. in. 0.537 0.835 1.459 1.927 Area Valve Seat Opening Sq. In. Per Cent of Area of Pipe 0.4418 0.822 1.258 1.773 - 82.2 98.4 86.2 92.2 Maximum ' Pipe and Valve 9.68 22.10 30.00 46.13 Capacity Pipe Alone Per Cent of Capacity of Pipe Alone 13.52 23.30 47.5 68.5 71.6 95.0 63.1 67.4 Nominal Size In. k .1 IK IK -Valve Stem--Vertical Capacity of Pipe and Valve Lb. per Hr. 1.38 7.73 13:20 18.81 Per Cent of Capacity of Pipe Alone 11.8 35.7 31.2 33.0 Valve Stem--Horizontal Capacity of Pipe and Valve Lb. per Hr. 8.83 14.06 22.88 32.00 Per Cent of Capacity of Pipe Alone 76.3 66.1 54.3 56.7 The capacity of risers with various shaped entrances is very important and those shown in Fig. 22 gave the following maximum capacities:-- Reamed entrances......v....................... 24,7 lb. per hr. Rounded entrances.--.......................... 23.9 lb. per hr. Squared entrances............................... 22.2 lb. per hr. Three wheel cutter._........................... 19.2 lb. per hr. Single wheel cutter.--.......................... 17.6 lb. per hr. Per Cent Decrease 0.0 3.2 10.1 22.2 28.7 Table 46 shows variation in capacity of a pipe as affected by variation of size and smoothness of pipe generally found on the market. The maximum and minimum results were obtained by picking out very smooth and very rough pipe from the stock room of a large manufacturer. Table 46. Per Cent Difference in Capacity Due to Variation of Pipe Size ______________ and Smoothness Capacity of Pipe....................................... Minimum. ................. Maximum.. . Per Cent Variation...... ........................... Maximum Condensation. Lb. per Hr. K" 14.00 15.20 8.6 1" 24.89 30.08 20.8 IK' 45.42 52.08 14.7 IK' 70.50 82.00 16.3 69