Product/Fact Sheet0 pages

41061_Dekker Medical TriFold table.main {} tr.row {} td.cell {} div.block {} div.paragraph {} .font0 { font:6.00pt "Arial", sans-serif; } .font1 { font:7.00pt "Arial", sans-serif; } .font2 { font:8.00pt "Arial", sans-serif; } .font3 { font:9.00pt "Arial", sans-serif; } .font4 { font:10.00pt "Arial", sans-serif; } .font5 { font:13.00pt "Arial", sans-serif; } .font6 { font:17.00pt "Arial", sans-serif; } .font7 { font:36.40pt "Arial", sans-serif; } .font8 { font:9.00pt "Microsoft Sans Serif", sans-serif; } .font9 { font:30.00pt "Microsoft Sans Serif", sans-serif; } .font10 { font:34.00pt "Microsoft Sans Serif", sans-serif; } .font11 { font:43.00pt "Microsoft Sans Serif", sans-serif; } DEKKER VACUUM TECHNOLOGIES, INC. "THE VACUUM FACT SHEET" ow to convert SCFM to ACF Vacuum Conversion Tabl Example: Convert 20 SCFM of air to ACFM at a vacuum level of 25"Hg (inches of mercury) at sea level. (For effect of lvation see lower section of page) First, convert 25"Hg gauge vacuum to "HgA (inches of mercury absolute) Atmospheric pressure is 29.92"Hg (P,) P2 = 29.92 - 25 = 4.92"HgA 驩quivalent to 125 torr (mmHg) SCFM = cubic feet per minute at standard temprature and pressure (STP) (68° F, 14.7 psi or 29.92"Hg) ACFM = cubic feet per minute at actual vacuum pump inlet To dtermine the pump flowrate in ACFM, we use Boyles Law (P,V, = P2V2), where P, - Atmospheric pressure at sea level (standard STP) P2 - Pump inlet pressure "HgA V, - Initial volume V, - Final volume Solving for V2: V2 = (P,V,)/P2 or (P,/P2) x V, V2 = (29.92/4.92) x 20 = 121.6 ACFM Torr mbar "HgV "HgA psia % vac. 760 1013.00 0.000 29.921 14.696 0.00 750 999.67 0.394 29.527 14.503 1.32 700 933.03 2.362 27.559 13.536 7.89 600 799.74 6.299 23.622 11.602 21.05 500 666.45 10.236 19.685 9.668 34.21 400 533.18 14.173 15.748 7.737 47.37 380 506.50 14.961 14.961 7.348 50.00 300 399.87 18.110 11.811 5.801 60.53 200 266.58 22.047 7.874 3.867 73.68 150 199.93 24.016 5.905 2.901 80.26 100 133.29 25.984 3.937 1.934 86.84 90 119.96 26.378 3.543 1.740 88.16 80 106.63 26.771 3.150 1.547 89.47 70 93.30 27.165 2.756 1.354 90.79 60 79.97 27.559 2.362 1.160 92.11 50 66.64 27.953 1.968 0.967 93.42 40 53.32 28.346 1.575 0.773 94.74 30 39.99 28.740 1.181 0.580 96.05 25.4 33.86 28.921 1.0000 0.491 96.66 20 26.66 29.134 0.7874 0.387 97.37 10 13.33 29.527 0.3937 0.19337 98.68 7.6 10.13 29.622 0.2992 0.14696 99.00 1.00 1.3329 29.882 0.0394 0.01934 99.87 0.75 0.9997 29.891 0.0295 0.01450 99.90 0.50 0.6664 29.9013 0.01968 0.00967 99.9342 0.10 0.1333 29.9171 0.00394 0.00193 99.9868 0.01 0.0133 29.9206 0.00039 0.00019 99.9987 0.00 0.0000 29.9210 0.00000 0.00000 100.0000 Evacuation of a closed vessel Example: The volume of a closed dry tank is 750 cubic feet including Connecting piping. Atmospheric pressure is 14.7 psi (29.92"Hg). D驩termine the required pump capacity to evacuate the vessel down to 24"Hg in 3 minutes. Q = V x Ln (P,/P2) In which Q = total volume to be removed V = volume of tank and piping P,= initial pressure P2= final pressure Solution: P, = 29.92"HgA P2 = 24"Hg or 5.92"HgA Ln(P,/P2) =Ln(29.92/5.92) = Ln(5.05) = 1.62. Therefore, Q = Vx 1.62 = 750fPx 1.62 = 1,215 ft3 The required vacuation time is 3 minutes. Required pump capacity = 1,215 ft3/3min = 405 ACFM. Select a vacuum pump with an average capacity of at least 405 ACFM. Capacity Loss* Formulas PROCESS VACUUM LEVEL "Hg CAPACITY LOSS AT INLET PRESSURE DROP 1"Hg 2"Hg 3"Hg 4"Hg 15 7% 13% 20% 27% 20 10% 20% 30% 40% 24 17% 33% 50% 66% 26 25% 50% 75% 100% 28 50% 100% - - Torr (mmHg) = 760-("HgV x 25.4) = "HgA X 25.4 = psia x 51.7 = mbar x 0.75 "HgVacuum = 29.92 - (mmHg/25.4) = 29.92 - "HgA = 29.92 - (psia x 2.036) = 29.92-(mbar x 0.0295) "HgAbsolute = mmHg/25.4 = 29.92 - "HgV = psia x 2.036 = mbar x 0.0295 "wc Vacuum = "Hgx13.6 Temprature Conversion °C = (T - 32) x 5/9 or (T - 32)/1.8 °F = (°C x 9/5) = 32 or (°C x 1.8) = 32 Temp驩rature Rise across a liquid ring vacuum pump ^T _ 42.4 x BHP in which: BHP = brake horse power (HP) q x 8.34 x SG x Cp q = seal fluid flow rate (GPM) SG = spcifie gravity of seal fluid Cp = spcifie heat of seal fluid Conversion formulas CFM - m3/hr To convert from rnVhr to CFM, multiply by 0.59 To convert from CFM to m3/hr, multiply by 1.7 'Due to improper inlet pipe sizing or poorly maintained inlet filters (at sea level) Absolute pressure ("HgA) 29.92 27 24 21 18 15 12 Altitude (in thousands of feet) O Ol O Ol O Ol / / f / r y 760 675 600 525 450 375 300 Absolute pressure (Torr) ltitude effect Performance curves for vacuum pumps are always derived relative to atmospheric pressure at sea level. When a vacuum pump op驩rtes at altitudes higher than sea level, the atmospheric pressure decreases. The important thing to remember when you encounter applications at altitude, is to measure the vacuum level relative to barometric pressure. Please see the example below to see how this affects the calculation of vacuum level. As a quick rule of thumb, you can assume that for each increase of 1,000 feet of l⩩vation, the barometric pressure will decrease by 1 "Hg. Example: The installation site is located in Denver, Co (lvation - 5,000 feet). A capacity of 750 ACFM at 20"Hg gauge is required for the application. The question is, what is the 驩quivalent vacuum level at sea level. Solution: Use the following formula tocalculate the quivalent vacuum level. 29 92 P, = P, x p in which P鄄, = quivalent vacuum level at sea level 2 P2 = barometric pressure at altitude = 25.3"HgA (from chart) P, = P2 - required vacuum level at altitude = 25.3"HgA- 20"Hg = 5.3"HgA P, = 5.3"Hg = 6.3"HgA or 23.4"HgV (29.92 - 6.3) (sea level 鄩quivalent) 25.3 Therefore, select a pump with a minimum capacity of 750 ACFM at 23.4"HgV. 935 SOUTH WOODLAND AVENUE, MICHIGAN CITY, IN 46360-5672 TOLL-FREE: 888-925-5444 TEL.: 219-861-0661 FAX: 219-861-0662 www.dekkervacuum.com Copyright © 2005 Dekker Vacuum Technologies