Series 160 Stainless Steel Pitot Tubes Specifications - Installation and Operating Instructions Bulletin H-11 Phone: 219/879-8000www.dwyer-inst.com P.O. BOX 373 • MICHIGAN CITY, INDIANA 46361, U.S.A. Fax: 219/872-9057e-mail: info@dwyer-inst.com The total pressure of an air stream flowing in a duct is the sum of the static or bursting pressure exerted upon the sidewalls of the duct and the impact or velocity pressure of the moving air. Through the use of a pitot tube connected differentially to a manometer, the velocity pressure alone is indicated and the corresponding air velocity determined. For accuracy of plus or minus 2%, as in laboratory applications, extreme care is required and the following precautions should be observed: 1.Duct diameter to be 30 times pitot tube diameter, or greater. 2.Make an accurate traverse per sketch at right, calculate the velocities and average the readings. 3.Provide smooth, straight duct sections a minimum of 8 1/2 diameters in length upstream and 1 1/2 diameters down- stream from the pitot tube. 4.Provide an egg crate type straightener upstream from the pitot tube. Air Velocity = 1096.2 where Pv = velocity pressure in inches of water D = Air density in #/cu. ft. Air Density = 1.325 x where P B = Barometric Pressure in inches of mercury T = Absolute Temperature (indicated temperature °F plus 460) Flow in cu. ft. per min. = Duct area in square feet x air velocity in ft. per min. √ Pv D P B T AIR VELOCITY CALCULATOR Computes velocity based on air density corrected for conditions of temperature and pressure. Eliminates tedious calculations. Ranges from .01 to 10˝ water corresponding to 400 to 20,000 FPM. Furnished with each pitot tube. STAINLESS STEEL PITOT TUBES Test confirmed unity coefficient and lifetime construction of No. 304 stainless steel. Inch graduations show depth of insertion for traversing. Model 160 is designed to meet ASME “Fluid Meters” 6th Ed, ANSI/AMCA 210- 99, ANSI/ASHRAE 51-1999, and British Standard 1042. Sizes 12˝ to 60˝ long. Hand or fixed mounting types. In making an air velocity check select a location as suggested above, connect tubing leads from both pitot tube connections to the manometer and insert in the duct with the tip directed into the air stream. If the manometer shows a minus indication reverse the tubes. With a direct reading manometer, air velocities will now be shown in feet per minute. In other types, the manometer will read velocity pressure in inches of water and the corresponding velocity will be found from the curves in this bulletin. If circumstances do not permit an accurate traverse, center the pitot tube in the duct, determine the center velocity and multiply by a factor of .9 for the approximate average velocity. Field tests run in this manner should be accurate within plus or minus 5%. The velocity indicated is for dry air at 70°F., 29.9˝ Barometric Pressure and a resulting density of .075#/cu. ft. For air at a temperature other than 70°F. refer to the curves in this bulletin. For other variations from these conditions, corrections may be based upon the following data: H-11 8/30/05 3:33 PM Page 1Phone: 219/879-8000www.dwyer-inst.com P.O. BOX 373 • MICHIGAN CITY, INDIANA 46361, U.S.A. Fax: 219/872-9057e-mail: info@dwyer-inst.com ©Copyright 2005Dwyer Instruments, Inc.Printed in U.S.A.8/05FR# 440226-00 Rev.8 AIR VELOCITY IN FEET PER MINUTE GAGE READING WITH PITOT TUBE (VELOCITY PRESSURE) IN INCHES OF WATER GAGE READING WITH PITOT TUBE (VELOCITY PRESSURE) IN INCHES OF WATER AIR VELOCITY IN FEET PER MINUTE H-11 8/30/05 3:33 PM Page 2Next >