Measuring Air Velocity - presented by Lonnie Glen, Kice Industries 2/28/2018. (and why it is important) Applications for Air

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(and why it is important) Wednesday, February 28, 2018 Presented by Lonnie Glen, Kice Technical Sales and Quickship Manager Applications for Air Air Activated

Drying/Cooling Reasons to know how to measure air volumes To know if your equipment is operating efficiently Best operation for the least amount of power Sizing

1 (and why it is important) Wednesday, February 28, 2018 Presented by Lonnie Glen, Kice Technical Sales and Quickship Manager Applications for Air Air Activated Processing Grinders Granulators Hammermills Aspirators Pneumatic Conveying Positive Pressure Vacuum (limited to non fluctuating loads) Dust Control Drying/Cooling Reasons to know how to measure air volumes To know if your equipment is operating efficiently Best operation for the least amount of power Sizing new equipment Dust Collection Aspiration Conveying Important to know when to replace equipment Blowers, Cyclone, Filters, Fans Record keeping Plant operations Government agencies 1

2 Measuring air to determine CFM and STATIC PRESSURE of a dust collection system 3.5 w.c. 1 w.c. 0.7 w.c. 0.5 w.c. 1.3 w.c. 2.5 w.c. 3 OD 5 OD 6 OD 7 OD 8 OD 4 w.c. 0.5 w.c. 3 OD 180 CFM 5 OD 520 CFM 6 OD 750 CFM 10 OD 2425 CFM 4 OD 325 CFM 4 OD 325 CFM 4 OD 325 CFM 12 OD 2425 CFM Sum total of CFM: 2,425 CFM Total of HIGHEST static pressure run of the system: 14 w.c. SP Common terms used in measuring air Pitot Tube Device used to measure static and velocity pressure Air Measuring Kit Tool set containing components to measure air, including Pitot tube, Magnehelic gauge(s), tubing, drill bits, charts, calculator, etc. Pressure Differential Gauge Magnehelic Gauge, Manometer, Spring Gauge, Analog, or Digital device/gauge use to measure pressure differential Velocity Speed of air, measured as Feet per Minute (FPM) Volumetric Air Flow Rate Amount of air typically being moved through the system, measured as Cubic Feet per Minute (CFM) Duct Velocity How fast the air, dust or product flies through the duct, measured in FPM Grain dust typically has minimum of 3400 FPM. Wheat typically conveys at 4200 FPM Typical Air Measuring Kit 2

Magnehelic Gauge High Pressure Connection Total Pressure Connection Pitot Tube Static Pressure Connection Static Pressure Port Total Pressure Port Low Pressure Connection Common terms used in

3 Magnehelic Gauge High Pressure Connection Total Pressure Connection Pitot Tube Static Pressure Connection Static Pressure Port Total Pressure Port Low Pressure Connection Common terms used in measuring air Static Pressure Pressure used to overcome the resistance to flow or. The amount of resistance of friction (including the hood, ducting, product and all other components) And.the energy used to move the product from Point A to Point B Usually the longest, smallest diameter run, but not always Velocity Pressure Pressure required to accelerate the mass of air from rest to its existing velocity or.. Air traveling at a given velocity or. Way to calculate velocity Total Pressure Sum total of static and velocity pressures Area Measurement of the inside of a duct Measured in square feet Vector representation of SP, VP, and TP Pressure Inside of a Duct Reprinted from Industrial Ventilation: A Manual of Recommended Practice for Design, 27 th Edition, published by the American Conference of Governmental Industrial Hygienists TP total pressure = SP static pressure VP (velocity pressure) 3

4 Common Terms Air to Cloth Ratio Establishes design capacity of a baghouse filter Ratio between the total amount of CFM and total area of the filter bags 15,000 CFM / 1,555 sq ft of filter area = 9.65:1 Air to Cloth Ratio Rule of Thumb 7 10:1 for Elevator, Cleaning House, and General Suction 7:1 for Secondary Collectors and High Humidity Air Systems 5:1 for Filter/Receiver, Centro Vacs, and Bin Vents Can Velocity Velocity measured inside the filter (in the open space below the bags) Interstitial Velocity Velocity measured inside the filter (between the filter bags) Basic Formula to determine CFM Q = VA Q = ACFM (Volume of Air) V = Velocity (in feet per minute) A = Tube internal cross-section area (in square feet) Follow a few basic principles Obtain the Velocity of the Air Obtain the Area of the duct/tube/pipe at the point of measurement Multiply Velocity x Area to determine volumetric flow rate Why 5 + pipe diameters downstream of fitting? Air after an, fitting, damper, etc. becomes turbulent Allows air to become laminar or more even inside the tubing/ducting/pipe Makes measurements more accurate Reprinted from Publication (R2007) Air Systems, published by the Air Movement and Control Association International, Inc 4

Right after Right after To short of straight run after Not good location; difficult to measure area LOCATIONS for Air Measurement Reading

5 Typical Air Measurement Reading Points OUTLET SP AND OPTIONAL VP READING OUTLET SP AND OPTIONAL VP READING INLET SP AND VP READING INLET SP AND VP READING OPTIONAL VP READING NOT GOOD LOCATIONS for Air Measurement Reading Points Right after Right after Turbulent flow Right after Right after Right after To short of straight run after Not good location; difficult to measure area LOCATIONS for Air Measurement Reading Points Not good location; right after Good location Good location Not good location; air too turbulent Not good location; air too turbulent 5

6 By the Book Method of Measuring Air for accurate air flow measurements Safety First Select location 10 pipe diameters, if possible, away from dampers, branches, s, etc. Drill 2 holes 90 degrees apart to allow insertion of Pitot tube Connect Pitot tube static and/or total pressure connections to gauge Need to record temperature and absolute pressure Traverse the tube, recording SP ( w.c.) and VP ( w.c.) readings at published insertion depths Take readings in both planes Calculate velocities using each VP reading Average the velocities to determine Average Velocity (V avg ) in FPM Calculate the Tube Area in square feet at the plane the measurements were taken Multiply Velocity by the Tube Area to get CFM Reality Method of Measuring Air for ESTIMATED STATIC PRESSURE Safety First Select location 5+ pipe diameters, if possible, away from dampers, branches, s, etc. Drill hole to allow insertion of Pitot tube Connect Pitot tube SP port to gauge or Put hose perpendicular to the flow over the hole If using Pitot tube, center the tube inside the duct Record the reading on the gauge Reality Method of Measuring Air for ESTIMATED air flow measurements Safety First Select location 5+ pipe diameters, if possible, away from dampers, branches, s, etc. Drill hole to allow insertion of Pitot tube Connect Pitot tube static and total pressure ports to gauge Record the VP at the center of the duct using the Pitot tube Convert Velocity Pressure (V p ) reading to Velocity (V) FPM Refer to chart for Velocity or calculate 4005 x VP (at STP) Multiply the velocity by.9 for 6 OD and smaller duct or by.95 for ducts 8 OD and larger to ESTIMATE Average Velocity (V avg ) Determine Tube Area in Square Feet In Feet: Area of circle = 3.14 x R 2 or.7854 x Diameter 2 In Inches: Area of circle = 3.14 x R 2 /144 or.7854 x Diameter 2 /144 (144 square inches = 1 square foot) Multiply Velocity by the Tube Area to get CFM 6

7 Measuring Static Pressure By the Book Low pressure connection is hooked up Usually the higher reading gauge Zero out gauge Hold gauge level Traverse readings across tube Measure in 2 planes Pitot Tube is into flow Reality Low pressure connection is hooked up Usually the higher reading gauge Zero out gauge Hold gauge level Take center reading Measure in 1 plane Pitot Tube is into flow Velocity Pressure TP (Total Pressure) SP (Static Pressure) = VP (Velocity Pressure) Velocity = 4005 x VP (at STP) Reprinted from Industrial Ventilation, A Manual of Recommended Practice, 22 nd Edition, published by the American Conference of Governmental Industrial Hygienists Measuring Velocity Pressure Reality Both connections hooked up Usually the lower reading gauge Zero out gauge Hold gauge level Measure in 1 plane Pitot Tube is into flow Read VP at center of duct By the Book Both connections hooked up Usually the lower reading gauge Zero out gauge Hold gauge level Measure in 2 planes Pitot Tube is into flow Traverse readings across tube 7

Finding Velocity Example 1: VP reading = 1.1 Velocity = 4200 FPM Example 2: VP reading = 1.75 Velocity = 5298 FPM Example 3: VP reading = 3.

Governmental Industrial Hygienists Finding Volume (Q = V x A) Example 1: Tube = 12 OD and has 0.7854 sq ft area Velocity = 4200 FPM x.95 Average Velocity = 3990 FPM 3990 x 0.

7854 sq ft area Velocity = 7599 FPM x.95 Average Velocity = 7219 7219 x 0.

readings based on Standard Air Typically, we calculate the Air Velocity from the Velocity Pressure. The calculations are correct for standard air conditions (air with a density of 0.075 lbs.

8 Finding Velocity Example 1: VP reading = 1.1 Velocity = 4200 FPM Example 2: VP reading = 1.75 Velocity = 5298 FPM Example 3: VP reading = 3.60 Velocity = 7599 FPM Calculation: Velocity = 4005 x VP (at STP) Reprinted from Industrial Ventilation, A Manual of Recommended Practice, 22 nd Edition, published by the American Conference of Governmental Industrial Hygienists Finding Volume (Q = V x A) Example 1: Tube = 12 OD and has sq ft area Velocity = 4200 FPM x.95 Average Velocity = 3990 FPM 3990 x = Volume of 3,134 CFM Example 2: Tube = 12 OD and has sq ft area Velocity = 5298 FPM x.95 Average Velocity = x = Volume of 3,953 CFM Example 3: Tube = 12 OD and has sq ft area Velocity = 7599 FPM x.95 Average Velocity = x = Volume of 5,670 CFM Reprinted from Industrial Ventilation, A Manual of Recommended Practice, 22 nd Edition, published by the American Conference of Governmental Industrial Hygienists Velocity readings based on Standard Air Typically, we calculate the Air Velocity from the Velocity Pressure. The calculations are correct for standard air conditions (air with a density of lbs. per cubic foot) and based on 70F ambient air temperature, at sea level and a barometric pressure of HG. Correction for actual conditions For conditions different that standard air we need to correct the velocity reading before we calculate to find the velocity and CFM. For this we need to know the Air Density. Typically we need to know the air temperature and elevation to make a correction to the Air Density. VP Calculation: Velocity (V) = x Air density 8

9 Air Density Calculation Calculation: Velocity (V) = 4005 x V = 4005 x of Velocity Pressure V = 4005 x of 1.0 V = 4005 x 1.0 V = 4005 FPM V (avg) = 4005 x.95 = CFM = V x A CFM = x.7854 CFM = 2988 VP Calculation: Velocity (V) = x Air density V = x of Velocity Pressure divided by the Air Density V = x of 1.0 / V = x V = x V = 4291 FPM V (avg) = 4291 x.95 = CFM = V x A CFM = x.7854 CFM = 3201 VP Assumption: 70F and 0 ASL Assumption: 120F and 1350 ASL Known Data compared to Calculated Data Issue/Problem 1: Sum total of air going to a dust collector is measured at 200% of original design. Result: Short bag lift, High air-tocloth ratio; dusting out at points, additional maintenance issues; line plugging? What changed? What was added? What was taken off line? Something open that is not supposed to be open Issue/Problem 2: Air leg no longer has the capacity it used to have. Result: Fan or Air Power Unit is unable to provide adequate static pressure and conveying line cannot handle the load. Allows you a starting point for checking. Fan belts loose or slipping? Motor over amping? Is it the fan rotation? Is the fan speed? Is it fan wear? Is there a choke point? Is there a leak point? Check the Airlock for leakage? Are filters dirty? Issue/Problem 3: Grinder or Mill is getting too hot. Result: Fan may not be providing enough CFM or static pressure to reduce heat at the mill. Allows you a starting point for checking. Has equipment been relocated? Fan belts loose or slipping? Motor over amping? Is it the feed rate? Is it the fan rotation? Is the fan speed? Is there a choke point? Is there a leak point? Check the Airlock for leakage. 9

10 Why is this information important in an Air System? Make system changes for adequate conveying velocity: For example, downstream duct area must roughly equal the sum of the area of the upstream ducts. A system tour can reveal duct branches that may have issues. Take proof of performance airflow and static pressure measurements: These will show whether you have adequate conveying velocity in all system branches at startup and provide a reference point to which you can go back if rebalancing is needed. Keep records of recent routine system measurements AND follow up when out of acceptable : Data history may show which parts of the system typically fail first (for example, plugged s, blinded filter media, or other component) for corrective action before major events. Assign trained personnel responsibility for the system: Allow your personnel the time, tools, and skills to take the data and complete follow up actions. General Good Practices Increase line size as needed to keep good velocity in the line back to the filter Reduces resistance & keeps dust in suspension. Use lockable dampers or slide gates on each connection point AND MARK FOR REFERENCE Use for balancing & lockout to keep from changes being made. Allow Free Air into the system Cannot pull against a dead head or sealed system & makes use of natural air currents. Seal any leaks in the system Will rob the dust collection system of suction to remove dust & many small leaks will add up. Purchase and learn to use an Air Measuring Kit Will let you measure resistance and static pressure, can use to rebalance a system, and gives you some known data to work with. Use care putting Pitot tube in conveying line or heavy dust line. May clog the small ports in the Pitot tube. Good design, Good volume, Good velocity Dust is in suspension because of correct velocities and velocities are correct to minimize wasting HP. 10

BAD design, Good volume, BAD velocity Dust is dropping out (in locations) but system is balanced (at end of system).

Dust build up inside line until area small enough to carry dust at correct velocity. Air taking path of least resistance.

11 BAD design, Good volume, BAD velocity Dust is dropping out (in locations) but system is balanced (at end of system). Additions without rebalancing Dust is NOT in suspension throughout the line System is not balanced. Dust build up inside line until area small enough to carry dust at correct velocity. Air taking path of least resistance. Deductions without rebalancing Dust is in suspension (but at higher velocity) System is balanced (but not correct) May be picking up good product. System works but wasting energy (HP). Once you are done measuring the air Leaving the drilled hole open Usually not so large as to effect the system Can be a point where foreign material can enter Covering the drilled hole Closes a leak point Does not allow foreign material to enter Marking the drilled hole Air Measurement label/magnet Leaves info for next person Self tapping screw Rubber plug Dab of silicone/caulking Duct tape/hvac tape Air Measurement label/magnet 11

12 Closing Comments It is not difficult to take air measurement reading with the correct tools. It can help you in dealing with the manufacturer and minimize any downtime. The information the air readings provide can: Benefit product quality Benefit in product recovery Extend equipment life Save energy Reduce emissions Reduce housekeeping Keep the plant running and out of trouble Thank you for the opportunity to speak today Contact information: Lonnie Glen; / Ph:

NJ AIHA CIH Review Industrial Ventilation

NJ AIHA CIH Review Industrial Ventilation Thomas Block, CIH MPH tblock@aps.rutgers.edu 848-445-2550 2016 American Industrial Hygiene Association, New Jersey Section, Inc. Course Objectives At the end of