IT STARTS AT THE SOURCE - RE-CALIBRATING YOUR PLANT METERS NYS AWWA Spring Conference Saratoga Springs, New York April 25, 2017 Robert Lucas, P.E.
WHAT ARE WE TALKING ABOUT? Types of Flow Measuring Devices (Primary Elements) Orifice Plates Venturi Tubes ie. PFS, B-I-F Insert Propeller Meter Mag-meter & Ultrasonic Flow Nozzle
WHERE ARE THEY USED? Well Heads deep vertical turbine Horizontal Split-case Booster GST Reservoir Clearwell Boosters short-coupled VT Transfer pumps 3
HYDRAULIC PRINCIPLE OF PRIMARY ELEMENT Based on Differential Pressure measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full think manometer Bernoulli's principle states that there is a relationship between the pressure of the fluid and the velocity of the fluid. When the velocity increases, the pressure decreases and vice versa. 4
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DIFFERENCES BETWEEN ELEMENTS Orifice Plate Inexpensive Small Footprint Higher head loss due to turbulence (energy loss) Venturi Tube Higher Cost Large Footprint - inside / vault used outside Much more efficient / less pressure loss Straight pipe upstream/downstream very important! 11
PREFERRED DESIGN - VENTURI TUBE Reduced pressure loss Fluid can flow with much higher velocity without turbulence Curved, streamlined section, long & gradually expanding downstream xx% more flow than orifice plate 12
SECONDARY ELEMENTS Differential Pressure Gage with Switch Still used to satisfy safety Set min. value confirms flow (reads inches of water ) Pressure Transmitter (digital) interprets DP Digital Processor part of pressure transmitter PLC: Programmable Logic Control software Digital Display Chart Recorder SCADA - Remote Monitoring & Control 13
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SO WHY DO WE NEED ACCURATE FLOW MEASUREMENT? To determine total quantity of fluid pumped Know your system outflow Accurately determine non-revenue water Ensure Accuracy & Performance of your equipment Selling or purchasing water Accurate treatment & equipment safety Safety Interlock / Chemical Safeties Used for chemical dosing on variable flow applications (flow pacing) 16
WHY CALIBRATION? All elements can & will develop error and need to be checked Exposure over time due to: Temperature fluctuations Humidity Vibration Pollutants / chemicals Everything wears : Sensing elements Diaphragms Gages 17
WHY CALIBRATION? What can go wrong? Wear in the throat of the Venturi Tube Clogs in the sending lines Iron & Manganese Minerals / Calcium Air!! - very common * must keep the main flooded [after the check valve is best ] 18
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CALIBRATION HOW OFTEN? AWWA recommends source metering to be calibrated annually Nov Feb: good time of year due to low pumpage in the off season January: start the year off right 21
CALIBRATION - WHY IT S IMPORTANT Verify proper equipment performance & that it is operating satisfactorily Getting a pulse of your system Planning for maintenance or capital improvements Pump Efficiency / Wear Efficiency = $$$ 22
CALIBRATION Employ services of a reputable controls contractor Check the elements starting at the pressure transmitter Problems most often occur in the PD gage or transmitter Typically flow is checked with calibrated DP gage & hand pump Isolate components and connect calibrated gage & hand pump Pump up to obtain various DP values Compare each DP value of DP gage to that of pressure transmitter Verify value to Calibration Chart / Flow Sheet / Design Table Every model VT has its own calibration chart Inches of water = flow in GPM MUST use digital process calibrator HART protocol 23
CALIBRATION A quick double-check of flow accuracy is also employed using a calibrated clamp on Ultrasonic Flow Meter UFM used when pump is running and measuring system flow 2-3% difference in results compared to calibrated components is acceptable 25
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CALIBRATION The 4-20 ma signal is then checked as it continues to the subsequent components in the system. To and through the PLC > > > output display Digital display Chart recorder SCADA modules.. Via graphical user interface The value may have to be adjusted / tweaked at each component to maintain accuracy Otherwise a compound of error will result 28
CALIBRATION Historical Data can be very helpful when calibrating: Can see what readings and GPM you had last time Confirm last calibration date and degree of error Prudent designs incorporate multiple transmitters to maximize accuracy Small span/wide range for low flow & larger span for high flow 29
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CALIBRATION Industry standardizing on open universal protocol that converts DP to 4-20mA electronic signal - HART Protocol In years past, the each manufacturer had their own calibration protocol for calibrating the pressure transmitter Rosemount Foxboro ABB Endress + Hauser Honeywell 31
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VENTURI LOCATION OPTIONS Inside the plant if you have the room Outside in a vault if limited space inside IMPORTANT: proper installation requires straight length pipe upstream & downstream of the element Typically 10 pipe diameters upstream 5 pipe diameters downstream 33
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IMPROPER CALIBRATION If your controls contractor asks you what s your pump putting out and then starts adjusting the transmitter, ask him/her to leave and call another contractor. This is not calibrating, its guessing! If the readings are bouncing the sensing lines must be flushed & purged 36
TAKE-AWAY THOUGHTS Budget calibrations annually but if something doesn t look right, don t wait Employ a reputable controls contractor For revenue reasons don t be afraid to explore the reality of meter error when it comes to your top 10 or 25 users explain / examples 37
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IT STARTS AT THE SOURCE - RE-CALIBRATING YOUR PLANT METERS Presented by: Robert J. Lucas, P.E. 538 Broad Hollow Road, 4 th Floor East, Melville, New York 11747 t 631.756.8000 f 631.694.4122 11 Computer Drive West, Suite 102, Albany, New York 12205 t 518.621.7558 f 518.621.7658 254 South Main Street, Suite 500, New City, New York 10956 t 845.499.2264 f 845.499.2265 119 Cherry Hill Road, Suite 200, Parsippany, New Jersey 07054 t 862.207.5900 f 973.334.0507 www.h2m.com