NUFLO DP Cone Meter User Manual
Contents
1. 20 Transmitter Calibration ec E Ope e eap Du ede HR Te Y EP aged 21 Section 4 Meter Installation for Gas 23 Installation Options oer Sa wheel nine ee ed ee ie 23 Meter aed ent ee tec A euet et opere er reet eee et lain ain late edie 23 Impulse Tube Orientation u ceinture e ena td cene rete i a decid 23 Condensate Chamber Drip Pot nennen nemen a 23 Horizontal Meter Installation a a 23 Drip Pot Installation Optional for Wet 2 24 Vertical Meter Installation amit a 25 Transmitter Calibrati n uuu 22e nl ie eee eA ee 26 April 2007 Page iii Table of Contents Section 5 Meter Installation for Steam u u 27 Install tiori ODptlOns Z SQ uum m u 27 Meter Orl ntaltloFi s coe Samana Re ayaq 27 Impulse Tubing Orlerntation2. 27 Condensate Chamber uuu Sandee 27 Horizontal Meter Installation crie ret 28 Installation 45 u a Quay au 29 Transmitter Calibration o eco ERROR ERRARE 30 Section 6 System Modifications U UU U u uu uu u 31 552 He 31 Gauge Line Emons cite 1255 31 Elevation and Temperature Effects in Piping n 31 Appendix A Flow Measurement Theory and Equations A 1 Berrnoulli Princlple 55612855 aaa A 1 Table of Contents Page iv April 2007 Section 7 General Description and Specifications Introduction The NuFlo Differential Pressure Cone Meter is a process control and multi fluid meter that uses differential pressure to provide accurate repeatable and cost optimized measurement solutions The NuFlo Cone Meter produces a differential pressure which is read by a differential pressure or multi variable transmitter The NuFlo MVX II multivariable transmitter and the NuFlo Scanner 2000 microEFM which feature an integral mul
3. M 12 Pipe Lengthand Configuration u EA 13 Extreme Temperature 13 Best Practices for Installing the NuFlo Cone Meter eee 14 Flow R n Bequirements 5 2 rere reo ce 14 Meter Orientation and Transmitter Position r 14 T ones aa R 14 Impulse NUDING RN 15 Installation Checkpoints for the Transmitter n 16 Section 3 Meter Installation for Liquid Service U U 17 1 1 1 10191512 5 tct u teni 17 Meter Orientation mc nen teo EG BM URBI 17 Pipe Orientatloni 5 mentio bte PII i BU Ep 17 Wall ADS PCI HT 17 Condensate Chamber Drip L aun nennen mener entere nnns 17 Horizontal Meter Installation I nsn 17 Bubble Pot Installation Optional U emen 18 Vertical Meter Installation na nns 19 Vertical Meter with Wall Taps
4. _ 102 7884 85 845 poled 0 5500035 ps ic 1 1 04915 1 8 1 0 5500035 Y 1 0 649 0 696 p gt i k P N 13 1 0 649 0 696 x 0 5500035 16 11066 0 99934 EvY BD AP 0 0000351241 0 8217 x 1 04915 0 99934 0 5500037 102 7884 X 56 1388 x 13 qm 2 6127 sec 9405 85 kg hr April 2007 Page A 13 Appendix A Sample Calculation 3 Natural Gas The same meter is measuring natural gas consisting of 97 methane 2 propane and 1 iso butane The flowing pressure is 700 psi absolute the flowing temperature is 84 F and the differential pressure is 73 inH2Ogo Find the flow rate in MMSCFD corrected to contract base conditions of 60 F and 13 60 psia Apply a diameter correction and neglect the meter factor Molar mass Eqn 1 Tables 1 amp 4 Mr 0 97 x 16 042 0 02 x 44 096 0 01 x 58 122 17 02388 At 700 psia and 84 F the compressibility factor according to AGA 8 is Zp 0 911979 At base conditions 60 F and 13 6 psia Z 0 997922 _ 17 02388 x 700 _ 3 Do Z RT 0911979 x 10 73164 x 84 45968 22265 Ibm fi _ _ 17 02388 x 13 6 3 ZRT 0 997922 10 73164 60 459 67 Diameter correction Eqn 7 8 Table 5 D D 1 o T T 4 026 1 0 00000925 84 68 4 0265495848 in 1 0 T T 3 362 1 0 00000925 84 68 3 362
5. esee 5 1818161911 efe M P PEE 5 mtn nein ptite tiet intu iere 5 Meter Components sete iis dH tr necne tad uite edes 5 Priniciples of Operations x deitatis eiae sided 6 ted er v Det ld eerte ela mie ede 8 Section 2 General Installation Guidelines U U u u u 9 Important Safety 2 SS asa 9 Unpacking the L u t o u Qiz s 9 Assembling the System eka S 9 System uuu 10 Differential Pressure Transmitter 11 ohuteOff Valves wis n unt bae eb eit bd freu e Lese Ite 11 bEi duaeirmee M 11 Thermo well or Thermocouple aa 12 Process Piping TARAA 12 Impulse TUBING 226 166 0 12 Pipe Material
6. The direction of flow is also indicated on every nameplate for easy reference during installation of the meter NUFLO CONE METER FLOW mj Model No DPC Serial No Tag No Meter ID in Beta Ratio Cone OD in Cd Measurement Systems CAMERON Houston TX 1 281 582 9500 Figure 1 3 Sample nameplate Section 1 Page 8 April 2007 Section 2 General Installation Guidelines Important Safety Information Installation inspection and maintenance of the NuFlo Cone Meter must be performed by authorized and trained personnel who have a working knowledge of piping configurations Never open a manifold valve or flange unless you have first verified that the system is completely depressurized WARNING During liquid or wet gas service open valves very slowly to avoid slugging in the meter run Always use proper procedures and equipment for lifting and moving the NuFlo Cone Meter to avoid risk of injury Secure all connections properly before starting up a system Keep a safe distance away from the process upon startup Be mindful of static electricity generated by insulated footwear etc and always ground yourself before touching pipes in the hazardous area where flammable gas is being metered Unpacking the Meter All NuFlo Cone Meters are securely packed to help prevent damage during shipment Inspect the packing list on receipt of the device and report any discrepancies immediately Assembling the
7. CAMERON Measurement Systems NUFLO M Differential Pressure Cone Meter User Manual Manual No 85165000 Rev 01 Important Safety Information Symbols used in this manual This symbol identifies information about practices or circumstances that can lead to personal injury or death property damage or economic loss This symbol indicates actions or procedures which if not performed correctly may lead to personal injury or incorrect function of the instrument or connected equipment Terms used in this manual Note Indicates actions or procedures which may affect instrument operation or may lead to an instrument response which is not planned Technical Support Contact Information Cameron Measurement Systems 14450 John F Kennedy Blvd Houston TX 77032 Phone 1 800 654 3760 281 582 9500 Fax 281 582 9599 NuFlo is a trademark of Cameron International Corporation Cameron Copyright 2007 Cameron International Corporation Cameron All information contained in this publication is confidential and proprietary property of Cameron Any reproduction or use of these instructions drawings or photographs without the express written permission of an officer of Cameron is forbidden All Rights Reserved Printed in the United States of America Manual No 85165000 Rev 01 April 2007 Table of Contents Section 1 General Description and Specifications
8. 0997424 x 0 8217 1 0492 x 0 9979 x 0 55014 x 4 026595848 x 2 23965 x 73 5 3843266 lbm sec Reynolds Number Eqn 17 Table 9 _ _ 227375 5 3843266 _ Re uD 0 01062 x 4026595848 28029354 Interpolation Eqn 18 The adjacent Reynolds numbers from the Meter Factor table are 2290500 at MF 1 0006 Rens 2912750 at MF 0 9968 _ _Re Re 2862935 2290500 2912750 2290500 Adjusted mass flow rate Eqn 19 x MF 5 3843266 x 0 9971 5 3687 MF x 0 9968 1 0006 1 0006 0 9971 Appendix A Page A 16 April 2007 Volume flow rate at base conditions Eqn 3 Table 4 _ qm _ 7 64109455 _ 3 3 2 004100 183 6757 std ft sec 15869584 12 std ft Iday 11 15 MMSCFD References 1 American Gas Association AGA Report No 3 Part 1 Orifice Metering of Natural Gas Part 1 General Equations amp Uncertainty Guidelines AGA catalog XQ9017 1990 2 American Gas Association AGA Report No 7 Measurement of Natural Gas by Turbine Meter AGA catalog XQ0601 2006 3 American Gas Association AGA Report No 8 Compressibility Factors of Natural Gas and Other Related Hydrocarbon Gases AGA catalog XQ9212 1994 4 Wagner W amp Kruse A Properties of Water and Steam The Industrial Standard IAPWS IF 97 for the Thermodynamic Properties and Supplementary Equations for Other Properties Springer Verla
9. 2280 Decane 142 282 111187 304 6 617 7 2100 Helium 4 0026 0 01927 5 195 227 46 Argon 39 948 002201 27155 710 4 150 87 4898 Air 18 0153 0 0179 238 7 551 9 132 61 3805 April 2007 Page A 9 Appendix A Critical press Pc kpa a Meter Factor 3 Although the cone meter s discharge coefficient varies little with Reynolds Number accuracy can be improved when required by calibrating the meter over the range of Reynolds Numbers it will encounter in service The meter factor is defined as true rate indicated rate where true rate is determined by the calibration standard the sonic flow nozzle volumetric or gravimetric prover etc and indicated rate is that given by the cone meter as computed from the discharge coefficient Cd stamped on the meter s data plate A typical calibration curve is shown below 1 05 1 04 1 03 1 02 1 01 14 0 99 0 98 0 97 0 96 4 0 95 0 1000000 2000000 3000000 4000000 5000000 6000000 7000000 MF Once the curve has been determined the meter factor at any Reynolds Number in the range may be found by linear interpolation First compute the mass rate qm determine the fluid s viscosity from Eqn 12 then find the Reynolds Number Re from the formula fluid absolute viscosity N gt units constant see Table 9 3 The Meter Factor method outlined here is consistent with current 2007 AGA and API standard
10. Cone Meter high pressure port located upstream of the low pressure port Section 2 Page 16 April 2007 Section 3 Meter Installation for Liquid Service Installation Options Meter Orientation NuFlo Cone Meters can be installed in a horizontal or vertical position Horizontal is the standard orientation however where space is very limited a vertical position may prove to be the best option Pipe Orientation The orientation of piping is dictated by the position of the meter the type of product being measured and for vertical meter installations the direction of flow When a vertical piping system is used the operator must give special consideration to the piping configuration to prevent gas from being trapped in liquid differential pressure lines Wall Taps In extremely cold environments where there is a risk of product freezing in the process lines the low pressure sensing port connected to the cone meter can become plugged with ice see P2 in Figure 1 2 page 7 In such installations a wall tap may be installed downstream of the meter and used to measure the downstream pressure This will allow the blockage to be removed without removing the meter from the meter run but the meter run must be isolated and depressurized before attempting to clean out the blockage Condensate Chamber Drip Pot The condensate chamber drip pot is a collection vessel to avoid gas bubbles in liquid instrument tubing It should be mounted at t
11. For gases find the compressibility factor Z the molar mass Mr and apply the following relations Gas density at flowing conditions Pup Zo ES EG L K 9 Gas density at base conditions Gas mixture Molar mass molecular weight ES 11 i 1 Use of a Meter Factor curve also requires the fluid s viscosity For a gas mixture use Mn iE Mn i 1 Dip density at flowing conditions Trand P Db density at base conditions u absolute viscosity see tables Pr flowing pressure absolute Ty flowing temperature absolute 28 compressibility factor at flowing conditions 7 and Zb compressibility factor at base conditions T and P P contract base pressure absolute Tp contract base temperature absolute X mole fraction of component i R universal gas constant see Table 6 April 2007 Page A 5 Appendix A Below about 1500 psi the effect of pressure on gas viscosity is negligible however there may be a significant temperature effect see reference 8 Pressure has a negligible effect on the density of most liquids but thermal expansion is often important enough to require correction Similarly the viscosity of liquids can vary substantially with temperature as indicated in Table 7 below Also see reference 8 Table 6 Universal Gas Constant R US units Metric units Metric units Metric units Metric units Pr
12. Ptp Db Table 7 Physical Properties of Selected Liquids Density t Ibm ft3 Density t kg m3 Viscosity p cp Water at 60 F 15 56 C 62 366 999 012 Water at 68 F 20 C 62 316 998 2 Water at 150 F 65 55 C 61 196 980 26 Kerosene Aviation gas Acetone Appendix A Page A 6 April 2007 There are many methods available for determining gas compressibility the standard in the natural gas industry is AGA 8 reference 3 Alternately the widely used Standing Katz diagram Figure A 2 may be used For a simple accurate calculation the Peng Robinson method is recommended Pseudoreduced Pressure Sager 28887 488 2 07 N N 5 lm 2 z E a 0 5 o 8 a x E 5 0 4 ane A r lt Figure A 2 Standing Katz compressibility diagram April 2007 Page A 7 Appendix A Compressibility may be read from the Standing Katz diagram after calculating the reduced temperature and reduced pressure Note that in the following equations all pressures and temperatures are in absolute units psia and Rankin or kpa a and Kelvin Pseudo critical pressure i e cm 13 12551 Pseudo critical temperature m 14 12531 Pseudo reduced pressure Pseudo reduced temperature c oh PT ss 16 where Pc critical pres
13. System The NuFlo Cone Meter alone cannot measure flow It is intended for use with instrumentation such as a transmitter or flow computer The installation usually comprises a manifold system for isolating the process fluid and allowing maintenance and calibration of the transmitter April 2007 Page 9 Section 2 Transmitter E T Manifold Line pressure Temperature Flow Computer n m tubing Figure 2 1 Typical components of a NuFlo Cone Meter system System Components A transmitter valve manifold shut off valves and impulse tubing are typically required for the operation of a NuFlo Cone Meter If the meter is used to measure steam a condensate pot may also be required Before installing a NuFlo Cone Meter review the following installation tips e Make sure the piping tubing or manifold installed between the NuFlo Cone Meter and the transmitter complies with national and local standards regulations and codes of practice to ensure safe containment of fluid e hydrostatic or pneumatic test may be required for piping systems to prove the integrity of the pressure containing components e In installations that are prone to plugging a rod or other device may be used to remove materials blocking the impulse tubing where high temperatures e g steam or dangerous fluids are being measured The meter run should be isolated and completely depressurized WARNI
14. Table 1 Flow Rate Equation Units Constant Gas Measurement US units 5 units US units Metric units Metric units MKS units T s gt N 0 525021 0 0997424 0 0997019 3 51241E 4 3 51241E 5 1 11072 N 3 92743 0 746125 0 745822 0 351241 3 51241E 5 1 11072 Table 3 Expansion Factor Equation Units Constant US units US units US units Metric units Metric units MKS units P Ibf in Ibf in Ibf in bar N3 1 27 707 27 73 1000 1000 1 April 2007 Page A 3 Appendix A Table 4 Flow Rate per Unit of Time Conversion From Multiply by Units per second Units per minute 60 Units per second Units per hour 3600 Units per second Units per day 86400 Y factor and the isentropic exponent The Y factor correction becomes important when the differential 4P is larger than approximately 1 30 of the static pressure 1 uniform pressure units This is most likely to occur at low static pressures for example below 100 psi 700 kpa The isentropic exponent k that appears in the Y factor equation is a characteristic property of the gas being measured Although it is possible to accurately calculate k for many substances the calculation is usually very complex see references 4 and 6 on page A 17 In reality the flow equation is insensitive to variations in k so the normal practice in industry is to treat k as a constant For natural gas 1 3 For steam k 14 D
15. manifold block Figure 3 5 Piping installation for downward flow through a vertical meter with wall taps Section 3 Page 20 April 2007 Transmitter Calibration Transmitters differential pressure and or multi variable should be calibrated according to the manufacturer s recommendations appropriate national or company standards and contractually agreed methodology Consideration should be given to the service in which the NuFlo Cone Meter and transmitter are installed and operated April 2007 Page 21 Section 3 Section 3 Page 22 April 2007 Section 4 Meter Installation for Gas Service Installation Options Meter Orientation NuFlo Cone Meters can be installed in a horizontal or vertical position Horizontal is the standard orientation however where space is very limited a vertical position may prove to be the best option Impulse Tube Orientation The orientation of impulse tubing is dictated by the position of the meter the type of product being measured and for vertical meter installations the direction of flow When a vertically oriented metering system is used the operator must give special consideration to the tubing configuration to prevent liquid from being trapped in gas differential pressure lines in gas service installations Condensate Chamber Drip Pot The condensate chamber is a collection vessel that helps prevent liquid pockets from collecting in
16. will be at a safe operating temperature by the time it reaches the differential pressure transmitter Both lines are extended to the T pieces Note This configuration results in a head difference in the differential pressure lines and the differential pressure transmitter must be zeroed when zero flow has been established in the main line port It may be advisable to flush the low pressure port with an inert fluid When the process is turned off particulates may fall into the low pressure before starting the meter CAUTION April 2007 Page 29 Section 5 Figure 5 3 Piping installation for downward flow through a vertical meter Transmitter Calibration Transmitters differential pressure and or multi variable should be calibrated according to the manufacturer s recommendations appropriate national or company standards and contractually agreed methodology Consideration should be given to the service in which the NuFlo Cone Meter and transmitter are installed and operated Section 5 Page 30 April 2007 Section 6 System Modifications Square Root Error Differential pressure measurement is only accurate for steady state flow Flow pulsation caused by reciprocating compressors defective regulators etc will cause misregistration of delivered volumes Significant errors will occur when using differential pressure devices at the discharge of a reciprocating gas compres
17. 007 Figure 1 2 NuFlo Cone Meter cutaway view 2 H P Tapping Support Tube L P outlet AP l yx ILI BB B GB B B B B B B B B B B B LB B B B B B B BB B B B B B PB B PB B B B B PB B B B B B B B BB B BB PB B B B B SSS N N N N N 772777222722222227341222772 Tubular Body L P Tapping Downstream Cone Hole Differential Producer Cone The shape of the meter cone reshapes the fluid velocity profile upstream of the meter cone conditioning flow naturally and eliminating the need for traditional flow conditioners As a result the NuFlo Cone Meter can be installed in shorter meter runs than those required by conventional differential pressure meters and a high degree of accuracy is ensured even under extremely disturbed flow conditions Table 1 Performance Characteristics and Specifications Accuracy up to 0 5 of rate Turndown 10 1 Repeatability 0 1 Installation Requirements 0 5 pipe diameters upstream 5 diameters if a gate valve is used 0 pipe diameters downstream Differential Pressure Limit gt 0 1 WC minimum 1 in WC preferred but the Reynolds number requirements must be met Differential Pressure Recommended 50 200 WC consult factory for higher DPs Reynolds number Re gt 8000 Re Y factor gases only as installed in various NuFlo computers see Appendix A for
18. 497576 in Temperature corrected beta Eqn 5 0 55014 B D d 4 026595848 3 362497576 D 7 4 026595848 Velocity of Approach factor Eqn 4 l 1 0492 1 1 0 55014 Expansion factor Eqn 6a Table 3 T go ZP 73 1 0 649 0 696 PON 1 0 649 0 696 0 55014 127700 227707 Y 0 9979 Appendix A Page A 14 April 2007 Volume flow rate at base conditions Eqn 3 Tables 1 amp 4 pe NONE p AP B pe p ope 0 0997424 x 0 8217 x 1 0492 x 0 9979 x 0 55014 x 4 026595848 2 23965 x 73 7 0 041601 129 4278 std ft sec 11182563 std ft day 11 18 MMSCFD Sample Calculation 4 Meter Factor Apply the following meter factor table to sample calculation 3 Re MF 976250 1 0055 1326250 1 0069 1844750 1 0046 2290500 1 0006 2912750 0 9968 3229500 0 9972 3656000 0 9980 4058500 0 9966 4955000 0 9972 6452000 0 9967 April 2007 Page A 15 Appendix A Calculate the viscosity cp LLL gt 15551 Numerator Term xi 0 97 0 01078 x 16 042 0 02 0 00788 x 44 096 0 01 0 00724 58 122 0 04348 Denominator Term 0 97 x 16 042 0 02 x 44 096 0 01 x 58 122 4 09414 1 1 _ 0 04348 _ 09414 0 01062 Initial qm from Sample Calculation 3 Eqn 1 EvY BD p AP 0
19. B 4 026 3 362 _ 4 9056 7 4 026 4 026 0 55 1 1 04915 1 1 0 55 Density and flow rate Eqn 2 Tables 2 4 7 water density p p 61 196 Ibm ft3 gy NCA EVY BD AP 2 gs 0 745822 x 0 8217 x 1 04915 x 0 55 x 4 026 x 61 196 x 54 61 196 2 96145 gal sec qv 2 96145 x 60 2177 68 gal min The flow equation can also be simplified by combining the constants and unmeasured variables e g qv AP NOLEvY BD Pa x 60 _ 0 745822 x 0 8217 x 1 04915 0 55 x 4 026 61 196 60 7 61 196 K 24 18017 Appendix A Page A 12 April 2007 Sample Calculation 2 Steam The meter from example 1 is measuring saturated steam at 10 megapascals gauge and produces a differential pressure of 13 kilopascals Local atmospheric pressure is 100 kpa Find the steam flow rate in kilograms per hour Neglect the meter factor and correct for thermal expansion in the meter The absolute pressure is 10 100 1000 10 1 mpa At 10 1 mpa Table 2 of the IF 97 Steam Tables shows the saturation state temperature to be 311 73 C and the vapour phase specific volume to be 0 017813 Density is the inverse of specific volume so 807813 56 1388 kg m D 1 4 T T 102 2604 1 0 0000177 311 73 20 102 7884 d d 1 a 7 T 85 404 1 0 0000177 311 73 20 85 845
20. NG before inserting a rod into an impulse tube Never use rod to clean out process lines high pressure applications Section 2 Page 10 April 2007 Differential Pressure Transmitter A differential pressure transmitter records the differential pressure signal generated by the cone meter and provides an analog or serial output to a flow computer or data control system The transmitter s selected for an installation must be appropriate for operating conditions of the process in terms of both accuracy and safety DP devices must be zeroed following installation The procedure varies somewhat for liquid gas and steam applications Procedures are provided for each application in Sections 3 4 and 5 respectively Shut Off Valves Choose a block valve that is rated for the operating pressure of the pipe in which it will be installed Where dangerous or corrosive fluids or gases like oxygen are likely the block valve and packing must provide ample protection The valves must not affect the transmission of the differential pressure signal Install block valves next to the NuFlo Cone Meter pressure taps Never use a globe valve for differential pressure transmission lines Ho 6 O Figure 2 2 Block valves Valve Manifolds A 3 way or 5 way valve manifold isolates the transmitter from the process lines 5 valve manifolds recommended They allow the operator to calibrate the transmitter without removing it from th
21. al pressure transmitter In most cases a large diameter tee is all that is required to collect the liquid see Figure 5 1 However if the DP measuring instrument is designed with hydraulic pneumatic bellows such a Barton 202E chart recorder a larger volume condensate chamber will be required see Figure 5 2 Modern DP transmitters have very little diaphragm movement and do not require the large volume condensate chamber April 2007 Page 27 Section 5 Horizontal Meter Installation The pressure taps shall be above the horizontal centerline 9 o clock to 3 o clock of the primary device In condensing hot vapor service such as steam the fluid in the impulse lines is liquid condensed from the vapor The use of a condensate chamber is mandatory to prevent hot process fluid from damaging the transmitter The impulse tubing should slope upwards from the cone meter to the condensate pots A condensate pot can be a tubing tee for low volume DP instruments as shown in Figure 5 1 or a full size condensate chamber for high volume DP instruments as shown in Figure 5 2 In either case the condensate pots should be at exactly the same level to ensure accurate differential pressure readings The line from the bottom of the tee to the transmitter mounted below the tee should be filled to the point where excess fluid can drain back into the meter In many cases water condensed steam is used for this fluid fill However in cold weather the fluid
22. e impulse tubing drain the transmitter and impulse tubing or vent it to atmosphere Valve manifolds must be oriented according to the manufacturer s instructions to prevent trapping of air or liquid April 2007 Page 11 Section 2 Figure 2 3 A 5 way manifold block mounted with a multi variable transmitter Thermowell or Thermocouple Flow measurement calculations for differential pressure devices require temperature and pressure measurement Generally a thermowell with an RTD installed is mounted downstream of the meter within 3 pipe diameters of the meter Alternatively a thermo well can be installed inside the meter body upstream of the cone and the meter calibrated with it in position For installations where temperatures are stable a thermocouple or temperature probe may be attached to the outside of the upstream piping and covered with insulation Impulse Tubing Considerations Before connecting impulse tubing between the NuFlo Cone Meter and the transmitter consider the following tips for optimizing your system s measurement accuracy In a well designed installation fluids will drain freely from the process lines and gases will vent to the atmosphere Tubing Size Selection Impulse tubing that connects the DP Cone meter tap holes to the transmitter diameters vary with service conditions The bore should be no smaller than 1 4 in 6 mm a minimum diameter of 3 8 in 10 mm is recommended The internal diameter ID mu
23. eed methodology Consideration should be given to the service in which the NuFlo Cone Meter and transmitter are installed and operated Section 4 Page 26 April 2007 Section 2 Meter Installation for Steam Service Installation Options Steam measurement is the most difficult application for differential pressure transmitter tubing and requires careful consideration during installation Steam is usually at a high temperature which will damage the transmitter and in addition it can be in the liquid or gaseous phase depending on temperature and pressure Due to this the differential pressure impulse tubing must be orientated in such a manner that it can operate with a gas or liquid present Meter Orientation NuFlo Cone Meters can be installed in a horizontal or vertical position Horizontal is the standard orientation however where space is very limited a vertical position may prove to be the best option Impulse Tubing Orientation The orientation of the impulse tubing is dictated by the orientation of the meter the type quality of the steam being measured and for vertical meter installations the direction of flow When a vertical meter run is used the operator must give special consideration to the impulse tubing configuration to prevent liquid from being trapped in gas differential pressure lines Condensate Chamber The condensate chamber is a liquid reservoir that helps prevent super heated steam from entering the differenti
24. elevation will cause a difference in the hydrostatic pressure of the liquid column in the process lines Temperature differences will cause a difference in the density of the fluids in the two lines which will change the amount of pressure generated Both can result in inaccurate differential pressure measurements Fasten the process lines together if possible e Install process lines so that they slope in only one direction up or down If piping must slope in more than one direction do not allow more than one bend and install a liquid or gas trap as applicable A liquid trap should be installed at the lowest point in a gas service installation A gas trap should be installed at the highest point in a liquid service installation Extreme Temperature Applications Steam temperatures can reach 1500 F 815 C well exceeding the temperature rating of a standard DP transmitter 200 F or 93 C A condensate chamber can be used to isolate the transmitter from the extreme temperatures Alternatively a long tube section can be installed to allow the fluid to cool before it reaches the transmitter As a general guideline when planning tubing lengths for temperature control run tubing horizontally where possible and allow for a temperature drop of 100 F 38 C per foot 305 mm of tubing This is merely a guideline however the operator is still responsible for ensuring that the temperature at the transmitter does not exceed the transmitter s ra
25. fferential pressure taps should be located in the top half of the pipeline For wet gas taps should be located between the 10 o clock and 2 o clock positions to allow proper drainage of liquids present e For steam differential pressure taps should be located in the side of the pipeline Illustrations of typical piping configurations for liquid gas and steam are provided in Sections 3 4 and 5 respectively Section 2 Page 14 April 2007 as CO CO LIQUID WET GAS DRY GAS STEAM 4 O CLOCK TO 5 O CLOCK 10 O CLOCK TO 2 O CLOCK 9 O CLOCK TO 3 O CLOCK HORIZONTAL TAPS ONLY OR 9 O CLOCK 7 O CLOCK TO 8 O CLOCK OR 3 O CLOCK Figure 2 4 Recommended tap locations for horizontal meter installations For vertical installations the location of differential pressure taps is unrestricted as long as the static pressure tap is upstream of the lower pressure tap Impulse Tubing Impulse tubing is used to connect the sensing taps of the cone meter to the manifold connected to the differential pressure transmitter One section of tubing should connect the high pressure tap to the high pressure static side of the differential pressure transmitter another section of tubing should connect the low pressure tap to the low pressure side of the differential pressure transmitter e Impulse tubing should be installed with a gradient larger than 1 10 to help prevent undesirable fluids from being transferred to the differential pressure transmitte
26. g 1998 ISBN 3 540 64339 7 5 Gas Processors Association GPA 2145 03 Table of Physical Constants for Hydrocarbons and Other Compounds of Interest to the Natural Gas Industry GPA Tulsa OK 2005 6 American Gas Association AGA Report No 10 Speed of Sound in Natural Gas and Other Related Hydrocarbon Gases AGA catalog XQ0310 2006 7 American Society of Mechanical Engineers ASME PTC 19 5 2004 Flow Measurement Performance Test Codes ASME New York NY 2005 8 Miller R W Flow Measurement Engineering Handbook third edition McGraw Hill New York NY 1996 ISBN 0 07 042366 0 April 2007 Page A 17 Appendix A WARRANTY LIMITATION OF LIABILITY Seller warrants only title to the products software supplies and materials and that except as to software the same are free from defects in workmanship and materials for a period of one 1 year from the date of delivery Seller does not warranty that software is free from error or that software will run in an uninterrupted fashion Seller provides all software as is THERE ARE NO WARRANTIES EXPRESS OR IMPLIED OF MERCHANTABILITY FITNESS OR OTHERWISE WHICH EXTEND BEYOND THOSE STATED IN THE IMMEDIATELY PRECEDING SENTENCE Seller s liability and Buyer s exclusive remedy in any case of action whether in contract tort breach of warranty or otherwise arising out of the sale or use of any products software supplies or materials is expressly limited to the replacement of
27. gas instrument tubing Horizontal Meter Installation The pressure taps on the NuFlo DP Cone Meter should be between the horizontal centerline and the top of the pipe 3 o clock to 12 o clock or 9 o clock to 12 o clock If the fluid is a wet gas 1 6 8 gas containing small quantities of liquids the pressure taps should be situated in a vertical position 12 o clock to allow all liquids to drain away from the transmitter Figure 4 2 If the connecting tubing extending from the cone meter to the transmitter is not installed in a vertical position it should slope upward at least 1 inch per foot to ensure proper drainage Figure 4 1 Piping installation for dry gas measurement with a horizontal meter April 2007 Page 23 Section 4 Figure 4 2 Piping installation for wet gas measurement with a horizontal meter Drip Pot Installation Optional for Wet Gas If drip pots are used they should ideally be mounted immediately following the shutoff valves installed near the upstream and downstream pressure taps of the meter For wet gas applications the piping from the meter connects to the condensate chamber in a 3 o clock or 9 o clock position on a horizontal plane The chambers are positioned vertically so that the meter connection and instrument connection points are at the top and drain points are at the bottom of the chambers Dp e Figure 4 3 Condensation chamber drip pot installatio
28. he highest point in the impulse tubing between the cone meter and the DP transmitter Horizontal Meter Installation For horizontal installations pressure taps must be positioned 30 to 60 below the horizontal centerline 4 o clock to 5 o clock or 7 o clock to 8 o clock Taps at the bottom of the pipe may become plugged with solids from the liquid taps above the centerline can accumulate air or non condensing gases In liquid service the connecting lines from the meter shall slope downward to the transmitter with no upturns or pockets The minimum recommended slope for self venting is 1 inch per foot April 2007 Page 17 Section 3 Figure 3 1 Piping installation for liquid measurement with a horizontal meter Bubble Pot Installation Optional In liquid applications where the transmitter must be mounted above the metering line gas or vapor in the liquid can collect at the highest point in the instrument tubing and give a false differential pressure reading Bubble pots may be the only effective solution for such installations The piping from the meter connects to the bubble pot anywhere between the 10 o clock and 2 o clock positions on a horizontal plane Figure 3 2 Bubble pot installation for liquid service where transmitter must be installed above the meter run Section 3 Page 18 April 2007 Vertical Meter Installation In most process applications the operator should assume that some level of gas or vap
29. iameter at flowing conditions When the flowing temperature Tr differs significantly from the calibration temperature T the meter tube and cone diameters should be corrected as follows Te Dream ict otio mtu tn MPG Seta as CE an CCS 7 ue a seem 155512 oderam ette eed RR 8 D meter tube inside diameter 2 at reference temperature T d cone diameter 2 at reference temperature T a linear coefficient of thermal expansion cone 2 linear coefficient of thermal expansion meter tube flowing temperature T is indicated on the meter s calibration sheet normally close to 20 C 68 F Note that the beta ratio f shown on the calibration sheet is at 7 not at T When a diameter correction is applied should be recalculated from the corrected diameters Shown on the meter s data plate and calibration certificate Appendix A Page A 4 April 2007 Table 5 Linear Coefficient of Thermal Expansion see reference 7 US units in in F Metric units m m C Stainless steel below 150 C 300 F 0 00000925 0 0000167 Stainless steel above 150 C 300 F 0 00000984 0 0000177 Carbon steel 150 C 300 F 0 00000620 0 00001116 Carbon steel above 150 C 300 F 0 00000725 0 00001305 Fluid properties The flow equations require knowledge of the fluid s density Density can be measured estimated or calculated from a suitable equation of state
30. must be protected from freezing The fluid fill requires careful design with heat tracing and insulation to keep it in the liquid phase and to keep both the high pressure and low pressure legs of the tubing at the same temperature maintaining the liquid fill at the same density A liquid leg fill fluid other than water should be used if practical Methanol is a possible substitute but di butyl phthalate is the recommended fill fluid because it is immiscible with water and remains liquid throughout a broad temperature range 31 F to 644 F 35 C to 340 C Important Care should be taken when using di butyl phthalate follow all hazardous material guidelines CAS No 87 74 2 Figure 5 1 Piping installation for steam measurement with a horizontal meter and a low volume DP instrument straight on into transmitter Section 5 Page 28 April 2007 Figure 5 2 Piping installation for steam measurement with a horizontal meter and a high volume DP instrument such as a chart recorder with DPU Vertical Meter Installation For steam service installations in which the meter is oriented vertically piping from the upstream pressure tap is extended horizontally to connector The T connector enables a plug to be installed at the top for liquid filling purposes to avoid overheating of the differential pressure cell The manifold block is positioned directly below at a distance that ensures the steam
31. n Section 4 Page 24 April 2007 Vertical Meter Installation When the meter is installed in a vertical position the operator must take special care to ensure that no trap forms in the downstream tap such that gas is trapped in a liquid or liquid is trapped in a gas When measuring dry non condensing gases where there is absolutely no risk for liquid being present the piping from the downstream pressure tap of the cone meter can be extended horizontally and then angled upward to connect to the manifold block The manifold block must be mounted horizontally and the tubing from the upstream tap of the cone meter must slope at least 1 inch per foot to the same level as the downstream tap piping to connect to the manifold shown in Figure 4 4 The U configuration could trap liquid in the cone If there is any liquid present in the gas do not use the piping arrangement changing the downstream pressure CAUTION FLOW FLOW Figure 4 4 Piping installation for upward flow dry gas through a vertical meter April 2007 Page 25 Section 4 Figure 4 5 Piping installation for downward flow dry gas through a vertical meter Transmitter Calibration Transmitters differential pressure and or multi variable should be calibrated according to the manufacturer s recommendations appropriate national or company standards and contractually agr
32. of liquid in the other leg the density of the fluid will be different resulting in inaccurate differential pressure measurement This most often occurs when one leg of the tubing is in bright sun and the other leg is shaded To minimize the effects of temperature differences in the vertical legs of impulse lines shade both of the legs from the sun The effect of temperature differences is more notable in liquid service installations gas service is not as prone to DP error due to varying line temperatures April 2007 Page 31 Section 6 Section 6 Page 32 April 2007 Appendix A Flow Measurement Theory and Equations Important The NuFlo Cone Meter flow equation differs from the orifice equation The device performing the flow calculation flow computer PLC chart integrator etc must be programmed to use the equations described in this section Bernoulli Principle The calculation of flow based on the differential pressure of fluid passing through a cone meter uses equations that are very similar to those used to calculate flow with all leading differential pressure devices The principle behind the cone meter is the conservation of energy in an enclosed pipe and is described by the Bernoulli equation When fluid passes through a closed pipe and encounters a restriction the pressure at the restriction decreases This results in a differential pressure when compared to the pressure upstream of the restriction as shown in Fig
33. or exists in a liquid service even if the liquid is water As a result the piping configuration must be designed to allow gas to rise back into the flow stream The process piping should be extended horizontally a very short distance from the downstream tap and then sloped at a nominal 1 inch per foot angle to the top of the manifold block The manifold block should be mounted horizontally below the upstream tap so that piping from the upstream tap to the manifold slopes downward also port It is advisable to flush the low pressure port with an inert fluid before When the process is turned off particulates may fall into the low pressure starting the meter CAUTION Figure 3 3 Piping installation for upward flow through a vertical meter Note While downward flow through a vertically oriented meter is suitable for a gas application downward flow piping configurations that use the standard upstream and downstream pressure ports are not recommended for liquid applications due to the risk of trapping gas For such applications consider the use of a vertically oriented meter with wall taps as described below April 2007 Page 19 Section 3 Vertical Meter with Wall Taps Both process lines should be extended horizontally for a very short distance and then tubed downwards to a manifold block The manifold block should be mounted horizontally below the bottom tap and the transmitter should be mounted below the
34. r e If tubing is installed in a horizontal orientation install a gas liquid separator device e Avoid abrupt bends in impulse tubing If impulse tubing sections are long use mounting brackets to support them See also Tubing Size Selection page 12 differential pressure transmitter Never use excessive pressure or force when connecting impulse tubing to a WARNING tubing is rated for the anticipated temperature range If high temperature fluids are likely to be encountered make sure the impulse CAUTION See Sections 3 4 and 5 for installation procedures recommended for liquid gas and steam applications respectively Both horizontal and vertical meter orientations are discussed as appropriate for each application April 2007 Page 15 Section 2 For additional installation information refer to ISO 5167 or contact Cameron s Measurement Systems Division Installation Checkpoints for the Transmitter Before putting the NuFlo Cone Meter into service verify that the transmitter is installed properly by reviewing the following checkpoints e 15 the transmitter full scale correct e Has the transmitter zero been checked and or adjusted e Are the transmitter and flow computer set to the appropriate modes linear or square root e Have the transmission lines to the transmitter been purged e Are there any leaks in the transmission lines e Is the manifold cross valve closed e Is the NuFlo
35. s See references 1 amp 2 Appendix A Page A 10 April 2007 Table 9 Reynolds Number Equation Units Constant N2 US units US units US units Metric units Metric units MKS units From the calibration curve locate the two Reynolds Numbers that bracket Re such that Re lt Re lt Re 2 0 0 Re Re Ren 1 and interpolate the meter factor from _ Ras 0 MF ME 18 The adjusted flow rate is a gh X ME dentato tet oet tut eant d stood edat taf Ebene 19 Other methods of handling meter factors are described in Appendix D 3 of AGA Report No 7 reference 2 Note that in their respective flow equations the cone meter s discharge coefficient Cd plays the same role as the turbine meter s K factor so the methods described in the report can be easily adapted to the cone meter April 2007 Page A 11 Appendix A Sample Calculation 1 Liquid A stainless steel cone meter having an inside diameter of 4 026 inches 102 2604 mm and a cone diameter of 3 362 inches 85 404 mm measuring pure water at 150 F generates a differential pressure of 54 in H2O g The discharge coefficient from the meter s calibration certificate 15 0 8217 Find the gross volume flow rate in US gallons per minute neglect the meter factor and thermal expansion in the meter Beta and EV Eqn 4 and 5
36. sor where pressure pulses may exceed 10 of static pressure This causes a condition called square root error which may be reduced by the use of an acoustic filter A filter design is described by E Carreon El Paso Natural Gas in Effects and Control of Pulsations in Gas Measurement Proceedings of the Seventieth International School of Hydrocarbon Measurement 1995 Gauge Line Error Gaseous fluids in small bore pipes may start to oscillate due to an effect predicted by Helmholtz This acoustic resonance comprising of standing pressure waves usually occurs at a maximum of 4 wavelengths This phenomenon termed gauge line error can be due to the use of long impulse lines To help prevent gauge line error keep impulse lines as short as possible use large impulse line diameters where possible and keep impulse line diameters constant Small diameters are more likely to result in measurement problems The direct mounting of the transmitter to the meter can help reduce the effects of gauge line error Direct mount manifolds are available from leading manifold manufacturers Elevation and Temperature Effects in Piping In liquid service it is important to keep vertical elevation of impulse lines equal If one liquid filled leg is longer than the other the hydrostatic head of the lines will vary resulting in inaccurate differential pressure measurement Similarly if the temperature of liquid in one leg is different from the temperature
37. st not exceed 1 in 25 mm For steam applications the ID should be 3 8 in 10 mm to 1 in 25 mm In most process control applications the primary concern is flow reliability If the pressure taps or the impulse tubes become plugged the reliability of the flow measurement is lost This creates a safety risk and the cost incurred in regaining control can be substantial High reliability is required for flow signals used in process safety management A minimum tubing ID of 5 8 in 16 mm is recommended in industrial applications For high temperatures in condensing vapor service in 25 mm is recommended Tubing Material Most instrument tubing is 316 stainless steel However duplex steel may be preferred for offshore applications where corrosion protection against saltwater is needed Section 2 Page 12 April 2007 Tubing Length and Configuration For best performance adhere to the following recommendations for tubing length and orientation e Tubing length must be short enough to ensure a high degree of accuracy and long enough to ensure proper cooling of high temperature fluids before they reach the transmitter e Make sure the installation permits access to the impulse tubes valves valve manifolds and transmitters e Limit the number of fittings and avoid long tubing sections which can impair measurement accuracy and increase the risk of plugging e Avoid changes in tubing elevation and fluid temperature Differences in
38. such products software supplies or materials on their return to Seller or at Seller s option to the allowance to the customer of credit for the cost of such items In no event shall Seller be liable for special incidental indirect punitive or consequential damages Seller does not warrant in any way products software supplies and materials not manufactured by Seller and such will be sold only with the warranties that are given by the manufacturer thereof Seller will pass only through to its purchaser of such items the warranty granted to it by the manufacturer MEASUREMENT SYSTEMS Formerly NuFlo Measurement Systems Barton Instrument Systems Caldon Inc NORTH ASIA EUROPE MIDDLE EAST AMERICA PACIFIC amp AFRICA 1 800 654 3760 603 2287 1039 44 1243 826741 ms us c a m com ms asiapacific c a m com ms uk c a m com HOUSTON HEAD OFFICE 281 582 9500 www c a m com flo USA Houston TX Corpus Christi TX Kilgore TX Odessa TX Dallas TX Tulsa OK Duncan OK Denver CO Bakersfield CA Shreveport LA Lafayette LA Houma LA e Pittsburgh Laurel MS Dunbar WV Casper WY Charleston WV CANADA Calgary AB Edmonton INTERNATIONAL Aberdeen Scotland Beijing China Bognor Regis UK Dubai UAE Hassi Messaoud Algeria e Kuala Lumpur Malaysia Singapore C CAMERON
39. sure see Table 8 Tc critical temperature see Table 8 mole fraction of component 1 Locate the curve of the pseudo reduced temperature note where it crosses the vertical pseudo reduced pressure line and read the compressibility factor on the left or right Appendix A Page A 8 April 2007 Table 8 Physical Properties of Selected Gases Gas Methane Nitrogen Carbon dioxide Ethane Propane Water vapour 18 0153 0 009607 116477 77 Critical Tc Critical temp Tc K Molar Viscosity p mass Mr c Critical press Pc psia 16 042 0 01078 343 001 67 190 56 4599 28013 001735 22714 492 5 126 19 3396 44 010 0 01439 547 47 Hoo 7377 1070 304 1 30 069 0 00901 549 594 706 6 305 33 4872 44 096 0 00788 665 59 615 5 369 77 4244 32001 1 647 1 1311 3 Hydrogen 4 082 00124 672 47 1306 5 373 6 9008 sulphide Hydrogen 20159 000871 59 36 187 5 32 97 1293 Carbon 28 010 0 01725 23926 507 5 132 7 3498 monoxide Oxygen 31 999 0 02006 27824 24 744 4 15458 58 5043 Isobutane 58 122 0 00724 ris LN 3640 N butane 58 122 0 00682 765216 550 9 425 12 3798 Isopentane 72149 82865 490 4 460 36 3381 N pentane 72449 84542 488 6 469 68 3370 Hexane 86 175 9135 436 9 507 5 3012 Heptane 100 202 972 54 396 8 540 3 2736 Octane 114 229 1023 89 360 7 568 8 2487 128 255 1070 47 1330 7 594 7
40. the appropriate expansion factor equations with respect to the meter geometry and process application Fluids gases vapors or liquids Meter Orientation horizontal or vertical Tap Location varies with type of product measured see Figure 2 4 page 15 Coefficient of discharge Cd Cd is unique to each meter and must be determined by calibration April 2007 Page 7 Section 1 Beta Range 0 45 to 0 85 standard 0 05 increments End Connections weld neck flanges RTJ flanges slip on connections Threaded fractional inch sizes flangeless welded in line Tube Design welded construction 1 2 in and greater diameters carbon stainless or duplex stainless steel The Reynolds number typically ranges from 8500 to above 5 million With special calibration the Cd can be calibrated to a lower Reynolds number Differential pressures can range from less than 1 in WC to more than several hundred inches WC to facilitate large turndowns A minimum differential pressure of 1 in or greater is recommended to ensure a stable and low noise differential pressure signal due to transmitter hysteresis Meter Nameplate The nameplate affixed to the NuFlo Cone Meter Figure 1 3 contains specifications for the meter including the coefficient of discharge Cd The calibrated Cd which is unique to each meter offers traceability for the accuracy of the meter
41. ti variable transmitter are among the devices that are compatible with the Cone Meter The method used to connect the transmitter to the meter varies depending on the type of product measured and available space for mounting the meter This user manual provides installation instructions and piping diagrams for using the Cone Meter in liquid gas and steam applications Applications The NuFlo Cone Meter is designed to work in unprocessed and processed applications and is ideal for upstream midstream and downstream flow metering applications that present a wide range of measurement challenges The NuFlo Cone Meter is ideal for low pressure coalbed methane wellhead and field applications compressor anti surge control and test separator applications Meter Components The meter comprises three primary elements as shown in Figures 1 1 and 1 2 e ameter body or tube with or without flanges acone assembly either fabricated or machined from a solid piece of metal positioned in the center of the meter tube of pressure taps a wall tap upstream and an integral sensing tap downstream for reading the differential pressure in the center of the meter tube Alternately a downstream tap may be used under certain process measurement conditions The meter can be manufactured from various materials carbon stainless or duplex stainless steel to meet the specific requirements for metering steam air natural gas digester gas ni
42. ting for the environmental conditions present In extreme cold temperature installations thermal insulation and or heat tracing of process lines may be necessary The amount of heat used must be carefully calculated to prevent liquids from vaporizing and prevent condensable vapors from producing unwanted condensation Fastening process lines together is recommended for keeping process lines at approximately the same temperature Providing a temperature controlled environment for the transmitter also helps ensure accurate metering in locations where extreme temperatures are likely such as on offshore platforms or in desert installations April 2007 Page 13 Section 2 Best Practices for Installing the NuFlo Cone Meter Note Read the best practice recommendations below in their entirety before installation of the NuFlo Cone Meter The basic steps for installing a NuFlo DP Cone Meter system are described as follows 1 Install the meter in the meter run in accordance with the flow run requirements below 2 Secure the manifold to the meter taps 3 Connect the differential pressure transmitter to the manifold observing the recommended guidelines below for pressure measuring tubes 4 Connect the transmitter to the flow computer according to instructions in the transmitter user manual 5 Zero the transmitter Flow Run Requirements The NuFlo Cone Meter should be installed with zero to five pipe diameters of straight run ups
43. tream of the meter and zero to three pipe diameters downstream The meter can be used in pipelines that are slightly larger than the meter tube however if the meter tube is larger than the pipeline operators should contact NuFlo for installation requirements This is usually determined before supply according to application and the degree of accuracy and performance required Meter Orientation and Transmitter Position The NuFlo Cone Meter can be installed in a horizontal or vertical position The location of the transmitter with respect to the meter should be based on the properties of the fluid or gas being measured gas steam liquid etc and the direction of flow through the pipeline The direction of flow is clearly labeled on nameplate affixed to the body of every NuFlo Cone Meter shipped The meter must be installed so that the static pressure tap labeled P1 in Figure 1 2 is always upstream of the differential pressure tap Pressure Tap Location Location of the static pressure and differential pressure taps will vary with the product flowing through the pipeline liquid gas or steam and the orientation of the meter vertical or horizontal For horizontal installations the following installation guidelines apply e For measuring liquid differential pressure taps should be located in the bottom half of the pipeline between 4 o clock and 5 o clock positions or between 7 o clock and 8 o clock positions e For measuring gas di
44. trogen ethanol and a host of liquids from crude oil to waste water April 2007 Page 5 Section 1 Upstream and Cone assembly downstream taps Meter body Figure 1 1 Basic components of the NuFlo Cone Meter The NuFlo Cone Meter has no moving parts and is designed such that there are no areas of stagnation where trash or fluid particles can lodge Accordingly it is virtually maintenance free Principles of Operation The NuFlo Cone Meter generates a differential pressure that can be used to calculate fluid flow rate A transmitter measures the differential pressure and outputs an integrated electronic signal typically via Modbus or a 4 20 mA output to a flow computer or other process controller for interpretation and readout For compressible fluids line pressure and temperature measurements are required for accurate flow rate calculations as well as compensation for the adiabatic change in the expansion factor As fluid flowing through the pipe flows around the cone a pressure drop occurs The static line pressure P1 is measured via a wall tap located just upstream of the cone Figure 1 2 Pressure is also measured via a sensing tap that is connected to the cone and measures pressure at a point immediately downstream of the cone P2 The fluid flow rate is calculated using the difference between the two pressures using variations of the standard differential pressure flow measurement principles Section 1 Page 6 April 2
45. ure A 1 The mass flow of the fluid traveling past the restriction is proportional to the square root of the differential pressure Ai gt 01 2 Figure A 1 Creation of differential pressure April 2007 Page A 1 Appendix A The general mass flow equation for the DP cone meter is shown below in a format similar to the well known orifice equation The calculation of the beta ratio is adjusted to reflect the annular area of the cone restriction rather than the central area of an orifice meter Mass rate qm BD Jp MP 1 Volumetric rate at flowing conditions gross or actual flow rate _ qm Cd EvY Pip AP 2 Volumetric rate at base conditions standard flow rate Ti Cd EvY B Dy AP 7 NE 3 Where RN Mb HERR ERUNT 4 For compressible fluids gases vapours Y 1 0649 0 606 8 2 REOR 6a For incompressible fluids water other liquids units constant see Tables 1 and 2 Cd discharge coefficient 1 D meter tube inside diameter at flowing conditions d cone diameter at flowing conditions AP differential pressure P absolute static pressure at the upstream tap k gas isentropic exponent pip fluid density at flowing conditions fluid density at base conditions 1 Shown on the meter s data plate and calibration certificate Appendix A Page A 2 April 2007
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