User`s Manual Laminar Flow Elements
Contents
1. calculations Standard or Mass Flow Rate CHECK VALVE LO HI DIFFERENTIAL PRESSURE INDICATOR TEMP RH HI 0 INLET ABSOLUTE I PRESSURE INDICATOR M FLOW FLOW M LAMINAR ELEMENT Actual Volumetric Flow Rate CHECK VALVE p ZX 10 d 22 7 p We 27 22 DIFFERENTIAL PRESSURE INDICATOR TENP RH 0 n FLOW FLOW LAMINAR ELEMENT Laminar Flow Systems OU lo o9 TEMP RH FLOW N OUT O U 1900 FLOW COMPUTER SMART 5 320 500 TEMP RH TEMP RH a TE 4 FLOW FLOW FLOW FLOW N FLOW FLOW gt gt LAMINAR ELEMENT LAMINAR ELEMENT Figurel Typical Installations of Laminar Flow Elements Actual Standard or Mass Flow Calibration Curve Table Meriam performs an air calibration of the LFE using a master flowmeter that is traceable to the National Standards and Technology2. Pstd Tf Mass flow rate Standard volumetric flow rate x density 2 standard conditions Temperature F 50 60 70 80 90 100 110 120 130 140 150 1 gt 5 2 10 Humidity 2096 Humidity 0 99 30 Humidity x 2 N 4096 Humidity 5 o _ __ p d _ pn 928 50 Humidity 5 D 6096 Humidity EZ 097 7096 Humidity 8 80 Humidity 90 Humidity 0 96 Figure2 Relative humidity correction factor for air viscosity A 35500 Kestin amp Whitelaw Table A 35600 NBSIR 83 2652 Humidity Correction Factor for Air Pwet Pdry Relative Humidity rs ee 9974 9948 9922 9895 9870 9964 9928 9892 9855 9818 9951 9902 9854 9805 9756 9981 9962 9944 9925 9907 Determining Flow from your Laminar Flow Element Calibration Curve Table The curve table of each LFE is normalized to standard conditions listed by multiplying the calibration data points by the ratio of viscosity of gas at calibration temperature viscosity of gas at 70 F standard temperature Therefore you should NOT read the flow rate directly from the curve table unless your flow temperature and pressure are identical to the standard conditions The following steps must be taken to determine flow rate at flowing conditions other than standard 1 Measure and correct to 4 C a
3. NIST The calibration data is standardized to an equivalent dry gas flow rate at 70 F 21 190 and 29 92 inches Hg absolute 101 3 kPa abs The customer may request another standard condition such as O C It is then possible to determine the actual or standard volumetric flow rate at your flowing conditions Each LFE has at least one calibration curve or table The standard curve table is for dry air flow rate in units of cubic feet per minute CFM versus the differential pressure DP in inches of water referenced to 4 produced by the LFE You may request a curve table for a different gas and or for different flow rate units Each curve table is generated using a quadratic second order equation B x DP x DP Flow The calibration constants B and C are printed on each curve table Actual Volumetric Flow Rate The LFE determines the actual volumetric flow rate To obtain the actual volumetric flow rate the differential pressure across the LFE and the inlet temperature to the LFE is measured Using the calibration curve table associated with the particular LFE a flow rate value is obtained by either 1 reading the value from the curve table or 2 using the formula B x DP x DP Flow Each curve has unique constants B and C Multiply this flow rate value by the ratio viscosity of flowing gas at 70 F in micropoise viscosity of flowing gas at flowing temperature in micropoise y 55 5 or ustd uf The product i
4. B x DP C x DP gt is equation can be rewritten B x x x uf x r Table A 31031 lists the values of Pf Pstd absolute line pressures from 26 Hg at 0 05 Hg intervals The standard pressure is 29 92 Hg absolute for this table Table A 32422 lists the values of Tstd Tf x ustd uf for air from 50 to 159 F in 1 intervals The standard temperature is 70 F 529 67 R for this table Note If you are flowing wet air a humidity correction factor for standard volumetric flow rate must be used The difference between wet air density Pwet and dry air density Pdry increases with temperature and humidity At 80 F and 80 relative humidity the ratio of Pwet Pdry is 990 Table 35600 lists the ratio Pwet Pdry of air from 40 to 100 F and from 20 to 100 relative humidity The equation for standard volumetric flow rate of flowing wet air becomes Standard Volumetric Flow Rate wet Air Bx DP C x Dp x 55 T9 PE x Pwet uwet air Tf Pstd Pdry Mass Flow Rate Multiply the standard volumetric flow rate by the density of the flowing gas at standard conditions to obtain the mass flow rate of that gas Mass Flow rate Standard volumetric flow rate x density 2 standard conditions Summary Curve table value DP B x DP C x DP td Actual volumetric flow rate B x DP Cx DP x gt 5 Pf Tstd Standard volumetric flow rate Actual volumetric flow rate x
5. covers models 50 10 50MW20 50MR2 50MJ10 SOMC2 and 50 15 For descriptions dimensions and capacities of these elements refer to Meriam Bulletin File No 501 215 Special Precautions When Handling Matrix Elements The Meriam LFE depends on the precise fabrication of a matrix metering element for its basic accuracy These elements are manufactured from 001 inch stainless steel stock and are carefully fabricated Exercise extreme care when handling the exposed element to make sure the end faces are not gouged or damaged in any fashion Gouges or damage to the end surfaces may produce nonlinear resistance to flow and introduce error If the end surface becomes damaged the accuracy of the element may be restored by recalibration at the factory Inspection 1 Make sure you have unpacked all instructions and other data that accompanied the unit 2 Visually inspect for any signs of damage There must be no nicks or scratches surfaces of the LFE should be clear 3 Unitsare shipped with a cap plug in each opening which protects the ends and pressure taps Remove these cap plugs 4 Visually inspect matrix surface and inside housing No capillaries should be blocked unless specified in special applications Installation Make sure the line is free of dirt and other foreign materials The metered gas must be clean In line use of filters 15 recommended Connections to the differential pressure instrument should be made with equal lengths o
6. 10 12 1 14 1 4 4 8 3 4 7 1 2 12 12 1 7 6 8 7 8 9 1 2 16 16 1 8 21 1 4 3 1 8 2 7 16 l 1 4 i SIZE MODEL Sowwa0 SIZE ana SS HALF COUPLINGS 3 5 8 11 2 2 1 4 2 2 3 4 yo BOTH ENDS TYPE 9 HAS 3 4 MODEL 50MJ10 TYPE SS BODY 3 3 8 i DIA HOLES ON FOR 1 4 1 0 HOSE BOLT CIRCLE 2 3 8 B G MODEL 50MR2 SIZE ALUMINUM BODY ALUMINUM HOSE CONNECTIONS ALUMINUM FLANGES pie E 3 1 87 11 167 1 4 BOTH 4 1 277 MODEL 50MK10 TYPE SS BODY 3 3 8 pee FOR 1 4 10 HOSE i D i size o F s 50MR2 2 2 6 1 16 5 4 15 172 4 4 4 3 4 MODEL 50MC2 SIZE 2 4 4 10 13 16 8 172 25 8 3 4 7 1 2 ALUMINUM BODY ALUMINUM HOSE CONNECTIONS 50MR2 6 6 13 9 16 12 30 1 2 8 7 8 9 1 2 SOMR2 8 8 16 15 16 16 3 4 37 1 418 7 8 11 3 4 MODEL 52 D E F 50MC2 2 2 5 9 16 5 1 4 14 1 2 5oMCc2 4 4 5 16 8 1 2 24 50 2 6 6 13 5 16 12 30 50MC2 8 8 16 5 16 16 3 4 3
7. 23 34 25 1 1447 26 15 8739 34 30 1 1458 26 20 8756 34 35 1 1480 26 25 8773 34 40 1 1497 26 30 8790 34 45 1 1514 26 35 8806 34 50 1 1530 26 40 8823 34 55 1 1547 26 45 8840 34 60 1 1564 26 50 8856 34 65 1 1580 26 55 8873 34 70 1 1597 26 60 8890 34 75 1 1614 26 65 8907 34 80 1 1631 26 70 8923 34 85 1 1647 26 75 8940 34 90 1 1664 26 80 8957 34 95 1 1681 26 85 8973 35 00 1 1697 26 90 8990 35 05 1 1714 26 95 9007 35 10 1 1731 2700 9024 35 15 1 1747 27 05 9040 35 20 1 1764 27 10 9057 35 25 1 1781 2715 9074 35 30 1 1798 27 20 9090 35 35 1 1814 27 25 9107 35 40 1 1831 27 30 9124 35 45 1 1848 27 35 9141 35 50 1 1864 27 40 9157 35 55 1 1881 27 45 9174 35 60 1 1898 27 50 9191 B5 65 1 1915 27 55 9207 35 70 1 1931 27 60 9224 35 75 1 1948 27 65 9241 35 80 1 1965 27 70 9258 35 85 1 1981 27 15 9274 35 90 1 1998 27 80 9291 35 95 1 2015 27 85 9308 36 00 1 2032 27 90 9324 27 95 9341 28 00 9358 For values not shown in table interpolate or use equation Pflow Pflow Pcf Base 29 92 Pcf Pressure Conversion Factor P base Assigned Base Pressure of 29 92 inches mercury absolute flow Laminar Inlet Pressure inches mercury absolute The equation can be used up to and including two atmospheres absolute It will be necessary to calibrate laminars for pressure exceeding above 12 Table A 31986 Air Viscosity Correction Factors for Base Viscosity 181 87 Micropoise at 70 F 1 C
8. 501 440 13 meriam a ScottFetzer company User s Manual Laminar Flow Elements 10920 Madison Avenue Cleveland Ohio 44102 Tel 216 281 1100 email meriam meriam comsWeb www meriam com 1 TABLE OF CONTENTS Subject Page Introductiol n de ero eto gp rone teertea dete dr ai b RU P EIS 3 Inspection go tereti ue t oca 3 Installation z 5e 4 REO RS PEU ses ie Rn DM ca roc ott p preci ds see MOM D LE 3 E 4 Typical Installations ei een n Ra e ete IT n IM ue tede eter in ite 4 Calibration oro Ep ot ED Eee ede petas 5 Actual Standard and Mass Flow Equations sss eee enne 5 7 Reading your Laminar Flow Element nennen nnne 9 Correction Factor Tables Curves Aur Humidity for Density eee RE ENTRE TH 8 Air Humidity for Viscosity eR RENT RH ORI GR ete bee 8 5s ceo Ente da ttbi 12 LABOUR 13 Terniperature Viscosity see et Re HE Gaia UE EU tv DEC Ie t Ri UR eas RH EHE Re EROR CR Tte tu 14 E E M fades 15 rh oou o eb org re rh oi e eds 14 Troubleshooting J C RE RN Oe or ENS A Gol REDE QU A iNet ods 15 EFE Dimetisions ene Roe eR e es vr edes ent edle oe fou i eem RE states eed 1
9. 6 xx 9 16 gom ENDS Ss BODY SS HALF COUPLING s PROP s 1 2 7 16 3 512 27 6 a 858 12 4 NI 8 2 7 16 4 1 2 2 76 10 03 5 2 13 2 2 7 16 59 6 8 2 7 16 12 12 3 4 12 7 6 2 8 2 776 8 6 5 8 2 7 16 we 6 12 17
10. 7 Introduction Because of their inherently high accuracy stable calibration excellent response time and repeatability Laminar Flow Elements LFEs excel in critical gas and air flow measurements and are frequently utilized in validating calibration standards Standard models are available to measure as little as 0 2 SCCM 5 9 E 06 SCFM to as much as 2250 SCFM at standard conditions Custom models for up to 15 000 SCFM of air are available Stainless steel or aluminum materials make LFEs compatible with most gases and flow rate of gas mixtures can also be measured when the percentages of component gases and mixture properties are known Higher accuracies can be achieved when used in conjunction with the Meriam MDT500 multivariable transmitter and software package The LFE matrix is made from individual SS tubes or windings of SS foil these tubes are long enough relative to their inside diameter to cause laminar flow to occur inside each tube the result is a near linear relationship between DP and flow rate The DP generated across the matrix responds very quickly to changes in flow and pressure loss to the system is reduced as each LFE is sized to produce no greater than 8 water column at maximum flowing conditions Individual tube diameters are very small so flowing gases need to be clean and dry to preserve the calibration Filtered inlet versions of most LFE models are available to keep the matrix clean and the calibration constant This manual
11. actor the pressure correction factor Pcf and the temperature correction factor Tcf This product will give the flow rate of a particular gas at the standard conditions 2 At flowing inlet conditions equal to the standard conditions read curve table directly in standard volumetric flow rate 10 Actual Volumetric Flow Rate 1 To obtain actual volumetric flow rate if the inlet temperature is different from standard temperature read the flow rate Q from the curve corresponding to the corrected DP Calculate the viscosity at the flowing temperature using the viscosity equation for the flowing gas Then calculate the viscosity correction factor using viscosity constant from curve table Clit ata pe tari ERAN H flowing gas viscosity at flowing temperature Multiply Q by the viscosity correction factor ucf This product will give the flow rate of a particular gas at the actual flowing conditions 3 At flowing inlet temperature equal to the standard temperature read the curve table directly in actual volumetric flow rate 11 Table A 31031 Meriam Laminar Flow Element Pressure Correction Factor any Gas Base Pressure Assigned Standard 29 92 Inches Mercury Absolute LAMINAR INLET LAMINAR INLET LAMINAR INLET LAMINAR INLET LAMINAR INLET PRESSURE INCH PRESSURE INCH PRESSURE INCH PRESSURE INCH PRESSURE INCH HG ABS Pcf G ABS Pcf 26 00 8689 34 15 1 1413 26 05 8706 34 20 1 1430 26 10 87
12. am and 5 diameters of straight pipe downstream of LFE Pipe size should be same as LFE outlet size e g 2 on LFE means 10 diameters of pipe Clean or check instrument connecting line If plugged replace with matched pair Meriam part 31650 Detect and repair Use small volume and equal volume connecting lines to readout device See Installation on page 4 Do not use reducers immediately before or after LFE Use at least 10 diameters of straight pipe upstream of LFE Detect and repair When you decide to have your LFE cleaned please be aware of the various capabilities of calibrating LFE s at Meriam Every calibration includes 6 8 calibration points differential pressure 1 8 H2O a data sheet with raw and reduced data calibration curve and instruction manual The procedure numbers are noted in parentheses Calibrations NIST Traceable Certificate Accuracy Reading Clean per A33555 and calibrate per A35822 Working Master X 0 72 Clean per A33555 and calibrate per 35822 Master Master X 0 54 R As Received calibration A35822 A34777 clean and calibrate WM X 0 72 R As Received calibration A35822 A34777 clean and calibrate MM X 0 54 R Accredited calibration ISO IEC 17025 contact Sales for details X 0 64 Nuclear safety application A33544 X 0 72 R Subcontracted per 35352 X 0 50 R Options 2 additional calibration poin
13. e water temperature reference must be given The calibration curve uses 4 C for the water temperature reference Some devices use a water temperature reference of 20 C and others may use other temperature references If no temperature reference is givenon the DP instrument or in its instruction manual consult the manufacturer If the DP measuring device has a water temperature reference other than 4 correct the DP reading by using the following equation density of H20Qtemperature temperature ref density of H20 4 C Water Temperature Water Density Ibs ft 4 0 C 39 2 F 62 426 20 0 C 68 0 F 62 316 15 5 C 60 0 F 62 366 21 1 C 70 0 F 62 301 The DP 4 C value should be used with the curve table Standard Volumetric Flow Rate The word standard when associated with flow rate means the flow rate has been normalized to an assigned standard pressure and temperature If standard volumetric flow rate is desired the actual volumetric flow rate is multiplied by the ratios Standard temperature Tstd flowing pressure Pf flowing temperature Tf standard pressure Pstd Be sure to use the same absolute units for pressure i e PSIA mm Hg absolute and temperature K or R The result is the standard volumetric flow rate at the given standard conditions i Tstd Pf Standard volumetric flow rate Actual volumetric flow rate x This equati be rewritten
14. f 1 4 I D hose tubing or pipe All instrument connections must be leak free Install temperature sensor 2 diameters upstream of the element Inlet absolute pressure instrument when needed must be connected close to the LFE at the inlet pressure tap Figure 1 shows several typical LFE installations Install the LFE in the line using hose connectors flanges tubing or pipe as desired Position the LFE in any orientation Horizontal is the most common Orient the high pressure and low pressure sensing ports in any angular direction Flow must be in the direction of the arrow on the LFE Avoid disturbances upstream of the LFE Good measurement practices dictate an adequate straight run of the pipe up and downstream of the element In most installations 10 diameters upstream and 5 diameters downstream are adequate Where installation makes straight pipe runs impossible LFE s can be calibrated with piping configurations that duplicate installation This special calibration assures installed accuracy In these applications consult Meriam regarding calibration Operation Establish flow through the LFE Measure the differential pressure between high pressure sensing port and low pressure sensing port Measure the inlet gas temperature For standard or mass flow rates measure absolute line pressure Refer to calibration curve table instructions for flow rate
15. fy Meriam if your flowing gas is not air and or standard conditions are different from 70 F and 29 92 Hg absolute A special curve table can be provided listing the gas being flowed The gas viscosity correction ustd uf will reference the gas and or new standard temperature value if applicable Table A 32422 or A 31986 cannot be used for gases other than air Gas Flow Other Than Air Standard Conditions From 70 F and 29 92 Hg ABS Select the proper flow curve table for the LFE being used Standard Volumetric Flow Rate 1 To obtain standard volumetric flow rate if the inlet temperature and pressure are different from standard read the flow rate Q from the curve table corresponding to the corrected differential pressure DP Calculate the viscosity at the flowing temperature using the viscosity equation for the flowing gas Then calculate the viscosity correction factor using Viscosity constant from curve table ee MUERE flowing gas viscosity at flowing temperature Locate the pressure correction factor Pcf for the flowing inlet pressure on chart A 31031 or calculate the correction factor using Pef absolute inlet line pressure cf 1 absolute standard pressure Locate the temperature correction factor Tcf for the flowing temperature on chart A 35700 or calculate using Tef absolute standard temperature cf 1MM absolute flowing temperature Multiply from the curve table by the viscosity correction f
16. nd if necessary the DP across the LFE 2 Measure and record the inlet temperature always and absolute line pressure for standard or mass flow rates Convert both values to absolute units 3 Follow the AIR FLOW or GAS OTHER THAN AIR guidelines below Model 50MK10 All Other Models Flow Q Flow Q 4 Differential Pressure Inch of Water 4 C Differential Pressure Inch of Water 4 C Air Flow Select the proper flow curve table for the LFE being used Standard Volumetric Flow Rate 1 To obtain standard volumetric flow rate if inlet pressure and temperature are other than 29 92 Hg absolute and 70 F respectively find the flow rate Q that corresponds to the corrected DP Multiply Q by temperature viscosity and pressure corrections shown on charts A 32422 and A 31031 respectively to bring flow to standard conditions of 29 92 Hg and 70 F 2 At flowing conditions of 70 F and 29 92 Hg read curve directly in standard volumetric flow rate Actual Volumetric Flow Rate 1 To obtain actual volumetric flow rate at inlet flowing temperature other than 70 F find the flow rate Q that corresponds to the corrected DP Multiply Q by the viscosity correction only See chart A 31986 for corrections 2 At flowing inlet temperature of 70 F read curve directly in actual volumetric flow rate Actual volumetric flow rate equals standard volumetric flow rate when flowing conditions are 70 F and 29 92 Hg Noti
17. opoise of the gas at flowing temperature in the Correction Factor equation Table A 35700 Temperature Correction Factor Base Temperature 70 F Ter 329 67 459 67 F Maintenance Accumulation of dirt in the capillaries of the laminar element will affect the accuracy When in doubt hold the laminar in front of a high intensity light sighting through the capillaries Any dirt will be apparent Loose dirt can be blown out with shop air no more than 100 PST in reverse direction of flow Shop air must be clean and dry Brushing or rubbing the ends of the matrix element is not recommended because the matrix can be deformed altering the calibration Unless the customer has the facilities and primary standards to check calibration after cleaning we recommend returning the unit to Meriam for cleaning and calibration 14 oF Problem Low or High DP Indication Pulsating Irregular Reading Troubleshooting Probable Cause Insufficient or improperly sized straight pipe downstream and or upstream of LFE One or both differential pressure connection taps plugged If pulsation dampener is used check stones Model 50 MR2 and 50 MC2 only Leak in line between LFE and readout device Large volume and or unequal volume connecting lines to readout device Piping reducers at inlet and or outlet Irregular flow pattern entering LFE Leak in system line 15 Remedy Use 10 diameters of straight pipe upstre
18. orrection Factor Hg 81 7 Note These correction factors do not correct for volume changes due to temperature 1 03034 1 01487 1 0000 0 98568 0 97189 0 95860 0 94578 0 93340 0 92144 0 90989 0 89871 1 02877 1 01336 0 99854 0 98428 0 97054 0 95729 0 94452 0 93219 0 92027 0 90875 0 89761 1 02720 1 01185 0 99709 0 98288 0 96919 0 95600 0 94327 0 93098 0 91910 0 90762 0 89652 1 02564 1 01035 0 99564 0 98149 0 96785 0 95470 0 94202 0 92977 0 91794 0 90650 0 89543 1 02408 1 00885 0 99420 0 98010 0 96651 0 95341 0 94077 0 92857 0 91678 0 90537 0 89434 13 1 02253 1 00736 0 99277 0 97872 0 96518 0 95213 0 93953 0 92737 0 91562 0 90425 0 89326 1 02099 1 00588 0 99134 0 97734 0 96386 0 95085 0 93830 0 92618 0 91446 0 90314 0 89218 1 01945 1 00440 0 98992 0 97597 0 96253 0 94957 0 93707 0 92499 0 91331 0 90203 0 89110 1 01792 1 00292 0 98850 0 97461 0 96122 0 94830 0 93584 0 92380 0 91217 0 90092 0 89003 1 01639 1 00146 0 98709 0 97325 0 9599 0 94704 0 93462 0 92262 0 91103 0 89981 0 88896 Table A 32422 Air Temperature Viscosity Correction Factors for SCFM Air Base Temperature 70 F 181 7 Micropoise Reference NBS Circular 564 529 67 181 7 xX 459 67 F yg ir 14 58 a 3 pair 58x 1s 2 459 674 1 8 Correction Factor 110 4 When flowing gas other than air use the viscosity in micr
19. s the actual volumetric flow rate The curve table lists the type of gas used to generate the curve table Actual volumetric flow rate B x DP x DP 897 uf 5 To help calculate the viscosity of air at flowing temperature a viscosity equation based on temperature 1s included in this instruction manual see Table A 32422 The equation is from tables of Thermodynamic and transport Properties of Air Argon Carbon Dioxide Oxygen and Steam All other gas viscosity equations are obtained from Physical and Thermodynamic Properties of Pure Chemicals Table A 31986 lists the values of ustd uf for air from 50 159 F at 1 intervals when the standard temperature is 70 F Note If you are flowing wet air a humidity correction factor for viscosity must be used The difference between wet air viscosity uwet and dry air viscosity dry increases with temperature and humidity at 80 F and 80 relative humidity the ratio of uwet udry is 997 Figure 2 is a graph of the ratio uwet of air from 50 to 150 F and from 10 to 90 relative humidity The viscosity of the flowing wet air becomes the value from the dry air viscosity equation times the ratio uwet udry A 14 58 0 Bt pwet air 7110 44 T udry Where T K The curve table may have DP units of 1 inches of water column WC 2 centimeters of WC 3 millimeters of WC 4 pascals 5 kilopascals Whenever a pressure is expressed in units of water th
20. ts beyond full scale up to 12 20 Additional calibration points beyond full scale at the following settings Additional calibration points below 1 H20 at the following settings Oxygen cleaning per 50558 Calibrating the LFE with differential pressure transmitter Hydrostatic leak testing per A33559 Pneumatic pressure test per 70763 The standard reference unit for flow rate 1s cfm cubic feet per minute The additional units available are Liters Cubic Centimeters Meters Pounds include flowing temperature and pressure Kilograms include flowing temperature and pressure Other 1me constants Second Minute Hour e standard reference for differential pressure is inches of water at 4 C The additional units available are Millimeters of water 4 C Centimeters of water 4 C Pascals Kilopascals T Other weer verve DS A second data sheet and calibration curve using the listed units will be included with the calibration 16 B DIA HOLES ON C BOLT CIRCLE LFE Dimensions 31 8 1 4 NPT EA pM n y je 8 MODEL 50MY15 SIZE SS BODY amp FLANGE SS HALF COUPLINGS SIZE B DIA C SIZE A B DIA 2 1 2 4 3 4 5 1 2 8 8 7 8 11 3 4 3 4 3 4 6
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