WPC 2U ZB 0XXxPQXPЫXxPQXP2xA`Univers (WN)XXx6X@QX@<6X9`("Courier New (TT)XXx6X@QX@<6X9`("Courier New (TT)XXx6X@QX@<6X9`("Courier New (TT)XXx6X@X@<09Z 0Courier (W1) RegularXXx6X@X@< 09Z 0Courier (W1) RegularXXx6X@QX@<6X9`("Courier New (TT)X23| ,  X   XX #Xx6X@QX@#yxdddy Prepared by Peter R. Westlin , EMC*DD/4 EMTIC GD031 Emission Measurement Center, OAQPS*DD/4March 14, 1995`%%P yxdddyX` hp x (##Xx6X@QX@#gX#Xx6X@QX@# XX X` hp x (#X` hp x (#%'0*,.8135@8:2Q_i ~~=~~17.65~V_i~~{{P_b} over {T_m theta_i}} >߻ڐ#<dd<7+q_i~=~17.65~v_i~~{{P_b} over {T_a~theta_i}}7ߴڐ  Where:  v=` ` ` Volume recorded on the total flow gas meter, corrected by the meter calibration factor, scf.  Pb=` ` ` Barometric pressure, in. Hg.  Tm=` ` ` Temperature of the total flowgas meter, R.  i=` ` ` Elapsed sampling time, min.  vi=` ` ` Volume recorded on partial flowgas meter, corrected by the meter calibration factor, scf.  Ta=` ` ` Room temperature, R.  17.65=` ` ` Standard temperature and pressure correction factor, viz. #@<dd@<."{528 DEG R} over {29.92~ \in.~ Hg}.߫  Calculate the mean total flow rate,  Q , and the mean of the  partial flow rate,  q : #<dd<?3 OVERLINE Q ~ =~ {sum from {i`=`1} to n Q_i} over n?߼ڐ#<dd<=1OVERLINE q~ =~ {sum from {i`=`1} to n q_i} over n=ߺڐ  Where: n=` ` ` Number of sampling holes. 3.2Determine the percent deviation, Q, from the mean total flow rate: #<dd<XLDELTA Q~=~{OVERLINE Q~ ~ sum from {i`=`1} to n q_i} over OVERLINE Q~ x~ 100Xڐ If a Q greater than 10 percent is found, indicating the total flow rate is too low for the probe design or the sample holes are too large, repeat the test with a redesigned probe or a revised flow rate.  3.3Determine the percent deviation, qi, from the mean partial flow rate for each hole: #<6dd<H<DELTA q_1~ =~ {q_1~ ~ overline q} over {overline q}~ x~ 100H All qi must be within + 10 percent for an acceptable probe ""Jdesign at the design flow rate. SUMMARY AND DISCUSSION OF TEST RESULTS Method validation tests were performed in the laboratory using three different multihole probes. All three probes had similar internal diameters of 0.375 inches and each had three sample equalsized sample holes: 0.078 in. for probe 1, 0.125 in. for probe 2, and 0.203 in. for probe 3. The results of the test are summarized in Table 1. These test results demonstrate the importance of properly setting the total flow rate for the probe. For example, at similar flow rates of about 48 scfh, probe 1 (I.D. = 0.078 in.) showed that the sum of partial flow rates totaled within 10 percent of the measured total flow rate while probe 2 (I.D. = 0.125 in.) showed almost 25 percent difference between these two figures. This indicates that the slight pressure drop associated with the partial flow drygas meter greatly affected the partial flow rates of probe 2, because of the larger sample holes, and was a limiting factor in the partial flow measurements. The result is a false indication of the operation of the probe. The second criterion set by the method is that the partial flow rates all be within 10 percent of the average partial flow rate. These results indicate that this criterion can be met if the total flow rate is sufficient to cause a probe pressure of about 10 in. water. Of course, the pressure drop at each sample hole includes the pressure drop associated with the drygas meter and the tubing connectors during the measurements. This makes it of prime importance that the drygas meter be of high quality (i.e., low pressure drop), and the tubing and connectors be of larae diameter and as short as practical. One limitation in the use of multihole probes brought out by these results and by the work of others3 is that very small sample holes are required to maintain adequate pressure drop to assure approximately equal flow. The results of this study indicate a hole diameter of 0.125 in. is about the upper limit for a 1.0 cfm probe. This restriction limits the applicability of multihole probes to stack gases with low particulate concentrations to avoid probe plugging problems.  X, ( Ã TABLE 1, SUMMARY OF RESULTS OF THE FLOWRATE EVALUATIONS OF MULTIPOINT SAMPLING PROBES ,ddxU((((" ,ddxU((((" .pp.Hole Diameter (in.)Probe Pressure (in. H2O)Average Total Flowrate (SCFH)Average Partial Flowrate (SCFH)Percent Deviation From Total (Q, %)Percent Deviation Per Hole qa qb qc (%) (%) (%).((.0.078ܩ1.2 3.1 6.4 10.1 16.4 35.319.4 31.8 47.4 60.1 74.6 108.85.7 9.5 14.3 18.2 23.5 33.311.7 10.7 9.1 9.2 5.3 8.20.9 7.1 5.2 6.9 4.3 3.4ܩ1.2 6.2 2.6 6.5 0.4 3.30.4 0.8 2.6 0.3 3.9 0.1.``.0.125ܩ1.1 3.4 7.0 10.9 14.547.9 83.7 124.7 148.3 170.012.3 25.6 36.9 46.7 51.323.0 8.3 11.3 5.6 9.46.5 10.8 10.8 5.5 11.2ܩ5.8 0.7 8.7 0.8 3.9ܩ0.9 10.1 2.0 4.8 7.4..0.203ܩ1.1 3.2 5.475.5 131.9 173.714.8 34.5 46.341.3 21.5 20.042.2 23.3 23.3ܩ2.4 2.1 1.4ܩ39.9 25.3 21.9  ,  X REFERENCES 1.Performance Specification 2 Specifications and Test Procedures for SO2 and NOx Continuous Monitoring Systems in Stationary Sources, Environmental Protection Agency, Emission Measurement Branch revision, May 1979. 2.Westlin, P. R. and R. T. Shigehara, Procedure for Calibrating and Using Dry Gas Volume Meters as Calibration Standards, Source Evaluation Society Newsletter, Vol. 3, No. 1, February 1978. 3.Technical Manual for Process Stream Volumetric Flow Measurement and Gas Sample Extraction Methodology, prepared for EPA, IERL, PMB, by TRW Systems Group, Contract No. 68021412, November 1975.