Document JNjr9L1Qd9wnwN10DKr0B1NdO

Vista Chemical Company t ft 15990 North Barker's Landing Road Post Office Box 19029 Houston, Texas 7722-1 Phone (713) S31-3200 March 9, 1989 Ms. Meredith N. Scheck The Vinyl Institute Wayne Interchange Plaza II 155 Route 46 West Wayne, NJ 07470 Re: FUGITIVE EMISSION BAGGING Dear Meredith: Our Aberdeen, MS plant recently received the results of a fugitive emission bagging study done by a contractor, TEAM Inc. The results of the study were so favorable that I thought it would be worthwhile passing them along to other VI members so they could get a better idea of the benefits of such a study. TEAM did site bagging work the week of November 28, 1988, Thirty seven components were subjected to bag sampling; 16 valves, 19 flanges, 2 compressors. In general, the study showed that the SOCMI stratified leak factors correctly characterized the fugitive emissions from a leaking component. However, the number of leaking components in our plant (and probably most PVC plants) is very low. The study showed that the EPA factor for non-leaking components overestimates fugitive emissions by a considerable amount. By using the factors derived from the bagging study, Aberdeen fugitive emissions were lowered to 15% of the level reported under SARA 313 last year. The cost of our bagging study was approximately $20,000. We were able to keep the cost down by doing a screening of all the components in the plant ourselves. This screening is needed to determine the percent of components leaking. The cost of che project would have been higher if TEAM did the screening. Since there has been interest among some members of the VI Health, Safety, and Environment Committee in bagging, I suggest you distribute this memo to the Committee members. I have attached selected pages from the report describing the process. Sincerely, jos*ph C. Ledvina Director, Environmental Activities dlj Attachment VVV 000005145 ABSTRACT The purpose of this study was to present accurate mass emission estimates for components in vinyl chloride (VCM) service at Vista Chemieal Company, Aberdeen, Mississippi. Screening data, supplied by Vista Company, along with response factor testing and bagging data generated by Team. was used t-o compile the emission estimates for VCM. inc. The testing was concentrated in the new module and old module sections which were considered identical (sister) units by Vista Chemieal Company. Tha unit boundary also Incorporated the compressor shed and tank farm as part of the testing region. Data gathered from testing of the VCM areas was compiled and used to compute the VCM emissions from the process. Emissions estimates were calculated using five different computation methods. The factors used, along with the data requirements were as follows: METHOD OATA REQUIREMENTS (1) Average SOCMt factors factors Accurate component counts (2) Leak/no leak factors Accurate component counts, screening data, response factor data (3) Stratified factors Accurate component counts, screeninq data, response factor data (4) EPA correlations with 6PA "default zero" emission rates Accurate component counts, screening data, response factor data, bagging data C5) EPA correlitiont with "default zero" emission rates from bagging Accurate component counts, screening data, response factor data, bagging data Calculations using the bagging data from emitting sources yielded the EPA correlations for valves (LI) and valves (gas) reasonably fit the process under study. The EPA correlation for flanges was observed to overestimate emissions from the process under study, but was still used to generate conservative emission es timat es. Bagging data from "zero" sources yielded statistically different emission rates for valves (light liquid) and flanges from that of the EPA "default zero" emission rates. The "default zero" emission rates from bagging were used to calculate emissions from components screening at "zero" for these sources. Pumps, compressors, and valves (gas) "zero" components emissions wjsre calculated using the EPA "default zero" emission rates. A summary of total emissions from each method in pounds per hour may be found in Appendix K, page K-1. VVV 000005146 OneStep INOEX SYSTEM * TV; 1. . . 5 L - A ft < ABSTRACT DEVELOPMENT OF EMISSION ESTIMATES i e * APPENDIX A: METHOD 21 APPENDIX B: ESTIMATE OF FUGITIVE EMISSIONS USING AVERAGE SOCMI FACTORS APPENDIX C: HNU SCREENING DATA c APPENDIX D: RESPONSE FACTOR GENERATION AND ADJUSTED HNU SCREENING DATA 6 APPENDIX E: ESTIMATE OF FUGITIVE EMISSIONS USING LEAK/NO LEAK METHOD AND STRATIFIED METHOD APPENDIX F: PARAMETERS AND PREDICTION EQUATIONS FOR NONMETHANE LEAK RATE FOR VALVES, FLANGES, AND PUMP SEALS 8 APPENDIX G: BLOW-THROUGH METHOD AND'BAGGING FIELD DATA 9 APPENDIX H: STATISTICAL AND GRAPHICAL COMPARISONS OF EPA CORRELATIONS VS, BAGGING DATA Q- ^ J VVV 0000051^7 OneStep* INOEX SYSTEM H - f Con terns. APPENDIX I: ESTIMATE OF FUGITIVE EMISSIONS USING EPA CORRELATIONS WITH EPA "DEFAULT ZERO" EMISSION RATES AND EPA CORRELATIONS WITH "DEFAULT ZERO" EMISSION RATES FROM ** -f BAGGING DATA_____________ _* APPENDIX J: DEVELOPMENT OF PROCESS SPECIFIC "QEFAULT ZERO" EMISSION RATES ** ^ APPENDIX K: FUGITIVE EMISSION ESTIMATE SUMMARY 3 REFERENCES 4** 5 6 7 8 9 10 VVV 0C000514U 2.0 DEVELOPMENT OF EMISSION ESTIMATES 2.1 INTRODUCTION In this section, the five methods used to compute the VCM emissions from equipment leeks in the VCM processing area are outlined end explained. Data collection technique and data analysis methods used are explained in detail in this section and with the use of the appendixes for each method. The most recent EPA protocol (reference 1) and the latest CMA protocol (reference 2) were adhered to very closely in compiling data and computing emission estimates. They will be referenced often and supplementary references should be sought through the reference list included in those protocols,.... ......... ..... ------- ----------- ------------------------- 2.2 AVERAGE EMISSION FACTOR METHOD Ail methods of calculating emissions required an accurate component count by type of equipment and-by service. Application of the EPA average emission factors to equipment counts for the unit are used to calculate emissions. The EPA average emission factors are shown in Table 2-1 (reference 1 page 2-2) on the following page. The product of the emission factor and the number of equipment components are summed to generate the unit specific emission estimates (reference 1, page 2-1). The results of the emission estimates for VCM uainq the average emission factors may be found in Appendix 8. page B-1. 2.3 LEAK/NO LEAK METHOD The leak/no isak method requires screening of ail equipment included in the inventory using a portable analyzer. Screening data of the VCM processing area using an HNU analyzer was supplied by Vista Chemical from a monitoring program performed in Oeeember, 1988. A list of the HNU screening values may be found in Appendix C, pages C-t C-2. The HNU screening values were adjusted by response factors to yield actual VCM concenI rat ion (ppmv). The laboratory generated response factor data and computation methods were performed by Team, Inc. A detailed explanation of the response factor generation for the HNU to actual concentration of VCM may be found in Appendix 0, page 0-1. The edjusted HNU screening values ere listed in Appendix 0, pages 0-5, D-6. The leak/no leak approach Is based on two emission rates: an emission rate for sources that "leak*1 (screening concentration above or equal to 10,000 ppmv) and an emission rate for sources that do not "leak" (screening concentrations less than 10.000 ppmv). Table 2-2 (reference 1. page 2-6) presents the leaking and non-leaking emissions factors for the different source/services. 2-1 yVV Q000051*9 TABLE 2-1. AVERAGE EMISSION FACTORS FOR FUGITIVE EMISSIONS Equipment Valves Pump Seals Compressor Seals Pressure Relief Seals FIanges Open-Ended Lines Sampling Connections Service Gas Light Liquid Heavy Liquid Light Liquid Heavy Liquid Gas/Vapor Gas/Vapor All All All Emission Factor (kg/hr/source) 0:0056 0.0071 0.00023 0.0494 0.0214 0.223 0.104 0.00083 0.0017 0.0150 2-2 VVV 000005150 TABLE 2-2. LEAKING AND NON-LEAKING EMISSION FACTORS FOR FUGITIVE EMISSIONS j[kg/hr source) __ Equipment Valves Service Leaking (>10,000 ppm) Emission Factor Non-leaking (<10,000 ppm) Emission Factor Gas* LL*"?V HLC 0.0451 0.0852 0.00023d 0.00048 '0.00171 0.00023 Pump Seals LL 0.437 0.0120 HL 0.3885 0.0135 Compressor Seals9 Pressure Relief Valves FIanges Open-Ended Lines Gas Gas All All 1.608 1.691 0.0375 0.01195 0.0894 0.0447 0.00006 0.00150 ` *The 1 taking and non-leaking emission factors for valves In gas/ vapor service aro based upon the emission factors determined for gas valves In ethylene, cumene, and vinyl acetate units during the SOCMI Maintenance Study. References 8 and 15. bLL - light liquid service. CHL - heavy liquid service. ^Leaking emission factor assumed equal to non-leaking emission factor since the computed leaking emission factor (0.00005 kg/hr/ source) was less than non-leaking emission factor. 'Emission factor reflects existing control level of 60 percent found In the Industry; control Is through the use of barrier fluid/degassing reservolr/vent-to-flare or other seal leakage capture system. 2-3 WY 000005151 'l The adjusted screening inventory for VCM yielded all non-leaking components. The product of the total number screened in each sour ce / IS r v.i ce .and the non-leaking emission factor for the source/service was calculated and an average emission rate for each source/serv i ce screened was'computed. The total component count for each s^a. (Including those-not screened because' of difficult to nonitor situations) multiplied by the average emission rata for those screened in each s/s was used to generate the emission estimate for each category. The results of emissions using the leak/no leak approach may be found in Appendix E, page -1. 2.4 STRATIFIED EMISSION METHOD Another approach that requires accurate screening data is the stratified emission method. The stratified emission method is based on three different ranges, each having an emission rate for different s/s. The three ranges used are: C 1 ) 0 - I ,000 ppmv (2) 1.00 1 - 10,000 ppmv (3) > tO.000 ppmv Table 2-4 (reference 1. page 2-10) presents the emission rates for each strata by equipment type and service. As with leak/no leak, the HNU screening values were adjusted by the properresponse factor to yield actual concentration Cppmv). The screening eoncentrations for each s/s were multiplied by the p r o p e r s t r a t_a em i s a o n rateand, an average emission rate for' eVch s/s screened was computed. The total components in each a/s was then used with the average emission rate for that s/s to generate the emission estimate. The results of the stratified emissions calculations may be found in Appendix E , page 6-2. 2.S EPA LEAK RATE/SCREEN ING VALUE CORRELATIONS Mathematical correlations relating OVA measurements taken using Method 2 1 -to mass emission rates have been published by EPA. The EPA correl ations fgj.vaIves C l Ight liquid), valves (gas), pumps and flanges are shown in Appendix F (reference 1, page D-1), Pages F-1, F-2. Bagging data for VCM emitting sources was gathered using t.he BLOW-THROUGH METHOO of bagging. The results were used to check the fit of the EPA corrsiationa to the VCM processing area. A graphical comparison and a statistical analysis yielded that the EPA correlations for valves (light liquid), and valves (gas) were an adequate representation for valves (light liquid) and valves (gas) in tha VCM processing area. The EPA correlation for flanges was observed to over estimate flange emissions for the VVV 000005152 Xl-_____ ......... 'A TABLE 2-_4. STRATIFIED EMISSION FACTORS FOR EQUIPMENT LEAKS (kg/hr/source) Source Compressor seals Pump seals Valves Flanges, connections Pressure relief devices Open-ended lines Service , :i Gas/vapor Emission Factors (kg/hr/source) for Screenlnq Value Ranqes, oomv 0-1,000 1,001-10,000 Over 10,000 V k' l' r 1 li` 0,01132 0.264 1.608 Light liquid Heavy liquid 0.00198 0.00380 0.0335 0.0926 0.437 0.3885 Gas/vapor Light liquid Heavy liquid 0.00014 0.00028 0.00023 0.00165 0.00963 0.00023 0.0451 0.0852 0.00023 All 0.00002 0.00875 0.0375 Gas/vapor 0.0114 0.279 1.691 All 0.00013 0.00876 0.01195 2-5 VVV 000005153 ti VCM processing area. However, the EPA correlation for flanges could stiM.be u ae.d as. ,a.=.con isc va t i ve thod - fo r estimating flange emissions. The bagging method used and the calculation procedures may be found ln_Appendlx G, pages. G-1 thru G-6 -- . t_reLrr.aiic.e ,2~.-pages '99-103)-;--Thebagging field data, graphical comparison and statistical analysis for the VCM area under study may be found in Append.!* H, pages thru H-a." Emissions were calculated for VCM emitters from ths HNU monitoring survey completed by Vista in December 1988. The HNU screening values were firat adjusted by appropriate response----- 'fa c t or * t a y i e f d equ T v a I en t OVA/me t hane screening values (reference 1, page 2-9). The equivalent OVA/methane screening values were then adjusted by appropriate OVA response factors to yield actual concan t r a_t j p.n a <J,P r OVA/methane ppmv- over the entire rYnge of screening values (reference 1. page 2-12). The adjusted equivalent OVA/methane concentrations were used with the EPA correlations to generate emissions from emitting sources. Response factor data and generation for the HNU to OVA/Methane adjustment and OVA to actual ppmv adjustment may be found in Appendix D, pagea 0-1 thru 0--11. 2.8.1 EPA CORRELATIONS WITH EPA "DEFAULT ZERO* VALUES In order to use the EPA correlations to generate emissions a separate treatment of "zero" components (sources that screen below the Instruments lower limit of detection) has to be coasidersd. EPA hee derived a "default zaro" OVA/Methane screening value of 6 ppmv and an aseoeiated mass emissions rate for the screening values between zero and the "default zero1' reading. These "default zaro" emission rates are shown below (reference 1. pegs 2-12). , =------ -------- ------ Zero Screening ------------------- ------~ "Default Zero- Equipment Tm/Servka 3cregnlnq_yalue. pom Value Emission Rate ncq/hr/soureet Valves, gas Valves, light liquid Flanges Pumps and all other components 8 8 8 8 0.000033 0.0Q0451 0.000093 0.000039 "These emission factors should be applied to equipment components screening between 0 end 8 ppm. The published correlations would be applied to all screening concentrations above 8 ppm. The total emissions estimate for equipment leaks is generated by totaling emissions estimates for ell "default zeros" and adding that total to the total estimates generated using the correlations." (Reference 1, page 2-12) The adjusted equivalent OVA screening values from the VCM area monitoring wera used with the EPA correlations along with the proper "default zero" emission rate to generate an average emission rate for each s/a under study. The total component count for each s/s In the VCM area was then used with the calculated average emission rate to generate the emission estimate for each s/e. Results of these calculation may be found in Appendix I, pages (-1 thru i-5. VVV 000005154 i 2.6.2 EPA CORRELATIONS WITH "OEFAULT ZERO" EMISSION RATES FROM BAGGING OATA Bagging data for '* 2r o" components in the VCM area for various s/s was also collected and analyzed. A statistical test comparing the existing EPA "default zero" emission rates and the "default zero" emission rate from bagging was computed and used to determine - I f tha "defai/l f^ero" rate from bagging was t iT riY'tfl fferVrf t' row' that of'the EPA "default zero" emission rata. The statistical test used is outlined in Appendix J. pages J-t thru J-S (reference 1. pages G-1 to G-3). The results of the statistical lest rtvealed that for valves flight liquid) and flanges the "default zero" emission rate from bagging data was statistically different from the EPA "default zero" emission rates. The "default zero" emission rate from bagging data for valves (gas) however, was not found to be statistically different from the EPA "default zero" emission rate. The "zero" bagging data summary and statistical analysis for each s/s may be found in Appendix J, pages J-6 thru J-8. Therefore, the EPA correlations along with the "default zero" emission rates from bagging were used to calculate emissions from valves (light liquid) and flanges as in section 2.6.1 above. The results of these calculations are shown in Appendix I, pages I - 6 thru 1-8. One should also note that even though background bags were taken at the time of bagging "zero" components, the leak rate due to background was not accounted for in the "default zero" emission rate determinations. Thus, the "default zero" emission rates from bagging may be biased high. A supplementary to this report will be generated and take into account background in*the "default 'zero" emission rate determination. The "default zero" emission rates will then be adjusted where warranted. 2.7 SUMMARY A summary table of emission estimates calculated using ail the above methods may be found in Appendix K. page K-1. All the emissions calculated are believed to be statistically valid and aeceptabie estimates for the VCM process unde t s t udy f . , . ... b t : 2-7 VVV 000005X55 I APPENDIX Q: : - i e s ; * : i s i . : i i * ? r - ? v blow-through methoo AND BAGGING FIELD DATA ^t C 5 " t : fc ; . a c. r u r. VVV 000005156 EMISSIONS CONTROL SERVICES - A TEAM COMPANY BAGGING TECHNIQUE ANO OATA THE BAGGING DATA WAS COLLECTEO USING THE BLOW-THROUGH METHOO OP 8AGGING. THE BLOW-THROUGH METHOO IS OESCRIBEO ON THE FOLLOWING PAGES ADAPTED FROM REFERENCE 2, PAGES 99 - 103. THE CALCULATION PROCEDURES ASSOCIATED WITH THE BLOW THROUGH BAGGING DATA IS SHOWN ON TABLE 4-1 ADAPTED FROM REFERENCE 3. PAGE 75. THE BAGGING DATA COLLECTION ANO CALCULATIONS FROM THE VISTA CHEMICAL VCM PROCESS STUDY WERE PERFORMED BY TEAM, INC. THE BLOW-THROUGH METHOO WAS ADHERED TO VERY CLOSELY. NITROGEN WAS USED AS THE PURGE GAS. THE ROTAMETER % WAS AOJUSTED AND LISTED IN UNITS OF LITERS/MINUTE. THE OVA READING GIVEN INSIDE THE TENT FOR EACH FLOW RATE WAS CONFIRMED 8Y TAKING SEVERAL READINGS INSIOE THE TENT UNTIL THE READINGS WERE CONSISTANT. THIS WAS REPEATED AT EACH FLOW RATE AT LEAST TWO TIMES UNTIL REPEATABLE READINGS WERE EVIDENT. WHERE NO DETECTABLE OVA READINGS WERE OBSERVED, SAMPLE WERE COLLECTED FROM THE TENT USING A PORTABLE SAMPLE PUMP AND TRANSFERED TO THE LAB FOR ANALYSIS. VISTA LAB PERSONEL PERFORMED THE G.C. ANALYSIS OF THE SAMPLE BAGS. THE TENT GAS TEMPERTATURE LISTED ALSO REFLECTED THE AMBIENT TEMPERATURE UNLESS OTHERWISE NOTED ON THE DATA SHEETS. NO MEASUREMENTS WERE TAKEN FROM THE TENTS UNTIL THE OXYGEN CONTENT WAS LESS THAN 5%. THE BAGGING OATA ANO CALCULATIONS ARE SHOWN IN THE FOLLOWING SECTION. THE DATA IS GROUPEO BY SOURCE/SERVICE IN ASCENOING ORDER BY OATA SHEET NUMBER. EACH SOURCE/SERVICE IS BROKEN INTO AN EMITTER SECTION ANO A "ZEROCOMPONENT SECTION. COMMENTS CONCERNING THE DATA COLLECTION PROCESS ARE PRINTED ON THE BOTTOM OF EACH 8AGGING OATA SHEET. . G-l VVV 000005157 tt 4.2 BLOW-THROUGH METHOD Blow-through refers to blowing nitrogen through a flexible tent to create a constant VOC concentration inside the tent. nitrogen Is metered into the tent through 1 or 2 polyvinyl chloride tubes. The temperature and oxygen concentrations are measured Inside the tent with a platinum-RTD thermocouple and an oxygen/combustible gas monitor. The flow of nitrogen is monitored In a gas rotameter calibrated to nitrogen. The nitrogen passes through activated charcoal and drlerlte to remove any organics-and moisture.- -The pressure In the tent never exceeds 1 psig. Figure 4-3 Illustrates the equipment required for the blow-through method. Tnc B L C* iHHOUCsr oMG'J'ko JA > A aHOWr* v> `Afe.i * * ' AQA-'fri- -H'>- = <-- `At least two OVA (Foxboro 108 Organic Vapor Analyzer) measurements are made Inside the tent, each measurement at two or more differing nitrogen flow rates to increase accuracy. (The OVA must be attached to a dilution probe and calibrated to nitrogen-diluted gasee to allow its use in the nitrogen atmosphere in the tent.] The OVA readings are converted to emiasion rates of VOC via response factors for the OVA; the calculation is shown in Table 4-1. Alternatively, gas samples from the tent can be collected with a portable sampling pump and transported to a lab for chemical speclation and concentration measurement., The calculation in Table 4-1 is also applicable for concentrations measured in this maimer (except that the response factor is set equal to 1) . The oxygen concentration Is also measured to determine the' total gas flow rate through the tent. However, oxygen concentration is also used to rate the quality of the tent, and except for a few extremely difficult situations, VOC : 0 r-i G-2 vvv o 0000515* cii 6-3 i1 ... cl. vvv ooooosi^v -r. Figure 4 -3 . Equipment required fo r the blow-through sampling technique. I, -:fc concentrations are not measured until the oxygen concentration in the tent is reduced below 5%. Air can replace nitrogen as a dilution gas if the hydrocarbon concentration is not expected to be high enough to cause an. explosive atmosphere inside the tent. However, calculations based on air tent data must assume a nominal tent leakage rate, i.e., extra flow through the tent due to air entering the tent that is not metered through the tubing. s. t. v v Safety has been a key factor in the development of this procedure. Over 400 valves have been tented with this technique without incident. Nitrogen is used as a dilution gas instead of air to prevent an explosive atmosphere within the tent. All of the instruments used are battery-operated and approved for Class I, Division I use. In summary, the blow-through method consists of the following steps: o Interview the unit operator to determine the composition of the material in the designated equipment component (in weight or volume %), and the operating conditions of the pump. o Screen the component by placing a Tygon nozzle on the end of the Foxboro/Century OVA (Organic Vapor Analyzer), holding the end of the nozzle within 1 centimeter of the leak interface, and recording the highest concentration seen on the OVA readout. The procedures for valves is the same/ however, the analyser does not need to be 1 cm away from the valve. o Cut a tent from appropriate material (see section 4.3 - Source Enclosure) that will easily' fiTE; over the equipment component o Connect tubing from the nearest low pressure nitrogen station to a rotameter stand, which includes a regulator, dessicant, activated charcoal, and a rotameter in series. ------------------------------------ o Run tubing from the rotameter outlet to a "Y" that splits the nitrogen flow into two pieces of tubing. Insert the tubes into openings located on either side of the tent. o Turn on nitrogen at the utilities station and regulate it at the rotameter to approximately 40 liters/minute. o After the nitrogen is flowing, wrap aluminum foil around those parts of the equipment component where air could enter the tent-enclosed volume. G-4 WW 000005160 t' --:-&~ijSe duct tap*, 'wira,'^and/or rope to secure the tent 'to the component. o Put a third hole in the tent roughly equidistant from ;:.the two. nitrogen-fed_holes. ...............- "O Measure the oxygen concentration in the tent by inserting the lead from an 0. meter into the third hole. Adjust the tent (add additional tape, foil, rope, etc.) until the 0- concentration is less than 5%. 'fl'Meaeure tfte temperature in.tbe. tent with a' A thermometer may also he used. o Calibrate the OVA to methane or hexane at a known concentration in nitrogen using the OVA dilution probe. Remember to correct for the dilution before inserting the OVA concentration reading into the calculation in Table 4-1. o Check the VOC concentration at several points in the tent'With "the OVA"to insure that the tent contents are at steady state. o Measure the hydrocarbon VOC concentration in the tent with the OVA at three different nitrogen flow rates. Typically the flow rates will be 40, 30 and 20 liters/minute if there is no OVA response at the higher rates (i.e., the mass leak rate from the valve is very low). After each adjustment of the nitrogen flow, check the O- concentration to ensure it stays below 5%. Alternatively, collect samples in Tedlar or aluminized sample bags by drawing sample out of the bag with a portable sampling pump. o Remove the tent and any plugs from the component and collect any condensate on the Inside of the tent in a plastic graduated cylinder. Record the amount collected and the elapsed time the tent was on the component. -- -- - - o If 'there is liquid dripping from the component, collect the drips for a timed period which produces enough collected material for accurate volume measurement. Record the amount in the report, but do not add it to the vapor leak rate. 6-5 VVV 00G005161 XL FIGURE J-2 FUGITIVE VOC EMISSION CONTROL CALCULATION PROCEDURES (a) Screening Concentration screening (vppm) 'idrlftX(*dilutlanr>XOVA>r::-:..cl concentration ~ r.saeur1-- '::is (gg * where: -CA calibration gaa concentration in vppm BE OVA response to calibration gas before screening in vppm AF OVA response to calibration gas after screening: 1a vppm dilution (^g * ^5/2 where: CA calibration gas concentration In vppm OB OVA response to calibration gas using dilution probe before screening in vppm OA - OVA response to calibration gas using dilution probe after screening in vppm OVA - highest Instrument reading at the valve surface minus background reading, In vppm (b) Tented Leak Rate Tent'(pounds/hour) Rate a.836 x 10"5(Q)(HW)(0VA)(RF) T 460 where: Q flow rate Into tent in cubic meters/hour Ng flowjrate In llters/mlnute . /tent oxygen concentration In TT At -r4i.-T._~rr v. [ ni^ -minute \ 0.06 liter-hour * co MU molecular weight of gas in pounds/pound-mole c T-.cr* temperature ln tent in cc^ OVA instrument reading-minus background reading, in vppm enroRF response factor-for leaking gas relative to calibration . 4.836 x 10'5 a conversion factor taking into account the gas constant and assuming a pressure in the tent of 1 atmosphere 6-6 yVV OOQOQ5162.