Proposed Rule: Mandatory Reporting of Greenhouse Gas EmissionsMeeting DocumentationDateStaff ContactInformation (Name,email, phone #)Name ofOrganization(Attach list of allattendees names andemails if possible)Summary of Discussion (e.g., applicability, reportingrequirements, etc.)WrittenCommentsProvided?Did they alsosubmit to Docket?Date sent toEPA- CCDEmail &telephonecorrespondencefrom7/2/10 –7/10/10Mollie Averyt, ICFInternational, 202-862-1569maveryt@icfi.comPaul Stewart, ICFInternational 202-862-1135pstewart@icfi.comDeborah Harris, ICFInternational 202-862-1574dharris@icfi.comon behalf of EPAunder Contract EPW-07-068, TaskOrder 68Representativesfrom PartnerCompanies ofEPA’s SF6Emission ReductionPartnership forElectric PowerSystems, including:Oncor, AEP, BPAIndustry contactsincluding: Dilo, AirProducts, Airgas,and NISTTopic: Error in cylinder weight measurementsQuestions were researched regarding:-whether the error of scales is typically expressed inabsolute terms;-if scale manufacturers distinguish between accuraciesand precisions;-precision and accuracy ofthe best-performing scalesnow owned by electric power systems; and-procedures at gas suppliers for filling cylinders andverifying that theycontain the correct amount of gasIn addition to telephone correspondence and e-mail, webresearch also conducted. Research notes provided below.NoN/A1Scale Error Research Notes -7/2/10 – 7/10/101.Is error of scales typically expressed in absolute terms (e.g., percent of full-scale or 2 lbs) or in relative terms (percent of reading atany level)? If precisions and accuracies are expressed in terms of full scale, what is full scale?Web research:Scale Manufacturers:1.Dilo (http://dilo.com/accessories.html) – absolute (+/- 0.1 lbs)2.Scaletron Industries (http://www.scaletronscales.com/) – absolute3.Intercomp (see attached spec sheet) - relative4.Brooks Instruments(http://www.brooksinstrument.com/downloads/Product%20Documentation/Cylinder%20Scales/Data%20Sheets/gcs400.pdf) – absolute(+/- 0.1% of full scale)5.Avery Weigh-Tronix (http://www.wtxweb.com/literature/drum_L.pdf) –understanding is that this isabsolute (5000 divisions +/- division)16.Tramfloc (http://www.tramfloc.com/tf57.html) – relative (some are 1% some are 0.5 % of capacity)It is clear that both relative and absolute terms are used. However, +/- a certain percentage of capacity (i.e., absolute) seems more common,through research of various web sites of industrial scalemanufacturers (that may not necessarily be targeted for SF6, although certainly capable ofweighing liquefied gases such as ammonium). A +/- a certain percentage of capacity translates into an absolute term; capacities are typicallybetween 300 and 350 lbs (e.g., 0.1% * 349lbs = .349lbs in absolute terms). Accuracy expressed in this way may be the reason why Oncor (andothers in the electronic industry) submitted the commentto have the accuracy expressedin absolute terms.NIST Handbook 44:It is not clear whether the NIST handbook does addresses thisquestion; it certainly does not address it directly. Weighingdevices are divided into accuracy classes (I, II, III, III L, orIIII) according to the number of scale divisions (n) and the value of the scale division(d). Table 3 provides n and d for each class. Table 7a explainseach class in terms of weighing application or scale type. Class III appears to bethe scale type for these industries.1“Divisions” refers to the amount of increments a scale offers. The amount of divisions can be determined by taking the scale's capacity divided by the scalesreadability (the smallest number a scale can display).http://www.balances.com/applications/glossary.html2Additional information from Steve, Cook, NIST (7/7/10):-Tolerance is defined by NIST Handbook 44 as “A value fixing the limit of allowable error or departure from true performance orvalue.”-“Maintenance tolerance” applies to equipment in actual use; whereas the “acceptance tolerance” applies to equipment to be put intocommercial use for the first time (along with some other conditions, for example, equipment returned to commercial service followingofficial rejection for failure to conform to performance requirements ,which is officially tested w/in 30 days after correctiveservice).-The term “count” is synonymous with the terms “division” and “graduation”.-Scales are tested against a reference and that reference is a physical standard. This physical standard, or “value” as referred to in thedefinition of tolerance, is a block of metal that is a certainweight as verified by weight and measures divisions at state (or local)governments.-An example –a scale that has a capacity of 1,000 lbs is graduated by1lb. Therefore, if something is weighed that is 500 lbs,it has 500graduations. You would thengo to Table 6 of handbook 44(“Maintenance Tolerances”)(http://ts.nist.gov/WeightsAndMeasures/Publications/upload/2-20-09-HB44-FINAL.doc) and look up the allowable error, which in thiscase is 1 graduation.2.Do scale manufacturers distinguish between accuracies and precisions?Repeated measurements on a scale with 1% precision willdecrease (improve) the precision of the summed or averaged measurements, but will not affect the accuracies of the summed oraveraged measurements.Brooks Instrumentsdoes provide precision expressed in absolute terms (+/- 0.1% offull scale). In a brief search, precisions were not found inspecification sheets from other manufacturers.BPA and Oncor (phone calls):out of all of the scales they researched, they did not see any information on precision, only accuracy.AEP (phone call):not sure.Reply from Dilo (information from Cooper Instruments):“There is the overall accuracy of a load cell. This is determined by Non-Linearity,Hysteresis, and Non-Repeatability. This is based on the full scale ofthe load cell I.E: 1000 lbs. So if you want to know whatthe precision is youcan multiply an accuracy of 1% by a full scale of1000 lbs. So you can say your precision is 1 lbs.”343.What is the precision and accuracy of the best-performing scales now owned by electric power systems?BPA (phone call):They use Dilo scales, which, from the research, appears to be best performing.Oncor (phone call):They use the basic scales available at retail stores such as Walmart.AEP (phone call):they have a scale in each of their store rooms but was not certain of accuracy. Believed that they were low end scales. Withthereporting rule in mind, they are planning to have each region buynew scales. They have at least 5 store rooms – each store room is where theykeep their gas for each of regions. There may be some scales at some substations that are 3 hours away or more. They do not move their scalesaround on trucks.4.What is procedure at gas suppliers for filling cylinders and verifying that they contain the correctamount of gas? Are cylindersplaced on a scale and filled until they reach the target weightof nominal tare + correct fill(119 lbs + 115 lbs)? Or are cylinders’tare weights measured at the supplier prior to cylinder filling?Response from Gas Suppliers:Airgas (phone call):The former, i.e., the target weight of nominal tare + correctfill. They refer to a tare weight stamped on the side of thecylinder. They will know how much each cylinder can hold. They rarely fill them empty.Air Products:sent email (and followed up with a call): “I can only speak for what we do at APCI. Our competitors may do something totallydifferent.For cylinders:We get the tare weight of each cylinder prior to fill. We fillthese in batches of 10 on the samemanifold. We use scales for 4 out of the 10. (Scale1 for cylinder 1, scale 2 on cylinder 2 for cylinders 2&3, Scale 3 on cylinder 4 for cylinders 4-6, scale 4 on cylinder 7 for cylinders 7-10.) As anexample we would fill cylinder 7 to target and then stop the fill on 7-10. After the fill on all 10 is complete, we weigh each cylinder individuallyto get the product weight.For Y Containers: Each Y has its own scale andis tared and then filled to a target weight.For ISO containers: Iso containers are filled to target weights using Temperature and Pressure readings. After they are filled they are weighed onthe truck scale. The are tared prior to fill.We use Metler-Toledo scales for cylinder and Yfills. Toledo truck scales for ISO fills.”