1、Designation: D1826 94 (Reapproved 2010)Standard Test Method forCalorific (Heating) Value of Gases in Natural Gas Range byContinuous Recording Calorimeter1This standard is issued under the fixed designation D1826; the number immediately following the designation indicates the year oforiginal adoption
2、 or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination with thecontinuous recording calor
3、imeter (Note 1) of the total calorific(heating) value of fuel gas produced or sold in the natural gasrange from 900 to 1200 Btu/standard ft3.NOTE 1An extensive investigation of the accuracy of the Cutler-Hammer recording gas calorimeter, when used with gases of high heatingvalue, was made by the Nat
4、ional Bureau of Standards in 1957 under aresearch project sponsored by the American Gas Association.1.2 The subjects covered in this test method appear in thefollowing sections:SectionsAir-Gas Ratio Test 11Apparatus 5Basis of Measurement 14Cold Balance Test 10Compensation of Complicating Factors 13C
5、ondition of Gas Sample 7Definitions 2Installation of Apparatus 6Maintenance Appendix X1Operating Precautions Appendix X2Operation and Checking of Apparatus 9Precision 15Scope 1Significance and Use 4Standardization of Calorimeter 12Standardization, Preliminary, of Calorimeter by Hydrogen 8Summary of
6、Test Method 31.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.
7、 Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 The most important terms used in connection with thedetermination of the calorific value of gaseous fuels in record-ing calorimetry are as follows:2.1.2 British Thermal Unit, or Btuis the defined Interna-tional Tables British therm
8、al unit (symbol Btu).NOTE 2The defining relationships are:(a) 1 Btulb1= 2.326 Jg1(exact)(b) 1 lb = 453.592 37 g (exact).By these relationships, 1 Btu = 1 055.055 852 62 J (exact). For mostpurposes, the value rounded to 1 Btu = 1 055.056 J is adequate.2.1.3 combustion airair used for combustion, a to
9、tal ofthe portion mixed with the gas as primary air and the airsupplied around the burner tube as secondary air (theoreticalair plus excess air).2.1.4 flue gasesthe products, of combustion remaining inthe gaseous state, together with any excess air.2.1.5 heat-absorbing airthe heat exchange medium us
10、edto absorb the heat of combustion derived from the burning ofgaseous fuel.2.1.6 saturated basisthe expressed total calorific value ofa gas when it is saturated with water vapor at standardtemperature and pressure; 1 ft3of this gas is equivalent in drygas content to 0.9826 ft3of dry gas at the stand
11、ard temperatureof 60F and standard pressure of 14.73 psia.NOTE 3The definitions given in 2.1.6 and 2.1.10 are for total calorific(heating) values per standard cubic foot of gas. The definitions corre-sponding to any other unit quantity of gas are obtained by substituting thename of the desired unit
12、in place of the term “standard cubic foot” in thedefinitions. Methods of calculating calorific (heating) values per cubicfoot of gas under any desired conditions of pressure, temperature, andwater vapor content are specified in Section 14.2.1.7 standard cubic foot of gasthe quantity of any gasthat a
13、t standard temperature and under standard pressure willfill a space of 1 ft3when in equilibrium with liquid water.2.1.8 standard pressureis 14.73 psia.1This test method is under the jurisdiction ofASTM Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.03 on Determina
14、tion ofHeating Value and Relative Density of Gaseous Fuels.Current edition approved May 1, 2010. Published July 2010. Originally approvedin 1961. Last previous edition approved in 2003 as D1826 94 (2003). DOI:10.1520/D1826-94R10.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West
15、 Conshohocken, PA 19428-2959, United States.NOTE 4This is the pressure base adopted by the American NationalStandards Institute in 1969 (Z132.1). According to Daltons law, this isequivalent to stating that the partial pressure of the gas is:14.73 0.256 36 = 14.473 64 psiawhere 0.256 36 is the vapor
16、pressure of water in psia at 60F.2.1.9 standard temperature60F, based on the interna-tional practical temperature scale of 1968.2.1.10 total calorific value (gross heating value, higherheating value)of a gas is the number of British thermal unitsevolved by the complete combustion at constant pressur
17、e ofone standard cubic foot of gas with air, the temperature of thegas, air, and products of combustion being 60F, and all thewater formed by the combustion reaction being condensed tothe liquid state.3. Summary of Test Method3.1 The heating value is determined by imparting all of theheat obtained f
18、rom the combustion of the test gas to a streamof air and measuring the rise in temperature of the air. Thestreams of test gas and heat absorbing air are maintained infixed volumetric proportion to each other by metering devicessimilar to the ordinary wet test meters geared together anddriven from a
19、common electric motor. The meters are mountedin a tank of water, the level of which is maintained and thetemperature of which determines the temperature of the enter-ing gas and air.3.2 The flue gas resulting from combustion of the gas(combustion products plus excess combustion air) is keptseparate
20、from the heat-absorbing air and is cooled to a fewdegrees above the initial temperature of gas and air. The waterformed in the combustion is practically all condensed to theliquid state. Consequently, the temperature rise produced in theheat-absorbing air is directly proportional to the heating valu
21、eof the gas. Since all the heat from the combustion of the testgas sample, including the latent heat of vaporization of thewater vapor formed in the combustion, is imparted to theheat-absorbing air, the calorimeter makes a direct determina-tion of total heating value. The temperature rise is measure
22、d bynickel resistance thermometers and is translated into Btu perstandard cubic foot.4. Significance and Use4.1 This test method provides an accurate and reliablemethod to measure the total calorific value of a fuel gas, on acontinuous basis, which is used for regulatory compliance,custody transfer,
23、 and process control.5. Apparatus5.1 The recording calorimeter (Note 5) consists of twomajor units; the tank unit or calorimeter proper, Fig. 1, Fig. 2,and Fig. 3, in which the heating value of the test gas sample ismeasured; and the recording unit which translates the heatmeasurements into an indic
24、ation of calorific (heating) valueand records it graphically on a strip chart recorder or digitallyif the new SMART-CAL is used (Note 6).NOTE 5The previous specified pressure base was the absolute pres-sure of a column of pure mercury 30 in. in height at 32F and understandard gravity (32.174 ft/s2).
25、 This is equivalent to 14.7346 psia.NOTE 6Refer to specific manufacturers manual for pictures of therecorder or the SMART-CAL, a digital indicating or printing device,currently used on new or retrofitted calorimeters.6. Installation of Apparatus6.1 To secure the precise results that are possible wit
26、h therecording calorimeter, it is important that the instrument beinstalled so that the surrounding conditions will not introduceerrors. In general, more precise results will be secured when anarrow range is maintained on the various conditions of thecalorimeter environment.6.2 Calorimeter RoomA typ
27、ical installation of a singlerecording calorimeter is shown in Fig. 4. The detailed require-ments for the calorimeter room are given in Table 1.NOTE 7A detailed discussion of these requirements is included in thelatest edition of the manufacturers instruction book covering the record-ing calorimeter
28、. The information can be applied to all models of theinstrument.NOTE 8The dimensions shown in Fig. 4 are for the latest modelcalorimeter.6.3 Gas ConnectionLocate the sample line that brings thegas to be tested to the calorimeter tank unit so that the heatingvalue is actually representative of the co
29、nditions existing in themain gas line. Keep the sample line time lag as small aspossible by (1) locating the calorimeter tank unit close to thesample point, (2) running the sample line of small size pipe(Note 9), and (3) operating the sample line at low pressure.Provide an additional purge burner or
30、 a bleed to a low pressurepoint.FIG. 1 CalorimeterSchematic Flow DiagramD1826 94 (2010)2NOTE 9Time lag may be calculated on the basis that the calorimeteruses about 1.2 ft3/h.6.4 Electrical WiringThe four leads for the resistancethermometers between either the recorder or the Smart-Caljunction box a
31、nd the tank unit shall be of No. 12 gage,insulated, solid copper wire without joints. Run in a separaterigid metal conduit which is grounded and contains no otherleads (Note 10). Power circuit wiring should be No. 14 gage,insulated, solid or stranded, copper wire. Provide the supplyline with a suita
32、bly fused disconnect switch. For the modelusing an electronic recorder, it is essential that a suitableground connection be made at both the recorder and the tankunit. Details are given in the manufacturers instructions.NOTE 10Where outdoor or underground wiring must be used, specialcare should be e
33、xercised to protect the terminals of the cables frommoisture to prevent grounds in the measuring circuit.6.5 Initial InstallationWhen the calorimeter is first in-stalled, fill the tank unit with water (Note 11) and adjust it toa temperature that is 2 to 5F below the normal roomtemperature. Allow the
34、 unit to operate at least 24 h beforeperforming the detailed calibration tests.NOTE 11The water may be ordinary tap water supplied by mostmunicipalities. If, however, it is found that excessive quantities of depositsand sludge are formed in short duration which interfere with satisfactoryperformance
35、, it will be necessary to use distilled or demineralized waterwithapHof7.NOTE 12For actual test instructions and other information, see theappropriate instruction book provided by the manufacturer.6.6 Recorder InstallationInstall the recorder so that theinstrument is reasonably free from mechanical
36、vibration. Thisis particularly important for those models in which asuspension-type galvanometer is used.7. Condition of Gas Sample7.1 Physical ContaminationThe gas sample should befree of dust, water, and other entrained solids. If experienceindicates that the foreign materials can enter the sample
37、 line,install a suitable sample line filter. To avoid any problems inthe line from water accumulation, pitch the line to a low pointand provide a drip leg.7.2 Chemical ContaminationThe sample line should bepractically free from hydrogen sulfide. A small, low-capacitypurifier can be constructed using
38、 iron oxide on wood shavingsas the purifying material. The time lag in the purifier adds tothe sample line time lag so that the purifier should be of smallcapacity. A design that will purify about 3 ft3of gas/h will besatisfactory.FIG. 2 CalorimeterLayout DiagramD1826 94 (2010)3FIG. 3 Calorimeter Co
39、mbustion ChamberNOTE 1For each additional calorimeter at least 50 % additional space is required; for example, for two calorimeters the room should be 12 by 18ft inside; for three calorimeters 15 by 18 ft.FIG. 4 Calorimeter RoomD1826 94 (2010)48. Preliminary Standardization of Calorimeter byHydrogen
40、8.1 The use of preliminary standardization by hydrogen testgas before the use of standard methane at the time of the initialinstallation or after any complete major overhaul of the tankunit and recorder is required, because of the following factors:8.1.1 Because of the low density of hydrogen, the p
41、resenceof any leaks in the system from the gas meter to the burner willresult in a definite low reading. This situation should certainlybe considered on the initial installation and whenever the gasmeter assembly has been dismantled for inspection or cleaning.8.1.2 The hydrogen test gives another cr
42、oss-check of theslide wire and thermometer calibration at a different point onthe scale of the instrument. A satisfactory hydrogen test givesadditional assurance that no error exists in this part of theinstrument.8.1.3 There is practically no possibility of incomplete com-bustion on the hydrogen tes
43、t. Therefore, a satisfactory hydro-gen result gives assurance that, with the proper heat input, thecorrect calorific value reading will be secured. If a satisfactoryhydrogen test has been secured and a low reading has beenobtained on the standard gas, the possibility of incompletecombustion could be
44、 suspected. Without the hydrogen test,there might be some tendency to make adjustments to com-pensate in another way for the low reading. This is obviouslyundesirable.NOTE 13Use the manufacturers instruction manual for the hydrogentest. This test is considered satisfactory if the reading agrees with
45、 thetheoretical value within 0.3 %.9. Operation and Checking of Apparatus9.1 The recording calorimeter is designed for continuousoperation and, as a precision instrument, it should receiveregular inspection. Recording the results of tests, the replace-ment of any parts, and the establishment of a re
46、gular inspectionwill ensure that the high degree of precision attainable will bemaintained. The manufacturers appropriate instruction bookgives details of the procedure for operating the instrument. Thefollowing points should be checked periodically:9.1.1 RecorderCheck the operation of the recorder
47、atregular intervals to be sure that the chart is set at the propertime and that the pen is making a satisfactory line. Examina-tions of the chart record will aid in avoiding certain operatingproblems since the record will show if undesirable conditionsdevelop. For example, an irregular chart may be
48、the result ofdeposits in the burner parts or on orifice caps. Gradual changesin the record from normal values may indicate a failure toreplenish the water in the reserve tank or may show theexistence of obstructions on the overflow weir.9.1.1.1 SMART-CALThe paper in the printer should bechecked week
49、ly. It may be necessary to correct the time. Ifalarm lights such as “high,” “low,” “max deviation,” or “flameout” are activated, the operator will check the tank unit forwater level, flame out, dirty overflow weir, restricted combus-tion air flow, defective burner parts, and so forth.9.1.2 Tank UnitTo avoid contamination of the air in theroom with combustible gas, take care to ensure that the bleederburner remains lighted at all times. For unattended locations, athermostatically operated shutoff valve that closes upon failureof
