1、Designation: D 1826 94 (Reapproved 2003)Standard Test Method forCalorific (Heating) Value of Gases in Natural Gas Range byContinuous Recording Calorimeter1This standard is issued under the fixed designation D 1826; the number immediately following the designation indicates the year oforiginal adopti
2、on or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination with thecontinuous recording ca
3、lorimeter (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
4、National 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
5、13Condition 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
6、of 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
7、.2. 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 th
8、ermal 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
9、 total 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
10、 usedto 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 st
11、andard 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 un
12、it 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 gastha
13、t at 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.NOTE 4This is the pressure base adopted by the American NationalStandards Institute in 1969 (Z132.1). According to Daltons law, this isequivalent
14、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 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, higherheati
15、ng value)of a gas is the number of British thermal unitsevolved by the complete combustion at constant pressure of1This test method is under the jurisdiction of ASTM Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.03 on Determination ofHeating Value and Relative De
16、nsity of Gaseous Fuels.Current edition approved May 10, 2003. Published May 2003. Originallyapproved in 1961. Last previous edition approved in 1998 as D 1826 94 (1998).1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.one standard cub
17、ic 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 from the combustion o
18、f 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 common electric moto
19、r. 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 from the heat-absorb
20、ing 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 valueof the gas. Since a
21、ll 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 measured bynickel resistanc
22、e 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, and process control
23、.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 indication of calorific (
24、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). This is equivalent
25、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 with therecording calor
26、imeter, 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 typical installation of
27、 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. The information ca
28、n 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 conditions existing in
29、 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 a bleed to a low pr
30、essurepoint.NOTE 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 and the tank unit shall be of No. 12 gage,insulated, solid copper wire withou
31、t joints. Run in a separaterigid metal conduit which is grounded and contains no otherFIG. 1 CalorimeterSchematic Flow DiagramD 1826 94 (2003)2leads (Note 10). Power circuit wiring should be No. 14 gage,insulated, solid or stranded, copper wire. Provide the supplyline with a suitably fused disconnec
32、t 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 exercised to protect
33、 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 unit to operate at
34、 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, it will be necess
35、ary 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 vibration. Thisis p
36、articularly 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 line,install a sui
37、table 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 iron oxide on wood
38、 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.8. Preliminary Standardization of Calorimeter byHydrogen8.1 The use of preliminary stand
39、ardization 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:FIG. 2 CalorimeterLayout DiagramD 1826 94 (2003)38.1.1 Because of the low density o
40、f hydrogen, the presenceof 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
41、 gives another cross-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
42、 the hydrogen test. 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 incompleteco
43、mbustion could be 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 re
44、ading agrees with 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 esta
45、blishment of a regular 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
46、 of the recorder 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 irregu
47、lar chart may be 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 shou
48、ld bechecked weekly. It may be necessary to correct the time. Ifalarm lights such as “high,” “low,” “max deviation,” or “flameFIG. 3 Calorimeter Combustion ChamberD 1826 94 (2003)4out” are activated, the operator will check the tank unit forwater level, flame out, dirty overflow weir, restricted com
49、bus-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 the bleeder flame is normally provided. Regular inspectionwill indicate the necessity of replenishing the water in thereserve tank and thus ensure maintenance of the proper level inthe main tank. The presence of any foreign materia
