1、Designation: D 1070 03Standard Test Methods forRelative Density of Gaseous Fuels1This standard is issued under the fixed designation D 1070; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in par
2、entheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover the determination of relativedensity of gaseous fuels, including liquefied petroleum gases,in the gaseous state at normal
3、temperatures and pressures. Thetest methods specified are sufficiently varied in nature so thatone or more may be used for laboratory, control, reference, gasmeasurement, or in fact, for any purpose in which it is desiredto know the relative density of gas or gases as compared to thedensity of dry a
4、ir at the same temperature and pressure.1.2 The procedures appear in the following sections:SectionMethod A, Ac-Me Gravity Balance 7-9Method B, Ranarex Recording and Indicating Gravitometer 10-11Method C, UGC Gravitometer 12-14NOTE 1The test methods and apparatus described herein are repre-sentative
5、 of methods and apparatus used broadly in industry. Manufactur-ers instructions for specific models should be consulted for further detailsand as supplements to the information presented here. In addition toinstrumentation described below additional equally accurate and satisfac-tory instruments may
6、 be available.1.3 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、. Referenced Documents2.1 ASTM Standards:D 5503 Practice for Natural Gas Sample-Handling andConditioning Systems for Pipeline Instrumentation23. Terminology3.1 Definitions:3.1.1 densitymass per unit of volume of the fuel gas or airbeing considered.3.1.2 gaseous fuelmaterial to be tested, as sampled,
8、 with-out change of composition by drying or otherwise.3.1.3 relative densityratio of the density of the gaseousfuel, under the observed conditions of temperature and pres-sure, to the density of dried air, of normal carbon dioxidecontent, at the same temperature and pressure.3.1.3.1 DiscussionIn th
9、ese test methods the term “relativedensity” has replaced the term “specific gravity.” The term,specific gravity, as used in a previous edition of these testmethods, was used incorrectly.3.1.4 relative humidityratio of actual pressure of existingwater vapor to maximum possible pressure of water vapor
10、 inthe atmosphere at the same temperature, expressed as apercentage.4. Summary of Test Methods4.1 Displacement BalancesThis test method is based onthe balancing of the weight of a fixed volume of gas atatmospheric pressure against the weight of dry air across thecenter of gravity of a balance beam.
11、The amount of this“deflection,” subject to correction, for humidity, high CO2content or other factor measures the relative density. Instru-ments of this class may be either visual or chart recording.4.2 Kinetic EnergyThis test method measures the ratio ofthe change in kinetic energy between an impel
12、ler and animpulse wheel operating in gas and a second impeller andimpulse wheel operating in a reference gas (generally air). Therelative torque of the impulse wheels is measured and providesa value for relative density since the relative torque is propor-tional to the gas and air densities.5. Signi
13、ficance and Use5.1 These test methods provide accurate and reliable meth-ods to measure the relative density of gaseous fuels on anintermittent or continuous basis. These measurements arefrequently used for regulatory or contract compliance custodytransfer and process control.1These test methods are
14、 under the jurisdiction of ASTM Committee D03 onGaseous Fuels and is the direct responsibility of Subcommittee D 03.03 onDetermination of Heating Value and Relative Density of Gaseous Fuels.Current edition approved May 10, 2003. Published July 2003. Originallyapproved in 1952. Last previous edition
15、approved in 1998 as D 1070 85 (1998).2Annual Book of ASTM Standards, Vol 05.06.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6. Sampling6.1 The sample shall be representative of the gas to bemeasured and shall be taken from its sou
16、rce without change inform or composition. Sampling of natural gases should be inaccordance with Practice D 5503.METHOD AAcMe GRAVITY BALANCE(Four-Spring Type)7. Apparatus7.1 AcMe Gravity Balance (Four-Spring Type), pressure-tight cylindrical container mounted on a base board. Inside thecontainer is
17、a balance beam with a sealed float at the back andgraduated scale at the front. The beam is suspended at thecenter by thin flat springs. A window for viewing the scale isprovided at the front of the container. The balance beam maybe locked by a cam mechanism when the instrument is not inuse. Valves
18、for introducing gas and air samples are provided.7.2 Carrying Case, for transportation or storage.7.3 Air Dryer, to dehydrate air samples (silica gel).7.4 Tripod, to support the balance firmly.7.5 Pressure-Vacuum Pump, to transfer samples and adjustpressure in the balance.7.6 Mercury Manometer, 760
19、mm, to measure pressure inthe balance.7.7 Aneroid Barometer, temperature compensated to con-vert balance pressure readings to absolute pressures. (Absolutepressure not corrected to sea level.)7.8 Rubber Hose, 6.35 mm (14-in.) inside diameter, fourlengths with brass swivel connections to join the bal
20、ance to itsoperating accessories.7.9 Sampling Hose, 6.35 mm (14 in.) with swivel connec-tions and two male 6.35-mm (14-in.) pipe adapters.7.10 Additional ApparatusRefer to the manufacturersliterature for further information on sizes, assembly, and otherdetails applicable to specific models.8. Proced
21、ure8.1 Assemble and set up the balance in accordance with themanufacturers instructions, making certain that it is firmlysupported, level, and is not disturbed during the entire test.Take and record the following four readings:8.1.1 Average Barometric ReadingRead the aneroid ba-rometer at the beginn
22、ing and end of each test, and record theaverage of these two readings.8.1.2 Air Reading:8.1.2.1 Admit air through first valve and air dryer untilatmospheric pressure is reached. Record temperature in thebalance. Close first valve.8.1.2.2 Open second valve and pull a vacuum of about 650mm, then close
23、 second valve. Unlock the balance beam byturning locking level counterclockwise. The beam will then bein an unbalanced position with the zero above the hairlineindicator.8.1.2.3 Observe the scale from such a position that thereflection of your eye in the look glass is centered on thehairline. Admit
24、air through first valve and air dryer until thebeam begins to fall. Then pinch down the flow of air throughfirst valve so that the air can be cut off at exactly the rightinstant to keep the beam in the balanced position. Observe thescale noting how far the zero swings above and below thehairline. Th
25、e beam is balanced when the zero of the scale isswinging an equal amount above and below the hairline.8.1.2.4 When balance is obtained, lock instrument and readand record the air vacuum shown on the manometer. Recordthe temperature within the balance.8.1.3 Gas Reading:8.1.3.1 Close the valve on the
26、air dryer and close Valve 1.Then open Valve 2 and pull a vacuum of about 650 mm on thebalance.8.1.3.2 Open gas supply valve and admit gas to the balanceuntil the pressure reads about 650 mm. (Do not exceedmanometer maximum reading or the balance may be dam-aged.)8.1.3.3 Repeat 8.1.3.1 and 8.1.3.2 th
27、ree times. The thirdtime will leave only about 0.05 % air in the balance. If thebalance is purged by flowing gas through it, the purging shouldbe continued until two successive readings (8.1.3.4) check.8.1.3.4 Unlock the instrument and release gas pressurethrough Valve 2 until balanced position of b
28、eam is reached.Follow the same method as described for the air reading in8.1.2.4. When balance is obtained, lock the instrument andrecord the gas pressure shown on the manometer. Record thetemperature in the balance.NOTE 2When the gas supply is under a vacuum or has a high contentof hydrocarbons hea
29、vier than ethane, keep the gas pressure within thebalance below that in the source line or container to avoid condensation inthe balance. If necessary, readjust instrument to balance on gas at avacuum about 20 mm higher than that in the sampling source.8.1.4 Air Check Reading:8.1.4.1 Close gas suppl
30、y valves. Open second valve and pulla vacuum of about 650 mm.8.1.4.2 Admit air through the air dryer to the balance untilatmospheric pressure is reached. Close first valve.8.1.4.3 Repeat 8.1.4.1 and 8.1.4.2 at least three times oruntil two successive readings (8.1.4.4) will check.8.1.4.4 Open second
31、 valve and pull a vacuum of about 650nm, then close second valve. Unlock instrument; admit airthrough first valve to bring the beam to the balanced positionas when taking the first air reading.8.1.4.5 When balance is obtained, lock instrument; read andrecord the air vacuum shown on the manometer. Re
32、cord thetemperature in the balance. This reading must check with thefirst air reading if the two temperatures in the balance are thesame. When test is complete close all valves on the balance.Close the cock on the air dryer to prevent moistening of silicagel.9. Calculation9.1 When an aneroid baromet
33、er is used in the field, it shouldbe checked periodically with a mercury barometer. The barom-eter should be handled very carefully and be well packed fortransportation. If barometer reading is in inches and fractions,multiply reading by 25.4 to convert to millimetres. To convertto absolute pressure
34、, add barometric pressure in millimetres toboth air and gas pressure readings. (If air or gas reading is onD1070032vacuum, subtract it from barometric pressure.) Divide theabsolute pressure for air by the absolute pressure for gas toobtain the relative density of the gases shown in the followingexam
35、ple:ManometerReadingBarometerReadingAbsolutePressureBarometer reading:753 mmAir readingGas readingAir check reading127204127+753753=626957Relative density 5absolute air pressureabsolute gas pressure 5 626/957 5 0.654(1)9.2 When there is a difference between the temperature forthe air reading and the
36、 temperature for the gas reading, thesetemperature readings should be converted to absolute tempera-ture, by adding 460, and used in calculations as shown by thefollowing example:ManometerReadingAbsolutePressure,PTemperatureFAbsoluteTemperature,TBarometer reading:745 mmAir reading 95 650 66 526Gas r
37、eading 197 942 68 528Air check reading 90 655 70 530Relative density 5 P air/P gas! 3 T gas/T air! (2)5 650/942! 3 528/526! 5 0.693 first air reading!Relative density 5 655/942! 3 528/530! (3)5 0.693 air check reading!METHOD BRANAREX PORTABLE ANDSTATIONARY GRAVITOMETERS10. Apparatus10.1 Ranarex Grav
38、itometers are typical of kinetic energyinstruments designed for use as either portable or stationaryinstruments to determine and continuously record relativedensity. Fig. 1 shows examples of portable and recordingRanarex gravitometers.10.1.1 Instrumentation based on the same operational prin-ciple c
39、ontain common features to Ranarex models. The chassis,consisting of a main body and two chamber doors. Behindthese doors are two cylindrical gas tight each having inlet andoutlet connections. Each chamber contains an impeller and animpulse wheel, facing each other, in a manner similar to atorque con
40、verter. An electric motor and drive belt rotate theimpellers at the same speed in opposite directions. Heavyaluminum covers enclose and protect the entire mechanism.10.1.2 The impeller in the lower chamber draws in acontinuous flow of the test gas and rotates it at high speedagainst the vanes of the
41、 companion impulse wheel. As therotating gas impinges on the impulse wheel vanes, it undergoesa change in kinetic energy that creates on the lower impulsewheel a torque proportional to the density of the gas. Similarly,the impeller in the upper chamber draws in a continuous flowof outside air and ro
42、tates it at the same speed as the gas but inopposite direction. As the rotating air impinges on the impulsewheel vanes, it too undergoes a change in kinetic energy thatcreates on the upper impulse wheel, a torque proportional tothe density of the air.10.1.3 The impulse wheel torques are transmitted
43、throughpivot shafts to the external lever arms, connecting link, andindicator, which move as a system to an angular position atwhich the torques balance each other. The linkage systemserves as a mechanical computer dividing one torque by theother. At each angular position of the linkage, there is ac
44、orresponding value for the ratio. However, since the torquesare proportional to the density of the medium in each chamber,the ratio may be expressed as follows:density of lower chamber/density of upper chamber (4)10.1.4 When the unknown gas is admitted to the lowerchamber and air is admitted to the
45、upper chamber, the ratiobecomes as follows:density of gas/density of air 5 relative density (5)FIG. 1 Examples of Portable and Recording RanarexGravitometers.FIG. 2 Examples of Portable and Recording RanarexGravitometers.D107003310.1.5 The relation between the value of this fraction andangular posit
46、ion of the linkage and indicator is determined inthe design of the instrument. The indicating scale and record-ing chart are graduated to read directly in relative density.10.1.6 Refer to the manufacturers literature for furtherinformation on sizes, assembly, and other options applicable tospecific
47、models.11. Procedure11.1 Ranarex gravitometers are direct-reading devices, andwhen operated in accordance with the instructions will delivervalues consistent with ASTM definition for relative density(see 3.1.3). Compensation for factors, which if neglectedwould cause deviation from the basic definit
48、ion, is provided asfollows:11.1.1 Dried Air StandardInstall a drier at the air inlet.The instrument must use air at normal CO2content as thereference standard.11.1.2 TemperatureThe air and the gas should be at thesame temperature. The installation of a sample line of reason-able length relative to d
49、iameter, for example, the equivalent of3 to 5 m (10 to 15 ft) of 9.5-mm (38-in.) tube or pipe, will allowsufficiently rapid heat transfer for the gas sample to reachambient temperature before it is drawn into the referencechamber.11.1.3 PressureReduce the gas sample to atmosphericwithin 6- to 13-mm (14-to12-in.) water column at the inlet tothe apparatus. The reference air is also at atmospheric pressure.Therefore, measure both the gas and air at atmosphericpressure. Normal operating results have indicated that if thegas flow is between 0.28 to
