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1、h- 2 5 0 5 3773-84 4853903 O027800 3 International Standard 3993 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION*MEYHAPOIIHAR OPrAHM3AUMR no CTAHAAPTM3AUWM*ORGANISATION INTERNATIONALE DE NORMALISATION Liquefied petroleum gas and light hydrocarbons - Determination of density or relative density - Pres
2、sure hydrometer method Gaz de ptrole liqufis et hydrocarbures lgers - Dtermination de la masse volumique ou de la densit relative - Mthode de laromtre sous pression First edition - 1984-08-01 UDC 665.725 : 531.754.3 Ref. No. IS0 3993-1984 (E) c 2 05 hydrometers, test equipment. Descriptors : petrole
3、um products, liquefied petroleum gases, hydrocarbons, tests, physical tests, determination, density (masc/volume), c 8 O v, Price based on 6 pages COPYRIGHT International Organization for Standardization Licensed by Information Handling Services COPYRIGHT International Organization for Standardizati
4、on Licensed by Information Handling Services Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of developing International Standards is carried out through IS0 technical committees. Every member body
5、 interested in a subject for which a technical committee has been authorized has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. Draft International Standards adopted by the technical comm
6、ittees are circulated to the member bodies for approval before their acceptance as International Standards by the IS0 Council. International Standard IS0 3993 was developed by Technical Committee ISO/TC 28, Petroleum products and lubricants, and was circulated to the member bodies in March 1983. It
7、has been approved by the member bodies of the following countries : Austria Australia Belgium Brazil Canada China Egypt, Arab Rep. of Germany, F. R. .Hungary India Iran Iraq Israel Italy Japan Netherlands Norway Peru Romania South Africa, Rep. of Sri Lanka Sweden Switzerland Turkey United Kingdom US
8、A USSR Venezuela The member body of the following country expressed disapproval of the document on technical grounds : France International Organization for Standardization, 1984 O Printed in Switzerland COPYRIGHT International Organization for Standardization Licensed by Information Handling Servic
9、es COPYRIGHT International Organization for Standardization Licensed by Information Handling Services 3773-84 4853703 oo2q802 7r INTERNATIONAL STANDARD IS0 3993-1984 (E) Liquefied petroleum gas and light hydrocarbons - Determination of density or relative density - Pressure hydrometer method 1 Scope
10、 and field of application 1.1 This International Standard specifies a method for the determination of density or relative density of liquefied petroleum gases and other light hydrocarbons. The prescribed apparatus shall not be used for materials having gauge vapour pressures higher than 1,4 MPa1) (1
11、4 bar) (absolute vapour pressure 1,5 MPa) at the test temperature. CAUTION - Attention is drawn to the hazards en- countered when working with liquefied petroleum gas or light hydrocarbons. The requirements of any national, local or domestic safety code should always be strictly observed. 1.2 Altern
12、ative calibration procedures are described, but only the one using a certified hydrometer is suitable for the deter- mination of density to be used in calculations of quantities for custody transfer or fiscal purposes. NOTE - An alternative method for calculating the density of liquefied petroleum g
13、ases from gas chromatographic analysis is described in IS0 65782). 1.3 Provision is made in the annex for the use of ther- mohydrometers. 2 Definitions For the purpose of this International Standard, the following definitions shall apply. 2.2 density : The mass of the liquid divided by its volume. W
14、hen reporting the density, the unit of density used, together with the temperature, shall be explicitly stated, for example kilogram per metre cubed or gram per millilitre at t OC (see the note), The standard reference temperature for international trade in petroleum and its products is 15 OC (see I
15、S0 5024); but other reference temperatures may be required for legal metrology or other special purposes. NOTE - In this International Standard, the preferred unit is the kilogram per metre cubed, but provision is also made for the useof the gram per millilitre. 2.2 relative density (this term now r
16、eplaces the former term specific gravity) : The ratio of the mass of a volume of the liquid at a temperature tl to the mass of an equal volume of pure water at a temperature t2, .e. the ratio of the density of the li- quid at a temperature tl to the density of pure water at a temperature t2. When re
17、porting the relative density, the temperatures tl and t2 shall be explicitly stated, for example relative density 60/60 OF. The standard reference temperature is 15 OC, but 20 OC and 60 O F are also in general use for tl and t2 and other tempera- tures may be employed for tl. 3 Principle The apparat
18、us is purged with a portion of the sample before fill- ing with the portion to be used for testing. The pressure cylinder is filled to a level at which the enclosed hydrometer floats freely. The hydrometer reading and the temperature of the sample are noted. 1) The SI unit of pressure is the pascal
19、: 1 Pa = 1 N/d; 105 Pa = 1 bar = 1,019 72 kgf/cm2 2) At present at the stage of draft. 1 COPYRIGHT International Organization for Standardization Licensed by Information Handling Services COPYRIGHT International Organization for Standardization Licensed by Information Handling Services IS0 3993-1984
20、 (E) 4 Apparatus 4.1 Hydrometers, made of glass, graduated in density or relative density, with the appropriate range and conforming to the dimensions given in table 1. I Use a certified hydrometer, or calibrate the hydrometers in ac- cordance with clause 7. Calibration corrections should be ap- pli
21、ed if the scale errors are in excess of 0,5 of a subdivision of the scale. I NOTE - For the use of thermohydrometers see the annex. Bulb wall thickness Stem diameter Stem wall thickness Scale length 0.4 to 0,6 mm 8to9mm 0.3 to 0.35 mm 110 to 130 mm 4.2 Thermometer, having a sensitivity of at least 2
22、,7 mm/l O C 1,5 mm/l O F ) calibrated for total immersion and of suitable dimensions to fit inside the hydrometer cylinder (4.3). A thermometer conforming to ISO/R 653, STl0.21 - 151 +45 is recommended. The thermometer shall be held firmly inside the hydrometer cylinder by means of a suitable clip i
23、n such a position as not to interfere with the free motion of the hydrometer. 4.3 Hydrometer cylinder, constructed of glass or trans- parent plastics, for example polymethylmethacrylate or equiv- alent material, conforming to the design and dimensions given in the figure. The ends shall be tightly s
24、ealed by means of chloroprene gaskets and metal end-plates as shown. CAUTION - As a precautionary measure a protective shield shall be placed around the plastics or glass cylinder. Replace any cylinders that show any fogging, crazing, cracking, or etching. NOTE - Certain compounds attack plastics an
25、d cloud the inner sur- face of the cylinder, making it difficult or impossible to read the hydrometer. Tests have shown no attack by ethane, ethylene, pro- pane, propylene, butane, isobutane, normal butylenes, isobutylene, pentane and isopentane and no attack is expected from butadiene. Users are ca
26、utioned, however, always to clean the cylinder thoroughly after each determination. Ketones and alcohols must not be used for cleaning as they attack and weaken plastics whilst aromatics also tend to attack the surface of plastics and should similarly not be used. The liquid inlet valve and the liqu
27、id outlet valve shall be tightly connected to a base plate which shall be so bored as to give both valves a common inlet to the cylinder. The vapour vent valve shall be similarly connected to the top plate. All valves shall be 6 mm or equivalent needle valves. The cylinder shall not be operated at a
28、 gauge pressure greater than 1,4 MPa (14 bar). 4.4 Water bath, fitted with a thermostat or other means of maintaining the bath at a constant temperature of 15 +_ 0,2 OC or 20 f 0,2 OC or 60 f 0,5 O F , and of such dimensions that the hydrometer cylinder (4.3) can be completely immersed. 5 Reference
29、liquids The following reference liquids are required for calibration of the hydrometer if a certified hydrometer is not available. 5.1 Pure propane, having a certified density or relative density. NOTE - Propane of density 507,6 k g / d (0.507 6 g/ml) at 15 O C or 500.0 kg/m3 (0.500 O g/ml) at 20 O
30、C or a relative density 60/60 O F of 0,507 3 is suitable. 5.2 Pure butane, having a certified density or relative density. NOTE - Butane of density 584.5 kg/rn3 (0,584 5 g/ml) at 15 O c or 578,8 kg/m3 (0,578 8 g/ml) at 20 O C or a relative density 60/60 O F of 0,584 4 is suitable. Table 1 - Ranges a
31、nd dimensional specification for pressure hydrometers Alternative ranges Subdivisions Figured every Overall length Bulb diameter 0,001 g/ml 0,001 330 mm max. 18 to 20 mm COPYRIGHT International Organization for Standardization Licensed by Information Handling Services COPYRIGHT International Organiz
32、ation for Standardization Licensed by Information Handling Services 3773-54 4553703 0027504 or IS0 3993-1984 (E) Hydrometer- Thermometer- Liquid inlet needle valve 6 nominal - bore (or equivalent) Vapour vent needle valve 6 nominal bore (or equivalent) c 6 2 4 Dimensions in millimetres I A I - 6 rod
33、s, 0 6 Plastics or glass -tube, 0 ext. 51 x 6,5 wall -Rubber seal (with holes, as in A) Liquid outlet needle bore (or equivalent) -valve 6 nominal Figure - Pressure hydrometer cylinder 3 COPYRIGHT International Organization for Standardization Licensed by Information Handling Services COPYRIGHT Inte
34、rnational Organization for Standardization Licensed by Information Handling Services IS0 3993-1984 (E) 6 Sampling The procedure for sampling for calibration of the apparatus and for subsequent testing is described below. 6.1 Carefully clean and dry the hydrometer (4.1), the ther- mometer (4.2) and t
35、he inside wall of the pressure cylinder (4.3). Insert the hydrometer in the pressure cylinder and attach the thermometer and cover plate. 6.2 Connect the source of supply of the liquid to be tested to the inlet valve by suitable fittings so that a representative sample can be introduced into the cyl
36、inder (4.3); ascertain that these connections are free from leaks. Open the outlet valve and purge the sampling connections by opening the inlet valve slightly, permitting the product to flow through the outlet valve at the bottom of the cylinder. 6.3 When the connections have been purged, close the
37、 outlet and vent valves and open the inlet valve, permitting the liquid to enter the cylinder until it is full. If necessary, the vent valve may be opened slightly to permit complete filling of the cylinder, after which it shall be closed. At no time shall the pressure in the cylinder be allowed to
38、rise above a gauge pressure of 1,4 MPa (14 bar). 6.4 When the cylinder has been filled, close the inlet valve and open the outlet valve, permitting the contents of the cylinder to be withdrawn completely and the pressure inside the cylinder to be reduced to that of the atmosphere. 6.5 Close the outl
39、et valve and open the inlet valve, filling the cylinder to a level at which the enclosed hydrometer floats freely. If it is necessary to accomplish this filling by venting vapour through the vent valve, repeat the purging to cool the cylinder sufficiently to permit its being filled without the neces
40、sity of venting. 6.6 With all valves closed, examine the apparatus for leaks; if leaks are detected, discard the sample, reduce the pressure to atmospheric and repair the leaks. Repeat the sampling pro- cedure. 7 Calibration of apparatus 7.1 If a hydrometer having a calibration certificate issued by
41、 an approved laboratory is not used, the hydrometer shall be calibrated using one of the alternative procedures specified in 7.2 or 7.3 before densities are determined. 7.2 Take three or more samples having different densities in the range of the hydrometer to be tested. Using the procedure specifie
42、d in clause 8 determine in duplicate for each sample the hydrometer reading on a certified hydrometer. Average the two values for each sample if these do not differ by more than 0,5 kg/m2, or the equivalent. If the duplicate results differ by more than 0,5 kglm2, or the equivalent, repeat the determ
43、ina- tions. Then obtain the average of duplicate hydrometer readings on the hydrometer being calibrated following the same procedure. Ensure that the maximum difference in temperature for all these determinations is not more than 0,4 O C (1 O F ) . Compare the hydrometer readings obtained on the two
44、 hydrometers and record any differences as corrections to be applied to hydrometer readings on the hydrometer being calibrated. 7.3 Use the procedure in clause 8 to determine the density of one of the reference liquids of certified density (see clause 5) at a temperature within f 0,2 O C (0,5 O F )
45、of the certification temperature. Make duplicate determinations and average the two results if these do not differ by more than 0,5 kg/m3, or the equivalent. Deduct the average from the certified density of the reference liquid to obtain the correction to be applied. If the two results differ by mor
46、e than 0,5 kg/m3, or the equivalent, repeat the determinations. NOTE - This method provides a check of the hydrometer at only one point on the scale, but this is often acceptable for routine testing. 8 Procedure 8.1 be tested as specified in clause 6. Prepare the apparatus and take a sample of the l
47、iquid to 8.2 Disconnect the cylinder from the source of supply of liquid and place it in the water bath (4.4) maintained at 15 f 0,2 OC, 20 f 0,2 O C or 60 f 0.5 O F until thermal equilibrium has been obtained. To accelerate thermal adjust- ment, occasionally remove the cylinder from the water bath,
48、 swirl it gently a few times to ensure mixing, and replace it in the water bath. Exercise care to prevent damage to the hydrometer and thermometer. Measure the temperature of the water bath using a ther- mometer outside the cylinder in order to avoid the effects of pressure on the thermometer inside
49、 the cylinder. Use the ther- mometer inside the cylinder to ensure that the liquid under test has reached constant temperature and that the temperature of the liquid does not vary significantly during the determination. 8.3 Remove the cylinder from the water bath (see the note), stand it on a firm level surface and, while the hydrometer is floating freely, take the hydrometer reading as promptly as possible in the following manner : Observe a point slightly below the plane of the liquid surface and then raise the line of vision until this surface, seen as an ellipse, be
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