ASTM D2029 - 97(2008)

    Standard Test Methods for Water Vapor Content of Electrical Insulating Gases by Measurement of Dew Point

    Active Standard ASTM D2029 | Developed by Subcommittee: D27.07

    Book of Standards Volume: 10.03


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    Significance and Use

    Certain gases have excellent dielectric and electric arc interruption characteristics which make their use in electrical installations very desirable.

    Water content, as the test parameter, is of great importance in determining the dielectric effectiveness of the gas. Under certain conditions, water may condense and become a conducting liquid resulting in a catastrophic dielectric breakdown of the insulation. The water content of these insulating gases as expressed by dew point is listed in Specifications D 1933, D 2473, and D 3283.

    Once the dew point is determined, a conversion to moisture content may be performed using Table 1. Once moisture content is known, the lowest temperature at which gas insulated equipment can be safely operated can usually be determined by reviewing manufacturers' specifications for the equipment.

    The dew point of the test gas is independent of the gas temperature but does depend on its pressure. Many moisture measurement test instruments are sensitive to pressure, and display moisture values at the instrument inlet pressure and not necessarily at the pressure of the system being sampled. It is therefore important to account for this condition to avoid serious measurement errors.

    TABLE 1 Relationship Between Dew Point and Moisture Content of Gases

    Note—With a known dew point which is indicated by the dew point indicator or recorder, the moisture content can be read directly from the table. The table shows the amount of water in air or other gas at various dew points at a pressure of 1 atm (14.7) psi.

    Dew PointMoisture ContentDew PointMoisture Content
    °C°Flb/1000
    ft3
    mg/LvolumeA
    percent
    °C °Flb/1000
    ft3
    mg/LvolumeA
    percent
    50 122.05.1682.712.216 3.20.0791.27 0.149
    49 120.24.9278.911.6171.40.0721.16 0.136
    48 118.44.6975.111.018 0.40.0661.06 0.123
    47 116.64.4871.910.519 2.20.0600.965 0.112
    46 114.84.2668.49.9520 4.00.0550.882 0.102
    45113.04.06 65.09.45215.80.0500.8090.093
    44111.23.88 62.18.99227.60.0460.7330.084
    43109.43.69 59.18.52239.40.0420.6660.076
    42107.63.52 56.48.102411.20.0380.6080.069
    41105.83.34 53.57.672513.00.0350.5560.063
    40104.03.18 50.97.272614.80.0310.5060.057
    39102.23.02 48.46.892616.60.0280.4540.057
    38100.42.87 46.06.542818.40.0250.4110.046
    37 98.62.7443.86.2029 20.20.0230.377 0.042
    36 96.82.6041.65.8730 22.00.0210.343 0.038
    35 95.02.4639.45.5531 23.80.0190.307 0.034
    34 93.22.3437.45.2532 25.60.0170.273 0.030
    33 91.42.2235.64.9633 27.40.0150.246 0.027
    32 89.62.1133.84.7034 29.20.0140.229 0.025
    31 87.82.0032.04.4435 31.00.0130.202 0.022
    30 86.01.8930.34.1936 32.80.0120.185 0.020
    29 84.21.8429.24.0137 34.60.0100.167 0.018
    28 82.41.6927.13.738 36.40.00930.149 0.016
    27 80.61.6025.73.5239 38.20.00820.131 0.014
    26 78.81.5224.43.3340 40.00.00740.119 0.0127
    25 77.01.4423.03.1241 41.80.00680.107 0.0113
    24 75.21.3521.72.9442 43.60.00600.096 0.0102
    23 73.41.2820.62.7843 45.40.00540.086 0.0090
    22 71.61.2119.42.6144 47.20.00470.076 0.0080
    21 69.81.1418.32.4645 49.00.00420.068 0.0071
    20 68.01.0817.32.3146 50.80.00380.061 0.0063
    19 66.21.0216.32.1747 52.60.00340.054 0.0056
    18 64.40.96115.42.0448 54.40.00310.049 0.0050
    17 62.60.89914.41.9149 56.20.00270.043 0.0044
    16 60.80.85513.71.8050 58.00.00240.038 0.0039
    15 59.00.79912.81.6851 59.80.00210.034 0.0034
    14 57.20.74912.01.5752 61.60.00190.030 0.0030
    13 55.40.70611.31.4853 63.40.00170.027 0.0027
    12 53.60.66810.71.3954 65.20.00140.023 0.0023
    11 51.80.6209.941.295567.0 0.00130.0210.0021
    10 50.00.5849.371.215668.8 0.00110.0180.0018
    948.20.5478.76 1.135770.60.00100.0160.0016
    846.40.5168.27 1.065872.40.000870.0140.0014
    744.60.4827.73 0.9885974.20.000750.0120.0012
    642.80.4527.25 0.9246076.00.000690.0110.0011
    541.00.4246.79 0.8616177.80.000590.00950.00092
    439.20.3996.36 0.8046279.60.000520.00830.00080
    337.40.3705.94 0.7486381.40.000460.00730.00070
    235.60.3465.55 0.6966483.20.000400.00640.00061
    133.80.3235.18 0.6496585.00.000350.00560.00053
    032.00.3024.84 0.6026686.80.000300.00480.00045
    130.2 0.2804.490.5566788.60.00027 0.00430.00040
    228.4 0.2584.140.5116890.40.00022 0.00360.00034
    326.6 0.2383.810.4706992.20.00019 0.00310.00029
    424.8 0.2203.520.4317094.00.00017 0.00270.00025
    523.0 0.2023.240.3967195.80.00015 0.00240.00022
    621.2 0.1862.980.3647297.60.00013 0.00210.00019
    719.4 0.1712.740.3337399.40.00011 0.00180.00016
    817.60.1582.530.30674101.20.000090.00150.00014
    915.80.1452.320.28075103.00.000080.00130.00012
    1014.00.1342.140.25776104.80.000070.00110.00010
    1112.20.1221.960.23577106.60.000060.00100.00009
    1210.40.1131.810.21578108.40.000050.00080.00007
    138.60.103

    1. Scope

    1.1 These test methods describe the determination of the water vapor content of electrical insulating gases by direct or indirect measurement of the dew point and the calculation of the water vapor content.

    1.2 The following four test methods are provided:

    1.2.1 Method A describes the automatic chilled mirror method for measurement of dew point as low as 73°C (99°F).

    1.2.2 Method B describes the manual chilled mirror or dew cup method for measurement of dew point as low as 73°C (99°F).

    1.2.3 Method C describes the adiabatic expansion method for measurement of dew point as low as 62°C (80°F).

    1.2.4 Method D describes the capacitance method for measurement of dew point as low as 110°C (166°F).

    1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific warnings, see 8.1.1, 9.2, 10.1.2 and 10.2.5.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    D1933 Specification for Nitrogen Gas as an Electrical Insulating Material

    D2472 Specification for Sulfur Hexafluoride

    D3283 Specification for Air as an Electrical Insulating Material


    UNSPSC Code

    UNSPSC Code 12142000(Noble gases)


    DOI: 10.1520/D2029-97R08

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