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Historical Reaffirmation

ASTM D2029-97(2008)

Standard Test Methods for Water Vapor Content of Electrical Insulating Gases by Measurement of Dew Point
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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 βˆ’ 73Β°C (βˆ’99Β°F).

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

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

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

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

Noteβ€”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
Β°CΒ°Flb/1000
ft3
mg/LvolumeA
percent
Β°C Β°Flb/1000
ft3
mg/LvolumeA
percent
50 122.05.1682.712.2βˆ’16 3.20.0791.27 0.149
49 120.24.9278.911.6βˆ’171.40.0721.16 0.136
48 118.44.6975.111.0βˆ’18 βˆ’0.40.0661.06 0.123
47 116.64.4871.910.5βˆ’19 βˆ’2.20.0600.965 0.112
46 114.84.2668.49.95βˆ’20 βˆ’4.00.0550.882 0.102
45113.04.06 65.09.45βˆ’21βˆ’5.80.0500.8090.093
44111.23.88 62.18.99βˆ’22βˆ’7.60.0460.7330.084
43109.43.69 59.18.52βˆ’23βˆ’9.40.0420.6660.076
42107.63.52 56.48.10–24βˆ’11.20.0380.6080.069
41105.83.34 53.57.67βˆ’25βˆ’13.00.0350.5560.063
40104.03.18 50.97.27βˆ’26βˆ’14.80.0310.5060.057
39102.23.02 48.46.89βˆ’26βˆ’16.60.0280.4540.057
38100.42.87 46.06.54βˆ’28βˆ’18.40.0250.4110.046
37 98.62.7443.86.20βˆ’29 βˆ’20.20.0230.377 0.042
36 96.82.6041.65.87βˆ’30 βˆ’22.00.0210.343 0.038
35 95.02.4639.45.55βˆ’31 βˆ’23.80.0190.307 0.034
34 93.22.3437.45.25βˆ’32 βˆ’25.60.0170.273 0.030
33 91.42.2235.64.96βˆ’33 βˆ’27.40.0150.246 0.027
32 89.62.1133.84.70βˆ’34 βˆ’29.20.0140.229 0.025
31 87.82.0032.04.44βˆ’35 βˆ’31.00.0130.202 0.022
30 86.01.8930.34.19βˆ’36 βˆ’32.80.0120.185 0.020
29 84.21.8429.24.01βˆ’37 βˆ’34.60.0100.167 0.018
28 82.41.6927.13.7βˆ’38 βˆ’36.40.00930.149 0.016
27 80.61.6025.73.52βˆ’39 βˆ’38.20.00820.131 0.014
26 78.81.5224.43.33βˆ’40 βˆ’40.00.00740.119 0.0127
25 77.01.4423.03.12βˆ’41 βˆ’41.80.00680.107 0.0113
24 75.21.3521.72.94βˆ’42 βˆ’43.60.00600.096 0.0102
23 73.41.2820.62.78βˆ’43 βˆ’45.40.00540.086 0.0090
22 71.61.2119.42.61βˆ’44 βˆ’47.20.00470.076 0.0080
21 69.81.1418.32.46βˆ’45 βˆ’49.00.00420.068 0.0071
20 68.01.0817.32.31βˆ’46 βˆ’50.80.00380.061 0.0063
19 66.21.0216.32.17βˆ’47 βˆ’52.60.00340.054 0.0056
18 64.40.96115.42.04βˆ’48 βˆ’54.40.00310.049 0.0050
17 62.60.89914.41.91βˆ’49 βˆ’56.20.00270.043 0.0044
16 60.80.85513.71.80βˆ’50 βˆ’58.00.00240.038 0.0039
15 59.00.79912.81.68βˆ’51 βˆ’59.80.00210.034 0.0034
14 57.20.74912.01.57βˆ’52 βˆ’61.60.00190.030 0.0030
13 55.40.70611.31.48βˆ’53 βˆ’63.40.00170.027 0.0027
12 53.60.66810.71.39βˆ’54 βˆ’65.20.00140.023 0.0023
11 51.80.6209.941.29βˆ’55βˆ’67.0 0.00130.0210.0021
10 50.00.5849.371.21βˆ’56βˆ’68.8 0.00110.0180.0018
948.20.5478.76 1.13βˆ’57βˆ’70.60.00100.0160.0016
846.40.5168.27 1.06βˆ’58βˆ’72.40.000870.0140.0014
744.60.4827.73 0.988βˆ’59βˆ’74.20.000750.0120.0012
642.80.4527.25 0.924βˆ’60βˆ’76.00.000690.0110.0011
541.00.4246.79 0.861βˆ’61βˆ’77.80.000590.00950.00092
439.20.3996.36 0.804βˆ’62βˆ’79.60.000520.00830.00080
337.40.3705.94 0.748βˆ’63βˆ’81.40.000460.00730.00070
235.60.3465.55 0.696βˆ’64βˆ’83.20.000400.00640.00061
133.80.3235.18 0.649βˆ’65βˆ’85.00.000350.00560.00053
032.00.3024.84 0.602βˆ’66βˆ’86.80.000300.00480.00045
βˆ’130.2 0.2804.490.556βˆ’67βˆ’88.60.00027 0.00430.00040
βˆ’228.4 0.2584.140.511βˆ’68βˆ’90.40.00022 0.00360.00034
βˆ’326.6 0.2383.810.470βˆ’69βˆ’92.20.00019 0.00310.00029
βˆ’424.8 0.2203.520.431βˆ’70βˆ’94.00.00017 0.00270.00025
βˆ’523.0 0.2023.240.396βˆ’71βˆ’95.80.00015 0.00240.00022
βˆ’621.2 0.1862.980.364βˆ’72βˆ’97.60.00013 0.00210.00019
βˆ’719.4 0.1712.740.333βˆ’73βˆ’99.40.00011 0.00180.00016
βˆ’817.60.1582.530.306βˆ’74βˆ’101.20.000090.00150.00014
βˆ’915.80.1452.320.280βˆ’75βˆ’103.00.000080.00130.00012
βˆ’1014.00.1342.140.257βˆ’76βˆ’104.80.000070.00110.00010
βˆ’1112.20.1221.960.235βˆ’77βˆ’106.60.000060.00100.00009
βˆ’1210.40.1131.810.215βˆ’78βˆ’108.40.000050.00080.00007
βˆ’138.60.1031.650.196βˆ’79βˆ’110.20.000040.00070.00006
βˆ’146.80.0951.520.179βˆ’80βˆ’112.00.000040.00060.00005
βˆ’155.00.0861.380.163βˆ’81βˆ’113.80.000030.00050.00004

A Vapor pressures in atmospheres at various dew points can be obtained by dividing the values for β€œvolume percent'' in this table by 100. Calculations for this table were made by using the International Critical Table values for the vapor pressure of ice and liquid water. The vapor pressure of liquid water was used for values from 50 to 0Β°C. The vapor pressure of ice was used from 0 to βˆ’ 81Β°C.

SDO ASTM: ASTM International
Document Number D2029
Publication Date Dec. 1, 2008
Language en - English
Page Count 6
Revision Level 97(2008)
Supercedes
Committee D27.07
Publish Date Document Id Type View
April 10, 1997 D2029-97 Revision
Jan. 1, 2017 D2029-97R17 Reaffirmation
Dec. 1, 2008 D2029-97R08 Reaffirmation
April 10, 1997 D2029-97R03 Reaffirmation