Standard Test Method for Sediments and Soluble Sludge in Service-Aged Insulating Oils

SCOPE
1.1 This test method covers the determination of sediment and soluble sludge in service-aged insulating oils of petroleum origin. Also, provision is made for determining organic and inorganic content of the sediment. The method is intended primarily for oils of comparatively low viscosity; for example 5.7 to 13.0 cSt at 40°C (104°F). Suitability for high viscosity oils have not been determined.  
1.2 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.

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Publication Date
09-Oct-1997
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ASTM D1698-97 - Standard Test Method for Sediments and Soluble Sludge in Service-Aged Insulating Oils
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 1698 – 97
Standard Test Method for
Sediments and Soluble Sludge in Service-Aged Insulating
Oils
This standard is issued under the fixed designation D 1698; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Summary of Test Method
1.1 This test method covers the determination of sediment 4.1 A sample portion is centrifuged to separate sediment
and soluble sludge in service-aged insulating oils of petroleum from the oil. The upper, sediment-free portion is decanted and
origin. Also, provision is made for determining organic and retained for determination of soluble sludge. The sediment is
inorganic content of the sediment. The method is intended dislodged and filtered through a filtering crucible. After drying
primarily for oils of comparatively low viscosity; for example and weighing to obtain total sediment the crucible is ignited at
5.7 to 13.0 cSt (mm /s) at 40°C (104°F). Suitability for high 500°C and reweighed. Loss in weight is organic and the
viscosity oils have not been determined. remainder is inorganic content of sediment. Soluble sludge is
1.2 This standard does not purport to address all of the determined on the sediment-free portion by dilution with
safety concerns, if any, associated with its use. It is the n-pentane to precipitate n-pentane insolubles, and filtration
responsibility of the user of this standard to establish appro- through a filtering crucible or 0.45 μm filter membrane.
priate safety and health practices and determine the applica-
5. Significance and Use
bility of regulatory limitations prior to use.
5.1 Sediment in insulating oil may deposit on transformer
2. Referenced Documents
parts and interfere with heat transfer and may choke oil ducts;
2.1 ASTM Standards: thus hindering oil circulation and heat dissipation. Inorganic
D 923 Practices for Sampling Electrical Insulating Liquids sediment usually indicates contamination of some type and
D 2440 Test Method for Oxidation Stability of Mineral organic sediment indicates either deterioration of the oil or
Insulating Oil contamination.
5.2 Soluble sludge indicates deterioration of the oil, pres-
3. Terminology
ence of contaminants, or both. It serves as a warning that
3.1 Definitions of Terms Specific to This Standard:
formation of sediment may be imminent.
3.1.1 inorganic sediment—that portion of the total sediment 5.3 The determination of sediment and soluble sludge in a
which remains after ignition at 500°C.
used insulating oil assists in deciding whether the oil may
3.1.2 organic sediment—that portion of the total sediment
continue to be used in its existing condition or should be
which is lost during ignition at 500°C. replaced, reclaimed, or reconditioned.
3.1.3 sediment—any solid substance or substances that are
6. Apparatus
insoluble in the oil under test at ordinary room temperatures,
and that can be separated by centrifuging under certain 6.1 Centrifuge Tube, 30-mL capacity, preferably with round
prescribed conditions. or elliptical bottom to facilitate removal of sediment. Pear-
3.1.4 soluble sludge—oil deterioration products or contami- shaped tubes are not recommended.
nants, or both, which become insoluble upon dilution with 6.2 Centrifuge, capable of whirling two or more filled
n-pentane under prescribed conditions. centrifuge tubes at a speed which can be controlled to give a
relative centrifugal force (rcf) between 600 and 700 at the tips
of the tubes. The revolving head, trunnion rings, and trunnion
cups, including the rubber cushion, shall be soundly con-
This test method is under the jurisdiction of ASTM Committee D-27 on
Electrical Insulating Liquids and Gases and is the direct responsibility of Subcom-
structed to withstand the maximum centrifugal force capable of
mittee D27.07 on Physical Test.
being delivered by the power source. The trunnion cups and
Current edition approved Oct. 10, 1997. Published December 1997. Originally
cushions shall firmly support the tubes when the centrifuge is
published as D 1698 – 59. Last previous edition D 1698 – 84 (1990).
Annual Book of ASTM Standards, Vol 10.03. in motion. The centrifuge shall be enclosed by a metal shield or
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 1698 – 97
case strong enough to eliminate danger if any breakage occurs. three washes of 25-mL portions each are sufficient. A drop of
Calculate the speed of the rotating head by means of the the final pentane naphtha washing should show no oil stain on
following equation: a filter paper.
9.5 Dry the sediment in the filtering crucible by suction, and
rpm 5 265 rcf/d
=
place in an oven at 105°C for drying to constant weight. Cool
in a desiccator and weigh to the nearest 0.0001 g.
where:
rcf = relative centrifugal force, and
10. Procedure for Organic and Inorganic Sediment
d = diameter of swing, in., measured between tips of
10.1 Wash the sediment in the filtering crucible with chlo-
opposite tubes when in rotating position,
roform or acetone until it is free of chloroform or acetone-
soluble material (see Note). Three washes of 25-mL portions
or:
d = diameter of swing CIN/2.54, measured between tips of each are usually sufficient.
opposite tubes when in rotating position.
10.2 Dry the sediment by suction and ignite in the crucible
6.3 Electric Muffle Furnace, capable of maintaining a tem-
in an electric muffle furnace at 500°C for 1 h, cool in a
perature of 500 6 15°C. desiccator, and weigh to the nearest 0.0001 g.
6.4 Explosion-Proof Oven, capable of maintaining a tem-
NOTE 1—If so desired, the chloroform or acetone washes can be
perature of 105 6 3°C.
combined and retained for further chemical analysis.
6.5 Filtering Crucible—Glass filter crucible having a maxi-
mum diameter of the pores of between 5 and 15 μm as
11. Procedure for Soluble Sludge
determined in accordance with the Appendix in Test Method
11.1 Place the crucible in an oven and dry a
...

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