ASTM D6181-97

Standard Test Method for Measurement of Turbidity in Mineral Insulating Oil of Petroleum Origin

SCOPE
1.1 This test method covers the laboratory procedure that ascertains the quantity of suspensions in insulating oils of petroleum origin using a nephelometric measurement technique to determine the fluid's turbidity. This test method is designed to reveal changes that may occur to these oils.  
1.2 This test method is applicable for turbidities in the range of 0.1 to 500 Nephelometric Turbidity Units (NTU).  
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.  
1.4 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.

General Information

• Status: Historical
• Publication Date: 09-Oct-1997
• ICS: 29.040.10 - Insulating oils
• Technical Committee: D27 - Electrical Insulating Liquids and Gases
• Drafting Committee: D27.07 - Physical Test

Relations

• Replaced By: ASTM D6181-03 - Standard Test Method for Measurement of Turbidity in Mineral Insulating Oil of Petroleum Origin (Withdrawn 2012)
• Effective Date: 01-Oct-2003

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact
ASTM International (www.astm.org) for the latest information.
Designation: D 6181 – 97
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Measurement of Turbidity in Mineral Insulating Oil of
1
Petroleum Origin
This standard is issued under the fixed designation D 6181; 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 One NTU is the turbidity of a formazine solution produced by
mixing 12.5 μg of hydrazine su1fate and 1.25 μg of hexa-
1.1 This test method covers the laboratory procedure that
methylenetetramine in 1 mL of turbidity-free water. See
ascertains the quantity of suspensions in insulating oils of
Appendix X1 for preparation instructions.
petroleum origin using a nephelometric measurement tech-
3.1.2 turbidity, n—the reduction of transparency due to the
nique to determine the fluid’s turbidity. This test method is
presence of particulate matter.
designed to reveal changes that may occur to these oils.
1.2 This test method is applicable for turbidities in the range
4. Summary of Test Method
of 0.1 to 500 Nephelometric Turbidity Units (NTU).
4.1 The turbidity is determined by a calibrated, ratio turbi-
1.3 The values stated in SI units are to be regarded as the
dimeter, which measures scattered light at 0.5 p rad (90°) or
standard. The values given in parentheses are for information
0.5 and 1.5 p rad (90 and 270°) angles to the incident beam.
only.
These instruments cannot be calibrated accurately in terms of
1.4 This standard does not purport to address all of the
absolute turbidity except in the case of fluids having uniform-
safety concerns, if any, associated with its use. It is the
size particles that are less than approximately one fifth of the
responsibility of the user of this standard to establish appro-
wave length of the incident light. Standards have been prepared
priate safety and health practices and determine the applica-
by thoroughly mixing suitable amounts of finely divided
bility of regulatory limitations prior to use.
titanium dioxide into partially polymerized polystyrene. Alter-
2. Referenced Documents
natively, suspension of formazine has been used as a turbidity
2.1 ASTM Standards: standard, formed by reacting hydrazine sulfate and hexameth-
6
ylenetetramine under carefully controlled conditions. Cali-
D 923 Test Method for Sampling Electrical Insulating Liq-
2
uids brated commercial standards in sealed tubes also are available.
D 1533 Test Methods for Water in Insulating Liquids (Karl 4.2 The test specimen is placed in the cell and its turbidity
2
Fischer Reaction Method) is measured. The turbidimeter measures the light scattered by
D 1698 Test Method for Sediments and Soluble Sludge in suspended solids dispersed within the test specimen. Accuracy
2
and sensitivity of the method is ensured by measuring the
Service Aged Insulating Oils
3
D 1889 Test Method for Turbidity of Water turbidity at a wavelength of light where there is little or no
absorption of the light by the test specimen. Use of a narrow
D 4652 Specification for Silicone Fluid Used for Electrical
2
Insulation bandwidth of light reduces interference that may be inherent to
these insulating oils. The narrow bandwidth is achieved
D 5180 Test Method for Quantitative Test for Turbidity in
4
Clear Liquids through the use of an optical filter to provide light at 600 nm
with a 40 nm bandwidth.
E 177 Practice for Use of the Terms Precision and Bias in
5
ASTM Test Methods 4.3 This test method is recommended only for mineral oils
and is not intended to be used on other fluids.
3. Terminology
5. Significance and Use
3.1 Description of Terms Specific to This Standard:
3.1.1 nephelometric turbidity unit (NTU), n—intensity of
5.1 This test method uses a ratio turbidimetric optical
light scattered by a known aqueous suspension of formazine.
system to measure the turbidity of insulating oils relative to
turbidity standards. Cloudiness or turbidity is attributed to
1
matter whose diameter is approximately 20 % of the wave-
This test method is under the jurisdiction of ASTM Committee D-27 on
Electrical Insulating Liquids and Gasesand is the direct responsibility of Subcom-
length of the incident light. Increasing turbidity signifies
mittee D27.07on Physical Test.
increasing transformer fluid contamination. This test method
Current edition approved Oct. 10, 1997. Published March 1998.
2
Annual Book of ASTM Standards, Vol 10.03.
3
Annual Book of ASTM Standards, Vol 11.01.
4 6
Annual Book of ASTM Standards, Vol 06.03. For information, see Chevalier, P., “Forma
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