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D445_12 (17a)

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For steam-refined cylinder oils and black lubricating oils, proceed to 12.2 of the written standard, ensuring a thoroughly representative sample is used. The kinematic viscosity of residual fuel oils and similar waxy products can be affected by the previous thermal history, and the following procedure described in 12.1.1 to 12.1.8 of the written standard shall be followed to minimize this. In general, the viscometers used for opaque liquids are of the reverse flow type listed in table A1.1 of the written standard. Heat the sample in the original container at a temperature between 60 degrees Celsius and 65 degrees Celsius for one hour. Place the BS/IP/RF/U-Tube reverse flow, or Zeitfuchs Cross-arm, or Lantz-Zeitfuchs type reverse flow viscometer for the samples to be tested in the viscometer bath or baths at the required test temperature. If the viscometers are to be charged prior to insertion in the viscometer bath, for example Cannon Fenske Opaque, see 12.2.1 of the written standard. Upon completion of step 12.1.2 of the written standard, vigorously stir each sample for approximately 20 seconds with a glass or steel rod of sufficient length to reach the bottom of the container. For samples of a very waxy nature, or oils of high kinematic viscosity, it may be necessary to increase the heating temperature above 65 degrees Celsius to achieve proper mixing. The sample should be sufficiently fluid for ease of stirring and shaking. Remove the stirring rod and inspect for sludge or wax adhering to the rod. Continue stirring until there is no sludge or wax adhering to the rod. Recap the container tightly and shake vigorously for one minute to complete the mixing. To protect the integrity of the sample should a repeat analysis be required, pour sufficient sample to fill two flasks and loosely stopper. Each flask should hold sufficient sample to fill two viscometers in order to obtain two determinations. The second flask is required to carry out a repeat analysis. If a repeat analysis is not a consideration, the next steps can be performed using the original container, loosely capped. Heat the first sample flask, or sample container, between 100 degrees Celsius and 105 degrees Celsius for 30 minutes. Remove the first sample flask or sample container from the heat, close tightly, and shake vigorously for 60 seconds. Two determinations of the kinematic viscosity of the test material are required. For those viscometers that require a complete cleaning after each flow time measurement, two viscometers must be used. These two determinations are used to calculate one result. Charge two viscometers in the manner dictated by the design of the instrument. For example, for the Lantz-Zeitfuchs Cross-arm, or the BS/IP/RF/U-Tube reverse flow viscometers for opaque liquids, filter the sample through a 75 UM filter into two viscometers previously placed in the bath. For samples subjected to heat treatment, use a pre-heated filter to prevent the sample coagulating during the filtration. Viscometers which are charged before being inserted into the bath may need to be preheated in an oven prior to charging the sample. This is to ensure that the sample will not be cooled below test temperature. After 10 minutes, adjust the volume of the sample where the design of the viscometer requires to coincide with the filling marks as in the viscometer specifications. See specifications D446. Allow the charged viscometers enough time to reach the test temperature. See 12.2.1 of the standard. Where one bath is used to accommodate several viscometers. Never add or withdraw or clean the viscometer while any other viscometer is in use for measuring flow time. With the sample flowing freely, measure in seconds to within 0.1 second the time required for the advancing ring of contact to pass from the first timing mark to the second. Record the measurement. In the case of samples requiring heat treatment described in 12.1 through 12.1.8 of the written standard, complete the measurements of flow time within one hour of completing 12.1.8 of the written standard. Record the measured flow times. Calculate kinematic viscosity, v, in millimeters squared per second from each measured flow time. Regard these as two determined values of kinematic viscosity. For residual fuel oils, if the two determined values of kinematic viscosity agree, within the stated determinability figure, see 17.1.1 of the written standard, use the average of these determined values to calculate the kinematic viscosity result to be reported. This constitutes one analysis. Record the result. If a second value, repeat, is required, then repeat the analysis after a thorough cleaning and drying of the viscometers, starting from sample preparation steps 12.1.6 of the written standard using the second flask. If the original container has been conditioned using steps 12.1.2 to 12.1.8 of the written standard, then this is not suitable for a repeat analysis. If the calculated kinematic viscosities do not agree, repeat the measurements of flow times after a thorough cleaning and drying of the viscometers and filtering of the sample. If the material or temperature or both is not listed in 17.1.1 of the written standard, for temperatures between 15 degrees Celsius and 100 degrees Celsius, use an estimate of the determinability 1.0% and 1.5% for temperatures outside this range. It must be realized that these materials can be non-Newtonian, and can contain solids, which can come out of solution as the flow time is being measured. See section 12.5.1 of the written standard for information on calculating kinematic viscosity of residual fuel oils. In this particular case, the viscometer tube calibration constant, C, equals 0.305 millimeters squared per second squared. Using the flow time measurement from test number one, 376.66 seconds, calculate the kinematic viscosity determination using the following equation. 376.66 seconds times 0.305 millimeters squared per seconds squared equals 114.88 millimeters squared per second. Calculate the second kinematic viscosity determination using the flow time measurement from test number two, 390.03 seconds. 390.03 seconds times 0.305 millimeters squared per seconds squared equals 118.96 millimeters squared per second. Determine the difference between the two kinematic viscosity results. Average kinematic viscosity determinations 1 and 2. Use the determinability calculation for residual fuel oils at 50 degrees Celsius from section 17.1.1 of the written standard. 0.017 times y, where y is the average of the determined values being compared. 0.017 times y equals 0.017 times 116.92 millimeters squared per second equals 1.98 millimeters squared per second. Because 4.08 millimeters squared per second is greater than 1.98 millimeters squared per second, the measurements are considered to not meet ASTM D445 determinability for this material type, and the results should not be reported. The operator must repeat the measurements of flow times after a thorough cleaning and drying of the viscometers and filtering of the sample as per section 12.5.1 of the written standard.

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Posted by: abuckmaster on Aug 22, 2018

D445_12 (17a)

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