GB/T 12581-2006Standard test method for oxidation characteristics of inhibited mineral oils (English PDF)

5.4 Heating Bath Thermometer-oxidation characteristic No. 2 thermometer having a

range from 72 to 126°C, and conforming to the requirements for thermometer GB-58 as prescribed in GB/T 514. Alternatively, temperature measuring devices of equal or better accuracy may be used.

5.5 Oxidation Cell Thermometer, oxidation characteristic No. 1 thermometer having

a range from 80 to 100°C, graduated in 0.1°C, total length-250mm, stem diameter-6.0 to 7.0mm, calibrated for 76-mm immersion, and conforming to the requirements for thermometer GB-57 as prescribed in GB/T 514. Alternatively, temperature measuring devices of equal or better accuracy may be used.

5.6 Thermometer Bracket, for holding the oxidation cell thermometer, of 1Cr18Ni9Ti

stainless steel, having the dimensions shown in Figure 2. The thermometer is held in the bracket by two fluoroelastomer O-rings of approximately 5mm inside diameter.

Alternatively, thin stainless steel wire may be used.

length and 15.9 to 16.5mm inside diameter. The turns of wire are evenly spaced, and two consecutive turns of the same wire are 3.96 to 4.22mm apart, center to center. The mandrel shown in Figure 3 is designed to produce such a coil. Using this mandrel, the iron wire is wound on a thread of 14.98-mm diameter, while the copper wire is wound on a thread of

15.9-mm diameter. The smaller diameter is to allow for springback of the iron wire after winding, so as to give 15.9-mm consistent inside diameter. Use of a very soft annealed steel wire may allow use of identical thread diameters for the two wires. Any arrangement that leads to the coil configuration described above is satisfactory.

8.3 Catalyst storage

The catalyst coil may be stored in a dry, inert atmosphere prior to use. A suitable procedure for catalyst storage is given in Appendix B. Before use it should be inspected to ensure that no corrosion products or contaminating materials are present.

For overnight storage (less than 24h) the coil may be stored in n-Heptane.

N-Heptane used for catalyst storage must be free of traces of water and corrosive materials. Redistilled n-Heptane conforming to 6.6 and stored in a tightly sealed bottle is suitable.

8.4 Cleaning new glassware

Wash new oxygen delivery tubes, condensers, and test tubes with a hot detergent solution and rinse thoroughly with tap water. Clean the interiors of the test tubes, exteriors of the condensers, and both interiors and exteriors of the oxygen delivery tubes with cleaning reagent. Rinse thoroughly with tap water until all cleaning solution is removed. Rinse all parts with distilled water and allow drying at room temperature or in an oven. The final distilled water rinse may be followed by an isopropyl alcohol rinse, or acetone rinse, optionally followed by dry air blowing, to hasten drying at room temperature.

8.5 Cleaning used glassware

Immediately following termination of a test, drain the oil completely from the test tube.

Rinse all the glassware with n-Heptane to remove traces of oil, wash with a hot detergent solution using a long-handled brush, and rinse thoroughly with tap water. If deposits still adhere to the glassware, a method that has been found useful is to fill the test tubes with detergent solution, insert the oxygen delivery tubes and condensers, and place the tubes in the heating bath at test temperature. Several hours soaking in this manner often serves to dissolve all adhering deposits except iron oxide.

Subsequent rinsing with hot (50°C) hydrochloric acid will serve to remove iron oxide.

After all deposits are removed, rinse all glassware with a cleaning reagent. Rinse thoroughly with tap water until all acid is removed. Rinse all parts with distilled water and allow drying at room temperature or in an oven. The final distilled water rinse may be followed by an isopropyl alcohol rinse, or acetone rinse, optionally followed by dry air blowing, to hasten drying at room temperature. Store glassware in a dry dust-free condition until ready to use.

8.6 Cleaning used sampling tube

Immediately following termination of a test, drain the oil completely from the sampling tube. Rinse the tube with n-Heptane to remove traces of oil and any tenacious organic residues. Repeat the rinsing procedure with n-Heptane and blow dry with air or nitrogen.

9.3 Connect the oxygen delivery tube to the oxygen supply through the flowmeter

using new polyvinyl chloride flexible tubing no more than 600mm in length. Before using, the interior of the new polyvinyl chloride flexible tubing should be rinsed with n-Heptane and blown dry with air. Adjust the rate of flow to 3±0.1L and continue flow for 30min.

9.4 Raise the condenser unit from the oxidation cell and add 60mL of distilled water into the test tube, and record the oxidation time.

9.5 To set the bath temperature use only a new, undepleted, oil sample with water and oxygen flowing as described in 9.2 or a dummy cell used specifically for temperature measurement. The dummy cell shall contain undepleted oil sample with

A - the number of test hours when acid number was last measured below

2.0mgKOH/g, in h;

B - the number of test hours when acid number was measured above 2.0mgKOH/g, in h;

C - the acid number at A hours, in mgKOH/g;

D - the acid number at B hours, in mgKOH/g.

11.1 Report the calculated hours to 2.0mgKOH/g acid number (oxidation lifetime), in

h.

11.2 If the acid number is still less than 2.0mgKOH/g after 10000h, the test shall be terminated. Since the maximum oil oxidation lifetime is limited to 10000h, report the test life and acid number as >10000h (AN=x.xx).

12.1 Repeatability r

The difference between concurrent test results obtained by the same operator with the same apparatus according to the same test method on identical test materials, would not exceed the value of Formula (2):

r=0.192X (2)

Where,

X - the arithmetic mean of duplicate determination results.

12.2 Reproducibility R

The difference between two single and independent results, obtained by different operators working in different laboratories with different apparatuses and with the same method on identical test material, would not exceed the value of Formula (3):

R=0.33 X (3)

Where,

X - the arithmetic mean of two determination results.

Note: Reproducibility with duplicate tests, R .

If two successive tests are performed by each operator in 12.2, the difference between the averages of the two sets of results from the tests would not exceed the value of Formula (4):

R =0.302 X (4)

Where,

X - the mean value of the averaged results from the two laboratories.

If more than two results are obtained by one or both of the laboratories, the reproducibility of the mean value can be calculated according to GB/T 17039.

Appendix A (Normative)

Semiquantitative Microdetermination of Acid Number of

Lubricating Oils during Oxidation Testing

A.1 Scope

A.1.1 This test method belongs to semiquantitative microdetermination method, applies to monitor the variation of acidic component of lubricating oil sample during the oxidation test within the acid number of 0.02mgKOH/g~1.0mgKOH/g, and is applicable to steam turbine oils, hydraulic oils and other circulating oils.

Note: This method is the microdetermination edition of GB/T 4945, and the results obtained from two methods are similar.

A.1.2 This test method is design for the condition of limited sample quantity. This method should not replace the method with higher accuracy, e.g. GB/T 4945 or GB/T

7304, and this method is not applicable to the monitoring of in-use oils.

A.2 Term

For the purposes of this Standard, the following term applies.

Acid number

Alkali quantity required for the sample dissolved through titration in designated solvent reaching the designated end point, which is expressed with milligram of potassium hydroxide/gram of sample.

Note: In this test method, when sample is dropped into volumetric solution to change the solution color from blue green to orange yellow, the acid number may be calculated through comparing the drops of added sample with the drops of added reference sample for using reference sample to make the volumetric solution have the same color change, because this is a direct comparison method, the obtained acid number may be reported as milligram of potassium hydroxide/gram of sample.

A.3 Summary of test method

A.3.1 Use a dropper to drop the sample into a portion of 2.0mL volumetric solution, and record the sample drops required for volumetric solution changing into stable orange yellow from green blue.

Dissolve potassium hydroxide into isopropyl alcohol to prepare into about 0.1M solution. Calibrate this solution with pure potassium hydrogen phthalate dissolved into

100mL of water, and detect the end point by using phenolphthalein as an indicator.

(commercially available reagents may be used)

Warning - Corrosive, toxic if inhaled, alkalic, stimulating to dermatitis.

A.6.4 Dodecenyl succinic anhydride

Warning - Stimulating to skin and eye.

A.6.5 P-naphtholbenzein indicator solution

P-naphtholbenzein must meet the specification requirements in Appendix A of GB/T

4945-2002. Prepare solution containing 10g/L of p-naphtholbenzein in mixed 50:50 methylbenzene and isopropyl alcohol solvent.

Warning - Flammable, vapor harmful.

Note: Fisher and other companies may provide p-naphtholbenzein indicator solution.

A.6.6 Isopropyl alcohol

Warning - Flammable, report indication; if no inhibition, generate peroxide and form explosive mixture when the container for storing isopropyl alcohol or reagent preparation bottle is empty and near to dryness.

A.6.7 Volumetric solution

Mix 350mL of methylbenzene, 350mL of isopropyl alcohol and 7mL of p-naphtholbenzein solution in a 1L plastic bottle, add 15mL of 0.1M potassium hydroxide isopropyl alcohol solution, and mix uniformly. (Warning - Flammable, vapor harmful, corrosive)

Note: The concentration of volumetric solution will drop with time, thus the volumetric solution needs to be replaced periodically, and one replacement every month may meet the requirements.

A.6.8 Methylbenzene

Warning - Flammable, vapor harmful.

A.7 Procedure

A.7.1 Sampling

Extract a minimum of test oil from oxidation cell according to the procedure specified in the oxidation test method.

The difference between two continuous test results, obtained by the same operator with the same apparatus and with the same test method on identical sample, would not exceed the value of Formula (A.3):

ra=0.2 n

Ax (A.3)

Where, n

A - the arithmetic mean of two determination results.

A.9.1.2 Reproducibility R.

The difference between two single and independent results, obtained by different operators working in different laboratories with different apparatuses and with the same method on identical sample, would not exceed the value of Formula (A.4):

Ra=0.7 n

Ax (A.4)

Where, n

A - the arithmetic mean of two determination results.

A.9.2 Bias

This test method has no bias as the acid number is only determined according to the test method.

Appendix B (Informative)

Procedure for Packaging Catalyst Coils

B.1 Materials

B.1.1 Test tubes, borosilicate glass, 250-mm length, 25-mm outside diameter, approximately 22-mm inside diameter.

B.1.2 Caps, for test tubes, polyethylene cylindrical shape designed to closely grip outside surface of test tube.

B.1.3 Desiccant bags, of silica gel granules.

B.1.4 Flushing tube, stainless steel or glass, approximately 5mm outside diameter,

305mm long, to deliver nitrogen to bottom of test tube.

B.1.5 Nitrogen gas, 99.7% minimum purity.

Warning - Compressed gas under high pressure. Gas reduces oxygen available for breathing.

B.2 Procedure

Flush a new test tube with nitrogen gas, using the flushing tube, to blow out any loose particles. The tube must be visibly clean and dry. Hold the tube on an angle and gently slide the catalyst coil into the tube. Add a desiccant bag that has been folded lengthwise to fit in the tube. Insert the nitrogen flushing tube down the middle of the test tube, to the bottom, and blow nitrogen through the tube for several seconds.

Immediately after withdrawing the flushing tube, seal the test tube with a polyethylene cap.

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