1、INTERNATIONAL STANDARD First edition 1995-02-01 -a Int, Do, s ee Petroleum products - Determination of the oxidation stability of middle-distillate fuels Produits p. 1 i :. ! r, 1 B I i ! / ) IS0 12205:1995(E) 7.3 Preparation of evaporating beakers ry Filter funnel filter Figure 2 - Filter assembly
2、Dry the cleaned evaporating vessels (6.8) for 60 min in the oven (6.5). Place the beakers in the desiccator (6.91, and allow to cool for 60 min. Weigh the beakers to the nearest 0,l mg. 8 Sampling 8.1 Samples shall be taken by the procedure de- scribed in IS0 3170, IS0 3171 or an equivalent na- tion
3、al standard. support 6.9 General apparatus A balance capable of weighing to 0,l mg, a hotplate capable of heating the liquid in the evaporating ves- sels (6.8) to 135 “C, a desiccator (without desiccant), spade-ended forceps for handling the filter media, and a suitable timing device. 7 Apparatus pr
4、eparation 7.1 Preparation of glassware other than oxidation cells Rinse all glassware thoroughly with trisolvent (5.4) followed by water, then wash with a mildly alkaline or neutral laboratory detergent. Rinse three times with grade 3 water (5) followed by acetone (5.1) to remove water, and allow to
5、 dry. 7.2 Preparation of oxidation cells and accessories After completion of 7.1, fill oxidation cells with lab- oratory detergent in grade 3 water (5). Place the oxy- gen delivery tube in the oxidation cell, place the condenser over the oxygen delivery tube, and allow to soak for at least 2 h. Wash
6、, drain, then rinse five times with tap water followed by three rinses with grade 3 water (5). Rinse with acetone (5.11, drain, and allow the oxidation cell and delivery tube to dry. 8.2 Test portions from the samples shall be drawn after thorough mixing and subdivision away from di- rect sunlight,
7、and in an area that would be compatible with other laboratory operations. Storage before stress, the stress period and cool-down after stress- ing shall occur in the dark. 8.3 Containers for samples shall be of metal lined with epoxy resin or similar material, previously rinsed twice with the materi
8、al to be sampled, or borosilicate glass, if they are wrapped or boxed to exclude light. Do not use soft (soda) glass containers, or plastic containers (due to the potential for leaching of plasticizers). 8.4 Analyse fuel samples as soon as possible after receipt. NOTE 6 If a fuel cannot be tested wi
9、thin one day, it should be blanketed with an inert gas such as oxygen-free nitrogen, argon or helium, and stored at a temperature no higher than 10 “C, but not lower than its cloud point. 9 Sample preparation 9.1 If the received sample is in a tank, drum or container exceeding 19 I capacity, use the
10、 subdivision procedures described in 8.2. 9.2 Thoroughly mix smaller samples by shaking, rolling or other techniques before taking a laboratory sample by pouring, pipetting or other means. 9.3 Clean any tube, thief, pipette, beaker or other apparatus or equipment that is to come into contact with th
11、e received sample, with trisolvent (5.4) fol- lowed by a portion of the sample prior to use. Allow samples that have been stored at temperatures sig- nificantly below 10 “C to warm to room temperature, and examine for the absence of any undissolved wax prior to mixing thoroughly and taking an aliquo
12、t. 4 NOTE 7 Warming allows any separated wax to redis- solve, and the viscosity to decrease to a point at which mixing is effective. Agitation during the warming period as- sists the redissolution of the wax. 10 Procedure 10.1 Sample filtration or plastic to prevent entrance of dirt or dust. Record
13、the time of removal as an interval from zero time. Place the cell(s) in a dark ventilated site at room tem- perature, which shall be above the cloud point of the fuel. Leave the samples until they have attained room temperature, but for no longer than 4 h. 10.4 Determining filterable insolubles Plac
14、e a single filter membrane (6.7) on the filter sup- port, and clamp the filter funnel to the support as shown in figure2. Apply suction of approximately 80 kPa (an absolute pressure of approximately 20 kPa in the flask). Pour 400 ml of the fuel through the filter (6.7) into a clean (7.1) 500 ml glas
15、s suction flask. After filtration is complete, discard the filter medium. Repeat preparation for each sample to be run. Never use the same filters for a second increment of fuel, because any material deposited on the filters by a previous increment of fuel can result in a greater removal of solids f
16、rom the next increment. 10.2 Assembling the oxidation apparatus Place a clean oxygen delivery tube into a clean oxidation cell (7.21, and pour 350 ml + 5 ml of the fil- tered fuel into the cell. As soon thereafter as possible, but never more than 60 min after measuring the fuel, immerse the test cel
17、l in the heating bath (6.2) such that the level of fuel in the oxidation cell shall be be- low the level of the liquid medium in the heating bath. During any interim period, store the cell in the dark. Place a condenser over the oxygen delivery tube and oxidation cell; connect the condenser to the c
18、ooling water. Connect the oxygen delivery tube to the oxy- gen supply through the flowmeter, and adjust the oxygen flow to 3,0 I/h &- 0,3 I/h. Ensure samples are protected from light. Record the time the first oxidation cell is placed in the bath as zero time, and allow the cell to remain in the bat
19、h for 16,00 h & 0,25 h. Note the sequence of placement of oxidation cells in the bath. When the number of test cells is less than the ca- pacity of the heating bath, the bath shall be filled with oxidation cells containing 350 ml of a stable liquid. No oxygen delivery tube or condenser is required f
20、or these “dummy” tubes. 10.3 Cooling the sample Remove the sample(s) from the heating bath in the same sequence as they were placed therein, cover the opening of each cell with a piece of aluminium foil Assemble the filter apparatus as illustrated in figure2, using one pair of matched mass filters (
21、6.7). Apply suction (approximately 80 kPa), and pour the cooled sample through the filter. Pull all the fuel through the filter before completely rinsing the oxidation cell and oxygen delivery tube with three separate 50 ml * 5 ml volumes of 2,2,4-tri- methylpentane (5.5). Pass all rinsings through
22、the fil- ter assembly. After filtration is complete, disconnect the top part of the filter assembly and wash down the rim of the filter-media-adjacent parts of the filter assembly with a further 50 ml * 5 ml of 2,2,4-trimethylpentane. Discard the filtrate. Dry the two filter media at 80 “C for 30 mi
23、n, cool them for 30 min, and weigh the upper (sample) and lower (blank) filters separately to the nearest 0,l mg. NOTE 8 Using matched mass filters assumes no col- lection of sediment on the lower filter medium that has passed through the upper medium, and that the blank cor- rection is for sample/s
24、olvent absorption. Occasionally, ma- terial is retained on the lower filter after having passed through the upper medium. If there is a visible deposit, or if the mass gain of the lower filter exceeds 10 mg, the sum of the mass gains should be used for the calculations. If severe filter plugging occ
25、urs, and filtration cannot be completed within 120 min. filter the remaining fuel through a separate set of weighed filters, using a fur- ther 50 ml + 5 ml portion of 2,2,4-trimethylpentane to wash down the filter media and filter assembly. 10.5 Determining adherent insolubles After completing the r
26、insing of the oxidation cell and oxygen delivery tube as described in 10.4, dissolve the adherent insolubles from them using three equal rinses of trisolvent (5.4) totalling 75 ml f 5 ml. The oxidation cell and oxygen delivery tube shall be ex- amined for evidence of stain or colour, indicating in-
27、complete removal. If such stain or colour is noted, rinse with a fourth 25 ml volume of trisolvent. Either collect the rinsings in one or more tared 100 ml beakers (6.8) as specified in IS0 6246 and evaporate the trisolvent mixture at 160 “C by the air jet procedure described in IS0 6246, or alternatively, collect the rinsings in a tared 200 ml beaker (6.8) and evaporate the trisolvent mixture with extreme caution
