ASTM D4625 Method for Middle Distillate Fuel Storage Stability at 43°C (110°F)
9. Preparation of Apparatus and Sample Bottles
9.1 Sample Storage Bottles - Scrub each bottle with a detergent solution and rinse it with water. Soak the bottle overnight in a mildly alkaline laboratory glassware cleaning solution. Rinse the bottle with tap water, then invert it and flush it with a stream of distilled water. Allow the bottles to dry and rinse the bottles with 50 mL of the fuel sample. Vent the bottles during storage, using a glass tube bent in an upside down "U", (see Fig. 2), to prevent contamination of the sample from airborne particulates. Insert the glass tube through a cover, preferably equipped with a polytetrafluoroethylene (PTFE) insert (see Fig. 2).
9.2 Clean all components of the filtration apparatus as described in 9.2.1-9.2.7.
9.2.1 Remove any labels, tags, and so forth.
9.2.2 Wash with warm tap water containing detergent.
9.2.3 Rinse thoroughly with warm tap water.
9.2.4 Rinse thoroughly with deionized water. Container caps should be handled only externally with clean laboratory crucible tongs during this and subsequent washings.
9.2.5 Rinse thoroughly with propan-2-ol that has been filtered through a 0.45-µm membrane filter.
9.2.6 Rinse thoroughly with filtered flushing fluid and dry.
9.2.7 Keep a clean protective cover (the cover may be rinsed with filtered flushing fluid) over the top of the sample container until the cap is installed. Similarly, protect the funnel opening of the assembled filtration apparatus with a clean protective cover until ready for use.
9.3 Preparation of Membrane Filters:
9.3.1 Each set of test filters consists of one test membrane filter and one control membrane filter. For fuels containing little particulate materials, only one set of filters is required. If the fuel is highly contaminated, more than one set of filters may be required. The two membrane filters used for each individual test shall be identified by marking the petri dishes used to hold and transport the filters. Clean all glassware used in preparation of membrane filters as described in 9.2.
9.3.1.1 Using forceps, place the test and control membrane filters side by side in a clean petri dish. To facilitate handling, the membrane filters should rest on clean glass support rods, or watch glasses, in the petri dish.
9.3.1.2 Place the petri dish, with its lid slightly ajar, in a drying oven at 90 ± 5°C and leave it for 30 min.
9.3.1.3 Remove the petri dish from the drying oven, and place it near the balance. Keep the petri dish cover ajar, but keep it such that the membrane filters are still protected from contamination from the atmosphere. Allow 30 min for the membrane filters to come to equilibrium with room air temperature and humidity.
9.3.1.4 Remove the control membrane filter from the petri dish with forceps, handling by the edge only, and place it centrally on the weighing pan of the balance. Weigh it, record the initial mass to the nearest 0.0001 g, and return it to the petri dish.
9.3.1.5 Repeat 9.3.1.4 for the test membrane filter.
9.3.1.6 Using clean forceps, place the weighed control membrane filter centrally on the membrane filter support of the filtration apparatus (see Fig. 1). Place the weighed test membrane filter on top of the control membrane filter. Install the funnel and secure with locking ring or spring clip. Do not remove the plastic film from the funnel opening until ready to start filtration.
10. Preparation of Sample
10.1 If the fuel has been stored at reduced temperature, allow the sample to come to ambient temperature. To dissolve any separated wax, be certain that the entire fuel sample is at least 5°C above its cloud point before proceeding.
10.2 Assemble a filtration system, as shown in Fig. 1, to filter the fuel. Clean the receiving flask, separatory funnel, and glass funnel in the same manner as the storage bottles (9.1). Rinse these items with filtered isooctane and then air.
