ASTM D5452 Standard Test Method for Particulate Contamination in Aviation Fuels by Laboratory Filtration
11. Procedure
11.1 Prepare the Filter Funnel and Filter Base Assembly - Using clean forceps, place the two test membrane filters centrally on the membrane filter support ring of the filtration apparatus (see Fig. 1) with the test membrane on top of the control membrane. Install the filter funnel. If using matched weight membranes, either one can be on top. With the membrane filter in place, perform a continuity test using a multimeter between the filter funnel and the filter holder. The meter shall read 10 Ω or less.

11.2 Prepare the Sample Container for the Filtration Test:
11.2.1 Thoroughly clean the outside of the sample container in the region of the closure by washing with detergent in water and rinsing with tap water and filtered isopropyl alcohol. Remove all labels from the container top. Shake the container vigorously for about 1/2 min to flush particles from internal surfaces of the installed plug or cap into the fuel in the container. Remove the closure. If it is a cap, remove any external contaminant that may be present in the threads on the sample container by washing with filtered flushing fluid, ensuring that none of the washings enter the container.

NOTE 4 - If the closure is a plug, preserve it in a clean petri dish for flushing at 11.2.5 or at 11.4.9. If it is a cap, it will not be flushed at 11.4.9, because its internal threads can be contaminated with external dirt.

11.2.2 If it has been determined that the fuel sample has a verified flash point greater than 38°C and that the sample is therefore to be poured into the filter funnel rather than to use the support stand, connect the receiving flask and safety flask with hose and connect the grounding cable assembly as shown in Fig. 1. Place the pre-assembled filter funnel and filter base assembly on the receiving flask. This filtration procedure will definitely result in electrostatic charges that shall be grounded for safety. Refer to Appendix X2.

11.2.3 Commence pouring the sample into the filter funnel and switch on the vacuum source. Move (swirl) the sample container about in order to carry particles into the funnel.

11.2.4 After the fuel has filtered completely, disconnect the vacuum, and record the volume of the filtered sample.

11.2.5 If the sample had been transferred from other containers, rinse them with four 50-mL quantities of filtered flushing fluid directly into the filter funnel. The external threads of the sample container plug may now be rinsed with 30 mL of filtered flushing fluid directly into the filter funnel. Then, proceed to 11.4.10.

11.3 If it was determined that the support stand should be used for filtering the fuel sample, prepare the apparatus.

NOTE 5 - All of this apparatus should be mounted in an exhaust hood to minimize operator exposure to fumes.

11.3.1 Connect the receiving flask and safety flask with hose, and connect the grounding cable assembly as shown in Fig. 1. Place the pre-assembled filter funnel and filter base assembly on the receiving flask. Ensure the adjustable shelf is located approximately 25 - 50 mm above the top of the filter funnel. This filtration procedure will definitely result in electrostatic charges that must be grounded for safety. Refer to Appendix X2.

11.3.2 Secure a ground clip and wire to the container support and ground in series as shown in Fig. 1.

11.3.3 Screw the dispensing closure from 6.12 firmly on the sample container. Slip a length of plastic tubing mentioned in 6.12 snugly over the hose barb of the above (dispensing plug or cap). If the closure will not fit the original sample container, shake the original sample container briefly, and quickly transfer the sample, by use of a funnel, to another container that can be equipped with a dispensing cap or plug. Ensure that the new container has been rinsed as described in Section 9. Preserve at a clean location the now empty original container pending flushing at 11.4.8.

11.4 Transfer the Fuel in the Sample Container to the Filter Funnel:
11.4.1 The length of the tubing on the dispensing plug or cap should be sufficient such that when the sample container is resting on the shelf, the tubing will extend well into the filter funnel, approximately halfway down to where the cone transition is located.

NOTE 6 - The reason for this is that the operator is instructed in this procedure to shake the sample container every minute. A short tube can accidentally come out of the funnel. if the outlet end of the tube is submerged in the fuel as little as 5 mm, flow into the filter funnel will stop to prevent overflow.

11.4.2 Fold down any container handle that is present, and double over or crimp the plastic tubing installed on the dispensing plug or cap. Grasp the container firmly and shake gently and carefully release vapor from the container by venting through the plastic tubing away from the face. Quickly crimp the tubing again and hold in place.

11.4.3 Carefully invert the container and position it over the shelf and filter funnel, releasing the tubing into the funnel just before resting it on the shelf.

11.4.4 As the filter funnel is filling, secure a grounding clip and wire to the container and electrically ground in series with all other grounds.

NOTE 7 - A small clamp, pinchcock, or fingertip pressure may be used to assist in crimping the tubing.

11.4.5 When the fuel has ceased flowing into the funnel, switch on vacuum source, stand well clear, and allow the fuel to filter. Agitate the container every minute during filtration by grasping firmly on both sides of the container and lifting the can approximately 1 cm off of the base and briefly shake the container for approximately 5 s.

11.4.6 Move (swirl) the container about in order to drain any residual fuel into the funnel.

11.4.7 After fuel has filtered completely, disconnect the vacuum, and record the volume of the filtered sample.

11.4.8 If the sample had been transferred from another container, rinse the original container with four 50-mL quantities of filtered flushing fluid directly into the filter funnel using a separate funnel, if necessary, that has been cleaned as in Section 9. Rinse the test container with four 50-mL quantities of filtered flushing fluid. If a separate funnel was used, rinse it with 30 mL of filtered flushing fluid into the filter funnel.

NOTE 8 - If the original containers or test containers are of a type such that they retain some of the fuel, record the volume of flushing fluid that was used to help in displacing particles and that fuel so that it can be deducted from the total volume in the receiving flask after the test and all flushing and rinsing operations have been completed. (See X2.7.6.1.)

11.4.9 Referring to Note 4, regarding closures, a plug from the original sample container should be rinsed using 30 mL of filtered flushing fluid directly into the filter funnel and onto the membrane filter. Do not rinse a cap internally or externally, and do not rinse the external surface of a plug.

11.4.10 Wash down the inside of the filter funnel with filtered flushing fluid. With the vacuum applied, carefully separate the funnel from the filter base by releasing the locking ring. To ensure that all test product has been flushed through the membrane filter, direct a gentle stream of filtered flushing fluid toward the middle, being careful not to shift position of any particles. This flushing action has the purpose of washing residual fuel through the membrane filters that are at the juncture of the funnel flange and the filter base. Maintain vacuum after the final washing only for the few seconds necessary to remove excess filtered flushing fluid from the membrane filter.

11.5 Using clean forceps, carefully remove the test and control membrane filters from the filter base, and place them on glass supports in a clean, covered petri dish. Dry and reweigh the membrane filters as described in 10.1.2-10.1.5, taking great care not to disturb the contaminant on the surface of the test membrane filter.