ASTM D5275 Test Method for Fuel Injector Shear Stability Test (FISST) for Polymer Containing Fluids
10. Procedure
10.1 Shearing is accomplished by pumping the entire 100 cm3 test oil charge through the nozzle in successive passes or cycles. One cycle consists of pumping the oil from the lower reservoir (8) in Fig. A1.1, through the nozzle (5), and into the upper reservoir (6). At the end of each cycle, when the entire test oil charge has been collected in the upper reservoir (6), the pump (2) stops and the solenoid-operated drain valve (7) opens, draining the oil into the lower reservoir (8). The pump then restarts automatically for the next cycle. This process repeats for the number of cycles that have been set on the cycle counter. At the end of the last cycle, both solenoid-operated drain valves, (7) and (9) in Fig. A1.1, open and the test oil drains into the sample collection bottle (10).
10.2 Flush the apparatus with four separate 20 cm3 portions of the test oil as described in 10.2.1 and drain. Do not use solvent as part of the flush at any time because it could cause contamination.
10.2.1 Pour the first 20 cm3 charge of test oil into the lower reservoir, (8) in Fig. A1.1, through the funnel (14). Set the cycle counter for five cycles of the fluid through the nozzle, the pump timer for 15 s and the valve time for 20 s.
10.2.2 Repeat 10.2.1 three more times, draining and discarding each flush.
NOTE 3 - These timer settings have been found satisfactory for all oils normally tested. The pump time should be sufficient for all oil to be pumped through the nozzle and into the upper reservoir, (6) in Fig. A1.1. The valve time should be sufficient for the oil to drain completely from the upper reservoir to the lower reservoir.
10.3 Pour 100 cm3 of the test oil into the lower reservoir through the funnel. Set the cycle counter for 20 cycles. Set a clean 120 cm3 bottle, (10) in Fig. A1.1, under the drain tube of the lower reservoir to receive the sheared sample. Start the pump and run until the 20 cycles have been completed. At the end of the twentieth cycle, both drain valves, (7) and (9) in Fig. A1.1, open automatically and the sample drains into the collection bottle, (10).
10.4 Measure the kinematic viscosity of the sheared oil and a sample of the unsheared oil at 100 °C by Test Method D445.
11. Calculation
11.1 Calculate the percentage loss of viscosity of the sheared oil as follows:
VL = 100 x (Vu - Vs)/Vu
where:
VL = viscosity loss, %,
Vu = kinematic viscosity of unsheared oil at 100 °C, mm2/s, and
Vs = kinematic viscosity of sheared oil at 100 °C, mm2/s.
