The ignition of hydrocarbon-based oil films by the impact of high-pressure oxygen has been studied as part of an evaluation of cleanliness requirements for oxygen systems. Stainless steel lines contaminated on the inside surface with known quantities of oil were closed at one end, attached to a high-pressure (52 MPa) oxygen system, and pressurized by opening a high-speed valve. Ignition of the oil films was detected by a photocell attached to the closed end of the line.
The results show that the frequency of ignition increased both with the concentration of oil on the inside surface of the stainless steel lines and with the pressure of the impacting oxygen. The experiments were repeated to obtain the probability of ignition under different conditions. The data are fitted to a statistical model and to an empirical equation that give the probability of ignition as a function of concentration and pressure. A comparison is made with literature studies and the results are discussed in light of the cleanliness levels required in oxygen systems.