A method for testing the flammability of sprays of hydraulic fluid

A method for testing the flammability hazards of hydraulic fluids in the form of spray escapes, is described. The method utilizes sprays, produced by a twin-fluid atomizer, which are ignited at their roots by the carefully controlled input of heat from a gas flame. This heat input is sufficient to provide complete combustion of highly flammable fluids, such as mineral oils, but increasingly incomplete combustion for increasingly less flammable fluids. Measurements of exhaust gas temperature, flame length and particulate emissions are made to derive three separate hazard rankings of fluids. The same test may be extended to rank fluids using other parameters, such as luminosity and exhaust toxicity. The exhaust gas temperature, when suitably normalized, provides the basic hazard ranking parameter, the ‘ignitability’, which provides a measure of the ease of igniting and stabilizing a spray flame of the fluid. A wide range of fluids has been investigated by using the new testing method and the resulting rankings are consistent with qualitative expectations. The technique provides a continuous ranking scale which gives a clear and repetitive means of comparing different fluids. The flammability testing apparatus incorporates careful control and measurement of all flow rates and a compact combustion chamber, with a co-flowing airflow around the spray which removes problems due to a poorly controlled environment which have occurred in earlier tests.