Flammability of emulsions on hot surfaces

Abstract

Purpose – The purpose of this paper is to establish the influence of oil concentration in oil-in-water emulsions on their flammability on hot surfaces and on their viscosity. The interest in fire test systematization is obviously developing due to many grades and applications of fluids and new design solutions asking for higher parameters in exploitation, including pressure and temperature. Higher temperature and pressure have a synergic effect on fire risk; thus, a special attention has to be given to selecting fluids based on fire tests. Design/methodology/approach – This test simulates a hazardous event when a fluid drops on a hot surface: 10 ml of fluid is dropped during 40-60 seconds on a manifold kept at a constant temperature, from a distance of 300 ± 5 mm above the surface. Tests were done under the procedure of SR EN ISO 20823:2004, with an original equipment. The apparent viscosity of the tested fluids was determined using a rheometer Rheotest 2. The tests were done for the fully mineral oil (Prista MHE-40) and for emulsions with different oil volume in water: 5, 10, 20, 30, 40, 50, 60, 70, 80 and 90 per cent, respectively. Findings – The mineral oil MHE 40 Prista does not burn repeatedly for manifold temperature lower than 440°C, but it burns at 450°C on the clean surface and at 425°C on dirty surface, as obtained after testing the same oil, but at a temperature for which the oil burns. The emulsions do not burn even at 90 per cent oil in water, but the apparent viscosity of the emulsion is too high and unstable, above 20-30 per cent (volume) oil in water. No evident relationship was found between the apparent viscosity of the emulsions and their behavior on hot surface. Research limitations/implications – The hydraulic fluids were ranked, taking into account the flammability characteristics determined with the help of this test. Practical implications – This paper aims to reduce the risk of fire in hazardous environments using fire-resistant fluids. Social implications – Testing hydraulic fluids under the procedure of SR EN ISO 20823:2004 is required by European and national regulations to avoid large-scale accidents produced by the ignition of hydraulic fluids. Originality/value – As far as the authors have known, the test procedure was only used for establishing whether a certain fluid passes or does not pass this test. The authors did not find any references for establishing the influence of oil concentration on the flammability characteristics. Also, the equipment has an original design, allowing for a good repeatability and a high protection of the operator.