Miniaturized Tests for Fire Resistance of Hydraulic Fluids

Abstract

Some of the conventional tests for assessing the fire resistance of hydraulic fluids use relatively large amounts of fluid in relationship to quantities available from exploratory research programs. To alleviate this problem, four miniaturized tests were devised for evaluating fire resistance of aerospace fluids. These were intended to simulate the following normal-size tests: (1) flash point (Cleveland open cup), (2) hot manifold, (3) low pressure spray, and (4) high pressure spray. The microflash apparatus uses a spark plug and a heated aluminum cylinder. Three drops of fluid are applied at each temperature of the test. Results were somewhat higher than for full-scale equipment. Low pressure spray test employs an airless spray gun (rotating disk) with reservoir modified to hold a small volume of fluid. In the high pressure spray apparatus, gas pressure forces fluid from a small orifice in stainless steel tubing, and only 20 ml of fluid is used in each determination. The small-scale hot manifold test uses a 1/2-in. diameter stainless steel heater. These miniaturized tests require a total of 40-ml of fluid, as compared to about 2500 required for the corresponding full-scale tests. The small units are easy to operate, and repeatability is good.