The maintenance factors (m values) and yield stresses (y values) of four gasket materials at four thicknesses each were determined under water pressures of 2.06 MPa and 0.014 MPa, respectively. The gaskets examined were made of PTFE, graphite, Technograph (trade name), and asbestos, each at thicknesses of 1.0, 1.5, 2.0, and 3.0 mm. The m values of asbestos gaskets decreased from 8.32 to 1.73 as thickness was increased, but values for the non-asbestos materials showed no regular change with thickness. The mean m values for PTFE, graphite, and Technograph gaskets were 0.81, 2.12, and 3.01, respectively. The performance of the non-asbestos gaskets was better than that of asbestos gaskets except 1.73 for the 3.0-mm thickness. The y values were much smaller than the m values, e.g. 2.06 MPa for the 1.0-mm thick asbestos gasket under N2 gas, and showed no variation with thickness. The mean y values for PTFE, graphite, Technograph, and asbestos gaskets were 0.08. 0.16, 0.36, and 0.34. It is not realistic to use these values as the minimum effective seating stress, replacing design stress for these gaskets on piping. The nonasbestos sheet gaskets can be used in place of asbestos gaskets at normal temperatures.
Cross sections of silicon and nitrile sheet rubbers were increased to 1.06 and 1.32 times, respectively, by exposure to bio-diesel fuel (BDF) for 112 days. Tensile strength for nitrile sheet rubber was reduced by 41%, and that for silicon sheet rubber was reduced by 12%. These results indicate that aging of nitrile sheet rubber was more rapid than that of silicon sheet rubber in response to exposure to BDF, although the values for reduced tensile strength were around 7 MPa for both of them. No obvious aging on the surface of aluminum alloy was observed in the scanning electron micrographs.
Engine troubles at sea have serious impacts on ship navigation. Serious engine troubles such as damaged piston rings and abnormally worn cylinder liners have even been imputed to problems with marine fuel. This paper proposes a method to test single droplets of marine fuel in order to prevent fuel-related troubles. In this test, a droplet of constant volume suspended from the tip of a quartz stick is combusted in high-temperature air. The marine fuel oil is evaluated based on the length of the burning time and amount of soot. A device to quantify the marine fuel oil and a flame detector were designed to simplify measurement. The standard for the evaluation is shown as follows: 1) Marine fuels that have caused engine problems burn longer than marine fuel oils that have not caused problems. 2) When marine fuels that have caused engine problems are combusted, large quantities of soot adhere to the quartz stick. Our results indicate that this method can be effectively used to identify marine fuels that cause engine problems.