diaphragms and hnbr seals
diaphragm hnbr seals
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Dia•Com is a leading international provider of innovative, cost-effective molded diaphragm solutions critical to the operation of essential systems and equipment in industrial, automotive, aerospace, medical instrumentation, and food and water processing applications. The company's reputation for excellence is based on superior quality in the design, manufacture and application of its high-performance, state-of-the-art, fabric-reinforced and homogeneous elastomeric diaphragm seals.

Gas-to-liquid (GTL) technology has been used for many years to synthesize hydrocarbons from natural gas. Recently, interest has grown in the production of GTL fuels and their emission reduction benefits. Several companies produce or have produced GTL fuels, including Shell, Sasol, ExxonMobil, and others.1 Many studies have examined the impact of GTL fuel on exhaust emissions from light- and heavy-duty vehicles and engines (summarized in Reference 2). In a majority of cases, GTL fuel produced a reduction in regulated emissions (hydrocarbons [HC], oxides of nitrogen [NOx], carbon monoxide [CO], particulate matter [PM]) compared to conventional diesel fuel. Much of the emission data reported have come from short-term studies, where the engine/vehicle has been switched to GTL fuel from conventional diesel fuel for the purposes of collecting emission test results. Upon concluding the tests, the engine/vehicle is then switched back to conventional diesel fuel. Thus, the long-term effect of GTL fuel on engine systems has not been adequately quantified. FUEL PROPERTY TESTING Previous studies of GTL diesel fuel do not always list complete fuel properties or test methods.2 The fuel used in this study was tested to determine physical and chemical properties. In addition, researchers performed elastomer compatibility testing to characterize the impact of GTL fuel on fuel system elastomers. FUEL PRODUCTION TECHNOLOGY – Shell Global Solutions (US) Inc. provided the fuel that was used for fuel property and emission testing, and on-road use. The SMDS (Shell Middle Distillate Synthesis) process is well documented, so only a brief description is offered here.3 The process is illustrated in Figure 1. The process was developed at Shell Research & Technology Centre Amsterdam and is comprised essentially of three stages: Manufacture of synthesis gas (hydrogen + carbon monoxide–with a H2:CO ratio of approximately two) from natural gas by non-catalytic auto-thermal partial oxidation using, for example, the Shell Gasification Process. Wax synthesis from CO + H2 by Heavy Paraffin Synthesis (HPS), followed by flash distillation to separate light ends (e.g., liquefied petroleum gas). Cracking of wax to distillates by Heavy Paraffin Conversion (HPC), where the boiling range and quality of the products can be adjusted to produce either kerosene or atmospheric gas oil (diesel). A recent modification to this process, designated as SMDS-2 offers an improved HPS (Heavy Paraffin Synthesis) catalyst, which will enable the manufacturers to increase production capacity considerably. In addition, adjusting the severity in the hydrocracking/isomerization (HPC) stage allows control of the n- to iso- paraffin ratio in the final product. Figure 1. Schematic illustration of Shell SMDS process. OO 2 2 Natural Gas CO + 2H 2 SSyynnththeessisis H 2 O – CH 2 – HHyyddrrooggeennaattioionn Naptha Kerosene Gasoil HHyyddrrooccrraacckkiningg ASU SGP HPS HPC CH4 Lube oil feedstock Syngas manufacture Syngas manufacture Solvents Waxes FUEL PROPERTY TEST RESULTS - The fuel was tested for a wide range of properties, such as composition, energy content, cold flow properties, and elastomer compatibility. All fuel property testing was performed at Southwest Research Institute in San Antonio, TX. Except for elastomer compatibility, which will be discussed separately, the test results are compiled in Table 1. Where applicable, the ASTM D975 specification is also listed. The fuel composition was tested through elemental testing and hydrocarbon determination. GTL fuel is composed of carbon and hydrogen. The fuel H/C ratio is about 2.1, about 16% greater than conventional diesel fuel. The high H/C ratio is due to the near zero aromatic content of the GTL diesel fuel.4 As with most GTL fuels, the Shell GTL has near zero sulfur content. The very low aromatic content and/or the high H/C ratio of diesel fuel have been shown to reduce NOx and PM emissions in previous studies.5,6,7 Thus, testing with GTL fuel is likely to result in reductions in NOx and PM emissions. Fuel sulfur reductions also result in PM emission reductions, though with diminishing returns as sulfur content becomes very low.6 In newer technology engines, the near zero sulfur content of GTL fuel may prove more beneficial by enabling sulfur sensitive emission control devices. GTL fuels have reduced densities compared to conventional diesel fuels,2 which have been shown to reduce the PM emission in older technology engines.6,7 Low density fuels, such as GTL fuel, may alter the fuel mass flow rates.7 Previous GTL fuel studies have not noted adverse effects on engine operation as a result of the lower fuel density.9,10,11 The cetane number of GTL fuels is most often reported as >74, much higher than conventional diesel fuels.12 GTL fuel is composed almost wholly of paraffins. Nparaffins are known to have very high cetane numbers, while iso-paraffins have lower cetane numbers.13 Increasing cetane number has been linked to a decrease or no change in NOx emissions. The effect appears to be depend on engine model year, with a less prominent effect on newer technology engines.5,6,7


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