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Fluidic Control: Pumps and Valves
Published in Frances S. Ligler, Jason S. Kim, The Microflow Cytometer, 2019
Siyang Zheng, Kashan Shaikh, Jun Xie
Check valves have diode-like behavior, allowing flow in only one direction. Most check valves are incorporated at the inlet and outlet of micropumps. The backpressure and pumping rate are negatively affected by the valve leakage. Most check valves are normally closed, passive flap valves. The flap structure can be circular diaphragm,17,21,68 cantilever,23,25,69 or tethered-plate,14,19,70 although non-flap structures like ball-type check valves.71 have been reported. Recently, floating-disk check valves for self-pressure-regulating flow controls were demonstrated with a biocompatible polymer parylene and used in a retinal prosthesis application.72 One design achieved near ideal diode operation with zero forwardcracking pressure and zero reverse leakage. The other design demonstrated a pressure-bandpass check valve with 0-100 mmHg pressure regulation range.
Fugitive emissions of volatile organic compounds from the pharmaceutical industry in China based on leak detection and repair monitoring, atmospheric prediction, and health risk assessment
Published in Journal of Environmental Science and Health, Part A, 2023
Fang Zhao, Yao Peng, Lin Huang, Ziwei Li, Weinan Tu, Biao Wu
After monitoring, the repair of a single flange reduced emissions by 47.5 kg, which was the largest emission reduction among all types of components. The repair of open-ended lines achieved the least reduction, of 3.1 kg per piece. Leaks were not identified in three types of components: agitator (shaft seal), pump (shaft seal), and pressure relief equipment. Therefore, these components were not repaired, as shown in Figure 2b). Flanges were the most repaired components. Despite the differences in the effectiveness of leak repair in different components, they all had good repairability and satisfied the production requirements. Flange leaks mainly because of the loosening of bolts and nuts, wearing of gaskets, or seal failures, which can be solved by tightening the bolts and nuts, replacing gaskets, or re-winding thread seal tape. Valve leakage generally refers to the leakage between the valve stem and gland packing, which can usually be eliminated by properly torquing the nut on the gland or gland bolt.[41–43] The main reason for the leakage of open-ended lines is the loose valve end, which can be solved by installing additional valves, blind plates, or pipe plugs, based on the conditions of the valve end or pipeline. A single component emitted 0.32 kg per year after the modification of the equipment and facilities, and a single pump had the highest emission of 1.42 kg per year. Pump leakage is generally due to seal failure and seal face separation, and sometimes results from lower spring pressure or insufficient fluid pressure. Such faults can be repaired by replacing the seal and static and dynamic O-rings and increasing the pressure ratio.
Importance of early fault diagnosis for marine diesel engines: a case study on efficiency management and environment
Published in Ships and Offshore Structures, 2022
Çağlar Karatuğ, Yasin Arslanoğlu
The abnormalities observed in the indicator diagrams taken from each cylinder of the diesel engine are evaluated as that the combustion does not occur in the normal conditions in the related cylinder. The reasons such as not performing sufficient maintenance operations properly, monitoring the informative indicators such as temperature and pressure deficiently, etc. could cause in this situation. Many conditions could affect combustion efficiency in the main engine. Faulty operations evaluated within the scope of this study: Early injection timing: Combustion that occurs earlier than the crank angle value stated in the timing diagram causes the pressure to reach higher than it should be. This operation mode could be caused by incorrect injector spring adjustment, wrong timing of fuel pump, etc. (Wharton 1991).Late injection timing: The combustion occurs while the piston is in the expansion phase, and therefore power is lost, the temperature of the exhaust gas rises, and the afterburning could emerge. Incorrect injector spring adjustment, poor atomisation, and incorrect specification of fuel could result in late injection timing (Wharton 1991).Worn injector nozzle: To ensure an efficient heat transfer between fuel and air, fuel is injected in an atomised way into the cylinder, but the wear of the injector nozzle could result in poor atomisation. Late timing could be emerged because of poor atomisation.Clogged injector nozzle: It could occur as a result of carbon build-up on the overheated nozzle. In such a case, the amount of fuel injected into the cylinder and the particle diameter of fuel could change, the power value desired to be produced by combustion does not be achieved and a decrease in the exhaust gas temperature of the related cylinder is to be.Exhaust valve leakage: Leakage of exhaust valve could be caused by the poor valve spring pressure, poor valve clearance adjustment, and fractures, cracks, or contamination on surfaces where exhaust valve pressed. Scavenging efficiency of the fresh air in the cylinder and the power generation is decreased.Contaminated scavenging air ports: Deposits that could mix into the scavenging air ports by exhaust gases or turbocharged air, reduce the quality of the air to be sent into the cylinder. It decreases the efficiency of the fresh air and the combustion process.