China Drying Network News Recently, the European Food Safety Authority (EFSA) announced that at present, under the conditions of using low concentrations of active ingredients, nicotine insecticides such as imidacloprid and thiamethoxam have no sufficient data on the survival of bee populations. Support, need to reset the toxicity criteria. EFSA requires professional committees to carry out in-depth review of products such as canidin, thiamethoxam, imidacloprid, acetamiprid, and thiacloprid. The investigation report is expected to be released in December.
EFSA is based on research reports published by two research groups in France and Britain in March this year. The study data showed that the residual levels of nicotine pesticides in nectar were significantly lower than those approved by the institutions, while the bee's lethal dose during indoor testing was greater than under actual conditions.
The research reports were based on the effects of imidacloprid and thiamethoxam on bees. These pesticides can indirectly interrupt the foraging activities of bee populations and produce certain toxic effects on the population. The results of this study prompted some EU member states to call for a re-evaluation of neonicotinoid insecticides. At the same time, the European Union also requires EFSA to strengthen the influence of nicotinic insecticides on the survival of bee populations to determine whether they are used through seed treatments. In addition to these two studies, EFSA also reviewed a German study that showed that imidacloprid and clothianidin have an impact on the survival of honeybee populations.
EFSA stated that in the determination of nectar residues, three indicators of neonicotinoid insecticide exceeded the maximum residue level specified. Tests have shown that exposure to simulated test methods may have a greater impact than bees in reality. Therefore, when formulating relevant standards, different exposure levels must be considered to ensure that the test results are close to the actual situation.
Globe valve, also known as cut-off valve, is a mandatory sealing valve, so when the valve is closed, pressure must be applied to the valve disc to force the sealing surface not to leak. When the medium enters the valve from under the valve disc, the resistance that the operating force needs to overcome is the friction force between the valve stem and the packing and the thrust generated by the pressure of the medium. The force to close the valve is greater than the force to open the valve, so the valve stem The diameter of the valve should be large, otherwise the failure of the top of the valve stem will occur. According to the connection method, it is divided into three types: flange connection, thread connection and welding connection. After the appearance of the self-sealing valve, the medium flow direction of the globe valve is changed from the top of the valve disc into the valve cavity. At this time, under the action of the medium pressure, the force to close the valve is small, but the force to open the valve is large, and the diameter of the valve stem can be adjusted accordingly. decrease. At the same time, under the action of the medium, this form of valve is also tighter. my country's valve "Three Chemicals" once stipulated that the flow direction of the globe valve should be from top to bottom. When the globe valve is opened, the opening height of the valve disc is 25% to 30% of the nominal diameter. The flow rate has reached the maximum, indicating that the valve has reached the fully open position. Therefore, the fully open position of the globe valve should be determined by the stroke of the valve disc.
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