【Daily Question: Pump Equipment】Weekly Summary 2019.2.3

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bg2.png Monday (2019.1.28) https://bbs.hcbbs.com/thread-2277093-1-1.html 1. Common three-phase squirrel-cage asynchronous motors can be used as variable-frequency motors (False). 2. Metal corrosion is a chemical reaction process (True). Tuesday (2019.1.29) https://bbs.hcbbs.com/thread-2278851-1-1.html 1. Control valves can allow a small amount of internal leakage (True). 2. An increase in the back pressure at the outlet of a centrifugal pump will necessarily lead to an increase in shaft power (False). Wednesday (2019.1.30) https://bbs.hcbbs.com/thread-2279752-1-1.html 1. Jet pumps do not belong to either centrifugal pumps or positive-displacement pumps (True). 2. The “hump” in the performance curve of a centrifugal pump is caused by factors related to the pump itself as well as by operating conditions (False). Thursday (2019.1.31) https://bbs.hcbbs.com/thread-2280990-1-1.html 1. In the standard “GB/T 29531-2013 Methods for Measuring and Evaluating Vibration in Pumps”, the basis for classifying the vibration level of a pump is the pump’s center height and rotational speed (True). 2. The higher the NPSH ratio of a centrifugal pump, the lower its NPSH value, and thus the stronger its resistance to cavitation (True). Friday (2019.2.1) https://bbs.hcbbs.com/thread-2282116-1-1.html 1. Roller bearings of the same size have a higher maximum rotational speed and can handle greater loads than ball bearings (False). 2. In an open system, the same centrifugal pump is less likely to experience cavitation when used at low altitudes compared to high altitudes. (Yes) Saturday (2019.2.2) https://bbs.hcbbs.com/thread-2282632-1-1.html 1. Excessive vibration in magnetic pumps may be caused by an inadequate net positive suction head. (Yes) 2. During vibration analysis, the horizontal axis in the spectrum graph represents the rotational speed, while the vertical axis represents the amplitude. (Mistake) One question per day – the last post before Chinese New Year. Happy Chinese New Year!