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Monday (2019.5.27) https://bbs.hcbbs.com/thread-2713282-1-1.html 1. Just like the starting current of a motor, the torque generated when a pump starts is about 7 times that during normal operation (Incorrect)； 2. The function of the vent valve (breather valve) at the top of the lubricating oil bearing housing is to balance the pressure difference between the inside and outside caused by temperature rise (correct). Tuesday (2019.5.28) https://bbs.hcbbs.com/thread-2715067-1-1.html: For pipeline transportation of a medium, the required average flow velocity is between 2.5 and 5.5 m/s, the flow rate is 300 tons per hour, and the specific gravity of the medium is 0.9. What are the available standard pipe diameters for selection (CD)? ； A 100mm B 125mm C 150mm D 200mm E 250mm Wednesday (2019.5.29) https://bbs.hcbbs.com/thread-2716017-1-1.html A centrifugal pump has a rated flow rate of 75 m3/h, a head of 146 m at that flow rate, an efficiency of 62.5% at the rated flow rate, and a rated rotational speed of 2950 rpm. The specific gravity of the fluid is 1.15. The maximum flow rate under operating conditions is 88 m3/h, with a head of 137 m at that flow rate and an efficiency of 65% at that flow rate. The shaft power at the rated flow rate is therefore (75*146*1.15/(3.6*10^2*0.625)) = 54.87 kW. The motor power required for this pump is (88*137*1.15/(3.6*10^2*0.65)) = 58.1 kW; hence, a 75 kW motor should be used. Thursday (2019.5.30) https://bbs.hcbbs.com/thread-2716911-1-1.html 1. The vibration of the pump connection pipelines is of low frequency, and it is commonly measured and evaluated using the amplitude in millimeters ； 2. It is normal for mechanical seals to exhibit excessive leakage in the initial stages of use, as a running-in period is required; once this period is over, the leakage will be within normal limits. (Mistake) Friday (2019.5.31) https://bbs.hcbbs.com/thread-2717697-1-1.html 1. Judgment: If the temperature value displayed by the PT100 thermoresistor fluctuates significantly in an instant, it indicates that the measured temperature is unstable and experiencing noticeable variations (This is incorrect – it suggests a problem with the instrument itself, issues with its installation, or interference). 2. Fill in the blank: When a pressure-bearing component is subjected to a hydrostatic test, if the pressure starts to drop continuously after pressure application, and after some time the pressure stabilizes without any leaks being detected in either the testing machine or the pressure-bearing component, while the temperature remains constant throughout, this indicates that (there is some degree of deformation of the pressure-bearing component under pressure). Saturday (2019.6.1) https://bbs.hcbbs.com/thread-2718383-1-1.html 1. Centrifugal pumps should preferably operate within a flow rate range that is equal in magnitude to both the design flow rate and its negative value. (Incorrect) 2. The size of the device’s net positive suction head depends on the pump inlet pressure, the pump’s own net positive suction head, and the operating temperature. (Mistake) Have a great weekend! ! !