【Daily Question: Pump Equipment】Weekly Summary 2018.12.23

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This post was last edited by 3983596_FPPZ on 2019-1-19 09:44. Monday (2018.12.17): https://bbs.hcbbs.com/thread-2216670-1-1.html 1. Steel grade 45# has a higher carbon content than steel grade 25#, so it possesses better weldability. (Mistake) 2. ZG230-450 is a cast carbon steel material, meaning that its tensile strength ranges from 230 MPa to 450 MPa. (Mistake) Tuesday (2018.12.18) https://bbs.hcbbs.com/thread-2217899-1-1.html 1. If the outlet valve of the centrifugal pump is gradually opened from fully closed to its maximum position, the following conditions may occur: flow rate can be zero, efficiency can be zero, and the net positive suction head can be zero. (Mistake) 2. Based on the variation pattern of the pump’s flow-rate vs. shaft power curve, it can be determined whether the pump should be started with the valve closed or open. (Correct) Wednesday (2018.12.19) https://bbs.hcbbs.com/thread-2220199-1-1.html 1. The net positive suction head value for all centrifugal pumps is less than 10.3 meters. (Mistake) 2. Increasing the flow velocity of the liquid at the inlet of the centrifugal pump can reduce the tendency of the pump to experience cavitation. (Mistake) Thursday (2018.12.20): https://bbs.hcbbs.com/thread-2221393-1-1.html 1. The main difference in the chemical composition of 304 and 316L metals is that, at the same carbon content, their levels of other chemical elements such as Cr and Ni vary. (Mistake) 2. For impellers with a large outlet diameter, it is necessary to cut them at an angle along the outer diameter; this is done so that the impeller can still maintain axial force balance and good dynamic balance after cutting. (Mistake) Friday (2018.12.21): https://bbs.hcbbs.com/thread-2223085-1-1.html 1. The factory testing items for ordinary centrifugal pumps include three aspects: performance tests, vibration tests, and temperature rise tests. (Mistake) 2. The operating pressure of a pump is limited by the hydrostatic test pressure of its pump casing; the maximum operating pressure shall not exceed this value. (Mistake) Saturday (2018.12.22): https://bbs.hcbbs.com/thread-2224434-1-1.html 1. For the motor used in conjunction with a pump, the actual electricity consumption = rated power of the motor x operating time. (Mistake) 2. For a given pump and fixed operating conditions, using a motor with a lower rated power will definitely result in less energy consumption. (Mistake)