Thread Content
Monday (2019.01.07) https://bbs.hcbbs.com/thread-2252015-1-1.html 1. As the temperature drops, the specific gravity of water increases continuously before it freezes (False). 2. The elastic elements (or functional structures) that keep the frictioning surfaces in contact are essential components of all types of mechanical seals (True). Tuesday (2019.01.08) https://bbs.hcbbs.com/thread-2253112-1-1.html 1. Calculating the critical speed of a centrifugal pump is done to avoid resonance (True). 2. For all mechanical seals (including dry gas seals), the lower the linear velocity of the rotating ring, the better (False). Wednesday (2019.01.09) https://bbs.hcbbs.com/thread-2254449-1-1.html 1. Self-priming pumps are divided into external mixing type and internal mixing type; in external mixing self-priming pumps, the fluid returns to the outer diameter of the impeller where gas and liquid mix at the impeller’s outlet, while in internal mixing type, the fluid returns to the inlet of the impeller where gas and liquid mix there. (Yes) 2. For pipelines used for long-distance transportation, the frictional losses along the pipeline represent the main type of losses; whereas for pipelines used for short-distance transportation, the local losses caused by fittings and auxiliary equipment are the primary issue. (Yes) Thursday (2019.01.10) https://bbs.hcbbs.com/thread-2255874-1-1.html 1. In the pump manufacturing process, processes such as painting, welding, casting, and heat treatment are considered special processes within the quality management system, and therefore require strict control. (Yes) 2. The smaller the mesh size of the filter at the pump inlet, the greater the pressure drop as the fluid passes through the filter, which increases the likelihood of cavitation in the pump. (Wrong) Friday (2019.01.11) https://bbs.hcbbs.com/thread-2257224-1-1.html 1. The higher the motor’s slip rate, the greater the load on the motor. (Yes) 2. High-power motors are designed to operate at high voltages in order to reduce the starting and operating currents. (Yes) Saturday (2019.01.12) https://bbs.hcbbs.com/thread-2258703-1-1.html 1. The shafts of multi-stage centrifugal pumps are usually slender, and the keyways on these shafts that correspond to the various impellers are often arranged alternately at 180-degree intervals. The main reason for this is to ensure the dynamic balance accuracy of the rotor system. (Incorrect) 2. Under normal circumstances, the efficiency of positive displacement pumps is generally higher than that of centrifugal vane pumps. Have a good weekend