【Daily Question: Pump Equipment】Weekly Summary May 19, 2019

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Monday (2019.5.13) https://bbs.hcbbs.com/thread-2699170-1-1.html 1. In key coupling, the height of the key matches closely with the depth of the keyway, while there should be a certain gap between the width of the key and the width of the keyway； (Incorrect) 2. Generally, the higher the carbon content in carbon steel materials, the greater the hardness obtained after quenching. (Yes) Tuesday (2019.5.14) https://bbs.hcbbs.com/thread-2700513-1-1.html 1. Fill-in-the-blank question: In O-rings according to standard GB3452.1, if the designation is φ97.5x3.55, then φ97.5 refers to the (C) of the O-ring ； A: Outer diameter B: Middle diameter C: Inner diameter D: Cross-sectional diameter 2. True or False: O-rings used in mechanical seals, due to their small diameter sizes and the large number of available specifications, usually follow the O-ring specifications specified in standard JB7757.2. (Yes) Wednesday (2019.5.15) https://bbs.hcbbs.com/thread-2701997-1-1.html 1. Certain manufacturing processes in equipment manufacturers are considered special processes, which refer to: a) processes whose product quality cannot be verified through subsequent measurements or monitoring; b) processes for which product quality can only be measured through destructive testing or complex and expensive methods, or can only be monitored indirectly; c) processes in which defective quality characteristics become apparent only after the product is used or delivered. Such as welding, heat treatment, painting, casting, and other processes (for) ； 2. The calibration and verification of instruments are two different names for the same process (incorrect). Thursday (2019.5.16) https://bbs.hcbbs.com/thread-2702808-1-1.html 1. Among the non-destructive testing methods, PT stands for magnetic particle inspection (incorrect – PT refers to penetrant testing; MT is the term for magnetic particle inspection) ； 2. During the quality supervision and manufacturing process, there are numerous control points; where W denotes a notification and witnessing point, H denotes a point where work must be halted for inspection, and R denotes a document review point (correct). Friday (2019.5.17) https://bbs.hcbbs.com/thread-2703883-1-1.html 1. At standard atmospheric pressure, water vaporizes at 100°C; it can therefore be inferred that in a vacuum environment, water must vaporize at 0°C (Incorrect — the conclusion is correct, but the causal relationship is wrong) ； 2. If the fit between the pump shaft and the coupling is loose (allowing movement along the shaft), a key with a tighter fit should be used to secure the coupling and prevent such movement (Incorrect – the coupling or the shaft should be replaced). Saturday (2019.5.18) https://bbs.hcbbs.com/thread-2705440-1-1.html Multiple-choice question: Among the following phenomena and characteristics, which ones are common in double-suction centrifugal pumps (BB1)? (B C) A. Rolling bearings are prone to damage. B. The pump’s net positive suction head requirement (NPSHr) is high. C. The pump vibrates excessively due to pipeline vibrations. D. The rotation speed is 2950 RPM. Wishing everyone a pleasant weekend!