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Monday (2019.4.22) https://bbs.hcbbs.com/thread-2679773-1-1.html 1. A sealing gasket needs to be placed in the internal threaded hole M22x1.5 of a union fitting, and the outer diameter of this gasket should be approximately (20) mm; 2. Among the four types of positive displacement pumps – gear pumps, diaphragm pumps, piston pumps, and screw pumps – which one generates the greatest pressure difference? (Piston pump). Tuesday (2019.4.23) https://bbs.hcbbs.com/thread-2680756-1-1.html 1. Water is the substance among naturally occurring liquids with the highest specific heat capacity; therefore, it is often used as a cooling and heat transfer medium (correct) ； 2. The viscosity grades of industrial lubricants are ISO viscosity classes; they only indicate the dynamic viscosity of the oil at 40 degrees Celsius, and do not reveal the brand or intended use of the oil. These details must be specified separately when making a purchase (correct) ； Wednesday (2019.4.24) https://bbs.hcbbs.com/thread-2681966-1-1.html 1. Vertical cartridge pumps are often used in applications where the net positive suction head is low; the main reason for this is (B). A. The pump has high efficiency. B. The pump has a low net positive suction head. C. The pump has multiple stages. D. The pump has a high head. 2. Before starting a centrifugal pump with a high head and high power, the on-site operator should keep a distance from all locations except for (C); it is not necessary to avoid that location, in order to prevent any dangers. A. The plane in which the coupling rotates; B. The plane where the seal surface of the pump outlet flange is located; C. The motor start/stop switch; D. The cable connecting the motor. Thursday (2019.4.25) https://bbs.hcbbs.com/thread-2683585-1-1.html 1. In vertical or submersible pumps with separate bearing housings, when calculating the load on the rolling bearings, the weight of the rotor must be taken into account (correct) ； 2. When the medium enters the inlet of the impeller of a centrifugal pump (not an axial flow pump), it exerts an axial force on the impeller, known as dynamic reaction force. However, the AY centrifugal oil pump has an inlet and outlet arranged at the top, so there is no dynamic reaction force (incorrect). Friday (2019.4.26) https://bbs.hcbbs.com/thread-2685340-1-1.html Briefly explain under what circumstances is it necessary to have a backup pump at the pump location when using a pump 1. Key or important pump stations – those whose shutdown would cause significant losses and impacts on production ； 2. Pump locations where the operating conditions vary greatly, as significant fluctuations in the process parameters can easily lead to pump damage ； 3. Process requirements specify pump stations that must operate continuously without interruption ； 4. Maintenance costs or downtime costs are higher than those for pumps with standby pumps ； 5. Pump positions that require a standby pump as explicitly stipulated by standards and specifications. Saturday (April 27, 2019): https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=2686296. To estimate the vibration levels of a centrifugal pump with a rotational speed of 2950 r/min and a center height of 320 mm, it is first necessary to determine the acceptable criteria for such vibration levels. According to the standard GB10889-89 \"Methods for Measuring and Evaluating Vibration in Pumps\", this type of pump should fall into Category (III) as specified in the standard. If its vibration level is to be classified as Class B, then its vibration values should not exceed 4.5 mm/s. Sunday (April 28, 2019): https://bbs.hcbbs.com/thread-2687255-1-1.html. 1. (Multiple choice) Which of the following structures can independently handle the task of balancing the axial forces in a centrifugal pump? (B) A. Balance holes in the impeller; B. Double-suction impeller; C. Balance disc in a multi-stage pump; D. Double-channel pump casing. 2. (True/False) If the vaporization pressure of a liquid at 80°C is 150 KPa, then at that temperature, when the pressure gauge reads 0.1 MPa, the liquid will start to vaporize. (Mistake). Monday (2019.4.29) https://bbs.hcbbs.com/thread-2688213-1-1.html 1. In the rotor part of a magnetic pump, since it is in contact with the medium, rolling bearings cannot be used; only sliding bearings can be employed (correct) ； 2. Due to the symmetrical structure, all gear pumps can operate in the reverse direction (incorrect). Tuesday (April 30, 2019) https://bbs.hcbbs.com/thread-2689592-1-1.html 1. When verifying whether the performance parameters of domestic centrifugal pump equipment meet the required standards, in addition to the provisions specified in the contract agreements, the most commonly used criterion is (GB/T3216-2005/2016) ； 2. All losses are ultimately manifested in the form of (heat generation/temperature rise/thermal energy/heat). Wish all sailors a happy Labor Day! ! A comfortable rest! ! Have fun! !