【Daily Question: Pump Equipment】Weekly Summary 2018.12.16

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This post was last edited by 3983596_FPPZ on 2019-1-19 at 09:44. Monday (2018.12.10): https://bbs.hcbbs.com/thread-2194393-1-1.html (Multiple-choice question) It is known that a centrifugal pump is used to transport high-concentration methanol solution at room temperature. The specific gravity of methanol is 0.8, the pump’s flow rate is 50 m3/h, the head is 80 m, the inlet pressure is 2 kgf/cm2, the rotational speed is 2900 r/min, and the motor power is 22 KW. Which of the following outlet pressures is closest to the actual value? (B) A 1.0 MPa B 0.84 MPa C 0.64 MPa D 2.64 MPa E 10 kgf/cm2 F 1.2 MPa. Tuesday (2018.12.11): https://bbs.hcbbs.com/thread-2199654-1-1.html (Multiple-choice question) A centrifugal pump is used to transport clean water in a coastal area. The temperature of the water is 90°C (the saturated vapor pressure of water at 90°C is 70 KPa, and its specific gravity is 0.965). The absolute inlet pressure is 0.08 MPa, and the NPSHR of the pump at its rated flow rate is 3.0 m. Will cavitation occur when this pump operates at its rated point after it is started? (A) A will experience cavitation, and the pump cannot be used. B: Critical cavitation; the pump cannot continue to operate. C: No cavitation will occur, and the pump operates normally. D: Uncertain. Wednesday (2018.12.12) https://bbs.hcbbs.com/thread-2207623-1-1.html (Multiple-choice question) In a double-cylinder, four-acting reciprocating pump, if the assembler fails to install one of the pump valves, then, ignoring the volume of the piston rod, the theoretical flow rate of the pump will (C) A: Not decrease. B: Decrease by 1/2. C: Decrease by 1/4. D: Decrease by 1/8. E: Be zero. Thursday (2018.12.13) https://bbs.hcbbs.com/thread-2211989-1-1.html (Multiple-choice question) In a centrifugal pump, as the viscosity of the fluid being pumped increases, then (ACDF) A: The head decreases. B: The net positive suction head decreases. C: The outlet pressure decreases. D: The efficiency decreases. E: The shaft power decreases. F: The shaft power increases. Friday (2018.12.14) https://bbs.hcbbs.com/thread-2213494-1-1.html (True/False questions) 1. In a centrifugal pump driven by a non-variable-frequency motor, the flow rate is generally controlled by regulating the valve in the pump’s outlet pipeline. (True) 2. For ZA series chemical process pumps, the first step in shutting down the pump properly is to cut off the power supply to the motor. (False) Saturday (2018.12.15) https://bbs.hcbbs.com/thread-2214885-1-1.html (True/False questions) 1. Gradual blockage of the filter screen at the inlet of a centrifugal pump, as well as wear and damage to the sealing rings, can cause the motor to operate under light load or overload conditions, respectively. (True) 2. Cavitation in a pump always occurs first at the inlet blades of the first impeller stage. (True)