【Daily Question: Pump Equipment】Short Answer Question, 3/7/2019
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bk14.jpg Rules for short-answer questions: 1. If the answer is incorrect, +2 wealth will be given for active participation; if the answer is somewhat reasonable but not specific enough, +5 wealth will be given; if the answer is correct, +8 wealth will be given. 2. Rewards for answers are available once per person only. 3. Each reply allows scoring for only one person. 4. The answer and its explanation will be visible after responding. 5. The reward is valid for 48 hours; no reward will be given if the deadline is exceeded. The student has won another award; come by here every day. It’s a municipal drainage centrifugal pump used in coastal areas, designed to draw water from pools at a certain depth. The pool is 4 meters deep, with the suction pipe extending 2.6 meters into the pool. The pump’s inlet is horizontal, and the vertical distance from the center of the inlet to the water surface is 3.5 meters. The water temperature is at normal levels. The pump’s NPSHR is 4.5 meters, and the loss in the suction pipeline at its rated flow rate is 0.3 meters. Will this pump be able to operate properly once it is started after being filled with water? Why? Answer: It can operate properly; at standard atmospheric pressure, water column height – NPSHR – suction pipe losses – safety margin > vertical lift distance: 10.3 – 4.5 – 0.3 – 0.5 = 5 > 3.5
It can operate properly; at standard atmospheric pressure, water column height – NPSHR – suction pipe losses – safety margin > vertical lift distance: 10.3 – 4.5 – 0.3 – 0.5 = 5 > 3.5
Yes. Effective NPSH of the unit = 10.3 – 3.5 – 0.3 – 0.5 = 6 > NPSHR 4.5
It can operate normally, with NPSHa-NPSHr > 0.6 m
It works; 3.5 + 0.3 = 3.8 << 4.5
Answer: It can work normally. 3.5 + 0.3 = 3.8 m, which is less than the NPSHR of 4.5 meters