【Daily Question】June 25: Starting an axial flow pump (First 80 participants + 2 correct answers earn an additional 3–8 units of wealth)
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This post was last edited by A Le on 2015-6-26 at 10:36. The Mechanical Section has introduced the \"One Question per Day\" feature, which aims to foster an active atmosphere for technical discussions and guide the direction of such exchanges. It also provides users with financial rewards, helping them experience various cool features. 【Daily Question】When starting an axial flow pump, in order to avoid excessive starting current, it is usually done at ( ). A. Start with the valve slightly open. B. Start with the valve partially open. C. Start with the valve fully closed. D. Start with the valve fully open. Answer: D. Unlike centrifugal pumps, axial flow pumps have their maximum shaft power when the valve is closed, and their minimum shaft power when the valve is fully open. Therefore, it should be started with the valve fully open. Requirements and tips for answering questions: Please reply with the answer you believe to be correct. If you provide a detailed explanation or analysis of the question or answer, an additional reward will be given. Extra rewards will be awarded if your answer is correct and your explanation is thorough and accurate. Feel free to answer the questions. Please note: We will close this post after 24 hours, and at that time we will announce the best reply (the best assistance), as well as the answer and explanation. Please do not answer the question repeatedly. As a reward for your effort, if you post a topic in this section within two days that provides a detailed explanation of the knowledge points related to this question, please reply or leave a comment in this post to inform us, and we will have a moderator assign you + Charm. It is not allowed to simply copy and paste; original content is preferred, with at least some organization by the user along with personal insights. After registration, we will rank participants based on the content of their posts: the last-place participant will receive +1 charm, the second-to-last +2 charm, and so on, with the highest score earning +5 charm. Other content: Call for weekly topics and daily questions (prizes for participation) [Mechanical Section] Collection of essential knowledge [Seeking manufacturer sponsorship] (long-term campaign) [Rewards for recommending valuable content] Summary of daily questions and answers related to mechanical equipment for 2015
The shaft power of an axial flow pump is highest at zero flow rate; therefore, the valve on the discharge pipeline must be opened before starting the pump in order to reduce the starting power. D. Start with the valve fully open
When starting an axial flow pump, in order to avoid excessive starting current, it is usually done at (C). A. Start with the valve slightly open B. Start with the valve partially open C. Start with the valve fully closed D. Start with the valve fully open
【Daily Question】When starting an axial flow pump, in order to avoid excessive starting current, it is usually started (C. with the valve fully closed). A. Start with the valve slightly open B. Start with the valve partially open C. Start with the valve fully closed D. Start with the valve fully open
Start with valve C fully closed
When starting an axial flow pump, in order to avoid excessive starting current, it is usually done at (D). A. Start with the valve slightly open B. Start with the valve partially open C. Start with the valve fully closed D. Start with the valve fully open
Choose D. 1. Close the outlet valve before starting the centrifugal pump. When a centrifugal pump is started, there is no water in the pump’s outlet pipeline, so there is no pipeline resistance or head loss. After the pump starts, its head is very low while the flow rate is high; as a result, the motor driving the pump generates a large amount of power (according to the pump’s performance curve), which can easily lead to overloading and damage to the pump’s motor and electrical wiring. Therefore, it is necessary to close the outlet valve at the time of startup to ensure the proper operation of the pump. 2. In an axial flow pump, water is drawn in along the axis of the impeller and discharged in the same direction; hence it is called an axial flow pump. Axial flow pumps and centrifugal pumps operate on different principles; the former primarily uses the thrust generated by the high-speed rotation of the impeller to lift water. The lift force generated by the rotating blades of an axial flow pump on the water allows the water to be pushed from below to above. The blades of an axial flow pump are generally submerged in the water tank containing the water to be pumped. Due to the high-speed rotation of the impeller, the lift force generated by the blades continuously pushes the water upward, causing it to flow out through the outlet pipe. As the impeller keeps rotating, water is continuously pumped to a higher height; imagine that if the valve is closed, it will inevitably lead to pressure buildup. During operation at line frequency, when the outlet valve of a centrifugal pump is fully open, the flow rate increases and the resulting mechanical load increases; whereas during operation at line frequency, when the outlet valve of an axial flow pump is fully open, the flow rate increases but the resulting mechanical load decreases. As the mechanical load increases, the motor’s speed will decrease, resulting in an increased slip rate and a greater rotor current ； Conversely, when the mechanical load decreases, the rotor current will decrease. An increase or decrease in rotor current also causes a corresponding increase or decrease in the current drawn by the stator windings. Therefore, during operation at line frequency: the current is highest when the centrifugal pump’s outlet valve is fully open at startup. The opposite of an axial flow pump
【Daily Question】When starting an axial flow pump, in order to avoid excessive starting current, it is usually done at (D). A. Start with the valve slightly open B. Start with the valve partially open C. Start with the valve fully closed D. Start with the valve fully open
D. Start with the valve fully open
When starting an axial flow pump, the outlet valve must be opened, as the power consumption is lowest at this time; if the valve is closed, it is easy to damage the motor