【Q&A Question 209】2017.07.28
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【Q&A Question 209】July 28, 2017: Why can’t valves be opened and closed quickly? The reference answers will be visible after responding; points are awarded by identifying the key points. (Unless otherwise specified, all questions and answers are based on hydrogenation units.) Operating the valve too quickly for opening or closing can lead to the following negative consequences: for the pump, it causes a sudden change in the discharge volume at the pump’s outlet, as well as sudden fluctuations in the motor current, which disrupts its stable operation and can damage the motor ； For equipment, a sudden increase in pressure within the pipelines and equipment generates excessive force on them, leading to damage to those pipelines and equipment ； For thermal media, sudden increases or decreases in the temperature of pipelines and equipment lead to rapid heating and cooling, generating excessive thermal stress that can easily damage the equipment ； In terms of operation, large fluctuations in medium flow disrupt the operational balance, which in turn affects product quality. Scoring criteria: 2 Wealth points for incorrect attempts; 3–8 points for *incomplete* answers. 10 Wealth points for correct answers, provided with detailed explanations; 15–20 Wealth points if the answer is correct but lacks sufficient details. Please score according to these criteria. Note: If there are edit records after answering, only participants will be given points. For continuous malicious spamming, 2 points will be deducted each time, with no upper limit. Pure numbers, pure emojis, or random letters that have nothing to do with the answer are all considered malicious spamming; points will start to be deducted after three warnings. 2017 Q&A Summary Thread (updates have begun) http://bbs.hcbbs.com/thread-1657793-1-1.html 2017 Daily Question Summary Thread (updates have begun) http://bbs.hcbbs.com/thread-1657794-1-1.html 2016 Q&A Summary Thread (updates completed) http://bbs.hcbbs.com/thread-1597792-1-1.html Petrochemical Sector – “Creative Ideas for Energy Saving” Campaign (Phase 2 is in full swing) http://bbs.hcbbs.com/thread-1666758-1-1.html (Source: Haichuan Chemical Industry Forum Website)
When opening and closing valves, do so slowly, as rapid opening and closing of valves in the pipeline can cause water hammer, resulting in a pressure surge in the section of pipe right next to the valve.
Because rapidly opening and closing valves in the pipeline causes water hammer, a water hammer pressure value is generated in the pipe section right next to the valve.
Operating the valve too quickly for opening or closing can lead to the following negative consequences: ① For the pump, it causes a sudden change in the discharge volume at the pump’s outlet, as well as sudden fluctuations in the motor current, which disrupts its stable operation and can damage the motor. ②It causes a sudden increase in pressure within the pipelines and equipment, exerting excessive force on them and damaging them. ③For thermal media, sudden increases or decreases in the temperature of pipelines and equipment lead to excessive thermal stress during these rapid temperature changes, which can easily damage the equipment.
Operating the valve too quickly for opening or closing can lead to the following negative consequences: ① For the pump, it causes a sudden change in the discharge volume at the pump’s outlet, as well as sudden fluctuations in the motor current, which disrupts its stable operation and can damage the motor. ②It causes a sudden increase in pressure within the pipelines and equipment, exerting excessive force on them and damaging them. ③For thermal media, sudden increases or decreases in the temperature of pipelines and equipment lead to excessive thermal stress during these rapid temperature changes, which can easily damage the equipment.
Because rapidly opening and closing valves in the pipeline causes water hammer, a water hammer pressure value is generated in the pipe section right next to the valve
When opening and closing valves, do so slowly, as rapid opening and closing of valves in the pipeline can cause water hammer, resulting in a pressure surge in the section of pipe right next to the valve.
When opening and closing valves, do so slowly, as rapid opening and closing of valves in the pipeline can cause water hammer, resulting in a pressure surge in the section of pipe right next to the valve. Search: According to calculations, for every 1 m/s change in the flow velocity of the liquid in the pipeline, the pressure generated by the liquid can reach 1 MPa. Moreover, this pressure propagates upstream from the section of the pipeline nearest to the valve at a speed close to the speed of sound (the speed of sound is 1500 m/s in water and 1100 m/s in gasoline). This pressure combines with the original pressures at various points along the pipeline, and this combined pressure can be high enough to cause the pipeline to burst. When the valve is opened and closed slowly and gradually, the rate of change is small over short periods of time, resulting in low initial pressure values. As time passes, the water hammer wave travels upstream and generates a reflected wave that counteracts the initial water hammer pressure, thereby preventing overpressure incidents in the pipeline.
Large pressure differences on both sides of the valve cause equipment damage