[Q&A Question 163] 2018.06.12
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【Q&A Question 163】June 12, 2018: Briefly explain why a \"reverse valve\" is generally used for regulating the temperature at the furnace outlet. For safety reasons, in case of a sudden interruption in the air supply to the valve, an air-actuated valve is used; it operates in the \"forward\" direction, so the control element also acts in the \"forward\" direction, and the transmitter as well. Therefore, the regulation must occur in the \"reverse\" direction, so that when the furnace temperature rises, the output of the control system decreases, thereby causing the valve to close and the furnace temperature to drop. (Unless otherwise specified, all Q&A questions are based on hydrogenation units.) ) Correct: 3 wealth, Incorrect: 1 wealth ； Mass posting of posts – rated based on the lowest score ； Replies that are unrelated to the answer are considered spam and will be deleted immediately. For management purposes, if you need to view content from a few days ago, please go to https://bbs.hcbbs.com/home.php?mod=space&uid=3862647&do=thread&view=me&from=space through the summary post below. The APP short-video skill competition has started! https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1951670
Wind opening valve? Shut down in the event of an accident; the valve closes when ventilation is stopped to ensure safety
Air shut-off valve: opens when air supply is stopped to prevent coking of the furnace tubes
For safety in the event of a sudden interruption of the air supply to the valve, a normally open valve is used. It operates in the “positive” direction; therefore, the control element also acts in the “positive” direction, and the transmitter functions in the “positive” direction as well. As a result, the control action must be in the “negative” direction in order to reduce the output when the furnace temperature rises, thereby closing the valve and lowering the furnace temperature.
For safety in the event of a sudden interruption of the air supply to the valve, a normally open valve is used. It operates in the “positive” direction; therefore, the control element also acts in the “positive” direction, and the transmitter functions in the “positive” direction as well. As a result, the control action must be in the “negative” direction in order to reduce the output when the furnace temperature rises, thereby causing the valve to close and the furnace temperature to drop.
For safety in the event of a sudden interruption of the air supply to the valve, a normally open valve is used. It operates in the “positive” direction; therefore, the control element also acts in the “positive” direction, and the transmitter functions in the “positive” direction as well. As a result, the control action must be in the “opposite” direction in order to reduce the output when the furnace temperature rises, thereby closing the valve and lowering the furnace temperature.
For safety in the event of a sudden interruption of the air supply to the valve, a normally open valve is used. It operates in the “positive” direction; therefore, the control element also acts in the “positive” direction, and the transmitter functions in the “positive” direction as well. As a result, the control action must be in the “negative” direction in order to reduce the output when the furnace temperature rises, thereby closing the valve and lowering the furnace temperature.
For safety in the event of a sudden interruption of the air supply to the valve, a normally open valve is used. It operates in the “positive” direction; therefore, the control element also acts in the “positive” direction, and the transmitter functions in the “positive” direction as well. As a result, the control action must be in the “negative” direction in order to reduce the output when the furnace temperature rises, thereby closing the valve and lowering the furnace temperature.
Answer: For safety purposes, in the event of a sudden interruption of the air supply to the valve, a normally open valve is used. It operates in the “positive” direction; therefore, the control element also acts in the “positive” direction, and the transmitter does as well. As a result, the control action must be in the “negative” direction, so that when the furnace temperature rises, the output of the control system decreases, which in turn causes the valve to close and the furnace temperature to drop.
For safety in the event of a sudden interruption of the air supply to the valve, a normally open valve is used. It operates in the “positive” direction; therefore, the control element also acts in the “positive” direction, and the transmitter functions in the “positive” direction as well. As a result, the control action must be in the “negative” direction in order to reduce the output when the furnace temperature rises, thereby closing the valve and lowering the furnace temperature.
Air shut-off valve: opens when air supply is stopped to prevent coking of the furnace tubes