[Q&A Question 241] 2018.09.04
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【Q&A Question 241】September 4, 2018: Briefly describe how to isolate a control valve in case of a failure In coordination with the operator, slightly open the bypass valve, and gradually close the control valve (or the upstream valve), maintaining stable process parameters (pressure, flow rate) downstream of the valve until the control valve is fully closed. Verify that the process parameters (pressure, flow rate) downstream of the valve are consistent with those when the control valve is operating properly. Close the upstream valve first, then the downstream valve, and slightly open the drain valve (vent valve or discharge valve) to vent or discharge fluid until all material in the pipeline has been removed, ensuring no internal leakage between the valves. (Unless otherwise specified, all questions and answers 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
Following the indication of the primary gauge at the site, first close the upstream valve slightly until there is a change in the reading on the primary gauge; at this point, the maximum flow rate of the control valve is already being controlled by the upstream valve. One person slowly opens the bypass valve, while another slowly closes the upstream valve; it is best for the gauge reading to remain stable, until the upstream valve is fully closed at which point the bypass valve is used for control.
Following the indication of the primary gauge at the site, first close the upstream valve slightly until there is a change in the reading on the primary gauge; at this point, the maximum flow rate of the control valve is already being controlled by the upstream valve. One person slowly opens the bypass valve, while another slowly closes the upstream valve; it is best for the gauge reading to remain stable, until the upstream valve is fully closed at which point the bypass valve is used for control.
In coordination with the operator, slightly open the bypass valve, and gradually close the control valve (or the upstream valve), maintaining stable process parameters (pressure, flow rate) downstream of the valve until the control valve is fully closed. Verify that the process parameters (pressure, flow rate) downstream of the valve are consistent with those when the control valve is operating properly. Close the upstream valve first, then the downstream valve, and slightly open the drain valve (vent valve or discharge valve) to vent or discharge fluid until all material in the pipeline has been removed, ensuring no internal leakage between the valves.
In coordination with the operator, slightly open the bypass valve, and gradually close the control valve (or the upstream valve), maintaining stable process parameters (pressure, flow rate) downstream of the valve until the control valve is fully closed. Verify that the process parameters (pressure, flow rate) downstream of the valve are consistent with those when the control valve is operating properly. Close the upstream valve first, then the downstream valve, and slightly open the drain valve (vent valve or discharge valve) to vent or discharge fluid until all material in the pipeline has been removed, ensuring no internal leakage between the valves.
There are several symptoms of a faulty control valve: usually, it gets stuck and remains fixed in one position, unable to be adjusted； Second, it cannot be adjusted after being fully opened ； Third, it cannot be adjusted after being fully turned off ； In case of jamming: The operator inside and outside work together; the external operator first opens the bypass line appropriately, and once the internal operator sees an increase in flow rate, they close the manual valves upstream and downstream of the control valve, then use the bypass line valve to carry out the operations ； In both fully open and fully closed positions, the valve is directly controlled by the auxiliary line to reach the appropriate opening degree, after which the valves upstream and downstream of the control valve are closed.
Following the indication of the primary gauge at the site, first close the upstream valve slightly until there is a change in the reading on the primary gauge; at this point, the maximum flow rate of the control valve is already being controlled by the upstream valve.
In coordination with the internal operator, slightly open the bypass valve and gradually close the control valve
1. When the control valve fails and shuts down, quickly open the bypass valve of the control valve to maintain a stable flow rate in the pipeline. Then, communicate with the operators on site to regulate the flow rate through a bypass line to the level it was at before the control valve failed. After that, close the manual valves before and after the control valve, and use drainage for emptying and replacement until the conditions are satisfactory, after which the valve can be sent for maintenance. 2. When the control valve fails to operate properly, quickly close the upstream valve of the control valve to prevent pressure surges. Then, by gradually closing this upstream valve, slowly open the bypass valve of the control valve (it is best to maintain a stable flow rate). Once the upstream valve of the control valve is fully closed, use the bypass valve to keep the flow rate stable. Finally, close both the upstream and downstream valves of the control valve, vent the system, and proceed with maintenance once the conditions are satisfactory.
Refer to the indication on the primary gauge at the site (or contact the control room), and first close the upstream valve slightly until there is a change in the indication on the primary gauge (or until the downstream parameters remain stable); at this point, the maximum flow rate of the control valve is controlled by the upstream valve. One person slowly opens the bypass valve, while another slowly closes the upstream valve; it is advisable for the gauge reading to remain stable (or for the downstream parameters to stay constant) until the upstream valve is fully closed, at which point the bypass valve is used for control.
Following the indication of the primary gauge at the site, first close the upstream valve slightly until there is a change in the reading on the primary gauge; at this point, the maximum flow rate of the control valve is already being controlled by the upstream valve. One person slowly opens the bypass valve, while another slowly closes the upstream valve; it is best for the gauge reading to remain stable, until the upstream valve is fully closed at which point the bypass valve is used for control.